54819-86-2

The invention provides a preparation method of a phenoxycarboxylic acid herbicide, wherein the preparation method includes the steps: S1, carrying out condensation reaction of phenol or o-cresol withchlorocarboxylic ester under the action of an alkaline substance to obtain phenoxycarboxylic ester, wherein the chlorocarboxylic ester has the general formula of ClR1COOR, R1 is C1-3 alkylene or alkylidene, and R is C1-10 alkyl or C3-10 cycloalkyl; S2, carrying out selective chlorination of phenoxycarboxylic ester with a chlorinating agent under the action of a first catalyst and a second catalyst, to obtain chlorobenzoxycarboxylic ester, wherein the first catalyst is selected from Lewis acid, the second catalyst is C5-22 thioether compounds, thiazole compounds, isothiazole compounds or thiophene compounds; and S3, carrying out acidolysis reaction of chlorobenzoxycarboxylic ester, to obtain the phenoxycarboxylic acid herbicide represented by the formula I, wherein R3 is H, Cl or CH3. The preparation method can improve the product quality and the operation environment of a production site, and has low quantity of three wastes.

Mono- or polycarboxylic acid esters are prepared by reacting a salt of such carboxylic acid with an organic halocompound, e.g., a (cyclo)alkyl, (cyclo)alkenyl, aryl or aralkyl halide, in an aqueous reaction medium, in the presence of a catalytically effective amount of a phase transfer catalyst, for example an onium salt.

A racemic or optically active alkyl 2-chloropropionate is prepared, respectively, from a racemic or optically active alkyl lactate by, in a first step, gradually bringing the alkyl lactate into contact with the thionyl chloride, in the presence of an organic base, while maintaining, in the reaction mixture, an excess of thionyl chloride, relative to the amount of alkyl lactate introduced into this mixture, at a temperature below the decomposition point of the chlorosulphinate of the alkyl lactate, which is formed as an intermediate, and then, in a second step, in heating the reaction mixture resulting from the first step at a temperature which is at least equal to the decomposition point of the chlorosulphinate of the alkyl lactate. The alkyl 2-chloropropionates can be used for the manufacture of the racemic or optically active 2-phenoxypropionic acids.