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71.
Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation 下载免费PDF全文
Dr. Taiga Yurino Yohei Ueda Dr. Yoshiki Shimizu Dr. Shinji Tanaka Haruka Nishiyama Prof. Dr. Hayato Tsurugi Prof. Dr. Kazuhiko Sato Prof. Dr. Kazushi Mashima 《Angewandte Chemie (International ed. in English)》2015,54(48):14437-14441
A salt‐free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6‐tetramethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene ( 1 ), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)2 (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C? C bond‐forming reactions of aryl halides in the presence of excess amounts of 1 . By examination of high‐magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity. 相似文献
72.
Dr. Aleksandrs Prokofjevs 《Angewandte Chemie (International ed. in English)》2015,54(45):13401-13405
Thermally induced dehydrogenation of the H‐bridged cation L2B2H5+ (L=Lewis base) is proposed to be the key step in the intramolecular C? H borylation of tertiary amine boranes activated with catalytic amounts of strong “hydridophiles”. Loss of H2 from L2B2H5+ generates the highly reactive cation L2B2H3+, which in its sp2‐sp3 diborane(4) form then undergoes either an intramolecular C? H insertion with B? B bond cleavage, or captures BH3 to produce L2B3H6+. The effect of the counterion stability on the outcome of the reaction is illustrated by formation of LBH2C6F5 complexes through disproportionation of L2B2H5+ HB(C6F5)3?. 相似文献
73.
Pilar G. Rodríguez Ortega Prof. Manuel Montejo Prof. Fernando Márquez Prof. Juan J. López González 《Chemphyschem》2015,16(7):1416-1427
The implementation of a strategy comprising the use of vibrational circular dichroism spectroscopy and DFT calculations allows determination of the solution‐state conformational distribution in (?)‐S‐cotinine, giving further proof of the extra conformer‐discriminating potential of this experimental technique, which may offer unique molecular fingerprints of subtly dissimilar molecular conformers of chiral samples. Natural bond orbital electronic structure calculations of the rotational barrier height between the two main conformers of the species indicate that hyperconjugative effects are the key force governing the conformational equilibrium. The negligible effect of the solvent’s polarity over both structure and conformational energy profile supports this result. 相似文献
74.
Chemical investigation of the ethanol extract of the roots of Cudrania cochinchinensis led to the isolation of a new flavonoid, (6S,12S,13R)-1-methoxy cyanomaclurin (1), together with seven known compounds, 1,3,5-trihydroxy-4-(3′-hydroxy-3′-methylbutyl)xanthone (2), 1,3,6-trihydroxy-4-prenylxanthone (3), 1,3,6,7-tetrahydroxyxanthone (4), 1,3,5,6-tetrahydroxyxanthone (5), 1,3,6-trihydroxy-5-methoxyxanthone (6), resveratrol (7) and oxyresveratrol (8). The structure of compound 1 was elucidated on the basis of 1D and 2D NMR spectra and the HR-ESI-MS data. The absolute stereochemistry was deduced via Rh2(OCOCF3)4-induced CD and NOESY spectra. 相似文献
75.
