T. K. Shkineva

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.

Effects of N-nitropyrazoles on ocular blood flow of rabbits and retinal function recovery of rat eyes after ischemic insults.

Twelve compounds of N-nitropyrazoles were studied for their effects on ocular blood flow in rabbits and retinal function recovery in rat eyes after ischemic insults. Of the twelve N-nitropyrazoles examined, nine increased choroidal blood flow while five increased retinal blood flow significantly. On the other hand, all twelve compounds increased blood flow in iris and ciliary muscle without exception. As for retinal function recovery after ischemic insult in rat eyes, eight out of the twelve compounds showed more significant facilitation than the control. The structure activity relationship of the N-nitropyrazoles to increase ocular blood flow and to facilitate retinal function recovery after ischemic insults were discussed.

Synthesis and investigation of isomeric mono- and dinitro derivatives of 3-methyl-4-(pyrazol-3-yl)furazan

The regioselective introduction of nitro groups in pyrazoles, containing a furazanyl substituent at position 3(5) was investigated. All synthetically accessible isomeric mono- and dinitropyrazole derivatives were obtained. X-ray structural investigation was performed for all mononitroisomers and a dinitro derivative.

Synthesis of 1- and 5-(pyrazolyl)tetrazole amino and nitro derivatives

Regioselective introduction of nitro groups was studied in the case of pyrazoles containing a 1- or 5-tetrazole substituent at position 3(5). All the possible isomeric C-mononitropyrazoles were synthesized. The reduction of these compounds gave the respective 3(5)-amino-5(3)-tetrazolylpyrazoles, which were nitrated to 3(5)-nitramino-4-nitro-5(3)-tetrazolylpyrazoles. The reaction of 1-(nitropyrazol-3(5)-yl)tetrazoles with hydroxylamine-O-sulfonic acid produced the respective N-amino derivatives.

Synthesis and Study of 1,3- and 1,3,3-Substituted Ureas Containing Isoxazole and Adamantane Fragments

A series of 1,3-disubstituted and 1,3,3-trisubstituted isoxazolyl- and adamantyl-functionalized ureas was synthesized. The resulting compounds are potent inhibitors of soluble epoxide hydrolase. The compounds were obtained in high yields under mild conditions. Water solubility of the synthesized ureas was found to exceed significantly that of known analogs.

Synthesis of 1-(N-nitropyrazolyl)-1Н-tetrazoles – a new type of heteronuclear N-nitropyrazole derivatives

A general method has been developed for the synthesis of 1-pyrazolyl-1Н-tetrazoles, and N-nitration of these compounds was studied. The structural features affecting the direction of nitration were identified. A series of 1-(N-nitropyrazolyl)-1Н-tetrazoles was obtained, representing a new type of heteronuclear N-nitropyrazole derivatives.

N-Alkylation and N-amination of isomeric nitro derivatives of 3-methyl-4-(1H-pyrazol-3(5)-yl)furazan

The reaction of bromoacetone and hydroxylamine-О-sulfonic acid with isomeric mono- and dinitropyrazoles containing a furazanyl moiety at position 3(5) gave pairs of regioisomeric products from pyrazole ring N-acetonylation and N-amination, respectively, that were characterized in detail by multinuclear NMR spectroscopy. X-ray structural study of the four synthesized N-amino derivatives indicated a non-planar structure, while the conformational analysis pointed to conformational lability of such molecules, and the role of intermolecular interactions in determining the crystal structure.

Nitropyrazoles 20. Synthesis and transformations of 1-methoxymethyl-3,4,5-trinitropyrazole

Abstract1-Methoxymethyl-3,4,5-trinitropyrazole, synthesized from 3,4,5-trinitropyrazole by the action of methoxymethyl chloride, was involved into the nucleophilic substitution reaction with N-nucleophiles (aliphatic amines, hydrazine derivatives). The reaction was effected regioselectively with substitution of the nitro group at position 5 in good yields. The thus obtained 5-R-substituted compounds under acid hydrolysis conditions give N-unsubstituted 5-R-3,4-dinitropyrazoles.

Bipyrazole bearing ten nitro groups – a novel highly dense oxidizer for forward-looking rocket propulsions

Taking into account the manifold requirements for future rocket industry breakthroughs, the scientific community is currently focusing on the design of novel higher performance, high-tech and environmentally more acceptable materials compared with conventional propellant ingredients for liquid, solid, gelled, and hybrid propellant systems. Earlier, considerable efforts were made to find environmentally friendly chlorine free alternatives to ammonium perchlorate (AP) which is still the main oxidizer for solid propellants; however, success in this way is extremely rare. In this work, a novel oxygen-rich energetic material, 4,4′,5,5′-tetranitro-2,2′-bis(trinitromethyl)-2H,2′H-3,3′-bipyrazole (11), was obtained by N-alkylation of 4,4′,5,5′-tetranitro-2H,2′H-3,3′-bipyrazole (9) with bromoacetone and subsequent nitration. X-ray single-crystal diffraction confirmed its structure and revealed a unique high crystal density of 2.021 g cm−3 at room temperature, introducing it into the top three of the densest CHNO compounds known. This high density material has an attractive positive oxygen balance, acceptable sensitivity, and enthalpy of formation (on a unit of weight) similar to CL-20, with calculated specific and effective impulses exceeding those of AP and ADN, making it a competitive replacement for AP as a green energetic oxidizer for diverse propellants.

Synthesis of 1-Adamantyl-3,4,5-R1,R2,R3-Pyrazoles

A method has been developed for the synthesis of 1-adamantyl-3,4,5-R1,R2,R3-pyrazoles by the reaction of 1,3-dehydroadamantane with N-unsubstituted 3,4,5-R1,R2,R3-1H-pyrazoles in an inert solvent. The effect of the NH acidity (pKa) of the starting 3,4,5-R1,R2,R3-1H-pyrazole on the course of the reaction and the product yields was studied.