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981.
Reddy Guda Mallikarjuna Sravya Gundala Yuvaraja Gutha Camilo Alexandre Zyryanov Grigory V. Garcia Jarem Raul 《Research on Chemical Intermediates》2018,44(12):7491-7507
Research on Chemical Intermediates - Development of potent antibacterial and antifungal agents is a permanently new and unremitting investigation in the therapeutic field. Still, medicinal research... 相似文献
982.
Mathilde Lachia François Richard Raphael Bigler Amandine Kolleth-Krieger Michael Dieckmann Alexandre Lumbroso Ulfet Karadeniz Saron Catak Alain De Mesmaeker 《Tetrahedron letters》2018,59(20):1896-1901
γ-Lactams are important building blocks for the synthesis of biologically active molecules and can easily be accessed via Beckmann rearrangement of cyclobutanones. However, Beckmann fragmentation is often a competing reaction for these strained ketones. We found that performing the Beckmann rearrangement with Tamura’s reagent in the presence of aqueous HCl suppresses the undesired fragmentation reaction. This improved procedure was applied to a broad scope of substrates affording monocyclic, bicyclic, tricyclic or spirocyclic lactams.Our experimental results and DFT calculations suggest that the mechanism of the rearrangement probably involves a tetrahedral intermediate and doesn’t proceed via oxime fragmentation as in a classical Beckmann rearrangement. 相似文献
983.
Abdoul Aziz Ndiaye Ana Lacoste Alexandre Bès Andrii Zaitsev Fabienne Poncin-Epaillard Dominique Debarnot 《Plasma Chemistry and Plasma Processing》2018,38(4):887-902
In the wavelength range from 200 up to 1000 nm, optical emission from electronically excited fragments (CN, CH, NH, C2, H2, N2, N2+, and H-Balmer) is detected when aniline plasmas are generated in a multi-dipolar microwave reactor. The optical emission spectrum monitored in very low-pressure conditions (~?1 mTorr) shows important characteristics. The Hα, Hβ and CN species are the most radiating systems and according to the NH/N2 intensity ratio, two different operating regimes are observed suggesting a change in the reaction pathways. These two regimes are correlated to changes of the plasma characteristics (electron temperature and density) deduced from Langmuir probe measurements. The plasma thermodynamic state is quantified by implementing numerical simulation codes for synthetic spectra calculations. The rovibrational temperatures (Tr, Tv) are determined for some neutral species (CN, CH). The obtained values of Tr and Tv show the non-local thermodynamic equilibrium of the vibrational and rotational states (Tr?<?Tv). Moreover, the very low pressure aniline-based plasmas deviate substantially from the Boltzmann distribution. Correlation between the optical emission data and the solid phase analysis allows proving that the in situ characterization of the plasma phase is an important predictive tool of physico-chemical properties of the film. From these correlated data, we deduce preponderant chemical reaction pathways which help to better understand the plasma generation. Relative contributions of the dehydrogenation of C–H and N–H groups are established in order to deduce the leading initiation reaction for H-Balmer line formation. 相似文献
984.
Amandine Kolleth Simona Müller Alexandre Lumbroso Gamze Tanriver Saron Catak Sarah Sulzer-Mossé Alain De Mesmaeker 《Tetrahedron letters》2018,59(34):3242-3248
We described a general approach to 3-aminobenzothiophenes and 3-aminothiophenes fused to 5-membered heteroaromatic rings as thiophenes, furans and pyrroles through a 6π-elctrocyclization reaction of keteniminium salts. We investigated various substituents not only on the aromatic rings, but also at C-2 and on the nitrogen atom of the keteniminium salt. In particular, we have determined the electronic requirements of the nitrogen substitution to secure the efficient formation of the corresponding keteniminium salt. A clear relation between the pKa of the amine leading to the formation of the keteniminium salt and the yield obtained for benzothiophene is established and should find broad application to other reactions involving these intermediates. Additional insight on the ease of this 6π-electrocyclization reaction was gained through competition reactions and DFT calculations. 相似文献
985.
