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Catalysis
Kinds of Catalysis Terms modified by Catalysis Selected AbstractsPhotoelectro-Synergistic Catalysis at Ti/TiO2/PbO2 Electrode and Its Application on Determination of Chemical Oxygen DemandELECTROANALYSIS, Issue 22 2006Jiaqing Li Abstract In this paper, photoelectro-synergistic catalysis oxidation of organics in water on Ti/TiO2/PbO2 electrode was investigated by the method of electrochemistry. Furthermore, the results were compared with those obtained from photocatalysis and electrocatalysis. The method proposed was applied to determine the chemical oxygen demand (COD) value, Ti/TiO2/PbO2 electrode functioning as the work electrode during the process. It was shown that the method of photoelectro-synergistic catalysis had lower detection limit and wider linear range than the methods of electroassisted photocatalysis and electrocatalysis. The results obtained by the proposed method and conventional one were compared by carrying out the experiment on 8 wastewater samples. The correlation of the results using different methods was satisfactory and the relative bias was below ±6.0%. [source] Nickel Complexes with N2O Donor Ligands: Syntheses, Structures, Catalysis and Magnetic StudiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2007Jishnunil Chakraborty Abstract Two new terephthalato-bridged tetranuclear polymeric NiII complexes, namely [Ni4L41(,-tp-,4 -O)(H2O)2(,-tp-,2 -O)]·2C2H5OH·CH3OH·3H2O (1) and [Ni4L42(,-tp-,4 -O)(H2O)2(,-tp-,2 -O)]·3H2O (2) [L1 = N -(3-aminopropyl)-5-bromosalicylaldimine and L2 = N -(3-aminopropyl)salicylaldimine], are reported along with the syntheses and structures of the dicyanoargentate-bridged polymeric complexes [Ni(L1)(H2O){Ag(CN)2}], (3) and [Ni(L3)(MeOH){Ag(CN)2}], (4) [L3 = N -(3-amino-2,2-dimethylpropyl)-5-bromosalicylaldimine]. All four complexes are found to be effective heterogeneous catalysts for the epoxidation of alkenes such as styrene, ,-methylstyrene and cyclohexene in the presence of tert -butyl hydroperoxide. The variable-temperature magnetic susceptibility measurements (300,2 K) of complex 1 show a fair degree of antiferromagnetic coupling between the NiII centers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Liquid Crystal Imidazolium Salts: Towards Materials for Catalysis and Molecular ElectronicsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2007Jean-Moïse Suisse Abstract 1,3-Bis(4-alkyloxyphenyl)-3H -imidazol-1-ium trifluoromethanesulfonates, alkyl = CH3(CH2)n,1, n = 8, 10, 12, 14 and 16, can be derived from the analogous 4-alkyloxyphenylamines. These imidazolium salts exhibit a lamellar liquid-crystal mesophase between 99 °C and 191 °C. The smectic-A phase was fully characterised by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. We report also the synthesis, lamellar crystal structure and catalytic activity of the PdII complex of the (deprotonated) carbene form of one of these salts. In addition, we measured the charged carrier mobilities in the mesophase.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Bis(phosphinimino)methanides as Ligands in Divalent Samarium Chemistry: Synthesis, Structures and CatalysisEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2007Michal Wiecko Abstract The reaction of K{CH(PPh2NSiMe3)2} with samarium diiodide in a 1:1 molar ratio in thf affords the corresponding divalent samarium complex [{(Me3SiNPPh2)2CH}Sm(,-I)(thf)]2 (1), whereas treatment of K{CH(PPh2NSiMe3)2} with samarium diiodide in a 2:1 molar ratio in thf gives the homoleptic complex [{(Me3SiNPPh2)2CH}2Sm] (2). When 1 is treated with KNPh2 in toluene in a 2:1 molar ratio the mixed dimeric compound [({(Me3SiNPPh2)CH}2Sm)2(,-I)(,-NPh2)] (3) is obtained. The single-crystal X-ray structures of all these complexes have been determined. [{(Me3SiNPPh2)2CH}Sm(,-I)(thf)]2 has also been successfully used as a catalyst for the polymerization of ,-caprolactone. Good activities and molecular masses are observed with this catalyst.