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Olefins
Kinds of Olefins Terms modified by Olefins Selected AbstractsTitelbild: High-Yielding Tandem Hydroformylation/Hydrogenation of a Terminal Olefin to Produce a Linear Alcohol Using a Rh/Ru Dual Catalyst System (Angew. Chem.ANGEWANDTE CHEMIE, Issue 26 201026/2010) Ein Volleyball fliegt von der akademischen zur industriellen Seite des Netzes als Symbol für die potenzielle Nützlichkeit eines neuen dualen Katalysatorsystems , einer Kombination aus Xantphos/[Rh(acac)(CO)2] und dem Shvo-Katalysator , auf beiden Gebieten. In der Zuschrift auf S.,4590,ff. beschreiben K. Nozaki et,al. die hoch effiziente Erzeugung von n -Undecanol aus Synthesegas mit diesem Katalysatorsystem. Das Eintopfverfahren umfasst eine rhodiumkatalysierte Hydroformylierung und eine rutheniumkatalysierte Hydrierung. [source] High-Yielding Tandem Hydroformylation/Hydrogenation of a Terminal Olefin to Produce a Linear Alcohol Using a Rh/Ru Dual Catalyst System,ANGEWANDTE CHEMIE, Issue 26 2010Kohei Takahashi Beim Test dualer Katalysatorsysteme für die Tandemsequenz aus Hydroformylierung und Hydrierung zur einstufigen Herstellung von n -Undecanol aus 1-Decen ergab die Kombination von Xantphos/[Rh(acac)(CO)2] mit dem Shvo-Katalysator 1 das beste Resultat (siehe Schema; acac=Acetylacetonat, DMA=N,N -Dimethylacetamid). Der Einsatz polarer Lösungsmittel verhindert die Bildung von Undecylformiat. [source] Unexpected Effects of Terminal Olefins on a Cooperative Recognition System that Implicate Olefin,Olefin Interactions,ANGEWANDTE CHEMIE, Issue 36 2009Rie Wakabayashi Dr. Überempfindlich: Mit einem neuen Verfahren, das auf dem Gastbindeverhalten allosterischer Wirtmoleküle beruht, gelang der hoch empfindliche Nachweis schwacher Olefin-Olefin-Wechselwirkungen (siehe Bild) [source] Dichloroketene,Chiral Olefin-Based Approach to Pyrrolizidines: Highly Stereocontrolled Synthesis of (+)-Amphorogynine A (VIII).CHEMINFORM, Issue 36 2003Caroline Roche Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: A Novel Approach for Mannich-Type Bases Having a Terminal Olefin: Zinc Triflate and Water-Promoted Cyclization/C,N Bond Cleavage Process.CHEMINFORM, Issue 16 2001Kaori Ishimaru Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] Osmabenzenes from Osmacycles Containing an ,2 -Coordinated OlefinCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2009Lei Gong Dr. Abstract Osmabenzenes can be easily synthesized from two ,2 -coordinated olefin osmacycles in the presence of benzonitrile by means of facile hydrogen-transfer conversions (see graphic). Mechanisms for the formation of osmabenzenes are proposed based on DFT calculations. Treatment of HCCC(CH3)(OH)CHCH2 with [OsCl2(PPh3)3] in dichloromethane yielded the ,2 -olefin-coordinated osmacycle [Os{CHC(PPh3)C(CH2)-,2 -CHCH2}Cl2(PPh3)2] (9). Transformations of osmacycle 9 by treatment with benzonitrile under various conditions have been investigated. Reaction of 9 with excess benzonitrile at room temperature afforded the dicationic osmacycle [Os{CHC(PPh3)C(CH2)-,2 -CHCH2}(PhCN)2(PPh3)2]Cl2 (11) by ligand substitution, which reacted further to the intramolecularly coordinated ,2 -allene complex [Os{CHC(PPh3)C(CH3)(,2 -CCH2)}(PhCN)2(PPh3)2]Cl2 (12). In contrast, heating a chloroform solution of 9 to the reflux temperature in the presence of excess benzonitrile generated osmabenzene [Os{CHC(PPh3)C(CH3)CHCH}(PhCN)2(PPh3)2]Cl2 (14). Complexes 11, 12 and 14 are in fact isomers. In the absence of excess benzonitrile, the isolated dicationic 12 and 14 readily dissociate the benzonitrile ligands in solution to produce the neutral complex [Os{CHC(PPh3)C(CH3)(,2 -CCH2)}Cl2(PPh3)2] (13) and the monocationic osmabenzene [Os{CHC(PPh3)C(CH3)CHCH}Cl(PhCN)(PPh3)2]BPh4 (15), respectively. Mechanisms for the formation of osmabenzene 14 from 11 and 12 are proposed based on DFT calculations. [source] Functionalisation of Polyolefins: Grafting of Phenol Groups on Olefin/5,7-Dimethylocta-1,6-diene CopolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 15 2003Marc Dolatkhani Abstract The grafting of phenol groups on ethylene/5,7-dimethylocta-1,6-diene copolymers and on ethylene/propylene/5,7-dimethylocta-1,6-diene