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This study presents the first synthesis and characterization of a new high energy compound [1,2,3,4]tetrazino[5,6-e][1,2,3,4]tetrazine 1,3,6,8-tetraoxide (TTTO). It was synthesized in ten steps from 2,2-bis(tert-butyl-NNO-azoxy)acetonitrile. The synthetic strategy was based on the sequential closure of two 1,2,3,4-tetrazine 1,3-dioxide rings by the generation of oxodiazonium ions and their intramolecular coupling with tert-butyl-NNO-azoxy groups. The TTTO structure was confirmed by single-crystal X-ray.

Thermal cyclization of 3 R 5 chloro 1,2,4 triazoles (R = Cl, Ph) afforded 2,6,10 tri R tris [1,2,4]triazolo [1,5 a:1´,5´ c:1″,5″ e] [1,3,5]triazines 5 (R = Ph) and 7 (R = Cl). These compounds are first representatives of this class of heterocycles, whose structures were unam biguously established. Treatment of these compounds with nucleophiles (H 2 O/NaOH, NH 3 ) results in the triazine ring opening to give compounds consisting of three 1,2,4 triazole rings linked in a chain. For example, treatment of cyclic compound 5 with aqueous alkali affords 3 phenyl 1 {3 phenyl 1 (3 phenyl 1H 1,2,4 triazol 5 yl) 1,2,4 triazol 5 yl} 1H 1,2,4 triazol 5 one. Treatment of 3,7,11 triphenyltris[1,2,4]triazolo[4,3 a:4´,3´ c:4″,3″ e][1,3,5]tri azine (2) with HCl/SbCl 5 leads to the triazine ring opening giving rise to 5 (3 chloro 5 phenyl 1,2,4 triazol 4 yl) 3 phenyl 4 (5 phenyl 1H 1,2,4 triazol 3 yl) 1,2,4 tri azole. Thermal cyclization of the latter produces 3,7,10 triphenyltris [1,2,4]triazo lo[1,5 a:4´,3´ c:4″,3″ e][1,3,5]triazine (13). Thermolysis of both cyclic compound 2 and cy clic compound 13 is accompanied by the Dimroth rearrangement to yield 3,6,10 triphenyl tris[1,2,4]triazolo[1,5 a:1´,5´ c:4″,3″ e][1,3,5]triazine (14). Compounds 13 and 14 are the first representatives of cyclic compounds with this skeleton. 13 C NMR spectroscopy allows the determination of the isomer type in a series of tris[1,2,4]triazolo[1,3,5]triazines.The 1,2,4 triazole ring can be fused to the 1,3,5 tri azine ring in two ways to give the structure А or B. Let us denote the 1,2,4 triazole ring involved in the struc tures А and B as the X ring and Y ring, respectively. Tris[1,2,4]triazolo[1,3,5]triazine in which the triazine ring is fused to three triazole rings is designated as TTT.In the early 20th century, the first tris[1,2,4]triazolo[1,3,5]triazine was prepared by heating 3,5 diamino 1,2,4 triazole (guanazole). 1 The authors of the cited paper 1 assigned structure Y 3 TTT 1a to this compound (Scheme 1) and called it pyroguanazole. More recently, structure X 3 TTT 1b was proposed 2 for this com pound based on its chemical behavior. However, the as signment is not conclusive and, in essence, the choice between structures 1а and 1b was not made.Triphenyl substituted compound 2 with the structure X 3 TTT was prepared by Huisgen et al. 3 by the reaction of cyanuric chloride with 1 phenyltetrazole (Scheme 2). The reaction mechanism involving the intermediate forma tion of nitrile imine C unambiguously determines the X 3 structure of compound 2, and the relatively low ther molysis temperature excludes the possibility of a skeletal rearrangement (for details, see below).To our knowledge, the above compounds are the only known tris[1,2,4]triazolo[1,3,5]triazines. Scheme 1

Benzo‐1,2,3,4‐tetrazine 1,3‐dioxides (BTDOs) represent fairly stable high‐nitrogen systems, incorporating two head‐to‐tail linked azoxy groups. The synthetic pathway to these heterocycles suggested the use of the tert‐butyl‐NNO‐azoxy group as a building block, allowing the first azoxy group to be incorporated into the ring. The second azoxy group was added with the help of the oxodiazonium ion (−N=N=O+) or its synthetic equivalent. This could be generated by two new methods. The first of these involved treatment of N‐nitroamines with nitrating agents, and the second treatment of diazonium salts with peracids in the presence of a base. The proposed key stage in the tetrazine 1,3‐bis(N‐oxide) ring formation is the reaction between the oxodiazonium ion and the distal nitrogen atom of the tert‐butyl‐NNO‐azoxy group, followed by elimination of the tert‐butyl cation. The syntheses of bromo‐BTDOs 3b−f and nitro‐BTDOs 4a−c are described. The BTDOs were characterized by NMR, including 14N and 15N experiments. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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