GB822199A - Process for the preparation of alpha-phenoxyalkanoic acids - Google Patents

Abstract

Compounds of formula <FORM:0822199/IV (a)/1> in which the nucleus X contains one or more halogen atoms and/or alkyl groups and R1 is an alkyl group of not more than 8 carbon atoms, are prepared by condensing an alkali metal salt of a phenol of formula <FORM:0822199/IV (a)/2> with an ester of formula <FORM:0822199/IV (a)/3> in which R1 is as defined above, R is a cyano or carboalkoxy group and R11 is an alkylsulphonyl, benzenesulphonyl or substituted benzenesulphonyl group, and thereafter hydrolysing the resulting alpha-phenoxyalkanoic acid nitrile or alkyl alpha-phenoxyalkanoate. The condensation may be carried out by adding the ester to an aqueous or alcoholic solution of the alkali metal phenate at an elevated temperature and under alkaline conditions. The nitrile or ester so obtained may be hydrolysed directly without preliminary isolation, for example by treatment with an alkali metal hydroxide solution, followed by acidification and filtration. The esters of formula III may be prepared as a preliminary stage in the process of the invention. The alpha-phenoxyalkanoic acids are used in herbicidal compositions. In examples: (1) alpha-cyanoethyl benzene sulphonate, prepared by reacting sodium cyanide and acetaldehyde in alkaline medium, followed by reaction with benzenesulphonyl chloride, is reacted with the sodium salt of 4-chloro-2-methylphenol, 2 : 4-dichlorophenol, 2 : 4 : 5 - trichlorophenol, p - chlorophenol, o-cresol or 2-bromo-4-chlorophenol, followed by hydrolysis with aqueous sodium hydroxide, acidification with hydrochloric acid and filtration to give alpha-(4-chloro-2-methyl-phenoxy) - or - (2 : 4 - dichlorophenoxy) - or -(2 : 4 : 5 - trichlorophenoxy)- or -(p - chlorophenoxy)- or -(p-methylphenoxy)- or -(2-bromo-4-chlorophenoxy)-propionic acid; (2) alphacyanoethyl toluene-p-sulphonate, prepared as in (1) but using toluene-p-sulphonyl chloride is reacted as in (1) with 4-chloro-2-methylphenol to give alpha-(4-chloro-2-methylphenoxy)-propionic acid; (3) alpha-cyanopropyl benzene sulphonate, prepared as in (1) but using propionaldehyde, is reacted with 2 : 4-dichlorophenol as in (1) to give alpha-(2 : 4-dichlorophenoxy)-butyric acid; (4) alpha-carboethoxyethyl benzenesulphonate or toluene-p-sulphonate, prepared by reacting ethyl lactate with benzenesulphonyl chloride or toluene-p-sulphonyl chloride in the presence of pyridine, is reacted with the sodium salt of 4-chloro-2-methylphenol and the product hydrolysed, acidified and filtered as in (1) to give alpha-(4-chloro-2-methylphenoxy)-propionic acid; (5) alpha - cyanoethyl methanesulphonate, prepared by treating lactonitrile in pyridine with methanesulphonyl chloride, is reacted as in (1) with 4-chloro-2-methylphenol to give alpha-(4 - chloro - 2 - methylphenoxy) - propionic acid. Specification 820,180 is referred to.