To a solution of 2-(2-aminoethoxy)ethanol (4.24 mL) in ethanol (30 mL) was added 4-thioxo-1,3-thiazolidin-2-one (5.65 g), and the mixture was stirred at room temperature for 4 hr. To the reaction mixture were added 1-[2,4-bis(trifluoromethyl)benzyl]piperidine-4-carbaldehyde (12 g) and potassium tert-butoxide (4.76 g), and the mixture was stirred at 80° C. for 3 hr. The reaction mixture was cooled to room temperature, saturated aqueous ammonium chloride solution/ethyl acetate were added, and the organic layer was separated, 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 (methanol/ethyl acetate) to give the title compound (4.3 g).
