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

Abstract Various symmetrical and unsymmetrical indolo[2,3‐a]carbazoles were synthesized in a one‐ or two‐step reaction using α‐haloketones and indoles. The developed methodology demonstrated controllable chemoselectivity and gram‐scale synthesis. Furthermore, this transformation was compatible with other α‐functionalized ketones, such as α‐hydroxy and α‐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.