Synthesis
a) Synthesis of methyl 1-methyl-1H-indole-5-carboxylate
Methyl indole-5-carboxylate (5.0 g, 28.54 mmol, 1.0 eq.) was dissolved in DMF and cooled to 0 °C in an ice bath. Sodium hydride (1.37 g, 34.29 mmol, 1.2 eq.) was added slowly with stirring, keeping the reaction temperature at 0 °C. The reaction was carried out over a period of 20 minutes. After 20 min of reaction, iodomethane (6.08 g, 2.7 mL, 42.81 mmol, 1.5 eq.) was added dropwise. The reaction mixture was continued to be stirred at 0 °C for 4 hours. Upon completion of the reaction, the reaction was quenched with ice water and then extracted with ethyl acetate (150 mL × 2). The organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The yellow oil obtained was ground with hexane to give methyl 1-methyl-1H-indole-5-carboxylate as a tan solid (5.22 g, 97% yield).
References
[1] Patent: WO2005/40157, 2005, A2. Location in patent: Page/Page column 78
[2] Chemistry - A European Journal, 2015, vol. 21, # 4, p. 1463 - 1467
[3] Patent: WO2015/74123, 2015, A1. Location in patent: Page/Page column 59-60
[4] Organic Letters, 2006, vol. 8, # 7, p. 1339 - 1342
[5] Patent: WO2014/73904, 2014, A1. Location in patent: Paragraph 894-896
