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Simple Filtration (simple + filtration)
Selected AbstractsAcrolein Diethyl Acetal: A Three-Carbon Homologating Reagent for the Synthesis of ,-Arylpropanoates and Cinnamaldehydes by Heck Reaction Catalyzed by a Kaiser Oxime Resin Derived PalladacycleEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2008Emilio Alacid Abstract A polymer palladacycle derived from Kaiser oxime resin was used as a source of palladium(0) in the chemoselective Heck reaction of acrolein diethyl acetal with aryl halides under ligand-free conditions. The use of typical Heck conditions afforded 3-arylpropionic esters, and the process can be directed to the synthesis of cinnamaldehydes under Cacchi conditions. These processes take place with rather low loading of the catalyst, which can be recovered by simple filtration and reused for at least five runs without competitive dehalogenation. This is the first time that a supported palladium complex has been reused under Cacchi conditions. ICP-OES analyses of the Pd content of the crude products in both transformations indicated lower leaching for the esters than for the aldehydes in the range up to 0.08 ppm for the esters and 0.8 ppm for the aldehydes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Silica-Immobilized NHC,CuI Complex: An Efficient and Reusable Catalyst for A3 -Coupling (Aldehyde,Alkyne,Amine) under Solventless Reaction ConditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2008Min Wang Abstract A novel silica-immobilized NHC,CuI complex was developed and used as a highly efficient catalyst in the three-component coupling reactions of aldehydes, alkynes and amines (A3 -coupling). The reactions were applicable to aromatic and aliphatic aldehydes, alkynes and amines, and generated the corresponding propargylamines in good yields only in the presence of SiO2,NHC,CuI (2 mol-%) at room temp. under solvent-free reaction conditions. Moreover, the catalyst was quantitatively recovered from the reaction mixture by a simple filtration and reused for ten cycles with almost consistent activity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Quaternary Ammonium-Supported Scavenger Reagents for Acids and ElectrophilesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2004Noha Ghanem Abstract The present article describes how we devised new quaternary ammonium-supported quench reagents (TAMA-Cl and BAX-sulfate) for scavenging acids and excess electrophiles from crude reaction mixtures. TAMA-Cl is liquid at room temperature, but is very glutinous and has to be used in aqueous solution. It removes unchanged electrophiles very efficiently. An aqueous preparation of TAMA-Cl may be easily added in automated syntheses, and high-throughput phase-separation techniques should allow purification of scavenger-containing reaction mixtures. However, workup with TAMA-Cl is more complex than simple filtration. Recognizing this major advantage of solid-phase syntheses, we designed BAX-sulfate, a highly crystalline scavenger reagent that allows reaction workup to be simplified to a single filtration and evaporation of solvent. BAX-sulfate reacts with electrophiles, quenches acids and precipitates quantitatively when diethyl ether is added. It even precipitates from methanol solutions. With BAX-sulfate the workup stage uses simple filtration to make crude separations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Rhodium Fluoroapatite Catalyzed Conjugate Addition of Arylboronic Acids to ,,, -Unsaturated Carbonyl CompoundsHELVETICA CHIMICA ACTA, Issue 10 2008Lakshmi Kantam, Mannepalli Abstract Rhodium fluoroapatite (RhFAP) is an efficient catalyst for conjugate addition of organoboron reagents to ,,, -unsaturated carbonyl compounds. A variety of arylboronic acids and ,,, -unsaturated carbonyl compounds were converted to the corresponding conjugate-addition products, demonstrating the versatility of the reaction. The reaction is highly selective. RhFAP was recovered quantitatively by simple filtration, and reused for four cycles. [source] Immobilization of MacMillan Imidazolidinone as Mac-SILC and its Catalytic Performance on Sustainable Enantioselective Diels,Alder CycloadditionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Hisahiro Hagiwara Abstract MacMillan's imidazolidinone catalyst was immobilized as a supported ionic liquid catalyst (Mac-SILC) in