terpolymers was performed, using two different modification procedures. An indirect route involving hydrochlorination followed by phenol insertion was found to be very effective for the terpolymers, and lead to a grafting phenol rate higher than 75%. However, if the phenol grafting is performed directly on a non-modified terpolymer, lower rates are obtained. When applied to the copolymers the procedures used were revealed to be less efficient. This fact might be related to the lower solubility of the ethylene/5,7-dimethylocta-1,6-diene copolymers (related to a higher crystallinity and a smaller diene content) when compared with the corresponding terpolymers. Although incomplete, the addition of a hindered phenol to the copolymer gave rise to a polymer that, when compared to polyethylene, presents a higher thermal-oxidative stability. Grafting of phenol on a hydrochlorinated ethylene/propylene/5,7-DMO terpolymer. [source] Repetitive Application of a Fluorous Chiral BINAP,Ru Complex in the Asymmetric Hydrogenation of OlefinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2007Joachim Horn Abstract A trisperfluoroalkylsilyl-modified (S)-BINAP ligand has been prepared and its pertinent Ru complex applied to the asymmetric hydrogenation of olefins. Efficient separation of the Ru catalyst by filtration and its reuse was achieved. Relative to the untagged complex with a Ru-leaching of 300 ppm, leaching into the product was low (1.6,4.9 ppm). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] 3,5-Bis(trifluoromethyl)phenyl Sulfones in the Julia,Kocienski Olefination , Application to the Synthesis of Tri- and Tetrasubstituted OlefinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2006Diego A. Alonso Abstract 3,5-Bis(trifluoromethyl)phenyl (BTFP) sulfones 8a,d are successfully employed in the modified Julia olefination reaction with carbonyl compounds employing phosphazene base P4- tBu at room temp. in THF, affording tri- and tetrasubstituted olefins in good yields. The Julia,Kocienski olefination between primary alkyl BTFP sulfones 8a,b and aromatic and aliphatic ketones affords the corresponding trisubstituted alkenes in good yields and low stereoselectivities. On the other hand, higher yields and stereoselectivities are obtained in the synthesis of trisubstituted olefins through the other approach, the coupling of secondary alkyl BTFP sulfones 8c,d with aliphatic, aromatic and ,,,-unsaturated aldehydes. For the first time, tetrasubstituted olefins are synthesized by means of the Julia,Kocienski protocol when the isopropyl BTFP sulfone 8c reacts with aliphatic and aromatic ketones, employing P4- tBu as base at THF reflux. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Carbodiazenylation of Olefins by Radical Iodine Transfer and Addition to Arenediazonium SaltsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2006Olga Blank Abstract Carbodiazenylation of olefins can be achieved with arenediazonium salts under reductive conditions. The method can be extended to aliphatic substituents when iodine compounds are present in the reaction mixture. Incorporation is achieved through a radical iodine transfer. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] New Functionalised Hydroxymethyl Ketones from the Mild and Chemoselective KMnO4 Oxidation of Chiral Terminal OlefinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2006Carlo Bonini Abstract Various terminal olefinic compounds are directly converted into the corresponding ,-hydroxy ketones in good yields by potassium permanganate oxidation. The reaction is also highly chemoselective in the presence of differently protected hydroxy groups and can be utilised for the preparation of polyfunctional compounds such as polyols. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] The Extraordinary Cocatalytic Action of Polymethylaluminoxane (MAO) in the Polymerization of Terminal Olefins by Metallocenes: Chemical Change in the Group 4 Metallocene Dimethyl Derivatives Induced by MAO,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2005John J. Eisch Abstract In the polymerization of olefins with Group 4 metallocene dichlorides or dimethyl derivatives as procatalysts the use of polymethylaluminoxane (MAO) as the cocatalyst, especially in extreme excess (102,103 times the metallocene equivalent), has been shown to have an extraordinary accelerating effect on the rate of olefin polymerization, when compared with the cocatalytic action of alkylaluminum halides. In attempts at explaining the greatly superior catalytic activity of MAO in olefin polymerization (the MAO conundrum), hypotheses have generally paralleled the steps involved in the cocatalytic action of RnAlCl3,n, namely the alkylation of Cp2MtCl2, ionization of Cp2Mt(R)Cl into the metallocenium cation, [Cp2Mt,R]+, and anion, [Rn,1AlCl4,n], and subsequent ion-pair separation. In order to understand any differences in catalytic action between such cocatalysts, we have studied the individual action of MAO (100 equiv.) and of MeAlCl2 (1,2 equiv.) on each of the Group 4 metallocene derivatives, Cp2TiCl2, Cp2ZrCl2, Cp2Ti(CH3)2 and Cp2Zr(CH3)2. With MeAlCl2 each of the metallocene derivatives appeared to form the cation, [Cp2Mt,CH3]+, with greater (Ti) or lesser (Zr) ease, because an alkyne such as diphenylacetylene was then found to insert into the Mt,CH3 bond stereoselectively. In striking contrast, treatment of each metallocene with MAO gave two reactions very different from MeAlCl2, namely a steady evolution of methane gas upon mixing and a finding upon hydrolytic workup that the diphenylacetylene present had undergone no insertion into the Mt,CH3 bond but instead had been reductively dimerized completely to (E,E)-1,2,3,4-tetraphenyl-1,3-butadiene. To account for this astonishing difference in chemical behavior between MAO and MeAlCl2 in their cocatalytic activation of Group 4 metallocenes to olefin polymerization, it is necessary to postulate a novel, unique sequence of reaction steps occurring between MAO and the metallocene. If one starts with the metallocene dichloride, then the free TMA present in the MAO would generate the Cp2Mt(CH3)2. This metallocene dimethyl derivative, complexed with an oligomeric MAO unit, would undergo a transfer-epimetallation with added olefin or acetylene to form a metallacyclopropane or metallacyclopropene, respectively. With added diphenylacetylene the resulting 2,3-diphenylmetallacyclopropene would be expected rapidly to insert a second alkyne to form the 2,3,4,5-tetraphenyl-1-metallacyclopentadiene. Simple hydrolysis of the latter intermediate would generate (E,E)-1,2,3,4-tetraphenyl-1,3-butadiene while alternative workup with D2O would give the 1,4-dideuterio derivative of this butadiene. Both such expectations were confirmed by experiment. In the case of added olefin, similar metallacyclopropane and metallacyclopentane intermediates should be produced until ring opening of the latter five-membered ring leads to an open-chain zwitterion, a process having ample precedent in the research of Gerhard Erker. The solution to the MAO conundrum then, namely the extraordinary cocatalytic activity of MAO in olefin polymerization by metallocenes, lies in the unique catalytic activation of the Group 4 metallocene dimethyl derivative, which occurs by transfer-epimetallation of the olefin monomer by the Cp2Mt(CH3)2,MAO complex. The most advantageous Lewis acidic sites in the MAO,oligomeric mixture for such metallocene,MAO complexation are suggested to be terminal Me2Al,O,AlMe, segments of an open-chain oligomer. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Syntheses of New Chiral Phosphane Ligands by Diastereoselective Conjugate Addition of Phosphides to Enantiomerically Pure Acceptor-Substituted Olefins from the Chiral PoolEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2005Burkhard Wiese Abstract A variety of new chiral phosphanes were prepared by highly diastereoselective additions of phosphanes to ,,,-unsaturated carbonyl compounds and related acceptor-substituted olefins derived from myrtenal as ex chiral pool source. Monophosphanes with astereogenic as well as stereogenic phosphorus are described. In addition diphosphanes were prepared by a highly diastereoselective double conjugate addition of a secondary diphosphane. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] The Synthesis and Reactivity of Group 4 Zwitterionic Complexes of the Type Mt+CH2AlCl3,: One-Component Stereoselective Polymerization and Oligomerization Catalysts for Olefins and AcetylenesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2004John J. Eisch Abstract A reinvestigation of the interaction of TiCl4 with 2 equiv. of Me3Al in toluene between ,78 °C and 25 °C over 24 h has now established that the ultimate black product obtained is an associated zwitterion of the type [Ti+,CH2,AlCl3,]n, supported by multinuclear NMR spectroscopy and mass spectrometric and gasometric analyses of the gases evolved (CH4, H2) upon its protolysis. Chemical reactions of the zwitterion have corroborated specific aspects of its proposed structure: 1) its methylene character, by its transformation of benzophenone into 1,1-diphenylethylene; 2) its divalent titanium content, by the substantial reductive dimerization of benzophenone to tetraphenylethylene, and 3) its Lewis acidic Ti center, by its catalytic isomerization of trans -stilbene oxide to 1,1-diphenylacetaldehyde. Similar individual reactions of ZrCl4 or HfCl4 with Me3Al have led to the analogous zwitterions [Zr+,CH2,AlCl3,]n and [Hf+,CH2,AlCl3,]n, respectively. These zwitterions of Ti, Zr and Hf have been proven to be capable of the cyclotrimerization and/or polymerization of acetylenes with varying facility, as evidenced by their catalytic action on 1-hexyne, phenylacetylene, di- n -butylacetylene, and diphenylacetylene. Furthermore, all three zwitterions were able to polymerize ethylene, without any added cocatalyst, with an activity following the order Zr > Ti > Hf. The Ti and Zr zwitterions effected the stereoselective polymerization of propylene to yield 50% of isotactic polymer, and all three catalysts induced the polymerization of 1-hexene to yield 85% (Zr, Hf) or 100% (Ti) of isotactic polymer. These oligomerizations and stereoselective polymerizations of acetylenes and olefins can be rationalized through a model for the active site resembling a three-membered metallacyclopropa(e)nium ion intermediate formed from the attack of the Group 4 metal zwitterion on the unsaturated hydrocarbon. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Reactivity and Selectivity of Captodative Olefins as Dienes in Hetero -Diels,Alder ReactionsHELVETICA CHIMICA ACTA, Issue 10 2008Rubén Sanabria Abstract The reactivity and selectivity of the the captodative olefins 1-acylvinyl benzoates 1a,1f and 3a as heterodienes in hetero -Diels,Alder reactions in the presence of electron-rich dienophiles is described. Heterodienes 1 undergo regioselective cycloaddition with the alkyl vinyl etherdienophiles 6a,b and 9 to give the corresponding dihydro-2H -pyrans 7, 8, and 10 under thermal conditions. The reactivity of these cycloadditions depends, to a large extent, on the electronic demand of the substituent in the aroyloxy group of the heterodiene. Frontier-molecular-orbital (FMO; ab initio) and density-functional-theory (DFT) calculations of the ground and transition states account for the reactivity and regioselectivity observed in these processes. [source] Insertion Reactions of 1,2-Disubstituted Olefins with an , -Diimine Palladium(II) ComplexHELVETICA CHIMICA ACTA, Issue 8 2006Carla Carfagna Abstract The migratory insertions of cis or trans olefins CH(X)CH(Me) (X,=,Ph, Br, or Et) into the metal,acyl bond of the complex [Pd(Me)(CO)(iPr2dab)]+ [B{3,5-(CF3)2C6H3}4], (1) (iPr2dab,=,1,4-diisopropyl-1,4-diazabuta-1,3-diene,=,N,N, -(ethane-1,2-diylidene)bis[1-methylethanamine]) are described (Scheme,1). The resulting five-membered palladacycles were characterized by NMR spectroscopy and X-ray analysis. Experimental data reveal some important aspects concerning the regio- and stereochemistry of the insertion process. In particular, the presence of a Ph or Br substituent at the alkene leads to the formation of highly regiospecific products. Moreover, in all cases, the geometry of the substituents in the formed palladacycle was the same as in the starting olefin, as a consequence of a cis addition of the Pd,acyl fragment to the CC bond. Reaction with CO and MeOH of the five-membered complex derived from trans-, -methylstyrene (=,[(1E)-prop-1-enyl]benzene) insertion, yielded