Visible-Light-Promoted Selenylative Radical Cyclization of 2-Vinyl--Aryl Imines to 3-Indoles via Oxygen Photosensitization.

A visible-light-promoted tandem selenylative radical cyclization of 2-vinyl--aryl imines to 3-indoles was developed involving a series of selenyl radical addition, 5- cyclization, and redox steps. The roles of triplet oxygen (O) and rhodamine-sensitized singlet oxygen (O) under visible light were investigated, revealing that the competing selenol-mediated hydrogen atom transfer process was effectively suppressed. The pivotal role of O in this tandem selenylative radical cyclization provides valuable insight into photocatalyst-controlled aerobic radical processes under visible light.