Iridium Catalyzed Intramolecular Cyclization of Allyl Alcohol-Indole Hybrids: Rapid Access to Photoluminescent 5H-Benzo[b]carbazoles

Herein, we report an intramolecular cyclization of secondary allylic alcohol-tethered indoles using iridium catalysis in the presence of diphenyl phosphate. This first-of-its-kind allylic substitution-aromatization cascade efficiently delivers 6-ethyl-5H-benzo[b]carbazoles in excellent yields (up to 96%) under mild conditions. The scope was extended to a naphthalen-1-ylmethanol containing 1H-benzo[f]indole derivative. In addition to a few key synthetic transformations, the photoluminescence properties of the benzo[b]carbazole derivatives have also been thoroughly explored.