Influence of a Very Bulky N-Heterocyclic Carbene in Gold-Mediated Catalysis

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• 作者：Adri谩n G贸mez-Su谩rez ; Rub茅n S. Ram贸n ; Olivier Songis ; Alexandra M. Z. Slawin ; Catherine S. J. Cazin ; Steven P. Nolan
• 刊名：Organometallics
• 出版年：2011
• 出版时间：October 24, 2011
• 年：2011
• 卷：30
• 期：20
• 页码：5463-5470
• 全文大小：941K
• 年卷期：v.30,no.20(October 24, 2011)
• ISSN：1520-6041

文摘

The syntheses of the free carbene IPr* (IPr* = 1,3-bis(2,6-bis(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene) and related gold complexes [Au(IPr*)Cl] (C1) and [Au(IPr*)(NTf₂)] (C2) were achieved in high yields. The % V_Bur of IPr* for both gold complexes was measured, revealing IPr* as one of the bulkiest NHCs on gold complexes reported to date. In addition, the catalytic activity of C1 and C2 in several reactions, typically catalyzed by Aup>Ip> complexes, was investigated. Examples include the tandem alkoxylation/lactonization of 纬-hydroxy-伪,尾-acetylenic esters, the [3,3]-rearrangement of propargylic acetates leading to the formation of conjugated enones and substituted indenes, and the rearrangement of allylic acetates. These studies revealed a strong solvent effect on the catalytic activity with 1,2-dichloroethane as the solvent of choice. The screening of C1 and C2 demonstrated only slightly diminished activities in comparison to [Au(NHC)(L)] complexes bearing bulky ligands such as IPr and SIPr.