GB2136427A

GB2136427A - Herbicidal N-pyridylpyrazole Derivatives

Info

Publication number: GB2136427A
Application number: GB08405980A
Authority: GB
Inventors: Leslie Roy Hatton; Edgar William Parnell; David Alan Roberts
Original assignee: May and Baker Ltd
Current assignee: May and Baker Ltd
Priority date: 1983-03-09
Filing date: 1984-03-07
Publication date: 1984-09-19
Also published as: GB8405980D0; GB2136427B

Abstract

N-Pyridylpyrazole derivatives of the general formula:- <IMAGE> wherein R<1> is (i), H, (ii) R<4>C(=O)- (wherein R<4> is H, C1-7alkyl or C1-4alkoxy optionally substituted by C1-4alkoxy, C2-8alkoxycarbonyl or halogen, or C3-4alkenyloxy, or R<4> is C3-6cycloalkyl optionally substituted by methyl or ethyl or R<4> is phenoxy (iii) R<5> wherein R<5> is C1-8alkyl or C2-8alkenyl or alkynyl optionally substituted by CN, OH, C1-6alkoxy, CO2H, 2-9alkoxycarbonyl, aminocarbonyl (optionally mono- or di-substituted by C1-8alkyl or C2-8alkenyl or alkynyl), C2-9alkoxyaminocarbonyl C2-9alkanesulphanamidocarbonyl, -C(=Het) [wherein Het is a N-containing saturated heterocyclic group having 3 to 7 ring atoms including up to 2 additional heteroatoms (O, N or S)] or halogen, or R<5> is C3-6cycloalkyl optionally substituted by one or more C1-4alkyls, R<2> is (iv) H when R<1> is H, (v) H or R<4> C(=O)- when R<1> is R<4>C(=O)-, (vi) H or R<5> when R<1> is R<5> or R<1> and R<2> together represent -CO-(CR<a>R<b>)m-CO- wherein R<a> and R<b> are H or C1-4alkyl and m is 2 or 3, or R<1>R<2>N- represents a group of the general formula:- <IMAGE> (wherein R<c>-R<h> are H or C1-6alkyl and n is 0, 1 or 2), or R<1> is C1-4alkylthio and R<2> is H, or R<1>R<2>N- represents R<p)<R<q>)C=N- where R<p> is C1-4alkoxy or NH2 optionally mono- or di-substituted by C1-4alkyl and R<q> is H or C1-4 alkyl, and R<3> is 3-chloro-5-trifluoromethylpyrid-2-yl and when appropriate salts with agriculturally acceptable bases, possess herbicidal properties. Compounds of general formula I wherein R<1>R<2>N- represents an open- chain alkenylcarbonylamino group and compounds of the general formula (NC)2C=CHNHNHR<3>, which possess herbicidal properties similar to the compounds of general formula I, are also described.

Description

SPECIFICATION N-Pyridylpyrazole Derivatives Useful as Herbicides This invention relates to N-pyridylpyrazole derivatives, compositions containing them and their use as herbicides.

The present invention provides new N-pyridylpyrazole derivatives of the general formula I herein depicted wherein R' represents (i) a hydrogen atom, (ii) an R4C(=0)-- group, wherein R4 represents a hydrogen atom, a straight- or branched-chain alkyl group containing from 1 to 7 carbon atoms, a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms or a straight- or branched-chain alkenyloxy group containing 3 or 4 carbon atoms, alkyl and alkoxy groups within the definition of R4 being unsubstituted or substituted by a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms, a straight- or branched-chain alkoxy-carbonyl group containing from 2 to 8 carbon atoms, or one or more halogen, e.g. chlorine atoms, or R4 represents a cycloalkyl group containing from 3 to 6 carbon atoms unsubstituted or substituted by a methyl or ethyl group, or R4 represents a phenoxy group, (iii) a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8, and preferably from 1 to 4, carbon atoms or a straight- or branchedchain alkenyl or alkynyl group containing from 2 to 8, and preferably from 2 to 4, carbon atoms, alkyl, alkenyl and alkynyl groups represented by the symbol R5 being unsubstituted or substituted by a cyano group, a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, a carboxy group, a straight- or branched-chain alkoxycarbonyl group containing from 2 to 9 carbon atoms, an aminocarbonyl group unsubstituted or substituted by one or two straight- or branched-chain alkyl groups containing from 1 to 8 carbon atoms and which, when the aminocarbonyl group is substituted by two alkyl groups, may be the same or different, or substituted by one or two straight- or branched-chain alkenyl or alkynyi groups containing from 2 to 8 carbon atoms and which, when the aminocarbonyl group is substituted by two alkenyl or alkynyl groups, may be the same or different, an alkoxyaminocarbonyl group, wherein the alkoxy moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, an alkanesulphonamidocarbonyl group wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, a -C(=O)Het group, wherein Het represents a saturated, nitrogen-containing heterocyclic group having from 3 to 7 atoms in the ring including up to two additional heteroatoms selected from oxygen, nitrogen and sulphur, and linked to the --C(=O))- group of the groupC(=O)Het by the nitrogen atom, or one or more halogen, e.g. chlorine, atoms, or R5 represents a cycloalkyl group containing from 3 to 6 carbon atoms unsubstituted or substituted by one or more straight- or branched-chain lower alkyl groups containing from 1 to 4 carbon atoms, for example a methyl or ethyl group, R2 represents (i) when R1 represents a hydrogen atom, a hydrogen atom, (ii) when R' represents an R4C(-O)- group (wherein R4 is as hereinbefore -defined), a hydrogen atom or an R4C(=0)-- group wherein R4 is as hereinbefore defined, (iii) when R' represents a group R5 (where R5 is as hereinbefore defined), R2 represents a hydrogen atom or a group within the definition of R5 as hereinbefore defined, or R' and R2 together represent C0(CRRb)mCO, wherein Ra and Rb, which may be the same or different, each represent a hydrogen atom or a straightor branched-chain alkyl group containing from 1 to 4 carbon atoms and m represents 2 or 3 or R' and R2, together with the nitrogen atom to which they are attached represent a group of the general formula II herein depicted wherein R8, Rd, Re, Rf, Rg and Rh, which may be the same or different, each represent a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 6 carbon atoms and n represents 0, 1 or 2, and wherein, when n represents 1 or 2, RC and Rd of the portions -[(Rc)C(Rd)]and ~[(RC~)C(Rd)]2 of the group of general formula II, may be the same or different, or R1 represents an alkyl thio group wherein the alkyl moiety contains from 1 to 4 carbon atoms and may be straight- or branched-chain and R2 represents a hydrogen atom, or R' and R2 together with the nitrogen atom to which they are attached represent a group of the general formula XXXII herein depicted wherein RP represent a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms or an amino group substituted by one or two straight- or branched-chain alkyl groups each containing from 1 to 4 carbon atoms, which, when the amino group is substituted by two alkyl groups, may be the same or different, and R9 represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms and R3 represents a group of the general formula Ill herein depicted, wherein R6 represents a chlorine atom, and, when R5 represents an alkyl, alkenyl or alkynyl group substituted by a carboxy group, salts thereof with agriculturally acceptable bases, which possess valuable herbicidal properties.

It is to be understood that when R' and R2 each represent a group R4C(=0)-, wherein R4 is as hereinbefore defined, the aforesaid R4C(=O)- groups may be the same or different.

It is also to be understood that (CRRb)m represents an unsubstitued ethylene or propylene group or an ethylene or propylene group in which one or more of the carbon atoms is substituted by one or two straight- or branched-chain alkyl groups containing from 1 to 4 carbon atoms.

It is also to be understood that, unless otherwise indicated, the term 'halogen' means fluorine, chlorine, bromine or iodine.

It is also to be understood that when R1 and R2 each represent a group R5, wherein R5 is as hereinbefore defined, the aforesaid R5 groups may be the same or different.

By the term 'saits with agriculturally acceptable bases' is meant salts the cations of which are known and accepted in the art for the formation of salts of pesticidally active acids for agricultural or horticultural use.

Preferably, the salts are water-soluble. Suitable salt with bases include alkali metal (e.g. sodium and potassium), alkaline earth metal (e.g. calcium and magnesium), ammonium and amine (e.g.

diethanolamide, triethanolamine, octylamine, morpholine and dioctylmethylamine) salts. It is to be understood that where reference is made in the present specification to the compounds of general formula I, such reference is intended to include also the salts with agriculturally acceptable bases of compounds of general formula I, where appropriate.

The following compounds of general formula I are of particular interest as herbicides: No. Compound 1. 5-amino-4-cyano-1 -(3-chloro-5-trifluoromethylpyrid-2-yl)pyrazole 2. 1-(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-diacetylaminopyrazole 3. 5-acetamido- 1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole 4. 1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-ethylaminopyrazole 5. 1-(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-methoxymethyleneaminopyrazole 6. 1-(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-propionamidopyrazole 7. 1 -(3-chloro-5-trifluoromethylpyrid-2-yI)-4-cyano-5-dichloroacetamidopyrazole 8. 1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-succinimidopyrazole 9. 1-(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-di(phenoxyCarbonyl)aminopyrazole 10. 1-(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-isopropoxyCarbonylaminopyrazole 11. 1 -(3-ch loro-5-trifl uoromethylpyrid-2-yl )-4-cyano-5-methoxycarbonylaminopyrazole 12. 5-(3-chloro-2-methylpropionamido)-1-(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano- pyrazole 1 3. 1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-(3-methyl-2-oxo-azetidin-1 -yl) pyrazole 14. 1 -3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-(2-propenyloxycarbonylamino)pyrazole 1 5. 1 -(3-ch loro-5-trifl uoromethylpyrid-2-yl)-4-cya no-5-pentanamidopyrazole According to a feature of the present invention, there is provided a method for controlling the growth of weeds (i.e. undesired vegetation) at a locus which comprises applying to the locus a herbicidally effective amount of at least one N-pyridylpyrazole derivative of general formula I. For this purpose, the N-pyridylpyrazole derivatives are normally used in the form of herbicidal compositions (i.e.

in association with compatible diluents or carriers suitable for use in herbicidal compositions), for example as hcreinafter described.

The compounds of general formula I show herbicidal activity against dicotyledonous (i.e. broadleafed) and monocotyledonous (e.g. grass) weeds by pre- and/or, post-emergence application.

By the term "pre-emergence application" is meant application to the soil in which the weed seeds or seedlings are present before emergence of the weeds above the surface of the soil. By the term 'post-emergence application' is meant application to the aerial or exposed portions of the weeds which have emerged above the surface of the soil.For example, the compounds of general formula i may be used to control the growth of broad-leafed weeds, for example,Aethusa cynapium, Abutilon theophrasti, A meran thus retroflexus, Amsinckia intermedia, Anagallis arvensis, Anthemis arvensis, Atriplex patula, Bidens pilosa, Brassica nigra, Capsella bursa-pastoris, Chenopodium album, Chrysanthemum segetum, Cirsium arvense, Datura Stramonium, Desmodium tortuosum, Emex australia, Euphorbia helioscopia, Fumaria officinalis, Galeopsis tetrahit, Galium aparine, Geranium dissectum, Ipomea purpurea, Lamium purpureum, Lapsana communis, Matricaria inodora, Monochoria vaginalis, Papaver rhoeas, Physalis longifolia, Plantago lanceolata, Polygonum spp., (e.g. Polygonum lapathifolium, Polygonium aviculare, Polygonum convolvulus and Polygonum persicaria), Portulaca oleracea, Raphanus raphanistrum, Rotala indica, Rumex obtusifolius, Saponaria vaccaria, Scandix pecten-veneris, Senecio vulgaris, Sesbania florida, Sida spinosa, Silene alba, Sinapis arvensis, Solanum nigrum, Sonchus arvensis, Spergula arvensis, Stellaria media, Thlaspi arvense, Tribulus terrestria, Urtica urens, Veronica hederifolia, Veronica persica, Viola arvensis and Xanthium strumarium, and grass weeds, for example, Alopecurus myosuroides, Apera spica-venti, Agrostis stolonifera, Avena fatua, Avena ludoviciana, Brachiaria spp., Bromus sterilis, Bromus tectorum, Cenchrus spp., Cynodon dactylon, Digitaria sanquinalis, Echinochloa crus-galli, Elusine indica, Setaria viridis and Sorghum halepense and sedges, for example Cyperus esculentus, Cyperus iria and Cyperus rotundus, and Eleocharis a cicularis.

The amounts of compounds of general formula I applied vary with the nature of the weeds, the compositions used, the time of application, the climatic and edaphic conditions and (when used to control the growth of weeds in crop-growing areas) the nature of the crops. When applied to a cropgrowing area, the rate of application should be sufficient to control the growth of weeds without causing substantial permanent damage to the crop. In general, taking these factors into account, application rates between 0.01 kg and 10 kg of active material per hectare give good results. However, it is to be understood that higher or lower application rates may be used, depending upon the particular problem of weed control encountered.

The compounds of general formula I may be used to control selectively the growth of weeds, for example to control the growth of those species hereinbefore mentioned, by pre- or post-emergence application in a directional or non-directional fashion, e.g. by direction or non-directional spraying, to a locus of weed infestation which is an area used, or to be used, for growing crops, for example cereals, e.g. wheat, barley, oats, maize and rice, soya beans, field and dwarf beans, peas, lucerne, cotton, peanuts, flax, onions, carrots, cabbage, oilseed rape sunflower, sugar beet, and permanent or sown grassland before or after sowing of the crop or before or after emergence of the crop.For the selective control of weeds at a locus of weed infestation which is an area used, or to be used, for the growing of crops, e.g. the crops hereinbefore mentioned, application rates between 0.01 kg and 4.0 kg, and preferably between 0.01 kg and 2.0 kg, of active material per hectare are particularly suitable. More particularly, the compounds of general formula I may be used to control selectively the growth of broad leafed weeds, for-example to control the growth of those broad leafed species hereinbefore mentioned, by pre- or, more especially, post-emergence application in a non-directional fashion, e.g. by nondirectional spraying, to an area used for growing cereal crops before or after emergence of both the crop and weeds.

For this purpose, i.e. the selective control of broad leafed weeds by pre- or post-emergence application to an area used for growing cereal crops, application rates between 0.01 and 4.0 kg, and preferably between 0.01 kg and 2.0 kg, of active material per hectare are particularly suitable.

The compounds of general formula I may also be used to control the growth of weeds, especially those indicated above, by pre- or post-emergence application in established orchards and other treegrowing areas, for example forests, woods and parks, and plantations e.g. sugar cane, oil palm and rubber plantations. For this purpose they may be applied in a directional or non-directional fashion (e.g.

by direction or non-directional spraying) to the weeds or to the soil in which they are expected to appear, before or after planting of the trees or plantations at application rates between 0.25 kg and 10.0 kg, and preferably between 1.0 kg and 4.0 kg, of active material per hectare.