the 2,3-substituted , -keto ester 9 with an (2RS,3SR)-configuration (Scheme,3). [source] The Origin of the High Enantioselectivity in Asymmetric Cyclopropanation of Unfunctionalized OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Yiying Zheng Abstract The mechanism of the asymmetric Simmons,Smith cyclopropanation for unfunctionalized olefins was investigated using density functional theory (DFT) methods. The calculated results of model reactions showed that the coordinated Lewis acidic zinc halide ZnX2 (X=Cl, I) and/or halomethylzinc halide XZnCH2X in the catalyst play an important role in the enantioselectivity. The catalyst not only forms the ring with the substance in the reaction centre, but also establishes two steric repulsions that can lead to an explanation for the high enantioselectivity. Hence, these results highlight some important insights for the prerequisites of an effective catalyst and a proper substrate towards high enantioselectivity for this kind of reaction. [source] A Thiourea-Oxazoline Library with Axial Chirality: Ligand Synthesis and Studies of the Palladium-Catalyzed Enantioselective Bis(methoxycarbonylation) of Terminal OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Ying-Xiang Gao Abstract We report herein the synthesis of novel chiral S,N-heterobidentate thiourea-oxazoline ligands and their application to palladium-catalyzed enantioselective bis(methoxycarbonylation)s of terminal olefins under mild conditions. Copper salts were found to play multiple roles in this reaction. Substituted 2-phenylsuccinates were obtained in >90% yield and up to 84% ee under optimized conditions. [source] Polymer-Supported Hantzsch 1,4-Dihydropyridine Ester: An Efficient Biomimetic Hydrogen Source for the Reduction of Ketimines and Electron-Withdrawing Group Conjugated OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Jun Che Abstract A polymer-supported Hantzsch 1,4-dihydropyridine ester was observed to be a useful selective reducing agent for the reduction of ketimines and electron-withdrawing conjugated olefins. The rate of the reduction of electron-withdrawing conjugated olefins is dependent on the nature of the conjugated substituents and could be enhanced by microwave irradiation. The reduction of (Z)-,-cyano-,-bromomethylcinnamates to cyclopropane derivatives using polymer-supported Hantzsch 1,4-dihydropyridine ester was found to proceed stereoselectively and in good yields. [source] Grafting of Molecularly Ordered Mesoporous Phenylene-Silica with Molybdenum Carbonyl Complexes: Efficient Heterogeneous Catalysts for the Epoxidation of OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Abstract Arenetricarbonyl complexes, or the general formula C6H4Mo(CO)3, were incorporated into crystal-like mesoporous phenylene-silica by liquid-phase deposition of molybdenum hexacarbonyl [Mo(CO)6]. By adjusting the reaction conditions, different molybdenum loadings of 1.5 and 5.9,wt% were obtained, which correspond to 3% and 14% of the phenylene contents. The texture properties of the materials as well as the nature of the surface-fixed complexes were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), N2 adsorption, FT-IR, UV-vis and MAS (13C, 29Si) NMR spectroscopy. The derivatized organosilicas were examined as catalyst precursors for the liquid-phase epoxidation of cis -cyclooctene, 1-octene, trans -2-octene and (R)-(+)-limonene at 55,°C, using tert -butyl hydroperoxide as the oxidant. For each olefin the corresponding epoxide was the only product detected. In the case of cyclooctene, the intrinsic reaction rates per surface molybdenum atom were similar for both Mo loadings (TOF,1150 mol,molMo,1,h,1), suggesting that the resultant materials act as single site epoxidation catalysts. Leaching tests and metal analyses of reaction solutions showed that the catalytic activity stemmed from the immobilized species and not from the leaching of active species into solution. The oxidation of limonene gave limonene oxide as the only product in 95% yield at 3,h, which reveals an outstanding regioselectivity to the epoxidation of the endocyclic double bond. [source] Iron-Catalyzed Epoxidation of Aromatic