Metal-Free Oxidative Spirocyclization of Alkynes with Sulfonylhydrazides Leading to 3‑Sulfonated Azaspiro[4,5]trienones

A novel
and direct oxidative spirocyclization of arylpropiolamides with sulfonylhydrazides
leading to 3-sulfonated azaspiro­[4,5]­trienones has been developed
under metal-free conditions. The reaction is performed in a tandem
manner constituted by the sequential sulfonylation of alkynes, ipso-carbocyclization, dearomatization, hydration, and oxidation
processes, providing a convenient and efficient approach to various
sulfonated azaspiro­[4,5] trienones of biological importance.