Search results for "Selectivity"
showing 10 items of 1148 documents
Separation of the azeotropic mixture 2-propanol + water employing different imidazolium ionic liquids as solvents
2020
Abstract The liquid-liquid equilibria of the ternary systems water (1) + 2-propanol (2) + [emim][Tf2N] (3) and water (1) + 2-propanol (2) + [hmim][Tf2N] (3) at 283.2, 303.2 and 323.2 K and atmospheric pressure were investigated, in order to achieve a better knowledge of the ternary mixture behaviour. The capability of [emim][Tf2N] and [hmim][Tf2N] as solvents in the separation of the azeotropic mixture water + 2-propanol was studied through the distribution coefficient and selectivity, and compared with the results obtained with other ionic liquids in the same azeotropic mixture studied before by our research group. The thermodynamic parameters of both ternary mixtures were calculated by th…
A new efficient, highly dispersed, Pd nanoparticulate silica supported catalyst synthesized from an organometallic precursor. Study of the homogeneou…
2018
[EN] A new Pd(0) catalyst supported on silica UVM-7 has been synthesized from the organometallic [Pd-2(mu-(C6H4) Pp(2))(2)(CH3CN)(4)](BF4)(2) precursor, characterized by the high dispersion, activity, and small size of the palladium nanoclusters fixed on the silica surface. The catalyst was tested for the Suzuki-Miyaura (SM) reaction of different 4-substitutedphenyl halides with phenylboronic acid. The kinetic study concurs with most of the catalytic action was carried out by Pd species originated by the partial solubilization of Pd immobilized on mesoporous silica. The Schmidt's analysis of differential selectivity (SADS) in several competitive SM reactions, together the STEM-HAADF and HRT…
The heterogeneity of new entrants and the selectivity of higher education institutions : some results using data from the CHEERS project
2002
02079; International audience; This paper attempts to test whether there stillexist differences in selectivity between highereducation institutions. Data from the CHEERS(Careers after Higher Education: a EuropeanResearch Survey) project enables us to describethe differences in institutional selectivity ineach country across different fields. We askthe question: how selective are institutionstoday, particularly in the case of Europe andJapan?. In order to describe the selectivity ofhigher education institutions for each field ineach country, we use the entry grade given byeach graduate in the CHEERS data. Despite thedifferences in the grading references in thedifferent countries, these data …
Metal-Free and User-Friendly Regioselective Hydroxyfluorination of Olefins
2018
A simple, user-friendly, metal-free protocol for the regioselective anti-Markovnikov hydrofluorination of olefins using readily available and inexpensive reagents has been developed. This new approach displays a broader scope than previously reported methodologies and has been applied to the late-stage fluorination of a complex molecule, giving rise to a fluorosteroid derivative. The stereochemistry of the process has also been studied in some detail.
Synthesis of vinca alkaloids and related compounds LX. A simple transformation of apovincamine into vincamine
1992
Abstract The 15α-chloro-vincamine derivative 2 was prepared and proved to be key intermediate of a two-step transformation of apovincamine into vincamine. The structure of 2 was established via detailed NMR and X-ray investigations.
Solvent-Enhanced Diastereo- and Regioselectivity in the PdII-Catalyzed Synthesis of Six- and Eight-Membered Heterocycles viacis-Aminopalladation
2009
The Pd(II)-catalyzed intramolecular oxidative cyclization of tosyl-protected cis- and trans-N-allyl-2-aminocyclohexanecarboxamides was examined, and efficient syntheses of cyclohexane-fused pyrimidin-4-ones and 1,5-diazocin-6-ones were developed. In the course of the research, a marked solvent effect was observed on both the regio- and diastereoselectivity. Additionally, a novel Pd(II)-mediated domino oxidation, oxidative amination reaction was discovered. Our experimental and theoretical findings suggest that the reactions proceed via a cis-aminopalladation mechanism.
Copper-catalyzed regioselective synthesis of (E)-β-fluorovinyl sulfones
2019
Organofluorine compounds are finding increasing application in a variety of fields such as pharmaceutical, agrochemical, and material sciences. However, given the scarcity of fluorine-containing natural products, advancement in this area depends almost entirely on the development of new synthetic methodologies. In this article, we present the synthesis of a series of previously undescribed (E)-&beta
The physiological basis for contrast opponency in motion computation in Drosophila
2021
This dataset contains traces (dF/F0) from in vivo two-photon calcium imaging from Tm1, tm2, Tm4, Tm9, CT1, and T5 neurons from responses to ONOFF fullfield flashes, ON and OFF bars, and moving sinewaves.
Proton Acid-Catalysed Transformations of Estrogen Derivatives: New Results and Some Mechanistic Aspects of theKober Colour Reaction
1994
The 3-O-methylated estrogen derivatives 1a-d and α-estradiol (1e) underwent sulfuric acid-catalysed transformations to furnish the steroids 2–6. The processes involved in the reaction sequence are regioselective sulfonation and, above all, the Wagner-Meerwein rearrangement of the methyl group at C-13. With the objective of obtaining further information on the course of the Kober colour reaction of estrogens, some UV/VIS and ESR spectroscopic investigations were also carried out. Protonenkatalysierte Transformationen von Estrogen-Derivaten: Neue Ergebnisse und einige mechanistische Aspekte der Kober-Farbreaktion Die O-methylierten Estrogenderivate 1a-d und α-Estradiol (1e) reagieren in Schwe…
D2 and H2 adsorption capacity and selectivity in CHA zeolites: Effect of Si/Al ratio, cationic composition and temperature
2020
International audience; The work deals with the effect of composition of CHA zeolites on the adsorption and separation of H2 and D2 under cryogenic temperatures. In the first part of this work the effect of Si/Al ratio and cationic composition on single gas adsorption of H2 and D2 was studied at 77.4 K. It was found that the adsorption capacities increase with Al content up to Si/Al = 2.1. Unexpectedly, Na-CHA zeolite with the highest Al content (Si/Al = 1.1) adsorbs only negligible amount because of the collapse of the zeolite structure upon dehydration at 400°C. The Na-and Li-containing chabazites with Si/Al = 2.1 possess similar adsorption capacities. In contrast, progressive replacement…