5-Chloro-1-methyl-3-trifluoromethylpyrazole-4-carboxylic acid (230 mg, 1 mmol) was dissolved in thionyl chloride (2 ml), and the solution was stirred at reflux temperature for 2 hours. After concentration under reduced pressure, the resulting acid chloride was added to a solution of 2-(1,3-dimethylbutyl)-4-[2,2,2-trifluoro-1-(trifluoromethyl)ethyl]aniline (330 mg, 1 mmol) and triethylamine (150 mg, 1.5 mmol) in tetrahydrofuran (10 ml) under ice-cooling, and the resulting mixture was stirred at room temperature for 2 hours. The reaction mixture was diluted with ethyl acetate and then washed with water. The organic layer was dried over anhydrous magnesium sulfate and then concentrated under reduced pressure, and the resulting residue was separated and purified by silica gel column chromatography (hexane:ethyl acetate=3:1) to obtain 233 mg of the desired compound.
