Suzuki–Miyaura coupling reactions of aryl chlorides catalyzed by a new nickel(II) σ‐aryl complex

A new nickel(II) σ‐aryl complex, trans‐chloro(9‐phenanthrenyl)bis(triphenylphosphine)nickel(II), was used as a precatalyst for the Suzuki–Miyaura coupling reactions of aryl chlorides. The catalytic conditions were optimized by investigating the cross‐coupling of p‐chloroanisole with phenylboronic acid. The results show that this complex is efficient for both electron‐rich and electron‐deficient aryl chlorides, though it gives better yields for activated arylboronic acids than deactivated ones. All isolated cross‐coupled biaryl products have been characterized by ¹H and ¹³C NMR, and their spectral data are consistent with those reported. Side products from the coupling of arylboronic acid with the precatalyst complex have also been isolated and characterized, which is helpful for understanding the coupling mechanism. Copyright © 2013 John Wiley & Sons, Ltd.     

Design and Synthesis of Nitrogen-Rich Azo-Bridged Furoxanylazoles as High-Performance Energetic Materials

A series of novel energetic materials comprising of azo-bridged furoxanylazoles enriched with energetic functionalities was designed and synthesized. These high-energy materials were thoroughly characterized by IR and multinuclear NMR (¹H, ¹³C, ¹⁴N) spectroscopy, high-resolution mass spectrometry, elemental analysis, and differential scanning calorimetry (DSC). The molecular structures of representative amino and azo oxadiazole assemblies were additionally confirmed by single-crystal X-ray diffraction and X-ray powder diffraction. A comparison of contributions of explosophoric moieties into the density of energetic materials revealed that furoxan and 1,2,4-oxadiazole rings are the densest motifs while the substitution of the azide and amino fragments on the nitro and azo ones leads to an increase of the density. Azo bridged energetic materials have high nitrogen-oxygen contents (68.8–76.9 %) and high thermal stability. The synthesized compounds exhibit good experimental densities (1.62–1.88 g cm⁻³), very high enthalpies of formation (846–1720 kJ mol⁻¹), and, as a result, excellent detonation performance (detonation velocities 7.66–9.09 km s⁻¹ and detonation pressures 25.0–37.7 GPa). From the application perspective, the detonation parameters of azo oxadiazole assemblies exceed those of the benchmark explosive RDX, while a combination of high detonation performance and acceptable friction sensitivity of azo(1,2,4-triazolylfuroxan) make it a promising potential alternative to PETN.     

Biodegradable aromatic copolyesters made from bicyclic acetalized galactaric acid

Random poly(hexamethylene terephthalate‐co‐galactarate)s and poly(dodecamethylene terephthalate‐co‐galactarate)s copolyesters covering the whole range of compositions were obtained with weight‐average molecular weights of ～30,000–50,000 g mol^?1 by melt polycondensation. They were thermally stable above 300 °C, and displayed T_g in the +20 to ?20 °C range with values steadily decreasing with the content in galactarate units. All the copolyesters were semicrystalline with T_m between 50 and 150 °C and those made from dodecanediol were able to crystallize from the melt at a crystallization rate depending on composition. Copolyesters containing up to 50% of galactaric units retained the crystal structure of their respective polyterephthalate homopolyesters, whereas they adopted the structure of the respective polygalactarates when the content in Galx units reached 70%. Stress‐strain essays revealed decay in the mechanical parameters as the aromatic units were replaced by Galx. Incubation in aqueous buffer revealed that hydrolysis of the polyesters were largely enhanced by copolymerization and evidenced the capacity of the Galx unit for making aromatic polyesters susceptible to biodegradation. A detailed NMR analysis complemented by SEM observations indicated that hydrolysis took place by preferred splitting of galactarate ester bonds with releasing of alkanediol and Galx‐diacid. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Assembly of Tetrazolylfuroxan Organic Salts: Multipurpose Green Energetic Materials with High Enthalpies of Formation and Excellent Detonation Performance

