Aleksei B. Sheremetev

Monocyclic furazans and furoxans

Publisher Summary This chapter covers the chemistry of monocyclic furazans and furoxans. The aim is to present a general picture of more than a century of development in this field. It focuses more on the reactivity of the side-chain functional groups than on the ring synthesis. A liberal selection of examples for preparations and reactions is offered. Because of the enormous amount of literature no exhaustive coverage of this field is intended. The chapter reviews that the chemistry of furazans and furoxans has been the subject of intensive investigations over the years. There has been a substantial increase in synthetic manipulations of substituents attached to these ring systems. Additionally, there are a number of publications that deal with the incorporation of the heterocyclic rings into more complex molecules.

Novel Highly Energetic Pyrazoles: N-Trinitromethyl-Substituted Nitropyrazoles.

A new family of energetic compounds, nitropyrazoles bearing a trinitromethyl moiety at the nitrogen atom of the heterocycle, was designed. The desirable high-energy dense oxidizers 3,4-dinitro- and 3,5-dinitro-1-(trinitromethyl)pyrazoles were synthesized in good yields by destructive nitration of the corresponding 1-acetonylpyrazoles. All of the prepared compounds were fully characterized by multinuclear NMR and IR spectroscopy, as well as by elemental analysis. Single-crystal X-ray diffraction studies show remarkably high density. Impact sensitivity tests and thermal stability measurements were also performed. All of the pyrazoles possess positive calculated heats of formation and exhibit promising energetic performance that is the range of 1,3,5-trinitroperhydro-1,3,5-triazine and pentaerythritol tetranitrate. The new pyrazoles exhibit positive oxygen balance and are promising candidates for new environmentally benign energetic materials.

Ionic Liquids as Unique Solvents in One‐Pot Synthesis of 4‐(N,2,2,2‐Tetranitroethylamino)‐3‐R‐Furazans

An efficient two-step one-pot protocol for the synthesis of N-nitrated trinitroethylamino furazans in an ionic liquid has been developed involving the condensation of aminofurazans with trinitroethanol and the N-nitration of an intermediate Mannich base. Trinitroethylnitramino derivatives have been synthesized and characterized by multinuclear NMR spectroscopy and X-ray crystallography. A role of the N,2,2,2-tetranitroethylamino group for stabilization of the high-density crystal-packing motif is described. The performance calculations gave detonation pressures and velocities for the furazan derivatives in a range of about 31-36 GPa and 8330-8745 ms(-1), respectively, which makes them competitive energetic materials. Furthermore, due to the positive oxygen balance, the compounds could be potential oxidizers for energetic formulations.

A Direct Approach to a 6-Hetarylamino[1,2,4]triazolo[4,3-b][1,2,4,5]tetrazine Library

The synthesis of 6-hetarylamino[1,2,4]triazolo[4,3-b][1,2,4,5]tetrazines is reported. The functionalized secondary amines were constructed via a K2CO3-mediated SNAr reaction of weakly basic hetarylamines with 3-(3,5-dimethylpyrazol-1-yl)[1,2,4]triazolo[4,3-b][1,2,4,5]tetrazines, which allowed displacement 3,5-dimethylpyrazolyl leaving group. Significantly, the reaction exhibited a broad substrate scope and proceeded in good yields.

Synthesis and X‐Ray Crystal Structure of Bis‐3,3′‐(nitro‐ NNO‐azoxy)‐difurazanyl Ether

Explosive furazans The sequence of introducing the substituents to the target molecule 1, namely initial ether-bond construction and subsequent nitro-NNO-azoxy-group formation, favors the synthesis of this molecule.

A practical anodic oxidation of aminofurazans to azofurazans: an environmentally friendly route

Nickel oxyhydroxide, NiOOH, anode has been shown to be an effective tool for the oxidation of aminofurazans to azofurazans in ca. 1% aqueous alkali at room temperature. The electrochemical reaction is simple and convenient, eliminating the use of expensive and toxic organic or inorganic oxidants. The green economic preparation of desired azo compounds is very clean, producing only H2 as a result of cathodic reduction.

1,2,5-oxadiazoles substituted at ring nitrogen. part 1. synthesis and study of 2-ethyl-1,2,5-oxadiazol-3(2H)-ones.

Abstract The first representatives of the 2-alkyl-1,2,5-oxadiazol-3(2H)-ones have been synthesized by the alkylation of trimethylsilyl derivatives of 3-hydroxyfurazans using triethyl orthoformate. The compounds obtained are investigated by 13C,14N,15N and 17O NMR, MS, IR and UV.

Novel alkynyl(phenyl)iodonium salts: nitrofurazanylate as a counterion

Alkynyl(phenyl)iodonium nitrofurazanylates 6–9 were prepared by reaction of 3-hydroxy-4-nitrofurazan 4 with iodosylbenzene and terminal acetylenes.

Novel trinitroethanol derivatives: high energetic 2-(2,2,2-trinitroethoxy)-1,3,5-triazines

The multicomponent reaction of 2,4,6-trichloro-1,3,5-triazine with potassium trinitromethane and trinitroethanol was exploited for the first synthesis of the hetaryl trinitroethyl ether, 2,4-bis(2,2,2-trinitroethoxy)-6-trinitrometyl-1,3,5-triazine 13. The use of compound 13 as a scaffold for the synthesis of substituted trinitroethoxytriazine by sequential nucleophilic substitution processes is described. A number of trinitroethoxytriazines bearing a range of functional groups, including 2,4,6-tris(2,2,2-trinitroethoxy)-1,3,5-triazine 16, have been prepared. There has been no previous incorporation of the trinitroethoxy moiety to a heteroaromatic ring. All trinitroethoxytriazines were fully characterized using IR and multinuclear NMR spectroscopy, elemental analysis, and differential scanning calorimetry (DSC), and, in some cases, 16, 20 and 21, with single crystal X-ray structuring. When compared to the aliphatic trinitroethoxy compounds, the trinitroethoxytriazines show better energetic performance as calculated. The impact sensitivities and ignition points of the novel oxygen and nitrogen-rich triazines were measured. The ability of the applied trinitroethoxytriazines in solid composite propellants as well as in gas generant compositions for airbag inflators was evaluated. The straightforward preparation of these ethers highlights them as valuable new environmentally friendly and high-performing nitrogen and oxygen-rich materials.

A facile synthesis and microtubule-destabilizing properties of 4-(1H-benzo[d]imidazol-2-yl)-furazan-3-amines

A series of 4-(1H-benzo[d]imidazol-2-yl)-furazan-3-amines (BIFAs) were prepared in good yields (60-90% for each reaction step) via a novel procedure from aminofurazanyl hydroximoyl chlorides and o-diaminobenzenes. The synthetic sequence was run under mild reaction conditions, it was robust and did not require extensive purification of intermediates or final products. Furthermore, there was no need for protection of reactive moieties allowing for the parallel synthesis of diverse BIFA derivatives. Subsequent biological evaluation of the resulting compounds revealed their anti-proliferative effects in the sea urchin embryo model and in cultured human cancer cell lines. The most active compounds showed 0.2-2 μM activities in both assay systems. The unsubstituted benzene ring of the benzoimidazole template as well as the unsubstituted amino group in the furazan ring were essential prerequisites for the antimitotic activity of BIFAs. Compound 57 bearing the 2-chlorophenyl acetamide substituent at the nitrogen atom of the imidazole ring was the most active molecule in the examined set.