[CH:1]([CH:3]1[CH2:8][CH2:7][N:6]([C:9]2[CH:14]=[CH:13][C:12]([NH:15][C:16](=[O:22])[O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[CH:11][CH:10]=2)[CH2:5][CH2:4]1)=O.[CH2:23]([NH2:25])[CH3:24].C([BH3-])#N.[Na+]>CO.O.[Cl-].[Zn+2].[Cl-]>[CH2:23]([NH:25][CH2:1][CH:3]1[CH2:8][CH2:7][N:6]([C:9]2[CH:14]=[CH:13][C:12]([NH:15][C:16](=[O:22])[O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[CH:11][CH:10]=2)[CH2:5][CH2:4]1)[CH3:24]To a suspension of tert-butyl [4-(4-formyl-piperidin-1-yl)-phenyl]carbamate (0.20 g, 0.66 mmol) in methanol (5 mL) is added ethylamine (2.0 M solution in tetrahydrofuran, 0.66 mL, 1.3 mmol). The reaction mixture is stirred for 20 minutes and then a mixture of zinc chloride (53 mg) and sodium cyanoborohydride (50 mg) in methanol (2 mL) is added in a dropwise fashion. After stirring overnight 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-ethylaminomethyl-piperidin-1-yl)-phenyl]-carbamate as a foam (0.27 g, >100%).
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