Brønsted‐Acid Mediated Synthesis of Symmetrical and Unsymmetrical Indolo[2,3‐a]carbazoles from Indoles and Α‐functionalized Ketones

Various symmetrical and unsymmetrical indolo[2,3-a]carbazoles were synthesized in a one- or two-step reaction using alpha-haloketones and indoles. The developed methodology demonstrated controllable chemoselectivity and gram-scale synthesis. Furthermore, this transformation was compatible with other alpha-functionalized ketones, such as alpha-hydroxy and alpha-acetyloxy ketones, allowing for the formation of their corresponding indolocarbazoles. Additionally, our photochemical research has revealed that all the indolo[2,3-a]carbazoles exhibited dual fluorescence, with the relative intensity varying depending on the solvent.