Pyrazole-Tetrazole Hybrid with Trinitromethyl, Fluorodinitromethyl, or (Difluoroamino)dinitromethyl Groups: High-Performance Energetic Materials

Iodine/DMSO-mediated one-pot access towards 1-aryl-2-(pyrazol-5-yl)ethane-1,2-diones via a domino reaction from functionalized pent-2-ene-1,5-diones

A facile one-pot cascade synthesis involving simultaneous in situ pyrazole formation followed by iodine/DMSO-mediated oxidation has been established to afford 1-aryl-2-(3-aryl)-1H-pyrazol-5-yl-ethane-1,2-diones. Primarily, a two-pot approach has been established which includes the reaction of 3-methylthio-1,5-diaryl-2-pentene-1,5-diones with hydrazine in the first step to afford pyrazole, which was eventually oxidized in the next steps in the presence of iodine in DMSO. Furthermore, we performed both steps in the same pot to afford 1,2-dicarbonyl compounds in good yield. The structure of one of the compounds was confirmed by single crystal X-ray analysis. DMSO served as a solvent as well as an oxidant. Moreover, N-substituted hydrazines provided 1-(1-substituted-3-aryl-1H-pyrazol-5-yl)-2-arylethane-1,2-diones regioselectively. Furthermore, for synthetic application, 1-aryl-2-(3-aryl)-1H-pyrazol-5-yl-ethane-1,2-diones were treated with o-phenylenediamine to afford pyrazole-functionalized quinoxaline in good yield. A control reaction was carried out to understand the mechanism of product formation.

Expanding the Limits of Organic Energetic Materials: High-Performance Alliance of 1,3,4-Thiadiazole and Furazan Scaffolds

A majority of known and newly synthesized energetic materials comprise polynitrogen or nitrogen-oxygen heterocycles with various explosophores. However, available structural combinations of these organic scaffolds are finite and are about to reach their limits. Herein, we present the design and synthesis of a series of sulfur-containing polyazole structures comprising 1,3,4-thiadiazole and furazan rings linked by C-C bonds and enriched with energetic nitro and azo functionalities. In terms of detonation performance, all synthesized 1,3,4-thiadiazole-furazan assemblies (D = 7.7-7.9 km s-1; P = 26-28 GPa) lie between the powerful explosive TATB (D = 8.0 km s-1; P = 31 GPa) and melt-cast material TNT (D = 6.9 km s-1; P = 23 GPa). In the synthesized series, azo-bridged derivative 5 seems to be most practically interesting, as it combines a relatively high energetic performance (D = 7.9 km s-1; P = 28 GPa), a very high thermal stability (271 °C), and insensitivity to friction. By these functional properties, 5 outperforms the benchmark heat-resistant explosive hexanitrostilbene (HNS). To the best of our knowledge, this is the first example of an energetic alliance of furazan and 1,3,4-thiadiazole scaffolds and a rare case of sulfur-containing high-energy materials, which can certainly be considered as an evolutionary step in energetic materials science.

Fluorine-Containing Functional Group-Based Energetic Materials

Molecules featuring fluorine-containing functional groups exhibit outstanding properties with high density, low sensitivity, excellent thermal stability, and good energetic performance due to the strong electron-withdrawing ability and high density of fluorine. Hence, they play a pivotal role in the field of energetic materials. In light of current theoretical and experimental reports, this review systematically focuses on three types of energetic materials possessing fluorine-containing functional groups F- and NF2 - substituted trinitromethyl groups (C(NO2 )2 F, C(NO2 )2 NF2 ), trifluoromethyl group (CF3 ), and difluoroamino and pentafluorosulfone groups (NF2 , SF5 ) and investigates the synthetic methods, physicochemical parameters, and energetic properties of each. The incorporation of fluorine-containing functional moieties is critical for the development of novel high energy density materials, and is rapidly being adopted in the design of energetic materials.

Recent Progress on Nitrogen-Rich Energetic Materials Based on Tetrazole Skeleton

Development of nitrogen-rich energetic materials has gained much attention because of their remarkable properties including large nitrogen content and energy density, good thermal stability, low sensitivity, good energetic performance, environmental friendliness and so on. Tetrazole has the highest nitrogen and highest energy contents among the stable azoles. The incorporation of diverse explosophoric groups or substituents into the tetrazole skeleton is beneficial to obtain high-nitrogen energetic materials having excellent energetic performance and suitable sensitivity. In this review, the development of high-nitrogen energetic materials based on tetrazole skeleton is highlighted. Initially, the property and utilization of nitrogen-rich energetic materials are presented. After showing the advantage of the tetrazole skeleton, the high-nitrogen energetic materials based on tetrazole are classified and introduced in detail. Based on different types of energetic materials (EMs), the synthesis and properties of nitrogen-rich energetic materials based on mono-, di-, tri- and tetra-tetrazole are summarized in detail.

