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101.
Christine Gravier-Pelletier Jacques Dumas Yves Le Merrer Jean-Claude Depezay 《Journal of carbohydrate chemistry》2013,32(8):969-998
AbstractEnantiomerically pure α-hydroxy, α,β-dihydroxy and α,β-epoxyaldehydes, useful building blocks for the synthesis of acyclic oxygenated fatty acids metabolites, were synthetized via epoxybutanediol acetonide starting from the commercially available L-ascorbic and D-isoascorbic acids. 相似文献
102.
Christine Bressy Minh Ngoc NGuyen Brigitte Tanguy Van Giang Ngo André Margaillan 《Polymer Degradation and Stability》2010,95(7):1260-9117
Polymers containing hydrolytically labile trialkylsilyl ester side groups were synthesised via a conventional and a controlled radical polymerization. The trialkylsilyl methacrylate monomer unit was chosen for its capacity to hydrolyse into basic, acid or sea water varying the hydrophilic character of the resulting polymer backbone with time. The hydrolysis or saponification reaction of the ester bond of the trialkylsilyl methacrylate was monitored through a 1H NMR study showing the formation of siloxane side-products. Several copolymers and polymer blends were prepared as matrixes for controlled erodible systems. Their capacity to hydrolyse was demonstrated through SEM investigations with selective dissolution of free films containing hydrolysable copolymers and PMMA blends. Well-defined random and diblock copolymers with methyl methacrylate were investigated to show the effect of the microstructure on the erosion properties of the corresponding coatings. Poly(methyl methacrylate-b-tert-butyldimethylsilyl methacrylate) diblock copolymers synthesised through the RAFT process showed a better control of the erosion with a constant erosion rate over a long-time service in sea water at pH = 8.2. In addition, experiments showed that the erosion rate could be modulated by varying the molar proportion of hydrolysable side groups onto the copolymer backbone and the weight amount of copolymers mixed with PMMA in toluene solution. 相似文献
103.
Asad Ali Munawar Hussain Imran Malik Alexander Villinger Christine Fischer Peter Langer 《Helvetica chimica acta》2010,93(9):1764-1772
Double Heck cross‐coupling reactions of 2,3‐ and 3,5‐dibromopyridine with various alkenes afforded the corresponding novel di(alkenyl)pyridines. The Heck reaction of 2,5‐dibromopyridine unexpectedly afforded 5,5′‐di(alkenyl)‐2,2′‐bipyridines by palladium‐catalyzed dimerization to give 5,5′‐dibromo‐2,2′‐bipyridine and subsequent twofold Heck reaction. 相似文献
104.
105.
Remigiusz Zurawinski Christine Lepetit Yves Canac Laure Vendier Marian Mikolajczyk Remi Chauvin 《Tetrahedron: Asymmetry》2010,21(13-14):1777-1787
The synthesis and structure of Rh(I) and Pd(II) complexes of chiral P,C-chelating phosphino-(α-sulfinylalkyl)phosphonium ylide ligands with a trisubstituted asymmetric ylidic center P+–C1R(S1(O)p-Tol)–M (R = alkyl group) have been investigated, and compared to those of the analogous disubstituted ylide complexes (R = H). Reaction of the ethyl onium ylide of o-bis(diphenylphosphino)benzene with (?)-menthyl-(S)-p-tolylsulfinate afforded the corresponding racemic erythro phosphino-(α-sulfinylethyl)phosphonium in 90% de (R = Me). The racemization process is interpreted by a Berry-like pseudorotation mechanism driven by the steric repulsion between the α-methyl substituent and the bulky menthyloxy S-substituent or sulfur lone pair in the intermediate ylide-sulfinyl adduct. The ylide of phosphino-(α-sulfinylethyl)phosphonium reacts with [Rh(cod)2][PF6] and PdCl2(MeCN)2 to afford the corresponding P,C1-chelated threo-Rh(I) and erythro-Pd(II) mononuclear complexes in 70% yield and total diastereoselectivity. These respective complexes act as efficient catalytic precursors for the hydrogenation of (Z)-α-acetamidocinnamic acid and allylic substitution of 3-acetoxy-1,3-diphenyl-1-propene with sodium dimethyl malonate. The bonding features of the erythro-Pd(II) complex exhibiting a sulfinyl O?Pd interaction are studied theoretically at the DFT level using ELF and MESP analyses. The η2-P,C haptomeric form of the ylide ligand is estimated to compete at 19% with the η1-C haptomeric form dominating at 81%. 相似文献
106.
