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排序方式: 共有108条查询结果,搜索用时 46 毫秒
81.
82.
Sary Abou Derhamine Dr. Tetiana Krachko Dr. Nuno Monteiro Dr. Guillaume Pilet Dr. Johannes Schranck Dr. Anis Tlili Prof. Dr. Abderrahmane Amgoune 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19110-19115
The challenging nickel-catalyzed mono-α-arylation of acetone with aryl chlorides, pivalates, and carbamates has been achieved for the first time. A nickel/Josiphos-based catalytic system is shown to feature unique catalytic behavior, allowing the highly selective formation of the desired mono-α-arylated acetone. The developed methodology was applied to a variety of (hetero)aryl chlorides including biologically relevant derivatives. The methodology has been extended to the unprecedented coupling of acetone with phenol derivatives. Mechanistic studies allowed the isolation and characterization of key Ni0 and NiII catalytic intermediates. The Josiphos ligand is shown to play a key role in the stabilization of NiII intermediates to allow a Ni0/NiII catalytic pathway. Mechanistic understanding was then leveraged to improve the protocol using an air-stable NiII pre-catalyst. 相似文献
83.
Abderrahmane Semmeq Dr. Antonio Monari Dr. Michael Badawi Prof. Dr. Said Ouaskit 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(68):15525-15534
Thymine radiation-induced fragmentation is characterised by ring opening and the loss of HNCO/NCO. These pathways have been investigated using DFT calculations in the presence of zero, one and two water molecules. In addition to the already characterised stepwise fragmentation mechanism, we propose a novel concerted pathway reported here for the first time. We show that both the stepwise and concerted mechanisms are competitive with activation energies of 2.05 eV and 2.00 eV, respectively, in the gas phase. The effect of microhydration on these mechanisms are examined based on the most stable conformations found by an exploration of the potential energy surface performed by using DFT-based ab initio molecular dynamics. Microhydration is also accompanied by an increase in the activation energies, with respect to gas phase, amounting to 0.47 eV—an increase that is associated to a stabilising effect of water in agreement with recent experimental studies. However, we also point out that this effect is greatly dependent on the specific water arrangement around thymine and could be limited to only 0.13 eV for some configurations. 相似文献
84.
Radhouane Aounallah Salah Boulaaras Abderrahmane Zarai Bahri Cherif 《Mathematical Methods in the Applied Sciences》2020,43(12):7175-7193
The paper deals with the study of global existence of solutions and the general decay in a bounded domain for nonlinear wave equation with fractional derivative boundary condition by using the Lyaponov functional. Furthermore, the blow up of solutions with nonpositive initial energy combined with a positive initial energy is established. 相似文献
85.
PEG–PLGA copolymers bearing carboxylated side chains: Novel hydrogels with enhanced crosslinking via ionic interactions
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Sytze J. Buwalda Abderrahmane Amgoune Didier Bourissou 《Journal of polymer science. Part A, Polymer chemistry》2016,54(9):1222-1227
Novel water‐soluble amphiphilic block copolymers with pendant carboxylic acid groups are synthesized and used for the preparation of ionically crosslinked hydrogels. d ,l ‐Lactide (DLLA) and l ?3‐(2‐benzyloxycarbonyl)ethyl‐1,4‐dioxane‐2,5‐dione (BED) are copolymerized at different ratios via organo‐catalyzed ring‐opening polymerization using a hydroxyl‐terminated poly(ethylene glycol) (PEG–OH) macroinitiator. Dynamic light‐scattering experiments show that, at low concentrations, aqueous solutions of these PEG‐P(BED‐DLLA) copolymers form micelles and aggregates. At higher concentrations, thermo‐sensitive gels are obtained, exhibiting a reversible gel‐to‐sol transition upon a temperature increase. Ionic interactions between the COOH groups and metal ions (Cu2+ or Ca2+) are shown to significantly shift the gel–sol transition to higher temperatures. Thus, the introduction of COOH groups significantly enhances the water solubility of the amphiphilic PEG–polyester copolymer and allows additional crosslinking interactions to form functionalized hydrogels with improved physical properties, making this new class of hydrogels interesting for various applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1222–1227 相似文献
86.
Abderrahmane Mezroua Kamel Khimeche Michel H. Lefebvre Mokhtar Benziane Djalal Trache 《Journal of Thermal Analysis and Calorimetry》2014,116(1):279-286
The influence of porous ammonium perchlorate (POAP) on the thermomechanical and combustion behavior of solid rocket propellants based on polyvinylchloride binder has been investigated. Differential scanning calorimetry, differential thermogravimetry, dynamic mechanical thermal analysis, and scanning electronic microscopy measurements were used for thermomechanical and thermal decomposition properties assessment. The results obtained indicate that lower glass transitions of the propellants and catalytic effect of combustion are obtained with POAP. 相似文献
87.
Maximilian Joost Pauline Gualco Yannick Coppel Karinne Miqueu Christos E. Kefalidis Laurent Maron Abderrahmane Amgoune Didier Bourissou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(3):766-770
Oxidative addition plays a major role in transition‐metal catalysis, but this elementary step remains very elusive in gold chemistry. It is now revealed that in the presence of GaCl3, phosphine gold chlorides promote the oxidative addition of disilanes at low temperature. The ensuing bis(silyl) gold(III) complexes were characterized by quantitative 31P and 29Si NMR spectroscopy. Their structures (distorted Y shape) and the reaction profile of σ(Si Si) bond activation were analyzed by DFT calculations. These results provide evidence for the intermolecular oxidative addition of σ(Si Si) bonds to gold and open promising perspectives for the development of new gold‐catalyzed redox transformations. 相似文献
88.
Feriel Rekhroukh Rémy Brousses Dr. Abderrahmane Amgoune Dr. Didier Bourissou 《Angewandte Chemie (International ed. in English)》2015,54(4):1266-1269
Migratory insertion of alkenes into gold–carbon bonds, a fundamental yet unprecedented organometallic transformation, has been investigated from a discrete (P,C) cyclometalated gold(III) dimethyl complex. Methide abstraction by B(C6F5)3 is shown to generate a highly reactive cationic AuIII complex that evolves spontaneously by C6F5 transfer from boron. In the presence of norbornene, migratory insertion into the Au? C bond proceeds readily. The resulting norbornyl complex is efficiently trapped with pyridines or chloride to give stable four‐coordinate adducts. 相似文献
89.
Hamid Ait Abderrahmane Frederick Paquet Hoi Dick Ng 《Combustion Theory and Modelling》2013,17(2):205-225
The dynamical behaviour of one-dimensional pulsating detonations was investigated in detail, with the aid of nonlinear theory tools such as phase plots and correlation dimension. The period-doubling cascade, as routes to deterministic chaos, is depicted through the transformations of the shapes of the attractors. Using a correlation dimension method, the dimension of the attractors is determined and we show that the chaos within a one-dimensional pulsating detonation is deterministic. 相似文献
90.
In this study, we build a kernel estimate of the transition operator density for some discrete time continuous states Markov processes which satisfy some general conditions. Assumptions are not restrictive and results can be used on transition Markov operator, viewed as an endomorphism on Lp, p∈[1,∞[, as well as on its adjoint. The main result deals with convergence rate of built kernel estimate. To cite this article: A. Laksaci, A. Yousfate, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 1035–1038. 相似文献