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Overcoming Back Electron Transfer Facilitates the Implementation of Electron Donor-Acceptor Complexes in Catalysis

preprint
revised on 17.04.2020 and posted on 20.04.2020 by Edward McClain, Timothy Monos, Mayuko Mori, Joel Beatty, Corey Stephenson
Electron donor-acceptor (EDA) complexes can controllably generate radicals under mild conditions through selective photoexcitation events. However, unproductive reactivity from fast deactivation of the photoexcited complexes through back electron transfer has slowed the development of EDA complexes in synthetic methodology. Here, we disclose the study of EDA complexes derived from 2-methoxynaphthalene donor and acylated ethyl isonicotinate N-oxide acceptor that undergo a fast N–O bond fragmentation event upon photoexcitation. This reaction design not only overcomes the limitations of back electron transfer but also enables the regeneration of the donor species, representing a rare example EDA photochemistry in a catalytic regime. The synthetic utility is demonstrated through visible light-driven radical trifluoromethylation and Minisci alkylation reactions. The scalability of the EDA complex promoted reaction evidenced by the successful multigram-scale trifluoromethylation of methyl N-Boc pyrrole-2-carboxylate in a continuous flow manifold.

Funding

Redox catalysis strategies for synthesis

Directorate for Mathematical & Physical Sciences

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History

Email Address of Submitting Author

crjsteph@umich.edu

Institution

University of Michigan

Country

USA

ORCID For Submitting Author

0000-0002-2443-5514

Declaration of Conflict of Interest

none

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