Hydrochloric Acid → 4-Chloro-3-fluoro-2-methylsulphenylbenzoic acid

Participants

Reaction Steps

n-Butyl lithium (2.5M in hexane; 180 ml) was added with cooling to a solution of 4-chloro-3-fluorobenzoic acid (37.5 g) in dry tetrahydrofuran while maintaining the temperature below -40° C. The mixture was stirred at -30° to -40° C. for 3 hours. Dimethyl disulphide (60.5 g) was added and the mixture was stirred at -40° C. for 0.5 hours and at room temperature overnight. Hydrochloric acid (2M) was added and the layers were separated. The aqueous layer was extracted with ether and the combined organic layers were extracted with aqueous sodium hydroxide (2M) and water. The aqueous extracts were combined and acidified to pH 1 and extracted with ether, washed with water, dried (Na2 SO4) and filtered. The filtrate was evaporated to dryness and the residue was triturated with n-hexane and filtered to give 4-chloro-3-fluoro-2-methylsulphenylbenzoic acid (32.84 g) as a yellow solid, m.p. 149.5°-150.5° C.

Provenance & Evidence