Search results for "Catalysis"
showing 10 items of 5944 documents
Novel functionalized cispentacin derivatives. Synthesis of 1,2,3-triazole-substituted 2-aminocyclopentanecarboxylate stereoisomers
2008
Four 1,2,3-triazole-substituted ethyl 2-amino-3-hydroxycyclopentanecarboxylate diastereomers (3,4-disubstituted cispentacins) with a cyclopentane skeleton were prepared in enantiomerically pure form from racemic β-lactam 7 via enzymatic ring opening, epoxidation and selective ring opening of the oxirane ring with sodium azide. The formation of the 1,2,3-triazole ring system involved click chemistry: 1,3-dipolar cycloaddition of the corresponding 4-substituted azidocarboxylates with diethyl acetylenedicarboxylate.
Synthesis of Isoxazole and 1,2,3-Triazole Isoindole Derivatives via Silver- and Copper-Catalyzed 1,3-Dipolar Cycloaddition Reaction.
2016
International audience; The CuI-or Ag 2 CO 3-catalyzed [3+2] cycloaddition of propargyl-substituted dihydroisoindolin-1-one (3) with arylnitrile oxides 1a-d (Ar = Ph, p-MeC 6 H 4 , p-MeOC 6 H 4 , p-ClC 6 H 4) produces in good yields novel 3,5-disubstituted isoxazoles 4 of the ethyl-2-benzyl-3-oxo-1-((3-arylisoxazol-5yl)methyl)-2,3-dihydro-1H-isoindole-1-carboxylate type. With aryl azides 2a-d (Ar = Ph, p-MeC 6 H 4 , p-OMeC 6 H 4 , p-ClC 6 H 4), a series of 1,4-disubstituted 1,2,3-triazoles 6 (ethyl-2-benzyl-3-oxo-1-((1-aryl-1H-1,2,3-triazol-4-yl)methyl)-2,3-dihydro-1H-isoindole-1-carboxylates) was obtained. The reactions proceed in a regioselective manner affording exclusively racemic adduc…
1,2,3-Triazole in Heterocyclic Compounds, Endowed with Biological Activity, through 1,3-Dipolar Cycloadditions
2014
1,3-Dipolar cycloaddition reactions can be considered a powerful synthetic tool in the building of heterocyclic rings, with applications in different fields. In this review we focus on the synthesis of biologically active compounds possessing the 1,2,3-triazole core through 1,3-dipolar cycloaddition reactions. The 1,2,3-triazole skeleton can be present as a single disubstituted ring, as a linker between two molecules, or embedded in a polyheterocycle. The cycloaddition reactions are usually catalysed by copper or ruthenium. Domino reactions can be achieved through dipolarophile anion formation, generally followed by cyclisation. The variety of attainable heterocyclic structures gives an ill…
Sustainable Construction of Heterocyclic 1,2,3-Triazoles by Strict Click [3+2] Cycloaddition Reactions Between Azides and Alkynes on Copper/Carbon in…
2019
1,4-Disubstituted-1,2,3-triazoles, considered as an important and useful class of heterocycles with potential applications in material science and biology, have been prepared in an efficient and selective manner by copper on carbon-catalyzed [3+2] cycloaddition reactions of azides and alkynes (CuAAC) in water under strict click chemistry conditions. Copper(I) catalysts heterogenized onto commercially activated carbon materials (Cu-CC) and on another carbon material produced from vegetable biomass using Argan nut shells (Cu-CANS) were found to be versatile catalytic sources for sustainable CuAAC. These copper on carbon supports were prepared and fully characterized by using two types of acti…
Stability of Asymmetric Lipid Bilayers Assessed by Molecular Dynamics Simulations
2009
The asymmetric insertion of amphiphiles into biological membranes compromises the balance between the inner and outer monolayers. As a result, area expansion of the receiving leaflet and curvature strain may lead to membrane permeation, shape changes, or membrane fusion events. We have conducted both atomistic and coarse-grained molecular dynamics simulations of dipalmitoyl-phosphatidylcholine (DPPC) bilayers to study the effect of an asymmetric distribution of lipids between the two monolayers on membrane stability. Highly asymmetric lipid bilayers were found to be surprisingly stable within the submicrosecond time span of the simulations. Even the limiting case of a monolayer immersed in …
Superfluorinated ionic liquid crystals based on supramolecular, halogen-bonded anions
2016
Unconventional ionic liquid crystals in which the liquid crystallinity is enabled by halogen-bonded supramolecular anions [CnF2 n+1-I⋯I⋯I-CnF2 n+1]- are reported. The material system is unique in many ways, demonstrating for the first time 1) ionic, halogen-bonded liquid crystals, and 2) imidazolium-based ionic liquid crystals in which the occurrence of liquid crystallinity is not driven by the alkyl chains of the cation. Out of the ordinary: The high directionality of halogen bonds and the fluorophobic effect were exploited in the design and synthesis of a new family of unconventional superfluorinated ionic liquid crystals. The liquid crystallinity of the system is driven by halogen-bonded…
Coordination nano-space as stage of hydrogen ortho–para conversion
2015
The ability to design and control properties of nano-sized space in porous coordination polymers (PCPs) would provide us with an ideal stage for fascinating physical and chemical phenomena. We found an interconversion of nuclear-spin isomers for hydrogen molecule H 2 adsorbed in a Hofmann-type PCP, {Fe(pz)[Pd(CN) 4 ]} (pz=pyrazine), by the temperature dependence of Raman spectra. The ortho (o)–para (p) conversion process of H 2 is forbidden for an isolated molecule. The charge density study using synchrotron radiation X-ray diffraction reveals the electric field generated in coordination nano-space. The present results corroborate similar findings observed on different systems and confirm …
The molecular identification of organic compounds in the atmosphere: state of the art and challenges.
2015
SSCI-VIDE+ATARI:CARE+BNO:BDA; International audience
Keggin heteropolyacid supported on BN and C3N4: Comparison between catalytic and photocatalytic alcohol dehydration
2020
The Keggin heteropolyacid (HPA), H3PW12O40 (PW12) has been supported on commercial boron nitride (BN) and two types of home prepared carbon nitride (C3N4). The supported PW12 was used in the gas-solid (photo)catalytic 2-propanol dehydration reaction to give propene at atmospheric pressure and temperatures in the range 70–120 °C and resulted more active than the pristine PW12. Reaction rate increased by increasing the temperature. Noticeably, the propene formation rate was higher by irradiating the catalytic system. The PW12/BN material resulted more active than PW12/C3N4. The acidity of the HPA cluster accounts for the catalytic role, whereas both the acidity and the redox properties of the…
ZrO2 Based materials as photocatalysts for 2-propanol oxidation by using UV and solar light irradiation and tests for CO2 reduction
2018
Abstract Bare ZrO2, Ce doped ZrO2 and Er doped ZrO2 samples have been prepared by a hydrothermal process and have been used as photocatalysts for 2-propanol oxidation reaction in gas solid regime. Moreover, some preliminary tests have been carried out for CO2 reduction. The samples were physico-chemically characterized and both bare and doped ZrO2 based materials resulted active for oxidation and reduction reactions by using UV and solar irradiation. The reactivity results have been correlated with the compositional, structural and morphological features of the photocatalysts.