Reaction Steps
To a 0.25-L flask equipped with a nitrogen inlet, a thermocouple, and a magnetic stirrer were added 2-(azetidin-3-ylidene)acetonitrile hydrochloride (2a, 4.5 g, 34.46 mmol), 1-(3-fluoro-2-(trifluoromethyl)isonicotinoyl)piperidin-4-one (7, 10 g, 34.46 mmol, 1.0 equiv), and methylenechloride (100 mL) at ambient temperature and the resulting mixture was then treated with sodium triacetoxyborohydride (14.6 g, 68.93 mmol, 2.0 equiv) at ambient temperature. The reaction mixture was stirred at ambient temperature for 2 hours before being quenched with saturated sodium bicarbonate (NaHCO3) aqueous solution (50 mL). The two phases were separated and the aqueous phase was extracted with dichloromethane (200 mL). The combined organic phase was washed with water (50 mL) and brine (50 mL) and concentrated under reduced pressure to afford the crude desired product (10), which was purified by column chromatography (SiO2, O-10% of ethyl acetate in hexane gradient elution) to afford 2-(1-(1-(3-fluoro-2-(trifluoromethyl)isonicotinoyl)piperidin-4-yl)azetidin-3-ylidene)acetonitrile (10, 9.5 g, 12.7 g theoretical, 74.8%) as a white solid. For 10: 1H NMR (400 MHz, CDCl3) δ 8.57 (d, J=4.7 Hz, 1H), 7.54 (t, J=4.6 Hz, 1H), 5.29 (p, J=2.4 Hz, 1H), 4.18-4.08 (m, 1H), 4.08-4.03 (m, 2H), 3.98-3.94 (m, 2H), 3.57-3.39 (m, 2H), 3.17-3.04 (m, 1H), 2.56 (tt, J=7.4, 3.5 Hz, 1H), 1.86-1.77 (m, 1H), 1.75-1.64 (m, 1H), 1.54-1.43 (m, 1H), 1.43-1.31 (m, 1H) ppm; 13C NMR (101 MHz, CDCl3) δ 161.34, 160.73, 152.62 (d, J=269.1 Hz), 145.75 (d, J=6.1 Hz), 136.73 (qd, J=36.1, 12.0 Hz), 134.56 (d, J=16.9 Hz), 126.89, 120.58 (qd, J=275.0, 4.9 Hz), 115.11, 92.04, 62.05, 60.57 (2C), 44.47, 39.42, 29.38, 28.47 ppm; C17H16F4N4O (MW 368.33), LCMS (EI) m/e 369 (M++H).
