Benzylic C(sp3)–H Functionalization by Photo Redox Catalysis

Abstract Benzylic C–H bonds, due to their enhanced reactivity, offer a valuable platform for the selective functionalization in organic synthesis. Recent advancements in catalytic methods have enabled direct transformation of these sp3-hybridized sites under mild conditions. Transition-metal catalysis, photo redox strategies, and radical pathways have shown particular promise. These approaches allow for the construction of diverse C–C and C–X (X = N, O, Br, S) bonds. The presence of electron-withdrawing groups on the substrates significantly reduces the reaction efficiency, representing a limitation of these methodologies. The ability to functionalize benzylic positions through intermolecular and intramolecular methods expand the toolbox for late-stage modification of complex molecules. Such transformations are increasingly important in pharmaceutical and materials chemistry.