Supported CuO Catalysts Catalyzed Ullmann C-O Coupling Reactions

Diaryl ethers are important construction units in many biologically active compounds. The synthetic method for the synthesis of diaryl ethers was traditional copper catalyzed Ullmann C-O coupling reactions. However, the present homogeneous copper catalytic system, immobilized copper catalytic system and nano-copper catalytic system are problematic in terms of high cost or difficulty in recycling of catalyst. CuO/γ-Al2O3catalyst prepared by impregnation method was applied to the coupling reaction of iodobenzene and m-cresol, reaction afforded70%yield of3-methyldiphenyl ether under ligand free conditions and the catalyst could be reused for four cycles providing the product in moderate yields. According to the characterizations of CuO/γ-Al2O3catalyst, the catalytic activity was due to the highly dispersed Cu(II) species.Copper leaching content of CuO/Al2O3catalysts after the reaction was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and the leaching copper species were proved to be catalytically active. The mechanism of CuO/Al2O3catalyzed coupling reaction of iodobenzene with m-cresol was studied by characterization of intermediate formed by catalysts and reactant.Coprecipitation method and sol-gel method combined with an evaporation-induced self-assembly process were also used to prepare supported CuO/Al2O3catalysts. The synthetic conditions of catalysts including copper loading and calcination temperature were studied. Furthermore, CuO/Al2O3catalyst was used to synthesize pharmaceuticals which contain diaryl ether segment.