To a suspension of 1.81 g (4.8 mmol) of (3S,5R,6S)-3-allyl-5-(3-chlorophenyl)-6-(4-chlorophenyl)-3-methylpiperidin-2-one (Example 71, Step D) in 3-bromopentane (17.6 mL) added 967 mg (60 wt. % in mineral oil, 24.2 mmol) of sodium hydride. The resulting milky white slurry was heated at 120° C. for 20 h, and then more 3-bromopentane (5.1 mL) was added. After an additional 24 h at 120° C., the reaction was cooled to room temperature and quenched with saturated aqueous ammonium chloride. The mixture was extracted with ethyl acetate (3×) and the combined organic layers were dried over Na2SO4, filtered and the filtrate was concentrated. Purification of the residue by flash chromatography on silica gel (2 to 26% EtOAc/hexanes, gradient elution) provided the title compound as a white solid.
