V. P. Zelenov

Synthesis of 1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 4,6-dioxide and its methyl derivatives

Abstract1H-[1,2,3]Triazolo[4,5-e][1,2,3,4]tetrazine 4,6-dioxide (3) was synthesized by reduction of 1-hydroxy-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxide (1) with PCl3, reduction of 1-methoxy-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxide (4) with Na2S2O4, and by the reaction of compound 4 with Et3N. Both methylation of compound 3 with diazomethane and reaction of Ag-salt of compound 3 with MeI occur at the triazole cycle to give all three possible isomers. The structures of the synthesized compounds were confirmed by 1H, 13C, 14N, and 15N NMR spectroscopy.

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

Abstract3-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.

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 But). 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 But). The structures of the compounds obtained were confirmed by 1H, 13C, and 14N NMR spectroscopy.

Alkylation of 1-hydroxy-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxide

Alkylation of 1-hydroxy-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxide 1 and its silver salt 10 with different alkylating agents (diazomethane, diazoacetone, bromoacetone, α-bromoacetophenone, methyl iodide, methyl vinyl ketone) was studied. Alkylation of compound 1 with diazo compounds and salt 10 with halocompounds results predominantly in O-alkylation products, 1-alkoxy-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxides. The Michael reaction of compound 1 with methyl vinyl ketone involves the triazole nitrogen atom to give 1-(3-oxobutyl)-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 3,4,6-trioxide. The structures of the compounds synthesized were established by 1H, 13C, 14N NMR spectroscopy and mass spectrometry.

Oxodiazonium ion generation 5. 3-(N-Nitroamino)-4-phenylfuroxan: synthesis and reactivity

Abstract3-(N-Nitroamino)-4-phenylfuroxan, the first representative of the furoxan series that contains the N-nitroamino group in position 3 of the furoxan ring, was obtained. This compound is not very stable; its structure was confirmed by chemical transformations into an ammonium salt and N- and O-methyl derivatives. Under standard conditions for oxodiazonium ion generation from nitramine, 3-(N-nitroamino)-4-phenylfuroxan underwent a transformation into the corresponding azofuroxan, viz., 3,3′-diazenediylbis(4-phenyl-1,2,5-oxadiazole 2-oxide), while the O-methyl derivative of 3-(N-nitroamino)-4-phenylfuroxan yielded 2-hydroxyimino-2-phenylacetonitrile. The changed reactivity of the oxodiazonium ion was explained by its intramolecular interaction with the exocyclic O atom of the furoxan system.

Synthesis of first representatives of 5-diazo-1,2,3-triazol-4-ones

A new intramolecular reaction involving neighboring (tert-butyl-NNO-azoxy) and N-nitroamine groups was found, which gave the first representatives of 5-diazo-1,2,3-triazol-4-ones: 3-acetoxy- and 3-hydroxy-5-diazo-3,5-dihydro-4H-1,2,3-triazol-4-ones. The structure of the products was confirmed by X-ray diffraction and NMR spectroscopy data.

Transformations of 3(4)-amino-4(3)-( tert -butyl- NNO -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.