Efficient methods for the synthesis of 1,2,3,4-tetrazine 1,3-dioxides annulated with five-membered polynitrogen heterocycles

New efficient methods were developed for the synthesis of heterocyclic 1,2,3,4-tetrazine 1,3-dioxides (TDOs) from appropriate amines based on the annulation with nitronium sulfates in organic solvents and also in HNO 3 solutions using weak acid anhydrides. The synthesis of TDOs using P 2 O 5 in an HNO 3 solution requires the preliminary thermal decomposition of intermediate nitro(poly)phosphoric acids. The structure of 2-methyl-2 H -[1,2,3]triazolo[4,5- e ]-[1,2,3,4]tetrazine 1,5,7-trioxide was established by X-ray diffraction.