The first report on the eco-friendly synthesis of 5- substituted 1H-tetrazoles in PEG catalyzed by Cu(II) immobilized on Fe3O4@SiO2@L-arginine as a novel, recyclable and non-corrosive catalyst

Cu(II) immobilized on Fe3O4@SiO2@L-aginine as a novel, inexpensive and non-corrosive nanostructured compound catalyzed the cycloaddition reaction of various organic nitriles with sodium azide. This combination leads to obtain a series of 5-substituted-1H-tetrazoles under mild reaction conditions in polyethylene glycol (PEG). The structure of the catalyst was studied by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS). Ease of operation, high efficiency, low cost, recovery, and reusability for four continuous cycles are the noteworthy features of the currently employed heterogeneous catalytic system. 1 Introduction Tetrazoles are a class of heterocycles with a wide range of applications that are receiving considerable attention in the recent years.1 Tetrazoles are nitrogen-rich compounds, which can be used in a wide range of applications, such as in material sciences, catalysis technology, information recording systems, explosives, and possible application in high energy chemistry.2 Recently, tetrazole moieties were widely used for binding aryl thiotetrazolylacetanilides with HIV-1 reverse transcriptase.3 Also they form stable complexes with metals4 and have been used as ligands for palladium-catalyzed reactions.5 Because of their potent usefulness, the various methods for the synthesis of tetrazole frameworks are well documented in the literature. In general, the most direct and versatile method for the synthesis of 5-substituted 1H-tetrazoles is [2 + 3] cycloaddition of nitriles and an azide moiety under the inuence of appropriate catalyst and different solvent conditions. Several new catalysts have been investigated, such as zinc salts,6 b-cyclodextrin, 7 Fe(OAc)2,8 CdCl2,9 AgNO3,10 SiO2–H3BO3,11 Cu-MCM- 41,12 and copper triates.13 Although all of these methods are benecial, a number of them have one ormore of the following drawbacks: the use of DMF as solvent, tedious workup of the reaction mixture, reuxing for a prolonged period of time, toxic metals and difficulty in separation and recovery of the catalyst. 14Hence, the choice of a suitable catalyst and environmentally benign method

5- substituted 1H-tetrazoles