(4R,5S)-(+)-4-Methyl-5-phenyl-2-oxazolidinone → (4R,5S)-4-methyl-3-((2R)-2-methyl-4,4,4-trifluorobutyryl)-5-phenyl-2-oxazolidinone

Participants

Reaction Steps

To a mixture of (4R,5S)-(+)-4-methyl-5-phenyl-2-oxazolidinone (3.22 g) and tetrahydrofuran (35 ml) at -70° C., under nitrogen was added 1.625M n-butyllithium (12.31 mL) and the mixture was stirred for 15 min. 2-Methyl-4,4,4-trifluorobutyryl chloride (3.5 g) was added to the reaction mixture which was stirred for 15 min at -70° C. and then at 0° C. for 1 hour. The reaction was quenched with ammonium chloride and extracted with ethyl acetate. The organic phase was washed (saturated NaHCO3, brine) and dried (MgSO4). Evaporation and flash chromatography, eluting with 5:95 then 1:9 ethyl acetate:petroelum ether, afforded the two diastereomeric products. Recrystallization from hexane at 20° C. gave (4R,5S)-4-methyl-3-((2R)-2-methyl-4,4,4-trifluorobutyryl)-5-phenyl-2-oxazolidinone (2.376 g, 42%) as colorless needles; mp 72.5°-73.5° C.; TLC, Rf =0.43, 1:9 ethyl acetate:petroleum ether; MS(CI): 316 (M+H).

Provenance & Evidence