Iodine-Catalyzed Annulation Reaction of Ortho -Formylarylketones with Indoles: A General Strategy for the Synthesis of Indolylbenzo[ b ]carbazoles.

The iodine-catalyzed cascade reaction of ortho -formylarylketones with indoles for the synthesis of indolylbenzo[ b ]carbazoles is reported. The reaction is initiated in the presence of iodine by two successive nucleophilic additions of indoles with an aldehyde group of ortho -formylarylketones, and the ketone does not undergo a nucleophilic addition and only involves in the Friedel-Crafts-type cyclization. A variety of substrates are tested, and the efficiency of this reaction is demonstrated with gram-scale reactions.