A mixture of 5-chlorosalicylic acid (173 mg, 1 mmol), 3,5-bis(trifluoromethyl)-N-methylaniline (243 mg, 1 mmol), phosphorus trichloride (44 μl, 0.5 mmol) and monochlorobenzene (5 mL) was refluxed for 3 hours under argon atmosphere. After the reaction mixture was cooled to room temperature, n-hexane (50 mL) was added, and the separated crude crystal was filtered and dissolved in ethyl acetate (50 mL). After the ethyl acetate solution was washed with water and brine one after another, dried over anhydrous sodium sulfate, the solvent was evaporated under reduced pressure. The obtained residue was purified by column chromatography on silica gel (n-hexane:ethyl acetate=2:1) to give the title compound (75 mg, 18.9%) as a white crystal.
