To a suspension of 4-{[2-(2-hydroxyethoxy)ethyl]amino}-1,3-thiazol-2(5H)-one (1.58 g) and 1-[2,4-bis(trifluoromethyl)benzyl]piperidine-4-carbaldehyde (2.89 g) in 2-propanol (30 mL) was added piperidinium acetate (1.12 g). The reaction mixture was stirred at 80° C. for 8 hr and concentrated. Water and ethyl acetate were added to the residue, and the mixture was extracted with ethyl acetate. The extract was washed with 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 (ethyl acetate/methanol) to give an oil. The oil was diluted with ethyl acetate (9 mL) and heptane (45 mL). The mixture was gradually cooled from 50° C. to 0° C., and the mixture was stirred for 6 hr. The precipitate was collected by filtration, and the obtained solid was washed with a mixed solution of ethyl acetate and heptane to give a white solid. The obtained white solid was recrystallized from ethyl acetate/heptane to give the title compound (2.53 g).