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Monophosphanylcalix[6]arene Ligands: Synthesis Characterization, Complexation, and Their Use in CatalysisEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2006Yasushi Obora Abstract Novel phosphanylcalix[6]arenes having mono- O -diphenylphosphanylmethyl (3) and mono- O -(4-diphenylphosphanylphenyl)methyl substituents (5) have been synthesized. The structures of these monophosphanylcalix[6]arenes were determined by NMR spectroscopy, mass spectrometry, and X-ray crystal structure analysis. The X-ray structure reveals that 3 adopts a flattened 1,2,3-alternate conformation in the crystalline state, while the NMR spectra show that 3 and 5 have a cone conformation in solution. Structure optimization and energy calculations for 3 and 5 at the B3LYP/LANL2DZ-CONFLEX5/MMFF94s level of theory show that the cone conformation is slightly more stable than the 1,2,3-alternate conformation by 0.36 kcal,mol,1 for 3 and 0.96 kcal,mol,1 for 5. Complexation of 3 with [PtCl2(COD)] and [Rh(COD)2]BF4 gives cis -coordinated [PtCl2(3)2] and [Rh(COD)(3)2]BF4, respectively. The X-ray analysis of [PtCl2(3)2] shows that 3 adopts a cone conformation upon complexation. Combination of 3 and 5 with [Rh(COD)2]BF4 provides an active catalyst for the hydroformylation of a variety of terminal alkenes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Preparation of Optically Active ,-Amino[3]ferrocenophanes , Building Blocks for Chelate Ligands in Asymmetric CatalysisEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2003Patrick Liptau Treatment of 1,1,-diacetylferrocene (4) with dimethylamine and TiCl4 yielded the unsaturated dimethylamino-substituted [3]ferrocenophane product 5. Its catalytic hydrogenation gave the corresponding saturated [3]ferrocenophane system 6 (trans/cis , 7:1). The rac -[3]ferrocenophane amine 6 was partially resolved (to ca. 80% ee) by means of L - or D - O,O, -dibenzoyltartrate salt formation. Treatment of 4 with the pure (R)- or (S)-methyl(1-phenylethyl)amine (8)/TiCl4 gave the corresponding optically active unsaturated [3]ferrocenophane amines (R)-(+)- 9 and (S)-(,)- 9, respectively. Their catalytic hydrogenation again proceeded trans -selectively, giving the corresponding saturated diastereomeric [3]ferrocenophane amines (1R,3R,5R)- 10a and (1S,3S,5R)- 10b [starting from (R)- 9], their enantiomers ent - 10a and ent - 10b were obtained from (S)- 9, but with a poor asymmetric induction (10a/10b < 2:1). Quaternization of 6 (CH3I) followed by amine exchange using (R)- or (S)-methyl(1-phenylethyl)amine (8), respectively, proceeded with overall retention. Subsequent chromatographic separation gave the pure diastereoisomers (1R,3R,5R)- 10a and (1S,3S,5R)- 10b [from (R)- 8, ent - 10a and ent - 10b from (S)- 8] in > 60% yield. Subsequently, the benzylic (1-phenylethyl) auxiliary was removed from the nitrogen atom by catalytic hydrogenolysis to yield the enantiomerically pure (> 98%) ([3]ferrocenophanyl)methylamines (1R,3R)- 11 and (1S,3S)- 11, respectively, which were converted into the corresponding dimethylamino-substituted [3]ferrocenophanes (1R,3R)- 6 and (1S,3S)- 6. Each enantiomer from the following enantiomeric pairs was isolated in its pure form and characterized by X-ray diffraction: (R)- 9/(S)- 9; (1R,3R,5R)- 10a/(1S,3S,5S)- 10a; (1R,3R,5S)- 10b/(1S,3S,5R)- 10b; (1R,3R)- 11/(1S,3S)- 11. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Atom-Efficient Vinylic Arylations with Triarylbismuths as Substoichiometric Multicoupling Reagents under Palladium CatalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Maddali L. N. Rao Abstract The first atom-efficient arylation of vinylic iodides was achieved by using triarylbismuths as substoichiometric multicoupling reagents under palladium catalysis. Vinylic iodides were efficiently coupled with electronically divergent triarylbismuths to furnish the corresponding arylated products in short reaction times. