To a solution of 3.25 g (10.16 mmol) of (5R,6S)-5-(3-chlorophenyl)-6-(4-chlorophenyl)piperidin-2-one (Example 1, Step E) in DMF (150 mL) at 0° C. was added a dispersion of 60% sodium hydride in mineral oil (1.016 g, 25.4 mmol). Evolution of gas was observed. The cloudy reaction mixture was stirred at 0° C. for 20 min before adding 3-bromocyclopent-1-ene (4.48 g, 30.5 mmol). The cloudy reaction mixture warmed to room temperature and stirred at room temperature for 18 h. The reaction was quenched with sat. aq. NH4Cl solution, diluted with EtOAc and the layers were separated. The organic layer was washed with 1M LiCl, sat. aq. NaCl solution, dried over Na2SO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (eluent: 25 to 100% EtOAc in hexanes) to give the title compound as a 5:2 mixture of diastereomers.
