Catalytic Functionalization of Unactivated π-Bonds Enabled by Bidentate Directing Auxiliaries.

Catalytic functionalization of unactivated π-bonds is a cornerstone of modern organic synthesis, offering efficient pathways to complex molecules. The emergence of the bidentate directing auxiliary strategy has fundamentally reshaped and significantly broadened the scope of transition-metal-catalyzed π-bond functionalization. A key feature of this strategy is the formation of chelated intermediates where the bidentate directing auxiliary, tethered to the alkene or alkyne substrate, coordinates strongly to the transition metal catalyst. This chelation provides numerous advantages, including enhanced reaction kinetics, superior chemoselectivity, and improved catalyst efficiency, thereby enabling previously challenging reaction types on unactivated π-bonds. This review highlights the recent significant progress in π-bond functionalization enabled by bidentate directing auxiliaries, focusing on transformations catalyzed by palladium, nickel, copper, and other transition metals. We systematically discuss major reaction types, including hydrofunctionalization, difunctionalization, and C-H activation across various substrates, while emphasizing the underlying design principles that govern reactivity and selectivity in these systems.