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.

Relatively mild and highly efficient CuI-catalyzed N-arylation procedures for nitrogen-containing heterocycles (e.g., imidazoles, benzimidazoles, pyrroles, pyrazoles, indoles, triazoles, etc.) with aryl and heteroaryl halides have been developed. The protocols can be performed easily and tolerate a number of functional groups, such as ester, nitrile, nitro, ketone, free hydroxyl, and free primary amine on the aryl halide.

New (S)-pyrrolidinylmethylimidazole ligands (4a-c) have been readily synthesized in a straightforward fashion from least expensive starting materials in short steps in high yields. Relatively mild and highly efficient CuI-catalyzed N-arylation procedures for imidazoles with aryl and heteroaryl bromides or chlorides have been developed in the presence of 4a and Cs2CO3. It is important to note that the protocol could tolerate functional groups such as ester, nitrile, nitro, ketone, free hydroxyl, and free primary amine on the aryl halide. The protocol could also be applicable to other pi-electron-rich nitrogen heterocycles (pyrrole, pyrazole, indole, benzimidazole, and triazole), affording the N-arylazoles in good to excellent yields.

A copper-catalyzed process has been developed for the N-arylation reaction under very mild conditions in the absence of additional ligand. This protocol could not only tolerate an array of thermally sensitive functional groups, but also achieve high chemoselectivity.

Heteroaryl Halides. -The pyrrolidine shown in the scheme is a highly efficient ligand which allows the formation of a wide range of N-arylated compounds in good to high yields. -(ZHU, L.; CHENG, L.; ZHANG, Y.; XIE, R.; YOU*, J.; J.