Synthesis
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.
References
[1] Patent: WO2006/101454, 2006, A1. Location in patent: Page/Page column 45
[2] Bioorganic and Medicinal Chemistry, 2002, vol. 10, # 5, p. 1611 - 1618
[3] Journal of the American Chemical Society, 2000, vol. 122, # 27, p. 6382 - 6394
[4] ACS Medicinal Chemistry Letters, 2014, vol. 5, # 9, p. 963 - 967
[5] Patent: WO2005/42513, 2005, A1. Location in patent: Page/Page column 57-58