Trifluoroacetic acid → Benzyl 1,2-dihydrospiro[indole-3,4'-piperidine]-1'-carboxylate

Participants

Reaction Conditions

Reaction Steps

A solution of phenyl hydrazine (1.29 g, 12.0 mmol) and trifluoroacetic acid (3.0 mL) in a 49/1 solution of toluene/acetonitrile (50 mL) is heated at 35° C. 4-Formyl-piperidine-1-carboxylic acid benzyl ester (2.7 g, 10.91 mmol) is dissolved in a 49/1 solution of toluene/acetonitrile (10 mL) and added dropwise to the mixture (WO2005046682). The mixture is stirred at 35° C. overnight. The resulting solution is cooled to 0° C., and methanol (5 mL) is added. NaBH4 (0.619 g, 16.38 mmol) is added slowly to the solution and the mixture is stirred for 45 min. The mixture is washed with aqueous NH4OH (6%, 25 mL) and brine (30 mL), dried over sodium sulfate, and evaporated to dryness to give a yellow solid. The crude solid is recrystallised from EtOAc to give a pale yellow solid (1.25 g, 1st crop). The mother liquor is evaporated and purified by flash chromatography, eluting with hexane:ethyl acetate (8:2) to give the title compound as a pale yellow solid (1.2 g, 2nd crop) with a total yield (2.4 g, 84%). ESI/MS m/z 323 (M+H)+.

Provenance & Evidence