Direct synthesis of aryl-annulated [<i>c</i>]carbazoles by gold(<scp>i</scp>)-catalysed cascade reaction of azide-diynes and arenes

Abstract

The gold-catalysed annulation of conjugated alkynes bearing an azido group with arenes gave annulated [<i>c</i>]carbazoles. Using benzene, pyrrole, and indole derivatives as the nucleophiles, benzo[<i>c</i>]-, pyrrolo[2,3-<i>c</i>]-, and indolo[2,3-<i>c</i>]carbazoles were produced, respectively. The reaction proceeded through pyrrole and benzene ring construction accompanied by the formation of two carbon-carbon and one carbon-nitrogen bond and the cleavage of two aromatic C-H bonds. The mechanism of the reaction with pyrrole was investigated by density functional theory calculations. <i>N</i>,<i>N</i>'-dimethylated indolo[2,3-<i>c</i>]carbazole showed dual ultraviolet-visible-near-infrared and fluorescence spectral changes upon electrolysis.