To a solution of ethyl diethylphosphonoacetate (2.74 ml) in tetrahydrofuran (50 ml), sodium hydride (60%, oily, 552 mg) was added at 0° C., and then the solution was stirred at room temperature for 30 minutes. To the reaction mixture, a solution of 1-(4-benzyloxybenzyl)-3-(4-benzyloxybenzyloxy)-1H-pyrazol-4-carbaldehyde (6.31 g) in tetrahydrofuran (100 ml) was added slowly, and the solution was stirred at room temperature for 15 minutes. The reaction mixture was poured into water, which was extracted with ethyl acetate. The ethyl acetate layer was washed with dilute hydrochloric acid, then, with saturated aqueous sodium chloride solution, and dried (MgSO4) and concentrated. The obtained crystals were collected by filtration, and ethyl 3-[1-(4-benzyloxybenzyl)-3-(4-benzyloxybenzyloxy)-1H-pyrazol-4-yl]propionate (6.79 g, yield: 95%) was obtained. This was recrystallized from ethyl acetate-hexane. Melting point: 98–99° C.
