To a solution of 1.5 g (4.7 mmol) of (5R,6S)-5-(3-chlorophenyl)-6-(4-chlorophenyl)piperidin-2-one (Example 1, Step E) in 9.4 mL of DMF was added sodium hydride (60% suspension in mineral oil, 244 mg, 6.1 mmol) at 0° C. The reaction was stirred at 0° C. for 20 min and then treated with cyclopropylmethyl bromide (759 μl, 5621 μmol). After being stirred at 25° C. for 5 h, the reaction was quenched (sat. aqueous NH4Cl), extracted (2×EtOAc). The combined organic layers were washed with sat. aq. NaCl and NaHCO3— solutions, dried over Na2SO4, filtered and the filtrate was concentrated under reduced pressure. Purification of the residue by flash chromatography on silica gel (30 to 50% EtOAc/hexanes, gradient elution) provided the title compound as a colorless foam.
