2,4,4,8,8-Pentanitro-2-Azaadamantane: A High-Density Energetic Compound

Construction of an All-Bridge Carbon-Oxidized 2-Azaadamantane Skeleton and Synthesis of Two Energetic Derivatives

The construction of an all-bridge-oxygenated (hetero)adamantane skeleton is a long-standing challenge. Herein, an all-bridge carbon-oxidized 2-azaadamantane skeleton, 6,9,10-trimethoxy-2-azaadamantane-4,8-diol, was constructed via an eight-step synthetic route from 9-hydroxybicyclo[3.3.1]nonane-2,6-dione with an overall yield of 45%. The obtained skeleton was derived into two novel high-performance energetic compounds. Among them, 2,9,9,10,10-pentanitro-2-azaadamantane-4,6,8-triyl trinitrate is the first example that possesses eight explosophoric groups on the adamantane skeleton.

Computational study of nitrogen-rich hexaazaadamantane cage compounds as potential energetic materials

CONTEXT

Nitrogen-rich carbocyclic cage compounds serve as versatile platforms for the design and development of explosives with tailored properties. Their compact and rigid structure due to efficient packing leads to high crystal density. Moreover, their structural characteristics and amenability to functionalization make them indispensable in the quest for more powerful and efficient energetic materials. Adamantane derivatives are promising candidates for high-energy materials due to their unique molecular structure and the ability to introduce explosophoric groups onto their scaffold. In this computational study, we investigated the effects of substitution of six different explosophoric groups on the hexaazaadamantane skeleton. We explore the incorporation of - N(O)- NNO2, - N(O)- NCN, - N3, - ONO2 - NO2, and - NH2 functionalities, renowned for their high-energy content and ability to enhance explosive properties. We predict the electronic structure, heat of formation, thermodynamic stability, impact sensitivity, and detonation performance of these azaadamantane derivatives. The results indicate that the nitrogen-rich adamantane-based cage structure, featuring - ONO2 functional groups along with - NH2 groups, exhibits excellent explosive properties and good impact sensitivity. Our computational approach enables the screening and design of novel energetic materials with superior explosive properties, offering insights into structural modifications that optimize energy release, sensitivity, and detonation characteristics.

METHODS

Density functional theory (DFT) using the Gaussian 16 software was used for all quantum chemical calculations. The optimization of the geometry of the designed compounds is performed at two different levels, e.g., B3LYP/6-311 + + G(d,p) and B3PW91/6-31G(d,p). Molecular surface and other properties are visualized using the Gaussview 6.0 software. The heat of formation (HOF) of the molecules is estimated using isodesmic reactions. The Multiwfn program was used for the calculation of molecular surface properties.

The Carbene Chemistry of N-Sulfonyl Hydrazones: The Past, Present, and Future

N-Sulfonyl hydrazones have been extensively used as operationally safe carbene precursors in modern organic synthesis due to their ready availability, facile functionalization, and environmental benignity. Over the past two decades, there has been tremendous progress in the carbene chemistry of N-sulfonyl hydrazones in the presence of transition metal catalysts, under metal-free conditions, or using photocatalysts under photoirradiation conditions. Many carbene transfer reactions of N-sulfonyl hydrazones are unique and cannot be achieved by any alternative methods. The discovery of novel N-sulfonyl hydrazones and the development of highly enantioselective new reactions and skeletal editing reactions represent the notable recent achievements in the carbene chemistry of N-sulfonyl hydrazones. This review describes the overall progress made in the carbene chemistry of N-sulfonyl hydrazones, organized based on reaction types, spotlighting the current state-of-the-art and remaining challenges to be addressed in the future. Special emphasis is devoted to identifying, describing, and comparing the scope and limitations of current methodologies, key mechanistic scenarios, and potential applications in the synthesis of complex molecules.

Facile construction of the all-bridge-position-functionalized 2,4,6,8-tetraazaadamantane skeleton and conversion of its N-functionalities

An unusual protocol of a “one-pot” three-step strategy to build the 2,4,6,8-tetraazaadamantane skeleton was developed. 17 products were obtained in 19–46% yields, and the N-benzyl groups were transferred to nitroso, acetyl, benzoyl and nitro groups.

A new oxygen-rich energetic salt dihydrazine tetranitroethide: a promising explosive alternative with high density and good performance

A novel high-energy salt with good oxygen balance, dihydrazine tetranitroethide (5), has been synthesized and characterized by FT-IR spectroscopy, NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction. Compound 5 exhibits high crystal density (1.81 g cm-3) and impressive detonation velocity (9508 m s-1) and detonation pressure (37.9 GPa), showing potential applications as a high performance explosive and a promising additive of propellants.

Synthesis of cyclic gem-dinitro compounds via radical nitration of 1,6-diynes with Fe(NO3)3·9H2O

Cyclic gem-dinitro compounds were obtained via nitration of 1,6-diynes using Fe(NO₃)₃·9H₂O as the nitrating agent.

2,4,4,6,8,8-Hexanitro-2,6-diazaadamantane: A High-Energy Density Compound with High Stability

A novel high-performance energetic compound of the polynitroazaadamantane family, 2,4,4,6,8,8-hexanitro-2,6-diazaadamantane, was designed and synthesized from 1,5-cyclooctadiene by two routes. Based on the experimental and calculated results, it exhibits a surprisingly high density (1.959 g cm^-3), high thermal stability (onset decomposition temperature of 235 °C), high positive heat of formation, and excellent detonation properties. These fascinating properties, which are comparable to those of CL-20, show great promise for potential applications as a high-energy density material.

A C-C bonded 5,6-fused bicyclic energetic molecule: exploring an advanced energetic compound with improved performance

A C-C bonded amino-nitro pyrazole (7) and its ring-expansion product (9) have been synthesized and characterized. The synthetic route to 9 proceeds in several steps from the commercial substrate diethyl oxalate and acetone. The process was found to be straightforward, practical and easily scalable. Both of these structures were confirmed by single crystal X-ray diffraction. Compound 9 with a high density (1.85 g cm-3) at room temperature, excellent thermal stability (Td: 315 °C), good detonation performance and low sensitivity to impact and friction has potential as a high-temperature energetic material.

Synthesis of two new gem-fluoronitro containing tetranitroadamantanes and property comparison with their nitro and gem-dinitro analogues

Two new fluorinated tetranitroadamantanes, 2,6-difluoro-2,4,4,6-tetranitroadamantane and 2,4,6,8-tetrafluoro-2,4,6,8-tetranitroadamantane, were synthesized. 2,6-Difluoro-2,4,4,6-tetranitroadamantane was prepared from 4,4-dinitroadamantane-2,6-dione by a three-step route with an overall yield of 40%. It has a slightly higher crystal density (1.787 g cm-3) than its analogue 2,2,4,4,6,6-tetranitroadamantane (1.777 g cm-3). 2,4,6,8-Tetrafluoro-2,4,6,8-tetranitroadamantane was prepared from 4,8-dihydroxyadamantane-2,6-dione by an eight-step route with an overall yield of 8%. It is notable that the replacement of one nitro group in the gem-dinitro functionality with fluorine might slightly reduce the detonation performance but improve the density and inherent steric hindrance, which makes it possible to introduce more nitro functionalities on the adamantane backbone.