排序方式: 共有123条查询结果,搜索用时 15 毫秒
71.
Michael Maes Maarten Trekels Mohammed Boulhout Stijn Schouteden Frederik Vermoortele Luc Alaerts Daniela Heurtaux You‐Kyong Seo Young Kyu Hwang Jong‐San Chang Isabelle Beurroies Renaud Denoyel Kristiaan Temst Andre Vantomme Patricia Horcajada Christian Serre Dirk E. DeVos 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2011,123(18):4296-4300
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Using a small scale test-rig a number of experiments were performed in which the imposed disk velocity v
disk, the different mechanical parameters of the test-rig (damping c and tangential stiffness k), and normal load were varied independently. 相似文献
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Kaval N Singh BK Ermolat'ev DS Claerhout S Parmar VS der Eycken JV der Eycken EV 《Journal of combinatorial chemistry》2007,9(3):446-453
A new transition metal-catalyzed orthogonal solid-phase protocol for the synthesis of highly substituted 2(1H)-pyrazinones was developed, on the basis of Chan-Lam arylation and Liebeskind-Srogl cross-coupling reactions. This strategy opens the way for the generation of small libraries of 2(1H)-pyrazinone analogues for biological screening. 相似文献
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Dr. Eduard Badarau Dr. K. Harsha Vardhan Reddy Dr. Aurore Loudet Dr. Charles Simon Dr. Laurent Trembleau Dr. Stijn Claerhout Dr. Etienne Pair Stéphane Massip Dr. Philippe Breton Dr. Brigitte Lesur Dr. Solo Goldstein Dr. Jean-Marie Fourquez Dr. Jean Michel Henlin Prof. Léon Ghosez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(67):15477-15481
Identification of a common Diels–Alder pattern in three classes of bioactive natural products led us to study the synthesis and cycloaddition of a new class of cyclic dienes readily available from β,γ-unsaturated lactams. A practical and readily scalable route to the parent p-methoxybenzyl-protected 6- and 7-membered β,γ-unsaturated lactams was developed. These were readily transformed into the corresponding O-silylated dienes, which were reacted with dimethyl and diethyl fumarate to yield stereoselectively highly functionalized bicyclic adducts. These exhibited unexpected and versatile transformations upon acid hydrolysis depending on the nature of the dienophile substituents and the acid catalyst. All reactions have been performed on multigram quantities. These transformations provide a convenient, economical, and easily scalable pathway for the rapid construction of functionally and stereochemically dense privileged scaffolds for the construction of libraries of natural products-inspired molecules of pharmacological relevance. 相似文献
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Omelchenko IV Shishkin OV Gorb L Leszczynski J Fias S Bultinck P 《Physical chemistry chemical physics : PCCP》2011,13(46):20536-20548
The degree of aromaticity of six-membered monoheterocycles with IV-VI group heteroatoms (C(6)H(5)X, where X = SiH, GeH, N, P, As, O(+), S(+), Se(+)) was analyzed using the results of ab initio calculations at the MP2/cc-pvtz level. Values of common aromaticity indices including those based on electronic delocalization properties, structural-dynamic features and magnetic properties all indicate high aromaticity of all considered heterocycles. A decrease in aromaticity is observed with increasing atomic number of the heteroatom, except in the case of the pyrylium cation. However, not all types of indices or even different indices within the same type correlate well among each other. Ring currents have been obtained at the HF/cc-pvdz level using the ipsocentric formulation. Ring current maps indicate that in the case of cationic heterocycles the ring current persists in all molecules under consideration. The different conclusions reached depending on the type of index used are a manifestation of the fact that when not dealing with hydrocarbons, aromaticity is ill-defined. One should always express explicitly which property of the molecules is considered to establish a degree of "aromaticity". 相似文献
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Hagendorfer H Kaegi R Traber J Mertens SF Scherrers R Ludwig C Ulrich A 《Analytica chimica acta》2011,706(2):367-378
In this work we discuss about the method development, applicability and limitations of an asymmetric flow field flow fractionation (A4F) system in combination with a multi-detector setup consisting of UV/vis, light scattering, and inductively coupled plasma mass spectrometry (ICPMS). The overall aim was to obtain a size dependent-, element specific-, and quantitative method appropriate for the characterization of metallic engineered nanoparticle (ENP) dispersions. Thus, systematic investigations of crucial method parameters were performed by employing well characterized Au nanoparticles (Au-NPs) as a defined model system.For good separation performance, the A4F flow-, membrane-, and carrier conditions were optimized. To obtain reliable size information, the use of laser light scattering based detectors was evaluated, where an online dynamic light scattering (DLS) detector showed good results for the investigated Au-NP up to a size of 80 nm in hydrodynamic diameter. To adapt large sensitivity differences of the various detectors, as well as to guarantee long term stability and minimum contamination of the mass spectrometer a split-flow concept for coupling ICPMS was evaluated. To test for reliable quantification, the ICPMS signal response of ionic Au standards was compared to that of Au-NP. Using proper stabilization with surfactants, no difference for concentrations of 1–50 μg Au L−1 in the size range from 5 to 80 nm for citrate stabilized dispersions was observed. However, studies using different A4F channel membranes showed unspecific particle–membrane interaction resulting in retention time shifts and unspecific loss of nanoparticles, depending on the Au-NP system as well as membrane batch and type. Thus, reliable quantification and discrimination of ionic and particular species was performed using ICPMS in combination with ultracentrifugation instead of direct quantification with the A4F multi-detector setup.Figures of merit were obtained, by comparing the results from the multi detector approach outlined above, with results from batch-DLS and transmission electron microscopy (TEM). Furthermore, validation performed with certified NIST Au-NP showed excellent agreement. The developed methods show potential for characterization of other commonly used and important metallic engineered nanoparticles. 相似文献
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Brooks NR Schaltin S Van Hecke K Van Meervelt L Binnemans K Fransaer J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(18):5054-5059
New metal-containing ionic liquids [Cu(CH(3)CN)(n)][Tf(2)N] (n=2, 4; Tf(2)N=bis(trifluoromethylsulfonyl)- amide) have been synthesised and used as a non-aqueous electrolyte for the electrodeposition of copper at current densities greater than 25 A dm(-2). The tetrahedral copper(I)-containing cation in [Cu(CH(3)CN)(4)][Tf(2)N] is structurally analogous to quaternary ammonium and phosphonium ionic liquids and overcomes problems of metal solubility and mass transport. Two CH(3)CN ligands are removed at elevated temperatures to give [Cu(CH(3)CN)(2)][Tf(2)N], which can be used as a concentrated non-aqueous electrolyte. The structural and electrochemical characterisation of these compounds is described herein. 相似文献