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Magnetically Separable Proline Ligand
G. Chouhan, D. Wang, H. Alper*
University of Ottawa, Canada
23 January 2008 (online)
Magnetic nanoparticle-supported proline ligand MNP-2 was prepared from azide-functionalized magnetite MNP-1 with tert-butyl-N-Boc-4-propargyloxyprolinate through the alkyne-azide [2+3]-cycloaddition reaction (eq. 1). The CuI-catalyzed Ullmann-type coupling reactions of aryl/heteroaryl bromides with various N-heterocycles such as imidazole, pyrazole, indole, and benzimidazole were carried out in the presence of proline-loaded magnetic nanoparticle MNP-2 as a ligand and Cs2CO3 as a base to form the corresponding N-aryl products in 30-98% yield.