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Gold(I) Catalysis: Selective Synthesis of Six- or Seven-Membered Heterocycles from Epoxy AlkynesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2009Lun-Zhi Dai Abstract Gold(I)-catalyzed intramolecular cycloisomerization of ketone-substituted epoxides with alkynes to six- or seven-membered heterocyclic compounds is firstly introduced in this paper. This procedure involves a cascade isomerization of the ketone-substituted epoxides into 1,3-diketones in the presence of a Lewis acid and subsequent gold(I)-catalyzed selective intramolecular addition of an oxygen or a carbon nucleophile to the alkynes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Preparation of Triaryl- and Triheteroarylmethanes under Ytterbium Triflate Catalysis and Solvent-Free ConditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2009Salvatore Genovese Abstract Triaryl- and triheteroarylmethanes have been synthesized in very good yield under solvent-free conditions from differently substituted aldehydes and 2-methylfuran or methoxybenzene in the presence of Yb(OTf)3 as catalyst. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Catalysis by Ionic Liquids: Significant Rate Acceleration with the Use of [pmIm]Br in the Three-Component Synthesis of DithiocarbamatesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2008Brindaban C. Ranu Abstract An easily accessible neutral ionic liquid, 1-methyl-3-pentylimidazolium bromide, promoted a one-pot three-component condensation of an amine, carbon disulfide, and an activated alkene/dichloromethane/epoxide to produce the corresponding dithiocarbamates in high yields at room temperature. The reactions are very fast in ionic liquids relative to those in other reaction media. These reactions do not require any additional catalyst or solvent. The ionic liquid can be recovered and recycled for subsequent reactions. A plausible mechanism is suggested. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Highly Selective Preparation of a Chiral Quaternary Allyl Aryl Piperidinedione by Palladium-Catalyzed Asymmetric Allylation Under Solid,Liquid Phase-Transfer CatalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 36 2007Audrey Nowicki Abstract The combination of a chiral palladium catalyst and a solid,liquid phase-transfer catalyst provides an effective method for the chemo- and enantioselective preparation of the chiral quaternary center of an allyl aryl piperidinedione. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Ferrocenyliminophosphites as Easy-to-Modify Ligands for Asymmetric CatalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2007Konstantin N. Gavrilov Abstract Several N,P bidentate phosphite-type ligands derived from readily available ferrocene-based iminoalcohols were successfully used in Rh-catalysed hydrogenations and Pd-catalysed allylic substitutions of a variety of substrates. Moderate-to-high catalytic activities under standard conditions were observed, and the enantiomeric excess of the products were up to 97,%. Results obtained under systematic variation of the ligand parameters indicate that the enantioselectivity is largely determined by the nature of the phosphocentre and also by the substituent in the C*HN-fragment. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Concave Pyridines for Bifunctional Acid,Base Catalysis,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2007Timo Liebig Abstract Two bifunctional concave acid,base catalysts, 1 and 2, have been synthesized starting from 2,6-dibromopyridine (9) and 2,6-bis(,-alkenyloxy)phenylboronic acids 8 and 10 which end up as bridgeheads in final bimacrocycles 1 and 2. One bridgehead contained an additional substituent in the 4-position. The respective protected 4-hydroxymethyl-substituted phenylboronic acids 8 were synthesized from 4-bromo-3,5-dihydroxybenzoic acid (3) in five steps. 4-Unsubstituted boronic acid 10 and 4-substituted boronic acid 8 were then attached to 9 by subsequent Suzuki couplings to give tetra-,-alkenes 12. By ring-closing metathesis of 12, bimacrocyclic dienes 13 and 17 were formed. After deprotection of the 4-hydroxymethyl group of one bridgehead, a 3-hydroxybenzoate was coupled to 14 to give ester 15 which gave bifunctional acid,base catalyst 1 upon hydrolysis. Analogously, homologue 2 was synthesized, but before coupling the bimacrocycle to the benzoate, tetraene 14 was hydrogenated to 18. Acidic and basic centers in 1 (49,% from 9) and 2 (19,% from 9) are at least 5 Å apart.