Sodium borohydride → ethyl 1-oxo-2,3,4,5-tetrahydro-1H-[1,4]diazepino[1,2-a]indole-8-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a suspension of diethyl 1-(2-cyanoethyl)-1H-indole-2,6-dicarboxylate (1.5 g, 4.8 mmol) in THF (12 mL) and methanol (16 mL) is added CoCl2 (1.3 g, 9.6 mmol). The bright blue suspension/solution is cooled to 0° C., and NaBH4 (1.8 g, 48.0 mmol) is carefully added in small portions. As each portion is added H2 is formed violently and the suspension becomes black. After the addition of NaBH4 is complete, the mixture is warmed up room temperature for 60 min and is then heated at reflux for 16 h. The mixture is cooled to room temperature and is diluted with EtOAc. The mixture is filtered through Celite, and the gummy solids are washed with EtOAc. The combined EtOAc filtrate is washed with 3M HCl, water, NaHCO3, brine, dried (Na2SO4) and concentrated to afford the title crude compound (1.1 g, 85%) which is used in the next step without purification.

Provenance & Evidence