To a −78 □C solution of benzyl 4-(2-ethoxy-2-oxoethyl)piperidine-1-carboxylate (5.02 g, 16.4 mmol) in THF (90 mL) was added lithium hexamethyldisilazide (1.0 M in THF, 18.1 mL, 18.1 mmol). After 1 h allyl bromide (2.19 g, 18.1 mmol) was added, the reaction stirred at this temperature for 0.5 h, then warmed to 25 □C. After 3 h the reaction was quenched by the addition of saturated aqueous ammonium chloride and extracted with ethyl acetate (2×). The combined organic layers were dried over MgSO4, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel chromatography, eluting with a gradient of 0 to 60% EtOAc:hexanes to give the title compound (4.08 g). MS: m/z=346.1 (M+1).
