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141.
Z Amara E Drège C Troufflard P Retailleau D Joseph 《Organic & biomolecular chemistry》2012,10(35):7148-7157
Novel 2,5-meso-pyrrolidines have been straightforwardly synthesized from readily available symmetrical double Michael acceptors. The key step rested on an aza-Michael addition of primary alkylamines to bis-enones. Competitive Rauhut-Currier and aza-Michael reactions have been highlighted in protic solvent. Ultrasound activation associated with solvent-free conditions led to the expected pyrrolidines in quantitative yields and excellent stereoselectivities. The optimized conditions have been extended to the sonochemical synthesis of pyrrolidine Lobelia alkaloids analogues in short sequences. 相似文献
142.
Anh Ngoc Ngo Khadija El Kassimi Zacharias Amara Emmanuelle Drège Delphine Joseph 《Tetrahedron letters》2012,53(26):3296-3300
To reach densely functionalized 1-azabicyclo[3.3.1]nonane frameworks synthesis, a stereocontrolled bridging Michael addition involving an unexplored C-5/C-6 disconnection strategy was studied. 1-Azabicyclo[3.3.1]nonane scaffolds have been diastereoselectively elaborated in fairly good yields by two concise pathways implying pyrrolidine derivative organocatalyst or enantiopure 1-phenylethylamine. 相似文献
143.
Ojo WS Jacob K Despagnet-Ayoub E Muñoz BK Gonell S Vendier L Nguyen VH Etienne M 《Inorganic chemistry》2012,51(5):2893-2901
The synthesis and characterization (mainly by (19)F NMR and X-ray diffraction) of highly fluorinated aryl-4,5,6,7-tetrafluoroindazoles and their corresponding thallium hydrotris(indazolyl)borate complexes are reported [aryl = phenyl, pentafluorophenyl, 3,5-dimethylphenyl, 3,5-bis(trifluoromethyl)phenyl]. Thanks to N-H···N hydrogen bonds, the indazoles crystallize as dimers that pack differently depending on the nature of the aryl group. The thallium hydrotris(indazolyl)borate complexes Tl[Fn-Tp(4Bo,3aryl)] resulting from the reaction of aryl-4,5,6,7-tetrafluoroindazoles [aryl = phenyl, 3,5-dimethylphenyl, 3,5-bis(trifluoromethyl)phenyl] with thallium borohydride adopt overall C(3v) symmetry with the indazolyl groups bound to boron via their N-1 nitrogen in a conventional manner. When the perfluorinated pentaphenyl-4,5,6,7-tetrafluoroindazole is reacted with thallium borohydride, a single regioisomer of C(s) symmetry having one indazolyl ring bound to boron via its N-2 nitrogen, TlHB(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-1-yl)(2)(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl) Tl[F27-Tp((4Bo,3C6F5)*)], is obtained for the first time. Surprisingly, the perfluorinated dihydrobis(indazolyl)borate complex Tl[F(18)-Bp(3Bo,3C6F5)], an intermediate on the way to the hydrotris(indazolyl)borate complex, has C(s) symmetry with two indazolyl rings bound to boron via N-2. The distortion of the coordination sphere around Tl and the arrangement of the complexes in the crystal are discussed. 相似文献
144.
Nuss H Claiser N Pillet S Lugan N Despagnet-Ayoub E Etienne M Lecomte C 《Dalton transactions (Cambridge, England : 2003)》2012,41(22):6598-6601
A comparison of the topology of the experimental electron density, as revealed by high resolution X-ray diffraction, is provided for two prototypal transition metal alkyne complexes where the alkyne formally behaves as a 2 or 4e(-) donor. A higher value of the electron density ρ(r)(bcp) at the M(T)···C bond critical point (bcp), a lower value of ρ(r)(bcp) at the coordinated C≡C bcp, outwardly bent MC bond paths and a close to zero ellipticity for the C[triple bond, length as m-dash]C bond constitute the topological signature of a 4e(-) donor alkyne ligand. 相似文献
145.