The compounds of general formula I may also be used to control the growth of weeds, especially those indicated above, at loci which are not crop-growing areas but in which the control of weeds is nevertheless desirable. Examples of such non-crop-growing areas include airfields, industrial sites, railways, roadside verges, the verges of rivers, irrigation and other waterways, scrublands and fallow or uncultivated land, in particular where it is desired to control the growth of weeds in order to reduce fire risks. When use for such purposes in which a total herbicidal effect is frequently desired, the active compounds are normally applied at dosage rates higher than those used in crop-growing areas as hereinbefore described. The precise dosage will depend upon the nature of the vegetation treated and the effect sought.Pre- or post-emergence application, and preferably pre-emergence application, in a directional or non-directional fashion (e.g. by directional or non-directional spraying) at application rates between 2.0 kg and 10.0 kg, and preferably between 4.0 and 10.0 kg, of active laterial per hectare are particularly suitable for this purpose.

- When used to control the growth of weeds by pre-emergence application, the compounds of general formula I may be incorporated into the soil in which the weeds are expected to emerge. It will be appreciated that when the compounds of general formula I are used to control the growth of weeds by post-emergence application, i.e. by application to the aerial or exposed portions of emerged weeds, the compounds of general formula I will also normally come into contact with the soil and may also then exercise a pre-emergence control on later-germinating weeds in the soil.

Where especially prolonged weed control is required, the application of the compounds of general formula I may be repeated if required.

According to a further feature of the present invention, there are provided compositions suitable for herbicidal use comprising one or more of the N-pyridylpyrazole derivatives of general formula I in association with, and preferably homogeneously dispersed in, one or more compatible herbicidallyacceptable diluents or carriers (i.e. diluents or carriers of the type generally accepted in the art as being suitable for use in herbicidal compositions and which are compatible with compounds of general formula 1). The term "homogeneously dispersed" is used to include compositions in which the compounds of general formula I are dissolved in the other components. The term "herbicidal compositions" is used in a broad sense to include not only compositions which are ready for use as herbicides but also concentrates which must be diluted before use.Preferably, the compositions contain from 0.05 to 90% by weight of one or more compounds of general formula I.

The herbicidal compositions may contain both a diluent or carrier and surface-active (e.g. wetting, dispersing, or emulsifying) agent. Surface-active agents which may be present in herbicidal compositions of the present invention may be of the ionic or non-ionic types, for example sulphoricinoleates, quaternary ammonium derivatives, products based on condensates of ethylene oxide with alkyl and polyaryl phenols, e.g. nonyl- or octyl-phenols, or carboxylic acid esters of anhydrosorbitols which have been rendered soluble by etherification of the free hydroxy groups by condensation with ethylene oxide, alkali and alkaline earth metal salts of sulphuric acid esters and sulphonic acids such as dinonyl- and dioctyl-sodium sulphonosuccinates and alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodium and calcium lignosulphonates and sodium and calcium alkylbenzene sulphonates.

Suitably, the herbicidal compositions according to the present invention may comprise up to 10%, e.g. from 0.05% to 10%, of surface-active agent but, if desired, herbicidal compositions according to the present invention may comprise higher proportions of surface-active agent, for example up to 15% in liquid emulsifiable suspension concentrates and up to 25% in liquid water soluble concentrates.

Examples of suitable solid diluents or carriers are aluminium silicate, talc, calcined magnesia, kieselguhr, tricalcium phosphate, powdered cork, adsorbent carbon black and clays such as kaolin and bentonite. The solid compositions (which may take the form of dusts, granules or wettable powders) are preferably prepared by grinding the compounds of general formula I with solid diluents or by impregnating the solid diluents or carriers with solutions of the compounds of general formula I in volatile solvents, evaporating the solvents and, if necessary, grinding the products so as to obtain powders.Granular formulations may be prepared by absorbing the compounds of general formula I (dissolved in suitable solvents, which may, if desired, be volatile) onto the solid diluents or carriers in granular form and, if desired, evaporating the solvents, or by granulating compositions in powder form obtained as described above. Solid herbicidal compositions, particularly wettable powders and granules, may contain wetting or dispersing agent (for example of the types described above), which may also, when solid, serve as diluents or carriers.

Liquid compositions according to the invention may take the form of aqueous, organic or aqueous-organic solutions, suspension and emulsions which may incorporate a surface-active agent.

Suitable liquid diluents for incorporation in the liquid compositions include water, glycols, tetrahydrofurfuryl alcohol, acetophenone, cyclohexanone, isophorone, toluene, xylene, mineral, animal and vegetable oils and light aromatic and naphthenic fractions of petroleum (and mixtures of these diluents). Surface-active agents, which may be present in the liquid compositions, may be ionic or nonionic (for example of the types described above) and may, when liquid, also serve as diluents or carriers.

Wettable powders, dispersible granules and liquid compositions in the form of concentrates may be diluted with water or other suitable diluents, for example mineral or vegetable oils, particularly in the case of liquid concentrates in which the diluent or carrier is an oil, to give compositions ready for use.

When desired, liquid compositions of the compound of general formula I may be used in the form of self-emulsifying concentrates containing the active substances dissolved in the emulsifying agents or in solvents containing emulsifying agents compatible with the active substances, the simple addition of water to such concentrates producing compositions ready for use.

Liquid concentrates in which the diluent or carrier is an oil may be used without further dilution using the electrostatic spray technique.

Herbicidal compositions according to the present invention may also contain, if desired, conventional adjuvants such as adhesives, protective colloids, thickeners, penetrating agents, stabilisers, sequestering agents, anti-caking agents, colouring agents and corrosion inhibitors. These adjuvants may also serve as carriers or diluents.

Preferred herbicidal compositions according to the present invention are aqueous suspension concentrates which comprise from 10 to 70% of one or more compounds of general formula I, from 2 to 10% of surface-active agent, from 0.1 to 5% w/v (weight/volume) of thickener and from 1 5 to 87.9% by volume of water; wettable powders which comprise from 10 to 90% w/w (weight/weight) of one or more compounds of general formula I, from 2 to 10% w/w of surface-active agent and from 10 to 88% w/w of solid diluent or carrier; liquid water soluble concentrates which comprise from 5 to 50%, e.g. 10 to 30%, w/v of one or more compounds of general formula I, from 5 to 25% w/v of surface-active agent and from 25 to 90%, e.g. 45 to 85%, by volume of water-miscible solvent e.g.

dimethylformamide, or a mixture of water-miscible solvent and water; liquid emulsifiable suspension concentrates which comprise from 10 to 70% w/v of one or more compounds of general formula I, from 5 to 1 5% w/v of surface-active agent, from 0.1 to 5% w/v of thickener and from 10 to 84.9% by volume of organic solvent; granules which comprise from 1 to 90%, e.g. 2 to 10%, w/w of one or more compounds of general formula I, from 0.5 to 7%, e.g. 0.5 to 2%, w/w of surface-active agent and from 3 to 98.5%, e.g. 88 to 97.5%, w/w of granular carrier; and emulsifiable concentrates which comprise 0.05 to 90% w/v, and preferably from 1 to 60% w/v of one or more compounds of general formula I, from 0.01 to 10% w/v, and preferably from 1 to 10% w/v, of surface-active agent and from 9.99 to 99.94%, and preferably from 39 to 98.99%, by volume of organic solvent.

Herbicidal compositions according to the present invention may also comprise the compounds of general formula I in association with, and preferably homogeneously dispersed in, one or more other pesticidally active compounds and, if desired, one or more compatible pesticidally acceptable diluents or carriers, surface-active agents and conventional adjuvants as hereinbefore described.Examples of other pesticidally active compounds which may be included in, or used in conjunction with, the herbicidal compositions of the present invention include herbicides, for example to increase the range of weed species controlled, for example alachlor [2-chloro-2' ,6'-diethyl-N-( methoxymethyl)- acetanilide], asulam [methyl(4-aminobenzenesulphonyl)carbamate], alloxydim Na [sodium salt of 2-(1 allyloxyaminobutylidene)-5,5-dimethyl-4-methoxycarbonylcyclohexane-1 ,3-dione], atrazine [2-chloro 4-ethylamino-6-isopropylamino-1 3,5-triazine], barban [4-chlorobut-2-ynyl N-(3-chlorophenyl)carbamate], benzoylprop-ethyl [ethyl N-benz6yl-N-(3,4-dichlornphenyl-2-a mi nopropionate], bromoxynil [3,5-dibromo-4-hydroxybenzonitrile], butachlor [N-(butoxymethyl)-2-chloro-2',6'-diethylacetanilide], butylate [S-ethyl N,N-diisobutyl(thiocarbamate)], carbetamide [D-N-ethyl-2-(phenylcarbamoxyloxy)propionamide], chlorfenprop-methyl [methyl 2-chloro-3-(4-chlorophenyl)propionate], chlorpropham [isopropyl N-(3-chlorophenyl)carbamate], chlortoluron [N'-(3-chloro-4-methylphenyl)-N,N- dimethylurea], cyanazine [2-chloro-4-( 1 -cyano- 1 -methylethylamino)-6-ethylamino-1 ,3,5-triazine], cycloate [N'-cyclohexyl-N-ethyl-S-ethyl(thiocarbamate)3, 2,4-D [2,4-dichlorophenoxyacetic acid], dalapon [2,2-dichloropropionic acid], 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid], desmedipham [3 (ethoxycarbonylamino)phenyl N-phenyl-carba mate], diva slate [S-2,3-dichloroallyl-N,N-di-isopropyl (thiocarbamate)], dicamba [3,6-dichloro-2-methoxybenzoic acid], dichlorprop [(+)-2-(2,4-dichloro- phenoxy)propionic acid], difenzoquat [1 ,2-dimethyl-3,5-diphenyl-pyrazolium salts], dimefuron 4-[2- chloro-4-(3,3-dimethylureido)phenyl]-2-t-butyl- 1 ,3,4-oxadiazolin-5-one, dinitramine [N1,N1-diethyl-- 2,6-dinitro-4-trifluoromethyl-m-phenylenediamine], diuron [N'-(3,4-dichlorophenyl)-N,Ndimethylurea], EPTC [S-ethyl N,N-dipropyl(thiocarba mate)], ethofu mesate [2-ethoxy-2,3-dihydro-3,3- dimethylbenzofuran-5-yl methylsulphonate], flampropisopropyl [isopropyl (+)-2-(N-benzoyl-3-chlorn- 4-fluoroanilino)propionate], flampropmethyl [methyl (+)-2-(N-benzoy-3-chloro-4-fluoroanilino)- propionate], fluometuron [N'-(3-trifluoromethylphenyl)-N,N-dimethylurea], ioxynil [4-hydroxy-3,5-diiodobenzonitrile], isoproturon [N'-(4-isopropylphenyl)-N,N-dimethylureai, linuron [N-(3,4-dichlorophenyl-N-methoxy-N-methylurea], MCPA [4-chloro-2-methylphenoxyacetic acid, MCP B [4-(4-chloro2-methylphenoxy)butyric acid], mecoprop [(+)-2-(4-chloro-2-methylphenoxy)propionic acid], metamitron i4-amino-3-methyl-6-phenyl- 1 ,2,4-triazin-5(4H)-one], methabenzthiazuron [N-(benzo thiazol-2-yl)-N ,N'-dimethyl urea], metribuzin [4-amino-6-t-butyi-3-(methylthio)- 1 ,2,4-triazin-5(4H)one], molinate [S-ethyl N,N-hexamethylene(thiocarbamate)], oxadiazon [3-(2,4-dichloro-5-isopropoxyphenyl)-5-t-butyl-1 ,3,4-oxadiazolin-2-one], paraquat [1,1 '-dimethyl-4,4'-bipyridylium salts], pebulate [S-propyl N-butyl-N-ethyl(thiocarbanate)], phenmedipham [3-(methoxycarbonylamino)phenyl N-(3methylphenyl)carbamate], prometryne [4,6-bisisopropyla mino-2-methylthio- 1 ,3,5-triazine], propachlor [2-chloro-N-isopropylacetanilide], propanil [N-(3,4-dichlorophenyl)propionamide], propha m [isopropyl N-phenylca rba mate], pyrazole [5-amino-47chlorn-2-phenylpyridazin-3(2H)-one], simazine [2-chloro4,6-bisethylamino-1 ,3,5-triazine], TCA (trichloroacetic acid], thiobencarb [S-(4-chlorobenzyl)-N,Ndiethylthiolcarbamate], tri-allate [S-2,3,3-trichloroallyl N,N-di-isopropyl(thiocarbamate)] and trifluralin [2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline]; insecticides, e.g. carbaryi [naphth- 1 -yl N-methylcarbamate]; synthetic pyrethroids, e.g. permethrin and cypermethrin; and fungicides, e.g. 2,6-dimethyl4-tridecyl-morpholine, methyl N-( 1 -butylcarbamoyl-benzimidazol-2-yl)carbamate, 1,2-bis-(3-methoxy carbonyl-2-thioureido)benzene, isopropyl 1 -ca rba moyl-3-(3, 5-dichlorophenyl) hydantoin and 1-(4 chloro-phenoxy)-3,3-dimethyl- 1-(1 ,2,4-triazol- 1 -yl)butan -2-one. Other biologically active materials which may be included in, or used in conjunction with, the herbicidal compositions of the present invention are plant growth regulators, e.g. succinamic acid, (2-chloroethyl)trimethylammonium chloride and 2-chloroethane-phosphonic acid; or fertilizers, e.g. containing nitrogen, potassium and phosphorus and trace elements known to be essential to successful plant life, e.g. iron, magnesium, zinc, maganese, cobalt and copper.

Pesticidally active compounds and other biological active materials which may be included in, or used in conjunction with, the herbicidal compositions of the present invention, for example those hereinbefore mentioned, and which are acids, may, if desired, be utilized in the form of conventional derivatives, for example alkali metal and amine salts and esters.

According to a further feature of the present invention there is provided an article of manufacture comprising at least one of the N-pyridylpyrazole derivatives of general formula I or, as is preferred, a herbicidal composition as hereinbefore described, and preferably a herbicidal concentrate which must be diluted before use, comprising at least one of the N-pyridylpyrazole derivative of general formula I within a container for the aforesaid derivative or derivatives of general formula I, or a said herbicidal composition, and instructions physically associated with the aforesaid container setting out the manner in which the aforesaid derivative or derivatives of general formula I or herbicidal composition contained therein is to be used to control the growth of weeds. The containers will normally be of the types conventionally used for the storage of chemical substances which are solid at normal ambient temperatures and herbicidal compositions particularly in the form of concentrates, for example cans and drums of metal, which may be internally-lacquered, and plastics materials, bottles of glass and plastics materials and, when the contents of the container is a solid, for example granular, herbicidal compositions, boxes, for example of cardboard, plastics materials and metal, or sacks. The containers will normally be of sufficient capacity to contain amounts of the N-pyridylpyrazole derivative or herbicidal compositions sufficient to treat at least one acre of ground to control the growth of weeds therein but will not exceed a size which is convenient for conventional methods of handling.The instructions will be physically associated with the container, for example by being printed directly there on or on a label or tag affixed thereto. The directions will normally indicate that the contents of the container, after dilution if necessary, are to be applied to control the growth of weeds at rates of application between 0.01 kg and 10 kg of active material per hectare in the manner and for the purposes hereinbefore described.

