Ceria-supported copper nanoparticles: A highly efficient and recyclable catalyst for N-arylation of indole

Cu@CeO2 catalytic nanomaterials have been synthesized by impregnation of ceria by copper acetate, followed by reduction and calcination under nitrogen. The components of these nanomaterials were characterized by means of XRD, XPS, N-2 adsorption/desorption, TGA, SEM, and TEM microscopy techniques. The XRD spectra of ceria and Cu@CeO(2-)1 (3.4 wt% copper loading) revealed a slight shift of the position of the planes with a small increase of the crystal lattice parameters, which can be explained by an eventual insertion of Cu-0 in interstitial sites and/or a partial substitution of Ce4+ by Cu2+center dot Cu@CeO2 nanomaterials were found to be efficient catalysts for the N-arylation of indole with various aryl bromides to produce good yields of the desired products. The decrease in the catalytic activity of the catalyst during the reuse was probably due to oxidation of Cu-0 to Cu2+ and its poisoning of KBr that was formed in situ. (C) 2014 Elsevier B.V. All rights reserved.