Boron Trichloride → (3S)-3-ethyl-7-fluoro-4-[(4-hydroxyphenyl)sulfonyl]-1-methyl-3,4-dihydroquinoxalin-2(1H)-one

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Reaction Conditions

Reaction Steps

A solution of (3S)-3-ethyl-7-fluoro-4-[(4-methoxyphenyl)sulfonyl]-1-methyl-3,4-dihydroquinoxalin-2(1H)-one (0.27 g, 0.7 mmol)) and tetrabutylamonium iodide (0.77 g, 2.09 mmol) in methylene chloride (20 mL) was cooled to −78° C. and treated with a 1M solution of boron trichloride in methylene chloride (3.5 mL, 3.5 mmol) via syringe. The cooling bath was removed and the solution was stirred at 25° C. for 3 hours. The reaction was quenched with a saturated aqueous solution of ammonium chloride. The organic phase was separated, dried over magnesium sulfate and concentrated in vacuo. The crude oil was purified via flash column chromatography (SiO2, 40% ethyl acetate:hexane) to afford 0.2 g (78%) of (3S)-3-ethyl-7-fluoro-4-[(4-hydroxyphenyl)sulfonyl]-1-methyl-3,4-dihydroquinoxalin-2(1H)-one as white solid. MS (ESI) m/z 365 ([M+H]+); MS (ESI) m/z 363 ([M−H]−); Anal. Calcd for C17H17FN2O4S: C, 56.03; H, 4.70; N, 7.69. Found: C, 56.12; H, 4.03; N, 7.45.

Provenance & Evidence