Synthesis and Properties of Thermostable Energetic Benzotriazines.

In an effort to balance energy and molecular stability effectively, several energetic compounds (-) based on benzotriazine were designed and synthesized. These structures were comprehensively characterized using NMR, IR, and elemental analysis, with compounds , , and further confirmed by single-crystal X-ray diffraction. Notably, 3-amino-5,7-dinitrobenzo[][1,2,4]triazine 1-oxide (), which features a face-to-face crystal stacking arrangement, exhibits good detonation velocity ( = 8050 m/s), a high thermal decomposition temperature ( = 290 °C), and low sensitivities (impact sensitivity >40 J, friction sensitivity >360 N).

Iodine as Polarity-Reversal Catalyst: Synthesis of a Fused Heterocycle with Contiguous Stereocenters.

We report an unconventional I-catalyzed cascade reaction for the synthesis of angular triquinane derivatives with a fused heterocycle skeleton, leveraging enaminones and anilines as simple acyclic precursors. The key to success lies in I functioning as a polar-reversal catalyst, which alters the reactivity at the α-position of the enaminone and facilitates the first hexa-functionalization of an enaminone along with the formation of highly congested continuous stereocenters.

Bifunctional Nitrogen-Rich Heterocyclic Compounds: Synthesis, Photoluminescence and Energetic Properties.

Nitrogen-rich heterocyclic frameworks have attracted enormous interest in organic chemistry and materials science. However, their potential for developing photoluminescent materials remains underexplored due to their relatively low molecular stabilities. In this work, two tricyclic fused nitrogen-rich fluorescent heterocycles were synthesized and characterized.

-Benzylhydroxylamine as a novel synthetic block in "C1N1" embedding reaction α-C(sp)-H activation strategy.

A novel process using -benzylhydroxylamine hydrochloride as a "C1N1 synthon" in [2+2+1] cyclization for the construction of 1,2,5-trisubstituted imidazoles has been described for the first time. The key to realizing this process lies in capturing arylamines by generated novel acyl ketonitrone intermediates. Subsequent tautomerization activates the α-C(sp)-H of -benzylhydroxylamines, and thus breaks through its inherent reaction mode and achieves , α-C site-selective cyclization.

Diazotization of -Aminoamidoximes for the Preparation of Energetic 6,5,6-Fused 1,2,3-Triazine-3-oxides.

Two 6,5,6-fused 1,2,3-triazine-3-oxides ( and ) were designed and synthesized via the reaction of -aminoamidoximes with sodium nitrite. In addition, the ring-opening products (, , and ) derived from 1,2,3-triazine-3-oxides were isolated and characterized. A comprehensive exploration of the reaction mechanism governing the ring-opening process was performed through a combination of theoretical and experimental studies.

I-DMSO-Mediated Construction of 2,3- and 2,4-Disubstituted Pyrimido[1,2-]indazole Skeletons.

An efficient synthetic method for constructing 2,3- and 2,4-disubstituted pyrimidio[1,2-]indazole skeletons through I-DMSO-mediated and substrate-controlled regioselective [4 + 2] cyclization is reported. The reaction conditions are mild, its operation is simple, and the substrate scope is wide. More than 60 pyrimidio[1,2-]indazole derivatives have been synthesized, providing a new methodology for constructing related molecules and potentially enriching bioactive-molecule libraries.

Pushing the limits of the heat of detonation the construction of polynitro bipyrazole.

The trinitromethyl group is a highly oxidized group that is found as an active functionality in many high-energy-density materials. The most frequently used previous synthetic method for the introduction of the trinitromethyl group is the nitration of heterocyclic compounds containing an acetonyl/ethyl acetate/chloroxime group. Now a novel strategy for constructing a trinitromethyl group (5) nitration of an ethylene bridged compound, dipyrazolo[1,5-:5',1'-]pyrazine (2), is reported.

From Tetranitromethane to -Dinitro-Bridged Nitrogen-Rich Heterocyclic Compound: Achieving High Heat of Detonation.

Improving the detonation performance of tetranitromethane (TNM) by introducing energetic moieties is an intriguing area in the field of energetic materials. Incorporation of a mono nitrogen-rich skeleton into TNM usually results in unsatisfactory detonation performance. Now, we reported the design and synthesis of an advanced TNM-like molecule () containing nitrogen-rich triazole and nitro-triazinane moieties.

I-DMSO-Mediated Transannulation of Benzo[]isoxazol-3-amine: Direct Access to 2,4,5-Substituted Pyrimidine Derivatives.

