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Catalyst Loading (catalyst + loading)
Kinds of Catalyst Loading Selected AbstractsA Versatile Palladium/Triphosphane System for Direct Arylation of Heteroarenes with Chloroarenes at Low Catalyst Loading,ANGEWANDTE CHEMIE, Issue 37 2010David Roy Ein luftbeständiger Palladiumkatalysator mit dreizähnigem Phosphanligand aryliert elektronenreiche wie elektronenarme mehrfach substituierte Furane (X=O), Thiophene (X=S) und Pyrrole (X=NR5) sowie Thiazole direkt unter C-H-Aktivierung mit Chlorarenen (siehe Schema; DMAc=N,N -Dimethylacetamid, TBAB=Tetra- n -butylammoniumbromid). [source] Highly Enantioselective Conjugate Addition of Thioglycolate to Chalcones Catalyzed by Lanthanum: Low Catalyst Loading and Remarkable Chiral Amplification,ANGEWANDTE CHEMIE, Issue 25 2010Yonghai Hui Kleineree,große Wirkung: Mit dem Lanthan(III)-Komplex eines chiralen N,N,-Dioxids als Katalysator verlief die Titelreaktion hoch enantioselektiv und mit hohen Ausbeuten. Besonders bemerkenswert war die große asymmetrische Verstärkung: Das Produkt wurde mit 98,%,ee erhalten, wenn 1,Mol-% L/La(OTf)3 mit 2,%,ee für L eingesetzt wurde. Tf=Trifluormethansulfonyl. [source] ChemInform Abstract: Efficient One-Pot Suzuki,Miyaura Double Cross-Coupling Reactions Using Very Low Pd(PPh3)4 Catalyst Loading.CHEMINFORM, Issue 15 2010Almeqdad Y. Habashneh 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] ChemInform Abstract: Modified Palladium-Catalyzed Regioselective ortho-Arylation of sp2 C,H Bond Substrates with a Low Catalyst Loading.CHEMINFORM, Issue 22 2009Fan Yang 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] TMSCl-Mediated Catalytic Carbocupration of Alkynoates: An Unprecedented and Remarkable Effect of Catalyst Loading on Highly Selective Stereochemical Induction via a TMS-Allenoate Intermediate.CHEMINFORM, Issue 46 2004Michael P. Jennings Abstract For Abstract see ChemInform Abstract in Full Text. [source] Stille Reactions with Tetraalkylstannanes and Phenyltrialkylstannanes in Low Melting Sugar-Urea-Salt MixturesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2006Giovanni Imperato Abstract The transfer of simple alkyl groups in Stille reactions usually requires special solvents (HMPA) or certain organotin reagents (stannatranes, monoorganotin halides) to be efficient. Using low-melting mixtures of sugar, urea and inorganic salt as solvent, a fast and efficient palladium-catalyzed alkyl transfer with tetraalkyltin reagents was observed. The high polarity and nucleophilic character of the solvent melt promotes the reaction. Stille biaryl synthesis using electron-poor and electron-rich aryl bromides proceeds with quantitative yields in the sugar-urea-salt melt. Catalyst loading may be reduced to 0.001 mol,% and the catalyst melt mixture remains active in several reaction cycles. Showing the same or improved performance for Stille reactions than organic solvents and allowing a very simple work up, sugar-urea-salt melts are a non-toxic and cheap alternative reaction medium available in bulk quantities for the catalytic process. [source] Novel Metathesis Catalysts Based on Ruthenium 1,3-Dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidenes: Synthesis, Structure, Immobilization, and Catalytic ActivityCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2004Liangru Yang Dr. Abstract The synthesis of novel ruthenium-based metathesis catalysts containing the saturated 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene ligand, that is, [RuCl2(NHC){CH-2-(2-PrO)-5-NO2 -C6H3}] (1) and [Ru(CF3COO)2(NHC){CH-2-(2-PrO)-5-NO2 -C6H3}] (2) (NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) is described. Both catalysts are highly active in ring-closing metathesis (RCM) and ring-opening cross-metathesis (ROCM). Compound 1 shows moderate activity in enyne metathesis. Compound 2 is not applicable to enyne metathesis since it shows high activity in the cyclopolymerization of diethyl dipropargylmalonate (DEDPM). Poly(DEDPM) prepared by the action of 2 consists of 95,% five-membered rings, that