The following Examples illustrate herbicidal compositions according to the present invention: EXAMPLE 1 A wettable powder was formed from: 5-amino-l -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole 50% w/w Ethylan BCP (a nonylphenyl/ethylene oxide condensate containing 9 moles of ethylene oxide per mol of phenol) 5% w/w Aerosil (silicon dioxide of microfine particle size) 5% w/w Celite PF (synthetic magnesium silicate carrier) 40% w/w by absorbing the Ethylan BCP onto the Aerosil, mixing with the other ingredients and grinding the mixture in a hammer-mill to give a wettable powder which may be diluted with water and applied at an application rate of 1 kg of wettable powder in 300 litres of spray fluid per hectare to control the growth of Gallium aparine, Veronica persica and Viola arvensis by post-emergence application in an emerged crop of winter wheat.

Similar wettable powders may be prepared as described above by replacing the 5-amino-1 -(3chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole by other compounds of general formula I.

EXAMPLE 2 An aqueous suspension concentrate was formed from: 5-amino-l -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole 50% w/w Ethyl an BCP 1.0% w/v Sopropon T36 (sodium salt of polycarboxylic acid) 0.2% w/v Ethylene glycol 5% w/v Rhodigel 23 (polysaccharide xanthan gum thickener) 0.1 w/v distilled water to 1 00% by volume by intimately mixing the ingredients and grinding in a ball-mill for 24 hours. The concentrate thus obtained may be dispersed in water and applied at an application rate of 500 g of aqueous suspension concentrate in 200 litres of spray fluid per hectare to control the growth of Galium aparine, Veronica persica and Viola arvensis by post-emergence application in an emerged crop of winter barley.

Similar aqueous concentrates may be prepared as described above by replacing the 5-amino-1- (3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole by other compounds of general formula I.

In experiments on herbicidal activity carried out on representative compounds of general formula I, the following results have been obtained.

Test Method Test Procedure The solutions of the test compounds, hereinafter identified by the Compound Nos. hereinbefore indicated, were prepared by dissolving the test compounds in acetone. Application was from a standard laboratory herbicide sprayer using a flat fan jet travelling at 1.8 m.p.h. (2.9 km/hour) and delivering the equivalent of 540 litres of spray fluid per hectare, the spray pressure being 2.6 kg/cm2 (37 pounds/inch2). The solutions of the test compounds were prepared by dissolving 0.089 g of test compound in 24 ml [equivalent to an application rate of 2000 g of test compound per hectare (g/ha) and solutions equivalent to 500, 125, 31 and 8 g/ha were prepared by four-fold serial dilution with acetone.

(b) Weed Control: Pre-emergence Application Weed seeds were sown on the surface of John Innes No. 1 potting compost (7 parts by volume of sterilized loam, 3 parts by volume of peat and 2 parts by volume of fine grit) in 7 cm-square plastic pots. The quantities of seeds per pot were as follows:- Approximate Number Weed Species of Seeds/Pot (i) Broad leafed weeds Chenopodium album 50 Brassica kaber 30-40 AbutilontheophrasV 1 5 ipomea purpurea 8 (ii) Grass weeds Avena fatua 1 5-20 Echinochloa crus-galli 30 The test compounds were applied as described above and the seeds were covered with 25 ml of sharp -sand after spraying. A single pot of each weed species was allocated to each treatment, with unsprayed controls and controls sprayed with acetone alone.After treatment, the pots were kept in the greenhouse and watered overhead. Visual assessment of percentage weed destruction was made 20 days after spraying, in comparison with unsprayed controls. The percentate weed destruction figures were then plotted against application rates to calcuiate the effective dose (EDgo) in grammes per hectare which produced 90% destruction of weeds. The results obtained are presented below in Table (c) Weed Control: Post-Emergence Application Weed species were grown and then transplanted at the seedling stage into John Innes No. 1 potting compost in 7 cm-square plastic pots, except forAvena fatua, which was sown directly in the test pot and not transplanted. The plants were then grown in the greenhouse until ready for spraying with the test compounds.The number of plants per pot and the growth stage of the plant at spraying were as follows:- Number of Growth Stage Weed Species Plants/Pot at Spraying (i) Broad leafed weeds Chenopodium album 4 4 leaves Brassica kaber 4 2 leaves Abutilon theophrasti 3 1-2 leaves lmpomea purpurea 3 2 leaves (iii) Grass weeds and sedges Avenafatua 10 1-2 leaves Echinochloa crus-galli 4 1-2 leaves Cyperus esculentus 3 2-3 leaves The test compounds were applied as described above. A single pot of each weed species was allocated to each treatment, with unsprayed controls and controls sprayed with acetone alone.After spraying, the pots were kept in the greenhouse and watered overhead, commencing 24 hours after spraying.

Visual assessment of % age weed destruction in comparison with unsprayed controls was made 20 days after spraying. The EDgo values in g/ha were then caiculated as described above. The results obtained are presented below in Table II.

Key to Weed Species (a) Broad-leaf weeds Ca=Chenopodium album Bk=Brassica kaber At=Abutilon theophrasti Ip=lpomea purpurea (b) Grass weeds Af=Avena fatua Ec=Echinochloa crus-galli (c) Sedges Ce=Cyperus esculentus TABLE I

T.C. Pre-Emergence ED90 (giha) A.R. No. g/ha Ca Bk At Ip Af Ec 1 19 64 60 71 125 95 8-2000 2 18 21 18 20 180 48 8-2000 3 12 49 14 50 172 59- 8-2000

TABLE II

T.C. Post-Emergence ED90 (g/ha) A.R. No. g/ha Ca Bk At Ip Af Ec Ce 1 75 100 125 22 2000 810 2000 8-2000 2 32 210 8 50 2000 88 2000 8-2000 3 < 8 172 < 8 < 8 615 49 956 8-2000

The following symbols which appear in the above Tables have the following meanings: 'T.C. No.' means=(Test) Compound Number.

'A.R. g/ha' means=Application Rates (g/ha) applied in the test in question.

' < ' means=less than.

According to a feature of the present invention, the compounds of general formula I wherein R1 and R2 each represent a hydrogen atom and R3 is as hereinbefore defined, i.e. the compound of formula IA herein depicted, wherein R3 is as hereinbefore defined, are prepared by the process which comprises the cyclisation of the compound of formula IV herein depicted, wherein R3 is as hereinbefore defined (i.e. 3-chloro-5-trifluoromethylpyrid-2-ylhydrazinomethylenemalononitdle). Cyclisation may be effected in the presence of an inert organic solvent, for example an alkanol containing from 1 to 4 carbon atoms (e.g. ethanol), acetic acid or ethoxyethanol, at a temperature of from ambient temperature up to the reflux temperature of the reaction mixture.

The compound of formula IV may be prepared by the reaction of the compound of formula V herein depicted, wherein R3 is as hereinbefore defined (i.e. 3-chloro-2-hydrazino-5-trifluoromethyl- pyridine), or an acid addition salt thereof, with a compound of general formula VI herein depicted, wherein R7 represents a straight- or branched-chain alkyl radical containing from 1 to 4 carbon atoms, preferably ethyl.

The reaction of a compound of general formula V with the compound of formula VI may be effected in the presence of a suitable inert organic solvent, for example an alkanol containing from 1 to 4 carbon atoms (e.g. ethanol), acetic acid or ethoxyethanol and at a temperature of from ambient temperature to the reflux temperature of the reaction mixture and optionally in the presence of an alkali metal (e.g. sodium or potassium) acetate, carbonate or bicarbonate, or alkoxide containing from 1 to 4 carbon atoms, e.g. ethoxide. When an acid addition salt of the compound of general formula V is used, the reaction with the compound of general formula Vl is effected in the presence of an alkali metal (e.g.

sodium or potassium) acetate, carbonate or bicarbonate.

The compound of formula IA, wherein R3 is as hereinbefore defined, may, according to another feature of the present invention, be prepared by reaction of the compound of formula V with a compound of general formula VI as hereinbefore described without isolation of the intermediate compound of formula IV from the reaction mixture.When the reaction of the compound of formula V with a compound of general formula VI is effected in acetic acid, in the absence or presence of an alkali metal (e.g. sodium or potassium) acetate, the intermediate compound of formula IV may separate from the reaction mixture, depending upon the solubility of the intermediate compound of general formula IV in the reaction medium, and may, if desired, be isolated before being cyclised as hereinbefore described to the compound of formula IA, preferably by heating in an inert organic solvent (e.g ethoxyethanol) at the reflux temperature of the reaction mixture.

The compound of formula IV exhibits herbicidal activities similar to those of the corresponding compound of formula IA into which it may be cyclised, and it is believed that the herbicidal activity of the compound of formula IV results from its cyclisation to the compound of formula IA.

According to a further feature of the present invention, the compounds of general formula I wherein RX represents an R5C(=O)- group, wherein R8 has the meanings hereinbefore indicated for R4 except for the hydrogen atom, R2 represents a hydrogen atom or an R8C(=0)-- group, wherein R5 is as hereinbefore defined, which is identical to the group R8C(=0)-- represented by R', and R3 is as hereinbefore defined, i.e. compounds of the general formula IB herein depicted wherein R9 represents an R8C(=0)-- group, wherein R8 is as hereinbefore defined, R'O represents a hydrogen atom or an R8C(=O)- group, wherein R8 is as hereinbefore defined and is identical to the group represented by the symbol R8 in the definition of the symbol R9, and R3 is as hereinbefore defined, are prepared by the reaction of the compound of the formula IA wherein R3 is as hereinbefore defined, with a compound of the general formula VII herein depicted wherein X represents a chlorine or bromine atom and R8 is as hereinbefore defined, or with a compound of the general formula Vill herein depicted wherein R8 is as hereinbefore defined, in the absence or presence of a suitable inert organic solvent, for example a ketone, e.g. acetone, an aromatic hydrocarbon, e.g. benzene or toluene, chloroform, dichloromethane or dimethylformamide, and optionally in the presence of an acid-binding agent, for example pyridine, triethylamine or an alkali metal, e.g. sodium or potassium, carbonate or bicarbonate, at a temperature from OOC to the reflux temperature of the reaction medium, to give a compound of general formula IB wherein R9 is as hereinbefore defined and R10 represents either a hydrogen atom or an R8C(=O)- group, wherein R8 is as hereinbefore defined, depending upon the reaction conditions chosen and/or the use of an excess of the compound of general formula VII or VI II. If desired, an alkali metal derivative of the compound of general formula IA may be used.

According to a further feature of the present invention, the compounds of general formula I wherein R' represents an R4aC(=O)-- group, wherein R4a represents a hydrogen atom, R2 represents a hydrogen aton and R3 is as hereinbefore defined, i.e. compounds of the general formula IC herein depicted wherein R3 is as hereinbefore defined, are prepared by reaction of the compound of formula IA, wherein R3 is as hereinbefore defined, with formic acid, preferably in a suitable inert organic solvent, for example a ketone, e.g. methylisobutyl ketone, or an aromatic hydrocarbon, e.g. benzene or toluene, at the reflux temperature of the reaction mixture.

According to a further feature of the present invention, the compounds of general formula I wherein R' represents an R4aC(=O)-- group, wherein R4a represents a hydrogen atom, R2 represents a hydrogen atom or an R4aC(=o)group, wherein R4a represents a hydrogen atom, and R3 is as hereinbefore defined, i.e. compounds of the general formula ID herein depicted wherein R" represents a hydrogen atom or an HC(=O)-- group and R3 is as hereinbefore defined, are prepared by the reaction of the compound of formula IA wherein R3 is as hereinbefore defined, with formylacetic anhydride (which may be prepared from formic acid and acetic an hydride), in the absence or presence of a suitable inert organic solvent, for example a ketone, e.g. acetone, or an aromatic hydrocarbon, e.g.

benzene or toluene, and optionally in the presence of an acid-binding agent, for example pyridine, triethylamine or an alkali metal, e.g. sodium or potassium, carbonate or bicarbonate, at a temperature from OOC to the reflux temperature of the reaction mixture, to give a compound of general formula ID wherein R3 is as hereinbefore defined and R11 represents a hydrogen atom or an HC(=O)-- group, depending upon the reaction conditions chosen and/or the use of an excess of formylacetic anhydride.

According to a further feature of the present invention, the compounds of general formula I wherein R' represents an R4C(=0)-- group, wherein R4 is as hereinbefore defined, R2 represents a hydrogen atom and R3 is as hereinbefore defined, i.e. compounds of the general formula lE herein depicted, wherein R12 represents an R4C(=O)- group, wherein R4 is as hereinbefore defined, and R3 is as hereinbefore defined, are prepared by the selective removal by hydrolysis under mild conditions of an R8C(=O)- group represented by the symbol R'O of a compound of general formula IB (wherein R3 and R9 are as hereinbefore defined) or an HC(=O)-- group represented by the symbol R" of the compound of formula ID (wherein R3 is as hereinbefore defined), i.e. the selective hydrolysis under mild conditions of a compound of general formula I wherein R' and R2 each represent an R4C(=0)-- group and R3 and R4 are as hereinbefore defined, to convert one of the groups R4C(=O)-to a hydrogen atom.

Hydrolysis may be effected, for example, by treatment with an aqueous-ethanolic solution or suspension of an alkali metal, e.g. sodium or potassium, bicarbonate, or with aqueous ammonia.

According to a further feature of the present invention, the compounds of general formula I wherein R: represents an R4bC(O) group, wherein R4b represents an unsubstituted or substituted straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms as hereinbefore defined for R4, R2 represents a hydrogen atom and R3 is as hereinbefore defined, i.e. compounds of the general formula IF herein depicted wherein R'3 represents an R14C(-0)- group, wherein R'4 is as hereinbefore defined for R4b and R3 is as hereinbefore defined, are prepared by the reaction of a compound of the general formula IG herein depicted wherein R15 represents a group R'EC(=O)--, wherein R16 represents a group within the definition of R14 as hereinbefore defined or a phenoxy group, and R3 is as hereinbefore defined, with a compound of the general formula IX herein depicted wherein R'4 is as hereinbefore defined, to replace one of the groups represented by the symbol R15 by a hydrogen atom, to replace the other group represented by the symbol R15 by a group within the definition of R'3 when R15 represents a group R'6C(=0)-- wherein R16 represents a phenoxy group, and, if desired, to replace the other group represented by the symbol R15 by another group represented by the symbol R'3 when R15 represents a group R'6C(=0)--, wherein R16 represents a group within the definition of R14. As will be apparent to those skilled in the art, the desired compound of general formula IF is obtained by selection of the appropriate compounds of general formulae IG and IX.The reaction may be effected in water or a suitable inert aqueous-organic or organic solvent, for example an alkanol containing 1 to 4 carbon atoms, e.g. ethanol, or an aromatic hydrocarbon, e.g. benzene or toluene, or which is preferably an excess of the compound of general formula IX, at a temperature from ambient temperature to the reflux temperature of the reaction mixture and, if necessary, at elevated pressure, and optionally in the presence of a base, for example an alkali metal alkoxide, e.g. of the compound of general formula IX.

