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71.
72.
Evelyne Delfourne 《Tetrahedron letters》2011,52(49):6560-6561
A three-step procedure to isogranulatimide C starting with the thermal condensation of 3-chloroindole with imidazole and proceeding in 41% yield is described. 相似文献
73.
Guillaume Guery J. David Musgraves Christine Labrugere Evelyne Fargin Thierry Cardinal Kathleen Richardson 《Journal of Non》2012,358(15):1740-1745
In this paper, a detailed study to examine the influence of chalcogen S/Se mole % in the Ge28Sb12S60 ?xSex glass system, with x = 0, 15, 30, 45 and 60, is presented that provides insight into the effect of chalcogen content on the glass network and properties. Specifically, we report results of a systematic study to evaluate the relationship between compositional variation, glass properties and dominant bonding configurations. These materials are important to applications in optics manufacturing where correlation of physical and optical properties is required to predict fabrication behavior and ultimate material performance. It has been found that the dominant bonds in the glass system change upon reaching a specific molar ratio (percentage, %) of chalcogen substitution, between 30 < x < 45 mol%, changing from Ge―Se to Sb―Se bonds as the dominant bond type. This singularity has been observed using micro-Raman spectroscopy and X-ray photoelectron spectroscopy. This effect of the dominant bond configurational change was also shown to impart changes in important physical properties including micro-hardness, thermal properties, and the glass' viscometric behavior. Results indicate that the observed dominant bond change was responsible for a constant value in the evolution of both the micro-hardness and calorimetric glass transition temperature. The viscosity was also affected by the change in dominant bond type, breaking the monotony of the viscosity evolution during the S substitution, due to the total strength of the vitreous system which does not linearly increase. 相似文献
74.
The structural assignment of bispyrroloquinone and bispyrroloiminoquinone regioisomers was achieved using 13C NMR spectral data. In the case of bispyrroloiminoquinones, the carbonyl group in the regioisomer possessing a nitrogen atom in both α‐positions was systematically less deshielded than the carbonyl group in the other regioisomer. In the case of bispyrroloquinones, the most deshielded carbonyl group in the regioisomer with a nitrogen atom in both α‐positions was more deshielded than the same carbonyl group in the other regioisomer. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
75.
Efficient Pd‐Catalyzed Allene Synthesis from Alkynes and Aryl Bromides through an Intramolecular Base‐Assisted Deprotonation (iBAD) Mechanism
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Natalie Nella Dr. Evelyne Parker Dr. Julien Hitce Dr. Paolo Larini Dr. Rodolphe Jazzar Prof. Olivier Baudoin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13272-13278
An optimized ligand‐controlled palladium‐catalyzed allene synthesis starting from alkynes and aryl bromides giving rise to allene products in a simple and direct manner is described. The methodology is performed in an inter‐ and intramolecular fashion with unprecedented scope and excellent yields. Based on mechanistic investigations and on DFT calculations, the role played by the carboxylic additive (i.e., PivOH) in controlling the selectivity of the reaction is discussed, allowing us to propose an intramolecular base‐assisted deprotonation (iBAD) mechanism for this process. 相似文献
76.
Highly Enantioselective Rhodium(I)‐Catalyzed Activation of Enantiotopic Cyclobutanone CC Bonds
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Laetitia Souillart Dr. Evelyne Parker Prof. Dr. Nicolai Cramer 《Angewandte Chemie (International ed. in English)》2014,53(11):3001-3005
The selective functionalization of carbon–carbon σ bonds is a synthetic strategy that offers uncommon retrosynthetic disconnections. Despite progress in C? C activation and its great importance, the development of asymmetric reactions lags behind. Rhodium(I)‐catalyzed selective oxidative additions into enantiotopic C? C bonds in cyclobutanones are reported. Even operating at a reaction temperature of 130 °C, the process is characterized by outstanding enantioselectivity with the e.r. generally greater than 99.5:0.5. The intermediate rhodacycle is shown to react with a wide variety of tethered olefins to deliver complex bicyclic ketones in high yields. 相似文献
77.
