CO Enabled Synthesis of Phenanthridinones, Oxindoles, Isoindolinones, and Spirolactams.

We report herein that photoinduced CO 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 CO through homolysis of cesium formate in the presence of light, and the further involvement of CO and the aryl radical was directly proved by trapping with diphenyl styrene and TEMPO.