Polyvinylpolypyrrolidone‐Stabilized Copper Nanoparticles as an Efficient and Recyclable Heterogeneous Catalyst for the Click of 1,2,3‐Triazoles in Water

Abstract

AbstractA simple, efficient, inexpensive, and friendly benign route for the preparation of highly stable monodisperse copper nanoparticles with an average of 4–5 nm is developed by using polyvinylpolypyrrolidone (PVPP) as a stabilizer. Chemical reaction of PVPP and copper(II) sulfate followed by the thermal chemical reduction of embedded copper(II) ions with ascorbic acid afford copper nanoparticles‐polyvinylpolypyrrolidone (CuNPs‐PVPP) nanocatalyst, which is systematically characterized by FT‐IR, Raman, transmission electron microscopy, X‐ray powder diffraction, scanning electron microscopy, dispersive X‐ray spectroscopy, and atomic absorption spectroscopy. The CuNPs‐PVPP system efficiently catalyzes the click chemistry reaction of azides–alkynes as well as one‐pot three‐component reactions to regioselectively produce the 1,4‐disubstituted‐1,2,3‐triazole isomer in excellent yields in water under mild reaction conditions. CuNPs‐PVPP is successfully recycled up to five times without significant loss of its catalytic efficiency and selectivity. Moreover, a mechanistic study is performed through density functional theory type calculations in order to explain the observed selectivity of CuNPs catalyst in copper(I)‐catalyzed azide–alkyne cycloaddition reactions. The cheap, simple work‐up, recoverability/reusability, and negligible residual traces in the final product (0.5 ppm) of this novel nanocatalyst are the significant features of this eco‐friendly green protocol.