According to a further feature of the present invention, the compounds of general formula I wherein R' represents an R4C(-O)- group, wherein R4 is as hereinbefore defined, R2 represents an R4C(=O)- group, wherein R4 is as hereinbefore defined, which may be the same as, or different to, the R4C(=0)-- group represented by the symbol R' and R3 is as hereinbefore defined, i.e. compounds of the general formula IH herein depicted wherein R3 and R12 are as hereinbefore defined and R'7 represents an R4C(=O)- group, wherein R4 is as hereinbefore defined, which may be the same as, or different to, the R4C(=O)- group represented by the symbol R'2, are prepared by the reaction of an alkali metal, e.g. sodium or potassium, derivative of a compound of general formula IB, wherein R3 and R9 are as hereinbefore defined and R'O represents a hydrogen atom, or of the compound of formula IC, wherein R3 is as hereinbefore defined, i.e. a compound of general formula IE wherein R3 and R12 are as hereinbefore defined, with formic acid, formylacetic anhydride or a compound of general formula VII, wherein R5 and X are as hereinbefore defined. Reaction may be effected in a suitable aprotic solvent, e.g. dimethylformamide, at a temperature from laboratory temperature to the reflux temperature of-the reaction mixture.

According to a further feature of the present invention, the compounds of general formula I wherein R' amd R2 together represent CO(CRaRb)mCO and R3, Ra, Rb and m are as hereinbefore defined, are prepared by the reaction of the compound of formula IA, wherein R3 is as hereinbefore defined, with a compound of the general formula X herein depicted wherein X, Ra, Rb and m are as hereinbefore defined, or with a compound of the general formula XI herein depicted wherein Ra, Rb and m are as hereinbefore defined, in the absence or presence of a suitable inert organic solvent, for example a ketone, e.g. acetone, an aromatic hydrocarbon, e.g. benzene or toluene, chloroform, dichloromethane or dimethylformamide, and optionally in the presence of an acid-binding agent, for example pyridine, triethylamine or an alkali metal, e.g. sodium or potassium, carbonate or bicarbonate, at a temperature from 00C to the reflux temperature of the reaction medium. If desired, an alkali metal derivative of the compound of general formula IA may be used.

Alkali metal derivatives of compounds of general formula IA or IE may be prepared in situ by reaction of the compounds of general formulae IA or IE, wherein R3 and R12 are as hereinbefore defined, with an alkali metal, e.g. sodium or potassium, hydride, in a suitable inert aprotic solvent, e.g.

dimethylformamide, at a temperature from laboratory temperature to the reflux temperature of the reaction mixture.

Accordingly to a further feature of the present invention, compounds of general formula I wherein R' represents a group R5 (wherein R5 is as hereinbefore defined), R2 represents a hydrogen atom or a group within the definition of R5 as hereinbefore defined and R3 is as hereinbefore defined, i.e.

compounds of the general formula IJ herein depicted, wherein R'7 represents a hydrogen atom or a group within the definition of R5 as hereinbefore defined and R3 and R5 are as hereinbefore defined, are prepared by the reaction of a compound of the general formula XII herein depicted wherein R5 and R'7 are as hereinbefore defined and R18 represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, preferably ethyl, with the compound of the formula V herein depicted, wherein R3 is as hereinbefore defined, or an acid addition salt thereof, e.g. the hydrochloride.

The reaction of a compound of general formula XII with the compound of formula V may be effected in the presence of a suitable inert organic solvent, for example an alkanol containing from 1 to 4 carbon atoms, e.g. ethanol, acetic acid or ethoxyethanol, and at a temperature of from ambient temperature to the reflux temperature of the reaction mixture, and optionally in the presence of an alkali metal, e.g. sodium or potassium, acetate, carbonate or bicarbonate. When an acid addition salt of the compound of general formula V is used, the reaction with the compounds of general formula XII is effected in the presence of an alkali metal, e.g. sodium or potassium, acetate, carbonate or bicarbonate.

According to a further feature of the present invention, compounds of general formula I wherein R1 represents a group R5 (wherein R5 is as hereinbefore defined), R3 is as hereinbefore defined and R2 represents a hydrogen atom or a group identical to the group R5 represented by the symbol R', i.e.

compounds of the general formula IK herein depicted, wherein R3 and R5 are as hereinbefore defined and R5" represents a hydrogen atom or a group identical to the group R5, are prepared by the reaction of the compound of the formula IA herein depicted, wherein R3 is hereinbefore defined or an alkali metal, e.g. sodium or potassium, derivative thereof, with one or two molar proportions a compound of the general formula XIII herein depicted, wherein R5 is as hereinbefore defined and X' represents a chlorine, bromine or iodine atom, in the absence or presence of a suitable inert organic solvent, for example an aromatic hydrocarbon, e.g. benzene or toluene, chloroform, dichloromethane, tetrahydrofuran or dimethylformamide and optionally in the presence bf an acid-binding agent, for example pyridine, triethylamine, an alkali metal, e.g. sodium or potassium, bicarbonate, and optionally in the presence of a Crown ether [e.g. 15-Crown-5 (1,4,7,10,1 3-pentaoxacyclopentadiene) or 18 Crown-6 (1 4,710,1 3,1 6-hexaoxacyclooctadecane)] at a temperature from OOC to the reflux temperature of the reaction mixture. The production of compounds of general formula IK wherein R5a represents a group identical tq the group R5 is favoured by the use of an excess of the compound of general formula Xlil. If necessary a mixture of compounds of general formula IK wherein R5a represent a hydrogen atom and R5a represents a group identical to R5 may be separated by known methods, e.g.

crystallisation or chromatography on silica gel.

According to a further feature of the present invention, compounds of general formula I wherein R' represents a group R5, which is a group R18R19CH- wherein R15 and R'9 together with the carbon atom to which they are attached represent a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms, unsubstituted or substituted by a cyano group, a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, a carboxy group, a straight- or branched-chain alkoxycarbonyl group containing from 2 to 9 carbon atoms or one or more halogen, e.g. chlorine atoms, R2 represents a hydrogen atom and R3 is as hereinbefore defined of the general formula IL herein depicted wherein R3, R15 and R'9 as hereinbefore defined, are prepared by the reduction of the imine double bond of a compound of the general formula XIV herein depicted, wherein R3, R18 and R19 are as hereinbefore defined. Reduction of the imine group of a compound of general formula XIV may be effected with an alkali metal, e.g. sodium, boro- or cyanoboro-hydride, in the presence of a suitable inert organic solvent, for example an alkanol containing from 1 to 4 carbon atoms e.g. methanol or ethanol, or tetrahydrofuran at a temperature from laboratory temperature to the reflux temperature of the reaction mixture.

According to a further feature of the present invention, the compounds of general formula I wherein R' represents a group R5, (wherein R5 is as hereinbefore defined), R2 represents a hydrogen atom and R3 is as hereinbefore defined, i.e. compounds of the general formula IM herein depicted, wherein R3 and R5 are as hereinbefore defined, are prepared by the removal of the group R20C0- of a compound of the general formula XV herein depicted, wherein R20 represents a straight- or branched chain alkyl or alkoxy group containing from 1 to 4 carbon atoms and R3 and R5 are as hereinbefore defined.Removal of the group R20COmay be effected by selective hydrolysis, when R20 represents an alkyl group, under mild alkaline conditions or, when R20 represents an alkoxy group, e.g. t-butoxy, under mild alkaline or acidic conditions, for example by treatment with an alkali metal, e.g. sodium or potassium, hydroxide in water or a suitable inert organic or aqueous-organic solvent, for example a lower alkanol, e.g. methanol, or a mixture of water and lower alkanol, e.g. methanol, or an inorganic acid, e.g. hydrochloric acid, in water or a suitable aqueous-organic solvent, e.g. a mixture of water and a lower alkanol, e.g. methanol, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture. As will be readily apparent to those skilled in the art, when R5 in the compound of general formula XV represents an alkyl, alkenyl or alkynyl group substituted by an alkoxycarbonyl group, removal of the group R20COmay be accompanied by hydrolysis or, when a lower alkanol is present in the reaction medium, transesterification of the alkoxycarbonyl group to give respectively, a product of general formula IM wherein R5 is an alkyl, alkenyi or alkynyl group substituted by a carboxy group or wherein R5 is an alkyl, alkenyl or alkynyl group substituted by an alkoxycarbonyl group wherein the alkoxy moiety is the same as that of the lower alkanol present in the reaction medium, according to the reaction conditions used.

By the term "lower alkanol" as used in the present specification is meant an alkanol containing from 1 to 4 carbon atoms unless otherwise indicated).

According to a further feature of the present invention, the compound of general formula I wherein R1 and R2 each represent a methyl group and R3 is as hereinbefore defined, are prepared by reaction of the compound of formula IA wherein R3 is as hereinbefore defined, with formic acid in the presence of acetic acid. The reaction may be effected in the absence or presence of a suitable inert organic solvent, for example an aromatic hydrocarbon, e.g. benzene or toluene, at a temperature from OOC to the reflux temperature of the reaction mixture and, if desired, at elevated pressure.

According to a further feature of the present invention, compounds of general formula I wherein R' represents a group R5 which is a group CH2R21 wherein R2' represents a straight- or branched-chain alkyl group containing from 1 to 7 carbon atoms, unsubstituted or substituted by a cyano group, a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, or one or more halogen, e.g. chlorine, atoms, R2 represents a hydrogen atom and R3 is as hereinbefore defined, of the general formula IN herein depicted, wherein R3 and R21 as hereinbefore defined, are prepared by reduction of the carbonyl group of a compound of the general formula XVI herein depicted, wherein R3 and R21 are as hereinbefore defined.Reduction of the carbonyi group of a compound of general formula XVI may be effected with an alkali metal, e.g. sodium, boro-ethanedithiolate, in a suitable inert organic solvent, for example a lower alkanol, e.g. methanol or ethanol, or tetrahydrofuran, at a temperature from laboratory temperature up to the reflux temperature of the reaction mixture.

Compounds of general formula XIV, wherein R3, R15 and Ra9 are as hereinbefore defined, may be prepared by reaction of the compound of formula IA, wherein R3 is as hereinbefore defined, with a compound of the general formula XVII herein depicted, wherein R18 and R'9 are as hereinbefore defined. Reaction may be effected in the presence of a lower alkanol, e.g. methanol or ethanol, optidnally in the presence of an inorganic acid, e.g. hydrochloric or sulphuric acid, at a temperature from laboratory temperature up to the reflux temperature of the reaction mixture.

Compounds of general formula XV, wherein R3, R5 and R20 are as hereinbefore defined, may be prepared by the reaction of a compound of the general formula XVI II herein depicted, wherein R3 and R20 are as hereinbefore defined, or an alkali metal, e.g. sodium or potassium, derivative thereof, with a compound of the general formula XIX herein depicted, wherein R5 and X' are as hereinbefore defined.

Reaction may be effected in a suitable inert organic solvent, e.g. dichloromethane, tetrahydrofuran or dimethylformamide, at a temperature from laboratory temperature to the reflux temperature of the reaction mixture, and, when a compound of general formula XVI II is used, in the presence of a base e.g.

Triton B.

Alkali metal derivatives of compounds of general formula XVI II may be prepared in situ by the reaction of a compound of general formula XVI II wherein R3 and R20 are as hereinbefore defined, with an alkali metal, e.g. sodium or potassium, hydride, at a temperature from laboratory temperature to the reflux temperature of the reaction mixture.

Compounds of general formula XVI II, wherein R3 and R20 are as hereinbefore defined, may be prepared by the reaction of the compound of formula IA, wherein R3 is as hereinbefore defined, with a compound of the general formula XX herein depicted, wherein R20 and X are as hereinbefore defined or with a compound of the general formula XXI herein depicted, wherein R20 is as hereinbefore defined, in the absence or presence of a suitable inert organic solvent, for example a ketone, e.g. acetone, an aromatic hydrocarbon, e.g. benzene or toluene, chloroform, dichloromethane or dimethylformamide, and optionally in the presence of an acid-binding agent, for example pyridine, triethylamine or an alkali metal, e.g. sodium or potassium, carbonate or bicarbonate, at a temperature from 00 C to the reflux temperature of the reaction mixture.

Compounds of general formula XVI may be prepared by the reaction of the compound of formula IA wherein R3 is as hereinbefore defined, with a compound of the general formula XXII herein depicted, wherein R2' and X are as hereinbefore defined, or with a compound of the general formula XXIII herein depicted, wherein R2' is as hereinbefore defined. The reaction may be effected as hereinbefore described for the reaction of a compound of general formula IA with a compound of general formula XX or XXI.

Compounds of general formula XVIII, wherein R20 represents a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms, i.e. compounds of the general formula XXIV herein depicted, wherein R22 represents a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms and R3 is as hereinbefore defined, may be prepared by the reaction of the compound of the formula XXV herein depicted wherein R23 represents a phenoxy group and R3 is as hereinbefore defined, with a compound of the general formula XXVI herein depicted, wherein R22 is as hereinbefore defined.The reaction may be effected in water or a suitable inert aqueous-organic or organic solvent, for example an alkanol containing from 1 to 4 carbon atoms, e.g. ethanol, or an aromatic hydrocarbon, e.g. benzene or toluene, or which is preferably an excess of the compound of general formula XXVI, at a temperature of from ambient temperature up to the reflux temperature of the reaction mixture and, if necessary, at elevated pressure, and optionally in the presence of a base, for example an alkali metal alkoxide, e.g. of the compound of general formula XXVI.

The compound of formula XXV may be prepared by the reaction of the compound of formula IA, wherein R3 is as hereinbefore defined, with a compound of the general formula XXVII herein depicted, wherein R23 and X are as hereinbefore defined. The reaction may be effected as hereinbefore described for the reaction of the compound of formula IA with a compound of general formula XX.

According to a further feature of the present invention, compounds of general formula I wherein R1 a group R5 represented by R1 has an alkoxycarbonyl substituent containing from 2 to 9 carbon atoms and R2 represents a hydrogen atom or a group R5 which may have an alkoxycarbonyl substituent containing from 2 to 9 carbon atoms, and R3 is as hereinbefore defined, may be prepared by the transesterification of the or each alkoxycarbonyl substituent of a compound falling within the definition given immediately above with an alkanol containing from 1 to 8 carbon atoms, e.g. methanol, the alkoxy moiety of which differs from the or both alkoxy moieties of the group(s) R5 represented by R' and R2.Transesterification may be effected with an excess of the alkanol containing from 1 to 8 carbon atoms in the presence of an inorganic acid, e.g. hydrochloric acid, and optionally in the presence of water, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture.

According to a further feature of the present invention, compounds of general formula I, wherein a group R5 represented by R' has an alkoxycarbonyl substitutent containing from 2 to 9 carbon atoms and R2 represents a hydrogen atom or a group R5 which may have an alkoxycarbonyl substituent containing from 2 to 9 carbon atoms, and R3 is as hereinbefore defined, may be prepared by the esterification of a corresponding compound of formula I in which a group R5 represented by R' has a carboxy substituent and R2 represents a hydrogen atom or a group R5 which may have a carboxy substituent, with an alkanol containing from 1 to 8 carbon atoms. Esterification may be effected with the alkanol containing from 1 to 8 carbon atoms, in the presence of an esterifying agent, e.g. sulphuric acid, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture.