is, poly(cyclopent-1-enevinylene)s, and 5,% of six-membered rings, that is, poly(cyclohex-1-ene-3-methylidene)s. The polymerization proceeds in a nonliving manner and results in polyenes with broad polydispersities (1.9,PDI,2.3). Supported analogues of 2 were prepared by immobilization on hydroxymethyl-Merrifield resin and a monolithic support derived from ring-opening-metathesis polymerization (ROMP). Catalyst loadings of 1 and 2.5,%, respectively, were obtained. Both supported versions of 2 showed excellent reactivity. With 0.24,2,% of the supported catalysts, yields in RCM and ROCM were in the range of 76,100,%. Leaching of ruthenium was low and resulted in Ru contaminations of the products of less than 0.000014,% (0.14 ppm). [source] Highly Efficient and Practical Pyrrolidine,Camphor-Derived Organocatalysts for the Direct ,-Amination of AldehydesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2010Pang-Min Liu Abstract A series of pyrrolidine,camphor-derived organocatalysts (1,4) were designed and synthesised. These organocatalysts were used for direct ,-amination of aldehydes with dialkyl azodicarboxylates to give the desired ,-aminated products in high chemical yields (up to 92,%) and with high to excellent levels of stereoselectivity (up to >99,% ee). The reactions proceeded rapidly (within 5 min) with low catalyst loading (5 mol-%) at ambient temperature. Enantioselective aminations of asymmetric ,,,-disubstituted aldehydes in the catalytic system were studied, with reasonable to high stereoselectivities (up to 75,% ee) being obtained. The utility of this methodology was demonstrated with the synthesis of derivatives of ,-amino-,-butyrolactone and a tetrasubstitutedcyclohexane-derived amino alcohol with high stereoselectivities. Transition models were proposed for the asymmetric ,-amination reactions; they involve hydrogen-bond interactions between the nucleophilic enamine formed in situ and the nitrogen source. [source] Alkyne Hydroarylations with Chelating Dicarbene Palladium(II) Complex Catalysts: Improved and Unexpected Reactivity Patterns Disclosed Upon Additive Screening,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2009Andrea Biffis Abstract Palladium(II) complexes with a ligand set made from a chelating N-heterocyclic dicarbene ligand and two weakly coordinating anions (generally introduced in situ upon addition of 2 equiv. of a suitable silver salt) were found to be very active and selective catalysts for the room-temperature hydroarylation of alkynes at low catalyst loading (0.1 mol-%). Moreover, the screening of various strong acids as reaction promoters revealed that both the strength of the acid and the coordinating ability of its conjugated base influence the catalytic performance. Most remarkably, the use of HBF4 together with a dicarbene Pd complex catalyst provides a dramatic change in the selectivity of the reaction, with the prevalent formation of a product stemming from the insertion of two molecules of alkyne into the aromatic C,H bond. The results presented herein highlight the fact that the dicarbene ligand, apart from stabilising the catalyst, is also able to enhance catalytic activity and, most notably, to steer the reaction selectivity towards novel products. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Enantioselective CpRu-Catalyzed Carroll Rearrangement , Ligand and Metal Source ImportanceEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2008David Linder Abstract The addition of unstabilized carbonyl nucleophiles to unsymmetrical allyl-metal fragments still represents a challenge to generate stereogenic centers enantio- and regioselectively. In this context, the decarboxylative Carroll rearrangement of allyl ,-keto esters is particularly interesting, since chiral ,,,-unsaturated ketones are obtained. Herein, we show that CpRu half-sandwich complexes can, with selected enantiopure pyridine-monooxazoline ligands, catalyze this transformation and afford complete conversions along with good levels of regioselectivity and enantioselectivity. Even more challenging (electron-poor) substrates react (up to 