CH Halogenation via Directing Group Strategies With Earth‐Abundant Metals (Cu, Co, Ni, Fe): Scope, Mechanism, and Limitations

Halogenated hydrocarbons, encompassing aliphatic, alicyclic, aromatic, and heterocyclic frameworks, are indispensable structural motifs in pharmaceuticals, agrochemicals, advanced materials, and natural product synthesis. The direct functionalization of inert CH bonds through transition‐metal‐catalyzed halogenation has emerged as a powerful, step‐economical, and atom‐efficient strategy for the construction. In pursuit of sustainable catalysis, significant research efforts have recently focused on employing earth‐abundant, cost‐effective, and environmentally benign first‐row transition metals, notably copper, cobalt, nickel, and iron, as catalysts for these transformations. This review provides a systematic and comprehensive overview of recent advances in the halogenation of (hetero)aromatic and inert aliphatic CH bonds catalyzed by such economical metals. The content is organized according to the catalytic metal center, with each section discussing substrate scope, regioselectivity control, practical reaction conditions, and proposed mechanistic pathways. Key comparisons are drawn regarding the reactivity, selectivity, and functional group tolerance of different catalytic systems. Finally, the review outlines current methodological limitations and highlights promising future directions aimed at enhancing catalytic efficiency, broadening substrate generality, improving selectivity prediction, and developing truly sustainable and scalable halogenation protocols. The insights presented aim to guide the rational design of next‐generation CH functionalization methodologies.