Fragmentation of Isoxazolones to Alkynes Enabled by Anomeric Amides

Over the past few years, isodiazenes have reemerged as an important class of intermediates with substantial synthetic potential. The most direct route to these reactive species is via reactions of N-nucleophiles with nitrenium ion precursors (e.g., anomeric amides). While emerging methodologies are almost exclusively focused on amine-derived isodiazenes, analogous transformations based on other nitrogen functionalities (e.g., oximes, heterocycles) are largely overlooked. Herein, we present evidence that the reactivity of nitrenium ion precursors can be expanded beyond its current scope, supported by the development of an unprecedented reaction between anomeric amides and isoxazol-5-ones. This unorthodox transformation provides an operationally simple, scalable, and highly chemoselective route to challenging sterically hindered alkynes. Moreover, we demonstrate that anomeric amides can behave as surrogates of nitrosonium cation.