Synthesis of 1,2,3,4-tetrazino[5,6-g]benzo-1,2,3,4-tetrazine 1,3,7,9-tetraoxides

1,2,3,4-Tetrazino[5,6-g]benzo-1,2,3,4-tetrazine 1,3,7,9-tetraoxides, which possess an-thracene-type annulation of the benzene ring with two 1,2,3,4-tetrazine 1,3-dioxide fragments, were obtained for the first time from aminobenzenes containing tert-butyl-NNO-azoxy groups in appropriate positions. Complete assignments of the signals in the ¹H, ¹³C, and ¹⁴N NMR spectra of the compounds obtained were carried out. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1595–1599, September, 2006.     

New syntheses of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide

New methods were developed for the synthesis of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide from 4-(tert-butyl-NNO-azoxy)-N-nitro-1,2,5-oxadiazol-3-amine or its alkali metal salts and acid anhydrides (or chlorides) in the presence of strong acids. The yield of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide in acetic anhydride in the presence of sulfuric acid or sulfuric anhydride at 20°C in 20 min attained 83%. A general mechanism was proposed for the reactions under study. Acetyl group behaved for the first time as departing group in the synthesis 1,2,3,4-tetrazine 1,3-dioxides, and [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide was obtained in 47% yield from N-[4-(acetyl-NNO-azoxy)-1,2,5-oxadiazol-3-yl]acetamide.     

Synthesis of amino-substituted 1,3-bis(tert-butyl-NNO-azoxy)benzenes 2.* 2-amino and 2,4-diamino derivatives

Oxidation of one of the amino groups of 2-bromo-4,6-dichloro-1,3-phenylenediamine to the nitroso group followed by its conversion into thetert-butyl-NNO-azoxy group afforded a derivative ofm-(tert-butyl-NNO-azoxy)aniline,viz., 2-bromo-3-(tert-butyl-NNO-azoxyl)-4,6-dichloroaniline. Analogously, the second amino group was converted into thetert-butyl-NNO-azoxy group to form a derivative of 1,3-bis(tert-butyl-NNO-azoxy)benzene,viz., 3-bromo-2,4-bis(tert-butyl-NNO-azoxyl)-1,5-dichlorobenzene The reaction of the latter with ammonia yielded 2-amino- and 2,4-diamino-substituted 1,3-bis-(tert-butyl-NNO-azoxyl)benzenes. For Part 1, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2126–2130, November, 1999.     

Synthesis and structures of pyridoannelated 1,2,3,4-tetrazine 1,3-dioxides

Treatment of 2- and 4-amino-3-(tert-butyl-NNO-azoxy)pyridines with nitrating agents (N₂O₅or NO₂BF₄) afforded the first representatives of pyridoannelated 1,2,3,4-tetrazine di-N-oxides, viz., pyrido[2,3-e][1,2,3,4]tetrazine 1,3-dioxide (9), 7-nitropyrido[2,3-e][1,2,3,4]tetrazine 1,3-dioxide (10), and pyrido[3,4-e][1,2,3,4]tetrazine 2,4-dioxide (11). These compounds were studied by ¹H, ¹³C, and ¹⁴N NMR spectroscopy. The 1:1 complex of compound 10 with benzene was studied by X-ray diffraction analysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2471–2477, November, 2004.     

Generation of oxodiazonium ions 6. Unexpected formation of tetrazole 1-oxides

(E)-2-[2,2-Bis(tert-butyl-NNO-azoxy)-1-(methylsulfinyl)vinyl]-1-isopropoxydiazene 1-oxide reacts with boron trifluoride etherate (BF₃?Et₂O) producing 2-tert-butyl-N-nitro-2H-tetrazolo-5-carboxamide 4-oxide and 2-tert-butyl-2H-tetrazolo-5-carbonitrile 4-oxide but not the expected 1,2,3,4-tetrazine 1,3-dioxide derivative. This reaction direction can be explained by cationic domino cyclization, the key stage of which is coupling of the oxodiazonium ion with the geminal MeS(O) group. Structure of N-nitrocarboxamide was confirmed by X-ray diffraction analysis.     

