反应详情

To a solution of 3-(ethoxycarbonyl)isoxazole-5-carboxylic acid (2.00 g; 10.80 mmol), triethylamine (1.74 mL; 12.42 mmol) and tert-butanol (2.58 mL; 27.01 mmol) in toluene (25 mL) was added at room temperature diphenylphosphoryl azide (2.74 mL; 12.42 mmol). The solution was stirred at room temperature for 10 min and was heated at 100° C. for 4 h. After evaporation, the residue was purified by flash chromatography on silica gel (eluent: 1 to 6% of ethyl acetate in dichloromethane) to afford 1.47 g (53%) of ethyl 5-(tert-butoxycarbonylamino)isoxazole-3-carboxylate as a white solid.

1. temperaturewas heated at 100° C. for 4 h
2. customAfter evaporation
3. customthe residue was purified by flash chromatography on silica gel (eluent: 1 to 6% of ethyl acetate in dichloromethane)