Nitroamino-functionalized 1,2,4-triazolo­[4,3-b]­[1,2,4,5]­tetrazine (1), when combined with intermolecular hydrogen bonds (HBs) and strong noncovalent interactions between layers, results, for example, in an interlayer distance of 2.9 Å for dihydroxylammonium 3,6-dinitramino-1,2,4-triazolo­[4,3-b]­[1,2,4,5]­tetrazine (2c) with a packing coefficient of 0.805. For dihydroxylammonium 6,6′-dinitramino-3,3′-azo-1,2,4-triazolo­[4,3-b]­[1,2,4,5]­tetrazine (3b), two fused rings are linked by an azo group, which expands the conjugated system resulting in an even shorter interlayer distance of 2.7 Å and a higher packing coefficient of 0.807. These values appear to be the shortest interlayer distances and the highest packing coefficients reported for tetrazine energetic materials. With high packing coefficients, both possess high densities of 1.92 g cm–3 and 1.99 g cm–3 at 293 K, respectively. Compared with its precursor, the hydroxylammonium moiety serves as a buffer chain (H–N–O–H), connecting the anion and cation through hydrogen bonds, giving rise to more favorable stacking, and resulting in higher density and lower sensitivity. The sensitivities of all the hydroxylammonium salts are lower than that of their neutral precursors, such as compound 2 (3 J, >5 N) and compound 2c (25 J, 360 N). The detonation properties of 2c (detonation velocity vD = 9712 m s–1 and detonation pressure P = 43 GPa) and 3b (vD = 10233 m s–1; P = 49 GPa) exceed those of present high explosive benchmarks, such as octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexanitrohexaazaisowurzitane (CL-20). The molecular structures of several of these new energetic materials are confirmed by single-crystal X-ray diffraction measurements. Using calculated and experimental results, the fused ring with a planar large π-conjugated system results in a compromise between desirable stabilities and high detonation properties, thus enhancing future utilization in the design of energetic materials.

The direct aldol reactions catalyzed by chiral dendritic catalysts derived from N-prolylsulfonamide gave the corresponding products in high isolated yields (up to 99%) with excellent anti diastereoselectivities (up to >99:1) and enantioselectivities (up to >99% ee) in water. In addition, catalyst 1e may be recovered by precipitation and filtration and reused for at least five times without loss of catalytic activity.

Intramolecular hydroamination of alkynyl amides was effected by a catalytic amount of Et2Zn (20 mol %) to form indole derivatives, and a tandem cyclization/nucleophilic addition procedure involving reaction of the indole zinc salt intermediate with acid chlorides or halides was developed to provide an efficient approach to C3-substituted indole derivatives when an excess of Et2Zn (120 mol %) was used.

Abstract:The asymmetric construction of quaternary carbon centers via cross-aldol reactions of ketones with b,g-unsaturated keto esters catalyzed by 4-(tert-butyldiphenylsilyloxy)-pyrrolidine-2-carboxylic acid in water is described. The adducts bearing two adjacent chiral centers were obtained in high yields, mostly up to 99% ee, and with high diastereoselectivities. The corresponding polyfunctional products could also be easily transformed to useful lactones with three chiral centers.

We report here an isotopic labeling and mass spectrometric method to rapidly identify S-adenosylmethionine (AdoMet)-dependent methylation products. In the presence of CH(3)- and CD(3)-labeled AdoMet, a methyl transfer product appears as a doublet separated by 3 Da in a mass spectrum, while other compounds show their normal isotopic distribution. Based on this unique isotopic pattern, methylation product(s) can be easily detected even from a mixture of cellular components. To validate our method, the product of human thiopurine methyltransferase (TPMT, EC 2.1.1.67) has been successfully identified from both an in vitro assay and a whole-cell assay. This method is generally applicable to AdoMet-dependent transmethylation and other group-transfer reactions, and constitutes the first example of a general strategy of enzyme-transferred isotope patterns (ETIPs) analysis.

Ammonium perchlorate (AP) is most often used as a practical solid rocket propellant because of its excellent performance. However, AP has many shortcomings, including instability, high negative enthalpy of formation, and claimed health and environmental issues resulting from its combustion products. The pursuit of highly dense, high-performance, and environmentally friendly oxidizers as solid propellants has long attracted scientists around the world. In this work, bis­(3-nitro-1-(trinitromethyl)-1H-1,2,4-triazol-5-yl)­methanone (3) was obtained from bis­(3-nitro-1H-1,2,4-triazol-5-yl)­methane (1) with chloroacetone followed by nitration. The structure of 3 was confirmed by elemental analysis and single-crystal X-ray diffraction. By introducing the carbonyl moiety, the density of 3 was increased to 1.945 g/cm3 and the decomposition temperature increased to 164 °C. Compound 3 is a green energetic oxidizer that has a positive oxygen balance (+8.7%), a high specific impulse (218 s), and an acceptable sensitivity (9 J, 240 N), making it a practical replacement for AP in solid rocket propellant formulations.

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Next-generation fused ring energetic materials for different applications were designed by regulating mechanical sensitivity.