NL8800037A - PREPARATION AND NITRATION OF N-ALKYL-3,4-XYLIDINES AND HERBICIDE PREPARATIONS OF NITRO-N-ALKYL-3,4-XYLIDINES. - Google Patents

Description

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Preparation and nitration of N-alkyl-3,4-xylidines and herbicidal preparations of nitro-N-alkyl-3,4-xylidines.

The invention relates to a process for the preparation of new N-alkyl-3,4-xylidines and to their use as herbicides as such or after nitration. The invention further relates to a process for the nitration of these xylidines. The new compounds are illustrated by formula 1 of the formula sheet, wherein H.1 is a sec.butyl, 1-methylbutyl or 1-ethylpropyl group and R2 and 10 are each a hydrogen atom or a group with the proviso that R2 and r3 are not both are a nitro group. As mentioned above, the invention also relates to the use of some compounds according to formula 1 for controlling undesired plant species, namely the mononitro compounds. They can be used to control a wide variety of undesirable monocotyledonous and dicotyledonous plants. They exhibit herbicidal activity both before and after the emergence of the plants and can be applied to the foliage of the unwanted plant or to the soil containing the seeds, preferably in solid or liquid preparations with a known horticultural additive such as a dispersant or surfactant.

The herbicidal compositions according to the invention contain as active substance a compound of the formula 1, wherein R 2 or R 2 is nitro, in an amount which, when administered to the foliage of undesired plant species or to the soil containing the seeds of the undesired plant species. contains a herbicidal effect. Control is usually achieved by administering one or more of the active ingredients in an amount of about 1-25 kg / ha.

Solid formulations that can be used include powders, powder concentrates and granular products. For administration in liquid form 30, the product is usually first prepared as a wettable powder containing 25-95% of the active compound, as well as 4-70% by weight of a finely divided diluent such as kaolin, attapulgus clay, silica, pumice, talc or diatomaceous earth. and 1-5 wt.% of a dispersant such as an alkali metal salt of naphthalene sulfonic acid or alkali metal lignosulfonate. The composition may also contain from about 1 to 5% by weight of a surfactant, such as sodium N-methyl-N-oloyl taurate, alkylphenoxy polyoxyethylene ethanol and sorbitan fatty acid esters. The wettable powders are usually dispersed in water for administration as a liquid spray.

In addition to their direct use as herbicides, the new .8800037 2% compounds of formula 1 are unexpectedly useful as intermediates in the preparation of dinitroanilines, such as N-sec, butyl-2,6-dinitro-3,4-xylidine; N- (1-ethylpropyl) -2,6-dinitro-3,4-xylidine and N- (1-methylbutyl) -2,6-dinitro-3-4-xylidine.

It was known to prepare these dinitro compounds via a 1-substituted nucleophilic replacement of a 1-substituted 2,6-dinitro-3,4-xylene using amine to replace, for example, a 1-chloro group.

In the method of the invention, nitro groups are introduced at the ortho position relative to the alkylamino group of a 3,4-xylidine. This route has several unexpected benefits.

The first advantage concerns the easy availability of the starting materials. The starting material is always o-xylene that is nitrated or chlorinated. In one case, a mixture of 3-nitro-o-xy-15-lene and 4-nitro-o-xylene is formed, and in the other, a mixture of 3-chloro-o-xylene and 4-chloro-o-xylene. In the case of the nitro compounds, the ring isomers are easy to separate with conventional distillation equipment, while the separation of 4-chloro-o-xylene from its ring isomer can be accomplished by distillation only with great difficulty due to the slight difference in boiling points of the isomers. The second advantage of the process of the invention is that the alkylamino substituent in the 4-position of the o-xylene ring system is highly ortho-directing to the nitration reactions in contrast to its 4-chlorine counterpart which also causes substitution at the meta site. This drawback is exacerbated by the fact that part of the 3,4-dimethyl-2,6-dinitrochlorobenzene formed forms a eutectic composition with its ring isomers so that the yield of the desired compound obtained by fractional crystallization is further reduced.