Olefins and 1,3-DienesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Kristin Schröder Abstract The combination of iron(III) chloride, pyridine-2,6-dicarboxylic acid and formamidine ligands allows for the epoxidation of styrenes and conjugated dienes in excellent chemoselectivity and yields. [source] Hydrogen/Deuterium Exchange Reactions of Olefins with Deuterium Oxide Mediated by the Carbonylchlorohydrido- tris(triphenylphosphine)ruthenium(II) ComplexADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Sunny Kai San Tse Abstract The catalytic properties of several ruthenium, osmium and rhodium hydride complexes for hydrogen/deuterium (H/D) exchange between olefins and deuterium oxide (D2O) were investigated. The most effective catalytic precursor was found to be the carbonylchlorohydridotris(triphenylphosphine)ruthenium(II) complex. Through H/D exchange between metal hydride and D2O, and reversible olefin insertion into an RuH(D) bond, protons attached to olefinic carbons and alkyl chains of olefins can all undergo H/D exchange with D2O. The catalytic reactions can be used to deuterate both terminal and internal olefins, for example, styrene, stilbene and cyclooctene. [source] An Efficient and Selective Epoxidation of Olefins with Novel Methyltrioxorhenium/(Fluorous Ponytailed) 2,2,-Bipyridine CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 8 2010Raffaele Saladino Abstract Novel complexes between methyltrioxorhenium (MTO) and bis(fluorous-ponytailed) 2,2,-bipyridines (bpy-Fn) were synthesized and used for the oxidation of alkenes with hydrogen peroxide under fluorous catalysis. High conversions and yields of the corresponding epoxides were obtained. [source] tert -Butanesulfinylphosphines: Simple Chiral Ligands in Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids to Electron-Deficient OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Feng Lang Abstract An efficient rhodium complex catalyst system was developed by using a class of simple tert -butanesulfinylphosphines as bidentate ligands, which solely bear sulfur chirality and combine the advantages of both sulfoxide and phosphine ligands. Excellent activities (in 0.5 hour, up to 99% yield) and enantioselectivities (up to 98% ee) were displayed in Rh-catalyzed asymmetric 1,4-additions under mild conditions. [source] One Step Synthesis of Chiral Olefins via Asymmetric Diamination and their Applications as Ligands for Rhodium(I)-Catalyzed 1,4-AdditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2010Xichao Hu Abstract A variety of acyclic chiral dienes were synthesized in a single step via palladium(0)-catalyzed asymmetric allylic and homoallylic CH diamination of terminal olefins. The applications of such simple dienes as steering ligands for rhodium(I)-catalyzed asymmetric 1,4-additions afforded the corresponding adducts in excellent yields and up to 85% ee. [source] Highly Enantioselective Iridium-Catalyzed Hydrogenation of Trisubstituted Olefins, ,,,-Unsaturated Ketones and Imines with Chiral Benzylic Substituted P,N LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Wei-Jing Lu Abstract The benzylic substituted P,N ligands, diphosphinobenzyloxazolines, showed their high catalytic activity as well as asymmetric induction in the iridium-catalyzed asymmetric hydrogenation of unfunctionalized alkenes, ,,,-unsaturated esters, allyl alcohols, ,,,-unsaturated ketones, and imines, providing the corresponding chiral products in high ee with high conversion. [source] DiPAMP's Big Brother "i- Pr-SMS-Phos" Exhibits Exceptional Features Enhancing Rhodium(I)-Catalyzed Hydrogenation of OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Michel Stephan Abstract Switching Knowles DiPAMP's {DiPAMP=1,2-bis[(o -anisyl)(phenyl)phosphino]- ethane} MeO groups with i- PrO ones led to the i- Pr-SMS-Phos {i- Pr-SMS-Phos=1,2-bis[(o -isoprop- oxyphenyl)(phenyl)phosphino]ethane} ligand which displayed a boosted catalyst activity coupled with an enhanced enantioselectivity in the rhodium(I)-catalyzed hydrogenation of a wide-range of representative olefinic substrates (dehydro-,-amido acids, itaconates, acrylates, enamides, enol acetates, ,,,-diarylethylenes, etc). The