The general procedure for the synthesis of benz[b]thiophene-2-carboxylic acid from benz[b]thiophene-2-carboxylic acid was as follows: benz[b]thiophene-2-carboxylic acid (356.42 mg, 2 mmol) was suspended in anhydrous toluene (6 mL) and thionyl chloride (4.4 mL, 60 mmol) and N,N-dimethylformamide (DMF, 0.05 mL) were added. After stirring at room temperature, the mixture was heated to reflux for 8 hours. Upon completion of the reaction, the volatiles were removed under reduced pressure to afford benzo[b]thiophene-2-carbonyl chloride as a yellow powder. Purification by rapid chromatography on silica gel using ethyl acetate/hexane (1:9, v/v) as eluent gave the target product (393.64 mg, 94.9% yield) as a white powder. The spectral data of the product were in agreement with those reported in the literature.1H NMR (300 MHz, CDCl3): δ 8.31 (s, 1H), 7.04-7.89 (m, 2H), 7.60-7.46 (m, 2H); 13C NMR (300 MHz, CDCl3): δ 161.14, 144.07, 138.05, 136.59, 135.89, 128.75, 126.68, 125.66, 122.91.
![BENZO[B]THIOPHENE-2-CARBONYL CHLORIDE](/CAS/GIF/39827-11-7.gif)