N-Fluorobenzenesulfonimide → 4-[5-(3,5-Dichloro-phenyl)-4-fluoro-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-2-methyl-benzoic acid tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

To a solution of 4-[5-(3,5-dichloro-phenyl)-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-2-methyl-benzoic acid tert-butyl ester (preparation of similar compounds described in, for example, EP 1,731,512) (500 mg) in tetrahydrofuran (6 ml) that was stirred at −78° C. for 15 minutes under argon, was slowly added lithium bis(trimethylsilyl)amide (“LiHMDS”) (1M in hexane) (1.1 ml). The reaction mixture was stirred at −78° C. for 1.5 hours. Then N-fluorobenzenesulfonimide (“NFSI”) (433 mg) was added quickly and the reaction mixture was stirred at −78° C. for 2 hours. The reaction was quenched by addition of aqueous ammonium chloride (saturated) at −78° C. tert-Butyl methyl ether (“TBME”) was added and the phases were separated. The organic layer was washed successively with aqueous ammonium chloride (saturated) and brine, dried over magnesium sulfate and concentrated. The residue was purified by column chromatography on silica gel (eluent: dichloromethane/heptane 1:2) to give 4-[5-(3,5-dichloro-phenyl)-4-fluoro-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-2-methyl-benzoic acid tert-butyl ester (200 mg) as a colorless oil.

Provenance & Evidence