To a solution of 1-[2,4-bis(trifluoromethyl)benzyl]piperidine-4-carbaldehyde (6.64 g) and 4-{[2-(diethylamino)ethyl]amino}-1,3-thiazol-2(5H)-one (5.48 g) in ethanol (98 mL) was added potassium tert-butoxide (2.85 g). The reaction mixture was stirred at 80° C. for 20 min, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (NH, ethyl acetate/hexane). The solvent was evaporated under reduced pressure, the residue was dissolved in ethyl acetate, the solution was washed with water and saturated brine, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (NH, methanol/ethyl acetate) and further silica gel column chromatography (methanol/ethyl acetate) to give the title compound (7.84 g).
