Thiophene-3,4-dicarbonitrile (13.4 g, 100 mmol) and KOH (56.1 g, 1 mol) were dissolved in ethylene glycol (167 ml), and heated under stirring overnight. The solution was cooled, put into distilled water, and washed with diethyl ether. The aqueous layer was oxidized with saturated hydrochloric acid, and organic materials were extracted with ethyl acetate. The organic layer was dried over MgSO and the4, solvent was evaporated Then, recrystallization was performed in distilled water to obtain thiophene-3,4-dicarboxylic acid (15.2 g, 88percent).
