In a stream of argon, to 30 ml of tetrahydrofuran was added 3.17 g of phenyllithium (19% solution in dibutylether) (7.16 mmol), and 2.57 g (6.5 mmol) of 2-thenyl triphenylphosphonium chloride was added thereto under ice cooling. Next, 3.17 g (6.5 mmol) of 4-dibutylamino-2-tert-butyldiphenylsiloxybenzaldehyde was dissolved in tetrahydrofuran and added dropwise. The mixture was stirred for 3 hours. After the reaction mixture was poured into water, extraction with ethyl acetate, 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 2.32 g of a yellowish brown oily matter (yield: 62.9%).
