4-Chloro-3-hydroxybenzoic acid

931409-94-8

34113-69-4

General procedure for the synthesis of 4-chloro-3-hydroxybenzoic acid from compound (CAS: 931409-94-8): boron tribromide (1 M in dichloromethane, 31 mL, 31.504 mmol) was slowly added dropwise to a solution of compound 38 (3.56 g, 15.752 mmol) in dichloromethane (30 mL) under ice bath cooling conditions. The reaction mixture was stirred at 0°C to room temperature for 18 hours. Upon completion of the reaction, the reaction was quenched with 0.88 aqueous ammonia solution and stirring was continued for 90 minutes at room temperature. Subsequently, the reaction mixture was acidified to pH 1 by dropwise addition of 2N aqueous hydrochloric acid solution and then extracted with ether (2 x 50 mL). The organic layers were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford 4-chloro-3-hydroxybenzoic acid as a light yellow solid in 90% yield (2.45 g). The product was characterized by 1H NMR (400 MHz, CD3OD): δ 7.36-7.38 (d, 1H), 7.44-7.47 (dd, 1H), 7.54-7.55 (d, 1H); LRMS APCI m/z 171 [M-H]-.