C-N, C-O Cross-coupling Reactions Catalyzed By Nano-copper

C(aryl)-N, C(aryl)-O bonds are prevalent in numerous pharmaceuticals and natural compounds. Ullmann-type coupling reaction is one of the most important methods to construct C(aryl)-N, C(aryl)-O bonds in organic synthesis. However, the classic Ullmann reactions are generally conducted under harsh reaction conditions such as elevated temperatures as high as 200°C, use of ligands, and moderate yields. In the past few decades, more and more attentions have been paid to the improvement of the classical Ullmann reaction, such as the use of cheaper catalysts, environmentally solvent, ligand-free condition for this kind of reaction. The C-N cross-coupling reactions based on copper catalyst under ligand-free conditions were studied in this paper. The main contents are summarized as follows:1. Cu and Ni nanoparticles were prepared through reduction of Cu(NO3)2 and NiCl2 with NaBH4 in aqueous medium under sonication, which were used to catalyze the C-N cross-coupling reaction. The result showed that they exhibit high catalytic activity in the reaction of aryl iodides with electron-deficient amines using mixed catalyst system Cu : Ni=2 : 1 (5 mol% Cu) under reflux at 110°C.2. CuI nanoparticles were prepared by a simple hydrothermal method in teflon-lined autoclave. The obtained CuI products were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM) analysis. The C-N cross-coupling reaction were catalyzed using CuI nanoparticles under hydrothermal and ligand free conditions. The effects of various parameters, such as catalyst, reaction temperature, reaction time, base, solvent and tetra butylammonium bromide (TBAB) were studied for the reaction of iodobenzene with aniline. The catalytic system could tolerate a broad range of amines, such as alkyl amines, aryl amines, amides, imidazole, indole and so on. The corresponding C-N cross-coupled products were obtained in high yield under the optimum condions. Furthermore the catalyst was stable and could be reused in normal atmosphere without suffering appreciable loss in catalytic activity. C-O cross-coupling reaction could also be carried out for hydroxyl compounds with aryl halide in the same systems, which also gave the corresponding C-O cross-coupled products in high yield.