Visible-Light Photoredox Catalysis: Enabling [2π+2σ] Dearomative Cycloaddition of Unactivated Indoles with Bicyclo[1,1,0]butyl Tethers

Dearomative [2+2] photocycloadditions of indoles with unsaturated functionalities via the energy transfer (EnT) process have been the subject of extensive investigation. In this work, we developed a dearomative [2π+2σ] photocycloaddition of unactivated indoles tethered with bicyclo[1,1,0]butyl units (BCBs) through photoredox catalysis, which enabled the construction of a series of N-heteropolycyclic three-dimensional (3D) molecular architectures. The photoredox catalysis mechanism has been comprehensively validated by a series of control experiments, Stern-Volmer quenching assays, and competition experiments. This protocol offers a novel catalytic pathway that is inaccessible via the EnT route and features a broad substrate scope, a simple reaction system, and straightforward operational procedures.