Preparation of GO/Cys-Cu(II) as a novel, effective and recoverable catalyst for the multi component synthesis of spirooxindoles under mild conditions

Abstract

Modified graphene oxide (GO/CPTES/Cys-Cu(II)) was prepared as a reusable catalyst and characterized by various analytical and spectroscopic methods, including Fourier transform spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and inductively coupled plasma (ICP) techniques. Obtained results from demonstrated the existence of cystein/Cu(II) on the MWCNTs surfaces. EDX and ICP analysis shown about 11% Cu (II) and about 8.5% of N element in the catalyst structure. Also, other characterization data confirmed the successfully preparation of synthesized catalyst. The efficiency of this novel catalyst was evaluated through the green synthesis of two variety of spirooxindole derivatives in a One-pot multi component reaction in ethanol as a green solvent. The catalyst showed high efficiency in this process and all of spirooxindoles were obtained after short time (18 min) in high to excellent yields (89–95%). The structure of all obtained products was assigned with hydrogen and carbon nuclear magnetic resonance (1H and 13C NMR) and FTIR. Furthermore, the catalyst could be easily recovered and directly reused at least five times without a notable reduction in activity. The other advantages of the presented methodology are high yields of products without the formation of by-products, simple and clean process, mild reaction conditions and agreement with green chemistry protocols.