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91.
Yunlong Wang Quanling Suo Limin Han Linlin Guo Yaqi Wang Fawang Li 《Tetrahedron》2018,74(15):1918-1925
An efficient protocol for the synthesis of unsymmetrical 1,3-diynes was developed using supercritical carbon dioxide (ScCO2) as the solvent. The direct coupling of two different terminal alkynes is catalysed by a bimetallic catalyst, CuCl2·2H2O/Pd(NH3)4Cl2·H2O, in the presence of the base tetramethylethylenediamine (TMEDA) and O2. In pure ScCO2, our bimetallic catalytic system maintains high activity over a wide substrate scope to provide unsymmetrical 1,3-diynes in good to excellent yields. In the proposed reaction mechanism, the synergistic cooperation between copper(II) and palladium(II) centres is responsible for the superior selectivity of the cross-coupling. 相似文献
92.
Chen Guo Feng Liu Lin Wu Jiu Li Wu Suo Juan Chen Bao Hua 《Research on Chemical Intermediates》2018,44(2):1381-1395
Research on Chemical Intermediates - Two novel fluorescent probes (C1, C2), comprising a coumarin moiety as fluorophore and a pair of dithiocarbamates as recognition sites, were designed and... 相似文献
93.
A polydopamine-based molecularly imprinted polymer was deposited on the surface of magnetite (ferroferric oxide) nanoparticles (Fe3O4@PDA MIPs) and is shown to be an efficient and fairly specific sorbent for the extraction of various ochratoxins. The MIPs were characterized by IR spectroscopy and transmission electron microscopy. The adsorption capacities, evaluated through the langmuir adsorption isotherm model, are 1.8, 0.23 and 0.17 mg·g?1 for ochratoxin A, ochratoxin B and ochratoxin C, respectively. Parameters such as the amount of magnetic MIPs, pH value, time for ultrasonication, elution solvent and volume were optimized. Following desorption from the MIP with acetonitrile, the ochratoxins were quantified by HPLC with fluorometric detection. Under optimal experimental conditions, the calibration plots are linear in the range of 0.01–1.0 ng·mL?1 of OTA, 0.02–2.0 ng·mL?1 of OTB, and 0.002–0.2 ng·mL?1 of OTC. The LODs are between 1.8 and 18 pg·mL?1, and the recoveries from spiked samples are 71.0% - 88.5%, with RSDs of 2.3–3.8% in case of rice and wine samples. The MIPs can be re-used for at least 7 times. 相似文献
94.
Han-wen Sun Feng-xia Qiao Ran Suo Li-xin Li Shu-xuan Liang 《Analytica chimica acta》2004,505(2):255-261
A new method was developed for simultaneous determination of trace arsenic and antimony in Chinese herbal medicines by hydride generation-double channel atomic fluorescence spectrometry with a Soxhlet extraction system and an n-octanol-water extraction system, respectively. The effects of analytical conditions on the fluorescence intensity were investigated and optimized. A water-dissolving and methanol-water-dissolving capability were compared. The contents of different species in five Chinese herbal medicines and their decoctions were analyzed. The concentration ratios of n-octanol-soluble As or Sb to water-soluble As or Sb were related to the kinds of medicine and the acidity of the decoction. Soxhlet extraction was found to be an effective method for plants pretreatment for determination of arsenic and antimony species in Chinese herbs; the interferences of coexisting ions were evaluated. The proposed method has the advantages of simple operation, high sensitivity and high speed, with 3σ detection limits of 0.094 μg g−1 for As(III), 0.056 μg g−1 for total As, 0.063 μg g−1 for Sb(III) and 0.019 μg g−1 for total Sb in a 1.0 g of the sample. 相似文献
95.
(3R,5R)-3,5-二羟基-6-取代己酸不对称合成研究进展 总被引:1,自引:0,他引:1
概述近 2 0年来 ( 3R ,5R) 3 ,5 二羟基 6 取代己酸不对称合成进展 ,并提出其研究方向 . 相似文献
96.
97.
New Diterpenoids from Coleus forskohlii 总被引:6,自引:0,他引:6
Two new diterpenoids, forskolin G and H were isolated from the chloroform extract of the roots of Coleus forskohlii, and based on spectroscopic data,their structures were identified as 1α-hydroxy-6β,7β-diacetoxy-8,13-epoxylabd-14-ene-11-one(1),and 1α,6β-diacetoxy-8,13-epoxy labd-14-ene-11-one (2),respectively. 相似文献
98.
CHEN Chunxia XU Chenghua FENG Liangrong SUO Jishuan & QIU Fali . Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu China . Graduate School of the Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2005,48(6)
Phenol hydroxylation is an industrially important reaction, whose main products are catechol and hy-droquinone being diverse applications which are im-portant intermediates for perfumes, drugs, and phar-maceuticals and so on[1]. The processes using H2O2 a… 相似文献
99.
Suo Hon Lim Cristiano Ferraris Martin Schreyer James O. Leckie 《Journal of solid state chemistry》2007,180(10):2905-2915
Photocatalysts of nominal composition (Ti1−xCox)O2−δ with 0.001?x?0.05 were prepared via a sol-gel technique followed by air firing (200-1000 °C). The incorporation of cobalt inhibited crystal growth and slightly raised the anatase to rutile transformation temperature (∼700 °C). An amorphous component was invariably significant with the maximum content (41-53 wt%) appearing simultaneously with the removal of anatase, suggesting that rutile crystallizes via an aperiodic structure. While the introduction of cobalt shifted the apparent band gap to visible light energies this did not enhance performance as there was limited miscibility of cobalt in titania, non-catalytic secondary phases were present, and active Ti3+ sites were displaced by cobalt. 相似文献
100.
Jianmin Wang Liang Yan Guang Qian Gaomeng Lv Guixian Li Jishuan Suo Xiaolai Wang 《Reaction Kinetics and Catalysis Letters》2007,91(1):111-118
The pyridine-heteropoly compounds are very active catalysts for phenol hydroxylation to dihydroxybenzenes with hydrogen peroxide
as oxidant in aqueous solutions. The conversion of phenol reaches 77.8%, and the selectivity for dihydroxybenzenes reaches
99%. 相似文献