[Synthesis]
GENERAL STEPS: To a suspension of 1-(benzyloxycarbonyl)piperidin-4-one (4 g, 17.16 mmol), methylamine hydrochloride (1.95 g, 18.88 mmol) and sodium triacetoxyborohydride (5.09 g, 24.02 mmol) in 1,2-dichloroethane (46 mL) was added acetic acid (0.8 mL, 12.7 mmol). The reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the reaction was quenched with saturated aqueous sodium bicarbonate (50 mL) and the organic layer was extracted with dichloromethane (3 x 40 mL). The organic layers were combined, dried with anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to afford the crude product 1-(benzyloxycarbonyl)-4-(methylamino)piperidine (4 g, 100% yield). The product was characterized by 1H NMR (400 MHz, CDCl3): δ 7.31-7.35 (m, 5H), 5.12 (s, 2H), 4.13 (s, 2H), 3.72 (s, 3H), 2.86 (t, J = 10Hz, 1H), 2.56-2.63 (m, 1H), 2.48 (s, 3H), 2.12 (s, 3H) , 1.91 (s, 1H), 1.22-1.39 (m, 2H). |