To a solution of 4-[5-(3,5-dichloro-phenyl)-5-trifluoromethyl-4-methylsulfanyl-4,5-dihydro-isoxazol-3-yl]-2-methyl-benzoic acid methyl ester (428 mg) in dichloromethane (15 ml) was added 3-chloroperoxybenzoic acid (“MCPBA”) (500 mg) dropwise at ambient temperature. The reaction mixture was stirred for 5 hours then more 3-chloroperoxubenzoic acid (“MCPBA”) (300 mg) was added dropwise. The reaction mixture was allowed to stand at ambient temperature for 3 days. Then more 3-chloroperbenzoic acid (“MCPBA”) (100 mg) was added dropwise. The reaction mixture was allowed to stand at ambient temperature for another day. The reaction mixture was then treated with aqueous sodium metabisulfite (saturated) and extracted twice with dichloromethane. The combined organic phases were washed with brine, dried over sodium sulfate and concentrated. The residue was purified by chromatography on silica gel (eluent: heptane/diethyl ether 6:4) to give 4-[5-(3,5-dichloro-phenyl)-4-methanesulfonyl-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-2-methyl-benzoic acid methyl ester (300 mg) as white foam. 1H-NMR (CDCl3, 400 MHz): 8.01-7.52 (m, 6H), 5.28 (s, 1H), 3.91 (s, 3H), 2.65 (s, 3H), 2.47 (s, 3H) ppm.
