17721-06-1

82685-95-8

17721-06-1

Isopropyl-3-thiophene carbamate (177 g; 0.975 mol) was heated and refluxed in methanol (1.2 L) and an aqueous solution containing sodium hydroxide (200 g) for 4 hours. After completion of the reaction, methanol was removed by distillation under reduced pressure. The cooled reaction mixture was extracted with ether (5L), and the extract was washed with water and aqueous sodium chloride solution sequentially, and then dried. The solvent was evaporated under reduced pressure to give 3-aminothiophene in oil form in 57% yield. The resulting 3-aminothiophene was dissolved in ice bath cooled methanol (500 mL) and dimethylethynyl dicarboxylate (80 g; 0.50 mol) was added slowly and dropwise.