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Charles Shearer Oriane Desaunay Stephen Zorc Alexis D. Richaud Shyam S. Samanta Nagalakshmi Jeedimalla Stéphane P. Roche 《Tetrahedron》2019,75(43):130606
4H-Pyrans (4H-Pys) and 1,4-dihydropyridines (1,4-DHPs) are important classes of heterocyclic scaffolds in medicinal chemistry. Herein, an indium(III)-catalyzed one-pot domino reaction for the synthesis of highly functionalized 4H-Pys, and a model of 1,4-DHP is reported. This alternative approach to the challenging Hantzsch 4-component reaction enables the synthesis of fused-tricyclic heterocycles, and the mechanistic studies underline the importance of an intercepted-Knoevenagel adduct to achieve higher chemoselectivity towards these types of unsymmetrical heterocycles. 相似文献
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Oriane Cérin Sophie Duquesne Gaëlle Fontaine Andreas RoosSerge Bourbigot 《Polymer Degradation and Stability》2011,96(10):1812-1820
The thermal degradation of vulcanized elastomeric poly(ethylene-co-vinyl acetate) (EVM) in inert and oxidative conditions was investigated. Based on the characterization of both condensed and gas phases during the thermal degradation it was possible to propose a reaction scheme of the EVM degradation. In addition, the determination of the kinetic parameters completed the chemical investigations. The thermo-oxidation of vulcanized EVM occurs in five steps, including the cleavage of some cross-linking bonds, the catalytic deacetylation forming polyenes and a charring step, followed by the decomposition and oxidation of the char. It appeared that the curing, and thus the cross-linking nodes, enhances the thermal stability of EVM by favouring the charring. On the other hand the pyrolysis of the polymer is quite not influenced by the vulcanization. 相似文献
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The East model is a one-dimensional, non-attractive interacting particle system with Glauber dynamics, in which a flip is prohibited at a site x if the right neighbour x+1 is occupied. Starting from a configuration entirely occupied on the left half-line, we prove a law of large numbers for the position of the left-most zero (the front), as well as ergodicity of the process seen from the front. For want of attractiveness, the one-dimensional shape theorem is not derived by the usual coupling arguments, but instead by quantifying the local relaxation to the non-equilibrium invariant measure for the process seen from the front. This is the first proof of a shape theorem for a kinetically constrained spin model. 相似文献
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Oriane Tascone Céline Roy Jean-Jacques Filippi Uwe J. Meierhenrich 《Analytical and bioanalytical chemistry》2014,406(4):971-980
Natural extracts used by the fragrance and cosmetics industries, namely essential oils, concretes, resinoids, and absolutes, are produced from natural raw materials. These are often cultivated by use of monoculture techniques that involve the use of different classes of xenobiotica, including pesticides. Because of these pesticides’ potential effect on public health and the environment, laws regarding permitted residual levels of pesticides used in cultivation of raw materials for fragrance and cosmetic products are expected to become stricter. The purpose of this review is to present and classify pesticides commonly used in the cultivation of these natural raw materials. We will summarize the most recent regulations, and discuss publications on detection of pesticides via chemical analysis of raw natural extracts. Advances in analytical chemistry for identification and quantification of pesticides will be presented, including both sample preparation and modern separation and detection techniques, and examples of the identification and quantification of individual pesticides present in natural extracts, for example essential oils, will be provided. Figure
The multidimensional gas chromatogramm depicts coelution of molecular ingredients of a rose essential oil spiked with an ethion pesticide 相似文献
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