Mechanistic Elucidation of the Arylation of Non-Spectator N-Heterocyclic Carbenes at Copper Using a Combined Experimental and Computational Approach

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• 作者：Thomas J. Williams ; Joshua T. W. Bray ; Benjamin R. M. Lake ; Charlotte E. Willans ; Nasir A. Rajabi ; Alireza Ariafard ; Chiara Manzini ; Fabio Bellina ; Adrian C. Whitwood ; Ian J. S. Fairlamb
• 刊名：Organometallics
• 出版年：2015
• 出版时间：July 27, 2015
• 年：2015
• 卷：34
• 期：14
• 页码：3497-3507
• 全文大小：673K
• ISSN：1520-6041

文摘

Cu^I(NHC)Br complexes (NHC = N-heterocyclic carbene) undergo a direct reaction with iodobenzene to give 2-arylated benzimidazolium products. The nature of the N-substituent on the NHC ligand influences the reactivity of the Cu^I(NHC)Br complex toward arylation. N-Benzyl or N-phenyl substituents facilitate arylation, whereas N-mesityl substituents hinder arylation. Density functional theory calculations show that an oxidative addition/reductive elimination pathway involving Cu^III species is energetically feasible. A less hindered Cu^I(NHC)Br complex with N-benzyl groups is susceptible to oxidation reactions to give 1,3-dibenzylbenzimidazolium cations containing a Cu^IBr anion (various polymorphs). The results described herein are of relevance to C鈥揌 functionalization of (benz)azoles.