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 Knolker-type catalyst, Cs2CO3 as the base, and benzyl alcohol as the non-expensive 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. (c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

We developed a new approach for synthesizing substituted dihydrobenzo[c]carbazoles and indoles through iron-catalyzed hydrogen transfer reduction of nitroarenes followed by intramolecular cyclization. This strategy involves the use of a Knolker-type catalyst, Cs2CO3 as the base, and benzyl alcohol as the hydrogen donor. We synthesized 30 examples of aza-heterocycles with moderate to excellent yields using this approach. DFT calculations suggest an anionic mechanism for the reaction pathway.