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951.
Johan Granander Francesco Secci Peter O’Brien Brian Kelly 《Tetrahedron: Asymmetry》2009,20(21):2432-2434
The attempted kinetic resolution of racemic secondary phosphine boranes [t-BuPhP(BH3)H and t-BuMeP(BH3)H] by P–H deprotonation using 0.5 equiv of s-BuLi and (?)-sparteine was unsuccessful and generated racemic benzyl bromide-trapped adducts in 42–49% yield. In contrast, an efficient kinetic resolution was observed with racemic tertiary phosphine boranes [t-BuPhP(BH3)Me and t-BuEtP(BH3)Me] by C–H deprotonation on the P–Me group using 0.5 or 0.6 equiv of s-BuLi and (?)-sparteine. For example, the use of 0.6 equiv of s-BuLi/(?)-sparteine with t-BuEtP(BH3)Me and trapping with DMF gave the (R)-aldehyde adduct in 37% yield and 83:17 er together with recovered (R)-t-BuEtP(BH3)Me in 44% yield and 74:26 er. These are the first examples of kinetic resolution of P-stereogenic phosphine boranes via deprotonation using s-BuLi/(?)-sparteine. 相似文献
952.
Johan Schubert 《International Journal of Approximate Reasoning》2011,52(3):449-460
In this article we develop a method for conflict management within Dempster-Shafer theory. The idea is that each piece of evidence is discounted in proportion to the degree that it contributes to the conflict. This way the contributors of conflict are managed on a case-by-case basis in relation to the problem they cause. Discounting is performed in a sequence of incremental steps, with conflict updated at each step, until the overall conflict is brought down exactly to a predefined acceptable level. 相似文献
953.
954.
Margey Tadesse Johan SvensonMarcel Jaspars Morten B. StrømMostafa H. Abdelrahman Jeanette H. AndersenEspen Hansen Per E. KristiansenKlara Stensvåg Tor Haug 《Tetrahedron letters》2011,52(15):1804-1806
Synoxazolidinone C is a new member of the synoxazolidinone family of compounds which are dibrominated guanidinium 4-oxazolidinones isolated from the sub-Arctic ascidian Synoicum pulmonaria. The compound was isolated along with synoxazolidinones A and B from the same ascidian extract. Spectroscopic methods revealed that the synoxazolidinone C differed from the other synoxazolidinones by an unprecedented bicyclic partial structure, containing an additional pyrrolidine ring. Synoxazolidinone C exhibited both antibacterial and anticancer activities. 相似文献
955.
956.
Ulrik Hillaert Dr. Martijn Verdoes Bogdan I. Florea Dr. Anastasios Saragliadis Kim L. L. Habets Johan Kuiper Dr. Serge Van Calenbergh Prof. Ferry Ossendorp Dr. Gijsbert A. van der Marel Prof. Christoph Driessen Prof. Hermen S. Overkleeft Prof. 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2009,121(9):1657-1660
957.
David Schaubroeck Johan De Baets Sandra Van Vlierberghe André Van Calster 《Applied Surface Science》2009,255(21):8780-8787
The introduction of amine groups on the surface of dielectric resins improves the adhesion with electrochemically deposited metals. In this work, etched epoxy resin surfaces are modified with aliphatic amines via a two step wet chemical reaction approach. First, cyanuric chloride is introduced on the surface. Next, the remaining reactive sites of cyanuric chloride are used to couple an aliphatic polyamine. Both reaction steps are optimized by variation of reaction parameters such as concentration, chemicals, temperature and time. A detailed surface characterization after each reaction step is provided using following techniques: ATR-IR, SEM-EDS, XPS and AFM. 相似文献
958.
959.
There is strong evidence in favor of zonal flow suppression in the Ion-Temperature-Gradient (ITG) mode turbulence, specifically close to the linear stability threshold. The present Letter attempts to analytically calculate the effects of zonal flow suppression of the ITG turbulence by deriving a modified dispersion relation including the back-reaction of the zonal flows on the ITG turbulence based on the quasilinear theory. The results are manifested in a reduction of the linear growth rate and an increase in the effective linear ITG threshold. 相似文献
960.
Hessel L. Castricum Ashima Sah Jan A. J. Geenevasen Robert Kreiter Dave H. A. Blank Jaap F. Vente Johan E. ten Elshof 《Journal of Sol-Gel Science and Technology》2008,48(1-2):11-17
A procedure for the preparation of hybrid sols for the synthesis of organic–inorganic microporous materials and thin film membranes is reported. We describe silane reactivity and sol structure for acid-catalysed colloidal sols from mixtures of either tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES), or bis(triethoxysilyl)ethane (BTESE) and MTES. Early-stage hydrolysis and condensation rates of the individual silane precursors were followed with 29Si liquid NMR and structural characteristics of more developed sols were studied with Dynamic Light Scattering. Condensation was found to proceed at more or less similar rates for the different precursors. Homogeneously mixed hybrid colloids can therefore be formed from precursor mixtures. The conditions of preparation under which clear sols with low viscosity could be formed from BTESE/MTES were determined. These sols were synthesised at moderate water/silane and acid/silane ratios and could be applied for the coating of defect-free microporous membranes for molecular separations under hydrothermal conditions. 相似文献