Synthesis, characterization, anticancer and in silico studies of a pyrazole-tethered thiazolidine-2,4-dione derivative

A new pyrazole-tethered thiazolidine-2,4-dione derivative (8) has been synthesized by the Knoevenagel condensation of 3-(4-nitrophenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde (4) and 3-(2,4-dioxothiazolidin-3-yl)propanenitrile (7). The structure of the final compound was confirmed by standard spectroscopic techniques including IR spectroscopy, ¹H-NMR spectroscopy, and ESI-MS mass spectrometry. Molecular features including frontier molecular orbital (HOMO-LUMO) energies, reactivity descriptors and molecular electrostatic potential (ESP) of the title molecule were determined using density functional theory (DFT) calculation. The in vitro cytotoxicity of both the intermediate (4) and final (8) compounds were investigated against cancerous (SW-480 and MCF-7) and normal (HEK-293) cell lines by MTT assay. Compound (8) displayed higher activity than (4) with higher sensitivity against breast cancer cell line and lesser toxicity. The experimental data were further complemented by docking and absorption, distribution, metabolism, and excretion (ADME) studies.Communicated by Ramaswamy H. Sarma.

Novel family of nitrogen-rich energetic (1,2,4-triazolyl) furoxan salts with balanced performance

Nitrogen-rich energetic materials comprised of a combination of several heterocyclic subunits retain their leading position in the field of materials science. In this regard, a preparation of novel high-energy materials with balanced set of physicochemical properties is highly desired. Herein, we report the synthesis of a new series of energetic salts incorporating a (1,2,4-triazolyl) furoxan core and complete evaluation of their energetic properties. All target energetic materials were well characterized with IR and multinuclear NMR spectroscopy and elemental analysis, while compound 6 was further characterized by single-crystal X-ray diffraction study. Prepared nitrogen-rich salts have high thermal stability (up to 232°C), good experimental densities (up to 1.80 g cm⁻³) and high positive enthalpies of formation (344–1,095 kJ mol⁻¹). As a result, synthesized energetic salts have good detonation performance (D = 7.0–8.4 km s⁻¹; p = 22–32 GPa), while their sensitivities to impact and friction are quite low.

An Alliance of Polynitrogen Heterocycles: Novel Energetic Tetrazinedioxide-Hydroxytetrazole-Based Materials

Energetic materials constitute one of the most important subtypes of functional materials used for various applications. A promising approach for the construction of novel thermally stable high-energy materials is based on an assembly of polynitrogen biheterocyclic scaffolds. Herein, we report on the design and synthesis of a new series of high-nitrogen energetic salts comprising the C-C linked 6-aminotetrazinedioxide and hydroxytetrazole frameworks. Synthesized materials were thoroughly characterized by IR and multinuclear NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction and differential scanning calorimetry. As a result of a vast amount of the formed intra- and intermolecular hydrogen bonds, prepared ammonium and amino-1,2,4-triazolium salts are thermally stable and have good densities of 1.75–1.78 g·cm⁻³. All synthesized compounds show high detonation performance, reaching that of benchmark RDX. At the same time, as compared to RDX, investigated salts are less friction sensitive due to the formed net of hydrogen bonds. Overall, reported functional materials represent a novel perspective subclass of secondary explosives and unveil further opportunities for an assembly of biheterocyclic next-generation energetic materials.

Various Techniques for One-Pot Synthesis of 1,3,5-Triazine (s-Triazine) Derivatives: A Review

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Recent studies have shown that one-pot synthesis is a boon for triazines synthesis. One-pot processes had significant success in carrying out complex reactions under mild and eco-friendly conditions. One-pot synthesis is environmentally benign and more economical than other processes in triazines synthesis. The triazine scaffold has provided the starting key point for the design and development of pharmaceutical molecules with wide range of biomedical applications. This review highlights the various methodologies involved for one-pot synthesis of 1,3,5-triazine scaffolds.

Theoretical insight into density and stability differences of RDX, HMX and CL-20

In this work, density and stability differences of RDX, HMX and CL-20 are exploited and addressed through static calculations from views of monomolecular parameters, intermolecular interactions (by the proposed BEC method) and crystal packing.

