Synthesis
GENERAL METHOD: 3-indolecarboxaldehyde, triethylamine (1.3 eq.) and 10 mol% DMAP were dissolved in dichloromethane and di-tert-butyl dicarbonate (1.2 eq.) was added slowly. The reaction mixture was stirred at room temperature until complete consumption of the ingredients was shown by thin layer chromatography (TLC) monitoring. Upon completion of the reaction, the reaction mixture was diluted with dichloromethane and subsequently washed with water. The organic layer was separated, washed with saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by fast column chromatography (eluent ratio: ethyl acetate/hexane = 1:5 for 1a and 1b; ethyl acetate/hexane = 1:9 for 1c) to afford the target compounds tert-butyl 3-formyl-1H-indole-1-carboxylate (1a-1c).
References
[1] Synthetic Communications, 2000, vol. 30, # 12, p. 2143 - 2159
[2] Organic and Biomolecular Chemistry, 2011, vol. 9, # 22, p. 7904 - 7912
[3] Bulletin of the Korean Chemical Society, 2013, vol. 34, # 2, p. 357 - 358
[4] Journal of Organic Chemistry, 2016, vol. 81, # 4, p. 1723 - 1730
[5] Journal of the American Chemical Society, 2018, vol. 140, # 20, p. 6432 - 6440
