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.