Photo- and Electrochemical Chlorination for (Hetero)Aryl C(sp2)─Cl Bond Formation.

Chlorinated (hetero)arenes are key structural motifs existed in various bioactive molecules, and serve as versatile building blocks in modern organic synthesis. Classical chlorination methods generally suffer from harsh reaction conditions, corrosive chlorinated reagents, and poor functional group tolerance. In recent years, photocatalysis and electrocatalysis have emerged as powerful and sustainable platforms for the sustainable synthesis of chlorinated (hetero)arenes under mild conditions, which significantly expand the diversity of chlorination reactions. This review summarizes the latest and representative advances in photo- and electrochemical chlorination of functionalized (hetero)arenes over the past decade, with particular emphasis on mechanistic understanding, catalyst and reagent design, and synthetic applications involving C(sp2)-H functionalization and ipso-chlorination of C(sp2)-X (X = C, N, S, and etc.) bonds. Elegant applications in late-stage functionalization of complex molecules and the upcycling of waste plastics are also highlighted in this review.