914348-94-0

General procedure: to a solution of 5-methyl-1H-indole-3-carbaldehyde (1.0 eq.) and di-tert-butyl dicarbonate (1.2 eq.) in acetonitrile was added 4-dimethylaminopyridine (DMAP, 0.1 eq.). The reaction mixture was stirred at room temperature overnight. After completion of the reaction, the reaction mixture was concentrated under reduced pressure. The residue was dissolved in dichloromethane and washed with saturated sodium bicarbonate solution. The organic and aqueous phases were separated. The aqueous phase was re-extracted with dichloromethane. All organic phases were combined and washed sequentially with saturated ammonium chloride solution, water and brine. The organic phase was dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give 1-Boc-5-methyl-3-formylindole crude. This BOC-protected compound can be used in the next step without further purification.

[1] Patent: WO2013/45516, 2013, A1. Location in patent: Page/Page column 129; 182
[2] European Journal of Medicinal Chemistry, 2016, vol. 112, p. 289 - 297