O=[C:2]1[CH2:7][CH2:6][N:5]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:4][CH2:3]1.[CH2:15]([NH2:22])[C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1.CC(O)=O.[BH3-]C#N.[Na+]>CO>[CH2:15]([NH:22][CH:2]1[CH2:7][CH2:6][N:5]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:4][CH2:3]1)[C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1To a solution of tert-butyl 4-oxopiperidine-1-carboxylate (10.0 g, 50.2 mmol) and benzylamine (2.7 mL, 25.1 mmol) in MeOH (30 mL) was added HOAc (1.9 mL, 32.6 mmol), followed by NaCNBH3 (2.0 g, 32.6 mmol) and the reaction was stirred at room temperature overnight. The resulting mixture was quenched with H2O (5 mL) and concentrated in vacuo. The residue was diluted with 0.1 N HCl and washed with Et2O. The aqueous layer was then basified with 2 N NaOH and extracted with Et2O. The organics were washed with brine, dried over anhydrous Na2SO4, filtered, and concentrated in vacuo, to afford tert-butyl 4-(benzylamino)piperidine-1-carboxylate (8.1 g, 56%).
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