After dissolving 298 mg of 2-(2-bromophenyl)-1-[1-(3-tert-butoxy-2-pyrazinylmethyl)piperidin-4-yl]ethanone in 2 ml of N,N-dimethylformamide, 235 mg of zinc cyanide and 77 mg of tetrakis(triphenylphosphine)palladium(0) were added and the mixture was stirred overnight at 100° C. A 1N sodium hydroxide solution was added to the reaction mixture and extraction was performed with ethyl acetate. The organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate, and then the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (solvent: n-hexane/ethyl acetate) to obtain the title compound (90 mg, 34% yield).