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Gold Catalysis: Alkylideneoxazolines and -oxazoles from Intramolecular Hydroamination of an Alkyne by a TrichloroacetimidateEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2006A. Stephen K. Hashmi Abstract Several propargylic trichloroacetimidates have been prepared and their reactions with gold catalysts studied. Only with the propargyl and the 1-methylpropargyl substituent was a selective cyclization observed; with gold(III) chloride in acetonitrile only the product of a fast hydroamination to 4-methylene-4,5-dihydrooxazoles was obtained, in chloroform the slower subsequent aromatization could not be prevented which delivered the oxazoles after long reaction times. Up to 3333 turnovers could be reached. With gold(I) catalysts in chloroform or dichloromethane selective hydroamination to 4-methylene-4,5-dihydrooxazoles without subsequent aromatization was exclusively observed. The gold(I) catalysts also allowed chemoselective cycloisomerization of N -propargylcarboxamides to 5-methylene-4,5-dihydrooxazoles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A Combined Theoretical and Experimental Research Project into the Aminolysis of ,-Lactam Antibiotics: The Importance of Bifunctional CatalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2003Natalia Díaz Abstract This paper reports the results of experimental work on the aminolysis of penicillin (6-APA) and monobactam (aztreonam) antibiotics by propylamine or ethanolamine. In general, aztreonam is slightly more reactive than 6-APA, despite the common assumption that the amide bond should be less activated in monobactams. Intriguingly, when ethanolamine acts as the nucleophile, the corresponding rate law has a kinetic term proportional to [RNH2][RNH3+]. To complement the experimental observations, the rate-determining free energy barriers in aqueous solution for various mechanistic pathways were computed by standard quantum chemical methodologies. From previous theoretical work it was assumed that the aminolysis of ,-lactams proceeds through mechanisms in which either a water molecule or a second amine molecule may act as bifunctional catalysts, assisting proton transfer from the attacking amine molecule to the leaving amino group. The energy barriers as computed have moderate values (ca. 26,34 kcal·mol,1) and reproduce most of the experimentally observed kinetic trends. Furthermore, the calculations predict that positively charged ethanolamine molecules can act as bifunctional catalysts as well, thus explaining the presence of the kinetic term proportional to [RNH2][RNH3+] in the rate law. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [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] Isolation of the dxr gene of Zymomonas mobilis and characterization of the 1-deoxy- D -xylulose 5-phosphate reductoisomeraseFEMS MICROBIOLOGY LETTERS, Issue 1 2000Sigrid Grolle Abstract The gene encoding the second enzyme of the 2C -methyl- D -erythritol 4-phosphate (MEP) pathway for isopentenyl diphosphate biosynthesis, 1-deoxy- D -xylulose 5-phosphate (DXP) reductoisomerase, was cloned and sequenced from Zymomonas mobilis. The deduced amino acid sequence showed the highest identity (48.2%) to the DXP reductoisomerase of Escherichia coli. Biochemical characterization of the purified DXP reductoisomerase showed a strict dependence of the enzyme on NADPH and divalent cations (Mn2+, Co2+ or Mg2+). The enzyme is a dimer with a molecular mass of 39 kDa per subunit and has a specific activity of 19.5 U mg protein,1. Catalysis of the intramolecular rearrangement and reduction of DXP to MEP is competitively inhibited by the antibiotic fosmidomycin with a Ki of 0.6 ,M. [source] Catalysis: Synthesis of High-Surface-Area Platinum Nanotubes Using a Viral Template (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Mater. [source] Porous Chromium Terephthalate MIL-101 with Coordinatively Unsaturated Sites: Surface Functionalization, Encapsulation, Sorption and CatalysisADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Do-Young Hong Recent ideas concerning