Metallaphotoredox catalysis for sp3 C–H functionalizations through single-electron transfer

Metallaphotoredox catalysis merging photocatalysis and transition metal catalysis is now the most efficient platform for sp3 C–H functionalizations due to its very efficient activation and transformation capability. In such a process, photocatalysis is usually in charge of C–H bond activation to generate an sp3-hybridized carbon-centred radical, whereas transition metal catalysis is in charge of the subsequent transformation of this radical. Here we review advances in sp3 C–H functionalizations under matallaphotoredox catalysis via photocatalytic single-electron transfer mechanisms as opposed to hydrogen atom transfer processes. The delineation of these advancements is initially organized according to distinct sp3 C–H bonds and subsequently categorized by various transition metal catalytic systems. We encompass a thorough exploration of diverse metallaphotoredox catalysis strategies, along with their synthetic applications and mechanisms. Similarities and differences between these strategies are described to inspire new reaction designs, thus promoting further development of this field. The merger of photocatalysis and transition metal catalysis has broadened the scope of chemical reactivity in organic synthesis. This Review provides an overview of the use of metallaphotoredox catalysis for sp3 C–H functionalizations that occur via single-electron, rather than hydrogen atom transfer.