Evelyne Chelain Olivier Floch Stanislas Czernecki 《Journal of carbohydrate chemistry》2013,32(8):1251-1256
Abstract Since l-nucleosides and 2-deoxy l-nucleosides are finding more and more applications for the preparation of nucleases resistant “antisense” oligonucleotides1 as well as for preparation of modified nucleosides as potential inhibitors of HIV,2 efficient preparation of l-ribofuranose derivatives is needed. Although l-ribose was obtained by inversion of d-ribono-1,4-lactone followed by reduction,3 epimerization at C-2 of l-arabinose4 and inversion of configuration at C-2 of l-arabinose or at C-3 of l-xylose by displacement of a sulfonate group5 were also evaluated, but were found to be not very satisfactory. We recently published a preparation of l-ribofuranose derivatives from l-arabinose in which the configuration at C-2 was inverted by an oxidation-reduction sequence after suitable protection of O-3 and O-5.6 Although a high overall yield was obtained, upscaling was difficult because none of the intermediates were obtained in crystalline form. Therefore we decided to evaluate the same methodology starting from l-xylofuranose and we report herein our results. 相似文献
78.
Most of the models proposed in literature for binary diffusion coefficients of solids in supercritical fluids are restricted to infinite dilution; this can be explained by the fact that most of experimental data are performed in the dilute range. However some industrial processes, such as supercritical fluid separation, operate at finite concentration for complex mixtures. In this case, the concentration dependence of diffusion coefficients must be considered, especially near the upper critical endpoint (UCEP) where a strong decrease of diffusion coefficients was experimentally observed. In order to represent this slowing down, a modified version of the Darken equation was proposed in literature for naphthalene in supercritical carbon dioxide. In this paper, the conditions of application of such a modelling are investigated. In particular, we focus on the order of magnitude of the solubility of the solid and on the vicinity of the critical endpoint. Various equations proposed in literature for the modelling of the infinite dilution diffusion coefficients of the solutes are also compared. Ten binary mixtures of solids with supercritical carbon dioxide were considered for this purpose. 相似文献
79.
Bantreil X Vaxelaire C Godet T Parker E Sauer C Belmont P 《Organic & biomolecular chemistry》2011,9(13):4831-4841
A family of furoquinolines were efficiently obtained through a tandem acetalization/cycloisomerization process catalyzed by (5 mol%) silver imidazolate polymer and triphenylphosphine, and diversity was brought by the use of 7 different alcohol groups. From these furoquinolines, 3 examples of reduced derivatives could be obtained (d.r. up to 94 : 6), 10 different spiroketal derivatives by hetero-Diels-Alder reaction (d.r. up to 20 : 1), 8 hetero-[5,5]-spirocycles by cycloaddition with dibromoformaldoxime (d.r. up to 86 : 14) and finally 6 hetero-[5,6]-spirocycles by [4 + 2] cycloaddition with ethyl 3-bromo-2-(hydroxyimino)propanoate (d.r. up to 90 : 10). 相似文献
80.
Araoz R Servent D Molgó J Iorga BI Fruchart-Gaillard C Benoit E Gu Z Stivala C Zakarian A 《Journal of the American Chemical Society》2011,133(27):10499-10511
Pinnatoxins belong to an emerging class of potent marine toxins of the cyclic imine group. Detailed studies of their biological effects have been impeded by unavailability of the complex natural product from natural sources. This work describes the development of a robust, scalable synthetic sequence relying on a convergent strategy that delivered a sufficient amount of the toxin for detailed biological studies and its commercialization for use by other research groups and regulatory agencies. A central transformation in the synthesis is the highly diastereoselective Ireland-Claisen rearrangement of a complex α,α-disubstituted allylic ester based on a unique mode for stereoselective enolization through a chirality match between the substrate and the lithium amide base. With synthetic pinnatoxin A, a detailed study has been performed that provides conclusive evidence for its mode of action as a potent inhibitor of nicotinic acetylcholine receptors selective for the human neuronal α7 subtype. The comprehensive electrophysiological, biochemical, and computational studies support the view that the spiroimine subunit of pinnatoxins is critical for blocking nicotinic acetylcholine receptor subtypes, as evidenced by analyzing the effect of a synthetic analogue of pinnatoxin A containing an open form of the imine ring. Our studies have paved the way for the production of certified standards to be used for mass-spectrometric determination of these toxins in marine matrices and for the development of tests to detect these toxins in contaminated shellfish. 相似文献