According to the invention, there is further provided a new process for the preparation of compounds of formula 1 of the formula sheet, wherein R 1 is a sec-butyl, 1-methylbutyl or 1-ethylpropyl group and R 2 and R 3 are hydrogen or nitro under provided that R 2 and R 3 are not both hydrogen, by reacting concentrated nitric acid with a compound of formula 1, wherein R 1, R 2 and R 3 have the above meanings, provided that R 2 and R 3 are not both a nitro group.

If it is desired to prepare N-alkyl-2,6-dinitro-3,4-xylidines from the non-nitrated xylidines, the nitration can be performed in a single step by reacting the xylidine with 5 to 20 moles eq. HNO3.

.8800037 3 #

Optionally, this process can be carried out in two stages, first forming an orthonitroxylidine which is then converted to the 2,6-di-nitro compound.

Nitration can be performed with conventional equipment and with known nitrants, such as concentrated nitric acid.

In the case of the one-step dinitration of the non-nitrated N-alkyl-3,4-xylidines or the mononitration of the N-alkyl-ortho-nitro-3,4-xyl-lidines, the nitration is preferably carried out with concentrated nitric acid, optionally in solution in a solvent such as dichloro-10 ethane. The reaction is preferably conducted at a low temperature, usually between -10 ° and + 10 ° C using a large excess of nitric acid. Preferably, the molar ratio of acid to xylidine is kept at about 15: 1.

If it is desired to obtain the N- (alkyl) -mononitro-3,4-xylidine, the appropriate N- (alkyl) -3,4-xylidine is treated with a stoichiometric amount or small excess of concentrated nitric acid, at preferably in the presence of concentrated sulfuric acid. This reaction is preferably conducted in the presence of a solvent, such as dichloroethane, at a temperature between about 5 and 35 ° C. The reaction gives a mixture of the desired N- (alkyl) -2-nitro-3,4-xylidine and N- (alkyl) -6-nitro-3,4-xylidine. The mixture can be separated into its components by column chromatography on silica gel using hexane as the eluent. Such separation is not necessary if it is desired to use this compound as an intermediate for the 2,6-dinitroxylidines or if the isomer mixtures can be used as such.

The N-alkyl-3,4-xylidines can be prepared by reacting 4-nitro-o-xylene or 3,4-xylidine (formula 2) with the appropriate ketone under a nitrogen atmosphere in the presence of a conventional hydro-30 generation catalyst, such as palladium. This reaction is shown in Figure 1 of the formula sheet, wherein X is NH2 or NO2; the ketone is methyl ethyl ketone, methyl propyl ketone or ethyl propyl ketone and sA has the aforementioned meaning.

An alternative route to the N- (alkyl) -3,4-xylidines of formula 3 comprises reacting 3,4-xylidine of formula 2, wherein X is NH 2, with one of the ketones as mentioned above, in the presence of an alkali metal cyanoborohydride, such as ΝβΒΗβΟΝ. Preferably, a molecular sieve is also used to bind the water formed by the reaction. This reaction can be carried out at a temperature of from 10 to 70 ° C, and is preferably carried out in the presence of a solvent such as a lower alcohol having 1-4 carbon atoms, such as a lower alcohol.

In yet another process for the preparation of the compounds of formula 3, 3,4-xylidine is treated with one of said ke-5 in the presence of a molecular sieve and a solvent such as dry benzene. This reaction gives the corresponding N- (alkylidene) -3,4-xylidine which can be reduced with an alkali metal borohydride or hydrogen and a hydrogenation catalyst to yield the corresponding N- (alkyl) -3,4-xylidine.

Since the N-alkyl group contains asymmetric carbon in some xylidines, optical isomers may exist. In such a case, said N-alkyl-xylidines may comprise the individual antimers as mixtures thereof.

Since separation is an expensive and time consuming operation, it is generally preferred to use the racemic mixtures rather than the individual antimers. Where separation is desired, N-alkyl compounds can be reacted with an optically active carboxylic acid such as 1-tartaric acid followed by separation of the diastereomers using conventional fractional crystallization.

The compounds of the invention as well as their preparation and use are further illustrated in the examples below. All parts and percentages therein are by weight unless otherwise indicated.

