Recent Advances in Palladium-Catalyzed Bridging C-H Activation by Using Alkenes, Alkynes or Diazo Compounds as Bridging Reagents

Transition-metal-catalyzed direct inert C-H bond functionalization has attracted much attention over the past decades. However, because of the high strain energy of the suspected palladacycle generated via C-H bond palladation, direct functionalization of a C-H bond less than a three-bond distance from a catalyst center is highly challenging. In this short review, we summarize the advances on palladium-catalyzed bridging C-H activation, in which an inert proximal C-H bond palladation is promoted by the elementary step of migratory insertion of an alkene, an alkyne or a metal carbene intermediate. 1 Introduction 2 Palladium-Catalyzed Alkene Bridging C-H Activation 2.1 Intramolecular Reactions 2.2 Intermolecular Reactions 3 Palladium-Catalyzed Alkyne Bridging C-H Activation 3.1 Intermolecular Reactions 3.2 Intramolecular Reactions 4 Palladium-Catalyzed Carbene Bridging C-H Activation 5 Conclusion and Outlook

Automated summary

This review summarizes the significance and methods of transition-metal-catalyzed bridging C-H activation in chemical synthesis, with a particular focus on the role of alkenes, alkynes, and metal carbenes as intermediates in the activation process.