86,% ee, branched/linear ratio , 97:03). In addition, the use of an air-stable metal precursor, namely [CpRu(,6 -naphthalene)][PF6], allows the reaction to be carried out reproducibly evenin non-anhydrous THF with a catalyst loading as low as2 mol-%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Catalytic Asymmetric Alkylation of Aldehydes by Using TrialkylboranesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 26 2008Takahiro Ukon Abstract Triethylborane can be used in the asymmetric alkylation of aldehydes by using a 3-(3,5-diphenylphenyl)-H8 -BINOL-derived titanium(IV) catalyst in the presence of an excess amount of titanium tetraisopropoxide. The reaction proceeds with a low catalyst loading (2 mol-%), exhibiting high enantioselectivity for aromatic and unsaturated aldehydes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Metal-Containing Ionic Liquids as Efficient Catalysts for Hydroxymethylation in WaterEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2008Katharina Bica Abstract The iron-containing ionic liquid butylmethylimidazolium tetrachloroferrate (bmim-FeCl4) proved to be an efficient and recyclable catalyst for the hydroxymethylation of ,-keto esters using aqueous formaldehyde and a low catalyst loading of up to 0.1 mol-% without co-solvents or additional surfactants. An useful and high-yielding approach to hydroxymethylated keto esters as well as to 3-disubstitued butyrolactones via tandem hydroxymethylation,lactonization could thus be established.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] A Practical Gold-Catalyzed Route to 4-Substituted Oxazolidin-2-ones from N -Boc PropargylaminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2007Eun-Sun Lee Abstract AuI -catalyzed cyclization of N -Boc propargylamines into 4-alkylidene oxazolidin-2-ones is described. This modularapproach provides access to a variety of nonproteogenic 4-substituted oxazolidinones that are important in asymmetric synthesis and biological applications. The current flexible route is characterized by low catalyst loading, mild conditions, and operational simplicity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Palladium-Catalyzed Suzuki,Miyaura Cross-Coupling Using Phosphinous Acids and Dialkyl(chloro)phosphane LigandsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2006Christian Wolf Abstract The use of eleven palladium complexes having monomeric and ,-chloro-bridged dimeric structures and either bulky dialkyl- and diarylphosphinous acid ligands (POPd, POPd-Br, POPd1, POPd2, POPd6, POPd7, Ph1-Phoxide) or dialkyl(chloro)phosphane ligands (PXPd, PXPd2, PXPd6, PXPd7) for Suzuki,Miyaura coupling reactions has been evaluated. Screening and optimization of catalyst loading, solvent, temperature, and base showed that excellent results can be obtained with electron-deficient and electron-rich aryl iodides, bromides, and chlorides in the presence of 2.5 mol-% of palladium,phosphinous acid POPd, (tBu2POH)2PdCl2, in 1,4-dioxane using cesium carbonate as base. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Kinetics and mechanism of myristic acid and isopropyl alcohol esterification reaction with homogeneous and heterogeneous catalystsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2008Tuncer Yalçinyuva The reaction of myristic acid (MA) and isopropyl alcohol (IPA) was carried out by using both homogeneous and heterogeneous catalysts. For a homogeneously catalyzed system, the experimental data have been interpreted with a second order, using the power-law kinetic model, and a good agreement between the experimental data and the model has been obtained. In this approach, it was assumed that a protonated carboxylic acid is a possible reaction intermediate. After a mathematical model was proposed, reaction rate constants were computed by the Polymath* program. For a heterogeneously catalyzed system, interestingly, no pore diffusion limitation was detected. The influences of initial molar ratios, catalyst loading and type, temperature, and water amount in the feed have been examined, as well as the effects of catalyst size