General procedure for the synthesis of 3-chloro-2-fluorobenzoic acid from 3-chloro-2-fluorobenzaldehyde: An acetone (75 mL) solution of 3-chloro-2-fluorobenzaldehyde (3 g, 18.92 mmol) was slowly added to an aqueous (30 mL) solution of sodium chlorite (6.81 g, 75.68 mmol) under cooling conditions in an ice bath. The reaction mixture was stirred at 0°C for 5 minutes. Subsequently, sulfamic acid (5.50 g, 56.76 mmol) was added all at once and stirring was continued for 30 min at the same temperature. The reaction process was monitored by thin layer chromatography (TLC). After completion of the reaction, the mixture was diluted with water (5 mL) and filtered. The filtrate was extracted with ethyl acetate (3 x 50 mL), the organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give 3-chloro-2-fluorobenzoic acid as a white solid (3.2 g, 97% yield).LC-MS analysis: 172.9 (M-H).
