Novel high-density oxidizer based on highly nitrated bipyrazole was developed. It is the champion among heteroaromatic CHNO compounds with a density equal to 2.021 g cm−3 at room temperature.

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.

The transformations of readily available 4-chloro-3,5-dinitropyrazole and its N-methylated derivative under the action of anionic S-/O-nucleophiles and neutral N-nucleophiles were studied. Independent of the substrate's charge (anionic, R = H, or neutral, R = Me), the nucleophilic substitution proceeds exclusively at position 4 replacing the chlorine nucleofuge. As a result of this study, the effective synthetic method for the preparation of 4-substituted 3,5-dinitropyrazoles via the nucleophilic substitution in 4-chloro-3,5-dinitropyrazole was elaborated.The current interest in the chemistry of pyrazoles is due to their wide practical applications. During last five years the number of publications on pyrazoles has doubled and is still continuing to grow. 1 Among pyrazoles, the polynitropyrazoles attract special attention because they belong to high-energy compounds and show some specific properties. 2,3 The effective synthetic approaches to 3,4-and 3,5-dinitropyrazoles through direct acid and nonacid nitration, as well as via C → N isomerization of N-nitropyrazoles, are well known. 4 In a series of papers, 5,6 we reported the nucleophilic substitution of NO 2 group in 3,4-and 3,5-dinitropyrazoles to be a quite powerful method for functionalization of C-3 and C-5 atoms of a pyrazole ring with formation of C(3/5)-X bonds (X = O, S, N).For example, it was found that in 3,4-dinitropyrazoles (pK a <6.5 7 ) under the action of heteroatom nucleophiles substitution proceeds selectively at position 3 (Scheme 1, route A). It should be stressed that such a process does not depend on the presence of the substituent at N-1. Even in the case of R = H, when the substrate reacts in its anionic form, only position 3 is functionalized. 5 3,5-Dinitropyrazoles (pK a <4.0 7 ) enter the substitution reaction with the same set of nucleophiles only in the case when a substituent R is present at N-1 (Scheme 1, route B). Otherwise, as a result of an acid-base reaction between NH acid and basic nucleophile, the reaction furnishes the respective salt (Scheme 1, route C). 6,8 All known methods of C-4 functionalization, particularly, in the case of N-unsubstituted pyrazoles, are based on the reactions with the electrophilic reagents. 4Quite recently as a result of our work, 9,10 as well as of Herve et al., 3 the first examples of fully carbon atomnitrated pyrazoles -3,4,5-trinitropyrazole (TNP) and its N-derivatives, 1-methyl-3,4,5-trinitro-1H-pyrazole 10a and 1-methoxymethyl-3,4,5-trinitro-1H-pyrazole 11 -became available for synthetic chemists. On the basis of systematic investigations, we found that the rules of nucleophilic substitution in these novel polynitropyrazoles are different compared to previously known ones. For instance, when TNP 12 in the form of its N-anion reacts with S-, O-, N-nucleophiles, the selective substitution of 4-NO 2 group occurs (Scheme 1, route

A method of preparation of 5 amino 3,4 dinitropyrazole (1) from 3(5) methyl 5(3) nitro and 3(5) methyl 4,5(3) dinitropyrazoles was developed, the key step of which was the Hofmann rearrengement of nitro and dinitropyrazolecarboxamides. The protonation of 5 amino 3,4 dinitropyrazole was studied by spectral methods (UV spectroscopy, NMR spectroscopy). In spite of low basicity of the amino group, compound 1 undergoes N arylation, N nitration, and annulation reactions with formation of dinitropyrazolo[5,1 a]pyrimidine derivatives and hitherto unknown dinitroimidazo[1,2 b]pyrazole derivatives. Diazotization of 1 leads to 5 diazo 3,4 dinitropyrazole (19), which exists in the form of the internal salt. Some reactions of this compound were studied and the formation of the corresponding 5 halogeno(azido) 3,4 dinitropyrazoles under the action of the halide and azide ion was shown. Dinitropyrazolo [5,1 c][1,2,4]triazine and 7 hydroxydinitro 4,7 dihydropyrazolo[5,1 c] [1,2,4]triazine deriva tives were obtained by the action of active methylene compounds on the betaine 19.

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3,4,5‐Trinitro‐1H‐pyrazole (1) has been obtained via nitration of 3,5‐dinitropyrazole with mixture of sulfuric and nitric acids. Compound 1 reacts with excess ammonia and aliphatic amines, in the presence of bases with NH‐azoles, phenols, thiols, and triflouroethanol at mild conditions in water. All these reactions occur as the nucleophilic substitution of the nitro‐group at position 4 in 1 affording 4‐R‐3,5‐dinitropyrazoles. The product of methylation of 1, N‐methyl‐3,4,5‐trinitropyrazole (4), also reacts with thiols, phenols, oximes, ammonia, amines, and NH‐azoles. The reactions proceed with high yields but nucleophilic substitutions in these cases occur regioselectively at position 5 in 4 to afford 5‐R‐3,4‐dinitropyrazoles.