In 15 ml of tetrahydrofuran, 1.5 g (10.85 mmol) of isophorone was dissolved, and 3.4 g of sodium ethoxide (20% solution in ethanol) (10.0 mmol) was added thereto. To this mixture, 2.6 g (9.87 mmol) of 4-dibutylamino-2-methoxybenzaldehyde in tetrahydrofuran was added dropwise with heating at 50° C., and the mixture was stirred for 4.5 hours. To the mixture, 100 ml of ethyl acetate was added. Washing with a saturated saline solution, drying over anhydrous sodium sulfate, and concentration were performed. The residue was purified by silica gel column chromatography to give 1.7 g of a reddish orange oily matter (yield: 45.0%).
