64-17-5

88-13-1

5751-80-4

Thirteen mL (200 mmol) of thionyl chloride was added slowly and dropwise at 0 °C to a 100 mL ethanol solution containing 9 g (70 mmol) of 3-thiophenecarboxylic acid and 86 mg (0.7 mmol) of 4-dimethylaminopyridine. The reaction mixture was gradually warmed from 0 °C to room temperature over 48 h with continuous stirring. Subsequently, the reaction solution was evaporated to dryness. The resulting residue was purified by silica column chromatography with the eluent being a 1:1 heptane/dichloromethane solvent mixture. Finally 10 g (91% yield) of ethyl thiophene-3-carboxylate was obtained.