for heterogeneous catalyst systems. Among used catalysts, p -toluene sulfonic acid (p -TSA) gave highest reaction rates. Kinetic parameters such as activation energy and frequency factor were determined from model fitting. Experimental K values were found to be 0.54 and 1.49 at 60°C and 80°C, respectively. Furthermore, activation energy and frequency factor at forward were calculated as 54.2 kJ mol,1 and 1828 L mol,1 s,1, respectively. © 2008 Wiley Periodicals, Inc. 40: 136,144, 2008 [source] Hydrocarbon gases and oils from the recycling of polystyrene waste by catalytic pyrolysisINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2004Paul T. Williams Abstract The yield and composition of oils and gases derived from the pyrolysis and catalytic pyrolysis of polystyrene has been investigated. The pyrolysis and catalytic pyrolysis was carried out in a fixed bed reactor. Two catalysts were used, zeolite ZSM-5 and Y-zeolite and the influence of the temperature of the catalyst, the amount of catalyst loading and the use of a mixture of the two catalysts was investigated. The main product from the uncatalysed pyrolysis of polystyrene was an oil consisting mostly of styrene and other aromatic hydrocarbons. The gases were found to consist of methane, ethane, ethene, propane, propene, butane and butene. In the presence of either catalyst an increase in the yield of gas and decrease in the amount of oil produced was found, but there was significant formation of carbonaceous coke on the catalyst. Increasing the temperature of the Y-zeolite catalyst and also the amount of catalyst in the catalyst bed resulted in a decrease in the yield of oil and increase in the yield of gas. Copyright © 2004 John Wiley & Sons, Ltd. [source] Cyclopalladated Ferrocenylimine as Efficient Catalyst for the Syntheses of Arylboronate EstersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Lianhui Wang Abstract The cyclopalladated ferrocenylimine I and its phosphine adducts IIa,f were prepared and evaluated in the borylation of aryl halides. The tricyclohexylphosphine adduct IIb exhibited highly catalytic activity for the coupling of aryl and heteroaryl bromides containing various functional groups with low catalyst loading (2,mol%). Aryl and heteroaryl chlorides were smoothly converted into the corresponding boronates in the presence of the monophosphinobiaryl ligand (XPhos) adduct IIf. It was proposed that palladacycle was only a reservoir of the catalytically active species from the investigation on the reaction mechanism. [source] Thiosemicarbazone Salicylaldiminato-Palladium(II)-Catalyzed Mizoroki,Heck ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Guanlei Xie Abstract Four tridentate thiosemicarbazone salicylaldiminato-palladium(II) complexes of the general formula [Pd(saltsc-R)PPh3] [saltsc=salicylaldehyde thiosemicarbazone; R=H (1), 3- tert -butyl (2), 3-methoxy (3), 5-chloro (4)], have been evaluated as catalyst precursors for the Mizoroki,Heck coupling reaction between a variety of electron-rich and electron-poor aryl halides and olefins. The palladium complexes (0.1,1,mol% loading) were found to effectively catalyze these reactions with high yields being obtained when aryl iodides and aryl bromides were utilized. The effects of base, catalyst loading, reaction temperature and reaction time on the catalytic activity of the most active complex were also investigated. [source] Extremely Efficient Cross-Coupling of Benzylic Halides with Aryltitanium Tris(isopropoxide) Catalyzed by Low Loadings of a Simple Palladium(II) Acetate/Tris(p -tolyl)phosphine SystemADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Chi-Ren Chen Abstract Highly efficient coupling reactions of benzylic bromides or chlorides with aryltitanium tris(isopropoxide) [ArTi(O- i- Pr)3] catalyzed by a simple palladium(II) acetate/tris(p -tolyl)phosphine [Pd(OAc)2/ P(p -tolyl)3] system are reported. The coupling reactions proceed in general at room temperature employing low catalyst loadings of 0.02 to 0.2,mol%, affording coupling products in excellent yields of up to 99%. For benzylic