Novel Method for the Synthesisof s-Triazolo[3,4-b][1,3,4]thiadiazines

The reaction of 4-amino-3-mercapto-5-phenyl-s-triazole with aromatic or aliphatic ketones containing active α-hydrogens as a methyl or methylene group using an acidified acetic acid method afforded the corresponding s-triazolo[3,4-b][1,3,4]thiadiazines. In a similar way, applying the same reaction with cyclic ketones afforded the corresponding tricyclic compounds. Interaction of 4-amino3-mercapto-5-phenyl-s-triazole with chloroacetonitrile under the same reaction conditions directly gave the cyclized 6-amino-s-triazolo[3,4-b][1,3,4]thiadiazine derivative. On treatment of 4-amino-3-mercapto-5-phenyl-s-triazole with acetonitrile or ethyl cyanoacetate under the same reaction conditions, an s-triazolo[3,4-b][1,3,4]thiadiazole derivative was obtained; the reaction carried out with malononitrile or cyanoacetamide gave an alternative s-triazolo[3,4-b][1,3,4]thiadiazole derivative. The mechanism of the reactions was investigated and the structures of all new compounds were elucidated using IR, 1 H NMR, 13 C NMR and mass spectroscopic data, and elemental analyses.