478148-99-1

478149-00-7

Ethyl thieno[2,3-c]pyridine-2-carboxylate (C121, 577 mg, 2.99 mmol) was added to a solvent mixture of methanol (15 mL) and water (1.5 mL) with 2 M sodium hydroxide solution (1.5 mL, 3.0 mmol). The reaction mixture was stirred at room temperature for 24 hours. Upon completion of the reaction, the solvent was removed by vacuum concentration and the residue was dissolved in water (75 mL). The solution was acidified to pH 3 with concentrated hydrochloric acid to form a slurry. The solid product was collected by filtration, washed sequentially with water and ether, and dried to give thieno[2,3-c]pyridine-2-carboxylic acid (C122) as an off-white solid in 38% yield. High-resolution mass spectrometry (FAB) analysis showed that the calculated value of C8H5NO2S + H was 180.0119 and the measured value was 180.0119 (M + H)+.