Multicomponent click reaction catalyzed by organic surfactant-free copper sulfide (sf-CuS) nano/micro flowers

Abstract

The azide-alkyne cycloaddition (Huisgen reaction) is one of the most powerful and widely used copper-mediated reactions. In many such reactions, use of metal or metal oxide nanoparticles as the catalyst is more appealing because of the increased catalytic activity attributed to the large surface to volume ratio. However, the nano/micro particles are synthesized often in the presence of long chain organic molecules as capping or stabilizing agents. These organic molecules cover the active centers and restrict or reduce their catalytic activity. Therefore, we have synthesized the copper sulfide (sf-CuS) nano/micro particles without having organic surfactant molecules as the capping agent. These particles with a flower-like architecture (micro flowers, mf) were obtained readily under the supersaturated condition at room temperature. In these particles, the surface was freely available for adsorption and desorption reactions. When utilized as a catalyst in multicomponent cycloaddition reactions, the sf-CuS mf exhibited excellent catalytic activity compared with some other nanoparticles with surfactants. This sf-CuS mf catalyzed the one-pot synthesis of 1,2,3-triazole and β-hydroxy-1,2,3-triazole effectively from a variety of benzyl bromide derivatives epoxides respectively. Both these reactions proceeded in the presence of azide and phenylacetylene in the water at room temperature. The catalyst was reusable, and there was no catalyst leaching observed during reactions. Synthesis of β-hydroxy triazoles and 1,2,3-triazoles under exceptionally mild conditions with high yields proved the sf-CuS mf as the catalyst as a robust and recyclable catalyst.