A solution of 1-(1-benzylpiperidin-4-yl)pent-4-en-1-one (6.11 g, 21.3 mmol) and (R)-2-methylpropane-2-sulfinamide (3.62 g, 27.6 mmol) in THF (71 mL, 0.3 M) was treated with titanium (IV) ethoxide (12.6 g, 55.3 mmol) and heated to 70° C. overnight. Because the reaction was incomplete, additional portions of (R)-2-methylpropane-2-sulfinamide (1.81 g, 13.8 mmol) and titanium (IV) ethoxide (6.3 g, 27.7 mmol) were added and the mixture was heated to 75° C. for 6 more hours. The reaction was quenched by pouring it slowly into rapidly stirred saturated aqueous sodium chloride (100 mL) and filtering through Celite. The Celite pad was washed with ethyl acetate (3×) and the combined organics were washed with saturated aqueous sodium chloride, dried over MgSO4, and concentrated in vacuo. The residue was chromatographed on silica gel (60% ethyl acetate in heptane) to afford the desired product (3.24 g, 42%). Rf 0.44 (EtOAc). 1H NMR (CDCl3, 300 MHz) δ 7.34-7.19 (m, 5H), 5.88-5.75 (m, 1H), 5.09-4.94 (m, 2H), 3.50 (d, J=5.5 Hz, 2H), 2.97-2.83 (m, 2H), 2.74-2.70 (m, 1H), 2.55-2.23 (m, 4H), 2.00 (t, J=8.8 Hz, 2H), 1.77-1.63 (m, 4H), 1.23 (s, 9H). ESI MS found for C21H32N2OS m/z [361.4 (M+1)].
