Gum Acacia Stabilized Ag-TiO2 and Ag-SiO2: Sustainable Nanocatalysts for Direct and Convenient Synthesis of 5-Substituted 1H-tetrazoles

Abstract

We describe the use of biocompatible gum acacia (GA)-assembled Ag-TiO2 and Ag-SiO2 nanostructures as effective heterogeneous catalysts for the synthesis of 5-substituted 1H-tetrazoles through the traditional [3+2] cycloaddition of aryl nitriles with sodium azides. Characterization of the prepared catalysts employing TEM, XPS, FE-SEM, FT-IR, XRD, and TGA-DTG reveals silver nanoparticles encapsulated in the GA matrix amidst modified nano titania or silica. A variety of structurally divergent aryl nitriles were converted into the corresponding tetrazoles in a short reaction time. Other advantages include low catalytic load, easy handling of catalyst, limited use of toxic reagents, and desirable conversion yields, making this protocol a viable and practical alternative for this cyclization. The catalysts can be easily recovered and reused over multiple cycles without significant loss of catalytic activity.