site-selective functionalization of chromium terephtha-late MIL-101 are discussed, focusing on the utilization of unsaturated Cr(III) sites (see image). Recent advances in synthesis, selective surface functionalization, outstanding sorption properties, encapsulation of nanoobjects, and catalytic applications in MIL-101 are also discussed. [source] Multicomponent Approach Towards the Synthesis of Substituted Pyrroles under Supramolecular Catalysis Using , -Cyclodextrin as a Catalyst in Water Under Neutral ConditionsHELVETICA CHIMICA ACTA, Issue 10 2009Narayana Murthy, Sabbavarapu Abstract Synthesis of substituted pyrroles in H2O by using , -cyclodextrin as a supramolecular catalyst is described. This reaction has several advantages over existing methods and provides substituted pyrroles in good-to-excellent yields (79,89%). The supramolecular catalysis of the reaction was studied using 1H-NMR spectroscopy. , -Cyclodextrin can be recovered and reused several times without loss of activity. [source] Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis?HELVETICA CHIMICA ACTA, Issue 3 2007Experiments Pointing to an Alternative View, Thoughts Abstract The N,O-acetal and N,O-ketal derivatives (oxazolidinones) formed from proline, and aldehydes or ketones are well-known today, and they are detectable in reaction mixtures involving proline catalysis, where they have been considered ,parasitic dead ends'. We disclose results of experiments performed in the early 1970's, and we describe more recent findings about the isolation, characterization, and reactions of the oxazolidinone derived from proline and cyclohexanone. This oxazolidinone reacts (THF, room temperature) with the electrophiles , -nitrostyrene and chloral (=trichloroacetaldehyde), to give the Michael and aldol adduct, respectively, after aqueous workup (Scheme,5). The reactions occur even at ,75° when catalyzed with bases such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or EtN(i-Pr)2 (DIPEA) (10%; Table,1). It is shown by NMR (Figs.,1 and 3) and IR analysis (Figs.,2 and 4) that the primarily detectable product (before hydrolysis) of the reaction with the nitro-olefin is again an oxazolidinone. When dissolved in hydroxylic solvents such as MeOH, ,hexafluoroisopropanol' ((CF3)2CHOH; HFIP), AcOH, CF3COOH, or in LiBr-saturated THF, the ring of the oxazolidinone from cyclohexanone and proline opens up to the corresponding iminium ion (Tables,2,4), and when treated with strong bases such as DBU (in (D8)THF) the enamino-carboxylate derived from proline and cyclohexanone is formed (Scheme,8). Thus, the two hitherto putative participants (iminium ion and enamine) of the catalytic cycle (Scheme,9) have been characterized for the first time. The commonly accepted mechanism of the stereoselective C,C- or C,X-bond-forming step (i.e., A,D) of this cycle is discussed and challenged by thoughts about an alternative model with a pivotal role of oxazolidinones in the regio- and diastereoselective formation of the intermediate enamino acid (by elimination) and in the subsequent reaction with an electrophile (by trans -addition with lactonization; Schemes,11,14). The stereochemical bias between endo - and exo -space of the bicyclo[3.3.0]octane-type oxazolidinone structure (Figs.,5 and 6) is considered to possibly be decisive for the stereochemical course of events. Finally, the remarkable consistency, with which the diastereotopic Re -face of the double bond of pyrrolidino-enamines (derived from proline) is attacked by electrophiles (Schemes,1 and 15), and the likewise consistent reversal to the Si -face with bulky (Aryl)2C-substituents on the pyrrolidine ring (Scheme,16) are discussed by invoking stereoelectronic assistance from the lone pair of pyramidalized enamine N-atoms. [source] Engineering Homochiral Metal-Organic Frameworks for Heterogeneous Asymmetric Catalysis and Enantioselective SeparationADVANCED MATERIALS, Issue 37 2010Yan Liu Abstract Owing to the potential applications in technological areas such as gas storage, catalysis, separation, sensing and nonlinear optics, tremendous efforts have been devoted to the development of porous