Synthesis
Step 2. Synthesis of ethyl 2-amino-1H-indole-3-carboxylate [Formula 12-3]: Ethyl 2-cyano-2-(2-nitrophenyl)acetate [Formula 12-2] (16 g, 68.315 mmol) was dissolved in acetic acid (200 mL), and zinc powder (17.86 g, 273.25 mmol) was added, and the reaction was stirred for 24 hr at 65 °C. Upon completion of the reaction, the zinc powder was removed by diatomaceous earth filtration and the acetic acid was removed by distillation under reduced pressure to give a solid product. The resulting solid was dissolved in excess dichloromethane and subsequently crystallized by addition of hexane to give ethyl 2-aminoindole-3-carboxylate (6 g, 44% yield).
References
[1] Chinese Journal of Chemistry, 2013, vol. 31, # 2, p. 263 - 266
[2] Patent: WO2013/62344, 2013, A1. Location in patent: Page/Page column 28; 99
[3] Patent: US2014/315889, 2014, A1. Location in patent: Paragraph 0472-0474
[4] Tetrahedron Letters, 2006, vol. 47, # 2, p. 159 - 162
[5] Bioorganic and Medicinal Chemistry, 2012, vol. 20, # 20, p. 6123 - 6133,11