Electrophilic substitution of thetert-butyl-NNO-azoxy group by the bromine atom

The electrophilic substitution of thetert-butyl-NNO-azoxy group by the bromine atom was observed for the first time when 6-bromo-2,4-bis(tert-butyl-NNO-azoxy)-5-chloro-1,3-phenylenediamine was treated with bromine in AcOH. The structural factors promoting this reaction are discussed. The direction of the replacement was confirmed by PM3 calculations of the heats of formation of intermediate cationic σ-adducts. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2131–2134, November, 1999.     

Syntheis of amino-substituted 1,3-bis(tert-butyl-NNO-azoxy)benzenes

Oxidation of 4,6-dichloro-1,3-phenylenediamine with Caro's acid yields the corresponding dinitrosobenzene, which reacts withN,N-dibromo-tert-butylamine to give 1,5-bis(tert-butyl-NNO-azoxy)-2,4-dichlorobenzene. Treatment of the latter with ammonia yields 4-amino-and 4,6-diamino-1,3-bis(tert-butyl-NNO-azoxy)benzenes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 7, pp. 1307–1310, July, 1999.     

Generation of oxodiazonium ions 4. Nitramine O-alkyl derivatives in the synthesis of benzotetrazine-1,3-dioxides

A new method for the synthesis of benzotetrazine-1,3-dioxides was developed from the 2-(tert-butyl-NNO-azoxy)-N-nitroaniline O-alkyl derivatives upon the action of strong acids (H₂SO₄, MeSO₃H, CF₃CO₂H) or BF₃·Et₂O. A mechanism suggested for these reactions includes transformation of the N=N(O)OR group (R = Me, Prⁱ) to the oxodiazonium ion (N=N=O)⁺, which intramolecularly reacts with the neighboring tert-butyl-NNO-azoxy group, furnishing the tetrazine-1,3-dioxide ring.     

New approach to the synthesis of benzo[e][1,2,3,4]tetrazine 1,3-dioxides

A new approach to the synthesis of benzo[e][1,2,3,4]tetrazine 1,3-dioxides involves the treatment ofN-nitroanilines containing anortho-(tert-butyl-NNO-azoxy) group with phosphoric anhydride or phosphorus pentachloride. The reaction is supposed to proceed through an intermediate diazonium oxide cation. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 3, pp. 480–484, March, 2000.     

Generation of oxodiazonium ions 2. Synthesis of benzotetrazine-1,3-dioxides from 2-(tert-butyl-NNO-azoxy)-N-nitroanilines

A new method for the synthesis of benzotetrazine-1,3-dioxides was developed, which involves the reaction of 2-(tert-butyl-NNO-azoxy)-N-nitroanilines with the Ac₂O/H₂SO₄ system. This method was also used for the synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline-5-oxide from 3-nitramino-4-phenylfurazan. The suggested mechanism of these reactions involves the formation of the intermediate oxodiazonium ion, resulting from acetylation of the oxygen atom of the nitramine group, followed by protonation and ionic dissociation. Then the oxodiazonium ion enters the intramolecular reaction with the neighboring tert-butyl-NNO-azoxy or phenyl group to form the corresponding heterocyclic systems.     

