Relay Photocatalyzed Reductive Cleavage of C_sp²–I To Establish Radical Cyclization/Coupling between O-Tethered Iodoarenes with Cyanoarenes

The activation of C_sp²-I bonds in iodobenzenes and their derivatives is a highly valuable research topic. Most known methods predominantly rely on transition metal catalysis, which often necessitates the use of oxidants, additives, ligands, and harsh reaction conditions. Photocatalysis has emerged in the last decades as an excellent alternative to drive intriguing organic transformations via various chemical bond cleavages, while photocontrolled direct C_sp²-I bond cleavage in O-tethered iodoarenes is rare due to its high reduction potential. To address this challenge, we have provided a relay reductive photocatalysis strategy to amplify the reduction function of low reduction potential photocatalysts using cyanoalkenes as photoredox mediators to achieve C_sp²-I bond cleavage in O-tethered iodoarenes. Moreover, it is noteworthy that cyanoarenes are simultaneously involved as coupling reagents in the radical cyclization/coupling process between O-tethered iodoarenes and cyanoarenes to form benzo-fused oxygen-containing heterocyclic compounds with different scaffolds.