Julianna M. Vagula Bruno A. Rocha Alexandre R. Silva Narendra Narain Ciomar A. Bersani-Amado Oscar O. S. Junior 《Analytical letters》2018,51(13):1973-1985
Solanum americanum Mill. has been traditionally used for the treatment of fever, stomachache, skin diseases, gynecological disorders, and different kinds of inflammation. This study evaluated the anti-inflammatory response of different extracts obtained from ripe fruits of S. americanum Mill., in experimental models and evaluated them qualitatively using ultrafast liquid chromatography with diode array and time-of-flight mass spectrometry (UFLC-DAD/TOF-MS). The inflammatory response of four extracts of ripe fruits was evaluated for the systemic and topical anti-inflammatory activities. The compounds in each extract were identified using UFLC-DAD-TOF/MS. A total of 34 compounds was identified in the four extracts. The best results were obtained in compounds from the aqueous and chloroform extracts. This study demonstrated a significant anti-inflammatory activity for the compounds present in fruit of S. americanum Mill. 相似文献
986.
P. Legay J. L. Benchimol F. Alexandre J. C. Harmand 《Journal of Crystal Growth》1995,150(1-4):394-398
In order to optimize the shape of chemical beam epitaxy (CBE) selective area growth, growth rates on (100), (111)B, (111)A and (110) substrate orientations have been examined for GaAs and InP materials. (111)B GaAs growth rate appears to be drastically enhanced at low V/III ratio, which has been applied to grow selective GaAs patterns limited by vertical sidewalls. Concerning InP, high growth rates were obtained on all orientations. This was used to perfectly fill a rectangular groove by selective embedded InP growth. 相似文献
987.
The compound 5-amino-1,3,4-thiadiazole-thiol (ATT) was anchored onto silica gel surfaces by homogeneous and heterogeneous routes. Both silica modification methodologies resulted in similar products, named SiCTT and SiATT, respectively. These materials were characterized by infrared and Raman spectroscopies, superficial area and elemental analysis as well as 13C and 29Si NMR spectroscopy. Elemental analysis proved that the material SiCTT presented a higher ATT immobilization than SiATT, with values of 0.73 and 0.65 mmol g−1, respectively. NMR, Raman and infrared spectroscopy corroborate to confirm the immobilization of ATT on both surfaces. Raman spectroscopy showed that the reaction of the ATT with silylant agent or pre-modified silica occurred by the thiol group, resulting in a surface with two sulfur groups and one free amine group able to complex soft and hard acids. 相似文献
988.
J. L. Benchimol X. Q. Zhang Y. Gao G. Le Roux H. Thibierge F. Alexandre 《Journal of Crystal Growth》1992,120(1-4):189-194
AlxGa1−xAs and AlxIn1−xAs alloys were grown on GaAs and InP, respectively, by chemical beam epitaxy, using trimethylamine alane (TMAA) as the source of aluminium. TMAA could be used properly only after some problems had been solved. Low carbon and oxygen concentrations were obtained in both alloys, leading to residual hole concentrations of 2 × 1016 cm-3 in Al0.3Ga0.7As. The abruptness of the AlGaAs/GaAs interface proved the absence of TMAA memory effect. The control of AlxIn1−xAs solid composition was more difficult than for GaxIn1−xAs, but was less sensitive to growth temperature. Photoluminescence intensities of Al0.3Ga0.7As and Al0.48In0.52As grown at 510°C were similar to those of MBE grown materials. 相似文献
989.
Foundations of Computational Mathematics - In this paper, we investigate the approximation of a diffusion model problem with contrasted diffusivity for various nonconforming approximation methods.... 相似文献
990.
By potential theoretic methods involving the Cartan fine topology a recent result by two of the authors is extended as follows: The Riesz charge of the lower envelope of a family of 3 or more -subharmonic functions (no longer supposed continuous) in the plane equals the infimum of the charges of the lower envelopes of all pairs of functions from the family. As a key to this it is shown in two different ways that the (fine) harmonic measures of any 3 pairwise disjoint finely open planar sets have Borel supports with empty intersection. One proof of this uses the Jordan curve theorem and the fact that the set of inaccessible points of the fine boundary of a fine domain is Borel and has zero harmonic measure; the other involves Carleman-Tsuji type estimates together with a fine topology version of a recent result of P. Jones and T. Wolff on harmonic measure and Hausdorff dimension. 相似文献