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791.
792.
Synthesis of Chiral Exocyclic Amines by Asymmetric Hydrogenation of Aromatic Quinolin‐3‐amines 下载免费PDF全文
Xian‐Feng Cai Ran‐Ning Guo Mu‐Wang Chen Lei Shi Prof. Yong‐Gui Zhou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7245-7248
Asymmetric hydrogenation of aromatic quinolin‐3‐amines was successfully developed with up to 94 % enantiomeric excess (ee). Introduction of the phthaloyl moiety to the amino group is crucial to eliminate the inhibition effect caused by the substrate and product, to activate the aromatic ring, and to improve the diastereoselectivity. This new methodology provides direct and facile access to chiral exocyclic amines. Notably, this report is the first on the highly enantioselective hydrogenation of aromatic amines. 相似文献
793.
Zongke Xu Dr. Guotao Duan Prof. Yue Li Dr. Guangqiang Liu Dr. Hongwen Zhang Zhengfei Dai Prof. Weiping Cai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6040-6046
CuO–ZnO micro/nanoporous array‐films are synthesized by transferring a solution‐dipped self‐organized colloidal template onto a device substrate and sequent heat treatment. Their morphologies and structures are characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectrum analysis. Based on the sensing measurement, it is found that the CuO–ZnO films prepared with the composition of [Cu2+]/[Zn2+]=0.005, 0.01, and 0.05 all show a nice sensitivity to 10 ppm H2S. Interestingly, three different zones exist in the patterns of gas responses versus H2S concentrations: a platform zone, a rapidly increasing zone, and a slowly increasing zone. Further experiments show that the hybrid CuO–ZnO porous film sensor exhibits shorter recovery time and better selectivity to H2S gas against other interfering gases at a concentration of 10 ppm. These new sensing properties may be due to a depletion layer induced by p–n junction between p‐type CuO and n‐type ZnO and high chemical activity of CuO to H2S. This work will provide a new construction route of ZnO‐based sensing materials, which can be used as H2S sensors with high performances. 相似文献
794.
Photochemically Engineering the Metal–Semiconductor Interface for Room‐Temperature Transfer Hydrogenation of Nitroarenes with Formic Acid 下载免费PDF全文
Dr. Xin‐Hao Li Yi‐Yu Cai Ling‐Hong Gong Dr. Wei Fu Dr. Kai‐Xue Wang Dr. Hong‐Liang Bao Dr. Xiao Wei Dr. Jie‐Sheng Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16732-16737
A mild photochemical approach was applied to construct highly coupled metal–semiconductor dyads, which were found to efficiently facilitate the hydrogenation of nitrobenzene. Aniline was produced in excellent yield (>99 %, TOF: 1183) using formic acid as hydrogen source and water as solvent at room temperature. This general and green catalytic process is applicable to a wide range of nitroarenes without the involvement of high‐pressure gases or sacrificial additives. 相似文献
795.
Cross‐linked starch‐based polymer as an SPE material for the determination of nitrophenols at trace levels in environmental water 下载免费PDF全文
Qian Zhang Tao Liang Lingqing Wang Yaqi Cai Chukwunonso Peter Okoli 《Journal of separation science》2014,37(3):257-264
SPE using a cross‐linked starch‐based polymer (CSMDI) as an adsorbent for the determination of four nitrophenols at trace levels from aqueous solution was investigated. The CSMDI was synthesized from native starch using 4,4′‐methylenebisphenyldiisocyanate as a cross‐linking agent in dry DMF. Parameters affecting the extraction efficiency including the pH of the water sample, type of eluent and its volume, flow rate, sample volume, and methanol content were investigated and optimized. The optimized results exhibited excellent linear relationships (R2 > 0.995) for all the nitrophenols over the range of 2.0–200 ng/mL, with the RSD values in the range of 2.9–5.7% (n = 5). The LODs ranged from 0.08–0.34 ng/mL (S/N = 3) for the four nitrophenols tested under optimum conditions. The developed method has been successfully applied for the analysis of several real environmental water samples including tap, river, and reservoir water. These results indicated that the CSMDI had a tremendous potential for the enrichment and determination of nitrophenols at trace levels in environmental water samples. 相似文献
796.
