4-Methylbenzo(b)thiophene-2-carboxylicacid

146137-98-6

1735-13-3

The general procedure for the synthesis of 4-methylbenzo[b]thiophene-2-carboxylic acid using methyl 4-methylbenzo[b]thiophene-2-carboxylate as a raw material was as follows: a mixture of 203 mg of methyl 4-methylbenzo[b]thiophene-2-carboxylate, 50 mg of lithium hydroxide monohydrate, 2 mL of water, and 6 mL of methanol was stirred and reacted for 2 hours at 80 °C. After completion of the reaction, the reaction mixture was concentrated under reduced pressure. An appropriate amount of water was added to the concentrated residue, followed by washing the residue with tert-butyl methyl ether three times. Concentrated hydrochloric acid was slowly added to the aqueous layer, acidified and extracted three times with tert-butyl methyl ether. The organic layers were combined, washed with saturated brine and dried over anhydrous magnesium sulfate. Finally, the dried organic layer was concentrated under reduced pressure to give 189 mg of 4-methylbenzo[b]thiophene-2-carboxylic acid (hereinafter referred to as "Compound 20"). The product was characterized by 1H-NMR (CDCl3) with chemical shifts δ: 8.25 (s, 1H), 7.73-7.71 (m, 1H), 7.40-7.38 (m, 1H), 7.22-7.20 (m, 1H), 2.66 (s, 3H).