Enantioselective, Visible Light-mediated Aza Paternò-Büchi Reactions of Quinoxalinones.

3-Substituted quinoxalin-2(1 H )-ones and various aryl-substituted or tethered olefins underwent an enantioselective, inter- or intramolecular aza Paterno-Buchi reaction upon irradiation at λ = 420 nm in the presence of a chiral sensitizer (10 mol%). For the intermolecular reaction with 1-arylethenes as olefin components, the scope of the reaction was studied (14 examples, 50-99% yield, 86-98% ee ). The absolute and relative configuration of the products were elucidated by single crystal X-ray crystallography. The reaction is suggested to occur by triplet energy transfer in a hydrogen-bonded 1:1 complex between the imine substrate and the catalyst. The intramolecular cycloaddition, consecutive reactions of the product azetidines, and an alternative reaction mode of quinoxalinones were investigated in preliminary experiments.