Example I

Preparation of N- (1-ethylpropyl) -3,4-xylidine 4-Nitro-o-xylene (10.0 g, 0.066 mol) is shaken in a Parr hydrogenator with diethyl ketone (20 cm @ 0.019 mol) .5% palladium on charcoal (0.5 g) and benzoic acid (0.5 g) with nearly 3 atmospheres hydrogen. After hydrogen uptake is complete, the slurry is filtered and analyzed by gas liquid chromatography, showing that N- (1-ethylpropyl) -3,4-xylidine is formed in 83% yield.

Example II

Preparation of N- (1-ethylpropyl) -3,4-xylidine

A solution of 3,4-xylidine (1.2 g, 0.01 mol) in diethyl ketone (5 cm 3) and methanol (20 cm 3) is stirred at room temperature in the presence of sodium cyanoborohydride (1.1 g) and 3A molecular weight sieving (3.0 to 40 g). The pH is checked every half hour and kept at 6 by addition of 8800037 5 * of acetic acid. After 7 hours, the sieves are removed by filtration, the filtrate diluted with water (100 cm 2) and then acidified with hydrochloric acid. The solution is then made basic with solid potassium carbonate and extracted with ethyl ether. The ether solution is dried and then evaporated to give the desired product as a residual oil in a yield of 97.5% and a purity of 93% as determined by gas liquid chromatography. The compound has a boiling point of 80 ° C at a pressure of 0.1 mm Hg. The elemental analysis is as follows: 10 calculated percentages for C13H21N: C 81.6; H 11.2; N 7.3.

percentages found: C 81.4; H 11.2; N 7.5.

Example III

Preparation of N-sec-butyl-3,4-xylidine N-sec-butyl-3,4-xylidine was prepared according to the procedure of Example II using an equivalent amount of methyl ethyl ketone for the diethyl ketone used therein. The desired product was obtained in quantitative yield with a purity of 96%. The boiling point was 75-77 ° C at a pressure of 0.4 mm and the following elemental analysis: calculated percentages for C 12 H 19 N: C 81.3; H 10.8; N 7.9.

percentages found: C 81.4; H 10.8; N 7.9.

Example IV

Preparation of N-sec.butyl-3,4-xylidine

Molecular sieves (type 5A, 300 g) are added to 79.2 g (1.0 mol) of methyl ethyl ketone and 121.0 g (1.0 mol) of 3,4-dimethylaniline in 1 liter of a dry benzene solution. The reaction mixture is stirred at room temperature for 16 hours. The mixture is then filtered from the molecular sieves which are washed with dry benzene. The benzene solutions are combined and evaporated in vacuo to give 198 g (100%) of the desired product. The product is sensitive to hydrolysis and is therefore immediately reduced in a hydrogenator using a 5% palladium-on-charcoal to yield N-sec-butyl-3,4-xylidine.

Examples V-VI

Preparation of N-sec-butyl-2-nitro-3,4-xylidine and N-sec-butyl-6-nitro-3,4-xylidine-40 N-sec-butyl-3,4-xylidine (5.3 g ) (0.03 mol) is dissolved in 10 cm 3. 8 G 0 0 0 3 7 6 dichloroethane and carefully treated with mixed acids (6 cm 3 concentrated sulfuric acid and 2.7 g concentrated nitric acid) at 15-25 ° C. After the addition is complete, the mixture is poured into water. The organic layer is separated and purified by column chromatography over silica gel using hexane as eluent. The first compound to be eluted was N-sec-butyl-2-nitro-3,4-xylidine, and was characterized by the nuclear magnetic resonance (NMR) and infrared (IR) spectra. The second compound eluted was N-secbutyl-6-nitro-3,4-xylidine and was characterized by the NMR and IR spectra. An analytical sample of the 6-nitro compound had a melting point of 73-75 ° C and the following elemental analysis: calculated percentages for 64.8, H 8.2, N 12.6.

percentages found: C 64.6; H 8.2; N 12.6.

Examples VII-VIII

Preparation of N- (1-ethylpropyl) -2-nitro-3,4-xylidine and N- (1-ethylpropyl) -6-nitro-3,4-xylidine_

The aforementioned compounds were prepared and isolated according to the procedure of Example V-VI, replacing the N-sec-butyl-3,4-xylidine used therein with an equivalent amount of N- (1-ethyl-propyl) -3, 4-xylidine. The 6-nitro compound after recrystallization from methanol had a melting point of 58-60 ° C and the following elemental analysis: calculated percentages for C13 H20 N2 O2: C 66.1, H 8.5; N 11.9. percentages found: C 66.1; H 8.6; N 11.7.

