Efficient synthesis of 5-substituted tetrazoles catalyzed by Ni-S-methylisothiourea complex supported on boehmite nanoparticles

Tetrazoles, being an interesting class of nitrogen-rich heterocycles, wide range of applications as drugs in pharmaceuticals, in coordination chemistry, in synthetic organic chemistry, in catalysis technology, in medicinal chemistry, in the photographic industry, in organometallic chemistry and in various materials science applications including propellants. Also, tetrazoles and their derivatives have been reported as analgesic, antiviral, antiinflammatory, anti-proliferative, antibacterial, potential anti HIV drug candidate, antifungal, herbicidal and anticancer agents. Therefore, recently, many catalysts have attracted increasing interest in the context for synthesis of tetrazole derivatives [1, 2]. In order to combine the advantages of both homogeneous and heterogeneous catalysis, immobilization of homogeneous catalysts on heterogeneous nanomaterials have been widely used as efficient and reusable catalysts for synthesis of tetrazole derivatives. But, some of nanomaterial are expensive or unstable. Also, synthesis of other nanoparticles require inert atmosphere or high temperature for calcination or preparation [3]. While, boehmite nanoparticles is not air or moisture sensitive, and can be prepared in water at room temperature. Boehmite nanoparticles have several advantages such as non-toxicity, stability, high specific surface area, ease of surface modification due to many hydroxyl groups on its surface, inexpensive and easily and readily available. Several methods have been reported for synthesis of boehmite nanoparticles; but, most of them have focused on the effect of temperature, ultrasonic waves, time and Al/OH molar ratio on morphologies, chemical and physical properties of the prepared particles. Meanwhile, nanoboehmite has been rarely used as support for catalyst [4]. Therefore herein a Nickel S-methylisothiourea complex immobilized on boehmite nanoparticles (Ni-SMTU@boehmite) has been reported as organometal nanocatalyst for the synthesis of 5-substituted 1H-tetrazole derivatives using nitriles and sodium azide in PEG- 400.