According to a further feature of the present invention, compounds of general formula I, wherein R' represents a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms or alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted as hereinbefore defined with exclusion of substituents selected from a cyano group, a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, a carboxy group or one or more halogen atoms R2 represents a hydrogen atom, and R3 is as hereinbefore defined, (i.e.

compounds of the general formula IP herein depicted, wherein R3 is as hereinbefore defined, Rr represents a straight- or branched-chain alkylene group containing from 1 to 8 carbon atoms or alkenylene or alkynylene group containing from 2 to 8 carbon atoms and R24 represents a straight- or branched-chain alkoxy group containing from 1 to 8 carbon atoms, an amino group unsubstituted or substituted by one or two straight- or branched-chain alkyl groups each containing from 1 to 8 carbon atoms and which, when the amino group is substituted by two alkyl groups, may be the same or different, or substituted by one or two straight- or branched-chain alkenyl or alkynyl groups containing from 2 to 8 carbon atoms and which, when the amino group is substituted by two alkenyl or alkynyl groups may be the same or different, an alkoxyamino group wherein the alkoxy moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, an alkanesulphonamido group wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, or a -Het group, wherein Het is as hereinbefore defined), may be prepared by the reaction of a compound of the general formula XXXIII herein depicted, wherein Rr and R3 are as hereinbefore defined, with a compound of the general formula XXXIV herein depicted wherein R24 is as hereinbefore defined or when R24 represents an alkanesulphonamido group, an alkali metal, e.g. sodium, salt of an alkanesulphonamide represented by general formula XXXIV.The reaction may be effected, when R24 represents an alkoxy group, in the presence of an excess of the alkanol represented by general formula XXXIV, or, when R24 represents an amino group unsubstituted or substituted by one or two alkyl, alkenyl or alkynyl groups, an alkoxyamino group, an alkanesulphonamido group or a Het group, in the presence of a suitable inert organic solvent, for example a ketone, e.g. methylethylketone, dimethylformamide or toluene, in the presence, when R24 represents an alkoxy group or an alkanesulphonamide group, of a base, for example an alkali metal, e.g. potassium, carbonate, or, when R24 represents an amino group unsubstituted or substituted or a Het group or an alkoxyamino group, in the presence of an alkali metal, e.g. potassium, carbonate, or an excess of ammonia, mono- or di-alkyl-, alkenyi- or alkynyl-amine, alkoxyamine or the heterocyclic compound represented by general formula XXXIV, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture.

Compounds of general formula XXXIII may be prepared by the reaction of a compound of general formula I wherein R1 represents a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by a carboxy group or a straight- or branchedchain alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by a carboxy group, with thionyl chloride or phosphorus oxychloride, optionally in the presence of an inert organic solvent, e.g., toluene, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture. If desired, compounds of general formula XXXII I may be prepared in situ and reacted with compounds of general formula XXXIV without previous isolation.A convenient method for preparing compounds of general formula I, wherein R' represents a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms or alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by an aminocarbonyl group substituted by one or two alkyl groups each containing from 1 to 8 carbon atoms, R2 represents a hydrogen atom, and R3 is as hereinbefore defined, comprises reacting a compound of general formula I wherein R' represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by a carboxy group or a straight- or branched-chain alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by a carboxy group, with phosphorus oxychloride and the appropriate mono- or dialkyl amine in the presence of potassium carbonate at a temperature of from laboratory temperature up to the reflux temperature of the reaction medium.

Certain compounds of general formula XXXII I may also be prepared by treating a compound of general formula I wherein R' and R2 together with the nitrogen atom to which they are attached represent a group of general formula II, wherein RC, Rd, Re, Rf, Rg, Rh and n are as hereinbefore defined, and R3 is as hereinbefore defined, with anhydrous hydrogen chloride in the presence of an inert organic solvent, e.g. chloroform at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture.

According to a furtherfeature of the present invention, compounds of general formula I, wherein R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by an alkanesulphonamidocarbonyl group wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain and R2 represents a hydrogen atom, and R3 is as hereinbefore defined, (i.e. compounds of the general formula IQ herein depicted wherein Or and R3 are as herein before defined and TO represents an alkanesulphonamido group wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branchedchain) may be prepared by the reaction of a compound of general formula i, wherein R' represents a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by an unsubstituted aminocarbonyl group or a straight- or branched-chain alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by an unsubstituted aminocarbonyl group, (i.e. a compound of general formula IP, wherein Rr and R3 are as hereinbefore defined and R24 represents an unsubstituted amino group), with an alkanesulphonylchloride, wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain. The reaction may be effected at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture and optionally in the presence of a suitable inert organic solvent, for example a ketone, e.g. methylethylketone, or toluene, and optionally in the presence of a base, for example an alkali metal, e.g. potassium, carbonate.

According to a further feature of the present invention, compounds of general formula I, wherein R' represents a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 2 to 8 carbon atoms substituted by a hydroxy group or a straight- or branched-chain alkenyl or alkynyl group containing from 3 to 8 carbon atoms substituted by a hydroxy group and R2 represents a hydrogen atom, and Era is as hereinbefore defined, (i.e. compounds of the general formula IR herein depicted wherein Era is as hereinbefore defined and RS represents a straight- or branched-chain alkylene group containing from 2 to 8 carbon atoms or a straight- or branched-chain alkenylene or alkynylene group containing from 3 to 8 carbon atoms) may be prepared by the reduction of the carboxylic acid or ester group of a compound of the general formula XXXV herein depicted wherein Ra is as hereinbefore defined, R' represents a straight- or branched-chain alkylene group containing from 1 to 7 carbon atoms or a straight- or branched-chain alkyenylene or alkynylene group containing from 2 to 7 carbon atoms, RU represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms and T' represents a hydrogen atom or, when RU represents an alkyl group, T' may also represent a group R25(C=O)-, wherein R25 represents a straight- or branched-chain alkyl or alkoxy group containing from 1 to 4 carbon atoms. When RU represents a hydrogen atom, the reduction may be effected with sodium dihydrobis-(2-methoxy-ethoxy)aluminate in the presence of a suitable inert organic solvent, for example toluene, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture. When RU represents an alkyl group, the reduction may be effected with sodium borohydride in the presence of methanol and of tertiary butanol as solvent, at the reflux temperature of the reaction mixture.

According to a further feature of the present invention, compounds of general formula I, wherein R' represents a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by a chlorine atom or a straight- or branched-chain alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by a chlorine atom, and R2 represents a hydrogen atom, and R3 is as hereinbefore defined (i.e. compounds of the general formula IS herein depicted, wherein R3 and Rr are as hereinbefore defined), may be prepared by the reaction of a compound of general formula I, wherein R' represents a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by a hydroxy group or a straight- or branched-chain alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by a hydroxy group and R2 represents a hydrogen atom, and R3 is as hereinbefore defined, with thionyl chloride, optionally in a suitable inert organic solvent, for example dichloromethane or trichloromethane, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture.

According to a further feature of the present invention, compounds of general formula l, whereln R' represents a group R5 wherein R5 represents an aikylthio group wherein the alkyl moiety contains from 1 to 4 carbon atoms and may be straight- or branched-chain, and R2 represents a hydrogen atom, and R3 is as hereinbefore defined, (i.e. compounds of the general formula IT herein depicted wherein R3 is as: hereinbefore defined and R" represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms) may be prepared by the reaction of an alkali metal, e.g. sodium or potassium, salt of the compound of formula IA, wherein R3 is as hereinbefore defined, with an alkanesulphenyl chloride, wherein the alkane moiety contains from 1 to 4 carbon atoms and may be straight- or branched-chain, for example with cooling, e.g. to OOC, in the presence of a suitable inert organic solvent, e.g. toluene, and optionally in the presence of a Crown ether, e.g. 15-Crown-5 or 18-Crown-6.

According to a further feature of the present invention, compounds of general formula I, wherein R' and R2 together with the nitrogen atom to which they are attached represent a group of general formula XXXI I, wherein RP represents a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms, and Rq is as hereinbefore defined, and R3 is as hereinbefore defined (i.e. compounds of the general formula IU herein depicted wherein R3, RV and Rq are as hereinbefore defined) may be prepared by the reaction of the compound of formula IA, wherein R3 is as hereinbefore defined with a compound of the general formula XXXVI'herein depicted, wherein RV is as herein before defined and RW represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, for example, in the presence of an acid catalyst, e.g. p-toluenesulphonic acid, optionally in the presence of a suitable inert organic solvent e.g. tetrahydrofuran or dioxan, at the reflux temperature of the reaction mixture.Reaction may be effected in the presence of a lower alkanol, e.g. methanol or ethanol, optionally in the presence of an inorganic acid, e.g., hydrochloric or sulphuric acid, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture.

According to a further feature of the present invention, compounds of general formula I, wherein R' and R2 together with the nitrogen atom to which they are attached represent a group of general formula XXXI I, wherein RP represents an amino group substituted by one or two straight- or branchedchain atkyl groups each containing from 1 to 4 carbon atoms and which may be the same or different, and Rq is as hereinbefore defined, and R3 is as hereinbefore defined, (i.e. compounds of the general formula IW herein depicted wherein RX represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms and Rq and RU are as.hereinbefore defined) may be prepared by reacting a compound of general formula I where R' and R2 together with the nitrogen atom to which they are attached represent a group of general formula XXXII, wherein RP represents a straight- or branchedchain alkoxy group containing from 1 to 4 carbon atoms and Rq is as hereinbefore defined, and R3 is as hereinbefore defined (i.e. a compound of general formula IU wherein R3, RV and Rq are as hereinbefore defined) with a mono- or di-alkylarnine wherein the alkyl moiety or moieties each contain from 1 to 4 carbon atoms and may be straight- or branched-chain and which, when the reaction is effected with a di-alkylamine, may be the same or different. The reaction may be effected in a suitable inert organic solvent, e.g. tetrahydrofuran, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture and preferably in the presence of an excess of the mono- or dialkylamine.

According to a further feature of the present invention, compounds of general formula I, wherein R' represents a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms unsubstituted or substituted in the alpha position by a straight- or branchedchain alkoxy group containing from 1 to 6 carbon atoms and R2 represents a hydrogen atom, and R3 is as hereinbefore defined, (i.e. compounds of the general formula IY herein depicted wherein R3 is as hereinbefore defined, RY represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 7 carbon atoms and T2 represents a hydrogen atom or a straight- or branchedchain alkoxy group containing from 1 to 6 carbon atoms) may be prepared by the reduction of the imine double bond of a compound of the general formula XXXVII herein depicted wherein R3, RY and T2 are as hereinbefore defined.The reduction may be effected with an alkali metal, e.g. sodium boro- or cyanoboro- hydride in the presence of a suitable inert organic solvent, for example an alkanol containing from 1 to 4 carbon atoms, e.g. methanol or ethanol or tetrahydrofuran at a temperature of from OOC up to 60CC. When the reduction of a compound in which T2 represents alkoxy is effected under mild conditions, a compound of general formula I wherein R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted in the alpha position by a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms and R2 represents a hydrogen atom and R3 is as hereinbefore defined (i.e. a compound of general formula IY wherein T2 represents an alkoxy group) is obtained, while the use of more vigorous reduction gives a compound of general formula I wherein R' represents a group R5 wherein R5 represents an unsubstituted straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms and R2 represents a hydrogen atom, and R3 is as hereinbefore defined (i.e. compounds of general formula IY wherein T2 represents a hydrogen atom). When the reduction is effected in the presence of an alkanol, the reduction may be accompanied by alcoholysis of an alkoxy group represented by T2 in general formula XXXVII, to give a product wherein R' is substituted in the alpha position by an alkoxy group corresponding to the alcohol used.

According to a further feature of the present invention, compounds of general formula I wherein R' represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 2 to 8 carbon atoms substituted by a carboxy group, a straight- or branched-chain alkoxycarbonyl group containing from 2 to 9 carbon atoms or an aminocarbonyl group unsubstituted or substituted by one or two straight- or branched-chain alkyl group each containing from 1 to 8 carbon atoms and which, when the amino carbonyl group is substituted by two alkyl groups, may be the same or different, or substituted by one or two straight- or branched-chain alkenyl or alkynyi groups each containing from 2 to 8 carbon atoms and which, when the aminocarbonyl group is substituted by two aikenyl or alkynyl groups, may be the same or different and R2 represents a hydrogen atom, and R3 is as hereinbefore defined (i.e. compounds of the general formula IZ herein depicted wherein R3 is as hereinbefore defined, RZ represents a straight- or branched-chain alkylene group containing from 2 to 8 carbon atoms, and T3 represents a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 8 carbon atoms or an amino group unsubstituted or substituted by one of two straight- or branched-chain alkyl groups each containing from 1 to 8 carbon atoms and which, when the amino group is substituted by two alkyl groups, may be the same or different or substituted by one or two straight- or branched-chain alkenyl or alkynyl groups each containing from 2 to 8 carbon atoms and which, when the amino carbonyl group is substituted by two alkenyl or alkynyl groups, may be the same or different), may be prepared by treating a compound of general formula I wherein R' and R2 together with the nitrogen atom to which are attached represent a group of general formula II, wherein RC, Rd, Re, Rf, R5, Rh and n are as hereinbefore defined, with the proviso that the group of general formula II contains from 2 to 8 carbon atoms excluding the carbon atom of the carbonyl group, and R3 is as hereinbefore defined, to effect fission of the amide group of the group of formula II with, respectively, an aqueous solution of an alkali metal, e.g. sodium or potassium, hydroxide, optionally in the presence of a lower alkanol, e.g. methanol, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture, a straight- or branched-chain alkanol containing from 1 to 8 carbon atoms in the presence of an alkali metal lower alkoxide, e.g. sodium methoxide, or ethanolic hydrogen chloride, optionally in the presence of water, art a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture, or ammonia or a mono- or dialkylamine, wherein the alkyl moieties are straight- or branched-chain and each contain from 1 to 8 carbon atoms and may, in the case of a dialkylamine, be the same or different or a mono- or di-alkenylor alkynyl-amine wherein the alkenyl or alkynyl moieties are straight- or branched-chain and each contain from 2 to 8 carbon atoms and which may, in the case of a di- alkenyl- or alkynyl amine, be the same or different, optionally in the presence of an inert organic solvent, e.g. toluene, tetrahydrofuran or dioxan, at a temperature of from laboratory temperature up to the reflux temperature of the reaction mixture.

Compounds of general formula XXXVII, wherein R3, RY and T2 are as hereinbefore defined, may be prepared by the reaction of the compound of formula IA wherein R3 is as hereinbefore defined, with a compound of the general formula XXXVIII herein depicted, wherein RY i9 as hereinbefore defined, to give a compound of general formula XXXVI I wherein T2 is a hydrogen atom, or with a compound of general formula XXXVI, wherein R" and RW are as hereinbefore defined, to give a compound of general formula XXXVII wherein T2 is an alkoxy group. The reaction may be effected under the conditions hereinbefore described for the reaction of the compound of formula IA with a compound of general formula XVII.

Compounds of general formula XXXV wherein T' represents a hydrogen atom may be prepared by procedures herein described for the preparation of compounds of general formula I wherein R' represents a group R5 wherein R5 represents an alkyl, alkenyl or alkynyl group substituted by a carboxy or alkoxycarbonyl group and R2 represents a hydrogen atom, and R3 is as hereinbefore defined.

Compounds of general formula XXXV wherein T' represents a group R25(C=O) may be prepared by the procedure herein described for the preparation of compounds of general formula XV.