bromides bearing strong electron-withdrawing cyano (CN) or trifluoromethyl (CF3) substituents, the reactions require a higher catalyst loading of 1,mol%, or the reactions are carried out at 60,°C. The catalytic system also tolerates (1-bromoethyl)benzene bearing ,-hydrogen atoms while using a catalyst loading of 1,mol% to afford the coupling product in a 70% yield. [source] Sulfonated N -Heterocyclic Carbenes for Pd-Catalyzed Sonogashira and Suzuki,Miyaura Coupling in Aqueous SolventsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010Sutapa Roy Abstract The reactions of the N,N, -diarylimidazolium and N,N, -diarylimidazolinium salts with chlorosulfonic acid result in the formation of the respective disulfonated N -heterocyclic carbene (NHC) precursors in reasonable yields (46,77%). Water-soluble palladium catalyst complexes, in situ obtained from the respective sulfonated imidazolinium salt, sodium tetrachloropalladate (Na2PdCl4) and potassium hydroxide (KOH) in water, were successfully applied in the copper-free Sonogashira coupling reaction in isopropyl alcohol/water mixtures using 0.2,mol% catalyst loading. The preformed (disulfonatedNHC)PdCl(cinnamyl) complex was used in aqueous Suzuki,Miyaura reactions at 0.1,mol% catalyst loading. The coupling protocol reported here is very useful for Sonogashira reactions of N - and S -heterocyclic aryl bromides and chlorides with aryl- and alkylacetylenes. [source] Resorcin[4]arene-Derived Mono- and Diphosphines in Suzuki Cross-CouplingADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Hani El Moll Abstract Three resorcin[4]arene cavitands (1,3) having either one or two resorcinolic C-2 atoms substituted by a CH2PPh2 podand arm were assessed in the Suzuki arylation of aryl bromides with phenylboronic acid. Using P:Pd ratios of 2:1 and operating in dioxane at 100,°C with a catalyst loading of 0.001,mol% resulted in highly efficient catalytic systems. For example, TOFs up to 34570 mol(converted ArBr),mol(Pd),1,h,1 were obtained with the proximally-disubstituted cavitand 3 when using 4-bromotoluene as substrate. The performance was shown to vary in the following order: monophosphine 1 Prolylprolinol-Catalyzed Asymmetric Michael Addition of Aliphatic Aldehydes to NitroalkenesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2010Dengfu Lu Abstract Several novel prolylprolinol catalysts have been designed and synthesized. This type of compound showed high catalytic efficiency on promoting the direct addition of unmodified aldehydes to nitroalkenes. Among the catalysts surveyed, the least bulky member (8d) exhibited the best performance on both efficiency and stereoselectivity, providing the products with up to 97% ee value with 1.5,5,mol% catalyst loading. Additionally, computational studies of the transition state have been conducted to explain the high diastereo- and enantioselectivity. [source] Bismuth Triflate-Catalyzed Addition of Allylsilanes to N -Alkoxycarbonylamino Sulfones: Convenient Access to 3-Cbz-Protected CyclohexenylaminesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Thierry Ollevier Abstract Bismuth triflate was found to be an efficient catalyst in the Sakurai reaction of allyltrimethylsilanes with N -alkoxycarbonylamino sulfones. The reaction proceeded smoothly with a low catalyst loading of Bi(OTf)3,4,H2O (2,5,mol%) to afford the corresponding protected homoallylic amines in very good yields (up to 96%). A sequential allylation reaction followed by ring-closing metathesis delivers 6,8 membered 3-Cbz-protected cycloalkenylamines. [source] Effect of Long Chain Fatty Acids on Organocatalytic Aqueous Direct Aldol ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Nobuyuki Mase Abstract In an organocatalyzed, aqueous direct aldol reaction, the addition of a long chain fatty acid (1,mol%) such as stearic acid or erucic acid improved the aldol product yield and the enantioselectivity with low catalyst loading (1,mol%). The small particle size of the emulsion (less than 1,,m) was a key to the enhanced reactivity as shown by dynamic light scattering (DLS) analyses. [source] Highly