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1.
The direct coupling of aryl halides with thiophene would be a considerable advantage for sustainable development because of only HBr associated with a base as by-product is formed and the number of steps to prepare these compounds is less than in more classical coupling reactions. We observed that through the use of only 0.2 mol% Pd(OAc)2 as the catalyst, a range of aryl bromides undergoes coupling via a C-H bond activation/functionalization reaction with thiophene to give 2-arylated thiophenes in good yields. In most cases, only traces of polyarylated thiophenes were detected when a large excess of thiophene was employed. This air-stable catalyst can be used with a wide variety of aryl bromides. 相似文献
2.
Souhila BensaidNouria Laidaoui Douniazad El AbedSoufi Kacimi Henri Doucet 《Tetrahedron letters》2011,52(12):1383-1387
The palladium-catalysed direct coupling of aryl halides with heteroaromatics in greener solvents than DMF or DMAc, which are often employed for such couplings, would be a considerable advantage for both industrial application and sustainable development. We observed that a range of aryl bromides undergoe coupling via C-H bond activation/functionalisation reaction of thiazoles or imidazoles in moderate to good yields using pentan-1-ol or 3-methylbutan-1-ol as the solvents. Pentan-1-ol and 3-methylbutan-1-ol are less toxic than DMF or DMAc, moreover they are bioresources as they can be obtained by fermentation. Therefore, these reaction conditions are certainly more eco-compatible than those generally employed for such couplings. 相似文献
3.
Several flavonols have been transformed upon treatment by Trametes versicolor laccase. Most of the major oxidation products have been isolated by HPLC as pure compounds and their structures have been, when possible, investigated through spectral methods (HPLC-MS and NMR). The results are coherent with the predominance of a dismutation process, leading to cation formation, over direct radical-radical coupling. 相似文献
4.
Flavonoids: hemisynthesis, reactivity, characterization and free radical scavenging activity 总被引:1,自引:0,他引:1
Phenolic compounds form one of the main classes of secondary metabolites. They display a large range of structures and they are responsible for the major organoleptic characteristics of plant-derived-foods and beverages, particularly color and taste properties and they also contribute to the nutritional qualities of fruits and vegetables. Phenolic compounds are also highly unstable compounds which undergo numerous enzymatic and chemical reactions during postharvest food storage and processing thus adding to the complexity of plant polyphenol composition. Among these compounds flavonoids constitute one of the most ubiquitous groups of all plant phenolics. Owing to their importance in food organoleptic properties and in human health, a better understanding of their structures, their reactivity and chemical properties in addition to the mechanisms generating them appears essential to predict and control food quality. The purpose of this work is an overview of our findings concerning the hemisynthesis, the reactivity and the enzymatic oxidation of some flavonoids and shed light on the mechanisms involved in some of these processes and the structures of the resulting products. The free radical scavenging activity of some of the synthesized compounds is also presented and a structure-activity relationship is discussed. The first part of this review concerns the synthesis and structural characterization of modified monomeric flavanols. The use of these compounds as precursor for the preparation of natural and modified dimeric procyanidin derivatives was then explored through different coupling reactions. The full characterization of the synthesized compounds was achieved by concerted use of NMR and ESI-MS techniques. The free radical scavenging activity of some of the synthesized compounds was investigated. The second part of this review concerns the enzymatic oxidation of several flavonols by Trametes versicolor laccase. Most of the major oxidation products have been isolated as pure compounds and their structures unambiguously established through spectroscopic methods. Correlation between the structure of the oxidation product and the substitution pattern of the starting materials allows mechanistic features of this transformation to be elucidated. 相似文献
5.
Boudjellal Loubna Belhadi Akila Brahimi Razika Boumaza Souhila Trari Mouhamed 《Journal of Solid State Electrochemistry》2020,24(2):357-364
Journal of Solid State Electrochemistry - The ilmenite CoTiO3 was synthesized by chemical route, and the decomposition of nitrates was followed by thermal analysis (TG/DTA). The intermediate... 相似文献
6.
