GB1571388A

GB1571388A - Manufacture of esters

Info

Publication number: GB1571388A
Application number: GB15582/76A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1976-04-15
Filing date: 1976-04-15
Publication date: 1980-07-16
Also published as: ZA772040B; NL7704073A; AU2423077A; DE2716772A1; JPS52128337A; AU509353B2; NZ183787A; FR2348193A1

Description

(54) MANUFACTURE OF ESTERS (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to an improved process for the manufacture of esters of m -phenoxybenzyl alcohol.

A number of esters of m-phenoxybenzyl alcohol are of insecticidal value, for example those with certain substituted 2, 2 dimethylcyclopropanecarboxylic acids.

These esters may be prepared from the corresponding acids by converting these to the acid chloride which may then be reacted with m-phenoxybenzyl alcohol. The cyclopropanecarboxylic acids are conveniently isolated in the form of their methyl or ethyl esters and it has now been found that m-phenoxybenzyl esters can be obtained conveniently and in good yield from the methyl or ethyl esters of these or other acids under specified conditions.

According to the invention there is provided a process for preparing esters of m-phenoxybenzyl alcohol and its os-cyano and ex-ethynyl derivatives with carboxylic acids which comprises mixing a methyl or ethyl ester of the carboxylic acid, m-phenoxybenzyl alcohol or its c-cyano or a-ethynyl derivative and at least 0.02 mol of tetramethyl or tetraethyl titanate per mol of carboxylic ester and heating the mixture at a temperature such that the methanol or ethanol are removed by distillation as they are formed.

The ingredients of the process may be mixed in any order and the mixture, preferably stirred or otherwise agitated, raised to reaction temperature. The preferred reaction temperatures are between 80C and 1 600C. Temperatures outside this range may be used but lower temperatures may necessitate prolonged reaction times and higher temperatures involve a risk of decomposition of the product.

If desired a solvent may also be used, especially one which gives a reaction mix boiling at the desired reaction temperature so that the methanol or ethanol formed during the process is distilled off with a part of the solvent.

Suitable solvents are for example hydrocarbons such as toluene or methylcyclohexane, halogenated hydrocarbons wherein the halogen atom is inert under the reaction conditions, e.g. chlorinated aromatic hydrocarbons such as chlorobenzene, and ethers such as dioxan. Lower boiling solvents such as cyclohexane may be used but need a longer reaction period at atmospheric pressure. The solvent and other ingredients of the reaction mixture should be free from water.

Titanate esters of higher alcohols, e.g. tetrabutyl titanate, are also effective catalysts, but tend to form titanium compounds with the m-phenoxybenzyl alcohol with consequent lower yield and lower purity of the desired product.

The amount of ester of titanic acid is at least 0.02 mol., and preferably from 0.05 to 0.2 mol., per mol. of carboxylic ester.

The required proportions of m-phenoxybenzyl alcohol or its a-cyano or a-ethynyl derivative and methyl or ethyl ester of carboxylic acid are equimolar.

Excess of either reactant may be used if desired and may generally be recovered unreacted at the end of the process, for example by distillation under reduced pressure.

The ester produced by the process of the invention may be isolated by any convenient procedure, for example by removing the solvent, if any, and any unchanged reactant, by distillation to leave the crude ester which could be purified by conventional means suitable for the ester concerned.

The methyl or ethyl ester of a carboxylic acid which may be used in the process of the invention is any of such esters which has a boiling point significantly higher than the reaction temperature. Such esters may b derived from aliphatic, aromatic, cycloaliphatic or heterocyclic carboxylic acids but the process of the invention is of particular value for the manufacture of m-phenoxybenzyl, a-cyano and a - ethynyl m - phenoxybenzyl esters of insecticidal activity, for example from 4 - methy; - a isopropylphenylacetic acid or more especially of pyrethrin-type esters of 2, 2 dimethylcyclopropanecarboxylic acids.

