To a suspension of 1-[2,4-bis(trifluoromethyl)benzyl]piperidine-4-carbaldehyde (35.0 g) and 4-(prop-2-yn-1-ylamino)-1,3-thiazol-2(5H)-one (23.9 g) in 2-propanol (400 mL) was added piperidinium acetate (15.0 g) at room temperature. The reaction mixture was stirred at 80° C. for 4 hr and concentrated under reduced pressure. Ethyl acetate was added to the residue, and the precipitate was removed by filtration. Water and ethyl acetate were added to the filtrate, 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/hexane), and the obtained solid was washed with diisopropyl ether to give a solid. The obtained solid was recrystallized from ethyl acetate/heptane/diisopropyl ether to give the title compound (28.9 g).
