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41.
Efficient Synthesis of Differentiated syn‐1,2‐Diol Derivatives by Asymmetric Transfer Hydrogenation–Dynamic Kinetic Resolution of α‐Alkoxy‐Substituted β‐Ketoesters
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Dr. Laure Monnereau Dr. Damien Cartigny Dr. Michelangelo Scalone Dr. Tahar Ayad Dr. Virginie Ratovelomanana‐Vidal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11799-11806
Asymmetric transfer hydrogenation was applied to a wide range of racemic aryl α‐alkoxy‐β‐ketoesters in the presence of well‐defined, commercially available, chiral catalyst RuII–(N‐p‐toluenesulfonyl‐1,2‐diphenylethylenediamine) and a 5:2 mixture of formic acid and triethylamine as the hydrogen source. Under these conditions, dynamic kinetic resolution was efficiently promoted to provide the corresponding syn α‐alkoxy‐β‐hydroxyesters derived from substituted aromatic and heteroaromatic aldehydes with a high level of diastereoselectivity (diastereomeric ratio (d.r.)>99:1) and an almost perfect enantioselectivity (enantiomeric excess (ee)>99 %). Additionally, after extensive screening of the reaction conditions, the use of RuII‐ and RhIII‐tethered precatalysts extended this process to more‐challenging substrates that bore alkenyl‐, alkynyl‐, and alkyl substituents to provide the corresponding syn α‐alkoxy‐β‐hydroxyesters with excellent enantiocontrol (up to 99 % ee) and good to perfect diastereocontrol (d.r.>99:1). Lastly, the synthetic utility of the present protocol was demonstrated by application to the asymmetric synthesis of chiral ester ethyl (2S)‐2‐ethoxy‐3‐(4‐hydroxyphenyl)‐propanoate, which is an important pharmacophore in a number of peroxisome proliferator‐activated receptor α/γ dual agonist advanced drug candidates used for the treatment of type‐II diabetes. 相似文献
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Omar Kammoun Nouha Loulou Walid Rekik Houcine Na?li Tahar Mhiri Thierry Bataille 《Journal of chemical crystallography》2012,42(2):103-110
Abstract
The new hybrid material, cobalt selenate templated by 1,4-diazabicyclo[2.2.2]octane (abbreviated dabco), has been synthesised by the slow evaporation method at room temperature. Its crystal structure was investigated using single crystal X-ray diffraction data. It crystallises in the monoclinic system (space group P21/c) with the following unit-cell parameters: a = 12.9169(2) ?, b = 11.9101(2) ?, c = 12.4951(2) ?, β = 108.484(1)°, V = 1823.10(5) ?3 and Z = 4. The supramolecular structure of (C6H14N2)[Co(H2O)6](SeO4)2 consists of isolated [Co(H2O)]2+ and (C6H14N2)2+ cations and (SeO4)2− anions linked together by three dimensional hydrogen-bond network. The infrared spectroscopy confirmed the presence of these different entities. The thermal behaviour of the precursor, studied by thermodiffractometry and thermogravimetric analyses, indicates that its decomposition proceeds through three stages giving rise to the cobalt oxide. 相似文献44.
Ghazi Kassab Dominique Petit Jean-Pierre Korb Tahar Tajouri Pierre Levitz 《Comptes Rendus Chimie》2010,13(4):394-398
Reversed micelles and water in oil micro-emulsions can be used to solubilize biopolymers and genetic materials allowing analyzing their properties in a confined geometry. Nuclear Magnetic Resonance Dispersion (NMRD) provides a powerful and a noninvasive experimental technique to probe the long-term dynamics of these confined systems. However, the first step is to analyze and understand the slow dynamics of water inside these micro-reactors without any guest molecule. This is the aim of this presentation. Experimental results have been obtained for deuteron 2H NMRD of water confined in reverse micelles of bis (2-ethylhexyl) sodium sulfosuccinate (AOT) dispersed in isooctane C8H18. The water content is expressed as the molar ratio W0 = [Water]/[AOT]. The radius of the spherical reversed micelles, Rm, increases almost linearly with W0. In our case, W0 is chosen in the range 20 ≤ W0 ≤ 50 (35 ≤ Rm ≤ 80 Å). The frequency dependence for the spin-lattice relaxation rate R1(ω) exhibits two regimes, for all W0 values: a plateau at low frequency, proportional to 1/Rm, followed by the beginning of an algebraic decay. These experimental observations are discussed and compared to a numerical simulation of the intermittent Brownian diffusion of a water molecule inside a rotating reverse micelle. The possibility to probe some properties of the confinement, such as the localisation time on the sulfonated palisade and/or the water self-diffusion inside the water pool is emphasised. 相似文献
45.
