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  • Analytical Chemistry and Spectroscopy  (25,033)
  • Biochemistry and Biotechnology  (13,095)
  • Catalysis
  • Wiley-Blackwell  (38,274)
  • 1
    Electronic Resource
    Electronic Resource
    Bimolekulare Radikalbildung durch H-Transfer, 2. H-Transferreaktionen mit Phenalen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1039-1045 
    Details
    ISSN: 0009-2940
    Keywords: Hydrogen transfer ; Radical formation, molecule induced ; C—H bond dissociation enthalpies, determination of ; Catalysis ; Coal pyrolysis ; Phenalene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bimolecular Formation of Radicals by H-Transfer, 2[1]. - H-Transfer Reactions of PhenaleneThe uncatalysed H transfer from phenalane (7) to α1-methyl-styrene (2) and the selfreaction (d) of phenalene (7) are quantitative transformations in the presence of an excess of 9,10-dihydroanthracene (1) (DHA) in diphenyl ether at 200-250°C. In this system phenalene (7) is consumed only in reaction (d) because the phenalenyl radicals (9) are captured by DHA (1) to give phenalene (7) and 9,10-dihydroanthryl radicals (3). The latter disproportionate rapidly. Accordingly, phenalene (7) acts as a catalyst for the hydrogenation of α1-methylstyrene (2) by DHA (1). The activation parameters of the two reactions (e) and (d) were obtained from kinetic experiments between 200-250°C. They allow the determination of the C—H bond enthalpy δHdiss of phenalene (7) (65.3 kcal mol-1) at the methylene position.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260426
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  • 2
    Electronic Resource
    Electronic Resource
    Substituierte N,N-Chelat-Liganden - Anwendungen in der Molybdän-katalysierten Olefin-EpoxidationHerrn Prof. Dr. H. Schmidbaur zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2373-2379 
    Details
    ISSN: 0009-2940
    Keywords: Chelating ligands ; Molybdenum complexes ; Peroxo complexes ; Catalysis ; Olefine epoxidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted N,N-Chelate Ligands - Applications in Molybdenum-Catalyzed Epoxidation of Olefins*Oxodiperoxomolybdenum complexes 4 of substituted 2-[3(5)-pyrazolyl]pyridines (2a-g) were synthesized in order to control the solubility of these complexes in organic solvents. Alkyl side chains (butyl, octyl, octadecyl) increase the solubility of the complexes and enable spectroscopic investigations in solution. Due to the symmetry of the ligands the peroxo complexes 4 appear in two isomeric forms, with the terminal oxo ligand in the trans position either to pyridine or to pyrazole. The latter isomer of (C5H4NC3H2N2CH2COOEt)MoO(O2)2 (4f) was characterized by an X-ray structure analysis. The alkyl-substituted peroxo complexes are active catalysts for the epoxidation of olefins with tert-butyl hydroperoxide.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941271206
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  • 3
    Electronic Resource
    Electronic Resource
    Functionalized Diorganozinc Compounds: Key Reagents for the Synthesis of Enantiomerically Pure 2,5-Disubstituted cis- and trans-Tetrahydrofurans (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1021-1028 
    Details
    ISSN: 0009-2940
    Keywords: Synthesis, stereoselective ; Catalysis ; Tetrahydrofurans ; Dialkylzinc reagents ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,4-Diol derivatives 4a-i were synthesized stereoselectively by either reagent- or catalyst-controlled routes using the addition of functionalized diorganozinc reagents to aldehydes. The stereoselectivities along the reagent-controlled synthetic path were in the range between 80:20 and 95:5. The stereoselectivities along the catalyst route exceeded 95:5. The 1,4-diol derivatives 4 thus obtained were transformed into enantiomerically pure cis- and trans-2,5-disubstituted tetrahydrofurans (16-20) by means of an intramolecular Williamson reaction.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281010
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of Functionalized Carbamates through a Palladium-Catalyzed Reductive Carbonylation of Substituted Nitrobenzenes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 13-22 
    Details
    ISSN: 0009-2940
