Dual Copper/Photoredox Catalyzed C−H Functionalizations

The rapid development of photo-synergistic transition metal catalysis has emerged as a green paradigm to complement thermal transition metal catalytic strategies. The interplay between photoredox and transition metal catalytic cycles allows for precise control over reactivity and selectivity, facilitating the construction of complex molecules, with the formation of diverse C─C, C-heteroatom bonds. Among different transition metal catalysts, copper, abundant in the Earth's crust, is particularly notable for its unique electronic structure and light-absorbing properties. This has spurred considerable interest in utilizing Cu in combination with an appropriate photocatalyst to enable chemical transformations that are otherwise inaccessible or require harsh reaction conditions. Over the years, dual copper and photoredox catalysis has emerged as a powerful approach for C-H functionalizations, enabling the direct modification of inert C─H bonds under mild conditions. This synergistic strategy leverages copper catalysts to activate specific substrates or intermediates, while photoredox catalysts generate reactive radical species under visible-light-induced processes. This facilitates the introduction of diverse functional groups into C─H bonds without the need for pre-functionalized starting precursors, making it an attractive approach in organic synthesis. In this review, we aim to summarize dual Cu/photoredox-catalyzed C-H functionalizations, emphasizing detailed mechanistic insights from reported experimental and theoretical studies. The present and future potential of this exciting research field is highlighted as well.