Facile Synthesis of Azahelicenes and Diaza[8]circulenes through the Intramolecular Scholl Reaction

Carbazole-based aza7]helicenes and hetero9]helicenes were successfully obtained via the intramolecular Scholl reaction of 3,6-bis(biphenyl-2-yl)carbazole congeners, while the reaction of 3,6-bis(naphthylphenyl)-appended carbazole gave a triple helicene via an unexpected simultaneous double aryl rearrangement. DFT calculations suggested that the rearrangement proceeded via an arenium cation intermediate. In addition, the reaction of methoxy-appended substrate gave an azahepta8]circulene via the concurrent C?C bond formation. These helical dyes showed circularly polarized luminescence. The azahepta8]circulene was further transformed into deeply saddle-distorted dibenzodiaza8]circulenes as the first example of its solution-based synthesis and unambiguous structural determination.