Fe3O4-chitosan immobilized Cu(II) Schiff base catalyst for the microwave-assisted amination of aryl halides in water

Abstract

This work represents the synthesis, characterization, and application of a magnetically separable (Fe3O4@CS@AF@Cu) catalyst for the C-N coupling reaction towards arylation of amines. The catalyst is synthesized by modifying the surface of Fe3O4-chitosan with acetyl-2-furan (AF) via the formation of Schiff base and then, generating a Cu(II) complex on the functionalized surface. State-of-art characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), X-ray diffractometer (XRD), x-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-optical emission (ICP-OES) spectrometry have been used to verify the structure of the catalyst. Under microwave irradiation, the Ullmann C-N coupling reactions using various aryl halides and amines demonstrate exceptional catalytic performance with a minimal catalyst loading of 0.63 mol% of Cu. Furthermore, the catalyst has been recycled 5 times with 96% efficiency for the amination of 1-bromo-4-nitrobenzene with piperidine under the investigated conditions. Overall, this study provides a practical approach to the synthesis of an effective heterogeneous catalyst for the C-N coupling reaction, which can be used in pharmaceuticals, bulk, and fine chemical industries.