Hydroxylamine → tert-butyl 4-[(5S)-5-(3,5-dichloro-4-fluoro-phenyl)-5-(trifluoromethyl)-4H-isoxazol-3-yl]-2-methyl-benzoate

Participants

Reaction Conditions

Reaction Steps

A 1500 mL reaction-vessel was charged at room temperature with 1-Anthracen-9-ylmethyl quininium chloride (2.93 g, 5.32 mmol) and tert-butyl 4-[(E)-3-(3,5-dichloro-4-fluoro-phenyl)-4,4,4-trifluoro-but-2-enoyl]-2-methyl-benzoate (12.7 g, 26.6 mmol) and dissolved in chloroform (700 mL). The mixture cooled down to −20° C. Then, a solution hydroxylamine (50 mass % in water, 3.3 mL) in water (16.7 mL) and cesium hydroxide (10.8 g, 71.8 mmol) in water (20 mL) were added simultaneously dropwise to the reaction mixture over 12 min. After the addition the reaction was kept 1.5 h at −20° C. after which time the conversion was complete. The reaction was brought to room temperature diluted with dichloromethane and washed three times with water. The organic phase was dried over MgSO4 and evaporated to yield 24.2 g of the crude title product. The product was purified over a silica gel column (eluent: EtOAc/Heptane) to obtain 12.6 gr of the title product.

Provenance & Evidence