A solution of (R,Z)—N-(1-(1-benzylpiperidin-4-yl)pent-4-enylidene)-2-methylpropane-2-sulfinamide (2.74 g, 7.6 mmol) in THF (130 mL, 0.06 M) was cooled to −78° C. Separately, a 1 M solution of Et2AlCN (11.4 mmol, 11.4 mL) was dissolved in THF (20 mL) and cooled to −78° C. iPrOH (0.64 mL, 8.26 mmol) was added dropwise and the solution was warmed to RT over 20 min, then added dropwise to the sulfinamide solution. The reaction was allowed to warm gradually to RT and stirred overnight. The reaction was quenched with saturated aqueous ammonium chloride (50 mL) and filtered through Celite. The Celite pad was washed with ethyl acetate (3×) and the combined organics were washed saturated aqueous sodium chloride, dried over MgSO4, and concentrated in vacuo. The residue was chromatographed on silica gel (1-9% methanol in dichloromethane and again with 2-5% methanol in ethyl acetate) to afford the desired product (1.99 g, 67%) along with its undesired diastereoisomer (0.46 g, 15%). Rf 0.26 (10% MeOH/CH2Cl2). 1H NMR (CDCl3, 300 MHz) δ 7.31-7.25 (m, 5H), 5.83-5.78 (m, 1H), 5.13-5.03 (m, 2H), 3.51 (d, J=1.5 Hz, 2H), 3.41 (s, 1H), 3.00 (d, J=11.0 Hz, 2H), 2.34-2.29 (m, 2H), 2.05-1.83 (m, 6H), 1.60-1.44 (m, 3H), 1.25 (s, 9H). ESI MS found for C22H33N3OS m/z [388.4 (M+1)].
