Organic Chemistry, Short Talk
OC-014

Electron Donor-Acceptor Complex-Catalyzed Aromatic Nitration: Unveiling the Role of Polymeric Donors

A. J. Fernandes1, H. Lecomte1*, M. G. Metzger1*, Q. E. Ordan1*, K. N. Houk2*, D. Katayev1*
1Departement für Chemie, Biochemie und Pharmazie, Universität Bern, Freiestrasse 3, 3012 Bern, Switzerland, 2Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States

Nitroaromatic compounds are indispensable building blocks in the synthesis of pharmaceuticals, agrochemicals, and functional materials, playing a central role in both academic research and large-scale industrial production.1,2 Despite their significance, the development of nitration strategies that are sustainable, highly chemo- and regioselective, and compatible with bench-stable, non-acidic reagents under catalytic and environmentally responsible conditions remains a pressing and unresolved challenge. Recently, light-mediated processes have attracted considerable attention due to their enhanced sustainability, milder conditions, and their ability to take molecules in their excited-states and unlock novel reactivity.

Herein, we report, the first example of an aromatic nitration reaction photocatalyzed by an Electron Donor–Acceptor (EDA) complex. This transformation proceeds under mild, light-mediated conditions and is enabled by a unique combination of two key components: the potent electron acceptor N,6-dinitrosaccharin3 and a carbazole-based polymeric donor, which synergistically generate nitryl radicals (•NO2) through EDA complex4,5 activation. The resulting •NO2 radicals efficiently functionalize a broad range of aromatic substrates, displaying excellent chemoselectivity and tolerance to diverse functional groups. Detailed mechanistic studies combining both experimental and computational evidence support a catalytic cycle initiated by photoinduced EDA complex activation and subsequent •NO2 radical generation. DFT studies elucidate the intricacies of the nitryl radical addition and radical-pair collapse pathways that govern the reaction mechanism, while offering key insights into the superior reactivity enabled by the polymeric donor.

 
 

 

 

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[2] K. Nepali, H.-Y. Lee, J.-P. Liou, J. Med. Chem. 2019, 62, 2851–2893.
[3] A. J. Fernandes, V. Valsamidou, D. Katayev, Angew. Chem. Int. Ed. 2024, 63, e202411073.
[4] A. K. Wortman, C. R. J. Stephenson, Chem 2023, 9, 2390–2415.
[5] T. M. Bockman, J. K. Kochi, J. Phys. Org. Chem. 1994, 7, 325–351.