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991.
《Comptes Rendus Chimie》2015,18(6):607-610
A concise, facile and straightforward synthetic method has been described for the synthesis of 2-(3-amino-2-oxoindolin-3-yl)-3-hydroxynaphthalene-1,4-dione derivatives by a one-pot, three-component reaction of isatins, 2-hydroxy-1,4-naphthoquinone and ammonium acetate under catalyst-free conditions in ethanol. This protocol becomes highly efficient due to its mild reaction conditions, operational simplicity, and overall good to excellent yields (80–99%). 相似文献
992.
Bifunctional Polyacrylonitrile Fiber‐Mediated Conversion of Sucrose to 5‐Hydroxymethylfurfural in Mixed‐Aqueous Systems 下载免费PDF全文
Dr. Xian‐Lei Shi Min Zhang Huikun Lin Minli Tao Prof. Dr. Yongdan Li Prof. Dr. Wenqin Zhang 《化学:亚洲杂志》2015,10(3):752-758
A highly efficient catalytic system composed of a bifunctional polyacrylonitrile fiber (PANF‐PA[BnBr]) and a metal chloride was employed to produce 5‐hydroxymethylfurfural (HMF) from sucrose in mixed‐aqueous systems. The promoter of PANF‐PA[BnBr] incorporates protonic acid groups that promote the hydrolysis of the glycosidic bond to convert sucrose into glucose and fructose, and then catalyzes fructose dehydration to HMF, while the ammonium moiety may promote synergetically with the metal chloride the isomerization of glucose to fructose and transfer HMF from the aqueous to the organic phase. The detailed characterization by elemental analysis, FTIR spectroscopy, and SEM confirmed the rangeability of the fiber promoter during the modification and utilization processes. Excellent results in terms of high yield (72.8 %) of HMF, superior recyclability (6 cycles) of the process, and effective scale‐up and simple separation procedures of the catalytic system were obtained. Moreover, the prominent features (high strength, good flexibility, etc.) of the fibers are very attractive for fix‐bed reactor. 相似文献
993.
Prof. Dr. Konstantin V. Kudryavtsev Chia‐Chun Yu Polina M. Ivantcova Prof. Dr. Vladimir I. Polshakov Dr. Andrei V. Churakov Prof. Dr. Stefan Bräse Prof. Dr. Nikolay S. Zefirov Prof. Dr. Jih‐Hwa Guh 《化学:亚洲杂志》2015,10(2):383-389
Functionalized oligomeric organic compounds with well‐defined β‐proline scaffold have been synthesized by a cycloadditive oligomerization approach in racemic and enantiopure forms. The structure of the novel β‐peptides was investigated by NMR spectroscopic and X‐ray methods determining the conformational shapes of the β‐proline oligomers in solution and solid states. The main structural elements subject to conformational switches are β‐peptide bonds between 5‐arylpyrrolidine‐2‐carboxylic acid units existing in Z/E configurations. The whole library of short β‐peptides and intermediate acrylamides has been tested on antiproliferative activity towards the hormone‐refractory prostate cancer cell line PC‐3 revealing several oligomeric compounds with low micromolar and submicromolar activities. Bromine‐substituted dimeric and trimeric acrylamides induced caspase‐dependent apoptosis of PC‐3 cells through cell‐cycle arrest and mitochondrial damage. 相似文献
994.
Total Synthesis of Proposed Structure of Yuremamine and All Diastereomers Using [3+2]‐Cycloaddition of Platinum‐Containing Azomethine Ylide 下载免费PDF全文
Tomoya Ohyama Masako Uchida Prof.Dr. Hiroyuki Kusama Prof. Dr. Nobuharu Iwasawa 《化学:亚洲杂志》2015,10(9):1850-1853
Total synthesis of the proposed structure of yuremamine has been achieved for the first time based on the intermolecular [3+2]‐cycloaddition reaction of the platinum‐containing azomethine ylide. All the possible diastereomers of yuremamine were also synthesized via the common intermediate. Through these syntheses, it was confirmed that the proposed structure of yuremamine and the diastereomers differ from the natural product. 相似文献
995.
