Iron-catalyzed one-pot synthesis of quinoxalines: transfer hydrogenative condensation of 2-nitroanilines with vicinal diols?

RSC Advances Pub Date: 2021-05-20 DOI: 10.1039/D1RA02532E

Abstract

Here, we report iron-catalyzed one-pot synthesis of quinoxalines via transfer hydrogenative condensation of 2-nitroanilines with vicinal diols. The tricarbonyl (η4-cyclopentadienone) iron complex, which is well known as the Kn?lker complex, catalyzed the oxidation of alcohols and the reduction of nitroarenes, and the corresponding carbonyl and 1,2-diaminobenzene intermediates were generated in situ. Trimethylamine N-oxide was used to activate the iron complex. Various unsymmetrical and symmetrical vicinal diols were applied for transfer hydrogenation, resulting in quinoxaline derivatives in 49–98% yields. A plausible mechanism was proposed based on a series of control experiments. The major advantages of this protocol are that no external redox reagents or additional base is needed and that water is liberated as the sole byproduct.

Graphical abstract: Iron-catalyzed one-pot synthesis of quinoxalines: transfer hydrogenative condensation of 2-nitroanilines with vicinal diols
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