Sodium borohydride (0.24 g) is added to an ice-cold solution of 4-[2-(5-bromo-2-chloro-pyridin-4-yl)-acetyl]-piperidine-1-carboxylic acid tert-butyl ester (1.65 g) in tetrahydrofuran (40 mL) and water (10 mL). The resulting mixture is stirred for 0.5 h. 2 N aqueous citric acid solution is added and the mixture is extracted with ethyl acetate. The combined extracts are washed with aqueous NaHCO3 solution and brine, dried (MgSO4), and concentrated. The residue is chromatographed on silica gel (cyclohexane/ethyl acetate 65:35) to give the title compound. Mass spectrum (ESI+): m/z=419/421/423 (Cl+Br) [M+H]+.
