Gold Nanoparticles Supported on Imidazole-Modified Bentonite: Environmentally Benign Heterogeneous Catalyst for the Three-Component Synthesis of Propargylamines in Water.

Gold nanoparticles supported on imidazole-modified bentonite, Bent@Im@Au NPs, has been developed for the first time as an effective heterogeneous catalyst for the synthesis of propargylamines under mild reaction conditions in water at a loading of 0.07 mol % of Au. Various techniques such as X-ray diffraction, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and element mapping by scanning electron microscopy were used to determine the physicochemical properties of the catalysts. The new gold catalyst was found to be highly active providing high to excellent yields of A3 coupling products via the reactions of various aldehydes, having electron-withdrawing as well as electron-donating substituents, with different amines and alkynes. The catalysts can be easily recovered and reused without significant loss of activity and the recycled catalyst was characterized.