According to a further feature of the present invention, compounds of general formula I wherein R' and R2, together with the nitrogen atom to which they are attached, represents a group of general formula II (wherein RC, Rd, Re, Rf, Rg, Rh and n are as hereinbefore defined) and R3 is as hereinbefore defined are prepared by the process which comprises the treatment with a base of a compound of the general formula XXVI II herein depicted, wherein RC, Rd, Re, Rf, Rg, Rh, R3, X and n are as hereinbefore defined.Treatment with a base may be suitable effected with sodium hydride in dichloromethane or dimethylsulphoxide, potassium bicarbonate in ethanol and, optionally, water, potassium carbonate in acetone and, optionally, water, triethylamine in ethanol and, optionally, water or Triton B in ethanol and, optionally, water, at a temperature from laboratory temperature up to the reflux temperature of the reaction mixture.

Compounds of general formula XXVIII are prepared by the reaction of the compound of formula IA, wherein R3 is as hereinbefore defined, with a compound of the general formula XXIX herein depicted, wherein X2 represents a chlorine or bromine atom and Rc, Rd, Re, Rf, Rg, Rh, X and n are as hereinbefore defined, and X and X2 may be the same or different, in the absence or presence of a suitable inert organic solvent, for example a ketone, e.g. acetone, an aromatic hydrocarbon, e.g.

benzene ortoluene, chloroform; dichloromethane or dimethylformamide, and optionally in the presence of an acid binding agents, for example pyridine, triethylamine or an alkali metal, e.g. sodium or potassium, carbonate or bicarbonate, at a temperature from OOC up to the reflux temperature of the reaction mixture.

it desired, the compound of general formula XXVIII may be prepared in situ by reaction of the compound of formula IA with a compound of general formula XXIX and treated with a mild base to give a compound of general formula I [wherein R and R2, together with the nitrogen atom to which they are attached, represent a group of general formula II (wherein RC, Rd, Re, Rf, Rg, Rh and n are as hereinbefore defined) and R3 is as hereinbefore defined] without isolation of the compound of general formula XXVIII.

When, in a compound of general formula XXVI II, one or both of Re and Rf represents a hydrogen atom and/or one or both of Rg and Rh represents an alkyl group containing an alpha-hydrogen atom, treatment of the aforesaid compounds of general formula XXVI II with a base may, according to the reaction conditions used, give rise, in addition to a compound of general formula I, to a compound in which the pyrazole ring carries, in the 5-position, an open-chain alkenylcarbonylamino group, (i.e. a compound of general formula I wherein R1R2N- represents an open-chain alkenylcarbonylamino group and R3 is as hereinbefore defined), by elimination of hydrogen chloride or hydrogen bromide with formation of an ethylenic double bond.For example, when in the compound of general formula XXVIII, Re is as hereinbefore defined and Rf is hydrogen, a compound of the general formula XXX herein depicted, wherein RC, Rd, Re, R9, Rh, R3 and n are as hereinbefore defined, may be obtained, in addition to a compound of general formula I by the elimination of hydrogen chloride or hydrogen bromide with the formation of an ethylenic double bond, while when, in the compound of general formula XXVIII, R5 represents an alkyl group containing an alpha-hydrogen atom and Rh represents a hydrogen atom or an alkyl group which does not contain an alpha-hydrogen atom, there may be obtained, in addition to a compound of general formula I, a compound of the general formula XXXI herein depicted, wherein RC, Rd, Re, Rf, Rh, R3 and n are as hereinbefore defined and Ri and Rk, which may be the same or different, each represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 3 carbon atoms, the total combined number of carbon atoms in Rand Rk taken together being not more than three. As will be apparent to those skilled in the art, further compounds of similar structure may be formed by elimination of hydrogen chloride or hydrogen bromide with formation of an ethylenic double bond, for example, when, in the compound of general formula XXVI II, Rh represents an alkyl group containing an alpha-hydrogen atom and Rg represents a hydrogen atom or an alkyl group which does not contain an alpha-hydrogen atom.Mixtures of compounds of general formula I and compounds in which the pyrazole ring carries, in the 5-position, an open-chain alkenylcarbonylamino group, e.g.

compounds of general formulae XXX and XXXI, thus obtained may be readily separated into their components of general formula I and, for example, formula XXX and/or XXXI by methods known per se, for example by chromatography on silica, selective solvent extraction or fractional crystallisation.

(By the term 'methods known per se' as used in the present specification is meant methods heretofore used or described in the chemical literature).

The compounds which are obtained from compounds of general formula XXVI II in which the pyrazole ring carries, in the 5-position, an open-chain alkenylcarbonylamino group, by elimination of hydrogen chloride or hydrogen bromide with formation of an ethylenic double bond, for example compounds of general formulae XXX and XXXI, wherein RC, Rd, Re, Rf, Rg, Rh, Ri, Rk, R3 and n are as hereinbefore defined, possess herbicidal properties similar to those of the compounds of general formula I.

Salts with agriculturally acceptable bases of compounds of general formula I wherein R' represents a group R5, wherein R5 represents an alkyl, alkenyl or alkynyl group substituted by a carboxy group may be prepared from the corresponding compounds of general formula I by methods known per se, for example by reacting stoichlometric quantities of the compounds of general formula I and the appropriate base, for example, an alkali metal hydroxide, carbonate or bicarbonate, an alkaline earth metal hydroxide or carbonate, ammonia or an amine (e.g. diethanolamine, triethanolamine, octyiamine, morpholine or dioctylamine), in a suitable solvent. The salts may, if necessary, be purified by recrystallisation from one, two or more suitable solvents.

As well as being useful in themselves as herbicidally active compounds, salts of compounds of general formula I may also be used in the purification of the corresponding compounds of general formula I, for example by exploitation of the solubility difference between the salts and the parent compounds in water and in organic solvents, by techniques which are well known to those skilled in the art.

The compound of formula V may be prepared by methods known per se, for example by reacting 2,3-dichloro-5-trifluoromethylpyridine with hydrazine hydrate in ethanol. Compounds of general formulae Vl, XII, XII I, XVI I, XIX, XX, XXI XXI I, XXII I, XXIX, XXXIV, XXXVI and XXXVI II may also be prepared by methods known per se.

2,3-Dichloro-5-trifluoromethylpyridine may be prepared as described in British Published Patent Specification No. 2002368A.

The following Examples and Reference Example illustrate the preparation of compounds of general formula I. Chromatography was effected on a silica column-(Merck 0.040-0.063 mm) at a pressure of 6.6 N . m-2.

EXAMPLE 3 (Preparation of Compound No. 1) Ethoxymethylenemalononitrile [2.68 g; described by Huber, J. Amer. Chem. Soc., 65,2224 (1 943)] and 3-chloro-2-hydrazino-5-trifluoromethylpyridine (4.65 g) were added to a magneticallystirred solution of sodium acetate (0.91 g) in glacial acetic acid (20 ml) at laboratory temperature. After stirring for 2 hours, a yellow solid precipitated from the clear brown solution obtained and stirring was continued for a further 1 5 hours. The mixture was then filtered.The solid obtained was washed successively with acetic acid, water, aqueous sodium bicarbonate solution and water, to give 3-chloro 5-trifluoromethylpyrid-2-yl-hydrazinomethylenemalononitrile (1.68 g), m.p. 21 2-21 50C, in the form of a yellow solid.

The 3-chloro-5-trifl uoromethylpyrid-2-yl-hydrazinomethylenema lononitri le thus obtained was then heated at reflux for 2 hours in ethoxyethanol (20 ml). The hot solution was filtered and the filtrate was cooled, diluted with water (100 ml), and filtered to give a brown solid which was crystallised from toluene (50 ml) to 5-amino-l -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole (1.58 g), m.p. 199--2000C, in the form of a cream coloured solid.

EXAMPLE 4 (Preparation of Compounds Nos. 2 and .3) Acetyl chloride (0.95 ml) was added to a stirred suspension of 5-amino-l -(3-chloro-5-trifluoro- methylpyrid-2-yl)-4-cyanopyrazole (prepared as described in Example 3: 1.0 g) in chloroform (10 ml) at OOC. A solution of pyridine (0.56 ml) in chloroform (5 ml) was then added to the reaction mixture at 0--5 OC. The reaction mixture was then warmed to laboratory temperature and allowed to stand overnight. The solution was then diluted with dichloromethane (50 ml) and washed with hydrochloric acid (2N, 50 ml) and twice with water (2x50 ml) and dried over anhydrous magnesium sulphate and evaporated to give a yellow solid.This solid was chromatographed on a silica column, eluted with dichloromethane and gradually increasing amounts of ethyl acetate (from O to 10% by volume).

Evaporation of the eluate containing the faster moving component gave 1 -(3-chloro-5-trifluoro- methylpyrid-2-yl)-4-cyano-5-diacetylaminopyrazole (0.40 g), m.p. 1 136 C, in the form of a cream coloured solid. Evaporation of the eluate containing the slower moving component gave 5 acetamido-1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole (0.30 g), m.p. 1 7 1--1 73 OC, in the form of a colourless solid.

EXAMPLE 5 (Preparation of Compound No. 4) A mixture of 5-amino-i -(3-chloro-5-trifluoromethylpyrid-2-yI)-4-cyanopyrazole (1.0 g) and powdered sodium hydride (0.17 g) in dry dioxan (25 ml) was heated at reflux for 16 hours. The reaction mixture was cooled and ethyl iodide (1.13 ml) was added. The reaction mixture was heated under reflux for 2 hours, then kept at laboratory temperature for 24 hours when further ethyl iodide (1 ml) was added. The reaction mixture was kept at laboratory temperature for a further 24 hours and then evaporated to dryness. The residue was dissolved in a mixture of dichloromethane (25 ml) and water (25 ml). The organic layer was washed with aqueous hydrochloride acid (2N; 25 ml), dried over anhydrous magnesium sulphate and evaporated to give a brown residue.

The residue was chromatographed using diethyl ether-hexane (1:2 by volume) as eluent.

Evaporation of the eluate containing the major component gave 1 -(3-chloro-5-tri-fluoromethylpyrid-2 yl)-4-cyano-5-ethylaminopyrazole (0.17 g), m.p. 82--840C, in the form of a pale yellow solid, after trituration with a mixture of diethyl ether and hexane.

EXAMPLE 6 (Preparation of Compound No. 5) A mixture of 5-amino-1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole (1.0 g) and p toluenesulphonic acid hydrate (0.02 g) in trimethylorthoformate (10 ml) was heated at reflux for 1 hour. After cooling, the reaction mixture was evaporated to dryness and the residue chromatographed using dichloromethane as eluent.

Evaporation of the eluate containing the major component gave a yellow semi-solid (0.9 g) which was recrystallised from a mixture of diethyl ether and hexane to give 1 -(3-chloro-5-trifluoromethyl- pyrid-2-yl)-4-cyano-5-methoxymethyleneaminopyrazole (0.7 g), m.p. 73--740C, in the form of a colourless solid.

EXAMPLE 7 (Preparation of Compounds No. 6 and 15) Propionyl chloride (1.14 g) was added to a stirred suspension of 5-amino-1-(3-chloro-5-trifluoro- methylpyrid-2-yl)-4-cyanopyrazole (1.0 g) in chloroform (10 ml) at OOC. A solution of pyridine (0.55 g) in chloroform (5 ml) was then added to the suspension-thusobtained over 10 minutes, with stirring, at OOC to 20C maintained by external cooling. The reaction mixture was then stirred at laboratory temperature for 1 6 hours and the solution thus obtained was evaporated to dryness. The residue was dissolved in ethanol (10 ml) and basified with aqueous ammonia (d: 0.880; 10 ml). The basified solution was heated at reflux for 3 hours and then evaporated to dryness.The residue was-dissolved in dichloromethane (100 ml), washed successively once with water, twice with 2N hydrochloric acid and twice with water, dried over anhydrous magnesium sulphate and evaporated. The brown solid thus obtained was crystallised from toluene (10 ml) to give 1 -(2-chloro-5-trifluoromethylpyrid-2-yl)-4- cyano-5-propionamidopyrazole (0.46 g), m.p.- 130-1 320C, in the form of sandy coloured powder.

By proceeding in a similar manner but replacing the propionyl chloride by valeryl chloride and basifing the reaction mixture with aqueous potassium bicarbonate in place of aqueous ammonia, there was prepared.

1-(3-Chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-pentanamidopyrazole, m.p. 89--900C, in the form of a brown solid, after crystallisation from a mixture of toluene and hexane.

EXAMPLE 7 (Preparation of Compound No. 9) Phenyl chloroformate (5.44 g) was added to a stirred suspension of 5-amino-1-(3-chloro-5trifluoromethylpyrid-2-yl)-4-cyanopyrazole (5.0 g) in dry chloroform (75 ml) at --100C. Pyridine (3.46 g) was added dropwise over 5 minutes to the reaction mixture at --100C (maintained by external cooling). The stirring was continued for 1 6 hours during which time the reaction mixture obtained laboratory temperature. The reaction mixture was then cooled to -1 00C and phenyl chloroformate (2.72-9) added followed by pyridine (1.73 g). The reaction mixture was stirred for a further 16 hours at laboratory temperature.

The clear reaction mixture was evaporated to dryness and the residue dissolved in.diethyl ether (200 ml). This solution was washed with water (3x200 ml), dried over sodium sulphate and evaporated to a yellow oily solid which was triturated with toluene (15 ml) to give 1 -(3-chloro-5 trifluoromethylpyrid-2-yl)-4-cyano-5-di(phenoxyCarbonyl)aminopyrazole (7.9 g), m.p. 191--1930C, in the form of colourless crystals.

EXAMPLE 8 (Preparation of Compounds Nos. 11, 10 and 14) 1-(3-Chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-di(phenoxyearbonyl)aminopyrazole (prepared as described in Exam;le 7; 2.4 g) was added to a solution of sodium methoxide in methanol [prepared from powdered sodium hydride (0.11 g) and anhydrous methanol (50 ml)] and the reaction mixture was heated under reflux for 1 hour.

The reaction mixture was evaporated to dryness and the residue dissolved in dichloromethane (150 ml) and water (150 ml). The organic layer was separated, washed with water (2 x 100 ml), dried over anhydrous magnesium sulphate and evaporated to give a yellow oil (1.4 g) which was crystallised from a mixture of diethyl ether (5 ml) and hexane (15 ml) to give 1-(3-chloro-5-trifluoromethylpyrid-2- yl)-4-cyano-5-methoxycarbonylaminopyrazole (0.68 g), m.p. 1 28-1 290C, in the form of colourless crystals.

By proceeding in a similar manner but replacing the methanol by the hereinafter indicated alcohol, there were prepared: 1 -(3-Chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-isopropoxycarbonylaminopyrazole, m.p.

1 19--1200C, in the form of colourless crystals, after crystallisation from a mixture of diethyl ether and hexane, from isopropanol.

1 -(3-Chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-(2-propenyloxycarbonylamino)pyrazole, m.p.

105-1 060C, in the form of colourless crystals, after crystallisation from a mixture of diethyl ether and hexane, following chromatography using dichloromethane-ethyl acetate (5:1 by volume) as eluent, from allyl alcohol.

EXAMPLE 9 (Preparation of Compound No. 12) A mixture of 5-amino-1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole (3.0 g) and (*)3- chloro-2-methylpropionyl chloride (7.3 g) in dry acetonitrile (15 ml) was heated at reflux for 5 hours.