metal-organic frameworks (MOFs) over the past ten years. Homochiral porous MOFs are particularly attractive candidates as heterogeneous asymmetric catalysts and enantioselective adsorbents and separators for production of optically active organic compounds due to the lack of homochiral inorganic porous materials such as zeolites. In this review, we summarize the recent research progress in homochiral MOF materials, including their synthetic strategy, distinctive structural features and latest advances in asymmetric heterogeneous catalysis and enantioselective separation. [source] Thiofenchone s -methylide and its spiro-1,3,4-thiadiazoline precursorHETEROATOM CHEMISTRY, Issue 3 2001Rolf Huisgen Spiro[fenchane-2,2,-(1,3,4)-thiadiazoline] (6), prepared from thiofenchone and diazomethane, extrudes N2 (t1/2 22 min, 46°C, toluene) and furnishes the S-methylide 7 which, in turn, closes the thiirane ring or else is intercepted by 1,3-cycloadditions to dipolarophiles (tetracyanoethylene, maleic anhydride, N-methyl-1,2,4-triazoline-3,5-dione, aromatic thioketones). When thiocarbonyl S-methylide 7 is set free in methanol, fenchone S,O-dimethylacetal is formed as an HX adduct. Catalysis by acetic acid converts 7 to 1-(methylthio)-,-fenchene (25) by way of a Wagner-Meerwein rearrangement. The addition of diazomethane to thiocampher leads, via thiadiazoline 12, to thiocamphor S-methylide; the latter undergoes a 1,4-H shift, thus affording 2-methylthio-2-bornene (11). © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:136,145, 2001 [source] Insoluble Perfluoroalkylated Polymers: New Solid Supports for Supported Fluorous Phase CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Nicolas Audic Abstract New perfluoroalkylated polystyrene resins have been prepared by the suspension polymerisation of 4-(perfluoro- n -octyl)styrene. The evaluation of these highly fluorinated insoluble materials as catalyst supports for rhodium-catalysed hydrogenation of styrene and palladium-mediated Suzuki,Miyaura carbon-carbon bond forming reactions with 4-bromoacetophenone and 4-bromoanisole revealed improvements in the recycling of the perfluoroalkylated catalysts as compared to that achieved using fluorous reverse-phase silica gel. [source] One-Pot Synthesis of Quinoline Derivatives Directly from Terminal Alkynes via Sequential Ruthenium(II) and Acid CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Min Zhang Abstract A convenient one-pot synthesis of 2,3-disubstituted, 2,3,6-trisubstituted, and 2,3,6,7-tetrasubstituted quinoline analogues from terminal alkynes via sequential ruthenium(II) and para -toluenesulfonic acid (p -TSA) co-catalyzed reactions is described. The catalytic process is shown to take place first via intermediate formation of an allyl ketone and then addition of an aniline derivative to the allyl ketone. The p -TSA is a catalyst for both allyl ketone and quinoline synthetic steps. The method allowed us to synthesize a wide range of quinoline derivatives and introduce different substituents by employing various simple starting materials. The reaction allows the synthesis of halogen-containing products. [source] The First Example of Saccharin-Lithium Bromide Catalysis: Direct Synthesis of N -Tosylimines from AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Rajesh Patel Abstract The first procedure to access N -tosylimines directly from alcohols under mild and neutral conditions is reported. The protocol involves saccharin-lithium bromide-catalyzed oxidation of alcohols to aldehydes/ketones with chloramine-T followed by their condensation with the in situ generated oxidation by-product p -toluenesulfonamide in the same reaction vessel to afford N -tosylimines in 40,90% overall yields. The present work opens up a new and efficient synthetic route to N -tosyimines directly from alcohols in a one-pot procedure. [source] Ruthenium ONO-Type Pincer Complex: Synthesis, Structural Characterization, and CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Yao Zhang Abstract A novel nitrone-based pincer ligand was developed by a single-step synthesis from N -(tert -butyl)hydroxylamine acetate and 