Visible-Light Excitation of Quinolinone-Containing Substrates Enables Divergent Radical Cyclizations

Reported herein is the photochemical activity of quinolinone-containing substrates that directly reach an excited state upon light absorption to trigger radical-based bond-forming processes. The presented transformations allow divergent construction of valuable dihydro- or tetrahydrophenanthridin-6(5H)-ones through the generation of S- or P-centered radicals, subsequent radical addition, cyclization, and a hydrogen atom transfer/electron transfer sequence. This strategy demonstrates the potential generality of quinolinone-tethered substrates to directly participate in the photoexcitation for the development of useful synthetic methods.