Aluminium chloride powder (66.75g, 0.5 mole) was added during one hour to a stirred mixture of dry 2-chlorophenol (27.3g, 0.22 mole), powdered succinic anhydride (20g, 0.2 mole) and dry sym-tetrachlorethane (150 ml) while the temperature was allowed to rise from 20° C to 40° C. The resultant mixture was heated in an oil bath at 135° C for 2 hours, then cooled in ice and hydrolysed with cold 10% hydrochloric acid solution (100 ml). Tetrachloroethane was removed by steam distillation and the aqueous residue precipitated a gum which was purified by standard procedures to give 31.97g, 70%, of a mixture of 3-(3-chloro-2-hydroxybenzoyl) propionic acid and 3-(3-chloro-4-hydroxybenzoyl)propionic acids. Esterification of the mixed acids with methanol - hydrogen chloride and separation of the products by column chromatography (silica, 5/1 chloroform/petroleum ether B.p. 60°-80° C) gave methyl 3-(3-chloro-2-hydroxybenzoyl)propionate (m.p. 60°-62° C) and methyl 3-(3-chloro-4-hydroxybenzoyl)propionate (m.p. 85°-89° C). Hydrolysis of the latter ester with dilute sodium hydroxide solution gave 3-(3-chloro-4-hydroxybenzoyl)propionic acid (m.p. 155°-160° C). The pure acid, on recrystallisation from water, had m.p. 160°-162° C.
