Dendrimer-encapsulated Cu() nanoparticles immobilized on superparamagnetic Fe3O4@SiO2 nanoparticles as a novel recyclable catalyst for N-arylation of nitrogen heterocycles and green synthesis of 5-substituted 1H-tetrazoles

摘要

In this study, dendrimer-encapsulated Cu() nanoparticles immobilized on superparamagnetic Fe3O4@SiO2 nanoparticles were prepared via a multistep-synthesis. Then, the synthesized composite was fully characterized by various techniques such as fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), UV-vis spectroscopy, energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA) and vibration sample magnetometer (VSM). From the information gained by FE-SEM and TEM studies it can be inferred that the particles are mostly spherical in shape and have an average size of 50nm. Also, the amount of Cu is determined to be 0.51mmol/g in the catalyst by inductively coupled plasma (ICP) analyzer. This magnetic nano-compound has been successfully applied as a highly efficient, magnetically recoverable and stable catalyst for N-arylation of nitrogen heterocycles with aryl halides (I, Br) and arylboronic acids without using external ligands or additives. The catalyst was also employed in a one-pot, three-component reaction for the efficient and green synthesis of 5-substituted 1H-tetrazoles using various aldehydes, hydroxylamine hydrochloride and sodium azide in water. The magnetic catalyst can be easily separated by an external magnet bar and is recycled seven times without significant loss of its activity.