Visible-Light-Catalyzed Cascade Radical Cyclization for 3-Substituted Chroman-4-ones

A visible-light-catalyzed, additive-free cascade radical cyclization/addition reaction is described for the synthesis of 3-substituted chroman-4-one derivatives at room temperature. This process, initiated by the photocatalytic excitation-driven reduction of ketoxime esters, generates nitrogen-centered radicals that undergo β-C-C bond cleavage to form carbon-centered radicals. These intermediates thereafter participate in a rapid intramolecular cyclization, producing chroman-4-one radicals, which subsequently undergo radical addition with N-arylacrylamide to efficiently construct structurally diverse 3-substituted chroman-4-one derivatives.