A solution of p-toluenesulfonylmethylisocyanide (3.08 g) in dimethoxyethane (15 ml) was added to a mixture of potassium t-butoxide (3.37 g) and dimethoxyethane (15 ml) at −78° C., and the resultant was stirred for 5 minutes. A solution of 1-(4-benzyloxybenzyl)-3-(4-fluorophenyl)-1H-pyrazole-4-carbaldehyde (5.80 g) in dimethoxyethane (30 ml) was added to the mixture. After stirring at the same temperature, the mixture was stirred for 1 hour while raising the temperature. Methanol (45 ml) was added to the mixture, which was refluxed for 1 hour. After cooling, the reaction mixture was poured into saturated aqueous ammonium chloride solution, which was extracted with ethyl acetate. The ethyl acetate layer was washed with saturated aqueous sodium chloride solution, dried (MgSO4), and concentrated. The residue was subjected to silica gel column chromatography to obtain 1-(4-benzyloxybenzyl)-3-(4-fluorophenyl)-1H-pyrazol-4-ylacetonitrile (4.52 g, yield 76%) as colorless crystals from the fraction eluted with ethyl acetate-hexane (1:2, volume ratio). This was recrystallized from ethyl acetate-hexane. Melting point: 86–87° C.
