N-benzylhydroxylamine hydrochloride → 2-Benzyl-5-(2,5-difluorophenyl)-3-phenylisoxazolidin-5-ol

Participants

Reaction Steps

A mixture of (2E)-1-(2,5-difluorophenyl)-3-phenylprop-2-en-1-one (1-1) (500 mg, 2.05 mmol, 1 equiv) and N-benzylhydroxylamine hydrochloride (327 mg, 2.05 mmol, 1.00 equiv) was heated at reflux in ethanol (10 mL) for 4 h. Additional N-benzylhydroxylamine hydrochloride (327 mg, 2.05 mmol, 1.00 equiv) was added and the mixture was heated at reflux for 16 h. The reaction mixture was partitioned between saturated sodium bicarbonate solution (50 mL) and ethyl acetate (2×50 mL). The combined organic layers were dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (silica, 100% hexanes initially, grading to 100% EtOAc) to give 2-benzyl-5-(2,5-difluorophenyl)-3-phenylisoxazolidin-5-ol (1-2); LRMS m/z (M+H) 368.3 found, 368.1 required. Methanesulfonyl chloride (0.093 uL, 1.20 mmol, 1.11 equiv) was added to a solution of (1-2) (400 mg, 1.09 mmol, 1 equiv) and triethylamine (0.455 mL, 3.27 mmol, 3.00 equiv) in dichloromethane (30 mL) at 0° C. and the resultant mixture was warmed to 23° C. and stirred for 30 min. The reaction mixture was partitioned between saturated sodium bicarbonate solution (50 mL) and dichloromethane (2×50 mL). The combined organic layers were dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (silica, 100% hexanes initially, grading to 100% EtOAc) to give 2-benzyl-5-(2,5-difluorophenyl)-3-phenyl-2,3-dihydroisoxazole (1-3) as a white solid. 1H NMR (300 MHz, CDCl3) δ 7.46-7.21 (m, 11H), 7.02 (m, 2H), 5.76 (t, 1H, J=3.0 Hz), 5.12 (d, 11H, J=2.8 Hz), 4.41 (d, 1H, J=12.8 Hz), 4.10 (d, 1H, J=12.8 Hz). LRMS m/z (M+H) 350.3 found, 350.1 required.

Provenance & Evidence