FR2575746A1 - Process for the preparation of pyrethroids - Google Patents

Abstract

Preparation of compounds of general formula I: in which R is a halogen atom or a C1-4 alkyl radical. A compound of formula II: in which R is as above, is reacted with an alkaline phenoxide of general formula III: in the presence of a catalyst based on copper and/or on a copper(I) salt. Preparation of pyrethroids with insecticidal use.

Description

dans laquelle R représente un atome d'halogène ou un radical alkyle de 7 à 4 atomes de carbone.The present invention relates to a new process for the preparation of compounds of general formula (I)

in which R represents a halogen atom or an alkyl radical of 7 to 4 carbon atoms.

The compounds of general formula (I) are important selective insecticides.

Several processes are known for the preparation of these compounds. All are characterized in that an ester group is formed with a diphenyl ether derivative and after the formation of the ester group, the additional conversion is carried out exclusively on the acid component. (GB Nos. 1,413,491 and 1,438,129;
US 4,255,351 and 4,289,711 and DE OS nO 2,716,771, 2,437,882, 2,651,341).

dans laquelle R a la même signification que ci-dessus (voir J. Agric. Food Chem 29, 1118, 1981), ester qu'on peut obtenir presque quantitativement à partir d'alcool 3-bromobenzylique et de chlorure d'acide perméthrique, l'alcool benzylique étant préparé d'une façon économique et simple à partir de benzaldéhyde au lieu d'éther diphénylique, on ne pouvait pas s'attendre à ce que la réaction puisse se dérouler avec succès sans changement des molécules de formule générale (II). Although it would have been obvious to form the ether group at the last stage by substitution of the bromine atom for the ester of general formula (II)

in which R has the same meaning as above (see J. Agric. Food Chem 29, 1118, 1981), an ester which can be obtained almost quantitatively from 3-bromobenzyl alcohol and permethric acid chloride, benzyl alcohol being prepared in an economical and simple way from benzaldehyde instead of diphenyl ether, it could not be expected that the reaction could proceed successfully without changing the molecules of general formula (II ).

Diphenyl ethers can be prepared by the Ulmann reaction in an alkaline medium at a relatively high temperature and in the presence of heavy metals or metal salts (copper). Dank The Ulmann reaction conditions, in accordance with the state of the art, one could hardly hope that the dichlorovinyl and the ester group would remain intact. It has surprisingly been found that the ester of general formula (II) can be converted into an ether of formula (I) with excellent yield and with heating in the presence of an alkaline phenolate of general formula (III) .

and in the presence of a copper-based catalyst and / or a copper salt.

dans laquelle R représente un atome d'halogène ou un radical alkyle de 1 à 4 atomes de carbones par réaction d'un composé de formule générale (II)

dans laquelle R est tel que défini plus haut, avec un phénolate alcalin de formule générale (III)

de préférence en présence d'un catalyseur à base d'une poudre de cuivre et/ou d'un sel de cuivre (I) et facultativement en présence d'une base organique a' une température de 120 à 1800C dans un solvant et/ou diluant organiques.Consequently, the present invention relates to the preparation of the esters of general formula I

in which R represents a halogen atom or an alkyl radical of 1 to 4 carbon atoms by reaction of a compound of general formula (II)

in which R is as defined above, with an alkaline phenolate of general formula (III)

preferably in the presence of a catalyst based on a copper powder and / or a copper salt (I) and optionally in the presence of an organic base at a temperature of 120 to 1800C in a solvent and / or organic thinner.

 The formation of the ether of general formula (I) is preferably carried out with potassium phenolate, advantageously at a temperature of 135 to 15,500 and with the use of a copper powder as catalyst activated by iodine and pyridine and with the use of xylene as solvent or diluent.

The following examples, in which all the proportions are by weight, serve to illustrate the invention without in any way limiting its scope Example 1
20.9 g (0.1 mole) of 2- (2.2 dichiorovinyl) -3.3-dinié thyl-cyclopropane-carboxylic acid are dissolved in 50 ml of benzene and 0.5 ml of solution is added to the solution. pyridine and then, with stirring at room temperature, 7.6 ml (105 mmol) of thionyl chloride are added dropwise over 30 minutes. Once the evolution of gas becomes slower, the mixture is heated under reflux for 3 hours. The reaction mixture is evaporated in vacuo, the residue is dissolved in 25 ml of pyridine and a solution of 18.7 g (0.1 mol) is added dropwise with stirring at 15-200C over 30 minutes. 3-bromobenzyl alcohol in 25 ml of pyridine. The mixture is further stirred for 4 hours at room temperature and filtered. The filtrate is evaporated in vacuo and 36.68 g (97% yield) of 5-bromobenzyl-2- (2,2-dichlorovinyl) -3,3-dimethylcyclopropane carboxylate are obtained.

