Visible‐Light‐Promoted Cascade Radical Cyclization for Difluorochroman‐4‐Ones Via Electron Donor‐Acceptor Complexes

Abstract The research of electron donor‐acceptor complex has developed fast in the field of photochemistry. Herein, the green and efficient metal‐free visible‐light‐promoted synthesis of difluorochroman‐4‐ones has been achieved with 2‐(allyloxy)arylaldehyde and bromodifluoroacetamide, which is driven by noncovalent interactions between 2‐(allyloxy)arylaldehyde/ N , N , N′ , N′ ‐tetramethylethylene diamine (TMEDA) and bromodifluoroacetamide/TMEDA. By precisely optimizing the electron donor and reaction solvent, a wide range of structurally diverse difluorochroman‐4‐ones, including aryl amide, aliphatic amide and ester groups, were obtained in up to 76 % yields. This strategy offers the benefits of simple operation, good yields, high atomic economy and broad applicability, providing an essential complement to traditional approaches for the preparation of chroman‐4‐one skeletons without any transition metals, photocatalysts or oxidants.