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311.
A General Method for Preparing Bridged Organosilanes with Pendant Functional Groups and Functional Mesoporous Organosilicas
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Prof. Jana Hodačová Dr. Guillaume Toquer Dr. Xavier Cattoën Dr. Michel Wong Chi Man 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10371-10382
New organosilica precursors containing two triethoxysilyl groups suitable for the organosilica material formation through the sol‐gel process were designed and synthesised. These precursors display alkyne or azide groups for attaching targeted functional groups by copper‐catalysed azide–alkyne cycloaddition (CuAAC) and can be used for the preparation of functional organosilicas following two strategies: 1) the functional group is first appended by CuAAC under anhydrous conditions, then the functional material is prepared by the sol‐gel process; 2) the precursor is first subjected to the sol‐gel process, producing porous, clickable bridged silsesquioxanes or periodic mesoporous organosilicas (PMOs), then the desired functional groups are attached by means of CuAAC. Herein, we show the feasibility of both approaches. A series of bridged bis(triethoxysilane)s with different pending organic moieties was prepared, demonstrating the compatibility of the first approach with many functional groups. In particular, we demonstrate that organic functional molecules bearing only one derivatisation site can be used to produce bridged organosilanes and bridged silsesquioxanes. In the second approach, clickable PMOs and porous bridged silsesquioxanes were prepared from the alkyne‐ or azide‐containing precursors, and thereafter, functionalised with complementary model azide‐ or alkyne‐containing molecules. These results confirmed the potential of this approach as a general methodology for preparing functional organosilicas with high loadings of functional groups. Both approaches give rise to a wide range of new functional organosilica materials. 相似文献
312.
α‐Halogenoacetanilides as Hydrogen‐Bonding Organocatalysts that Activate Carbonyl Bonds: Fluorine versus Chlorine and Bromine
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Dr. Sylvain Koeller Dr. Coralie Thomas Dr. Fréderic Peruch Dr. Alain Deffieux Dr. Stéphane Massip Prof. Dr. Jean‐Michel Léger Dr. Jean‐Pierre Desvergne Prof. Dr. Anne Milet Dr. Brigitte Bibal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(10):2849-2859
α‐Halogenoacetanilides (X=F, Cl, Br) were examined as H‐bonding organocatalysts designed for the double activation of C?O bonds through NH and CH donor groups. Depending on the halide substituents, the double H‐bond involved a nonconventional C?H???O interaction with either a H?CXn (n=1–2, X=Cl, Br) or a H?CAr bond (X=F), as shown in the solid‐state crystal structures and by molecular modeling. In addition, the catalytic properties of α‐halogenoacetanilides were evaluated in the ring‐opening polymerization of lactide, in the presence of a tertiary amine as cocatalyst. The α‐dichloro‐ and α‐dibromoacetanilides containing electron‐deficient aromatic groups afforded the most attractive double H‐bonding properties towards C?O bonds, with a N?H???O???H?CX2 interaction. 相似文献
313.
Gold‐Catalyzed Diastereoselective Cycloisomerization of Alkylidene‐Cyclopropane‐Bearing 1,6‐Diynes
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Dr. Hongchao Zheng Laura L. Adduci Dr. Ryan J. Felix Prof. Dr. Michel R. Gagné 《Angewandte Chemie (International ed. in English)》2014,53(30):7904-7907
An unprecedented gold‐catalyzed diastereoselective cycloisomerization of 1,6‐diynes bearing an alkylidene cyclopropane moiety has been developed. This methodology enables rapid access to a variety of 1,2‐trimethylenenorbornanes, which are important building blocks in the preparations of abiotic and sesquiterpene core structures. 相似文献
314.
315.
Xavier Cattoën Achraf Noureddine Jonas Croissant Nirmalya Moitra Kristýna Bürglová Jana Hodačová Olivia de los Cobos Martine Lejeune Fabrice Rossignol Delphine Toulemon Sylvie Bégin-Colin Benoît P. Pichon Laurence Raehm Jean-Olivier Durand Michel Wong Chi Man 《Journal of Sol-Gel Science and Technology》2014,70(2):245-253
The combination of the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction with sol–gel processing enables the versatile preparation of sol–gel materials under different shapes with targeted functionalities through a diversity-oriented approach. In this account, the development of the CuAAC reaction under anhydrous conditions for the synthesis of sol–gel precursors and for the assembling of magnetic nanoparticles on self-assembled monolayers is related, as well as the use of the classical CuAAC methodologies for the functionalization of mesoporous silica nanoparticles and microdots arrays. Coupling CuAAC and Sol–Gel will result in simplified preparations of multifunctional materials with controlled morphologies. 相似文献
316.