the pores of silica gel with the aid of an ionic liquid , 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The heterogenized organocatalyst was utilized for the enantioselective Diels,Alder reaction of cyclopentadiene and cinnamaldehyde, recovered by simple filtration and subsequent evacuation, and repeatedly used up to six times in 81% average chemical yield, 87% ee for endo - and 80% ee for exo -products. The Mac-SILC was effective for a variety of substrates. [source] Efficient Aerobic Oxidation of Alcohols using a Hydrotalcite-Supported Gold Nanoparticle CatalystADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Takato Mitsudome Abstract Hydrotalcite-supported gold nanoparticles (Au/HT) were found to be a highly efficient heterogeneous catalyst for the aerobic oxidation of alcohols under mild reaction conditions (40,°C, in air). This catalyst system does not require any additives and is applicable to a wide range of alcohols, including less reactive cyclohexanol derivatives. This Au/HT catalyst could also function in the oxidation of 1-phenylethanol under neat conditions; the turnover number (TON) and turnover frequency (TOF) reached 200,000 and 8,300,h,1, respectively. These values are among the highest values compared to those of other reported catalyst systems at high conversion. Moreover, the Au/HT can be recovered by simple filtration and reused without any loss of its activity and selectivity. [source] Improved Suzuki,Miyaura Reactions of Aryldiazonium Salts with Boronic Acids by Tuning Palladium on Charcoal Catalyst PropertiesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009François-Xavier Felpin Abstract An improved Suzuki,Miyaura cross-coupling reaction of aryldiazonium tetrafluoroborates with boronic acids catalyzed by a highly active palladium catalyst supported on charcoal is described as an extremely practical and efficient protocol. A properties-activity study of various catalysts clearly established that the optimal catalytic activity was obtained with palladium nanoparticles having a low oxidation degree and uniformly dispersed on the charcoal. The optimized reaction conditions allow the cross-coupling to proceed at room temperature without any base and ligand in technical grade methanol. Although the catalyst could not be recycled, the low palladium contamination of the solvent and product after a simple filtration of the palladium on charcoal (Pd/C) renders the present protocol competitive and safer for the environment compared to more conventional homogeneous conditions. We have highlighted the efficiency of this novel protocol by a short synthesis of the fungicide Boscalid®. [source] Cooperative Catalysis in the Hydrolytic Kinetic Resolution of Epoxides by Chiral [(salen)Co(III)] Complexes Immobilized on Gold ColloidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2008Thomas Belser Abstract Chiral salen ligands were incorporated into self-assembled thiolate monolayers (SAMs) on gold colloids. Treatment of the immobilized ligand with Co(OAc)2,4,H2O yielded the corresponding [(salen)Co(II)] complex, and aerobic oxidation in the presence of triflic acid afforded the catalytically active [(salen)Co(III)] complex. Functionalized gold colloids with a diameter of 3.4,nm, coated with a mixed monolayer of n -octanethiolates and thiolates with chiral [(salen)Co(III)] end groups were studied as catalysts in the hydrolytic kinetic resolution (HKR) of hexene-1-oxide. Extremely high selectivitiy and significant rate acceleration relative to homogeneous monomeric catalysts were observed. Recovery of the immobilized catalyst was accomplished by simple filtration, and catalyst reoxidation and repeated recycling (seven times) was possible with no loss of reactivity or enantioselectivity. [source] Fluorapatite-Supported Palladium Catalyst for Suzuki and Heck Coupling Reactions of HaloarenesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2007M. Lakshmi Kantam Abstract A fluorapatite-supported palladium catalyst (PdFAP) was synthesized by treatment of fluorapatite (prepared by incorporating the basic species fluoride ion into apatite in situ by co-precipitation) with bis(benzonitrile)palladium(II) chloride in acetone. The catalyst displayed high catalytic activity for Suzuki coupling of aryl iodides and bromides with boronic acids at room temperature and chloroarenes at 130,°C in the presence of