Julien Férec Emmanuelle Abisset-Chavanne Gilles Ausias Francisco Chinesta 《Rheologica Acta》2014,53(5-6):445-456
Recently, Férec et al. (2009a) proposed a model for nondilute rod-like suspensions, where particle interactions are taking into account via a micromechanical approach. The derived governing equation used the well-known second- and fourth-order orientation tensors (a 2 and a 4 ) and novel second- and fourth-order interaction tensors (b 2 and b 4 ). To completely close the model, it is necessary to express a 4 , b 2 , and b 4 in terms of a 2 . This paper gives the general framework to elaborate these new relations. Firstly, approximations for b 2 are developed based on linear combinations of a 2 and a 4 . Moreover, a new closure approximation is also derived for b 4 , based on the orthotropic fitted closure approach. Unknown parameters are determined by a least-square fitting technique with assumed exact solutions constructed from the probability distribution function (PDF). As numerical solutions for the PDF are difficult to obtain given the nonlinearity of the problem, a combination of steady state solutions is used to generate PDF designed to cover uniformly the entire domain of possible orientations. All these proposed approximations are tested against the particle-based simulations in a variety of flow fields. Improvements of the different approximations are observed, and the couple iORW-CO4P3 gives efficient results. 相似文献
146.
Emmanuelle Anceaume François Castella Romaric Ludinard Bruno Sericola 《Methodology and Computing in Applied Probability》2013,15(2):305-332
We consider the behavior of a stochastic system composed of several identically distributed, but non independent, discrete-time absorbing Markov chains competing at each instant for a transition. The competition consists in determining at each instant, using a given probability distribution, the only Markov chain allowed to make a transition. We analyze the first time at which one of the Markov chains reaches its absorbing state. We obtain its distribution and its expectation and we propose an algorithm to compute these quantities. We also exhibit the asymptotic behavior of the system when the number of Markov chains goes to infinity. Actually, this problem comes from the analysis of large-scale distributed systems and we show how our results apply to this domain. 相似文献
147.
Bis(2-sulfanylethyl)amido (SEA) side-chain derivatives of aspartic and glutamic acids enable the synthesis of tail-to-side chain cyclic or branched peptides using standard Fmoc-SPPS followed by SEA native peptide ligation. 相似文献
148.
Emmanuelle Declercq Alain Forestier† Jean-Marc Hérard‡ Xavier Louis¶ Gérard Poissant§ 《International Journal of Computational Fluid Dynamics》2013,27(3):169-182
We focus on the computation of a hyperbolic system describing a multicomponent turbulent flow for isentropic gases, using an exact Riemann solver. This method is very robust, but costly. Thus, we introduce two approximate upwinding schemes: a Godunov scheme called VFRoe and a Rusanov scheme. The Rusanov scheme always ensures positive values for mass, concentration and turbulent kinetic energy, but generates less accurate results. We show some one- and two-dimensional computations and compare these three resolution methods. 相似文献
149.
Wolfgang Jahnke Guido Bold Andreas L. Marzinzik Silvio Ofner Xavier Pell Simona Cotesta Emmanuelle Bourgier Sylvie Lehmann Chrystelle Henry Ren Hemmig Frdric Stauffer J. Constanze D. Hartwieg Jonathan R. Green Jean‐Michel Rondeau 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(48):14783-14787
150.
Enrique Nadal Emmanuelle Abisset-Chavanne Elias Cueto Francisco Chinesta 《Comptes Rendus Mecanique》2018,346(7):581-589
Even if the diffusion equation has been widely used in physics and engineering, and its physical content is well understood, some variants of it escape fully physical understanding. In particular, anormal diffusion appears in the so-called fractional diffusion equation, whose main particularity is its non-local behavior, whose physical interpretation represents the main part of the present work. 相似文献