Azo Coupling of Indoles Revisited: Synthesis of Biindolyl Photoswitches via the Azo-Coupling/C–H Functionalization Domino Approach

When azo coupling of aryldiazonium salts with indoles was carried out in aprotic nonpolar solvent on air, a pseudo-three-component reaction has been discovered. Azo coupling is followed by a nucleophilic addition of a second indole unit to the indolium intermediate; aromatization and oxidation are achieved under air. © 2023 American Chemical Society.