Advances in Chromium(III) Photocatalysis: Catalyst Design and Reaction Development

Over the past few decades, photoredox catalysis has emerged as a powerful tool for new bond formation. Acting as an oxidant or a reductant, an excited-state metal complex can generate reactive radical intermediates via a single-electron transfer process. The most commonly used transition-metal photocatalysts are ruthenium or iridium complexes. Our group has utilized chromium(III) complexes in a variety of different photoredox transformations. Notably, we have been able to accomplish (4+2) cycloaddition reactions using electron-rich or electron-deficient dienophiles, a (2+1) cycloaddition with diazoacetates, and a (3+2) cycloaddition with vinyl diazoacetates while employing [Cr(Ph2phen)3](BF4)3 and visible light as the photocatalytic system. While working with collaborators in an attempt to expand the scope of chromium(III) photocatalysis, the development of novel chromium(III) photocatalysts for reaction discovery will be discussed. Efforts to utilize chromium(III) photocatalysis, along with the design of an intramolecular Baeyer-Villiger reaction, toward the synthesis of the Cripowellin alkaloids will also be mentioned. Lastly, in working with collaborators at UGA, the scalable synthesis of a unique ketohydroperoxide intermediate along the hydrocarbon oxidation mechanism will be highlighted.

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