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Abstract
Recently, there has been a resurgence of interest in the field of photocatalysis within the synthetic community. This is in part due to the development of visible light-mediated photoredox catalysis. This mild synthetic approach has allowed access to numerous novel bond-forming transformations. The most commonly employed photocatalysts to date are ruthenium and iridium-based complexes, two of the rarest metals on earth. A goal within our group has been to develop complementary photocatalysts that are based on earth-abundant metals. Namely, we have been able to exploit chromium(III) complexes as efficient photooxidants under visible light irradiation. Chapter 2 of this document will discuss our findings on the discovery of a highly reactive second-generation chromium photocatalyst that displays increased absorbance in the visible light region compared to the first-generation catalyst. Further, we have shown the utility of this photocatalyst through application in a dearomative (3 + 2) cycloaddition reaction between indoles and vinyldiazo species to synthesize densely substituted indoline substrates. In another study discussed in Chapter 3, the functional group tolerance of this dearomative cycloaddition was expounded upon. Specifically, we were able to employ valuable tryptamine and tryptophan derivatives in this cycloaddition with vinyldiazo species to access similar indoline substrates with amine functionality. This was accomplished by utilizing a highly efficient Ru(II) photocatalyst. Finally, Chapter 4 will discuss preliminary work on a (3 + 3) cycloaddition between aminocyclopropanes and vinyldiazo species to generated functionalized aminocyclohexenes. This transformation was achieved via a visible light-mediated, photoredox-catalyzed oxidation to generate a highly reactive distonic radical cation intermediate. This dissertation will outline and described in detail these three separate studies in radical cation cycloadditions.