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Visible-Light-Promoted Metal-Free Ammoxidation of C(sp3)-H bonds

preprint
submitted on 24.08.2020 and posted on 24.08.2020 by Kathiravan Murugesan, Karsten Donabauer, Burkhard Koenig
The metal-free activation of C(sp3)-H bonds to value-added products is of paramount importance in organic synthesis. Herein, we report the use of the commercially available organic dye 2,4,6-triphenylpyrylium tetrafluoroborate (TPP) for the conversion of methylarenes to the corresponding aryl nitriles via a photo process. Applying this methodology, a variety of cyanobenzenes have been synthesized in good to excellent yield under metal- and cyanide-free conditions. We demonstrate the scope of the method with over 50 examples including late-stage functionalization of drug molecules (celecoxib) and complex structures such as L-menthol, amino acids and cholesterol derivatives. Further, the presented synthetic protocol is applicable for gram-scale reactions. In addition to methylarenes, selected examples for the cyanation of aldehydes, alcohols and oximes are demonstrated as well. Detailed mechanistic investigations have been carried out using time-resolved luminescence quenching studies, control experiments and NMR‑ spectroscopic as well as kinetic studies, all supporting the proposed catalytic cycle.

Funding

German Science Foundation (DFG, KO 1537/18-1)

This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement No. 741623).

History

Email Address of Submitting Author

burkhard.koenig@chemie.uni-regensburg.de

Institution

University of Regensburg

Country

Germany

ORCID For Submitting Author

0000-0002-6131-4850

Declaration of Conflict of Interest

There are no conflicts of interest to declare.

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