Michel Petitjean 《Angewandte Chemie (International ed. in English)》2020,59(20):7650-7651
In this comment on the Essay entitled “Bad Language” by Dunitz I add new elements which enlighten the discussion. I hope that they contribute to suppress ambiguities and preconceived ideas about chirality. 相似文献
317.
Shusuke Sato Fumitaka Kudo Michel Rohmer Tadashi Eguchi 《Angewandte Chemie (International ed. in English)》2020,59(1):237-241
Adenosylhopane is a crucial intermediate in the biosynthesis of bacteriohopanepolyols, which are widespread prokaryotic membrane lipids. Herein, it is demonstrated that reconstituted HpnH, a putative radical S‐adenosyl‐l ‐methionine (SAM) enzyme, commonly encoded in the hopanoid biosynthetic gene cluster, converts diploptene into adenosylhopane in the presence of SAM, flavodoxin, flavodoxin reductase, and NADPH. NMR spectra of the enzymatic reaction product were identical to those of synthetic (22R)‐adenosylhopane, indicating that HpnH catalyzes stereoselective C?C formation between C29 of diploptene and C5′ of 5′‐deoxyadenosine. Further, the HpnH reaction in D2O‐containing buffer revealed that a D atom was incorporated at the C22 position of adenosylhopane. Based on these results, we propose a radical addition reaction mechanism catalyzed by HpnH for the formation of the C35 bacteriohopane skeleton. 相似文献
318.
Patrick Azavant Albert Lichanot Michel Rerat Cesare Pisani 《International journal of quantum chemistry》1996,58(4):419-429
Ab initio calculations of dynamic structure factors are performed with a methodology that requires the crystalline density matrix determined by the periodic Hartree-Fock CRYSTAL code. Amplitudes and orientations of the atomic vibrations are fixed by the mean-square displacements available in the literature. This method, which is here upgraded so as to satisfy normalization conditions, gives rise, for any temperature T, to a “dynamic” density matrix different from the static one. An application to the calculation of the dynamic structure factors of magnesium difluoride (MgF2), which has anisotropic mean-square displacement tensors, is proposed and compared with experiments at 298 K. © 1996 John Wiley & Sons, Inc. 相似文献
319.
Grald Monard Michel Loos Vincent Thry Kristofor Baka Jean-Louis Rivail 《International journal of quantum chemistry》1996,58(2):153-159
A coherent computational scheme on a very large molecule in which the subsystem that undergoes the most important electronic changes is treated by a semiempirical quantum chemical method, though the rest of the molecule is described by a classical force field, has been proposed recently. The continuity between the two subsystems is obtained by a strictly localized bond orbital, which is assumed to have transferable properties determined on model molecules. The computation of the forces acting on the atoms is now operating, giving rise to a hybrid classical quantum force field (CQFF ) which allows full energy minimization and modeling chemical changes in large biomolecules. As an illustrative example, we study the short hydrogen bonds and the proton-exchange process in the histidine-aspartic acid system of the catalytic triad of human neutrophil elastase. The CQFF approach reproduces the crystallographic data quite well, in opposition to a classical force field. The method also offers the possibility of switching off the electrostatic interaction between the quantum and the classical subsystems, allowing us to analyze the various components of the perturbation exerted by the macromolecule in the reactive part. Molecular dynamics confirm a fast proton exchange between the three possible energy wells. The method appears to be quite powerful and applicable to other cases of chemical interest such as surface reactivity of nonmetallic solids. © 1996 John Wiley & Sons, Inc. 相似文献
320.
Michel Boulouard Patrick Dallemagne Abdellah Alsaïdi Sylvain Rault 《Journal of heterocyclic chemistry》1996,33(6):1743-1749
Treatment of 3-(2-formyl-1H-pyrrol-1-yl)-2-thiophenecarboxamide by various nucleophiles like methyl ketones, amines, alcohols, thiols or acetates led to new 5,6-dihydro-4H-pyrrolo[1,2-a]thieno-[2,3-f][1,4]diazepines. 相似文献