Energetic Co-Crystal of a Primary Metal-Free Explosive with BTF. Ideal Pair for Co-Crystallization

Co-crystallization is an elegant technique to tune the physical properties of crystalline solids. In the field of energetic materials, co-crystallization is currently playing an important role in the engineering of crystals with improved performance. Here, based on an analysis of the structural features of the green primary explosive, tetramethylammonium salt of 7-oxo-5-(trinitromethyl)-4,5,6,7-tetrahydrotetrazolo[1,5-a][1,3,5]triazin-5-ide (1), a co-former such as the powerful secondary explosive, benzotrifuroxan (BTF, 2), has been proposed to improve it. Compared to the original 1, its co-crystal with BTF has a higher detonation pressure and velocity, as well as an initiating ability, while the impact sensitivity and thermal stability remained at about the same level. Both co-formers, 1 and 2, and co-crystal 3 were characterized by single-crystal X-ray diffraction and their crystal packing was analyzed in detail by the set of approaches, including periodic calculations. In the co-crystal 3, all intermolecular interactions were significantly redistributed. However, no new types of intermolecular interactions were formed during co-crystallization. Moreover, the interaction energies of structural units in crystals before and after co-crystallization were approximately the same. A similar trend was observed for the volumes occupied by structural units and their densifications. The similar nature of the organization of the crystals of the co-formers and the co-crystal gives grounds to assert that the selected co-formers are an ideal pair for co-crystallization, and the invariability of the organization of the crystals was probably responsible for the preservation of some of their properties.

Nitrogen-rich metal-free salts: a new look at the 5-(trinitromethyl)tetrazolate anion as an energetic moiety

A series of energetic nitrogen-rich salts comprised of a 5-(trinitromethyl)tetrazolate anion and high-nitrogen cations was synthesized by simple and efficient chemical routes from readily available commercial reagents. These energetic materials were fully characterized by IR and multinuclear NMR (¹H, ¹³C, ¹⁴N) spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). Additionally, the structure of an energetic salt containing the 3,6,7-triamino-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazolium cation was confirmed by single-crystal X-ray diffraction. The synthesized compounds exhibit decent experimental densities (1.648-1.845 g cm^-3) and positive enthalpies of formation (up to 725.5 kJ mol^-1) and, as a result, superior detonation performance (detonation velocities 8.2-9.2 km s^-1 and detonation pressures 28.5-37.8 GPa), which is comparable to or even exceeding those of commonly used booster explosive PETN. On the other hand, high mechanical sensitivity of several novel 5-(trinitromethyl)tetrazolate salts along with their high combined nitrogen-oxygen content (>81%) and excellent detonation performance render them environmentally friendly alternatives to lead-based primary explosives.

Self-Assembly of Nitrogen-Rich Heterocyclic Compounds with Oxidants for the Development of High-Energy Materials

The development of energetic materials with high energy and low sensitivity has attracted immense interests due to their widespread applications in aerospace technology and national defense. In this work, a promising self-assembly strategy was developed to prepare three high-energy materials (1-3) through the introduction of oxidant molecules into the crystal voids of the parent materials. The structures of these new materials were comprehensively examined by infrared spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and single-crystal X-ray diffraction. In these materials, three unique layer structures with hcb, sql, and interrupted sql topologies were observed, which were formed by the fused-ring-based energetic components. Windows with hexagonal, square, and rectangular structures were observed within these layer structures, which were occupied by H₂O₂, NO₃^-, and ClO₄^-, respectively. Oxidant molecules interacted with parent molecules via hydrogen bonds to form crystal structures of these materials. Moreover, the energetic property of these materials was estimated by computing methods. The calculation results revealed that these self-assembly materials exhibit excellent energetic properties. The highest energetic performance was observed for compound 3. The detonation velocity, detonation pressure, and specific impulse values were up to 9339 m·s^-1, 42.5 GPa, and 308 s, respectively, which were greater than those of HMX. Furthermore, these materials exhibited good sensitivity, which was closely related to their unique crystal structures. The high performance of these materials indicated that the self-assembly strategy should be a promising method for the development of novel energetic materials.

Synthesis of Pyrazoles Utilizing the Ambiphilic Reactivity of Hydrazones

A Brønsted acid-mediated synthesis of pyrazoles from conjugated hydrazones through a β-protonation/nucleophilic addition/cyclization/aromatization sequence was developed. This protocol utilizing the ambiphilic reactivity of hydrazones enables not only self-condensation but also cross-condensation, affording multisubstituted pyrazoles in high yields, with a broad substrate scope. This sequential reaction proceeds under mild conditions via a simple operation. Moreover, the method can be applied to the synthesis of a nonsteroidal anti-inflammatory drug, Lonazolac.