2-Alkyl-4-amino-5-(tert-butyl-NNO-azoxy)-2H-1,2,3-triazole 1-oxides: synthesis and reduction

A new approach to the synthesis of 4-amino-5-(tert-butyl-NNO-azoxy)-2-R-2H-1,2,3-triazole 1-oxides 1 was developed. Compounds 1 were obtained by reactions of 3-amino-4-(tert-butyl-NNO-azoxy)furoxan with aliphatic amines RNH₂ (R = Me, Et, Prⁱ, Bu, and Bu^t). 4-Amino-5-(tert-butyl-NNO-azoxy)-2-tert-butyl-2H-1,2,3-triazole 1-oxide was transformed under the action of acids into 4-amino-5-(tert-butyl-NNO-azoxy)-1-hydroxy-1H-1,2,3-triazole. Methylation of the latter with diazomethane mainly involves the O atom of the triazole oxide ring. Reduction of compounds 1 gave 4-amino-5-(tert-butyl-NNO-azoxy)-2-R-2H-1,2,3-triazoles and 4-amino-5-(tert-butyldiazenyl)-2-R-2H-1,2,3-triazoles (R = Me, Prⁱ, and Bu^t). The structures of the compounds obtained were confirmed by ¹H, ¹³C, and ¹⁴N NMR spectroscopy.     

The tert-butyl-NNO-azoxy group in the synthesis of 1,2,4-benzotriazin-3(4H)-one 1-oxides

Treatment of 2-(tert-butyl-NNO-azoxy)anilines with phosgene at 20 °C was proposed as a novel route to 1,2,4-benzotriazin-3(4H )-one 1-oxides. This method involves a new reaction, viz., an intramolecular interaction of the tert-butyl-NNO-azoxy group with a C-electrophile (leading to the formation of the N(2)—C(3) bond of the triazine ring) followed by elimination of the tert-butyl group. Complete assignment of the signals in the ¹H and ¹³C NMR spectra of the compounds obtained was performed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1507–1509, August, 2007.     

Synthesis of 1,2,3,4-tetrazine 1,3-dioxides annulated with 1,2,3-triazoles and 1,2,3-triazole 1-oxides

1,2,3,4-Tetrazine 1,3-dioxides annulated with 1,2,3-triazoles and 1,2,3-triazole 1-oxides have been synthesized by the reaction of 4-amino-5-(tert-butyl-NNO-azoxy)-2-R-2H-1,2,3-triazoles (R=Me, i-Pr, t-Bu) and their 1-oxides (R=H, Me, Et, i-Pr) with the HNO₃/H₂SO₄/Ac₂O system. Their thermal stability, spectroscopic, and X-ray properties have been studied.     

Amino(tert-butyl-NNO-azoxy)furoxans: synthesis, isomerization, and rearrangement of N-acetyl derivatives

3-Amino-4-(tert-butyl-NNO-azoxy)furoxan (1a) and 4-amino-3-(tert-butyl-NNO-azoxy)-furoxan (1b) and their acetyl derivatives 6a,b were obtained. The equilibria 1a ai 1b and 6a ? 6b were studied. Furoxan 6b can undergo thermal rearrangement into 3-[(tert-butyl-NNO-azoxy)(nitro)methyl]-5-methyl-1,2,4-oxadiazole (7), prolonged heating of which gives N-(2-tert-butyl-5-nitro-1-oxido-2H-1,2,3-triazol-4-yl)acetamide (8). With the transformation 7 → 8 as an example, the possibility of participation of the azoxy group in the Boulton-Katritzky rearrangements was demonstrated for the first time.     

Synthesis of brominated 2-(tert-butyl-NNO-azoxy)anilmes

2-(tert-Butyl-NNO-azoxy)aniline was prepared by selective reduction of 2-(tert-butyl-NNO-azoxy)nitrobenzene. Its bromination yielded the correspondingpara-bromo- andortho, para-dibromoanilines (3a,b).meta-Bromoanilines (6a,b) were synthesized by selective replacement of theortho-bromine atoms in ortho,para-bromo(tert-butylazoxy)benzenes (5a,b) by ammonia in toluene under pressure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1620–1623, September, 1994.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-18461).     

