Synthesis of 1,2-Benzisoxazoles by 1,3-Dipolar Cycloaddition

Significance

The synthesis of benzisoxazoles 3 via the 1,3-dipolar cycloaddition of benzyne and nitrile oxides, generated in situ from ortho-(tri­methylsilyl)phenyl triflate (1) and hydroximoyl chlorides 2 is reported. Optimization of the reaction conditions showed that TBAF was suitable as both a fluorine source and nucleophilic base for the simultaneous generation of both reactive intermediates in one pot. The reaction is tolerant of both electron-rich and electron-poor aryl hydroximoyl chlorides with good to excellent yields (75-99%) observed in all cases. One example of a challenging aliphatic nitrile oxide substrate was also reported, albeit in modest yield (50%).