The Decatungstate Anion in Metallaphotoredox Catalysis

Abstract

Methods for the functionalization of C–H bonds have the potential to revolutionize organic synthesis by facilitating reactivity at ubiquitous but otherwise inert positions. This can enable both efficient upgrading of abundant feedstocks and late-stage diversification of complex structures, dramatically expanding readily accessible chemical space. Among established C–H functionalization strategies, hydrogen atom transfer (HAT) provides a particularly modular approach, separating the challenging C–H activation step from the well-established functionalization of the resultant radical. In recent years, advances in photoredox catalysis have dramatically expanded the range of HAT-mediated transformations, enabling the generation of open-shell species capable of hydrogen atom abstraction under mild conditions. Combining this convenient generation of alkyl radicals with the remarkable single-electron chemistry of first-row transition metals has facilitated the direct use of C–H bonds in valuable cross-coupling reactions. Described herein are several novel HAT-mediated functionalizations of strong C(sp3)–H bonds, employing the decatungstate anion to facilitate photocatalytic C–H bond cleavage at unactivated sites. In Chapter 2, the merger of decatungstate photocatalysis with copper catalysis affords a general method for C(sp3)–H trifluoromethylation, incorporating the pharmaceutically relevant CF3 group at traditionally unreactive positions. In Chapter 3, decatungstate/nickel dual catalysis enables the direct use of strong, aliphatic C–H bonds as cross-coupling partners, providing a valuable method for C(sp3)–H arylation. In Chapter 4, combining decatungstate photocatalysis with the open-shell chemistry of sulfur dioxide enables an efficient synthesis of alkyl sulfinates, demonstrating a powerful strategy to convert C–H bonds into diverse sulfur-containing products.