Recent Advances in Pd-Catalyzed Directed meta-C-H Olefination: Strategies and Outlook

Vinyl arenes are widely found in natural products, pharmaceuticals, and functional materials, and serve as important intermediates for the construction of complex molecular architectures. Among the various synthetic strategies available, transition-metal-catalyzed direct C-H olefination has emerged as a particularly concise and efficient alternative approach. Through the use of directing strategies and ligand modulation, both the regioselectivity and stereoselectivity of C-H bond cleavage can be precisely controlled. Among the available catalytic systems, palladium catalysts occupy a central position owing to their outstanding reactivity and broad applicability. In comparison, ortho-C-H functionalization has become relatively well established, whereas remote C-H functionalization remains underdeveloped due to the high-energy macrocyclic metallacyclic transition states involved, as well as factors such as conformational strain and steric hindrance. Current studies have primarily focused on directing-group design and substrate scope expansion, while other key issues have received comparatively limited attention. Building upon our group's research efforts in this area, this review systematically summarizes the recent advances, mechanistic insights, and applications of palladium-catalyzed directing-group-assisted meta-C-H olefination, with the aim of providing a useful reference for future developments in this field.