A novel and efficient magnetically recoverable copper catalyst [MNPs-guanidine-bis(ethanol)-Cu] for Pd-free Sonogashira coupling reaction

We designed and fabricated a copper complex immobilized on the surface of silica-coated magnetic nanoparticles modified with guanidine-bis ethanol (prepared via the ring-opening reaction of MNPs-guanidine with epoxide). FT-IR spectroscopy, Scanning electron microscope (SEM, Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), Thermogravimetric analysis (TGA), Vibrating sample magnetometer (VSM), X-ray diffraction (XRD), Elemental mapping, Atomic absorption spectroscopy (AAS), Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES) and Elemental mapping-analysis were used to characterize the structure of MNPs-guanidine-bis(ethanol)-Cu nanocatalyst. The MNPs-guanidine-bis(ethanol)-Cu nanocomposite showed high catalytic activity in the Pd-free Sonogashira cross-coupling reactions. The MNPs-guanidine-bis(ethanol)-Cu catalyst was consistent toward a variety of aryl halides bearing amine, acid, aldehyde, nitro, etc., functional groups, where high-to-excellent yields were obtained for all substrates. The copper nanocatalyst could be easily recovered by a simple magnetic separation and recycled at least 8 times without deterioration in catalytic activity.