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Catalytic Transformations (catalytic + transformation)
Selected AbstractsFormation of Furfural in Catalytic Transformation of Levoglucosan over Mesoporous MaterialsCHEMCATCHEM, Issue 5 2010M. Käldström Abstract Catalytic transformations of levoglucosan (1-6-anhydro-,- D -glucopyranose) and furfural were carried out in a fixed-bed reactor at 573,K over mesoporous materials. Proton forms of MCM-41, MCM-48, SBA-15, and platinum form of MCM-48 catalysts were tested in the reaction, whereas H-Beta and quartz sand were used as reference materials. The yield of the transformation products was substantially influenced by the catalyst structures. Oxygenated species were the main liquid products, consisting mainly of aldehydes and furfural. The formation of furfural was the highest over MCM-41 catalyst followed by SBA-15, MCM-48, and H-Beta catalyst. All catalysts were to some extent deactivated due to coke formation. However, it was possible to successfully regenerate the spent catalysts without changing the structure. [source] Rhodium-Mediated Decarboxylative Conjugate Addition of Fluorinated Benzoic Acids: Stoichiometric and Catalytic Transformations,ANGEWANDTE CHEMIE, Issue 36 2009Zhong-Ming Sun Dr. Je nach Bisphosphanligand entsteht bei der Decarboxylierung von 2,6-difluorierten Benzoesäuren mit einem RhI -Katalysator in Gegenwart eines Acrylesters oder Acrylamids bevorzugt das konjugierte Addukt 1 oder das Produkt der Heck-Mizoroki-Arylierung (2; Binap=2,2,-Bis(diphenylphosphanyl)-1,1,-binaphthyl, diop=4,5-Bis(diphenylphosphanylmethyl)-2,2-dimethyl-1,3-dioxolan). [source] ChemInform Abstract: Single-Pot Triple Catalytic Transformations Based on Coupling of in situ Generated Allyl Boronates with in situ Hydrolyzed Acetals.CHEMINFORM, Issue 47 2008Nicklas Selander Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Formation of Furfural in Catalytic Transformation of Levoglucosan over Mesoporous MaterialsCHEMCATCHEM, Issue 5 2010M. Käldström Abstract Catalytic transformations of levoglucosan (1-6-anhydro-,- D -glucopyranose) and furfural were carried out in a fixed-bed reactor at 573,K over mesoporous materials. Proton forms of MCM-41, MCM-48, SBA-15, and platinum form of MCM-48 catalysts were tested in the reaction, whereas H-Beta and quartz sand were used as reference materials. The yield of the transformation products was substantially influenced by the catalyst structures. Oxygenated species were the main liquid products, consisting mainly of aldehydes and furfural. The formation of furfural was the highest over MCM-41 catalyst followed by SBA-15, MCM-48, and H-Beta catalyst. All catalysts were to some extent deactivated due to coke formation. However, it was possible to successfully regenerate the spent catalysts without changing the structure. [source] Study of operating variables in the transformation of aqueous ethanol into hydrocarbons on an HZSM-5 zeoliteJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2002Andres T Aguayo Abstract With the aim of determining the possibilities of directly upgrading the liquid obtained from carbohydrate fermentation, the effect of operating conditions (temperature, space time, water content in the feed) has been studied in the catalytic transformation of aqueous ethanol into hydrocarbons on an HZSM-5 zeolite in an isothermal fixed bed reactor. Special attention has been paid to the effect of water content on the yield, product distribution and catalyst deactivation. Although deactivation by coke decreases as the water content is increased, this content must be limited at 450,°C and higher temperatures in order to avoid irreversible deactivation of the catalyst by dealumination. © 2002 Society of Chemical Industry [source] Redox-dependent structural changes in archaeal and bacterial Rieske-type [2Fe-2S] clustersPROTEIN SCIENCE, Issue 12 2002Nathaniel J. Cosper Abstract Proteins containing Rieske-type [2Fe-2S] clusters play important roles in many biological electron transfer reactions. Typically, [2Fe-2S] clusters are not directly involved in the catalytic transformation of substrate, but rather supply electrons to the active site. We report herein X-ray absorption spectroscopic (XAS) data that directly demonstrate an average increase in the iron,histidine bond length of at least 0.1 Å upon reduction of two distantly related Rieske-type clusters in archaeal Rieske ferredoxin from Sulfolobus solfataricus strain P-1 and bacterial anthranilate dioxygenases