Examples of these are particularly esters of 2, 2 - dimethylcyclopropanecarboxylic acids containing in the 3-position substituted vinyl groups such as 2', 2 dimethylvinyl, 2', 2' - dichlorovinyl, 2' ethylvinyl and 2', 2' - dibromovinyt. These acids are normally obtained as mixtures of cis and trans forms, which in the case of the desired m-phenoxybenzyl esters have different insecticidal potency. The process of the invention is particularly valuable in that it brings about a minimum of interconversion of the cis into the less potent trans forms and also lower formation of byproducts.

The invention is illustrated but not limited by the following Examples in which all parts and percentages are by weight unless otherwise stated.

Example I A solution of 56 parts of m-phenoxybenzyl alcohol, 80 parts of ethyl 2, 2 - dimethyl - 3 - (2', 2 ' - dichlorovinyl) - cyclopropanecarboxylate (cis: trans ratio, 58 : 42) and 3.9 parts of tetraethyl titanate in 420 parts of dry toluene was stirred and heated at the boiling point. The azeotrope of ethanol and toluene was removed by distillation at the rate of 50 parts per hour while maintaining the reaction volume by the addition of fresh toluene. After 4 hours the toluene was removed by heating under reduced pressure and the residue heated to a temperature of 160"C at a pressure of 0.3 mm. of mercury.Volatile fractions removed were 26 parts of unreacted ethyl 2, 2 dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropanecarboxylate, boiling at 80 to 100"C at a pressure of 0.3 mm. of mercury and 2 parts of unchanged m-phenoxybenzyl alcohol, boiling at 120-1700C at 0.3 mm. of mercury.

There was obtained 90 parts of product containing 38.3% cis and 54.8% trans isomer of m-phenoxybenzyl 2, 2 - dimethyl 3 - (2', 2' - dichlorovinyl) - cyclopropanecarboxylate.

Example 2 A mixture of 80 parts of ethyl 2 2 dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropanecarboxylate (cis - trans ratio, 55:45), 85.7 parts of m-phenoxybenzyl alcohol and 3.53 parts of tetramethyl titanate was stirred at 138-140"C under a slow stream of nitrogen. Ethanol formed in the reaction was continually removed by distillation.After 18 hours the pressure was reduced to 0.3 mm. of mercury and the temperature raised to 1800C. 2.2 Parts of unreacted ethyl 2,2 dimethyl - 3 - (2', 2 ' 2' - dichlorovinylcydop- ropane - carboxylate, boiling at 8-1000C and 21.7 parts of ' unchanged m-phenoxybenzyl alcohol, boiling at 100-170"C, were removed by distillation.

The residue was 119.9 parts of m-phenoxybenzyl 2, 2- dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropanecarboxylate, (cis-trans ratio, 55 : 45).

Example 3 A mixture of 70.5 parts of methyl 2, 2 dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropane carboxylate (cis-trans ratlo, 48:52 56 parts of 3-phenoxybenzyl alcohol, 433 parts of dry toluene and 3.0 parts of tetramethyl titanate was stirred and heated at the boiling point. The binary mixture of ethanol and toluene was removed by distillation at a rate of 50 parts per hour whilst maintaining the reaction volume by the addition of fresh dry toluene. After 4 hours' reaction a further charge of 1 part of tetramethyl titanate was added and the reaction was continued for a further 6 hours.

The toluene was removed by heating under reduced pressure and the residue was heated to a temperature of 1600C at a pressure of 0.3 mm of mercury.

Volatile fractions were removed to leave 81 parts of product containing m phenoxybenzyl 2, 2 - dimethyl - 3 - (2', 2 ' - dichlorovinyl) - cyclopropane carboxylate, the cis:trans isomer ratio of which was 46:54.