    Keywords: Carbamates ; Catalysis ; Substituted nitrobenzenes ; Palladium ; Reductive carbonylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The palladium-catalyzed reductive carbonylation of ortho and para-substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1, 10-phenanthroline)2(triflate)2 catalyst system, the scope of the reaction has been studied. Substrates with electron-donating substituents at the para position were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. the selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron-withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at the ortho position of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion ot the nitro group. Especially with 4-nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis for N-protected amines containing carboxylic acid function.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300104
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  • 5
    Electronic Resource
    Electronic Resource
    A Specific Route to Enantiomerically Pure Asymmetric (η6-Arene)(η4-1,5-cyclooctadiene)Ru(0) ComplexesDedicated to Professor Rolf Gleiter on the occassion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 123-130 
    Details
    ISSN: 0009-2940
    Keywords: Arene complexes ; Ruthenium compounds ; Electrophilic substitution ; Lithiation ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral or achiral (arene)(COD)Ru complexes can be made by replacing the η6-ligands of (η4-1,5-COD)(η6-1,3,5-cyclooctatriene)Ru (1) or (η4-1,5-COD)(η6-naphthalene)Ru (2) by a suitable arene. This well known reaction has been extended to mono- and dibromoarenes and we report a novel route to substituted (arene)(COD)Ru species, utilizing (bromoarene)-(COD)Ru as starting materials. These facilitate a rapid bromine-lithium exchange reaction with nBuLi at low temperatures and the lithiated species react readily with alkyl chloroformates as electrophiles. By using chiral electrophiles [alkyl = (-)-menthyl] enantiomerically pure or diastereomeric complexes containing CO2R* groups are formed, depending on the symmetry of the original complex. A diastereomeric 1:1 mixture was separated by recrystallization. All (arene)-(COD)Ru complexes tested so far are useful as catalysts for the hydrogenation of simple alkenes at room temperature.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300121
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  • 6
    Electronic Resource
    Electronic Resource
    New Coupling Reactions and Phosphorylations Using Organozinc Reagents (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1021-1027 
    Details
    ISSN: 0009-2940
    Keywords: Zinc ; Chirality ; Cross-coupling ; Phosphorylations ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This Microreview on the chemistry of organozinc reagents starts by briefly showing the methods of preparation of organozinc compounds and then discusses the considerable synthetic utility of zinc organometallics for the formation of new carbon-carbon bonds in the presence of transition-metal catalysts. Finally, the use of organozinc chemistry for the preparation of polyfunctional and chiral phosphanes is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300802
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  • 7
    Electronic Resource
    Electronic Resource
    Molybdenum-Catalysed and -Mediated Cycloaddition Reactions: Efficient Synthesis of Complex Products from 1-Oxa-1,3-dienes and Cyclotrienes or -tetraenes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 453-462 
    Details
    ISSN: 0009-2940
    Keywords: Cycloadditions ; Catalysis ; 1-Oxa-1,3-dienes ; Molybdenum ; stereoselectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molybdenum-mediated [6 + 2]-cycloaddition reactions of unsaturated ketones to cyclotri- or -tetraenes, e.g. cyclohepta-1,3,5-triene or cyclooctatetraene, proceed under very mild conditions, in high yields and with excellent stereoselectivity starting from the appropriate dicarbonylbis[π4-(1-oxa-1,3-diene)]molybdenum complexes. The stereochemistry of the product arising from the reaction of dicarbonylbis[π4-(5-methylhex-3-en-2-one)]molybdenum with cyclohepta-1,3,5-triene allows one to deduce a stepwise mechanism for this addition. The reactants are fused, as would be expected from an exo-type approach, thus indicating an intermolecular attack of the cycloheptatriene. Tungsten oxadiene complexes are effective in analogous reactions at somewhat reduced reaction rates. Catalytic cycloadditions are observed in several cases when 1-5 mol% of the highly reactive dicarbonylbis[π4-(R-(+)-pinocarvone)]molybdenum is employed as the catalyst. Cycloadducts are formed diastereospecifically in most cases. When cyclooctatrienes are employed as reactants, a sequence of electrocyclization of the triene and subsequent [4 + 2]-cycloadditon occurs with high selectivity and efficiency, leading to a pentacyclic ketone. The product structure reveals an endo-type approach of the polyene in this case.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300404
