High-Density Energetic Materials with Low Mechanical Sensitivity and Twinning Derived from Nitroimidazole Fused Ring.

The innovative synthesis of 3,8-dibromo-2,9-dinitro-5,6-dihydrodiimidazo [1,2-a:2',1'-c]pyrazine and 3,9-dibromo-2,10-dinitro-6,7-dihydro-5H-diimidazo [1,2-a:2',1'-c][1,4]diazepine is described in this study. The tricyclic fused molecular structures are formed by the respective amalgamation of piperazine and homopiperazine with the imidazole ring containing nitro. Compound 1 and 2 possess excellent high-density physical properties (ρ1 = 2.49 g/cm3, ρ2 = 2.35 g/cm3) due to the presence of a fused ring structure and Br atom. In addition to their high density, they have high decomposition temperatures (Td > 290 °C) which means that they have excellent thermal stability and can be used as potential heat-resistant explosives. Low mechanical sensitivities (IS > 40 J, FS > 360 N) are observed. The twinning structure of 2 was resolved by X-ray diffraction. Non-covalent interaction analysis, Hirshfeld surfaces, 2D fingerprint plot, and Electrostatic potential analysis were used to understand the intramolecular interactions in relation to physicochemical properties. The unique structures of this type of compound provide new potential for the evolution of energetic materials.

Combination of Energetic Tetrazole and Triazole: Promising Materials with Exceptional Stability and Low Mechanical Sensitivity as Propellants and Gas Generators.

An innovative synthesis of 5-((1H-tetrazol-5-yl)methyl)-4H-1,2,4-triazole-3,4-diamine (TMT) based on triazole and tetrazole frameworks bearing double amino groups was reported. It is worth mentioning that TMT is insensitive to impact and friction (IS > 40 J, FS > 360 N), thus enabling it to have an exceptional thermal decomposition behavior that is superior to RDX and TNT. Meanwhile, it also has relatively high energetic performance (Dv = 8.417 km/s). A series of energy-containing salts TMT-1-8 were also investigated for their potential applications. Except for TMT-4 and TMT-7, the remaining nitrogen-rich salts have initial decomposition temperatures above 200 °C. Furthermore, the salts with positive heat generation all have extraordinary gas production, especially for TMT-1 (Vo = 840.5 dm3/kg), TMT-2 (Vo = 803.9 dm3/kg), and TMT-7 (Vo = 844.3 dm3/kg). The low mechanical sensitivities of the TMT series were discovered, and a majority of them have impact sensitivities exceeding 40 J with friction sensitivities exceeding 360 N which are superior to TNT (IS = 15 J, FS = 353 N). The intermolecular and intramolecular interactions of the crystals TMT-1-3 were explored by Hirshfeld surfaces, 2D fingerprint plots, noncovalent interaction (NCI) analysis, and electrostatic potential surface analysis to understand the physicochemical property changes in relation to the structure. Consequently, this novel tri/tetrazole and polyamine system as a promising material provides the impetus for the development of gas generators and propellants.

The strategy for improving the stability of nitroform derivatives-high-energetic oxidant based on hexanitroethane.

To develop high-energetic stability nitroform compounds, three types of nitroform derivatives based on hexanitroethane structure are designed. The guidelines for selecting these compounds are based on (1) constructing a flexible molecule and weakening the external force by elastic deformation and (2) forming negative ion or introducing electron-rich group to eliminate the electron-deficient situation. The conformations and some important properties of them are calculated at B3LYP/6-311 + G(d) level. Based on the bond order and bond dissociation enthalpy analysis, C-NO2 bond is considered to be the most unstable position, and both of the methods can improve the stability of designed compounds. Based on molecular energy gap (HOMO-LUMO) and density of state (DOS) analysis, it is found that introducing of bridge atoms is helpful to lower the sensitivity, while the construction of anions changes both HOMO-LUMO and DOS which shows obvious ionic properties. A further study on the electrical potential surface shows that the probability for extreme values of designed compounds decreases which is beneficial for high stability. Finally, the explosive properties and impact sensitivity of them are calculated. Results show that their explosive performances are obviously better than current energetic oxidants and some of them maintain low sensitivity.

Palladium-catalyzed annulation of alkynes with ortho-halide-containing benzyl alcohols in aqueous medium.

The Pd-catalyzed annulations of ortho-halide-containing benzyl alcohols with alkynes for the synthesis of indenones were achieved in aqueous Triton X-100 micelles with good yields and wide substrate scopes. Moreover, the indenones obtained in this procedure can be further functionalized to form some more synthetic useful derivatives via an environmental-friendly way.

One-pot synthesis of 2-amino-4(3H)-quinazolinones via ring-opening of isatoic anhydride and palladium-catalyzed oxidative isocyanide-insertion.

An efficient and practical two-step process has been developed for the synthesis of 2-amino-4(3H)-quinazolinones via ring-opening of isatoic anhydride and palladium-catalyzed oxidative isocyanide-insertion in one pot. This regioselective procedure could construct a wide range of 2-amino-4(3H)-quinazolinones in moderate to excellent yields. Furthermore, the methodology also had distinct advantages of easily accessible starting materials and operational simplicity.

Synthesis of highly functionalized macrocycles by tandem multicomponent reactions and intramolecular Sonogashira cross-coupling.

An efficient chemoselective process for the synthesis of 14- and 15-membered triazole-containing macrocycle compounds has been developed through the combination of two multicomponent reactions and an intramolecular Sonogashira cross-coupling reaction.

Synthesis of novel isoquinolinone and 1,2-dihydroisoquinoline scaffolds via Ugi reaction and ring opening reaction of furans.

Combining the Ugi reaction with ring opening reaction of furans for the synthesis of novel isoquinolinone and 1,2-dihydroisoquinoline scaffolds has been developed. The isoquinolinone and 1,2-dihydroisoquinoline derivatives with unsaturated carbonyl moiety may open up many opportunities for further functionalizations.

Chemoselective preparation of 1,2,3-triazole-isoxazole bisfunctional derivatives and their application in peptidomimetic synthesis.

A novel kind of bisfunctional nitrogen heterocycle containing both 1,2,3-triazole and isoxazole scaffolds has been prepared. The protocol utilized alkynyl substituted amines as the bifunctional linkers to combine a copper-free triazole synthesis with a hypervalent iodine-mediated isoxazole cycloaddition through a chemoselective process. This method has also been exemplified in the construction of bisfunctional-modified peptidomimetics by combining three reactions in a sequential procedure. This straightforward metal free process may find biological applications. In addition, all of the compounds were analysed by Lapinski's rule-of-five which is expected to help drug discovery.

A simple procedure for polymer-supported N-heterocyclic carbene silver complex via click chemistry: an efficient and recyclable catalyst for the one-pot synthesis of propargylamines.

A series of polymer-supported N-heterocyclic carbene silver complexes were prepared using a simple procedure via click chemistry. These complexes were tested as catalysts in the synthesis of propargylamines by the one-pot three-component coupling reaction of aldehydes, amines and alkynes (A(3)-coupling). The reaction was preceded smoothly to afford the corresponding products in good to excellent yields at room temperature under low catalyst loading of 0.1 mol%. Furthermore, the catalysts were stable and recoverable for six runs without a significant loss in their activity.