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111.
112.
The synthesis of novel symmetrical liquid crystalline compounds based on 5-methyl-5-[2-(4-alkyloxyphenyl)-2-hydroxyethyl]-2,2-bipyridines is reported, together with some physical properties. Although the chelating head-groups are connected via a chiral sp3 carbon atom, all the materials are mesomorphic. Intermolecular hydrogen bonding between pyridino and hydroxy fragments in the mesophases is made apparent by FTIR spectroscopy. 相似文献
113.
ZDM – Mathematics Education - 相似文献
114.
Dr. Tarun Kumar Yan Yang Sirine Sghaier Dr. Yassir Zaid Dr. Xavier F. Le Goff Dr. Elodie Rousset Dr. Fabien Massicot Dr. Dominique Harakat Agathe Martinez Dr. Marc Taillefer Prof. Laurent Maron Prof. Jean-Bernard Behr Dr. Florian Jaroschik 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(12):4016-4021
The development of new fluorine-containing building blocks and their efficient synthetic access is currently a challenging research field. Herein, the highly regio- and stereoselective addition of a large range of aldehydes onto trifluoromethylated benzofulvenes was achieved using a simple La/I2/DIBAL-Cl system via a selective C−F bond activation process. This versatile methodology provided homodienyl alcohols bearing a terminal CF2-alkene with potential further applications, as shown by the dehydration to the first benzofulvenes carrying a difluorovinyl group. In addition, for certain electron-poor aldehydes, unprecedented ipso substitution of the CF3 group in a diene was observed, which, according to DFT studies, is related to the presence of the large, Lewis-acidic lanthanum metal. 相似文献
115.
Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Europium(III) DO3A as a Bimodal Imaging Probe
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Dr. Sophie Carron Dr. Maarten Bloemen Prof. Luce Vander Elst Prof. Sophie Laurent Prof. Thierry Verbiest Prof. Tatjana N. Parac‐Vogt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4521-4527
A new prototype consisting of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles decorated with europium(III) ions encapsulated in a DO3A organic scaffold was designed as a platform for further development of bimodal contrast agents for MRI and optical imaging. The USPIO nanoparticles act as negative MRI contrast agents, whereas the europium(III) ion is a luminophore that is suitable for use in optical imaging detection. The functionalized USPIO nanoparticles were characterized by TEM, DLS, XRD, FTIR, and TXRF analysis, and a full investigation of the relaxometric and optical properties was conducted. The typical luminescence emission of europium(III) was observed and the main red emission wavelength was found at 614 nm. The relaxometric study of these ultrasmall nanoparticles showed r2 values of 114.8 mm ?1Fes?1 at 60 MHz, which is nearly double the r2 relaxivity of Sinerem®. 相似文献
116.
117.
Laurent Jeannin Janos Sapi Elka Vassileva Pierre Renard Jean-Yves Laronze 《合成通讯》2013,43(9):1711-1719
Three methods have been proposed for the preparation of functionalized 1-oxo-1,2,3,4-tetrahydro-β-carboline-3 carboxylates (3) from which the “acylazide formation-Curtius rearrangement-acid catalyzed ring closure” sequence starling from hemi-ester hemi-acids (8) seemed to be quite general. 相似文献
118.
Dr. Yong Wu Dr. Shanshan Cao Dr. Iskander Douair Prof. Laurent Maron Prof. Xihe Bi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(19):5999-6006
The [2+1] cycloaddition reaction of a metal carbene with an alkene can produce important cyclopropane products for synthetic intermediates, materials, and pharmaceutical applications. However, this reaction is often accompanied by side reactions, such as coupling and self-coupling, so that the yield of the cyclopropanation product of non-silver transition-metal carbenes and hindered alkenes is generally lower than 50 %. To solve this problem, the addition of a low concentration of diazo compound (decomposition of sulfonyl hydrazones) to alkenes catalyzed by either CuOAc or PdCl2 was studied, but side reactions could still not be avoided. Interestingly, however, the yield of cyclopropanation products for such hindered alkenes were as high as 99 % with AgOTf as a catalyst. To explain this unexpected phenomenon, reaction pathways have been computed for four different catalysts by using DFT. By combining the results of these calculations with those obtained experimentally, it can be concluded that the efficiency of the silver catalyst is due to the barrierless concerted cycloaddition step and the kinetic inhibition of side reactions by a high concentration of alkene. 相似文献
119.
Davide Toniolo Aurélien R. Willauer Dr. Julie Andrez Yan Yang Dr. Rosario Scopelliti Prof. Laurent Maron Prof. Marinella Mazzanti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7831-7834
The activation of CS2 is of interest in a broad range of fields and, more particularly, in the context of creating new C−C bonds. The reaction of the dinuclear ytterbium(II) complex [Yb2L4], 1 , [L=(OtBu)3SiO−] with carbon disulfide led to the isolation of unprecedented reduction products. In particular, the crystallographic characterization of complex [Yb2L4(μ-C2S2)], 2 , provided the first example of an acetylenedithiolate ligand formed from metal reduction of CS2. Computational studies indicated that this unprecedented reactivity can be ascribed to the unusual binding mode of CS22− in the isolated “key intermediate” [Yb2L4(μ-CS2)], 3 , which results from the dinuclear nature of 1 . 相似文献
120.
Laurent François Joël Dupays Dmitry Davidenko Marc Massot 《Combustion Theory and Modelling》2020,24(5):775-809
We investigate a model of solid propellant combustion involving surface pyrolysis coupled to finite activation energy gas-phase combustion. Existence and uniqueness of a travelling wave solution are established by extending dynamical system tools classically used for premixed flames, dealing with the additional difficulty arising from the surface regression and pyrolysis. An efficient shooting method allows to solve the problem in phase space without resorting to space discretisation nor fixed-point Newton iterations. The results are compared to solutions from a CFD code developed at ONERA, assessing the efficiency and potential of the method, and the impact of the modelling assumptions is evaluated through parametric studies. 相似文献