One Step Preparation of Reduced Graphene Oxide/Pd–Fe3O4@Polypyrrole Composites and Their Application in Catalysis 下载免费PDF全文
Dr. Tongjie Yao Hao Wang Quan Zuo Dr. Jie Wu Dr. Xiao Zhang Dr. Fang Cui Dr. Tieyu Cui 《化学:亚洲杂志》2015,10(9):1940-1947
The simple preparation of catalysts with superior catalytic activity and good reusability is highly desirable. Herein, we report a novel strategy to construct reduced graphene oxide (rGO)/Pd–Fe3O4@polypyrrole (PPy) catalysts with Pd and Fe3O4 nanoparticles anchored on a rGO nanosheet surface and wrapped in a PPy shell. The synthesis and assembly of both the Pd and Fe3O4 nanoparticles, the preparation of the PPy layer, and the reduction of graphene oxide nanosheets were finished in one step. In the system, the PPy layer not only prevented aggregation of Pd and Fe3O4 nanoparticles, but also generated a synergistic effect with precursor Pd2+ ions, which led to a high dispersity of as‐prepared Pd nanoparticles. Although the procedure was simplified to one step, the catalytic activity and reusability were not sacrificed. In the reduction of 4‐nitrophenol, their catalytic performance was better than that in recent reports. Moreover, the catalysts showed good reusability owing to their magnetic properties. 相似文献
996.
Platinum‐Catalyzed Cascade Rearrangement Reaction of 1,5‐Diynyl Esters: Unusual Regioselective 1,5‐Hydride Migration 下载免费PDF全文
A highly regioselective sequential 1,3‐acyloxy migration/pentannulation/1,5‐hydride migration reaction is disclosed which provides an efficient access to (E)‐2‐vinyl‐3‐oxo‐1‐methyleneindenes under neutral and mild reaction conditions. The migrated hydrogen atom was derived from an unactivated alkyl group, and the long‐range 1,5‐H shift was confirmed through related deuterium experiments. 相似文献
997.
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
998.
The mechanism of the gold nanocluster‐catalyzed aerobic homocoupling of arylboronic acids has been elucidated by means of DFT calculations with Au20? as a model cluster for the Au:[poly(N‐vinylpyrrolidin‐2‐one)] catalyst. We found that oxygen affects the adsorption of phenylboronic acid and, by lowering the energy barrier, a water molecule enhances dissociation of the C?B bond, which is probably the rate‐determining step. The key role of oxygen is in activating the surface of the gold cluster by generating Lewis acidic sites for adsorption and activation of the phenylboronic acid, leading to the formation of biphenyl through a superoxo‐like species. Moreover, the oxygen adsorbed on the Au nanocluster can act as an oxidant for phenylboronic acid, giving phenol as a byproduct. As shown by NBO analysis, the basic aqueous reaction medium facilitates the reductive elimination process by weakening the Au?C bond, thereby enhancing the formation of biphenyl. The coupling of phenyl and reductive elimination of biphenyl occur at the top or facet site with low‐energy‐barrier through spillover of phenyl group on Au NC. The present findings are useful for the interpretation or design of other coupling reactions with Au NC. 相似文献
999.
Direct Synthesis of Controlled‐Size Nanospheres inside Nanocavities of Self‐Organized Photopolymerizing Soft Oxometalates [PW12O40]n (n=1100–7500) 下载免费PDF全文
The unusual self‐assembly of {(BMIm)2(DMIm)[PW12O40]}n (n=1100–7500) (BMIm=1‐butyl‐3‐methylimidazolium, DMIm=3,3′‐dimethyl‐1,1′‐diimidazolium) soft oxometalates (SOMs) with controlled size and a hollow nanocavity was exploited for the photochemical synthesis of polymeric nanospheres within the nanocavity of the SOM. The SOM vesicle has been characterized by using several techniques, including dynamic light scattering (DLS), static light scattering (SLS), attenuated total reflection (ATR) IR spectroscopy, Raman spectroscopy, microscopy, and zeta‐potential analysis. The self‐assembly and stabilization of this soft‐oxometalate vesicle has been shown by means of counter‐ion condensation. The immediate implication of such stabilization—the variation of the dielectric constant with the hydrodynamic radius of the vesicle—has been used to synthesize vesicles of controlled size. Such vesicles of varying size have been used as templates for polymerization reactions that produce polymeric spheres of controlled size. Direct evidence shows that the SOM behaves as a model heterogeneous catalytic system. Such surfactant‐ and initiator‐free photochemical synthetic routes for obtaining uniform latex spheres could be used in the making of optical bandgap materials, inverse opals, and paints. 相似文献
1000.
分光光度法测定土壤中碘的方法改进 总被引:2,自引:0,他引:2
对碳酸钠-氧化锌熔矿,分光光度法测定土壤样品中碘含量的方法进行改进,在不经过超级恒温水浴的情况下,对熔样温度、试剂用量的选择、比色温度等实验条件进行优化。改进后的方法经过国家一级标准物质分析验证,准确度ΔlgC0.05,相对标准偏差(RSD)10%,结果准确可靠,完全满足地球化学调查样品中对碘的质量要求,更加适合批量生产。 相似文献