from Acinetobacter sp. strain ADP1. This localized redox-dependent structural change may fine tune the protein,protein interaction (in the case of ARF) or the interdomain interaction (in AntDO) to facilitate rapid electron transfer between a lower potential Rieske-type cluster and its redox partners, thereby regulating overall oxygenase reactions in the cells. [source] 2-(3-Pyridyl)-1,3,8-triazanaphthalene, a product of the catalytic transformation of 3-cyanopyridineACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2003Jan Janczak The title compound, C12H8N4, was obtained by thermal treatment of 3-cyanopyridine in the presence of magnesium phthalocyanine as catalyst. The X-ray structure analysis, in direct contrast to molecular orbital calculations corresponding to the gas phase, shows the molecule to be non-planar in the solid state, with an interplanar angle between the pyridine and 1,3,8-triazanaphthalene rings of 13.33,(9)°. Molecules related to one another by cell translation, and positioned at intervals consistent with ,,, intermolecular interactions, form stacks in the b direction. [source] Generalized treatment of NMR spectra for rapid chemical reactionsCONCEPTS IN MAGNETIC RESONANCE, Issue 4 2007Matthew D. Christianson Abstract Application of NMR spectroscopy to fast irreversible reactions (t1/2 < 0.7 s) has been hampered by limitations in instrumentation and general methods for modeling the complicated spectra that result. Analytical descriptions of nuclear spin dynamics during fast reactions, first solved by Ernst and coworkers, are limited to first-order reaction kinetics. We demonstrate that numeric methods enable simulation of NMR spectra for fast reactions having any form of rate law. Simulated stopped-flow NMR spectra are presented for a variety of common kinetic scenarios including reversible and irreversible reactions of first and second-order, multistep reactions, and catalytic transformations. The simulations demonstrate that a wealth of mechanistic information, including reaction rates, rate laws, and the existence of intermediates, is imbedded in a single NMR spectrum. The sensitivity of modern NMR instrumentation along with robust methods for simulating and fitting kinetic parameters of fast reactions make stopped-flow NMR an attractive method for kinetic studies of fast chemical reactions. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 165,183, 2007. [source] Ruthenium-Catalyzed Allenyl Carbamate Formation from Propargyl Alcohols and IsocyanatesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2008Edgar Haak Abstract Ruthenium complexes of redox-coupled cyclopentadienone ligands catalyze the formation of allenyl carbamates from propargyl alcohols and isocyanates. This efficient and atom-economical process represents the first catalytic access to allenyl carbamates, compounds of high synthetic potential. The reaction needs an acidic co-catalyst and can be performed at room temperature. In addition, new (cyclopentadienone)iron and -ruthenium complexes were synthesized, and mechanistic aspects regarding catalytic transformations of propargyl systems with ruthenium catalysts are obtained. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Sequential Stereoselective Catalysis: Two Single-Flask Reactions of a Substrate in the Presence of a Bifunctional Chiral Ligand and Different Transition MetalsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2003Rita Annunziata Abstract A new bifunctional ligand capable of promoting different stereoselective catalytic transformations in combination with different transition metals has been prepared by connecting with a spacer a bis(oxazoline) to dihydroquinidine; this ligand was employed in a one-flask procedure in which methyl (E)-3-(4-vinylphenyl)propenoate underwent first cyclopropanation at the electron-rich double bond and then dihydroxylation at the electron-poor alkene to afford a product containing four stereocenters with complete regiocontrol and high stereoselectivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] ChemInform Abstract: Catalytic Asymmetric Synthesis of R207910.CHEMINFORM, Issue 39 2010Yutaka Saga Abstract The first asymmetric synthesis of the potent anti-tuberculosis drug (VI) involves two key catalytic transformations: an enantioselective proton migration reaction of dihydroquinolinone (I) using an in situ generated yttrium catalyst, and a CuF-catalyzed highly diastereoselective allylation of the resulting quinolinone (II). [source] | ||||||||||