Metal Free Sulfonylative Spirocyclization of Alkenyl and Alkynyl Amides via Insertion of Sulfur Dioxide.

Herein, we report an efficient synthesis of azaspiro[4,5]‐decanes and azaspiro[4,5]‐trienones by the radical cascade spirocyclization of N‐benzylacrylamides or N‐arylpropiolamides respectively. These reactions proceed under metal free conditions and involve in situ generation of aryl sulfonyl radicals from DABSO and aryl diazonium salts. Furthermore, a catalyst free visible light mediated protocol was developed for the sulfonylative spirocyclization of N‐aryl alkynamides using diaryliodonium salts. The utility of these protocols were justified by the excellent compatability of a wide range of functional groups, good yields and scalablity under mild conditions at room temperature. [ABSTRACT FROM AUTHOR]