To a solution of 1-tosyl-1H-indole-3-carbaldehyde [50562-79-3] (1.90 g, 6.35 mmol) in 1,2-dichloroethane (30 mL) were added tert-butyl 4-allyl-4-aminopiperidine-1-carboxylate [741687-08-1] (1.52 g, 6.35 mmol) and acetic acid (381 mg, 6.35 mmol). The resulting solution was heated at 60° C. for 3 h. Then NaBH(OAc)3 was added and the reaction mixture was heated at 60° C. for 38 h. The mixture was cooled to rt, saturated NaHCO3 solution (30 mL) was added and extracted with ethyl acetate (3×50 mL). The combined organic layers were washed with water and brine, then dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure. The crude mixture was purified by flash-column chromatography over silicagel (eluent: 20% ethyl acetate/hexane) to yield the title compound (2.0 g, 60%). [LCMS RtE=0.34 min, [M+H]+=524.0]
