Search results for "Catalysis"
showing 10 items of 5944 documents
Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges
2021
The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton …
One-pot cross-enyne metathesis (CEYM)-Diels-Alder reaction of gem-difluoropropargylic alkynes.
2013
Propargylic difluorides 1 were used as starting substrates in a combination of cross-enyne metathesis and Diels–Alder reactions. Thus, the reaction of 1 with ethylene in the presence of 2nd generation Hoveyda–Grubbs catalyst generates a diene moiety which in situ reacts with a wide variety of dienophiles giving rise to a small family of new fluorinated carbo- and heterocyclic derivatives in moderate to good yields. This is a complementary protocol to the one previously described by our research group, which involved the use of 1,7-octadiene as an internal source of ethylene.
Stereoselective aldol reaction catalyzed by a highly recyclable polystyrene supported substituted prolinamide catalyst
2008
Polystyrene supported substituted prolinamide was used as catalyst in the aldol reaction between cyclohexanone or acetone and several substituted benzaldehydes in chloroform/water. This catalyst afforded aldol products in high yields and stereoselectivities, especially in the case of reactions performed with acetone. The catalyst was easily recovered by filtration and reused, after regeneration with formic acid, up to 22 times.
Novel Stereoselective Intramolecular Processes for the Generation of New Molecular Entities
2019
La Química Orgánica, además de constituir una fuente inagotable de fascinación académica por su capacidad de generar un número virtualmente infinito de nuevas estructuras moleculares, ha proporcionado una poderosa herramienta, el cribado de librerías de moléculas orgánicas, en el ámbito de la química biológica/médica y el descubrimiento de fármacos que se ha convertido en el caballo de batalla en la identificación de nuevas dianas terapéuticas y sus correspondientes moduladores y potenciales fármacos, con un impacto directo sobre la salud humana. La principal problemática de estas librerías es el aspecto de la diversidad estructural, ya que la probabilidad de dar con un fármaco candidato es…
Carbon Dioxide Activation and Reaction Induced by Electron Transfer at an Oxide-Metal Interface
2015
A model system has been created to shuttle electrons through a metal-insulator-metal (MIM) structure to induce the formation of a CO2 anion radical from adsorbed gas-phase carbon dioxide that subsequently reacts to form an oxalate species. The process is completely reversible, and thus allows the elementary steps involved to be studied at the atomic level. The oxalate species at the MIM interface have been identified locally by scanning tunneling microscopy, chemically by IR spectroscopy, and their formation verified by density functional calculations.
An efficient method for selective oxidation of (oxime)Pt(II) to (oxime)Pt(IV) species using N,N-dichlorotosylamide
2016
The oxidation of (oxime)PtII species using the electrophilic chlorine-based oxidant N,N-dichlorotosylamide (4-CH3C6H4SO2NCl2) was studied. The reactions of trans-[PtCl2(oxime)2] (where oxime = acetoxime, cyclopentanone oxime, or acetaldoxime) with this oxidant led to trans-[PtCl4(oxime)2] products. The oxidation of trans-[Pt(o-OC6H4CH = NOH)2] at room temperature gave trans-[PtCl2(o-OC6H4CH = NOH)2], whereas the same reaction upon heating was accompanied by electrophilic substitution of the benzene rings. peerReviewed
1,1prime-Binaphthyl-2-methylpyridinium-based peroxophosphotungstate salts: synthesis, characterization, and their use as oxidation catalysts
2009
A series of 1,1′-binaphthyl-2-methylammonium and pyridinium salts 6, 7, and 8 was synthesized through the coupling reaction of 2-(bromomethyl)-1,1′-binaphthalene (5) with the dendritic tetraallyl pyridinedicarbinol dendron 2 as well as triethylamine and 4-tert-butylpyridine. Tetraallyl pyridinedicarbinol dendron 2 was prepared by allylation of commercially available diethyl pyridine-3,5-dicarboxylate (1). The allylation of 2 with allyltrimethylsilane in the presence of boron trifluoride was unsuccessful, as tetraallyl pyridinedicarbinol trifluoroboron adduct 3 was obtained instead of expected hexaallylpyridine compound 4. The catalytic hydrogenation of allyl groups of the ammonium salt of 2…
Oxidation of aromatic alcohols in irradiated aqueous suspensions of commercial and home-prepared rutile TiO(2): a selectivity study.
2008
WOS: 000256241700021
DFT Prediction of Enhanced Reducibility of Monoclinic Zirconia upon Rhodium Deposition.
2018
Oxides are an important class of materials and are widely used, for example, as supports in heterogeneous catalysis. In a number of industrial catalytic processes, oxide supports actively participate in chemical transformations by releasing lattice oxygen anions. While this is intuitively understood for reducible oxides, the reducibility of irreducible oxides may be modified via nanoengineering or upon inclusion of foreign species. Our calculations predict that the ability of irreducible monoclinic zirconia to release oxygen improves substantially upon deposition of rhodium. Through a comprehensive screening of Rh/ZrO2 with different size of the rhodium species, we find that a Rh adatom and…
Controlling Oxidative Addition and Reductive Elimination at Tin(I) via Hemi-Lability.
2021
We report on the synthesis of a distannyne supported by a pincer ligand bearing pendant amine donors that is capable of reversibly activating E–H bonds at one or both of the tin centres through dissociation of the hemi-labile N–Sn donor/acceptor interactions. This chemistry can be exploited to sequentially (and reversibly) assemble mixed-valence chains of tin atoms of the type ArSn{Sn(Ar)H} n SnAr ( n = 1, 2). The experimentally observed (decreasing) propensity towards chain growth with increasing chain length can be rationalized both thermodynamically and kinetically by the electron-withdrawing properties of the –Sn(Ar)H– backbone units generated via oxidative addition. peerReviewed