Click Chemistry in zeolites: Copper(I) zeolites as new heterogeneous and ligand-free catalysts for the Huisgen [3+2] cycloaddition

For the first time, copper(l)exchanged zeolites were developed as catalysts in organic synthesis. These solid materials proved to be versatile and efficient heterogeneous, ligand-free catalytic systems for the Huisgen [3+2] cycloaddition. These cheap and easy-to-prepare catalysts exhibited a wide scope and compatibility with functional groups. They are very simple to use, easy to remove (by filtration), and are recyclable (up to three times without loss of activity). Investigations with deuterated alkynes and deuterated zeolites proved that this Cu-I-zeolite-catalyzed "click" reaction exhibited a mechanism different from that reported for the Meldal-Sharpless version.