Recent Advances in Tetrazole Chemistry

This chapter discusses the development of tetrazole chemistry from 1965 to 1975. Over the years, it has been noted that the field has grown rapidly, with regard to the industrial interest that the tetrazoles command. Some of the significant areas in this field include the applications of modern physical techniques to tetrazole derivatives and studies of pharmacologically active tetrazoles, particularly, replacement of the carboxylic acid group in known active molecules by its analog—the tetrazole ring. Tetrazole essentially is an aromatic azapyrrole nucleus, which exist in two tautomeric forms. The chapter also describes physicochemical studies. These studies include nuclear magnetic resonance spectroscopy and theoretical calculations, mass fragmentation, tetrazole complexes and crystal structures, and photolysis and tetrazole radicals. Tetrazole can be synthesized by several methods that are also presented in the chapter. In the context of azide-tetrazole isomerism, it is observed that polar solvents tend to favor the tetrazole form and nonpolar solvents the azide form. Another factor that influences this isomerism is the syn-anti isomerism about the C=N moiety.