SO3Cu-Carbon: A Novel Heterogeneous Catalyst for the Synthesis of beta-Hydroxy 1,2,3-Triazoles by One Pot Cycloaddition Reaction

A novel heterogeneous carbon-based sulfonated copper (SO3Cu-carbon) catalyst was developed for the first time and investigated its catalytic activity for the regioselective synthesis of beta-hydroxy 1,2,3-triazoles by azide-alkyne cycloaddition in aqueous medium. The SO3Cu-carbon catalyst was prepared by the modification of the glycerol-based SO3H-carbon catalyst on treatment with 10% aqueous CuCl2 solution under controlled conditions. Based on its physico-chemical characteristics the structure of the catalyst is proposed as a polycyclic aromatic carbon attached with -SO3Cu, -COOCu and -OCu functionalities. The catalytic activity of the SO3Cu-carbon catalyst was demonstrated for the one pot 'click' reaction of epoxide, sodium azide and terminal alkyne in water at 60 degrees C for the synthesis of beta-hydroxy 1,2,3-triazoles in excellent yields (89-94%) without any additives. The formation of the product proceeds in one pot through a mechanism that involves in situ generation of organic azide intermediate followed by rapid ring closure with alkynes. The catalyst was easily recovered by simple filtration and reused for 5 cycles without any leaching and deactivation thus exhibiting its excellent stability and reusability. Moreover, the cascade reaction was best performed in water at moderate temperature, rendering all the processes truly green.