Example 4 A mixture of 70.5 parts of methyl 2, 2 dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 48:52), 67.5 parts of 3-phenoxybenzyl alcohol and 3.52 parts of tetramethyl titanate was stirred at 138-140"C under a slow stream of nitrogen. Methanol formed in the reaction was continually removed by distillation. After 20 hours' reaction a further charge of 0.8 parts of tetramethyl titanate was added and the reaction was continued for a further 8 hours. The pressure was reduced to 0.05 mm of mercury and the temperature was raised to 1800C. 5.24 Parts of methyl 2, 2 dimethyl - 3 - (2', 2' - dichlorovinyl) - cyclopropane carboxylate boiling at 60-680C and 1 2.1 1 parts of unchanged 3-phenoxybenzyl alcohol, boiling at 120-164"C were removed by distillation.

The residue was 106.8 parts of m phenoxybenzyl 2, 2 - dimethyl -3 - (2', 2' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 45:55).

Example 5 A mixture of 237 parts of ethyl 2, 2 dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 40:60), 200 parts of 3-phenoxybenzyl alcohol and 10.6 parts of tetramethyl titanate was stirred at 135-400C under a slow stream of nitrogen. Ethanol formed in the reaction was continually removed by distillation. After 20 hours' reaction a further charge of 2.4 parts of tetramethyl titanate was added and the reaction was continued for a further 8 hours. The pressure was reduced to 0.05 mm of mercury and the temperature was raised to 1800C, 20.4 parts of ethyl 2, 2 dimethyl - 3 - (2', 2' - dichlorovinyl) - cyclopropane carboxylate and 21.9 parts of 3-phenoxybenzyl alcohol were removed by distillation.The residue was 351 parts of m phenoxybenzyl 2, 2 - dimethyl - 3 - (2', 2 ' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 40:60).

Example 6 A solution of 40 parts m - phenoxybenzyl alcohol, 57 parts of ethyl 2, 2 - dimethyl - 3 (2', 2' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 40:60) and tetramethyl titanate (3.82 parts as a 45% methanolic paste) in 300 parts of dry xylene was stirred and heated at the boiling point.

The mixture of ethanollxylene was removed by distillation at the rate of about 50 parts per hour while maintaining the original volume by the addition of fresh xylene.

After 32 hours the mixture was cooled to 90 C, water (2 parts) was added and the mixture was stirred for a further 10 minutes.

Magnesium sulphate was added and the mixture was filtered.

The xylene was removed under reduced pressure and the residue was distilled to an internal temperature of 100"C/0.2 mm Hg.

Unreacted ester (16.5 parts) was removed, leaving m-phenoxybenzyl 2, 2 - dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropane carboxylate (67.5 parts) comprised of 36.2% cis isomer and 50.1% trans isomer.

WHAT WE CLAIM IS: 1. A process for preparing esters of m-phenoxybenzyl alcohol and its a-cyano and a-ethynyl derivatives with carboxylic acids which comprises mixing a methyl or ethyl ester of the carboxylic acid, m-phenoxybenzyl alcohol or its a-cyano or a-ethynyl derivative and at least 0.02 mol of tetramethyl or tetraethyl titanate per mol of carboxylic ester and heating the mixture at a temperature such that the methanol or ethanol are removed by distillation as they are formed.

2. A process as claimed in Claim 1 wherein the reaction temperature is between 80" and 1600C.

3. A process as claimed in Claim 1 or Claim 2 wherein the reaction is carried out in an anhydrous solvent.

4. A process as claimed in Claim 3 wherein the solvent is such that the reaction mixture boils at the desired reaction temperature so that the methanol or ethanol formed during the process is distilled off with a part of the solvent.

5. A process as claimed in any one of Claims 1 to 4 wherein the amount of tetramethyl or tetraethyl titanate which is used is from 0.05 to 0.2 mol per mol of carboxylic ester.

6. A process as claimed in any one of Claims 1 to 5 wherein the m-phenoxybenzyl alcohol or its a-cyano or a-ethynyl derivative and the methyl or ethyl ester of the carboxylic acid are employed in equimolar proportions.

