To a suspension of tert-butyl [4-(4-formyl-piperidin-1-yl)-phenyl]carbamate (0.30 g, 1.0 mmol) in methanol (5 mL) is added N,N-dimethylethylenediamine (0.18 g, 2.0 mmol). The reaction mixture is stirred for 10 minutes and then a mixture of zinc chloride (82 mg, 0.6 mmol) and sodium cyanoborohydride (75 mg, 1.2 mmol) in methanol (2 mL) is added in a dropwise fashion. After stirring for two hours at room temperature, the reaction mixture is diluted with water and extracted 3× with ethyl acetate. The combined extracts were washed once with saturated aqueous sodium chloride solution, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to give tert-butyl {4-[4-({[2-(dimethylamino)ethyl]amino}methyl)piperidin-1-yl]phenyl}carbamate as a white foam (0.4 g, 100%).
