CO₂^•– Enabled Synthesis of Phenanthridinones, Oxindoles, Isoindolinones, and Spirolactams

We report herein that photoinduced CO₂^•- enabled reductive intramolecular radical cyclization of a variety of aryl iodide derivatives to the corresponding phenanthridinone, oxindole, isoindolinone, and spirolactam derivatives in good yields. Preliminary mechanistic studies suggested the generation of CO₂^•- through homolysis of cesium formate in the presence of light, and the further involvement of CO₂^•- and the aryl radical was directly proved by trapping with diphenyl styrene and TEMPO.