rhodium(I)-(i- Pr-SMS-Phos) catalytic profile was investigated revealing its structural attributes and robustness, and in contrast to the usual trend, 31P,NMR analysis revealed that its methyl (Z)-,-acetamidocinnamate (MAC) adduct consisted of a reversed diastereomeric ratio of 1.4:1 in favour of the most reactive diastereomer. [source] Efficient Functionalisation of Cubic Monovinylsilsesquioxanes via Cross-Metathesis and Silylative Coupling with Olefins in the Presence of Ruthenium ComplexesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Patrycja Abstract Monovinylheptaisobutylsilsesquioxane undergoes efficient cross-metathesis and silylative coupling with styrenes. Allyl derivatives were successfully tested in cross-metathesis in the presence of first generation Grubbs' catalyst, while heteroatom-substituted vinyl derivatives (vinyl ethers, 9-vinylcarbazole) efficiently undergo silylative coupling catalysed by ruthenium hydride complexes. Both reactions proceed highly stereoselectively and lead to nearly quantitative formation of E isomers. Only when vinyl ethers are used does the reaction lead to a mixture of stereoisomers. Atmospheric pressure photoionisation has been successfully used for recording mass spectra of the functionalised silsesquioxanes. [source] Aluminium Powder-Catalyzed Regio- and Stereoselective Aminobromination of ,,,-Unsaturated Carbonyl Compounds and Simple Olefins with the p -Toluenesulfonamide/ N -Bromosuccinimide (TsNH2 -NBS) SystemADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Zhan-Guo Chen Abstract The regio- and stereoselective aminobromination of ,,,-unsaturated carbonyl compounds and simple olefins catalyzed by elementary aluminium powder has been established by using p -toluenesulfonamide (TsNH2) and N -bromosuccinimide (NBS) as the nitrogen/bromine sources. The reaction was convenient to carry out with a loading of 1,mol% catalyst at room temperature without inert gas protection. This method provides an easy approach to trans vicinal haloamino derivatives of ,,,-unsaturated carbonyl compounds and simple olefins in high yields (up to 99.8%) and in excellent regio- and stereoselectivities. The electron-rich and electron-deficient olefins show significant differences in activity to the aminobromination reaction and give the opposite regioselectivities. Two possible pathways involving separately a bromonium or an aziridinium intermediate have been proposed. [source] Recyclable Polymer- and Silica-Supported Ruthenium(II)-Salen Bis-pyridine Catalysts for the Asymmetric Cyclopropanation of OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Christopher Abstract Homogeneous ruthenium(II)-salen bis-pyridine complexes are known to be highly active and selective catalysts for the asymmetric cyclopropanation of terminal olefins. Here, new methods of heterogenization of these Ru-salen catalysts on polymer and porous silica supports are demonstrated for the facile recovery and recycle of these expensive catalysts. Activities, selectivities, and recyclabilities are investigated and compared to the analogous homogeneous and other supported catalysts for asymmetric cyclopropanation reactions. The catalysts are characterized with a variety of methods including solid state cross-polarization magic-angle spinning (CP MAS) 13C and 29Si,NMR, FT-IR, elemental analysis, and thermogravimetric analysis. Initial investigations produced catalysts possessing high selectivities but decreasing activities upon reuse. Addition of excess pyridine during the washing steps between cycles was observed to maintain high catalytic activities over multiple cycles with no impact on selectivity. Polymer-supported catalysts showed superior activity and selectivity compared to the porous silica-supported catalyst. Additionally, a longer, flexible linker between the Ru-salen catalyst and support was observed to increase enantioselectivity and diastereoselectivity, but had no effect on activity of the resin catalysts. Furthermore, the polymer-supported Ru-salen-Py2 catalysts were found to generate superior selectivities and yields compared to other leading heterogeneous asymmetric cyclopropanation catalysts. [source] | |||||||||||||||||||||||||||||||