To a mixture of the crude product of 1-[4-bromo-2-(4,4-dimethylcyclohexyl)phenyl]piperazine produced in Example (57a) (1.21 g), butyraldehyde (0.35 mL, 3.98 mmol), acetic acid (0.1 mL, 3.32 mmol) and tetrahydrofuran (8 mL) was added sodium triacetoxyborohydride (1.1 g, 4.98 mmol), followed by stirring for 2 hours and 10 minutes at room temperature. Saturated aqueous solution of sodium hydrogencarbonate was added to the reaction mixture and extraction was performed with ethyl acetate. The separated organic layer was washed with water and brine in that order and then dried over anhydrous sodium sulfate. The desiccant was filtered off and the filtrate was concentrated under reduced pressure. The resultant residue was purified by NH silica gel column chromatography (ethyl acetate/hexane) to give 901 mg of the title compound as a yellow oil.