107.
Cuauhtémoc Pozos vázquez Russell Tayouo Christine Joly‐Duhamel Bernard Boutevin 《Journal of polymer science. Part A, Polymer chemistry》2010,48(10):2123-2134
The synthesis and characterization of poly(dimethylsiloxanes) bearing maleimides end‐groups (PDMSM) were carried out through imidization of maleic anhydride with three poly(dimethylsiloxanes) diamines of different molecular weights. Self‐photopolymerization of PDMSM was studied by Real‐Time Fourier Transform infrared spectroscopy (RT‐FTIR) and was possible even without photoinitiator (Darocur 1173). The reaction was found to proceed within seconds upon exposure to ultraviolet (UV) radiation to generate highly crosslinked polymer networks. The results indicated that these polymerizations were less sensitive to oxygen inhibition than the radical processes carried out on conventional UV‐curable acrylate resins. The thermal and mechanical properties of these resulting materials were studied starting from PDMS precursors with different molecular weights. These materials exhibit a low glass transition temperature (100 °C) and a high degradation temperature (400 °C) depending on the density of crosslinking points. These PDMSM are suitable as hydrophobic additives in a coating formulation based on a UV cured polypropylene glycol bismaleimide. Only a very small amount of silicone additives (0.3 wt %) is needed to change the wettability on the surface of the films. The migration of the additive was clearly shown before irradiation by scanning electron microscopy EDX and surface energy measurements. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2123–2134, 2010 相似文献
108.
Muhammad Mumtaz Christine Labrugère Eric Cloutet Henri Cramail 《Journal of polymer science. Part A, Polymer chemistry》2010,48(17):3841-3855
The synthesis by oxidative polymerization of well‐defined poly(3,4‐ethylenedioxythiophene) (PEDOT) nano‐objects in the presence of modified and unmodified poly(N‐vinylpyrrolidone)‐based copolymers used as stabilizers in aqueous media is reported. Ammonium persulfate or a mixture of ammonium persulfate with CuCl2 or CuBr2 was used as oxidants. The effects of several parameters such as the molar mass and the concentration of the stabilizer as well as the nature of the oxidants on the size, morphology, and the conductivity of the PEDOT particles have been investigated. The distribution of the reactive moieties along the copolymer stabilizer backbone was shown to be crucial to get well‐defined PEDOT nano‐objects. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3841–3855, 2010 相似文献
109.
Christine Bernardi Driss Yakoubi 《Mathematical Methods in the Applied Sciences》2016,39(18):5192-5202
We are interested in a mixed reaction diffusion system describing the organic pollution in stream‐waters. In this work, we propose a mixed‐variational formulation and recall its well‐posedness. Next, we consider a spectral discretization of this problem and establish nearly optimal error estimates. Numerical experiments confirm the interest of this approach. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
110.
Development and Validation of the Mathematics Teachers' Beliefs About English Language Learners Survey (MTBELL) 下载免费PDF全文
Given the increasing number of English Language Learners (ELLs) in secondary mathematics classrooms, it is imperative that mathematics teacher educators develop measures for determining how and why secondary mathematics teachers (SMTs) understand and respond instructionally to these students. This paper reports on the initial development and validation of the Mathematics Teachers' Beliefs about English Language Learners survey, an instrument that measures SMTs beliefs, attitudes, knowledge base, and instructional practices in relation to meeting the academic and language needs of ELLs. Through piloting processes, the instrument was refined for a research study through which reliability and validity were established. The five constructs identified from exploratory factor analysis illustrate perceived opportunities and barriers in meeting ELLs' academic and language needs among SMTs. This article features a Research to Practice Companion Article . Please click on the supporting information link below to access. 相似文献