Copper(II)-Schiff Base Complex-Functionalized Polyacrylonitrile Fiber as a Green Efficient Heterogeneous Catalyst for One-Pot Multicomponent Syntheses of 1,2,3-Triazoles and Propargylamines

A series of copper(II)-Schiff bases-functionalized polyacrylonitrile fiber catalysts were successfully prepared using copper acetate as copper source and characterized by elemental analysis, fourier-transfer infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy and inductively coupled plasma analysis. Excellent physical strength and thermal stability of the fiber catalysts were demonstrated by scanning electron microscopy, X-ray diffraction, thermogravimetric/differential scanning calorimetry analysis and mechanical strength measurements. Furthermore, these catalysts were successfully applied to one-pot multicomponent copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and aldehyde, alkyne, amine (A3) coupling reaction in which the influences of different substituent groups on the catalytic activities of fiber catalysts were investigated in detail. Among them, the bis[N-ethyl-3,5-di-tert-butyl-salicylideneiminato]copper(II)-functionalized polyacrylonitrile fiber (PAN(S2)F-Cu) as a green, efficient catalyst exhibited the best catalytic activity for its high hydrophobic micro-environment can aggregate the reactants to the catalytic sites and accelerate the reaction. In addition, the PAN(S2)F-Cu has performed well in scaled-up experiment and shown excellent recyclability (at least ten times), and these enable it to have great potential for further applications.