Functional Group Migration-Driven Quaternary Carbon Editing via Intramolecular [4+2] Annulation

Abstract

A photocatalytic tandem radical intramolecular [4+2] cyclization of unactivated cyanated alkenes for constructing functionalized benzo[1,6]naphthyridinones through the integration of radical cyano migration and hydrogen atom transfer (HAT) strategies is reported. This protocol uses mild reaction conditions, readily accessible and stable substrates, and a metal-free organic photocatalyst while enabling late-stage functionalization. The mechanistic study reveals that the intramolecular [4+2] cyclization mechanism involves radical addition to an unactivated alkene, followed by 1,4-cyano migration, 1,6-HAT, and a subsequent intramolecular 6-endo-trig radical cyclization process.