An I-DMSO-mediated multicomponent [3+1+2] cascade annulation reaction using aryl methyl ketones, enaminones, and benzo[]isoxazol-3-amine as substrates has been developed. This metal-free reaction involved the transannulation of benzo[]isoxazol-3-amines with the formation of two C-N bonds and a C-C bond in one pot. Notably, a pyrimidine ring with a 1,4-dicarbonyl scaffold could efficiently transform into a pyrimido[4,5-]pyridazine skeleton.

Triazole-induced planarization of a twisted tetrazole-based molecule towards energetic materials with improved thermostability and insensitivity.

Pursuing the structural planarization of energetic materials is an efficient method for achieving improved performance. Although many planar energetic molecules have been prepared so far, the innovation of advanced planar explosives still relies on the scientific intuition, experience and trial-and-error of researchers. Now, a triazole-induced planarization strategy is proposed based on the regulation of aromaticity, charge distribution, and hydrogen bonds.

The design and synthesis of new advanced energetic materials based on pyrazole-triazole backbones.

A series of derivatives of the nitropyrazole-triazole backbone were designed through units' screening of 219 N-heterocycle compounds and were synthesized. Among them, the thermal stability of DNPAT ( = 314 °C) is close to that of traditional heat-resistant explosive HNS (318 °C) while the detonation performance and sensitivity ( = 8889 m s; IS = 18 J) are better than those of HNS ( = 7612 m s; IS = 5 J) and traditional high-energy explosive RDX ( = 8795 m s; IS = 7.4 J), which is rarely reported in heat-resistant explosives.

Site-Selective Oxidative Coupling Reaction of Diamines toward Aminoazo Compounds.

A selective oxidative coupling reaction of a diamine containing both - and -NH was achieved using acidic potassium permanganate as the coupling reagent. The reaction conditions were optimized, and the reaction selectivity was illustrated by quantum calculations. Furthermore, the azo-coupled product was derivatized to four nitroamine energetic materials with excellent detonation performances.

N, S Co-Coordinated Zinc Single-Atom Catalysts for N-Alkylation of Aromatic Amines with Alcohols: The Role of S-Doping in the Reaction.

S-doping emerged as a promising approach to further improve the catalytic performance of carbon-based materials for organic synthesis. Herein, a facile and gram-scale strategy was developed using zeolitic imidazole frameworks (ZIFs) as a precursor for the fabrication of the ZIF-derived N, S co-doped carbon-supported zinc single-atom catalyst (CNS@Zn-AA) via the pyrolysis of S-doped ZIF-8, which was modified by aniline, ammonia and thiourea and prepared by one-pot ball milling at room temperature. This catalyst, in which Zn is dispersed as the single atom, displays superior activity in N-alkylation via the hydrogen-borrowing strategy (120 °C, turnover frequency (TOF) up to 8.

Dehydrogenative Syntheses of Biazoles via a "Pre-Join" Approach.

The structural motif of biazoles is the predominant substructure of many natural products, pharmaceuticals, and organic materials. Considerable efforts have focused on synthesizing these compounds; however, a limited number of processes have been reported for the efficient formation of biazoles. Herein, we report a "pre-join" approach for the dehydrogenative synthesis of biazoles, which are challenging to prepare using conventional methods.

I-DMSO Mediated Multicomponent [3+2] Annulation Reaction: An Approach to Pyrrolo[2,1-]isoquinoline Derivatives with a Quaternary Center.

An I-DMSO mediated multicomponent [3+2] cascade annulation reaction using methyl ketones, 1,2,3,4-tetrahydroisoquinolines (THIQ) and cyclopropenones as readily available substrates has been developed. This metal-free process involves N-H/α-C(sp)-H trifunctionalization of THIQ and C-C bond cleavage of cyclopropenone, providing a direct approach to obtain pyrrolo[2,1-]isoquinoline derivatives with a quaternary carbon center. Two C-C bonds and one C-N bond are formed efficiently in one pot.

Effects of nitric acid concentration for nitration of fused [1,2,5]oxadiazolo[3,4-]pyrimidine-5,7-diamine.

Nitration reactions are very often used for the selective synthesis of novel, high performing nitramine-based materials. Now nitration reactions of the fused 5,7-diamino pyrimidine derivative 1, under different nitric acid concentrations were examined. Concentrated nitric acid gave selectively -(5-amino-4,5-dihydro-[1,2,5]oxadiazolo[3,4-]pyrimidin-7-yl)nitramide, 2, while the fused ring nitrate salt, 4, and ring open nitrate salt, 3 were obtained using low concentrations of nitric acid (<70%).

