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

• N-arylation of indole with various aryl bromides was carried out in good to excellent yields using a nanostructured catalysis: Cu@CeO2.
• This nanostructured catalysis based on ceria-supported copper nanoparticles was synthesized and characterized by several advanced analysis techniques.
• The initial trials were performed to optimize the reaction conditions by varying different parameters using a model reaction.
• Using the optimized conditions, the scope was extended of this catalyzed N-arylation of indole to the use of various aryl bromides.

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, N2 adsorption/desorption, TGA, SEM, and TEM microscopy techniques. The XRD spectra of ceria and Cu@CeO2_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 Cu0 in interstitial sites and/or a partial substitution of Ce4+ by Cu2+. 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 Cu0 to Cu2+ and its poisoning of KBr that was formed in situ.

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