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A Synergistic LUMO Lowering Strategy Using Lewis Acid Catalysis in Water to Enable Photoredox Catalytic, Functionalizing C-C Cross-Coupling of Styrenes

preprint
submitted on 25.04.2018 and posted on 26.04.2018 by Elisabeth Speckmeier, Patrick J. W. Fuchs, Kirsten Zeitler
Easy available alpha-carbonyl acetates serve as convenient alkyl radical source for an efficient, photocatalytic crosscoupling with a great variety of styrenes. Activation of electronically different alpha-acetylated acetophenone derivatives could be effected via LUMO lowering catalysis using a superior, synergistic combination of water and (water-compatible) Lewis acids. Deliberate application of fac-Ir(ppy)3 as photocatalyst to enforce an oxidative quenching cycle is crucial to the success of this (umpolung type) transformation. Mechanistic particulars of this dual catalytic coupling reaction have been studied in detail using both Stern-Volmer and cyclic voltammetry experiments. As demonstrated in more than 30 examples, our waterassisted
LA/photoredox catalytic activation strategy allows for excess-free, equimolar radical cross-coupling and subsequent formal Markovnikov hydroxylation to versatile 1,4-difunctionalized products in good to excellent yields.

Funding

DFG GRK1626

History

Email Address of Submitting Author

kzeitler@uni-leipzig.de

Institution

Universität Leipzig, Institut für Organische Chemie

Country

Germany

ORCID For Submitting Author

0000-0003-1549-5002

Declaration of Conflict of Interest

no conflict of interest

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