Efficient Synthesis of Indolyl Benzo[b]carbazoles via Surfactant-Type Brønsted Acid-Catalyzed Three-Component Cyclization of Ortho-Formylarylketones with Indoles

Abstract

The surfactant-type Brønsted acid-catalyzed multi-component cascade reaction of ortho-formylarylketones with indoles was investigated in an aqueous medium for the synthesis of indolyl benzo[b]carbazoles. The reaction was carried out in the presence of dodecylbenzenesulfonic acid, which was initiated by two consecutive nucleophilic additions of indoles to the aldehyde group of ortho-formylarylketones, followed by a Friedel−Crafts-type cyclization and dehydrative aromatization. This protocol afforded the desired products in good yields under mild conditions and demonstrated a broad substrate scope.