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排序方式: 共有154条查询结果,搜索用时 46 毫秒
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Treatment of a wide range of functionalized hydroxyallenic esters with 5 mol % Ph(3)PAuCl and 5 mol % AgOTf in CH(2)Cl(2) at 25 °C for 1 h produced selectively 2-alkyl- and aryl-3-ethoxycarbonyl-2,5-dihydrofurans in good to excellent yield through intramolecular hydroalkoxylation by a 5-endo mode. 相似文献
35.
H. Kwak G. H. Eom S. H. Lee H. G. Koo S. P. Jang J. Lee W. Shin M. S. Lah C. Kim S.-J. Kim Y. Kim 《Journal of Structural Chemistry》2010,51(5):923-930
Five new Ni(II) complexes with pyridine carboxamide ligands have been synthesized and the crystal structures of three of the complexes were determined. Strong distortion effects of 6-methyl substitution were observed in the complexes with 6-methyl-substituted pyridyl bpb ligands. The C-H...F and C-H...O hydrogen bond interactions build extended architectures in the crystals studied. This result suggests that the steric effect of 6-methyl substitution plays an important role in the distortion of the structure, and the 6-methyl substitution can facilitate hydrogen bond interactions between methyl hydrogen atoms and O(carbonyl) or F atoms. Twelve Ni(II) complexes, including seven complexes reported previously, show reversible redox behavior, implying that the reduced Ni(I) state of each complex is stable in the time scale of CV measurement. The steric effect of R1 substituent and the electronic effects of X1 and X2 groups were found to be the main factors contributing to the shift of the redox potential of the Ni(II) complexes 相似文献
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[reaction: see text]. We herein report the development of one-pot procedures for the conversion of allyl aryl ethers to 2-methylbenzofurans (via sequential Claisen rearrangement and oxidative cyclization) and for the conversion of aryl homoallyl ethers to chromenes (via direct oxidative cyclization). It is likely that both reactions proceed via a common Pd-catalyzed pathway involving olefin activation, nucleophilic attack, and beta-hydride elimination. 相似文献
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D. W. Kim Y. S. Jeon T. Y. Eom M. Y. Suh C. H. Lee 《Journal of Radioanalytical and Nuclear Chemistry》1991,150(2):417-426
A study on the separation of Li isotopes was carried out with a resin having monobenzo-15-crown-5 as a functional group, synthesized by substitution reaction of chloromethylated styrene-DVB copolymer with 4-aminobenzo-15-crown-5. Adsorption properties of the resin for Li+ were invesgated with batch method in various solvents and counter anions. Upon column chromatography [0.9 cm (I. D.)×25 cm (height)] using 5% (v/v) H2O in acetonitrile as an eluent, single separation factor, , 1.053 (±0.005), (6Li/7Li)resin/ (6Li/7Li) solution was obtained by the GLUECKAUF method from the elution curve and isotope ratios. 相似文献
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Yeong Jae Park Kyung-Hoon Jung Kyoung Kyun Park Tae Yoon Eom 《Journal of colloid and interface science》1993,160(2)
The effects of o-phenanthroline and 2,2′-bipyridine on the adsorption of metal(II) (Fe, Co, Ni and Cu) ions onto silica gel surface have been studied. The adsorption is expressed in terms of the measured concentrations of both metal and ligand at equilibrium. Each adsorption of the four metal ions is increased with the presence of the ligands. In addition, adsorption increases slowly with pH at low pH values and then increases rapidly up to near the pKa value of silica gel (≈6.5). The adsorption of each metal ion at low pH is increased with increased ligand concentration. However, at high pH the adsorptions of Fe(II) and Cu(II) are decreased with increased ligand concentration whereas the adsorptions of Co(II) and Ni(II) are always increased. At low pH values the ligand to metal ratio adsorbed on the silica gel surface is ca. 3:1 while at high pH values it is 1:1, 2:1, and 3:1, corresponding to the initial ligand to metal ion concentration ratio. The addition of ethanol to the phenanthroline-SiO2 solution results in a decrease in the adsorption of phenanthroline. The effect of ethanol is also observed in the Fe(II)-phenanthroline-SiO2 system. The behavior of the adsorption is interpreted qualitatively by hydrophobic expulsion, the formation of surface complexes, and electrostatic interaction. It is concluded that hydrophobic expulsion plays an important role in the adsorption of metal ions in the presence of hydrophobic ligands on silica gel surface. 相似文献
39.
A. F. Hebard C. B. Eom R. M. Fleming Y. J. Chabal A. J. Muller S. H. Glarum G. J. Pietsch R. C. Haddon A. M. Mujsce M. A. Paczkowski G. P. Kochanski 《Applied Physics A: Materials Science & Processing》1993,57(3):299-303
The irradiation of sublimed fullerene (C60 and C70) thin films with ultraviolet light in an oxygen-rich ambient has been found to lead to a substantially increased cohesive energy in the fullerene solid. The decreased solubility and lower vapor pressure of the phototransformed material enables wet (organic solvents) or dry (thermal or photon-induced sublimation) development of photo-defined negative images. One micrometer wide lines with good edge definition are demonstrated. X-ray, infrared, optical absorption, and high performance liquid chromatography reveal that photo-oxygenated C60 retains its fcc crystal structure but with a substantial fraction of the C60 molecules modified with carbonyl (C=O) bonds. 相似文献
40.
We report the LPG pair device that can be used as a pulse duplicator or an OCDMA encoder/decoder. Due to the ring core region of dispersion compensating fiber (DCF), we can shorten the device length by a third and obtain surrounding insensitive LPG devices. 相似文献