To a solution of 1-[2,4-bis(trifluoromethyl)phenyl]piperidine-4-carbaldehyde (1.61 g) in 2-propanol (20 mL) were added 4-(prop-2-yn-1-ylamino)-1,3-thiazol-2(5H)-one (1.15 g) and piperidinium acetate (0.72 g). The reaction mixture was stirred at 80° C. for 1 hr, and the solvent was evaporated under reduced pressure. Water was 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/hexane), and recrystallized from ethyl acetate/heptane to give the title compound (1.45 g).
