Synthesis of 1,2-Benzisoxazoles via a 1,3-Dipolar Cycloaddition

Significance

Reported is the synthesis of 1,2-benzisoxazoles through the 1,3-dipolar ­cycloaddition of benzyne and nitrile oxides, which were themselves formed in situ by heating anthranilic acid and α-chloro oximes, respectively. In analogy to previous work by the same researchers, heating the reaction using a microwave reactor was found to be hugely beneficial. The authors postulate that this is due to comparable rates of formation of the highly reactive benzyne and nitrile oxides. Conventional heating in a round-bottomed flask gave a poor yield of the benzisoxazole. Remarkably, performing the reaction using conventional heating in a sealed tube gave a similar yield to that obtained with microwave heating, which was rationalized as a pressure effect.