After purification by chromatography, the 2-nitro compound is an oil.

It had the following elemental analysis: calculated percentages for C ^ K ^ o ^ C ^ C 66.1, H 8.5, N 11.9. percentages found: C 67.7, H 8.9, N 12.0.

The 6-nitro compound is optionally prepared by 3.8 g (0.02 mol) of 30 N- (1-ethylpropyl) -3,4-xylidine and 5.0 cm (0.08 mol) of 70% concentrated nitric acid react as described in Example XII. The desired product is isolated in a conventional manner by chromatography on silica gel.

Example IX-XI

The selective herbicidal activity of the compounds of the invention over pre-emergence crops is demonstrated by the following experiments, in which the seeds of a variety of monocotyledonous and dicotyledonous plants are mixed separately with potting soil. 3 cm of this soil to be sown on a layer of potting soil of about 3.8 cm is placed in separate plastic pots measuring 6.4 by 6.4 cm. After planting, the pots are sprayed with the appropriate aqueous acetone solution containing the test compound in an amount sufficient to provide an equivalent of 0.06 to 10 kg / ha of test compound per pot. The treated pots are then placed on benches in a greenhouse and sprayed and cared for in accordance with greenhouse standards. The tests are terminated three or four weeks after treatment and each jar is examined and evaluated according to the following system.

The results are shown in Table A.

Rating system% difference in growth according to control * 0 - no effect 0 1 - possible effect 1 - 10 15 2 - poor effect 11-25 3 - moderate effect 26 - 40 5 - obvious damage 41 - 60 6 - herbicidal effect 61 - 75 7 - good herbicidal activity 76-90 20 8 - almost completely killing 91 - 99 9 - completely killing 100 4 - abnormal growth, ie a clear physiological malformation but with a total effect less than 5 according to the evaluation system.

* - based on visual assessment of position, size, external strength, bleach, growth deformity and the general appearance of the plant.

30 Plant Abbreviations CR - (Digitaria sanguinalis) Finger Grass PI - (Amaranthus retroflexus) Parrot Herb LA - (Chenopodium album) White Goosefoot COR - (Zea mays) Mais 35 WO - (Avenia fatua) Wild Oats MU - (Brassica Kaber) Mustard RAG - ( Ambrosia artemisiifolia) Ambrosia BA - (Echinochloa crusgalli) Cephala GHF - (Setaria viridis) Green Needle 40 MG - (Ipomoea purpurea and Ipomoea hederacea) Purple orfe .8800037 (.

8 COT - (Gossypium hirsutum) Cotton SB - (Beta vulgaris) Sugar beet SOY - (Glycine max) Soy. 8800037 9

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Examples XII-XXV

The method of converting the compounds of the invention to 2,6-dinitroaniline is illustrated in Examples XII-XVI. The utility of the products thus formed is demonstrated in the comparative examples XVII-XXV.

Example XII

Preparation of N-sec.butyl-2,6-dinitro-3,4-xylidine N-sec.butyl-3,4-xylidine (1.2 g, 6.7 x 10 µmole) is run at 15 ° C 10 was added to 70 percent nitric acid (13 cm 3). After an hour, the reaction mixture is poured into ice water and extracted with ethyl ether. The extract is dried over MgSO 4 and evaporated in vacuo to yield the desired product as 1.55 g of a solid residue. The product is purified by silica gel chromatography using hexane as eluent. The total weight of the purified product is 1.1 g (60%) and the product has a melting point of 41-45 ° C. Recrystallization from hexane gives the analytical sample with a melting point of 43-44eC and an elemental analysis of:

Calculated percentages for C 12 H 17 N 3 C> 4: C 53.9; H 6.4; N 15.7 20 Percentages found C 54.0; H 6.2; N 15.7.