Toward Advanced High-Performance Insensitive FOX-7-like Energetic Materials via Positional Isomerization.

For an energetic molecule with a definite elemental composition, the substituent type and position are the most important factors to influence its detonation performance and mechanical sensitivities. In this work, two pairs of FOX-7-like energetic isomers based on ( and ; and ) were synthesized and characterized. Through positional isomerization, advanced high-performance insensitive explosives were obtained.

An advanced primary explosive and secondary explosive based on a zwitterionic pyrazole-triazole derivative.

Two zwitterionic energetic materials containing a pyrazole-triazole backbone were synthesized and fully characterized. Compound 3 can serve as an ideal secondary explosive due to its high decomposition temperature (>200 °C), low impact sensitivity (>40 J), and excellent calculated detonation velocity (9090 m s). The good priming ability of compound 4 demonstrates that it is a potential candidate as a primary explosive, which was confirmed in the test.

I-DMSO-Mediated N-H/α-C(sp)-H Difunctionalization of Tetrahydroisoquinoline: Formal [2 + 2 + 1] Annulation for the Construction of Pyrrolo[2,1-]isoquinoline Derivatives.

An I-DMSO-mediated cascade reaction using methyl ketones and 1,2,3,4-tetrahydroisoquinolines (THIQs) as commercially available substrates has been developed for the construction of pyrrolo[2,1-]isoquinoline derivatives. This metal-free process involves N-H/α-C(sp)-H difunctionalization of THIQ. Two C-C bonds and one C-N bond are formed in one pot under mild conditions.

From Nitro- to Heterocycle-Functionalized 1,2,4-Triazol-3-one Derivatives: Achieving High-Performance Insensitive Energetic Compounds.

5-Nitro-1,2,4-triazol-3-one, a nitro-functionalized 1,2,4-triazol-3-one (TO) derivative, shows excellent energetic properties and promising application potential. However, the use of the TO skeleton as an energetic material is still largely underexplored both theoretically and practically. We report here a mild and efficient method for obtaining the TO skeleton via a reaction of aminocarbohydrazide with BrCN.

Copper-Catalyzed Oxidative C(sp)-H/C(sp)-H Cross-Coupling Reaction of 3-Methylbenzo[]isoxazoles with Methyl Ketones: Access to Indigoid Analogues.

A copper-catalyzed oxidative C(sp)-H/C(sp)-H cross-coupling reaction of methyl ketones and 3-methylbenzo[]isoxazoles has been developed for the direct synthesis of 3-oxoindolin-2-ylidene derivatives. This process involves an intermolecular nucleophilic addition/ring-opening/aza-Michael addition cascade, providing indigoid analogues with high atom economy and as single isomers exclusively under mild conditions.

Energetic Tricyclic Polynitropyrazole and Its Salts: Proton-Locking Effect of Guanidium Cations.

An axisymmetric polynitro-pyrazole molecule, 3,5-di(3,5-dinitropyrazol-4-yl)]-4-nitro-1-pyrazole (), and its salts (-) were prepared and fully characterized. These compounds not only show promising energetic properties but also show a unique tautomeric switch via combining different cations with the axisymmetric compound (). Its salts (-) remain axisymmetric when the cations are potassium, ammonium, or amino-1,2,4-triazolium.

I-DMSO mediated oxidative amidation of methyl ketones with anthranils for the synthesis of α-ketoamides.

An I-DMSO mediated oxidative amidation of methyl ketones using anthranils as masked N-nucleophiles has been developed for the direct synthesis of α-ketoamides with high atom-economy. This metal-free process involves reductive N-O bond cleavage of anthranils and oxidative C-N bond formation of methyl ketones under mild conditions. The iodo group and electrophilic formyl group provide multiple possibilities for further functionalization of α-ketoamides.

Mono-N-oxidation of heterocycle-fused pyrimidines.

Three nitrogen-rich heterocyclic compounds containing the diamino-pyrimidine mono-N-oxide moiety were synthesized via mild oxidation reactions. Oxidation of the furazano-pyrimidine compound (1) with a mixture of trifluoroacetic anhydride (TFAA) and hydrogen peroxide (50%) gave the nitrate salt (3). All of the compounds were characterized by NMR spectra, elemental analysis, and single-crystal X-ray diffraction.