To a solution of potassium bis(trimethylsilyl)amide (30.7 g, 0.15 mol) in tetrahydrofuran (750 mL) at 0° C. was added a solution of methyl 1-(tert-butoxycarbonyl)piperidine-4-carboxylate (25 g, 0.10 mol) from Step A in tetrahydrofuran (250 mL) and the reaction mixture was stirred for 1 h. 5-Bromo-1-pentene (19.4 mL, 0.164 mol) was added and the reaction mixture was allowed to warm to room temperature for 1.5 h. The reaction mixture was then poured into saturated sodium bicarbonate solution and extracted three times with ethyl acetate. The organic layers were combined and washed with brine, dried over sodium sulfate, filtered, and concentrated to afford the title compound (30.9 g) which was used in the next step without further purification.
