Dual-Role Halogen-Bonding-Assisted EDA-SET/HAT Photoreaction System with Phenol Catalyst and Aryl Iodide: Visible-Light-Driven Carbon-Carbon Bond Formation.

Electron donor-acceptor (EDA) complex-mediated single-electron transfer (SET) is a crucial method for generating carbon radicals. Hydrogen atom transfer (HAT) enables the direct generation of alkyl radicals. We report a dual-role EDA-SET/HAT photoreaction system for carbon-carbon bond formation using a phenol catalyst and aryl iodide. This system facilitates addition of alkyl radicals generated from ethers, amide, sulfide, and cycloalkane to arenes. Mechanistic studies revealed that EDA complex formation is mediated by halogen bonding between phenoxide and aryl iodide. Irradiation of the EDA complex with visible light generates an aryl radical, which abstracts a hydrogen atom from an sp 3 carbon to form an alkyl radical.