Method development for the determination of 24S‐hydroxycholesterol in human plasma without derivatization by high‐performance liquid chromatography with tandem mass spectrometry in atmospheric pressure chemical ionization mode 下载免费PDF全文
Hiroshi Sugimoto Masaaki Kakehi Yoshinori Satomi Hidenori Kamiguchi Fumihiro Jinno 《Journal of separation science》2015,38(20):3516-3524
We developed a highly sensitive and specific high‐performance liquid chromatography with tandem mass spectrometry method with an atmospheric pressure chemical ionization interface to determine 24S‐hydroxycholesterol, a major metabolite of cholesterol formed by cytochrome P450 family 46A1, in human plasma without any derivatization step. Phosphate buffered saline including 1% Tween 80 was used as the surrogate matrix for preparation of calibration curves and quality control samples. The saponification process to convert esterified 24S‐hydroxycholesterol to free sterols was optimized, followed by liquid–liquid extraction using hexane. Chromatographic separation of 24S‐hydroxycholesterol from other isobaric endogenous oxysterols was successfully achieved with gradient mobile phase comprised of 0.1% propionic acid and acetonitrile using L‐column2 ODS (2 μm, 2.1 mm id × 150 mm). This assay was capable of determining 24S‐hydroxycholesterol in human plasma (200 μL) ranging from 1 to 100 ng/mL with acceptable intra‐ and inter‐day precision and accuracy. The potential risk of in vitro formation of 24S‐hydroxycholesterol by oxidation from endogenous cholesterol in human plasma was found to be negligible. The stability of 24S‐hydroxycholesterol in relevant solvents and human plasma was confirmed. This method was successfully applied to quantify the plasma concentrations of 24S‐hydroxycholesterol in male and female volunteers. 相似文献
76.
Nitrite Oxidation with Copper–Cobalt Nanoparticles on Carbon Nanotubes Doped Conducting Polymer PEDOT Composite
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Copper–cobalt bimetal nanoparticles (Cu?Co) have been electrochemically prepared on glassy carbon electrodes (GCEs), which were electrodeposited with conducting polymer nanocomposites of poly(3,4‐ethylenedioxythiophene) (PEDOT) doped with carbon nanotubes (CNTs). Owing to their good conductivity, high mechanical strength, and large surface area, the PEDOT/CNTs composites offered excellent substrates for the electrochemical deposition of Cu?Co nanoparticles. As a result of their nanostructure and the synergic effect between Cu and Co, the Cu?Co/PEDOT/CNTs composites exhibited significantly enhanced catalytic activity towards the electrochemical oxidation of nitrite. Under optimized conditions, the nanocomposite‐modified electrodes had a fast response time within 2 s and a linear range from 0.5 to 430 μm for the detection of nitrite, with a detection limit of 60 nm . Moreover, the Cu?Co/PEDOT/CNTs composites were highly stable, and the prepared nitrite sensors could retain more than 96 % of their initial response after 30 days. 相似文献
77.
Jonathan H. Brown Lisa Orloff Clark Astrid an Huef 《Journal of Pure and Applied Algebra》2017,221(10):2458-2481
The graph groupoids of directed graphs E and F are topologically isomorphic if and only if there is a diagonal-preserving ring ?-isomorphism between the Leavitt path algebras of E and F. 相似文献
78.
《Mathematische Nachrichten》2017,290(1):120-141
We obtain general lower estimates of transition densities of jump Lévy processes. We use them for processes with Lévy measures having bounded support, processes with exponentially decaying Lévy measures for large times and for processes with high intensity of small jumps for small times. 相似文献
79.
《Mathematische Nachrichten》2017,290(5-6):738-755
We introduce some general classes of pseudodifferential operators with symbols admitting exponential type growth at infinity and we prove mapping properties for these operators on Gelfand–Shilov spaces. Moreover, we deduce composition and certain invariance properties of these classes. 相似文献
80.
Lin Feng Wang Ze Yu Zhang Liang Zhao Yu Jie Zhou 《Mathematical Methods in the Applied Sciences》2017,40(4):992-1002
We prove that on a smooth metric measure space with m ?Bakry–Émery curvature bounded from below by ?(m ? 1)K for some constant K ≥0 (i.e., Ricf ,m ≥?(m ? 1)K ), the following degenerate elliptic equation (0.1) has no nonconstant positive solution when p > 1 and constant λ f ,p satisfies Our approach is based on the local Sobolev inequality and the Moser's iterative technique and is different from Cheng‐Yau's method, which was used by Wang‐Zhu in 2012 to derive a same Liouville theorem when 1 < p ≤2, Ricf ,m ≥?(m ? 1)K and the sectional curvature is bounded from below. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献