An Efficient, Solvent‐Free and Green One‐Pot Protocol for the Rapid Access to Polyfunctionalized Carbazoles

The solvent‐free one‐pot π‐extension reaction of indole to carbazole has been carried out very efficiently on the surface of a basic alumina as an inexpensive reusable solid support by involving several 2‐(3‐formyl‐1 H ‐indol‐2‐yl)acetophenones/acetates and a wide range of 2‐aryl/hetero‐aryl/alkyl‐substituted nitroolefins (or in situ generated nitroolefins from aldehydes and nitromethane)/nitrodienes/chalcones/cinnamyl esters as acceptors under aerobic conditions. This oxidant‐free one‐shot protocol delivers high to excellent yields (76‐92 %) of a novel series of 3‐nitro/benzoyl/carboxylate carbazole derivatives in eco‐friendly and economical manners and allows a variety of sensitive functional groups on aromatic rings. Moreover, the synthesized 3‐nitrocarbazoles are valuable synthons for the easy access to tetra cyclic pyrido[3,2‐ c ]carbazoles, 3‐iodo/arylacetylenyl‐substituted carbazoles and ( Z )‐N‐carbazole‐substituted nitroenamine ( Z/E= 99:1).