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  • 8
    Electronic Resource
    Electronic Resource
    Metal-Catalyzed Oxidations, 4Part 3: Ref.[1].. The Reaction of Molybdenumperoxo Complexes with Brønsted and Lewis Acids (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 575-580 
    Details
    ISSN: 0009-2940
    Keywords: Molybdenum complexes ; Peroxo complexes ; Catalysis ; Olefin epoxidation ; Proton transfer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NMR studies of the reaction of complexes of the type (L-L)MoO(O2)2 (L - L= bidentate ligand) with strong Brønsted and Lewis acids prove that protons are transferred preferentially to an η2-peroxo and not to the oxo ligand. This behavior in proton transfer reactions is one critical point of the catalytic activity of such complexes in olefin epoxidation. EH calculations on the model complex (NH3)2MoO(O2)2 support the spectroscopic investigations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290516
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  • 9
    Electronic Resource
    Electronic Resource
    Contributions of the Chemistry of Boron, 236. In Quest of New and Stable Bis(organyloxy)boranes (RO)2BH for Catalytic HydroborationDedicated to Prof. Dr. Marianne Baudler on the occasion of her 75th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 363-370 
    Details
    ISSN: 0009-2940
    Keywords: Bis(triphenylmethoxy)hydroborane ; Naphtho[2,3-d], -1,3,2-dioxaborolane ; Naphtho[1,8-de]-1,3,2-dioxaborinane ; Phenanthro[9,10-d]-1,3,2-dioxaborolane ; Dibenzol[d,g]-1,3,2-dioxaborocine ; Bis(diphenylmethoxy)borane ; Tetrachlorobenzo-1,3,2-dioxaboraolen ; Hydroborations ; Boron ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New and stable bis(organyloxy)boranes, 1,3,2-dioxaborolanes and 1,3,2-dixoaborinanes have been prepared (i) from the corresponding diol and BH3·THF and (ii) from 1,2-diketones and BH3·THF. They were characterized by spectroscopic techniques. The BH stretching frequency seems to be a measure of ring strain and Lewis acidity. The compounds have been qualitatively tested in the transition-metal-catalysed hydroboration of cyclopentene, and the dioxaborinane 11 proved to be superior to the 1,3,2-dioxaborolanes 9 and 18.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300310
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  • 10
    Electronic Resource
    Electronic Resource
    Palladium-Copper-Catalyzed Coupling of Tricarbonylchromium-Complexed Phenylacetylene with Iodoarenes - A Facile Access to Alkynyl-Bridged Cr(CO)3-Complexed Benzenes (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 607-613 
    Details
    ISSN: 0009-2940
    Keywords: Arene complexes ; Chromium compounds ; Alkynes ; Catalysis ; Coupling reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The palladium-copper-catalyzed coupling of the tricarbonyl-chromium-complexed chlorobenzene 1 with (trimethylsilyl)-acetylene gives tricarbonyl{η6-[(trimethylsilyl)ethynyl]-benzene}chromium(0) (2) in high yield. After desilylation of 2 tricarbonyl[η6-(ethynylbenzene)]chromium(0) (3) is obtained quantitatively. Using the palladium-copper-catalyzed methodology, we can readily introduce Cr(CO)3-complexed phenylethynyl units by a multifold coupling of 3 with iodobenzene, 1,2-, 1,3-, 1,4-di- and 1,3,5-tiiodobenzene (4a-e) or 1 to give polynuclear Cr(CO)3-complexed (phenylethynyl)benzenes 5a-e and doubly Cr(CO)3-complexed tolane 6 in good to moderate yield. The crystal structure analyses of μ3-{η6:η6:η6[1,3,5-benzenetriyltris(2,1-ethynediyl)]tris(benzene)}tris[tricarbonylchromium(0)] (5e) and μ-{η6:η6-[1,2-ethynediylbis(benzene)]}bis[tricarbonylchromium(0)] (6) reveal that the tricarbonylchromium tripods in the same molecule are arranged in antiparallel syn-eclipsed conformations. The Eglington coupling of 3 affords a doubly Cr(CO)3-complexed diphenylbutadiyne 7 in excellent yield.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290604
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