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31.
Alexander KomechRID=""ID=""Supported partly by French–Russian A.M.Liapunov Center of Moscow State University by Max-Planck Institute for Mathematics in the Sciences by research grants of INTAS of Volkswagen-Stiftung. Markus KunzeRID=""ID=""Supported by DAAD andNSF during a stay at Brown University
<AU><FNMS>Herbert<SNM>Spohn<ORF RID="a" 《Communications in Mathematical Physics》1999,203(1):1-19
32.
Katy B. Wilson Hannah S. Nedzbala Spenser R. Simpson Megan N. Ericson Karl S. Westendorff Mahendra D. Chordia Diane A. Dickie W. Dean Harman 《Helvetica chimica acta》2021,104(10):e2100103
Reactions are described for complexes of the form WTp(NO)(PMe3)(η2-arene) and various amines, where the arene is benzene or benzene with an electron-withdrawing substituent (CF3, SO2Ph, SO2Me). The arene complex is first protonated to form an η2-arenium species, which then selectively adds the amine. The resulting η2-5-amino-1,3-cyclohexadiene complexes can then be subjected to the same sequence with a second nucleophile to form 3-aminocyclohexene complexes, where up to three stereocenters originate from the arene carbons. Alternatively, 1,3-cyclohexadiene complexes containing an ester group at the 5 position (also prepared from an arene) can be treated with acid followed by an amine to form trisubstituted 3-aminocyclohexenes. When the amine is primary, ring closure can occur to form a cis-fused bicyclic γ-lactam. Highly functionalized cyclohexenes can be liberated from the tungsten through oxidative decomplexation. The potential utility of this methodology is demonstrated in the synthesis of the alkaloid γ-lycorane. An enantioenriched synthesis of a lactam precursor to γ-lycorane is also described. This compound is prepared from an enantioenriched version of the tungsten benzene complex. Regio- and stereochemical assignments for the reported compounds are supported by detailed 2D-NMR analysis and 13 molecular structure determinations (SC-XRD). 相似文献
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34.
Ashraf Ghanem Volker SchurigRID="a"ID="a" Dedicated to the Memory of Prof. <E>E. Bayer</E> – 《Monatshefte für Chemie / Chemical Monthly》2003,134(8):1151-1157
Summary. Asymmetric acetylation of a set of secondary alcohols with the innocuous acyl donor isopropenyl acetate catalyzed by a lipase from Pseudomonas cepacia immobilized on ceramic particles (PSL-C) in toluene as organic medium afforded the chiral alcohols and the corresponding acetates in high enantiomeric excess (up to 99%). An effective baseline separation of the enantiomers of both substrate and product was performed in one analysis without derivatization using gas chromatography on a new chiral stationary phase (CSP) Chirasil--Dex containing an undecamethylene spacer (C11-Chirasil-Dex).Received November 27, 2002; accepted (revised) January 9, 2003
Published online June 2, 2003 相似文献
35.
Pierre?SchapiraEmail authorView authors OrcID profile 《Mathematical Physics, Analysis and Geometry》2017,20(3):21
We extend the classical Wick rotation to D-modules and higher codimensional submanifolds. 相似文献
36.
Preeti?Luthra Ajay?KumarEmail authorView authors OrcID profile Vandana?Rajpal 《Positivity》2018,22(2):629-652
We extend the \(\lambda \)-theory of operator spaces given in Defant and Wiesner (J. Funct. Anal. 266(9): 5493–5525, 2014), that generalizes the notion of the projective, Haagerup and Schur tensor norm for operator spaces to matrix ordered spaces and Banach \(*\)-algebras. Given matrix regular operator spaces and operator systems, we introduce cones related to \(\lambda \) for the algebraic operator space tensor product that respect the matricial structure of matrix regular operator spaces and operator systems, respectively. The ideal structure of \(\lambda \)-tensor product of \(C^*\)-algebras has also been discussed. 相似文献
37.
Incorporation studies with 13C-, 15N-, and 2H-labeled substrates, followed by NMR analysis, show that the pyrimidine unit of thiamin (Vitamin B1) originates from a C5N fragment, derived from C-2',2,N,C-6,5,5' of pyridoxol (Vitamin B6) and an N-C-N fragment derived from L-histidine. Urocanic acid serves as an intermediate on the route of the N-C-N fragment of histidine into the thiamin pyrimidine. 相似文献
38.
Laura?Geatti Claudio?GorodskiEmail authorView authors OrcID profile 《Algebras and Representation Theory》2017,20(3):751-764
We study polar representations in the sense of Dadok and Kac which are symplectic. We show that such representations are coisotropic and use this fact to give a classification. We also study their moment maps and prove that they separate closed orbits. Our work can also be seen as a specialization of some of the results of Knop on multiplicity free symplectic representations to the polar case. 相似文献
39.
John W. Whitley Ian A. Adams Kelsey L. Terrill Spenser S. Hayward Michael T. Burnette Jason E. Bara 《Journal of polymer science. Part A, Polymer chemistry》2016,54(13):2004-2014
Here, we provide a detailed report on a new type of structured media for improving photopolymerizations: coordinated ionic liquids (ILs). Coordinated ILs are readily formed from the bistriflimide ([Tf2N]?) anion and coordination complexes composed of Li+ cations with polar organic monomers without an additional cosolvent. Photopolymerization kinetics and monomer conversion were monitored in real time using attenuated total reflectance Fourier transform infrared spectroscopy and the material properties of the products were examined using gel permeation chromatography and differential scanning calorimetry. Generally, coordinated IL monomers displayed improved reaction kinetics at both high and low salt concentrations as well as distinct product properties. The noncovalent (and reversible) interactions between monomer and salt in coordinated ILs hold promise as an efficient and versatile form of structured media for photopolymerizations. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2004–2014 相似文献
40.
Xi?Chen Zheng-Zhe?LinEmail authorView authors OrcID profile 《Journal of nanoparticle research》2018,20(5):136
In recent years, two-dimensional confined catalysis, i.e., the enhanced catalytic reactions in confined space between metal surface and two-dimensional overlayer, makes a hit and opens up a new way to enhance the performance of catalysts. In this work, graphdiyne overlayer was proposed as a more excellent material than graphene or hexagonal boron nitride for two-dimensional confined catalysis on Pt(111) surface. Density functional theory calculations revealed the superiority of graphdiyne overlayer originates from the steric hindrance effect which increases the catalytic ability and lowers the reaction barriers. Moreover, with the big triangle holes as natural gas tunnels, graphdiyne possesses higher efficiency for the transit of gaseous reactants and products than graphene or hexagonal boron nitride. The results in this work would benefit future development of two-dimensional confined catalysis. 相似文献