ortho-C─H Alkylation of Aryl Chlorides by a Catellani Strategy

Herein we report a general and practical palladium/norbornene catalysis system that effectively promotes difunctionalization of less reactive aryl chlorides. The key to success lies in the use of a particular norbornene (NBE) derivative as a powerful mediator that synergistically cooperates with the palladium catalyst and an electron-rich phosphine ligand. A broad spectrum of electronically diverse aryl chlorides (57 examples) delivered the corresponding ortho-C─H alkylation/ipso-olefination products in moderate to good yields. Notably, this protocol features excellent functional-group tolerance, high concentration, scalability, and late-stage functionalization of complex aryl chlorides. Furthermore, by integrating this chemistry with its counterparts involving aryl iodides and bromides, an intriguing triple-Catellani reaction sequence was developed, rapidly increasing molecular complexity and diversity. Finally, DFT calculations were performed, revealing that noncovalent C─H⋯O interactions between the XPhos ligand and the NBE mediator promote the pivotal NBE insertion step.

Palladium/Norbornene Cooperative Catalysis

Palladium/norbornene cooperative catalysis has emerged as a distinct approach to construct polyfunctionalized arenes from readily available starting materials. This Review provides a comprehensive overview of this field, including the early stoichiometric investigations, catalytic reaction developments, as well as the applications in the syntheses of bioactive compounds and polymers. The section of catalytic reactions is divided into two parts according to the reaction initiation mode: Pd(0)-initiated reactions and Pd(II)-initiated reactions.

Intermolecular domino reaction of two aryl iodides involving two C-H functionalizations

A palladium-catalyzed intermolecular cross-coupling of two aryl iodides is reported, giving polycyclic ring systems with a high level of convergence and efficiency.