2-Methyl-4H-thieno[3,2-b]pyrrole-5-carboxylic acid

238749-54-7

332099-14-6

General procedure for the synthesis of 2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylic acid from compound (CAS:238749-54-7): compound 3 (1.82 g, 8.70 mmol, 1 equiv.) was dissolved in ethanol (100 mL), followed by the addition of an aqueous sodium hydroxide solution (50 mL containing 5.35 g NaOH 134 mmol, 15.4 equiv). The reaction mixture was stirred under reflux conditions for 30 minutes. After completion of the reaction, the mixture was cooled and 6N aqueous hydrochloric acid solution was slowly added to neutralize the reaction system. The resulting precipitate was collected by filtration, the precipitate was washed well with water and finally dried under vacuum to afford the target product 2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylic acid (4) as a white solid (1.41 g, 89.5% yield). Thin layer chromatography (TLC) analysis (silica gel plate, unfolding reagent: hexane/ethyl acetate = 1:1): Rf = 0.2.