Example 2
5.18 g (55 mmol) of phenol, 3.31 g (50 mmol, 85%) are stirred and heated using a water condenser until the condensation of water is complete. ) potassium hydroxide, 18 ml of xylene. The mixture is then cooled to 1000C and 0.16 g of copper powder activated with iodine and 0.5 ml of pyridine are added, then a solution of 18.9 g is added dropwise over 10 minutes (50 mmol) of 3-bromobenzyl-2- (2,2-dichlorovinyl) -3,3-dimethyl-cyclopropane carboxylate in 5 ml of xylene. The reaction mixture is heated for 6 hours with stirring under reflux. After cooling, the reaction mixture is filtered, the filtrate is washed with 2 × 20 ml of a 10% solution of sodium hydroxide, treated with perlite, filtered, evaporated in vacuo and purified, then eluted with benzene on a column of silica gel. 16.95 g (86% yield) of 3-phenoxybenzyl-2- (2, 2-dichlorovinyl) -3,3-dimethylcyclopropane (Ia) carboxylate are thus obtained, the product being identical as regards its physicochemical properties. and all of its spectroscopic data to the substance prepared by a known method.

Example 3
14.9 g (50 mmol) of 2- (2.2 dibromovinyl) -3.3-dimé thyl-cyclopropane-carboxylic acid are dissolved in 30 ml of benzene and 0.2 ml of pyridine is added to the solution, then 3.8 ml of thionyl chloride are added dropwise at room temperature with stirring. The mixture is heated for three hours under reflux and evaporated in vacuo. The residue is dissolved in 15 ml of pyridine and, with stirring at 20 ° C., a solution of 9.35 g (50 mmol) of 3-bromo-benzyl alcohol in 10 ml of pyridine is added dropwise over 30 minutes. the mixture for 4 hours at room temperature, then filtered and the filtrate is evaporated.

21.71 g (93% yield) of 3-bromo-benzyl-2- (2,2-dibromovinyl) -3,3-methyl-cyclopropane are obtained. 5.18 g (55 mmol) of phenol, 3.08 g (46 mmol, 85%) of potassium hydroxide and 20 ml of xylene are heated with stirring in a plant fitted with a water trap to 1 l completion of water condensation. The mixture is cooled to below 100 ° C. and 0.15 g of copper powder activated with iodine and 0.5 ml of pyridine is added, then in the next 10 minutes a solution in 10 ml of xylene of 3-bromobenzyl-2- (2,2-dibromovinyl) - 3,3-dimethylcyclopropane carboxylate prepared as described. The reaction mixture is heated with stirring for 5 hours, cooled and filtered. The filtrate is washed with 2 x 20 ml of a 10% sodium hydroxide solution, treated with perlite, filtered and evaporated in vacuo. The residue is purified on a column of silica gel and eluted with benzene. 17.64 g (yield 79%) of 3-phenoxy benzyl-2- (2,2-dibromovinyl) -3,3-dimethylcyclopropane carboxylate are thus obtained and the spectroscopic data of the product are identical to that of the product which is obtained by a known method.

Example 4
16.82 g (0.1 mol) of 2- (2,2-dimethylvinyl) -3,3-dimethylcyclopropane-carboxylic acid are dissolved in 50 ml of benzene and 0.5 ml of pyridine is added to the solution, then under stirring at room temperature, 7.6 ml of thionyl chloride are added dropwise. The mixture is then heated for 3 hours and evaporated in vacuo. The residue is dissolved in 25 ml of pyridine and, with stirring at 200 ° C., 18.7 g of 3-bromobenzyl alcohol dissolved in 25 ml of pyridine are added dropwise over 30 minutes. The reaction mixture is stirred for 4 hours at room temperature, filtered and the filtrate is evaporated. 32.38 g (96% yield) of 3-bromo-benzyl-2- (2,2-dimethylvinyl) -3,3-dimethylcyclopropane carboxylate are obtained.

 -Warm with stirring using a water trap until water condensation is complete, 5.18 g (55 mmol) of phenol, 3.31 g (50 mmol, 85%) of potassium hydroxide in 20 ml of xylene. The mixture is cooled above 1000C and 0.16 g of copper powder activated with iodine and 0.5 ml of pyridine are added, then within 16 minutes, 16.86 g are added dropwise (50 mmol) of 3-bromobenzyl-2- (2, 2-dimethylvinyl-3, 3-dimethyl-cyclopropane carboxylate in 10 ml of xylene. The reaction mixture is heated with stirring for 6 hours, cooled and filtered. The filtrate is washed with 2 x 20 ml of a 10% sodium hydroxide solution, treated with perlite, filtered and evaporated under vacuum. The residue is eluted with benzene on a column of gel. silica and 15.24 g (87% yield) of 3-phenoxybenxyl-2- (2,2-dimethylvinyl) - 3,3-dimethylcyclopropane carboxylate are thus obtained and the spectroscopic data of the product are identical to that of a product obtained by a conventional process.

Claims (5)

- PEVENDICADIONS -  1 - Process for the preparation of compounds of general formula (I)

 in which R represents a halogen atom or an alkyl radical of 1 to 4 carbon atoms, characterized in that a compound of general formula (II) is reacted

 in which R is as defined above, with an alkaline phenolate of general formula III

 in the presence of a copper-based catalyst and / or a copper (I) salt.  2 - Process according to claim 1, characterized in that the reaction is carried out with potassium phenolate and in the presence of a copper catalyst preferably a copper powder activated with iodine.  3 - Process according to claim 1 or 2, characterized in that the formation of the ether is carried out in the presence of a catalytic proportion of pyridine.  4 - Process according to claim 1, 2 or 3, characterized in that the reaction is carried out in an aprotic organic solvent, preferably in the presence of xylene.  5 - Process according to any one of claims 1 to 4, characterized in that the formation of the ether is carried out at a temperature of 120 to 1800C, preferably 135 to 155 "C.