Recent Developments in the Synthesis of Tetrazoles and their Pharmacological Relevance

The heterocycle ring tetrazole is an important moiety relevant to medicinal chemistry since it is present in some drugs with clinical importance. Its primary biological activity is being a bioisosteric analogue of the carboxylic acid and cis-amide groups. Its metabolic stability and other physicochemical properties make it an attractive structure for designing and synthesizing new pharmaceuticals. The biological activity of tetrazoles is quite extensive and includes antiviral, antibacterial, anticancer, antifungal, and antioxidant properties; all of them are discussed in this review. The most effective way to obtain tetrazoles is by azide derivatives, either in the starting materials by the cycloaddition [3 + 2] of organic azides and nitriles or by preparing a reactive imidoyl azide intermediate. The nucleophilic behavior of the azide group is discussed when the raw materials include isocyanides. Some other methods include alternative synthetic routes like thermolysis. This review also highlights some of the developments regarding the use of different heterogeneous catalysts to synthesize several tetrazole derivatives.