Photoredox Catalysis in C-H Bond Functionalization

Photoredox catalysis offers a powerful approach to C-H bond functionalization by harnessing visible light to generate reactive open-shell intermediates under mild conditions. Central to this strategy is the use of hydrogen-atom transfer (HAT) to activate an array of Csp [[sup]]3[[/sup]] -H bonds, enabling their conversion into synthetically versatile radical species. This chapter explores a broad range of HAT mediators – including oxygen-, nitrogen-, halogen-, sulfur-, and carbon-centered radicals, as well as polyoxometalates such as decatungstate. The mechanistic basis of polarity-matched HAT is discussed alongside strategies for radical trapping, cross-coupling, and integration with dual catalytic cycles. Collectively, these methodologies define a versatile and modular framework for transforming simple C-H bonds into complex molecular architectures, establishing photoredox catalysis as a foundational tool in modern synthetic chemistry.