Recent Advances in Synthesis and Properties of Nitrated-Pyrazoles Based Energetic Compounds

Nitrated-pyrazole-based energetic compounds have attracted wide publicity in the field of energetic materials (EMs) due to their high heat of formation, high density, tailored thermal stability, and detonation performance. Many nitrated-pyrazole-based energetic compounds have been developed to meet the increasing demands of high power, low sensitivity, and eco-friendly environment, and they have good applications in explosives, propellants, and pyrotechnics. Continuous and growing efforts have been committed to promote the rapid development of nitrated-pyrazole-based EMs in the last decade, especially through large amounts of Chinese research. Some of the ultimate aims of nitrated-pyrazole-based materials are to develop potential candidates of castable explosives, explore novel insensitive high energy materials, search for low cost synthesis strategies, high efficiency, and green environmental protection, and further widen the applications of EMs. This review article aims to present the recent processes in the synthesis and physical and explosive performances of the nitrated-pyrazole-based Ems, including monopyrazoles with nitro, bispyrazoles with nitro, nitropyrazolo[4,3-c]pyrazoles, and their derivatives, and to comb the development trend of these compounds. This review intends to prompt fresh concepts for designing prominent high-performance nitropyrazole-based EMs.

One-pot synthesis of 1,3,5-triazine-2,4-dithione derivatives via three-component reactions

A catalyst-free one-pot synthetic methodology was developed for the preparation of 1,3,5-triazine-2,4-dithione derivatives through three-component reactions of arylaldehydes, thiourea, and orthoformates. The procedure tolerated a diverse range of arylaldehydes and orthoformates and provided a rapid entry to a variety of 4-aryl-6-(alkylthio)-3,4-dihydro-1,3,5-triazine-2(1H)-thiones (29 examples). The synthetic strategy relies on the dual role of thiourea in the cyclization with the aldehydes and the alkylation via an intermediate imidate formation. The structures of 1,3,5-triazine-2,4-dithione derivatives were characterized by spectroscopic techniques as well as by single crystal X-ray diffraction.

Nitro compounds as the core structures of promising energetic materials and versatile reagents for organic synthesis

This review addresses some promising areas of chemistry of nitro compounds extensively developed in recent years in Russia (particularly at the N.D.Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences) and worldwide. The most important results in the synthesis of novel energetic N-, C- and O-nitro compounds are summarized. New environmentally friendly approaches to the preparation of known compounds of this series, used as components of energetic compositions, are considered. Methods for selective transformations of various nitro compounds to valuable products of organic synthesis, primarily biologically active products and their precursors, are systematically analyzed.

The bibliography includes 446 references.

Synthesis and Characterization of 3-(5-(Fluorodinitromethyl)-1H-1,2,4-triazol-3-yl)-4-nitrofurazan: A Novel Promising Energetic Component of Boron-based Fuels for Rocket Ramjet Engines

The synthesis of a new energetic 1,2,4-triazole compound bearing nitrofurazanyl and fluorodinitromethyl units, which may find use as a component for rocket ramjet engines (RRE), is described. The target product was prepared in a four-step process applying oxidation/nitration/decarboxylation/fluorination reactions and is fully characterized. Its density and structural features were uniquely determined by X-ray analysis. It is shown that replacing HMX with the compound of this study in boron-based fuels gives an increase in energy.

Intermolecular Interactions in Functional Crystalline Materials: From Data to Knowledge

Intermolecular interactions of organic, inorganic, and organometallic compounds are the key to many composition–structure and structure–property networks. In this review, some of these relations and the tools developed by the Cambridge Crystallographic Data Center (CCDC) to analyze them and design solid forms with desired properties are described. The potential of studies supported by the Cambridge Structural Database (CSD)-Materials tools for investigation of dynamic processes in crystals, for analysis of biologically active, high energy, optical, (electro)conductive, and other functional crystalline materials, and for the prediction of novel solid forms (polymorphs, co-crystals, solvates) are discussed. Besides, some unusual applications, the potential for further development and limitations of the CCDC software are reported.

Domino C-H Sulfonylation and Pyrazole Annulation for Fully Substituted Pyrazole Synthesis in Water Using Hydrophilic Enaminones

The cascade reactions between NH₂-functionalized enaminones and sulfonyl hydrazines have been developed for the synthesis of fully substituted pyrazoles. By making use of the hydrophilic primary amino group in the enaminones, the reactions proceed well in the medium of pure water in the presence of molecular iodine, TBHP, and NaHCO₃ via cascade C-H sulfonylation and pyrazole annulation. The cleavage of the C-N bond in enaminones is confirmed by the experiment using ¹⁵ N-labeled enaminone.

N-(2-Fluoro-2,2-dinitroethyl)azoles: a novel assembly of diverse explosophoric building blocks for energetic compound design

The first protocol forN-(dinitrofluoroethyl)ation of azoles has been created.