2-Alkynyl Indole-3-carbonitriles: Synthon for the Regioselective Synthesis of Functionalized 4-Aminocarbazoles

An operationally easy and atom-economical approach for the regioselective tandem synthesis of functionalized 4-aminocarbazoles from easily accessible 2-alkynyl indole-3-carbonitriles under mild reaction conditions has been developed. The developed chemistry involves aza-Henry and successive regioselective annulation to afford the functionalized carbazoles. Replacement of nitromethane with acetophenone led to the formation of the corresponding amino(phenyl)methanone-substituted carbazoles, further extending the diversity of the developed chemistry. The developed methodology accommodates wide functional group variation on the alkyne and is successfully applied for late-stage modification of bioactive molecules.