title: A concept of supported amino acid ionic liquids and their application in metal scavenging and heterogeneous catalysis.
abstract: 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 have shown an efficient metal scavenging ability (e.g., CuI, Pd(OAc)2, Pd0, and IrCl3) without the aid of a nonimmobilized ionic liquid, which relies on the highly synergistic effect of the coordination with the nitrogen atom and the COO- group of the L-proline moiety, electrostatic forces, and steric protection. The resulting metal-soaked supported ionic liquids can be used as efficient heterogeneous catalysts. These materials have been investigated in the CuI-catalyzed N-arylation of nitrogen-containing heterocycles and exhibit much higher catalytic activity and a more extensive structural range of aryl and heteroaryl halides than those exhibited by free L-proline in combination with CuI both in the ionic liquid ([BMIM][BF4]) and in the corresponding homogeneous reaction conditions. The CuI-soaked catalyst 4a-2 can be recycled for nine runs at least without any considerable loss of activity. To the best of our knowledge, our catalytic process is 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-free hydrogenation of styrene to ethylbenzene. This new concept is generally applicable and may easily be extended to other supported task-specific ionic liquids.
authors.affiliation: Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, West China Hospital, West China Medical School, Sichuan University, Chengdu 610064, PR China.
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Liangbo
authors.initials: L
authors.lastname: Zhu
authors.forename: Jingbo
authors.initials: J
authors.lastname: Lan
authors.forename: Rugang
authors.initials: R
authors.lastname: Xie
authors.forename: Jingsong
authors.initials: J
authors.lastname: You
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D016166:Free Radical Scavengers / Q000138:chemical synthesis / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000596:Amino Acids; D016166:Free Radical Scavengers; D006571:Heterocyclic Compounds; D052578:Ionic Liquids; D019216:Metals, Heavy; D009942:Organometallic Compounds; D011137:Polystyrenes