Jing Jiang Fang Tian Yun Cai Xiaohong Qian Catherine E. Costello Wantao Ying 《Analytical and bioanalytical chemistry》2014,406(25):6265-6274
Recombinant human erythropoietin (rhEPO) has been extensively used as a pharmaceutical product for treating anemia. Glycosylation of rhEPO affects the biological activity, immunogenicity, pharmacokinetics, and in-vivo clearance rate of rhEPO. Characterization of the glycosylation status of rhEPO is of great importance for quality control. In this study, we established a fast and comprehensive approach for reliable characterization and relative quantitation of rhEPO glycosylation, which combines multiple-enzyme digestion, hydrophilic-interaction chromatography (HILIC) enrichment of glycopeptides, and tandem mass spectrometry (MS) analysis. The N-linked and O-linked intact glycopeptides were analyzed with high-resolution and high-accuracy (HR–AM) mass spectrometry using an Orbitrap. In total, 74 intact glycopeptides from four glycosylation sites at N24, N38, N83, and O126 were identified, with the simultaneous determination of peptide sequences and glycoform compositions. The extracted ion chromatograms based on the HR–AM data enabled relative quantification of glycoforms. Our results could be extended to quality control of rhEPO or could help establish detection approaches for glycosylation of other proteins. Graphical Abstract
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797.
Qilong Xie Shuhui Liu Yingying Fan Jianzhi Sun Xiaoke Zhang 《Analytical and bioanalytical chemistry》2014,406(18):4563-4569
A selective and low organic-solvent-consuming method of sample preparation combined with high-performance liquid chromatography with diode-array detection is introduced for analysis of phthalic acid esters in edible oils. Sample treatment involves initial liquid–liquid partitioning with acetonitrile, then QuEChERS cleanup by dispersive solid-phase extraction with primary secondary amine as sorbent. Preconcentration of the analytes is performed by ionic-liquid-based dispersive liquid–liquid microextraction, with the cleaned-up extract as disperser solvent and 1-hexyl-3-methylimidazolium hexafluorophosphate as extraction solvent. Under the optimized conditions, correlation coefficients (r) were 0.998–0.999 and standard errors (S y/x ) were 2.67–3.37?×?103 for calibration curves in the range 50–1000 ng g?1. Detection limits, at a signal-to-noise ratio of 3, ranged from 6 to 9 ng g?1. Intra-day and inter-day repeatability, expressed as relative standard deviation, were in the ranges 1.0–6.9 % and 2.4–9.4 %, respectively. Recovery varied between 84 % and 106 %. The developed method was successfully used for analysis of the analytes in 28 edible oils. The dibutyl phthalate content of four of the 28 samples (14 %) exceeded the specific migration limit established by domestic and international regulations. Figure
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798.
Bin Cai Jun-Wei Zhao Bai-Feng Yang Huan He Guo-Yu Yang 《Journal of Cluster Science》2014,25(4):1047-1059
Hydrothermal reactions of trilacunary precursor A-α-AsW9O34 9? polyoxoanions and nickel ions in the presence of ethylenediamine (en = ethylenediamine) led to two new hexa-Ni-substituted Keggin-type tungstoarsenates [Ni6(μ 3-OH)3(en)3(H2O)6(B-α-AsW9O34)]·6H2O (1) and [Ni6(μ 3-OH)3(en)3(H2O)6(B-α-AsW9O34)]·10H2O (2), which have been characterized by elemental analyses, IR spectra, powder X-ray diffraction, thermogravimetric analyses and single-crystal X-ray diffraction. Crystal data for 1: hexagonal, R3c, a = b = 20.4379(5) Å, c = 21.5062(6) Å, β = 120º, V = 7779.8 (3) Å3 and Z = 6; for 2: momoclinic, P21/c, a = 13.4200(3) Å, b = 19.1428(5) Å, c = 22.8845(9) Å, β = 112.403(3)º, V = 5435.2(3) Å3 and Z = 4. Structural analyses reveal that the [Ni6(μ 3-OH)3(B-α-AsW9O34)] clusters in 1 and 2 are covalently functionalized by neutral en ligands, in which two similar {Ni6(μ 3-OH)3(en)3(H2O)6}9+ cores have been observed by our lab. Notably, 1 and 2 represent the highest number of substituted transition metal ions in all known lacunary Keggin-type polyoxotungstoarsenate monomers. 相似文献
799.
800.
Jun‐Jie Shen Prof. Shou‐Fei Zhu Dr. Yan Cai Huan Xu Xiu‐Lan Xie Prof. Qi‐Lin Zhou 《Angewandte Chemie (International ed. in English)》2014,53(48):13188-13191
An iron‐catalyzed asymmetric intramolecular cyclopropanation was realized in high yields and excellent enantioselectivity (up to 97 % ee) by using the iron complexes of chiral spiro‐bisoxazoline ligands as catalysts. The superiority of iron catalysts exhibited in this reaction demonstrated the potential abilities of this sustainable metal in asymmetric carbenoid transformation reactions. 相似文献