Enantioselective Michael Addition of ,-Substituted Cyano Ketones to ,,,-Unsaturated ,-Keto Esters using Bifunctional Thiourea-Tertiary Amine Catalysts: An Easy Access to Chiral DihydropyransADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Sheng-Li Zhao Abstract An asymmetric Michael addition of ,-substituted cyano ketones to ,,,-unsaturated ,-keto esters to form chiral dihydropyrans catalyzed by a series of ,-amino acid-derived thiourea-tertiary amines is presented. A novel tyrosine-derived thiourea catalyst was identified as the optimal catalyst providing the desired product in 91,95% yields and with 90,96% ee at a low catalyst loading of 2.0,mol%. The utility of the reaction was exemplified by facile conversion of the dihydropyran product into pharmaceutically useful dihydropyridine. [source] Room Temperature Lewis Base-Catalyzed Alumination of Terminal AlkynesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Yuhan Zhou Abstract An efficient and mild access to mixed dimethylalkynylaluminum reagents has been developed via a direct Lewis base-catalyzed alumination of terminal alkynes by trimethylaluminum. The use of bis(trimethylsilyl)methylamine enables the metalation at room temperature with only 1% of catalyst loading. [source] A Lutidine-Bridged Bis-Perimidinium Salt: Synthesis and Application as a Precursor in Palladium-Catalyzed Cross-Coupling ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Tao Tu Abstract A novel lutidine-bridged bis-perimidinium dibromide 3 was synthesized in quantitative yield from cheap commercial starting materials. The bisylidene prepared therefrom in situ upon deprotonation is a potent precatalyst in palladium-catalyzed Heck and Suzuki cross-coupling reactions under aerobic conditions, and is efficient even with a ppm scale catalyst loading. Its stronger ,-donor character is held to be responsible for its superior catalytic performance compared with imidazole- and benzimidazole-based analogues bearing the same skeleton precursors. [source] An Efficient Synthesis of Poly(ethylene glycol)-Supported Iron(II) Porphyrin using a Click Reaction and its Application for the Catalytic Olefination of AldehydesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Suman Abstract The first successful synthesis of poly(ethylene glycol) (PEG) immobilized iron(II) porphyrin using a copper-catalyzed azide-alkyne [3+2],cycloaddition is reported. In contrast to the existing methods for the synthesis of PEG-immobilized metalloporphyrins, the click method offers better catalyst loading under comparatively mild reaction conditions. The prepared complex 5 (PEG-C51H39FeN7O) was found to be an efficient catalyst for the selective olefination of aldehydes with ethyl diazoacetate in the presence of triphenylphosphine and afforded excellent olefin yields with high (E) selectivities. The PEG-supported catalyst 5 was readily recovered by precipitation and filtration and was recycled for up to ten runs without significant loss of activity. [source] The Ion Tag Strategy as a Route to Highly Efficient Organocatalysts for the Direct Asymmetric Aldol ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Marco Lombardo Abstract The installation of an imidazolium tag via acetate connection to the C-4 of cis -4-hydroxy- L -proline provides a highly efficient catalyst for the direct asymmetric aldol reaction, that works in a remarkably low catalyst loading (0.1,mol%) affording TONs up to 930 in the case of electron-poor aromatic aldehydes with ee up to >99%. [source] The First Catalytic Mannich-Type Reaction of N -Alkoxycarbonylamino Sulfones with Silyl EnolatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2006Thierry Ollevier Abstract Bismuth triflate was found to be an efficient catalyst in the Mannich-type reaction of silyl enolates with N -alkoxycarbonylamino sulfones. The reaction proceeded smoothly with a low catalyst loading of bismuth triflate (0.5,1.0 mol,%) to afford the corresponding protected ,-aminocarbonyl compound in very good yields (up to 96,%). [source]
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