Iron-catalyzed reductive cyclization of nitroarenes: Synthesis of aza-heterocycles and DFT calculations

Research into environmentally friendly strategies for hydrogen transfer reduction is increasing, along with the need for more elaborate heterocyclic platforms. Within this context, we develop a new approach for substituted dihydrobenzo[c]carbazoles and indoles. These compounds were synthesized through an iron-catalyzed hydrogen transfer reduction of nitroarenes, followed by intramolecular cyclization. This transformation involves using a Kn?lker-type catalyst, Cs2CO3as the base, and benzyl alcohol as the nonexpensive and low volatile hydrogen donor. We synthesize 30 examples of aza-heterocycles with moderate to excellent yields by applying this strategy. Additionally, DFT calculations demonstrated that the pathway reaction could follow an anionic mechanism.