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991.
Najla Al ShayeSameer Chavda Elliot CoulbeckJason Eames Yonas Yohannes 《Tetrahedron: Asymmetry》2011,22(4):439-463
The parallel resolution of racemic pentafluorophenyl 2-aryl/phenylpropanoates and butanoates using an equimolar combination of quasi-enantiomeric Evans oxazolidin-2-ones is discussed. The levels of diastereoselectivity were excellent (>90% de) leading to separable quasi-enantiomeric oxazolidin-2-ones in good yield. This methodology was used to resolve a series of structurally related 2-aryl/phenylpropanoic and butanoic acids. 相似文献
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996.
Sumiko Matsumura Antisar R. Hlil Mohammed A. K. Al‐Souz Julie Gaudet Daniel Guay Allan S. Hay 《Journal of polymer science. Part A, Polymer chemistry》2009,47(20):5461-5473
The synthesis and properties of the first examples of dendritic multiblock co PES s, bearing sulfonated dendritic clusters, that form strong membranes are described. End‐capped dendritic multiblock co PES s with various average block lengths (n = 50–80) were synthesized by two‐step reactions. The synthesis of dendritic blocks consisting of difunctional dendritic block and monofunctional dendritic end‐group was accomplished by an aromatic nucleophilic substitution reaction of hexakis(4‐(4‐fluorophenylsulfonyl)phenyl)benzene with varying amounts of 1‐(4‐hydroxyphenyl)‐2,3,4,5,6‐pentaphenylbenzene, which provides a number of pendant phenyl rings as postsulfonation sites. Polycondensation of a controlled molar ratio between 4,4′‐dihydroxybenzophenone and bis(4‐fluorophenyl)sulfone monomers was carried out in the presence of the difunctional and monofunctional dendritic blocks in sulfolane at 215 °C for 3.5 h. Essentially six sulfonic acid groups were introduced into each hexaphenylbenzene moiety on the dendritic blocks by reaction with a large excess of chlorosulfonic acid, followed by hydrolysis with KOH aqueous solution. The introduction of longer average blocks (n = 60–80) into the dendritic PES s improved the mechanical properties of the resulting sulfonated dendritic PES membranes. At a level of IEC (0.92–1.26 meq/g) similar to Nafion (0.91 meq/g), PES membranes showed proton conductivities (58–67 mS/cm) comparable with that of Nafion (99 mS/cm). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5461–5473, 2009 相似文献
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In this work a simple technique to extract the texture function in granular thin film media is implemented. The technique is based on previous work in which the distribution function of particles easy axes f(α) is calculated from the measured parallel remanence curve (Mrp(β)). In this simple technique we consider that the measured Mrp(β) curve can be fitted to a series of cos(2β), i.e. Mrp(β)=B0+B2 cos(2β)+B4 cos(4β) where the angle β is the angle by which the film is rotated. This approximation is found to be valid when the texture function has a standard deviation >20°. On this basis, the constants B0, B2 and B4 can be determined by using only three data points for the parallel remanence, Mrp(0), Mrp(45°) and Mrp(90°). The new technique is applied to a textured thin film consisting of cobalt ferrite particles 17 nm in diameter and to a commercial Sony video tape. Using this simple technique, the obtained texture functions are found to be similar to those obtained from the full Mrp(β) curves. This new technique will furnish a simple method with which the texture function in 2D systems can be obtained. 相似文献
999.
A highly convergent, short and stereoselective synthesis of a series of methoxy substituted 2, 3-dibenzylbutyrolactones was achieved using a Horner-Wadsworth-Emmons (HWE) reaction as the key step in overall yields above 32%. 相似文献
1000.
Hanane Al Bay Mustafa Taleb Nour-Eddine Benchat Brahim El Bali Michal Dusek 《合成通讯》2013,43(18):2767-2779
New N,N-bis(triazol-1-ylmethyl)amines have been prepared in one step by condensation of 1-(hydroxymethyl)triazole with a series of primary substituted aromatic amines. These reactions were carried out in refluxed CH3CN for 4 h. The products were recuperated with excellent and good yields (75–90.5%). The x-ray crystallography structure of one of them has been studied. 相似文献