2-Aminoethanesulfonic Acid Immobilized on Epichlorohydrin Functionalized Fe3O4@WO3 (Fe3O4@WO3-EAE-SO3H): A Novel Magnetically Recyclable Heterogeneous Nanocatalyst for the Green One-Pot Synthesis of 1-Substituted-1H-1,2,3,4-Tetrazoles in Water

In this research 2-aminoethanesulfonic acid immobilized on epichlorohydrin functionalized Fe3O4@WO3 (Fe3O4@WO(3)EAE-SO3H) has been introduced as a novel and efficient magnetic nanocatalyst for appropriate and rapid synthesis of 1-substituted-1H-1,2,3,4-tetrazoles. This new nanocatalyst was then characterized using FT-IR, XRD, TEM, EDS, TGA, FE-SEM, CHNS and VSM techniques. The above experimental results allowed determination of the composition of Fe3O4@WO3-EAE-SO3H and clearly revealed that the nano-particles are spherical in shape with particle size in the range of 7-23nm and superparamagnetic behavior. Fe3O4@WO(3)EAE-SO3H as an excellent replacement for Bronsted acids was shown to be highly efficient in the rapid preparation of 1-substituted-1H-1,2,3,4-tetrazoles through the cyclization reaction of various primary amines, triethyl orthoformate and 1-butyl-3-methylimidazolium azide ([bmim][N-3]). Compared with conventional methods, the present protocol has considerable advantages such as short reaction time, mild reaction conditions, easy work-up, pure products with high yields, catalyst recovery using an external magnet and reuse of the catalyst several times without noticeable deterioration in catalytic activity. In addition to the aforementioned favourable properties, the remarkable feature of the present protocol is the use of water as environmentally benign solvent, which eliminates the use of toxic solvent.