Step A: Synthesis of 4-amino-1-benzylpiperidine-4-carbonitrile
To a solution of ammonium chloride (17.3 g, 323 mmol) in water (200 mL) was sequentially added 25% ammonia (25 mL, 332 mmol) and 1-benzylpiperidin-4-one (11.43 g, 60 mmol). The resulting mixture was stirred at room temperature for 20 minutes, followed by the addition of sodium cyanide (14.7 g, 300 mmol) in batches over 15 minutes. The reaction mixture was stirred at room temperature for 24 hours and then partitioned between water (200 mL) and dichloromethane (2 x 200 mL). The organic phases were combined, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give the crude product. The crude product was purified by fast column chromatography (silica gel, elution gradient: 50% ethyl acetate/heptane to 100% ethyl acetate) to afford 4-amino-1-benzylpiperidine-4-carbonitrile (6.15 g, 47% yield).
1H NMR (300 MHz, CDCl3) δ ppm: 1.69-1.86 (m, 4H), 2.00 (dt, J = 13.1, 2.1 Hz, 2H), 2.27-2.45 (m, 2H), 2.83 (dt, J = 12.4, 3.6 Hz, 2H), 3.55 (s, 2H), 7.21-7.39 (m. 5H); MS m/z 216 (M + H)+.
