Methylative Cyclization of α-Substituted Styrenes Mediated by Excited Dibenzothiophene S-Oxide

Radical-mediated carbofunctionalization of olefins with alkyl radicals has been extensively studied as a powerful tool for skeletal construction in organic synthesis. However, methyl-functionalization reactions to introduce the smallest carbon substituent remain relatively unexplored because methods for generating methyl radicals are limited.In this study, we found that excited dibenzothiophene S-oxide promotes methyl radical generation from DMSO, enabling methylative cyclization of olefins to afford a variety of heterocycles. This transformation proceeds under mild conditions using an excited sulfoxide as the oxidant without relying on explosive peroxides.