An effective metal-free C-H amination of N-Ts-2-alkenylanilines by using DDQ as an oxidant has been developed to afford a diverse range of substituted indoles. This protocol is operationally simple and robust, obviates the need of expensive transition-metal catalysts, and offers a broad substrate scope. A mechanism involving a radical cation generated by SET and a migratorial process via a phenonium ion intermediate is proposed.
synthetic route could be readily scaled up to gram quantity without difficulty. Mechanistic studies have revealed that in situ formed selenium electrophile species may be the key intermediate for the selenocyclization process.