In this work, we have prepared electrochemically and studied a composite materials based on an organic conducting polymer, polyaniline (PANI), in which inorganic semiconductor titanium dioxide (TiO2) particles were incorporated with different concentrations. The polyaniline/titanium dioxide composite material which had been deposited by cyclic voltammetry on substrates of indium tin oxide was then characterized. The cyclic voltammogram showed one redox couple characteristic of the oxidation and reduction states of the produced composite material. The impedance spectroscopy study showed that the resistance of the film increases with the TiO2 cocntent incorporated in the polymer. The incorporation of TiO2 in PANI covering the surfaces was confirmed by the scanning electron microscopy and the energy dispersive X-ray analysis. The morphological analysis of the film surfaces showed that the TiO2 nanoparticle increased the roughness. These observations allow to consider a new approach to improve the physicochemical properties of the interface between the organic and inorganic material. The I–V characteristics of PANI+TiO2 heterostructure diode showed the nonlinear nature of the I–V curve of PANI+TiO2 heterostructure device. 相似文献
7.
Amel Boudjemaa Aline Auroux Souhila Boumaza Mohamed Trari Ouiza Cherifi Rabah Bouarab 《Reaction Kinetics and Catalysis Letters》2009,98(2):319-325
The effect of the structure of the achiral primary amine additive on the enantioselective heterogeneous catalytic hydrogenation
of (E)-2-methyl-2-butenoic acid over cinchonidine modified Pd/Al2O3 was studied. It was found that a variety of amines increase the enantioselectivity, which was always accompanied by decrease
in the initial rate of the hydrogenations. Based on these results, the participation of the amine additive in the formation
of the intermediate complex responsible for enantioselection was suggested. A decrease in the reaction temperature resulted
in further increase in the optical purity of the product up to 67%, the highest value reported in the hydrogenation of unsaturated
aliphatic acids in this heterogeneous catalytic system so far. 相似文献
8.
Design and Synthesis of New Hybrid Molecules That Activate the Transcription Factor Nrf2 and Simultaneously Release Carbon Monoxide 下载免费PDF全文
Dr. Jayne Louise Wilson Sarah Fayad Kobeissi Dr. Souhila Oudir Dr. Benjamin Haas Dr. Brian Michel Prof. Jean‐Luc Dubois Randé Dr. Anthony Ollivier Prof. Thierry Martens Dr. Michael Rivard Dr. Roberto Motterlini Dr. Roberta Foresti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(45):14698-14704
9.
The regioselective 5-arylation of a variety of heteroaromatics with functionalised pyridyl bromides using palladium catalyst gives a simple access to functionalised heteroarylated pyridines. The target products were obtained in moderate to good yields using only 1 mol % PdCl(C3H5)(dppb) as the catalyst. Substituents, such as fluoro, acetyl, nitrile, nitro, methoxy or amino on the pyridyl bromide are tolerated. However, the nature of the substituents has an important influence on the yields. Electron-withdrawing substituent favours the reaction; whereas electron-donating are unfavourable. 相似文献
10.
The passage of solid spheres through a liquid–liquid interface was experimentally investigated using a high-speed video and
PIV (particle image velocimetry) system. Experiments were conducted in a square Plexiglas column of 0.1 m. The Newtonian Emkarox
(HV45 50 and 65% wt) aqueous solutions were employed for the dense phase, while different silicone oils of different viscosity
ranging from 10 to 100 mPa s were used as light phase. Experimental results quantitatively reveal the effect of the sphere’s
size, interfacial tension and viscosity of both phases on the retaining time and the height of the liquid entrained behind
the sphere. These data were combined with our previous results concerning the passage of a rising bubble through a liquid–liquid
interface in order to propose a general relationship for the interface breakthrough for the wide range of Mo
1/Mo
2 ∈ [2 × 10−5–5 × 104] and Re
1/Re
2 ∈ [2 × 10−3–5 × 102]. 相似文献