Earth-Abundant Transition Metals Catalyzed Alkylation, Alkenylation, and Alkynylation of Arenes via Cross Dehydrogenative Coupling (CDC): Synthetic Strategies and Mechanistic Pathways.

Cross dehydrogenative coupling (CDC) via C-H bond activation enables direct and sustainable synthesis of carbon-carbon and carbon-heteroatom bonds, bypassing the requirement of prefunctionalization steps. Utilizing earth-abundant metals such as iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu), CDC offers cost-effective, environmentally friendly alternatives to precious metal catalysts (Ru, Rh, Pd, Ir). These metals facilitate mild and efficient C-H activation, expanding substrate scope and improving selectivity. Among different methods, transition metal-catalyzed C-H activation via CDC has emerged as an effective tool for direct functionalization, offering efficiency, sustainability, and regioselectivity. Recent advancements address challenges such as catalyst deactivation and functional group compatibility. This article highlights recent developments of various synthetic alkylation, alkenylation, and alkynylation strategies of arenes and their mechanistic pathways catalyzed by earth-abundant metals (Fe, Co, Ni, and Cu) through cross dehydrogenative coupling via C-H bond activation.