蟺鈥撓€ Interaction Assisted Hydrodefluorination of Perfluoroarenes by Gold Hydride: A Case of Synergistic Effect on C鈥揊 Bond Activation

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• 作者：Hongbin Lv ; Jin-Hui Zhan ; Yuan-Bo Cai ; Yi Yu ; Bingwu Wang ; Jun-Long Zhang
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：October 3, 2012
• 年：2012
• 卷：134
• 期：39
• 页码：16216-16227
• 全文大小：654K
• 年卷期：v.134,no.39(October 3, 2012)
• ISSN：1520-5126

文摘

鈥淪ynergistic effect鈥?is prevalent in natural metalloenzymes in activating small molecules, and the success has inspired the development of artificial catalysts capable of unprecedented organic transformations. In this work, we found that the attractive 蟺鈥撓€ interaction between organic additives (as electron-donors) and the perfluorinated arenes (as electron acceptors) is effective in gold hydride catalyzed activation of C鈥揊 bonds, specifically hydrodefluorination (HDF) of perfluoroarenes catalyzed by the Sadighi鈥檚 gold hydrides [(NHC)AuH] (NHC = N-heterocyclic carbene). Although a weak interaction between [(NHC)AuH] and perfluoroarenes was observed from ¹H NMR and UV鈥搗is spectroscopies, low reactivity of [(NHC)AuH] toward HDF was found. In contrast, in the presence of p-N,N-dimethylaminopyridine (DMAP), the HDF of perfluoroarenes with silanes can be efficiently catalyzed by [(NHC)AuH], resulting in mainly the para-hydrodefluorinated products with up to 90% yield and 9 turnovers. The yield of the reaction increases with the more electron-withdrawing groups and degree of fluorination on the arenes, and the HDF reaction also tolerates different function groups (such as formyl, alkynyl, ketone, ester, and carboxylate groups), without reduction or hydrogenation of these function groups. To reveal the role of DMAP in the reactions, the possible 蟺鈥撓€ interaction between DMAP and perfluoroarenes was suggested by UV鈥搗is spectral titrations, ¹H NMR spectroscopic studies, and DFT calculations. Moreover, ¹H and ¹⁹F-NMR studies show that this 蟺鈥撓€ interaction promotes hydrogen transfer from [(NHC)AuH] to pyridyl N atom, resulting in C鈥揊 bond cleavage. The interpretation of 蟺鈥撓€ interaction assisted C鈥揊 activation is supported by the reduced activation barriers in the presence of DMAP (31.6 kcal/mol) than that in the absence of DMAP (40.8 kcal/mol) for this reaction. An analysis of the charge distribution and transition state geometries indicate that this HDF process is controlled by the 蟺鈥撓€ interaction between DMAP and perfluoroarenes, accompanied with the changes of partial atomic charges.