Ultrasmall Cu I Nanoparticles Stabilized on Surface of HPMC: An Efficient Catalyst for Fast and Organic Solvent-Free Tandem Click Chemistry in Water.

A simple and environmentally benign technology for synthesizing ultrasmall Cu nanoparticles (NPs) on the surface of the food additive hydroxypropyl methylcellulose (HPMC) and their application in completely organic solvent-free tandem alkyne-azide cycloaddition reactions were reported. The NP catalyst was thoroughly characterized by high-angle annular dark-field scanning transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analysis for its morphology, particle size distribution, chemical composition, and oxidation state analyses. The NP catalyst was highly efficient, affording products in 10-45 min. All products were obtained in high purity by simple filtration, obviating organic solvents from the reaction set-up to product isolation. The methodology is general and scalable as validated by a broad substrate scope.