2,6-pyridinedicarboxaldehyde. The developed ligand allowed us to synthesize a cationic ruthenium pincer complex. A distorted octahedral coordination environment around the ruthenium center was observed. The complex showed excellent catalytic activity in transfer hydrogenation reactions with turnover numbers up to 590,000. [source] Ditopic Cyclodextrin-Based Receptors: New Perspectives in Aqueous Organometallic CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Natacha Six Abstract The mass transfer properties of mono- and ditopic ,-cyclodextrin-based receptors have been evaluated in a biphasic palladium-catalyzed Tsuji,Trost reaction and compared to one of the best mass-transfer promoters, namely the randomly methylated ,-cyclodextrin. While monotopic receptors appeared to be poor mass-transfer promoters of long alkyl chain allyl carbonates or urethanes, cooperative effects have been evidenced with ditopic cyclodextrin-based receptors, opening new perspectives in aqueous organometallic catalysis. [source] Properties and Catalytic Activities of New Easily-Made Amphiphilic Phosphanes for Aqueous Organometallic CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010Michel Ferreira Abstract Mono- and disulfonated amphiphilic versions of triphenylphosphane (PPh3) and cyclohexyl(phenyl)phosphane were easily synthesized from commercial reagents and sulfuric acid. The behaviour of these phosphanes in solution was investigated by surface tension, isothermal titration calorimetry, nuclear magnetic resonance and cryo-transmission electron microscopy. Two different supramolecular assemblies were evidenced according to the degree of sulfonation. The monosulfonated phosphanes formed well organized micelle-like aggregates while the disulfonated phosphanes formed heterogeneous and disorganized vesicle-like assemblies. The efficiency of these amphiphilic phosphanes was evaluated in the aqueous biphasic, palladium-catalyzed cleavage of allyl alkyl carbonates. [source] Polymer-Supported, Carbon Dioxide-Protected N-Heterocyclic Carbenes: Synthesis and Application in Organo- and Organometallic CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Gajanan Manohar Pawar Abstract The synthesis of a resin-supported, carbon dioxide-protected N-heterocyclic carbene (NHC) and its use in organocatalysis and organometallic catalysis are described. The resin-bound carbon dioxide-protected NHC-based catalyst was prepared via ring-opening metathesis copolymerization of 1,4,4a,5,8,8a-hexahydro-1,4,5,8- exo,endo -dimethanonaphthalene (DMNH6) with 3-(bicyclo[2.2.1]hept-5-en-2-ylmethyl)-1-(2-propyl)-3,4,5,6-tetrahydropyrimidin-1-ium-2-carboxylate (M1), using the well-defined Schrock catalyst Mo[N -2,6-(2-Pr)2 -C6H3](CHCMe2Ph)(OCMe3)2 and was used for a series of organocatalytic reactions, i.e., for the trimerization reaction of isocyanates, as well as for the cyanosilylation of carbonyl compounds. In the latter reaction, turn-over numbers (TON) up to 5000 were achieved. In addition, the polymer-supported, carbon dioxide-protected N-heterocyclic carbene served as an excellent progenitor for various polymer-supported metal complexes. It was loaded with a series of rhodium(I), iridium(I), and palladium(II) precursors and the resulting Rh-, Ir-, and Pd-loaded resins were successfully used in the polymerization of phenylacetylene, in the hydrogen transfer reaction to benzaldehyde, as well as in Heck-type coupling reactions. In the latter reaction, TONs up to 100,000 were achieved. M1, as a non-supported analogue of poly-M1- b -DMNH6, as well as the complexes PdCl2[1,3-bis(2-Pr)tetrahydropyrimidin-2-ylidene]2 (Pd-1) and IrBr[1-(norborn-5-ene-2-ylmethyl)-3-(2-Pr)-3,4,5,6-tetrahydropyrimidin-2-ylidine](COD) (Ir-1) were used as homogeneous analogues and their reactivity in the above-mentioned reactions was compared with that of the supported catalytic systems. In all reactions investigated, the TONs achieved with the supported systems were very similar to the ones obtained with the unsupported, homogeneous ones, the turn-over frequencies (TOFs), however, were lower by up to a factor of three. 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