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排序方式: 共有1783条查询结果,搜索用时 15 毫秒
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Konstantin N. Gavrilov Alexei A. Shiryaev Ilya V. Chuchelkin Sergey V. Zheglov Eugenie A. Rastorguev Vadim A. Davankov Armin Börner 《Tetrahedron: Asymmetry》2012,23(14):1052-1057
New P,P-bidentate diastereomeric diphosphoramidite chiral ligands with mixed stereogenic elements and a C1 backbone symmetry have been prepared from (Sa)- and (Ra)-1,1′-binaphthyl-2,2′-diol (BINOL) and (S)-N-benzyl-1-(pyrrolidin-2-yl)methanamine and are fully characterized. The use of these ligands provides up to 84% ee in the Pd-catalyzed asymmetric allylic substitution of (E)-1,3-diphenylallyl acetate and up to 95% ee in the Rh-catalyzed asymmetric hydrogenation of α-dehydrocarboxylic acid esters. The results indicate that the catalytic performance is highly affected by the axial chirality of the binaphthyl moieties of the ligand and the nature of the solvent. 相似文献
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A. G. Vitukhnovsky A. A. Vashchenko R. B. Vasiliev 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(7):803-807
Specific features of plane-geometry nanocrystals (CdSe nanoplatelets) functioning in an organic–inorganic light emitting diode are analyzed. 相似文献
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Wilson Merchan-Merchan Alexei V. Saveliev Walmy Cuello Jimenez 《Proceedings of the Combustion Institute》2011,33(2):1899-1908
In this paper we report the growth of 1-D and 3-D tungsten-oxide nanostructures on tungsten wire probes inserted in an opposed-flow oxy-fuel flame. The probe diameter and oxygen content in the oxidizer were varied to study their influence on the growth of tungsten-oxide nanostructures. The introduction of a 1-mm diameter W probe into the flame environment with an oxidizer composition of 50%O2 + 50%N2, resulted in the formation of 1-D nanorods on the upper surface of the probe. The formation of triangular, rectangular, square, and cylindrical 3-D channels with completely hollow or semi-hollow morphology was achieved by reducing the probe diameter to 0.5 mm. Whereas, the increase of the O2 content to 100% and the employment of a 1-mm probe resulted in the growth of ribbon-like micron-sized structures. The lattice spacing of ∼0.38 nm measured for the 1-D W-oxides closely matches a monoclinic WO3 structure. X-ray photoelectron spectroscopy analysis revealed that the larger 3-D structures also consist of WO3 confirming that the chemical composition of the structures remains the same while varying the probe and flame parameters. The proposed growth mechanism states that the 3-D WO3 structures are formed through the lateral coalescence of 1-D W-oxide nanorods. 相似文献
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Alexei Entin 《Geometric And Functional Analysis》2012,22(5):1322-1360
We study the distribution of the zeroes of the L-functions of curves in the Artin–Schreier family. We consider the number of zeroes in short intervals and obtain partial results which agree with a random unitary matrix model. 相似文献
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Dr. Yashapal Singh Prof. Dr. Alexei V. Demchenko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1461-1465
The discovery that traditional silver(I)-oxide-promoted glycosidations of glycosyl bromides (Koenigs–Knorr reaction) can be greatly accelerated in the presence of catalytic trimethylsilyl trifluoromethanesulfonate (TMSOTf) is reported. The reaction conditions are very mild that allowed for maintaining a practically neutral pH and, at the same time, providing high rates and excellent glycosylation yields. In addition, unusual reactivity trends among a series of differentially protected glycosyl bromides were documented. In particular, benzoylated α-bromides were much more reactive than their benzylated counterparts under these conditions. 相似文献