Zn@CS: An Efficient Cu-Free Catalyst System for Direct Azide-Alkyne Cycloadditions and Multicomponent Synthesis of 4-Aryl-NH-1,2,3-triazoles in H.sub.2O and DES

A highly efficient recoverable and reusable heterogeneous Zn-catalyst, chitosan supported ZnSO.sub.4. 7H.sub.2O (designated as Zn@CS) is synthesized via a simple synthetic route. Low catalyst loading, need of aqueous reaction media and sharp reduction of time requirement in comparison to the previously reported methodologies are some special features of the established Zn catalyzed direct azide-alkyne cycloaddition reaction. Zn@CS-catalyst is also suitable for multicomponent synthesis of 4-aryl-NH-1,2,3-triazoles from different derivatives of benzaldehyde. An inexpensive and environmentally benign deep eutectic solvent (DES), ChCl:PEG-400:Glycerol as a suitable reaction media accelerates these reactions leading to excellent yields of NH-triazoles. Based on literature report a plausible mechanism has been suggested for ZnAAC reaction.