Isoquinoline formation by a novel photochemical intermolecular cycloaddition of 1,1-diphenylethene derivatives to 1,4-dicyanobenzene

Phenanthrene-sensitized photoreaction of 1,1-diphenylethene (DPE) derivatives and 1,4-dicyanobenzene (DCNB) in benzene leads to a novel intermolecular cycloaddition to give isoquinoline derivatives as a novel synthetic method. The feasibility of this reaction was dependent upon the side chain structure of DPE derivatives, which would regulate the stability of radical cation DPE+· in a highly polar exciplex, and/or a contact radical ion pair, by hyperconjugation or neighboring group participation.