tetrabutylammonium bromide to give biaryls in excellent yields. Heck olefination of chloroarenes was also successfully carried out by this catalyst. PdFAP was recovered quantitatively by simple filtration and reused with consistent activity. PdFAP was well characterized by XRD, FTIR, XPS, ICP-AES, CO2 TPD and CHN elemental analysis. [source] Preparation, Characterization and Catalytic Properties of Polyaniline-Supported Metal ComplexesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 12-13 2006Boyapati Abstract Polyaniline-supported Sc, In, Pd, Os and Re catalysts were prepared by using a simple protocol and the thus prepared catalysts were well characterized using FTIR, XPS, UV-Vis/DRS, TGA-DTA. All the catalysts were successfully employed in a wide range of organic transformations such as cyanation and allylation of carbonyl compound, Suzuki coupling of aryl halides and boronic acids, and, most importantly, in asymmetric dihydroxylation of olefins to afford optically active vicinal diols. All the catalysts were separated from the reaction mixture by simple filtration and reused with consistent activity for five cycles without noticeable leaching of metal from the support. [source] Nanocrystalline Magnesium Oxide-Stabilized Palladium(0): An Efficient and Reusable Catalyst for Suzuki and Stille Cross-Coupling of Aryl HalidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2005Kantam, M. Lakshmi Abstract A nanocrystalline magnesium oxide-stabilized palladium(0) catalyst is prepared by counterion stabilization of PdCl42, with nanocrystalline MgO followed by reduction. This ligand-free heterogeneous nanocrystalline MgO-stabilized nanopalladium [NAPMgPd(0)] catalyst using the basic MgO in place of basic ligands exhibits excellent activity in Suzuki and Stille cross-coupling of haloarenes (chloro, bromo and iodo) to afford the unsymmetrical biaryls. The catalyst is quantitatively recovered by simple filtration and reused for four cycles with almost consistent activity. [source] A Novel Microencapsulated Osmium Catalyst Using Cross-Linked Polystyrene as an Efficient Catalyst for Asymmetric Dihydroxylation of Olefins in WaterADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005Tasuku Ishida Abstract A novel microencapsulated osmium catalyst (PSresin-MC Os) was developed using cross-linked polystyrene. The concept of this method may go beyond that of microencapsulation. The catalyst was successfully used in asymmetric dihydroxylation in water, and it was recovered quantitatively by simple filtration and reused several times without loss of activity. The shape of the catalyst was maintained even after several uses. Moreover, no leaching of the Os component was detected. [source] Polymer-Supported Bisacetoxybromate(I) Anion ,-An Efficient Co-Oxidant in the TEMPO-Mediated Oxidation of Primary and Secondary AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2003Marco Brünjes Abstract A polymer-bound reagent for the efficient oxidation of primary alcohols to aldehydes and secondary alcohols to ketones in the presence of a catalytic amount of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) is described. The oxidation process is particular mild and allows one to prepare aldehydes with ,-chirality without racemization. This also includes the synthesis of ,-aminoaldehydes. In most cases, work-up of this heavy metal-free oxidation is achieved by simple filtration followed by removal of the solvent. Insight into the role of the bromate(I) anion in the oxidation process was gained from the TEMPO-mediated oxidation of benzaldehyde in the presence of the hypochlorite anion loaded on an anion exchange resin. [source] An improved practical Pd/C-catalyzed Sonogashira cross-coupling reaction for the synthesis of liquid crystals of trans-cyclohexyltolansAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2010Hongyong Shang Abstract An improved practical synthesis of liquid crystals of trans-cyclohexyltolans by Sonogashira cross-coupling reaction of 1-iodo-4-(trans-4-alkylcyclohexyl)benzene with aromatic terminal alkynes in the presence of Pd/C (palladium on activated carbon) as low as 0.03 mol% of Pd and CuI (2 mol%) in a mixture solvent of acetone,water (5:2 in volume) is described. The liquid crystals could be obtained in high yields as a solid with excellent purity by simple filtration, and the filtrate could be reused several times