An efficient, reusable copper-oxide/carbon-nanotube catalyst for N-arylation of imidazole

Copper oxide nanoparticles (CuONPs) were successfully decorated on acid treated multi-wall carbon nanotubes (f-MWCNTs) using copper acetate precursor by a very simple “mix and heat” method, and was used as a heterogeneous nanocatalyst for the N-arylation of imidazole for the first time. The transmission electron microscopic (TEM) images of the prepared nanocatalyst (CuO/MWCNT) showed a good adhesion of CuONPs on anchoring sites of the MWCNTs. The factual loading of Cu in CuO/MWCNT was 7.64 wt% as confirmed by inductively coupled plasma-mass spectrometry (ICP-MS). The chemical state of Cu on MWCNTs was +2 as revealed by wide angle X-ray diffraction (WAXD), X-ray photoelectron spectroscopic (XPS) and temperature programmed reduction (TPR) techniques. Initially the reaction conditions were optimized and then the scope of the catalytic system was extended with different aryl halides. 0.98 mol% (5 mg) of the catalyst was sufficient for N-arylation of imidazole. A literature survey showed that this is the smallest amount of catalyst used for this reaction in research reported to date. The CuO/MWCNT is chemically as well as physically very stable, heterogeneous in nature and reusable. After the catalytic reaction, MWCNTs were successfully separated from the used CuO/MWCNT and characterized by Raman, TEM and WAXD.