The reaction mixture was evaporated under reduced pressure to give a solid, which was recrystallised from toluene after treatment with decolourising charcoal to give (+)5-(3-chlorn-2-methyl- propionamido)- 1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole (1.57 g), m.p. 1 51 - 1 52.50C, in the form of a fawn coloured solid.

EXAMPLE 10 (Preparation of Compounds No. 13, 7 and 8) A solution of 5-(3-chloro-2-methylpropiona mido)- 1 -(3-chloro-5-trifl uoromethylpyrid-2-yl)-4cyanopyrazole (1.40 g) in a mixture of dimethylformamide (10 ml) and dichloromethane (40 ml) was added dropwise over 1 hour to a rapidly stirred suspension of powdered sodium hydride (0.21 g) in a mixture of dimethylformamide (10 ml) and dichloromethane (40 ml) at laboratory temperature. The reaction mixture was then stirred for 2 hours. Saturated aqueous ammonium chloride solution was added to the reaction micture and then the organic layer was removed, washed with water, dried over anhydrous magnesium sulphate and evaporated to dryness. The residue was chromatographed using diethyl ether-hexane (1:2 by volume) as eluent.Evaporation of the eluate containing the faster moving component gave (+) 1 -(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-(3-methyl-2-oXo-azetidin- 1 yl)pyrazole (0.33 g), m.p. 123-1 240 C, in the form of colourless crystals.

By proceeding in a similar manner but replacing the acetyl chloride by the hereinafter indicated acid chloride, there were prepared: 1-(3-Chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-dichloroacetamidopyrazole, m.p. 1 65- 1 660C, in the form of a buff-coloured solid, after crystallisation from a mixture of toluene and hexane, from dichloroacetyl chloride.

1 -(3-Chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-succi nimidopyrazole, m.p. 200-201 OC, in the form of a buff-coloured solid, after crystallisation from a mixture of toluene and hexane, from succinyl chloride.

REFERENCE EXAMPLE 1 3-Chloro-2-hydrazino-5-trifluoromethylpyridine, used as a starting material in Example 3 was prepared as follows:- 2,3-Dichloro-5-trifluoromethylpyridine (10.37 g; described in British Published Patent Specification GB 2,002,368A) was added to a solution of hydrazine hydrate (99100% w/w 7.5 ml) in ethanol (50 ml) and the mixture heated at reflux for 24 hours. The reaction mixture was then cooled and evaporated to dryness and the residue was recrystallised frbm ethanol (25 ml) to give 3-chloro-2hydrazino-5-trifluoromethylpyridine (4.85 g), m.p. 88-900C, in the form of a grey solid. A sample of this material was recrystallised from n-hexane to give the 3-chloro-2-hydrazino-5-trifluoromethylpyridine, m.p. 870C, in the form of colourless crystals.

The various Formulae referred to in the present specification are as follows:-

RVCHO XXXVIII

Claims

1. N-Pyridylpyrazole derivatives of the general formula:

wherein R1 represents (i) a hydrogen atom, (ii) and R4C(=0)-- group, wherein R4 represents a hydrogen atom, a straight- or branched-chain alkyl group containing from 1 to 7 carbon atoms, a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms or a straight- or branched-chain alkenyloxy group containing 3 or 4 carbon atoms, alkyl and alkoxy groups within the definition of R4 being unsubstituted or substituted by a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms, a straight- or branched-chain alkoxycarbonyl group containing from 2 to 8 carbon atoms, or one or more halogen atoms, or R4 represents a cycloalkyl group containing from 3 to 6 carbon atoms unsubstituted or substituted by a method or ethyl group, or R4 represents a phenoxy group, (iii) a group R5, wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms or a straight- or branched-chain alkenyl or alkynyl group containing from 2 to 8 carbon atoms, alkyl, alkenyl and alkynyl groups represented by the symbol R5 being unsubstituted or substituted by a cyano group, a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, a carboxy group, a straight- or branched-chain alkoxycarbonyl group containing from 2 to 9 carbon atoms, an aminocarbonyl group unsubstituted or substituted by one or two straight- or branched-chain alkyl groups containing from 1 to 8 carbon atoms and which, when the aminocarbonyl group is substituted by two alkyl groups, may be the same or different, or substituted by one or two straight- or branched-chain alkenyl or alkynyl groups containing from 2 to 8 carbon atoms and which, when the aminocarbonyl group is substituted by two alkenyl or alkynyl groups, may be the same or different, an alkoxyaminocarbonyl group, wherein the alkoxy moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, an alkanesulphonamidocarbonyl group wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, a -C(=O)Het group, wherein Het represents a saturated, nitrogen-containing heterocyclic group having from 3 to 7 atoms in the ring including up to two additional heteroatoms selected from oxygen, nitrogen and sulphur, and linked to the -C(=O)- group of the groupC(=O)Het by the nitrogen atom, or one or more halogen atoms, or R5 represents a cycloalkyl group containing from 3 to 6 carbon atoms unsubstituted or substituted by one or more straight- or branched-chain lower alkyl groups containing from 1 to 4 carbon atoms, R2 represents (i) when R1 represents a hydrogen atom, a hydrogen atom, (ii) when R' represents an R4C(= group (wherein R4 is as hereinbefore defined), a hydrogen atom or an R4(= group wherein R4 is as hereinbefore defined, (iii) when R1 represents a group R5 (wherein R5 is as hereinbefore defined), R2 represents a hydrogen atom or a group within the definition of R5 as hereinbefore defined, or R1 and R2 together represent CO(CRaRb)mCO, wherein Ra and Rb, which may be the same or different, each represent a hydrogen atom or a straightor branched-chain alkyl group containing from 1 to 4 carbon atoms and m represents 2 or 3 or R1 and R2, together with the nitrogen atom to which they are attached represent a group of the general formula:

wherein RC, Rd, Re, Rf, Rg and Rh, which may be the same or different, each represent a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 6 carbon atoms and n represents 0, 1 or 2, and wherein, when n represents 1 or2, RC and Rd of the portions [(RC)C(Rd)]~ and ~[(RC~)C(Rd)]2 of the group of general formula II herein depicted, may be the same or different, or R1 represents an alkyl thio group wherein the alkyl moiety contains from 1 to 4 carbon atoms and may be straight- or branched-chain and R2 represents a hydrogen atom; or R1 and R2 together with the nitrogen atom to which they are attached represent a group of the general formula

wherein RP represents a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms or an amino group substituted by one or two straight- or branched-chain alkyl groups each containing from 1 to 4 carbon atoms, which, when the amino group is substituted by two alkyl groups, may be the same, or different, and Rq represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms and R3 represents a group of the general formula::

wherein R6 represents a chlorine atom, and, when R5 represents an alkyl, alkenyl or alkynyl group substituted by a carboxy group, salts thereof with agriculturally acceptable bases,

2. N-Pyridylpyrazole derivatives according to claim 1, wherein R1 represents an R4C(=O)- group, wherein R4 represents a straight- or branched-chain alkyl group containing from 1 to 7 carbon atoms or straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms substituted by one or more chlorine atoms and R2 and R3 are as defined in claim 1.

3. N-Pyridylpyrazole derivatives according to claim 1, wherein R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms or straight- or branched-chain alkenyl or alkynyl group containing from 2 to 8 carbon atoms, unsubstituted or substituted as defined in claim 1 and R2 and R3 are as defined in claim 1.

4. N-Pyridylpyrazole derivatives according to claim 1, wherein R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms or straight- or branched-chain alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by one or more chlorine atoms and R2 and R3 are as defined in claim 1.

5. N-Pyridylpyrazole derivatives according to claim 1, wherein R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms or straight- or branched-chain alkenyl or alkynyl group containing from 2 to 4 carbon atoms unsubstituted or substituted as defined in claim 1 or 4.

6. 5-Amino-4-cyano- 1 -(3-chloro-5-trifluoromethylpyrid-2-yl)pyrazole, 1 -(3-chloro-5-trifluoro- methylpyrid-2-yl)-4-cyano-5-diacetylaminopyrazole, 5-acetamido- 1 -(3-chloro-5-trifluoromethylpyrid 2-yl)-4-cyanopyrazole, 1 -(3-chloro-5-trifluoromethylpyrid-2-yI)-4-cyano-5-ethyla minopyrazole, 1 -(3 chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-methoxymethyleneaminopyrazole, 1 -(3-chloro-5- trifluoromethylpyrid-2-yl)-4-cyano-5-propionamidopyrazole, 1 -(3-chloro-5-trifl uoromethylpyrid-2-yl)- 4-cyano-5-dichloroacetamidopyrazoie,1-(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5- succinimidopyrazole, 1 -(3-chloro-5-trifluoromethylpyrid-2-yI)-4-cyano-5-di(phenoxycarbonyl)amino- pyrazole, 1 -(3-chloro-5-trifiuoromethylpyrid-2-yl)-4-cyano-5-isopropoxyCarbonyla minopyrazole, 1 -(3chloro-5-trifluoromethylpyrid-2-yl)-4-cyano-5-methoxycarbonylaminopyrazole, 5-(3-chloro-2-methyl- propionamido)-1-(3-chloro-5-trifluoromethylpyrid-2-yl)-4-cyanopyrazole, 1-(3-chloro-5-trifluoro- methylpyrid-2-yl)-4-cyano-5-(3-methyl-2-oxo-azetidin- 1 -yl)pyrazole. 1 -(3-chloro-5-trifluoromethyl pyrid-2-yl)-4-cyano-5-(2-propenyloxycarbonylamino)pyrazole, and 1 -(3-chloro-5-trifluoromethyl- pyrid-2-yl)-4-cyano-5-pentanamidopyrazole.

7. A process for the preparation of a compound of general formula I depicted in claim 1, wherein R1, R2 and R3 are as defined in claim 1, which comprises: (A) when R1 and R2 each represent a hydrogen atom and R3 is as defined in claim 1 , the cyclisation of the compound of the formula:

wherein R3 is as defined in claim 1, (B) when R1 and R2 each represent a hydrogen atom and R3 is as defined in claim 1, the reaction of the compound of the formula:: R3NHNH2 V wherein R3 is as defined in claim 1, with a compound of the general formula

wherein R7 represents a straight- or branched-chain aikyiradical containing from 1 to 4 carbon atoms, (C) when R1 represents an R5C(=O)- group, wherein R5 has the meanings specified for R4 in claim 1 except for the hydrogen atom, R2 represents a hydrogen atom or an R8C(=O)- group, wherein R8 is as hereinbefore defined, which is identical to the group R8C(=0) represented by R1, and R3 is as defined in claim 1, the reaction of the compound of the formula::

wherein R3 is as defined in claim 1, or an alkali metal derivative thereof, with a compound of the general formula: R8COX VII wherein X represents a chlorine or bromine atom and R8 is as hereinbefore defined, or with a compound of the general formula (R8C0)20 VIII wherein R8 is as hereinbefore defined, (D) when R1 represents an R4eC(=O) group, wherein R4a represents a hydrogen atom, R2 represents a hydrogen atom and R3 is as defined in claim 1, the reaction of a compound of general formula IA herein depicted in (C), wherein R3 is as defined in claim 1, with formic acid, (E) when R1 represents an R4aC(=O)-- group, wherein R4a represents a hydrogen atom, R2 represents a hydrogen atom or an R4aC(=O) group, wherein R4" represents a hydrogen atom, and R3 is as defined in claim 1, the reaction of the compound of formula IA herein depicted in (C), wherein R3 is as defined in claim 1, with formylacetic anhydride, (F) when R1 represents an R4C(-O)-, wherein R4 is as defined in claim 1, R2 represents a hydrogen atom and R3 is as defined in claim 1, the selective removal by hydrolysis under mild conditions to convert to a hydrogen atom one of the groups R4C(=O)- of a compound of general formula I depicted in claim, wherein R1 and R2 each represent an R4C(=O)- group, wherein R3 and R4 are as hereinbefore defined.

(G) when R' represents an R4bC(=O)group, wherein R4b represents a straight- or branchedchain alkoxy group containing from 1 to 4 carbon atoms as defined for R4 in claim 1, R2 represents a hydrogen atom and R3 is as defined in claim 1, the reaction of a compound of the general formula

wherein R15 represents a group R18C(=O)-, wherein R16 represents astraight- or branched-chain alkoxy group containing from 1 to 4 carbor! atoms unsubstituted or substituted by an alkoxy group containing from 1 to 4 carbon atoms, an alkoxycarbonyl group containing from 2 to 8 carbon atoms or one or more halogen atoms, or R16 represents a phenoxy group, with a compound of the general formula:: R'40H IX wherein R'4 is as hereinbefore defined for R4b, to replace one of the groups represented by the symbol R'5 by a hydrogen atom, to replace the other group represented by the symbol R15 by a group R14C(=O)-, wherein R4 is as hereinbefore defined, when R15 represents a group R16C(=O)-, wherein R16 represents a phenoxy group, and, if desired to replace the other group represented by the symbol R15 by another group R14C(=O)- when R15 represents a group R16(=O)-, wherein R16 represents a group within the definition of R14, (H) when R1 represents an R4C(=O)- group, wherein R4 is as defined in claim 1, R2 represents an R4C(=0)- group, wherein R4 is as defined in claim 1, which may be the same as or different to, the R4C(=O)- group represented by the symbol R', and R3 is as defined in claim 1, the reaction of an alkali metal derivative of a compound of the general formula:

wherein R12 represents a group R4C(=0)-, wherein R4 is as defined in claim 1, and R3 is as defined in claim 1, with formic acid, formylacetic anhydride or a compound of general formula VII depicted in (C), wherein R8 and X are as defined in (C), (I) when R1 and R2 together represent CO(CRSRb)mCO, wherein Ra, Rb and m are as defined in claim 1, and R3 is as defined in claim 1, the reaction of the compound of formula IA depicted in (C), wherein R3 is as defined in claim 1, with a compound of the general formula: XOC(CRSRb)mCOX X wherein Ra, Rb and m are as defined in claim 1 and X is as defined in (C), or with a compound of general formula:

wherein Ra, Rb and m are as defined in claim 1, (J) when R1 represents a group R5, wherein R5 is as defined in claim 1, R2 represents a hydrogen atom or a group within the definition of R5 as defined in claim 1, and R3 is as defined in claim 1 , the reaction of a compound of the general formula::

wherein R'7 represents a hydrogen atom or a group within the definition of R5 as defined in claim 1, R18 represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, and R5 is as defined in claim 1, with a compound of general formula V depicted in (A), wherein R3 is as defined in claim 1, (K) when R' represents a group R5, wherein R5 is as defined in claim 1, R3 is as defined in claim 1, and R2 represents a hydrogen atom or a group identical to the group R5 represented by the symbol R', the reaction of the compound of formula l(A) depicted in (C), wherein R3 is as defined in claim 1 or an alkali metal derivative thereof, with one or two molar proportions of a compound of the general formula:: R5X' XIII wherein R5 is as defined in claim 1 and X' represents a chlorine, bromine or iodine atom.

(L) when R' represents a group R5 which is a group R18R19CH-, wherein R18 and R'9 together with the carbon atom to which they are attached represent a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms, unsubstituted or substituted by a cyano group, a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, a carboxy group, a straight- or branched-chain alkoxy carbonyl group containing from 2 to 9 carbon atoms or one or more halogen atoms and R2 represents a hydrogen atom, and R3 is as defined in claim 1, the reduction of the imine double bond of a compound of the general formula::

wherein R3 is as defined in claim 1 and R18 and R'9 are as hereinbefore defined.