7. A process as claimed in any one of Claims 1 to 6 wherein the carboxylic acid is a 2, 2 - dimethylcyclopropanecarboxylic acid which gives pyrethrin-type esters with m-phenoxybenzyl alcohol or its a-cyano or a-ethynyl derivative.

8. A process as claimed in Claim 7 wherein the 2, 2 - dimethylcyclopropanecarboxylic acid contains a 2', 2 '-dimethylvinyl, 2', 2 '-dichlorovinyl, 2'-ethylvinyl or 2', 2'-dibromovinyl group in the 3-position.

9. A process for preparing esters of m-phenoxybenzyl alcohol and its a-cyano and a-ethynyl derivatives with carboxylic acids substantially as hereinbefore described in the foregoing Example 1 or Example 2.

10. A process for preparing esters of m-phenoxybenzyl alcohol and its a-cyano and a-ethynyl derivatives with carboxylic acids substantially as hereinbefore described in any one of the foregoing Examples 3 to 6.

11. Esters of m-phenoxybenzyl alcohol and its a-cyano and a-ethynyl derivatives with carboxylic acids whenever obtained by a process as claimed in any one of Claims 1 to9.

12. Esters of m-phenoxybenzyl alcohol and its a-cyano and a-ethynyl derivatives with carboxylic acids whenever obtained by a process as claimed in Claim 10.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 120-164"C were removed by distillation. The residue was 106.8 parts of m phenoxybenzyl 2, 2 - dimethyl -3 - (2', 2' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 45:55). Example 5 A mixture of 237 parts of ethyl 2, 2 dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 40:60), 200 parts of 3-phenoxybenzyl alcohol and 10.6 parts of tetramethyl titanate was stirred at 135-400C under a slow stream of nitrogen. Ethanol formed in the reaction was continually removed by distillation. After 20 hours' reaction a further charge of 2.4 parts of tetramethyl titanate was added and the reaction was continued for a further 8 hours. The pressure was reduced to 0.05 mm of mercury and the temperature was raised to 1800C, 20.4 parts of ethyl 2, 2 dimethyl - 3 - (2', 2' - dichlorovinyl) - cyclopropane carboxylate and 21.9 parts of 3-phenoxybenzyl alcohol were removed by distillation.The residue was 351 parts of m phenoxybenzyl 2, 2 - dimethyl - 3 - (2', 2 ' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 40:60). Example 6 A solution of 40 parts m - phenoxybenzyl alcohol, 57 parts of ethyl 2, 2 - dimethyl - 3 (2', 2' - dichlorovinyl) cyclopropane carboxylate (cis:trans ratio 40:60) and tetramethyl titanate (3.82 parts as a 45% methanolic paste) in 300 parts of dry xylene was stirred and heated at the boiling point. The mixture of ethanollxylene was removed by distillation at the rate of about 50 parts per hour while maintaining the original volume by the addition of fresh xylene. After 32 hours the mixture was cooled to 90 C, water (2 parts) was added and the mixture was stirred for a further 10 minutes. Magnesium sulphate was added and the mixture was filtered. The xylene was removed under reduced pressure and the residue was distilled to an internal temperature of 100"C/0.2 mm Hg. Unreacted ester (16.5 parts) was removed, leaving m-phenoxybenzyl 2, 2 - dimethyl - 3 - (2', 2' - dichlorovinyl) cyclopropane carboxylate (67.5 parts) comprised of 36.2% cis isomer and 50.1% trans isomer. WHAT WE CLAIM IS:

1. A process for preparing esters of m-phenoxybenzyl alcohol and its a-cyano and a-ethynyl derivatives with carboxylic acids which comprises mixing a methyl or ethyl ester of the carboxylic acid, m-phenoxybenzyl alcohol or its a-cyano or a-ethynyl derivative and at least 0.02 mol of tetramethyl or tetraethyl titanate per mol of carboxylic ester and heating the mixture at a temperature such that the methanol or ethanol are removed by distillation as they are formed.