A mixed suspension of 69 mg (0.461 mmol) of 5-difluoromethyl-2-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one (produced in the same manner as in Intermediate Production Example), 12 mg (0.508 mmol) of lithium hydroxide, 14 mg (0.092 mmol) of sodium iodide and 3 ml of toluene was stirred for 2 hours while heating under reflux. Toluene was distilled off under reduced pressure, 3 ml of anhydrous 1,4-dioxane was added to the residue under nitrogen atmosphere, then, 100 mg (0.461 mmol) of 2-methyl-5-phenylbenzyl chloride was added. The reaction solution was stirred for 18 hours while heating under reflux, then, concentrated. Ethyl acetate was added to the residue, the mixture was washed with water, then, washed with saturated saline, and dried over anhydrous magnesium sulfate, then, concentrated. The residue was subjected to silica gel thin layer chromatography (eluant: hexane/ethyl acetate=3/1 (v/v)), to obtain 61 mg of 5-difluoromethyl-2-methyl-4-(2-methyl-5-phenylbenzyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (Compound 1) and 11 mg of 3-difluoromethyl-1-methyl-5-(2-methyl-5-phenylbenzyloxy)-1H-1,2,4-triazole as a by-product.