Example XIII

Preparation of N- (1-ethylpropyl) -2,6-dinitro-3,4-xylidine

This compound is prepared according to the procedure of Example XII 25, substituting an equivalent amount of N- (1-ethylpropyl) -3,4-xylidine for the N-sec-butyl-3,4-xylidine used therein. The desired product is formed in a yield of 80%. Purification is by recrystallization from methanol to form a crystalline product having a melting point of 56-57 ° C and the following elemental analysis:

Calculated percentages for ¢ ^ 3 ^ 9 ^ 04: 0 55.3; H 6.8; N 14.9

Percentages found C 55.4; H 6.8; N 15.0.

Example XIV

35 Preparation of N- (1-ethylpropyl) -2,6-dinitro-3,4-xylidine N- (1-Ethylpropyl) -2-nitro-3,4-xylidine (1.0 g 4 x 10 4 mol) ) is added to 10 cm HNO3 (70% concentration). After 90 minutes, the reaction mixture is worked up as described in Example XII, whereby 100% crude yield of the desired dinitrop product is obtained. Gas-40 liquid chromatography shows that this product is 97% pure.

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Example XV

Preparation of N- (1-ethylpropyl) -2,6-dinitro-3,4-xylidine

The title compound is formed in a 90% crude yield according to the procedure of Example XIV, substituting an equivalent amount of N- (1-ethylpropyl) -6-nitro-3,4-xylidine for the 2-nitro compound used therein. This product had a purity of 90 Z.

Example XVI

41.0 g (0.214 mol) of N- (1-ethylpropyl) -3,4-dimethylaniline and 128 cra-1,2-dichloroethane are placed in a flask. The solution is stirred and cooled to 0-5 ° C. 254 g (3.22 mol) of 80% HNO3 are added at 0-5 ° C over 135 min. After the addition, the reaction mixture is kept at 0-5 ° C for 240 min. At the end of this period, the cold reaction mixture is poured onto 254 g of ice. 128 cm 3 of CICH2CH2CI is added. After removal of the aqueous phase, the product solution is washed with 5% aqueous bicarbonate and water. The crude product is obtained by drying the organic layer over MgSO 4, filtering and removing the solvent from the filtrate under reduced pressure. 52.3 g of the crude product with an estimated yield of 89.7 Z are obtained. The actual yield is 79.3 Z.

The product crystallizes after some time at ambient conditions.

Example XVII-XXV

The selective herbicidal activity of the compounds of the invention over pre-emergence crops is demonstrated by the following experiments in which the seeds of a variety of monocotyledonous and dicotyledonous plants are mixed separately with potting soil 30 and 1.3 cm. sow soil on about 3.8 cm of potting soil is placed in separate plastic pots of 6.4 by 6.4 cm. After planting, the pots are sprayed with the selected aqueous acetone solution containing the test compound in sufficient amount to provide an equivalent of 0.06-10 kg / ha of test compound per pot.

The treated pots are then placed on benches in a greenhouse and sprayed and cared for according to normal greenhouse standards. The tests are terminated three or four weeks after the treatment and each jar is examined and evaluated according to the aforementioned system. The results of these tests are set forth in Table B and demonstrate the excellent herbicidal activity of the products N-sec.butyl-2,6-dinitro-3,4 prepared according to the method of the invention. -xylidine; N- (1-ethylpropyl) -2,6-dinitro-3,4-xylidine and N- (1-methylbutyl) -2s6-dinitro-3,4-xylidine as well as the substantial inactivity of the closely related homologous compounds when used in equivalent amounts 5 or a duplicate thereof.

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Claims (3)

1. Process for the preparation of N-alkylxylidines, characterized in that N-sec-alkylxylidines of formula 1, wherein R 1 is a 1-methylpropyl, 1-methylbutyl or 1-ethylpropyl group and and R 3 each be a hydrogen atom or a nitro group, but not both are a nitro group. 2. Process for preparing N-alkylxylidines of formula 1, wherein R * is a 1-methylpropyl, 1-methylbutyl or 1-ethylpropyl group and R 1 and R 3 are each a hydrogen atom or a nitro group but not both a hydrogen atom characterized in that an N-sec-alkylxylidine prepared according to claim 1 is treated with concentrated nitric acid. 3. A method of preparing a herbicidal composition, characterized in that an N-sec-alkylxylidine of the formula I, prepared according to claim 1 or 2, in which R 1 or R 3 is a nitro group, is mixed with a carrier suitable for weed control. ****** .8800037