while still retaining high catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd. [source] Bifunctional Heterogeneous Catalysis of Silica,Alumina-Supported Tertiary Amines with Controlled Acid,Base Interactions for Efficient 1,4-Addition ReactionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 41 2009Ken Motokura Dr. Abstract We report the first tunable bifunctional surface of silica,alumina-supported tertiary amines (SA,NEt2) active for catalytic 1,4-addition reactions of nitroalkanes and thiols to electron-deficient alkenes. The 1,4-addition reaction of nitroalkanes to electron-deficient alkenes is one of the most useful carbon,carbon bond-forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA-supported amine (SA,NEt2) catalyst enabled selective formation of a double-alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA,NEt2 catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA,NEt2 catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron-deficient alkenes. The solid-state magic-angle spinning (MAS) NMR spectroscopic analyses, including variable-contact-time 13C cross-polarization (CP)/MAS NMR spectroscopy, revealed that acid,base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid,base interactions. [source] Synthesis of Large Ring Macrocycles (12,18) by Recyclable Palladium-Complexed Dendrimers on Silica Gel Catalyzed Intramolecular Cyclocarbonylation ReactionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2007Shui-Ming Lu Dr. Abstract Intramolecular cyclocarbonylation reactions with palladium-complexed dendrimers on silica gel as catalysts are very effective for the synthesis of twelve- to eighteen-membered ring macrocycles. This process can tolerate a wide variety of functional groups, including halide, ether, ketone, and ester. The heterogeneous dendritic catalysts facilitate excellent substrate reactivity, affording oxygen-, nitrogen-, or sulfur-containing tricyclic heterocycles in 70,92,% yields. Importantly, these systems are easily recovered by simple filtration and reused several times with only a slight loss of activity. [source] Homo-coupling of Aryl Iodide and Bromide Catalyzed by Immobilized Palladium with a Bidentate Nitrogen LigandCHINESE JOURNAL OF CHEMISTRY, Issue 10 2009Xiaofang Chen Abstract The immobilized palladium onto organic-inorganic hybrid material, which contains bidentate nitrogen ligands, was a very effective catalyst for homo-coupling of aryl iodide and bromide. The protocol involved the use of N,N -dimethylacetamide as a solvent, and n -tributylamine as a base. The reaction generated the corresponding homo-coupling products in good to excellent yields at low catalyst loading (0.20 mol%). Furthermore, the silica-supported palladium catalyst could be recovered and recycled by a simple filtration of the reaction solution and used for five consecutive trials without loss of its activity. [source] Polystyrene-supported Palladium(II) Ethylenediamine Complex: A Recyclable Catalyst for the Syntheses of 2-Benzyl-imidazo[2,1- b][1,3]benzothiazoles by Sonogashira ReactionCHINESE JOURNAL OF CHEMISTRY, Issue 2 2009Mohammad BAKHERAD Abstract The polymer-supported palladium(II) ethylenediamine complex was used as a catalyst for the heterocyclization during Sonogashira reaction between a substituted phenyl iodide and 2-amino-3-(2-propynyl)-1,3-benzothiazolium bromide, which could readily be recovered from the reaction medium by a simple filtration, and reused without a significant loss in its activity. [source] Asymmetric aldol reactions catalyzed by efficient and recyclable silica-supported proline-based peptidesCHIRALITY, Issue 4 2009Jincan Yan Abstract A series of silica-supported proline-based peptides were synthesized and applied as catalysts for direct asymmetric intermolecular aldol reactions. Among these, a peptide with two L -proline units was found to be the most efficient one for the asymmetric aldol reactions between acetone and aromatic aldehydes. The reactions generated the corresponding products with satisfactory isolated yields (up to 97%) and enantiomeric excesses (up to 96%) in the presence of this catalyst (5 mol %). Furthermore, the silica-supported organocatalyst could be recovered and recycled by a simple filtration of the reaction solution and used for five consecutive trials without loss of its reactivity. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||