Enantioselective, Visible Light Mediated Aza Paternò–Büchi Reactions of Quinoxalinones

Abstract 3‐Substituted quinoxalin‐2(1 H )‐ones and various aryl‐substituted or tethered olefins underwent an enantioselective, inter‐ or intramolecular aza Paternò–Büchi 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.