Development of N-Heterocyclic Carbene鈥揅opper Complexes for 1,3-Halogen Migration

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• 作者：Steven C. Schmid ; Ryan Van Hoveln ; Jared W. Rigoli ; Jennifer M. Schomaker
• 刊名：Organometallics
• 出版年：2015
• 出版时间：August 24, 2015
• 年：2015
• 卷：34
• 期：16
• 页码：4164-4173
• 全文大小：657K
• ISSN：1520-6041

文摘

A series of NHC鈥揷opper complexes was synthesized and their potential to catalyze 1,3-halogen migration explored. Increasing the steric bulk around the metal drastically improves the lifetime of NHC鈥揅uH species and promotes 1,3-halogen migration of both 2-bromo- and 2-chlorostyrenes through transfer of an aryl halogen to a benzylic carbon with concomitant arene borylation. The NHC-based system displays a broad substrate scope with notable advantages over previously reported phosphine-based catalysts, including complete selectivity for migration versus competing benzylic borylation, increased steric tolerance, efficient aryl chloride migration, and facile formation and characterization of organocopper catalytic intermediates. Experimental evidence and DFT calculations support a mechanism proceeding through dearomatization of a benzyl copper species, followed by a 1,4-halogen shift and borylation of the resulting ArCu(I) intermediate.