Citric Acid → tert-butyl 6-{2-[(phenylsulfonyl)amino]ethyl}-1,4,5,6-tetrahydroazepino[4,5-b]indole-3(2H)-carboxylate

Participants

Reaction Steps

tert-Butyl 6-(2-aminoethyl)-1,4,5,6-tetrahydroazepino[4,5-b]indole-3(2H)-carboxylate (0.0403 g, 0.122 mmol) was dissolved in THF (2 mL) at rt under N2. Diisopropylethylamine (0.043 mL, 0.0316 g, 0.245 mmol, 2.00 equiv.) and benzenesulfonyl chloride (0.023 mL, 0.0324 g, 0.183 mmol, 1.50 equiv.) were added, then the reaction mixture was stirred for 19 h. Citric acid (10%) was added and the reaction mixture was stirred for 15 min. The reaction mixture was extracted with EtOAc, and the organic layer was washed sequentially with 10% citric acid, saturated aqueous NaHCO3 and brine. The organic layer was dried over MgSO4, filtered, and concentrated. The crude product (0.0649 g) was chromatographed (SiO2 25 g, eluted with 2:1 hexane:EtOAc) to give tert-butyl 6-{2-[(phenylsulfonyl)amino]ethyl}-1,4,5,6-tetrahydroazepino[4,5-b]indole-3(2H)-carboxylate (0.0430 g) in 75% yield. 1H NMR (300 MHz, CDCl3) δ 1.46, 1.52, 2.95-3.02, 3.22-3.30, 3.63-3.75, 4.24-4.31, 4.63, 4.79, 7.09-7.26, 7.45-7.51, 7.48, 7.58, 7.79; MS (ESI+) for C25H31N3O4S m/z 470.0 (M+H)+.

Provenance & Evidence