Transformations of 3(4)-amino-4(3)-(<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">NNO</Emphasis>-azoxy)furoxans in the annulation reactions into 1,2,3,4-tetrazine 1,3-dioxides

Reactions of 3(4)-amino-4(3)-(tert-butyl-NNO-azoxy)furoxans with excess (NO₂)₂S₂O₇ or with a HNO₃—H₂SO₄—Ac₂O mixture unexpectedly produce [1,2,5]oxadiazolo[3,4-e]?[1,2,3,4]tetrazine 4,6-di-N-oxide (furazanotetrazine dioxide) and products of amino group oxidation (mainly to the corresponding azofuroxans) instead of the expected furoxanotetrazine dioxides. In some cases, individual (Z)-3,3´-((E)-diazene-1,2-diyl)-bis-((Z)-2-tert-butyl-1-oxidodiazenyl)-1,2,5-oxadiazole 2-oxide) was isolated. Formation of furazanotetrazine dioxides was observed in the reaction of 3-nitramino-4-(tert-butyl-NNO-azoxy)furoxan sodium salt with H₂SO₄ in Ac₂O. Quantum chemical calculation at the DFT/B3LYP/6-31G(d) level of theory was used to estimate several aspects of the reactivity of 3(4)-nitramino-4(3)-(tert-butyl-NNO-azoxy)furoxans in a comparison with 3(4)-nitramino-4(3)-phenylfuroxans and the possible causes of the observed transformations were revealed.     

An unusual cascade of <Emphasis Type="Italic">S</Emphasis><Subscript>N</Subscript> reactions of benzotetrazine 1,3-dioxide derivatives

An unusual cascade of S _NAr reactions was discovered in the series of benzo-1,2,3,4-tetrazine 1,3-dioxides containing two adjacent nucleofuges X and Y in the benzene ring. First, the 1,2,3-triazole anion displaces the anion X^s- from the more reactive site. Then the nucleo-phile X^s- displaces the adjacent group Y. For instance, 1,2,3-triazole reacts with 6-azido-5-nitrobenzotetrazine 1,3-dioxide to give 5-azido-6-(1,2,3-triazol-2-yl)benzotetrazine 1,3-dioxide, with 8-azido-7-nitrobenzotetrazine 1,3-dioxide to give 7-azido-8-(1,2,3-triazol-2-yl)benzotetrazine 1,3-dioxide and 7-azido-8-(1,2,3-triazol-1-yl)benzotetrazine 1,3-dioxide, and with 7-bromo-6-(phenylthio)benzotetrazine 1,3-dioxide to give 7-phenylthio-6-(1,2,3-triazol-2-yl)benzotetrazine 1,3-dioxide.     

Aliphatic α-nitroalkyl-<Emphasis Type="Italic">ONN</Emphasis>-azoxy compounds and their derivatives

Interaction of primary amines and 2,2-dimethyl-5-nitro-5-nitroso-1,3-dioxane in the presence of dibromoisocyanurate generates 2,2-dimethyl-5-nitro-1,3-dioxan-5-yl-ONN-azoxyalkanes. Based on the reaction of the latter with AcCl/MeOH followed by further transformations, the first representatives of mononitro- and polynitroalkyl-ONN-azoxyalkanes, i.e., (methyl-NNO-azoxy)nitromethane and dinitro(methyl-NNO-azoxy)methane, as well as some their derivatives, were prepared.     

Synthesis of Tetrazino‐tetrazine 1,3,6,8‐Tetraoxide (TTTO)

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.     

5,5-Bis(alkoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxides. Synthesis and X-ray diffraction study

2,2-Bis(alkoxy-NNO-azoxy)propane-1,3-diols reacted with thionyl chloride to give previously unknown 5,5-bis(methoxy-NNO-azoxy)- and 5,5-bis(ethoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxides. Replacement of the hydroxy groups by chlorine is a minor reaction path. According to the X-ray diffraction data, the heteroring in the molecule of 5,5-bis(methoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxide adopts a chair conformation with axial orientation of the S=O bond.