To a mixture of propyltriphenylphosphonium bromide (2.34 g), potassium-t-butoxide (62 mg) and sodium amide powder (0.3 g) is added tetrahydrofuran (110 ml) under argon atmosphere and the mixture is stirred at room temperature for 3 hours. To the resulting yellowish red solution is added 1-[1-(4-formylbenzoyl)-4-piperidinyl]-3,4-dihydrocarbostyril (2 g) gradually under ice cooling and the mixture is stirred under the same conditions for 3 hours. The reaction mixture is poured into water and extracted with ethyl acetate/toluene and then dried over sodium carbonate. The resultant is purified by silica gel column chromatography (solvent: n-hexane:ethyl acetate=1:1) to give 1-{1-[4-(1-butenyl)benzoyl]-4-piperidinyl}-3,4-dihydrocarbostyril (2 g).
