Visible-Light-Induced Decarboxylative Cross-Coupling Reactions: Transition-Metal and Metal-Free Approaches.

Photocatalysis has emerged as a powerful and sustainable platform for modern organic synthesis, enabling efficient bond-forming reactions under mild visible-light irradiation. Transition-metal complexes play a crucial role in these systems by facilitating electron-transfer and energy-transfer (EnT) processes, thereby enhancing reaction efficiency and selectivity. Among the numerous transformations accessible through photocatalysis, decarboxylative cross-coupling reactions have emerged as a versatile and efficient tool for the construction of carbon-carbon and carbon-heteroatom bonds, utilizing abundant and stable carboxylic acids as readily available coupling partners. In this review, we critically examined recent advances in visible-light-induced decarboxylative cross-coupling reactions from a coordination-chemistry perspective. Key classes of photocatalysts, including ruthenium-, iridium-, copper-, and nickel-based complexes, are discussed alongside cooperative dual-catalytic systems, metallaphotoredox strategies, and metal-free approaches. Emphasis is placed on the mechanistic pathways governing these transformations, including single-electron transfer, ligand-to-metal charge transfer, and EnT processes. Furthermore, current challenges and emerging opportunities in catalyst design, sustainability, efficiency, and reaction scalability are highlighted, underscoring the central role of coordination chemistry in advancing environmentally benign, energy-efficient catalytic methodologies.