20699-85-8

20699-86-9

20699-85-8

General procedure for the synthesis of methyl 5-aminobenzothiophene-2-carboxylate from methyl 5-nitrobenzo[b]thiophene-2-carboxylate: to a reaction flask was added methyl 5-nitrobenzo[b]thiophene-2-carboxylate (1 g, 0.004 mol), concentrated nitric acid (20 mL, 0.24 mol) and SnCl2-2H2O (4.85 g, 0.017 mol). The reaction mixture was stirred at 80 °C for 1 h and subsequently cooled to room temperature. The pH of the reaction mixture was adjusted with 10% aqueous sodium hydroxide solution to 9~11. The resulting suspension was filtered and the solid residue was washed with water and methanol sequentially to afford the target product, methyl 5-aminobenzothiophene-2-carboxylate, as a yellow solid in quantitative yield.