Guettari Moez Ajroudi Lilia Jouini Karima Tajouri Tahar Herráez José V. 《Journal of solution chemistry》2014,43(8):1414-1420
Journal of Solution Chemistry - The aim of this work is to develop a simple theory to study the effect of the addition of an impurity on the interaction between unlike molecules in mixed liquids.... 相似文献
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The Mathematical Collection of the Polish Virtual Library of Science is an open access repository of Polish mathematical papers.
The work on this project started 8 years ago and at present 12,500 articles and 54 books are available in the collection.
Statistical analysis of use of the webpage clearly shows the advantages of online publishing of scientific works. Currently,
we are preparing the migration of the Mathematical Collection to a new platform for electronic publishing called YADDA. This
platform, developed at ICM UW, offers an excellent solution for Open Access paradigm of content publishing, and will ensure
improved access to the Mathematical Collection. 相似文献
48.
Mohamed Tahar Kadaoui Abbassi Oldřich Kowalski 《Annals of Global Analysis and Geometry》2010,38(1):11-20
We prove that there is always a locally homogeneous Einstein g-natural metric on the unit tangent sphere bundle over any Riemannian space of constant positive sectional curvature. Furthermore,
using the (1–1) correspondence between all SO(m + 1)-invariant homogeneous metrics on the Stiefel manifold
V2 \mathbbRm+1 = SO(m+1)/SO(m-1){V_2 \mathbb{R}^{m+1} = {{SO}}(m+1)/{{SO}}(m-1)} and all g-natural metrics on T1 Sm{T_1 S^m} (Abbassi and Kowalski, Diff. Geom. Appl., to appear [7]), we reconstruct, by purely local procedure, the same well-known
unique SO(m + 1)-invariant homogeneous Einstein metric on
V2 \mathbbRm+1, m 1 3{V_2 \mathbb{R}^{m+1}, m \neq 3}, initially constructed by Kobayashi. 相似文献
49.
Sébastien Prévost Sébastien Gauthier Maria Cristina Caño de Andrade Céline Mordant Ali Rhida Touati Philippe Lesot Philippe Savignac Tahar Ayad Phannarath Phansavath Virginie Ratovelomanana-Vidal Jean-Pierre Genêt 《Tetrahedron: Asymmetry》2010,21(11-12):1436-1446
The dynamic kinetic resolution (DKR) of racemic α-chloro β-ketoesters and α-chloro β-ketophosphonates through ruthenium-mediated asymmetric hydrogenation is reported. The corresponding α-chloro β-hydroxyesters and α-chloro β-hydroxyphosphonates were obtained in good to high enantio- and diastereomeric excesses using, in particular, the atropisomeric ligand DIFLUORPHOS. This methodology allowed an efficient preparation of the anti phenylisoserine side chain of Taxotere® which has been used for the hemisynthesis of the cancer therapeutic agent itself. In addition, 13C NMR in chiral oriented solvents was used to investigate the DKR effect. 相似文献
50.
Crystal structure and ionic conductivity of lithium gadolinium polyphosphate, LiGd(PO3)4, were investigated. Single crystals of the title compound have been grown by a flux technique. The structure of this novel phosphate was determined by single crystal X-ray diffraction techniques. LiGd(PO3)4 is isotypic with LiNd(PO3)4. It crystallizes in the monoclinic space group C2/c with the unit cell parameters a=16.386(2), b=7.059(3), c=9.677(2) Å, β=126.12(1)°, V=904.2(4) Å3 and Z=4. The structure refined from 967 independent reflections leads to R1=0.0167 and wR2=0.0458. The lattice of LiGd(PO3)4 is built of twisted zig-zag chains running along with the b direction and make up of PO4 tetrahedra sharing two corners, connected to the GdO8 and LiO4 polyhedra by common oxygen atoms to form a three-dimensional framework. Differential and thermogravimetric thermal analysis are given. The thermal curve of this compound was recorded and interpreted in agreement with impedance measurements. The ionic conductivity has been measured on pellet of the polycrystalline powder and evaluated as a function of temperature. This phase showed the conductivity of 2×10−6 and 2×10−4 Ω−1 cm−1 at 682 and 951 K, respectively. 相似文献