1,1'-Carbonyldiimidazole → (4R,5R)-4-(2-bromo-5-fluoropyridin-4-yl)-5-(2,5-difluorophenyl)oxazolidin-2-one

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Reaction Steps

Optically-enriched tert-butyl (1R,2R)-1-(2-bromo-5-fluoropyridin-4-yl)-2-(2,5-difluorophenyl)-2-hydroxyethylcarbamate (253 mg, 0.283 mmol) was dissolved in trifluoroacetic acid (10% in dichloromethane, 10 mL) and stirred at room temperature overnight. In the morning, the reaction was concentrated and loaded onto a strong cation exchange cartridge. The cartridge was flushed with several volumes of methanol which were discarded. The crude aminoalcohol was eluted with 2M ammonia in methanol and concentrated to give 53 mg as a solid. The crude solid was dissolved in tetrahydrofuran (5 mL), cooled to 0° C., and treated with carbonyldiimidazole (45.9 mg, 0.283 mmol). After 5 min, the ice bath was removed, and stirring continued for 1 h. The reaction was quenched by addition of 2M ammonia in methanol. The reaction was concentrated and purified by column chromatography (25%→50% EtOAc/Hex) to give 20 mg (9.5%). Mass spec.: 373.1 (MH)+.

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