<i>ortho</i> ‐C─H Alkylation of Aryl Chlorides by a Catellani Strategy
Jian‐Shu Wang, Zequan Liu, Guangyin Qian, Xiahe Chen, Liming Cao, Tenghui Yu, Jinxiang Ye, Yuanyuan Ma, Shuqing Chen, Zuo Yang, Hong‐Gang Cheng, Yun‐Fang Yang, Qianghui Zhou
Abstract
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.