A series of highly energetic organic salts comprising a tetrazolylfuroxan anion, explosophoric azido or azo functionalities, and nitrogen-rich cations were synthesized by simple, efficient, and scalable chemical routes. These energetic materials were fully characterized by IR and multinuclear NMR (¹H, ¹³C, ¹⁴N, ¹⁵N) spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). Additionally, the structure of an energetic salt consisting of an azidotetrazolylfuroxan anion and a 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 good experimental densities (1.57–1.71 g cm⁻³), very high enthalpies of formation (818–1363 kJ mol⁻¹), and, as a result, excellent detonation performance (detonation velocities 7.54–8.26 kms⁻¹ and detonation pressures 23.4–29.3 GPa). Most of the synthesized energetic salts have moderate sensitivity toward impact and friction, which makes them promising candidates for a variety of energetic applications. At the same time, three compounds have impact sensitivity on the primary explosives level (1.5–2.7 J). These results along with high detonation parameters and high nitrogen contents (66.0–70.2 %) indicate that these three compounds may serve as potential environmentally friendly alternatives to lead-based primary explosives.     

The behavior of thermoresponsive star-shaped poly-2-isopropyl-2-oxazoline in saline media

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Calorimetric study of poly(2-ethylhexyl acrylate) over the range from T → 0 to 350 K

For the first time, the heat capacity $ C_{\text{p}}^{^\circ } $ of poly(2-ethylhexyl acrylate) has been studied in an adiabatic vacuum calorimeter between 7 and 350 K, the standard thermodynamic functions: heat capacity $ C_{\text{p}}^{^\circ } $ (T), enthalpy H°(T) ? H°(0), entropy S°(T) ? S°(0), Gibbs function G°(T) ? H°(0) have been calculated from T → 0 to 350 K. The energy of combustion Δ_c U of the compound under study has been measured in a calorimeter with a stationary bomb and an isothermal shell. The standard enthalpy of combustion Δ_c H° and thermodynamic parameters of formation—enthalpy Δ_f H°, entropy Δ_f S°, Gibbs function Δ_f G°—at T = 298.15 K have been calculated. The results have been used to calculate the thermodynamic characteristics of 2-ethylhexyl acrylate bulk polymerization into poly(2-ethylhexyl acrylate) over the range from T → 0 to 350 K.     

A sensitive chromatographic determination of hydrazines by naphthalene-2,3-dialdehyde derivatization

A new high-performance liquid chromatography (HPLC) method for the sensitive simultaneous determination of hydrazine (Hy), monomethylhydrazine (MMH) and 1,1-dimethylhydrazine (UDMH) based upon the derivatization of hydrazines with naphthalene-2,3-dialdehyde and the separation of the derivatives on Zorbax Eclipse AAA column in a single chromatographic run under acidic conditions (pH 2.4) was developed. Hydrazine and monomethylhydrazine derivatives were found to be strongly fluorescent at λ_ex?=?273?nm, λ_em?=?500?nm. It was shown that UDMH derivative can be detected as non-fluorescent hydrazone at 290?nm by UV-detection. Limits of detection were 0.05?µg?·?L^?1 for Hy and MMH, and 1?µg?·?L^?1 for UDMH for the injection volume of 100?µL. The method was validated for water sample analysis. It proved to be selective, accurate and precise with the supplementary advantage of the simple and rapid sample preparation.     

Development and validation of a LC-MS/MS method for d-cycloserine determination in human plasma for bioequivalence study

A reliable and high throughput high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated for determining levels of the antitubercular drug-d -cycloserine in human plasma. Plasma samples analyte with an internal standard (IS) (niacin) were prepared by solid-phase extraction using Waters Oasis MCX cartridges. The chromatographic separation was performed using the HILIC mode on a YMC-Pack SIL-06 column (150?×?4.6 mm; 3 μm) under isocratic conditions. The run time of analysis was 5 min. The mobile phase consisted of methanol, propanol-2 and 0.075 % trifluoroacetic acid (66.5:28.5:5, v/v/v). Protonated ions formed by turbo ion spray in positive mode were used to detect the analyte and the IS. MS/MS detection was used to monitor the fragmentation of 103–75?m/z for cycloserine and 124 to 80?m/z for niacin (IS) on an API 4000 (AB Sciex) triple quadrupole mass spectrometer. A linear dynamic range of 0.3–30 μg/mL was established for cycloserine using 0.2 mL human plasma and a 1 μL injection volume. The mean relative recovery of cycloserine and niacin were 77.2 and 82.4 %, respectively. The procedure of sample preparation was consistent and reproducible (precision, 0.8–3.4 %; accuracy, 93.8–104.9 %). The method was validated in accordance with requirements of the European Medicines Agency and successfully applied to a bioequivalence study of 250 mg tablet formulations in 23 healthy human subjects.