(M) when R1 represents a group R5, wherein R5 is as defined in claim 1, R2 represents a hydrogen atom, and R3 is as defined in claim 1, the removal of the group R20C0- of a compound of the general formula:

wherein R3 and R5 are as defined in claim 1 and R20 represents a straight- or branched-chain alkyl or alkoxy group containing from 1 to 4 carbon atoms, (N) when R1 and R2 each represent a methyl group and R3 is as defined in claim 1 , the reaction of the compound of formula IA depicted in (C), wherein R3 is as defined in claim 1, with formic acid in the presence of acetic acid, (0) when R1 represents a group R5 which is a group CH2R21 wherein R21 represents a straight- or branched-chain alkyl group containing from 1 to 7 carbon atoms unsubstituted or substituted by a cyano group, a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, or one or more halogen atoms, and R2 represents a hydrogen atom, and R3-is as defined in claim 1 , the reduction of the carbonyl group of a compound of the general formula#

wherein R3 and R21 are as hereinbefore defined.

(P) when a group R5 represented by R' has an alkoxycarbonyl substituent containing from 2 to 9 carbon atoms and R2 represents a hydrogen atom or a group R5 which may have an alkoxycarbonyl substituent containing from 2 to 9 carbon atoms, transesterifying the or each alkoxycarbonyl substituent of a compound falling within the definition given immediatley above with an alkanol containing from 1 to 8 carbon atoms, the alkoxy moiety of which differs from the or both alkoxy moieties of the group(s) R6 represented by R1 and R2, (Q) when a group R5 represented by R1 has an alkoxycarbonyl substituent containing from 2 to 9 carbon atoms, and R2 represents a hydrogen atom or a group R5 which may have. an alkoxycarbonyl substituent containing from 2 to 9 carbon atoms, esterifying a corresponding compound df formula I depicted in claim 1 in which a group R5 represented by R' has a carboxy substituent and R2 represents a hydrogen atom or a group R5 which may have a carboxy substituent, and R3 is as defined in claim 1, with an alkanol containing from 1 to 8 carbon atoms, (R) when R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms or alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted as defined in claim 1 with the exclusion of-substituents selected from a cyano group, a hydroxy group, a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, a carboxy group and one or more halogen atoms and R2 represents a hydrogen atom, and R3 is. as defined in claim 1, the reaction of a compound of the general formula:

wherein R3 is as defined in claim 1 and Rr represents a straight- or branched-chain alkylene group containing from 1 to 8 carbon atoms or a straight- or branched-chain alkenylene or alkynylene group containing from 2 to 8 carbon atoms, with a compound of the general formula:: R24~H XXXIV wherein R24 represents a straight- or branched-chain alkoxy group containing from 1 to 8 carbon atoms, an amino group unsubstituted or substituted by one or two straight- or branched-chain alkyl groups containing from 1 to 8 carbon atoms and which, when the amino group is substituted by two alkyl groups, may be the same or different, or substituted by one or two straight- or branched-chain alkenyl or alkynyl groups containing from 2 to 8 carbon atoms and which, when the amino group is substituted by two alkenyl or alkynyl groups, may be the same or different, an alkoxyamino group wherein the alkoxy moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, an alkanesulphonamido group wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, or a Het group as defined in claim 1, or when R24 represents an alkanesulphonamido group, an alkali metal salt of an alkanesulphonamide represented by general formula XXXIV, (S) when R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by an alkanesulphonamidocarbonyl group wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain and R2 represents a hydrogen atom, and R3 is as defined in claim 1 , the reaction of a compound of general formula I depicted in claim 1, wherein R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by an unsubstituted aminocarbonyl group or a straight- or branched-chain alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by an unsubstituted aminocarbonyl group, and R2 represents a hydrogen atom, and R3 is as defined in claim 1, with an alkanesulphonyl chloride, wherein the alkane moiety contains from 1 to 8 carbon atoms and may be straight- or branched-chain, (T) when R' represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 2 to 8 carbon atoms substituted by a hydroxy group or a straight- or branched-chain alkenyl or alkynyl group containing from 3 to 8 carbon atoms substituted by a hydroxy group and R2 represents a hydrogen atom, and R3 is as defined in claim 1, the reduction of the carboxylic acid or ester group of a compound of the general formula:

wherein R3 is as defined in claim, Rt represents a straight- or branched-chain alkylene group containing from 1 to 7 carbon atoms or a straight- or branched-chain alkenylene or alkynylene group containing from 2 to 7 carbon atoms, RU represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms and T' represents a hydrogen atom or, when R" represents an alkyl group, T' may also represent a group R25(C=O)-, wherein R25 represents a straight- or branchedchain alkyl or alkoxy group containing from 1 to 4 carbon atoms, (U) when R' represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by a chlorine atom or a straight- or branchedchain alkenyl or alkynyl group containing from 2 to 8 carbon atoms substituted by a chlorine atom and R2 represents a hydrogen atom, and R3 is as defined in claim 1, the reaction of a compound of general formula I depicted in claim 1 , wherein R' represents a straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms substituted by a hydroxy group or a straight- or branched-chain alkenyi or alkynyl group containing from 2 to 8 carbon atoms substituted by a hydroxy group, and R2 represents a hydrogen atom, and R3 is as defined in claim 1 , with thionyl chloride, (V) when R1 represents a group R5 wherein R5 represents an alkyithio group wherein the alkyl moiety contains from 1 to 4 carbon atoms and may be straight- or branched-chain, and R2 represents a hydrogen atom and R3 is as defined in claim 1, reacting an alkali metal salt of the compound of formula IA depicted in (C), wherein R3 is as defined in claim 1, with an alkanesulphenyl chloride, wherein the alkane moiety contains from 1 to 4 carbon atoms and may be straight- or branched-chain, (W) when R' and R2 together with the nitrogen atom towhich they are attached represent a group of general formula XXXI I depicted in claim 1, wherein RP represents a straight- or branchedchain alkoxy group containing from 1 to 4 carbon atoms, and Rq is as defined in claim 1, and R3 is as defined in claim 1, the reaction of the compound of general formula IA depicted in (C), wherein R3 is as defined in claim 1, with a compound of the general formula RWC(ORV)a XXXVI wherein RV represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms and RW represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, (X) when R' and R2 together with the nitrogen atom to which they are attached represent a group of general formula XXXII depicted in claim 1 , wherein RP represents an amino group substituted by one or two straight- or branched-chain alkyl groups each containing from 1 to 4 carbon atoms and which may be the same or different, and R9 is as defined in claim 1, and R3 is as defined in claim 1, the reaction of a compound of general formula I depicted in claim 1 , wherein R' and R2 together with the nitrogen atom to which they are attached represents a group of general formula XXXII depicted in claim 1, wherein RP represents a straight- or branched-chain alkoxy group containing from 1 to 4 carbon atoms, and R9 is as defined in claim 1, and R3 is as defined in claim 1, with a mono- or dialkylamine wherein the alkyl moiety or moieties each contain from 1 to 4 carbon atoms and may be straight- or branched-chain, and which, when the reaction is effected with a di-alkylamine, may be the same or different, (Y) when R' represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 2 to 8 carbon atoms unsubstituted or substituted in the alpha position by a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, and R2 represents a hydrogen atom, and R3 is as defined in claim 1, the reduction of the imine double bond of a compound of the general formula::

wherein B is as defined in claim 1, RV represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 7 carbon atoms and T2 represents a hydrogen atom or a straight- or branched-chain alkoxy group containing from 1 to 6 carbon atoms, (Z) when R1 represents a group R5 wherein R5 represents a straight- or branched-chain alkyl group containing from 2 to 8 carbon atoms substituted by a carboxy group, a straight- or branched-chain alkoxycarbonyl group containing from 2 to 9 carbon atoms or an aminocarbonyl group unsubstituted or substituted by one or two straight- or branched-chain alkyl groups each containing from 1 to 8 carbon atoms and which, when the aminocarbonyl group is substituted by two alkyl groups, may be the same or different, or substituted by one or two straight- or branched-chain alkenyl or alkynyl groups each containing from 2 to 8 carbon atoms and which, when the amino carbonyl group is substituted by two alkenyl or alkynyl groups, may be the same or different, and R2 represents a hydrogen atom, and R3 is as defined in claim 1, the treatment of a compound of general formula I depicted in claim 1, wherein R and R2 together with the nitrogen atom to which they are attached represent a group of general formula II depicted in claim 1, wherein RC, Rd, Re, Rf, Rg, Rh and n are as defined in claim 1, with the proviso that the group of general formula II contains from 2 to 8 carbon atoms, excluding the carbon atom of the carbonyl group, and R3 is as defined in claim 1, to effect fission of the amide group of the group of general formula II, with, respectively, an aqueous solution of an alkali metal hydroxide, a straight- or branched-chain alkanol containing from 1 to 8 carbon.atoms in the presence of an alkali metal lower alkoxide or ethanolic hydrogen chloride, or ammonia or a mono- or di-alkylamine, wherein the alkyl moieties are straight- or branched-chain and each contain from 1 to 8 carbon atoms and which may, in the case of a dialkylamine, be the same or different, or a mono- or di-alkenyl- or alkynylamine, wherein the alkenyl or alkynyl moieties are straight- or branched-chain and each contain from 2 to 8 carbon atoms and which may, in the case of a di-alkenyl- or alkynyl- amine, be the same or different, (AA) when R1 and R2 together with the nitrogen atom to which they are attached represent a group of general formula II depicted in claim 1 wherein RC, Rd, Re, Rf, R9, Rh and n are as defined in claim 1 and R3 is as defined in claim 1, the treatment of a compound of the general formula :

wherein Rc, Rd, Re, Rf, Rg, Rh and R3 are as defined in claim 1 and X represents a chlorine or bromine atom, with a base.

8. Process according to claim 7 followed by the step of converting by methods known per se an N-pyridylpyrazole derivative of general formula I depicted in claim 1 wherein one or each of the groups represented by R1 and R2 has a carboxy substituent and R3 is as defined in claim 1, into a salt thereof with an agriculturally acceptable base.

9. Process for the preparation of N-pyridylpyrazole derivatives of general formula I depicted in claim 1, wherein R1, R2 and R3 are as defined in claim 1, substantially as hereinbefore described, with especial reference to Example 3, 4, 5, 6, 7, 8, 9 or 10.

10. N-pyridylpyrazole derivatives of general formula I depicted in claim 1 wherein R1, R2 and R3 are as defined in claim 1 or when appropriate salts thereof with agriculturally acceptable bases, when prepared by the process claimed in any one claims 7 to 9.

11. A herbicidal composition which comprises, as active ingredient, at least one Npyridylpyrazole derivative of general formula I depicted in claim 1, wherein R1, R2 and R3 are as defined in claim 1, in association with one or more compatible herbicidally-acceptable diluents or carriers and/or surface active agents.

1 2. A herbicidal composition according to claim 11 which contains from 0.05 to 90% by weight of N-pyridylpyrazole derivative(s).

13. A herbicidal composition according to claim 11 or 12 which contains from 0.05 to 25% of surface-active agent.

1 4. A herbicidal composition according to claim 11 or 12 which contains from 0.05 to 10% of surface-active agent.

1 5. A herbicidal composition according to any one of claims 11 to 14 in the form of dusts, granules or wettable powders.

1 6. A herbicidal composition according to any one of claims 11 to 14 in the form of aqueous, organic or aqueous-organic solutions, suspensions or emulsions.

1 7. A herbicidal composition according to any one of claims 11 to 14 and 1 6 in which the herbicidally-acceptable diluent is water.

1 8. A herbicidal composition according to any one of claims 11 to 17 which contains one or more other pesticidally-active (including herbicidally-active) compounds.

19. A herbicidal composition according to any one of claims 1 I to 18 in which the Npyridylpyrazole derivative(s) incorporated in the compositions is a compound claimed in any one of claims 2 to 6.

20. A herbicidal composition according to claim 11 substantially as hereinbefore described with especial reference to Example 1 or 2.

21. A method of controlling the growth of weeds at a locus which comprises applying to the locus a herbicidally effective amount of an N-pyridylpyrazole derivative of general formula I depicted in claim 1, wherein R', R2 and R3 are as defined in claim 1, in a herbicidal composition as claimed in any one of claims 11 to 20.

22. A method according to claim 21 in which the weeds are broad-leafed weeds, such as those specifically mentioned in the Description.

23. A method according to claim 21 in which the weeds are grass weeds, such as those specifically mentioned in the Description.

24. A method according to claim 21, 22 or 23 wherein the N-phenylpyrazole derivative is applied pre- or post-emergence of the weeds.

25. A method according to claim 21 or 22 wherein the N-phenylpyrazole derivative is applied post-emergence of the weeds.

26. A method according to any one of claims 21 to 25 in which the herbicidal composition is applied to an area used, or to be used, for growing crops.

27. A method according to claim 26 in which the herbicidal composition is applied to a cropgrowing area at a rate sufficient to control the growth of weeds without causing substantial permanent damage to the drop.

28. A method according to any one of claims 21 to 25 in which the N-phenylpyrazole derivative is applied at a rate between 0.01 kg and 10 kg per hectare.

29. A method according to claim 26, 27 or 28 in which the crop is a cereal, soya beans, field or dwarf beans, peas, lucerne, cotton, peanuts, flax, onions, carrots, cabbage, oilseed rape, sunflower, sugar beet, or permanent or sown grassland.

30. A method according to claim 26, 27 or 28 in which the crop is wheat, barley, oats, maize or rice.

31. A method according to claim 29 or 30 in which the fierbicidal composition is applied for the control of broad-leafed weeds in an area used for growing a cereal crop before or after emergence of both the crop and weeds.

32. A method according to claim 31 in which the herbicidal composition is applied postemergence of the broad-leafed weeds.

33. A method according to any one of claims 26, 27, 29, 30, 31 or 32 in which the N-pyridylpyrazole derivative is applied at a rate between 0.1 kg and 4.0 kg per hectare.

34. A method according to any one of claims 26, 27, 29, 30, 31 or 32 in which the Npyridylpyrazole derivative is applied at a rate between 0.01 kg and 4.0 kg per hectare.

35. A method according to any one claims 21 to 34 in which the N-pyridylpyrazole derivative is a compound claimed in any one of claims 2 to 6.

36. A method of controlling the growth of weeds at a locus according to claim 21 substantially as hereinbefore described.

37. 3-Chloro-5-trifluoromethylpyrid-2-ylhydriazinomethylenemalononitrile.

38. Compounds of general formula I depicted in claim 1, wherein R1R2N- represents an openchain alkyenylcarbonylamino group and R3 is as defined in claim 1.

39. Compounds of the general formula:

wherein Rc, Rd, Re, R5, Rh and n are as defined in claim 1 and R3 is as defined in claim 1.

40. Compounds of the -general formula:--

wherein RC, Rd, Re, Rf, Rh and n are as defined in claim 1, Rk and RJ, which may be the same or different, each represent a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 3 carbon atoms, the combined total number of carbon atoms in Rk and R' taken together being not more than three, and R3 is as defined in claim 1.