Solution-Phase Synthesis of a Diverse Library of Benzisoxazoles Utilizing the [3 + 2] Cycloaddition of in Situ-Generated Nitrile Oxides and Arynes

A library of benzisoxazoles has been synthesized by the [3 + 2] cycloaddition of nitrile oxides with arynes and further diversified by acylation/sulfonylation and palladium-catalyzed coupling processes. The eight key intermediate benzisoxazoles have been prepared by the reaction of o-(trimethylsilyl)aryl triflates and chlorooximes in the presence of CsF in good to excellent yields under mild reaction conditions. These building blocks have been used as the key components of a diverse set of 3,5,6-trisubstituted benzisoxazoles.