A Concept of Supported Amino Acid Ionic Liquids and Their Application in Metal Scavenging and Heterogeneous Catalysis

详细信息    查看全文

• 作者：Wen Chen ; Yuanyuan Zhang ; Liangbo Zhu ; Jingbo Lan ; Rugang Xie ; Jingsong You
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：November 14, 2007
• 年：2007
• 卷：129
• 期：45
• 页码：13879 - 13886
• 全文大小：254K
• 年卷期：v.129,no.45(November 14, 2007)
• ISSN：1520-5126

文摘

Novel supported task-specific ionic liquids have been developed for the first time via the ionic-pair coupling of imidazolium cation of the modified polystyrene support with L-proline. The materials haveshown an efficient metal scavenging ability (e.g., CuI, Pd(OAc)₂, Pd⁰, and IrCl₃) without the aid of anonimmobilized ionic liquid, which relies on the highly synergistic effect of the coordination with the nitrogenatom and the COO^- group of the L-proline moiety, electrostatic forces, and steric protection. The resultingmetal-soaked supported ionic liquids can be used as efficient heterogeneous catalysts. These materialshave been investigated in the CuI-catalyzed N-arylation of nitrogen-containing heterocycles and exhibitmuch higher catalytic activity and a more extensive structural range of aryl and heteroaryl halides thanthose exhibited by free L-proline in combination with CuI both in the ionic liquid ([BMIM][BF₄]) and in thecorresponding homogeneous reaction conditions. The CuI-soaked catalyst 4a-2 can be recycled for nineruns at least without any considerable loss of activity. To the best of our knowledge, our catalytic processis among the most efficient approaches to the N-arylation of imidazoles with aryl halides so far reported.Furthermore, the Pd-soaked material 4a-2 also shows higher catalytic activity in the solvent-freehydrogenation of styrene to ethylbenzene. This new concept is generally applicable and may easily beextended to other supported task-specific ionic liquids.