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  • 1995-1999  (11)
  • 1990-1994
  • 1960-1964
  • 1910-1914
  • 1890-1899
  • 1999  (11)
  • Catalysis
  • Inorganic Chemistry
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Material
Years
  • 1995-1999  (11)
  • 1990-1994
  • 1960-1964
  • 1910-1914
  • 1890-1899
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of 1β-Methylcarbapenem Antibiotic Precursors by Cyclization Using π-Allylpalladium Complexes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 621-626 
    Details
    ISSN: 1434-193X
    Keywords: 1β-Methylcarbapenems ; Palladium ; Ruthenium ; Catalysis ; Cyclizations ; Stereoselective hydrogenation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -An efficient diastereoselective multi-step synthesis of bicyclic 1β-methylcarbapenem antibiotic precursors has been developed, starting from the commercially available 4-acetoxyazetidin-2-one 4. Chiral ruthenium catalysts are used in the hydrogenation step to control the β-stereochemistry at the 1-position, and a π-allylpalladium ring-closure strategy is used to form the functionalized carbapenem skeleton.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Palladium-Catalyzed Cyclocarbonylation of o-Ethynylphenols and Vinyl Triflates To Form 3-Alkylidene-2-coumaranones (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1137-1141 
    Details
    ISSN: 1434-193X
    Keywords: Cyclocarbonylation ; Alkynes ; Catalysis ; Palladium ; Vinyl triflates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -o-Ethynylphenols react with vinyl triflates, in the presence of tetrakis(triphenylphosphane)palladium(0) and under carbon monoxide, to form 3-alkylidene-2-coumaranones in good yield.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    New Chiral Catalysts Containing N,O-Heterocycles Derived from Chiral Amino Alcohols (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3323-3333 
    Details
    ISSN: 1434-193X
    Keywords: Chirality ; Catalysis ; Amino acids ; Crown ethers ; Heterocyclic compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantioselectivity exerted by a new series of chiral catalysts containing N,O-heterocycles of different sizes has been checked in the addition of diethylzinc to benzaldehyde, which was used as a model reaction. The catalysts were derived from natural amino acids, following a relatively simple procedure, and in several cases excellent ee values were obtained. The results were complementary since ee's ranged from 98% (R) to 94% (S) excesses of the final 1-phenylpropan-1-ol. Molecular mechanics calculations suggested that the production of the R alcohol may be explained by a mechanism similar to that described by Noyori, in which ZnEt2 interacts solely with the N-C-C-OH fragment, whereas the formation of the S enantiomer needed the direct participation of the lateral chain of the parent amino acid and the N,O-heterocycle.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Cerium(III) Chloride Catalyzed Michael Reaction of 1,3-Dicarbonyl Compounds and Enones in the Presence of Sodium Iodide Under Solvent-Free Conditions (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 617-620 
    Details
    ISSN: 1434-193X
    Keywords: Cerium(III) chloride heptahydrate ; Catalysis ; 1,3-Dicarbonyl compounds ; Enones ; Michael reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Cerium(III) chloride heptahydrate in the presence of sodium iodide catalyses the Michael addition of 1,3-dicarbonyl compounds to α,β-unsaturated ketones and α,β-unsaturated aldehydes with extraordinary efficiency. The very mild conditions allow high chemoselectivity as shown by the absence of the typical side reactions, which can be observed in the conventional base-catalyzed processes. More interestingly, when at least one of the starting materials is liquid at room temperature, the reaction can also be performed without solvents. The CeCl3· 7 H2O/NaI catalyst system can be easily separated from the reaction mixture and it can be reused without an appreciable loss of activity. Advantages of the present procedure, which utilizes cheap and “friendly” reagents, over the previously reported ones, are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of γ-Amino- and δ-Amino-Functionalised Ethers, Amines, or Silanes by Hydroaminomethylation of Heterofunctionalised Allylic Compounds (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 653-660 
    Details
    ISSN: 1434-193X
    Keywords: Hydroaminomethylation ; Rhodium ; Catalysis ; Carbonylation ; Heterofunctionalised allylic compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Heterofunctionalised allylic ethers 1, silanes 5, and amines 9 are hydroformylated in the presence of primary or secondary amines 2 to form the corresponding γ-amino- and δ-amino-functionalised compounds. The rhodium(I)-catalysed reaction sequence proceeds by aldehyde formation and subsequent reductive amination to generate the corresponding functionalised secondary or tertiary amines. This selective one-pot hydroaminomethylation procedure establishes access to γ-amino- and δ-amino-functionalised ethers, amines or silanes with potential biological activity.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of γ-Butyrolactones by a Baeyer-Villiger Oxidation with Hydrogen Peroxide, Catalysed by Methyltrioxorhenium (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1767-1770 
    Details
    ISSN: 1434-193X
    Keywords: Baeyer-Villiger reaction ; Lactones ; Methyltrioxorhenium ; Catalysis ; Oxidations ; Cyclobutanones ; Ketones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: γ-Butyrolactones were obtained in good yields and high regioselectivity by a Baeyer-Villiger oxidation with H2O2 catalysed by methyltrioxorhenium. The lactonization was chemoselective in the presence of double bonds, aromatic rings, and chlorine substituents. A trimethylsiloxy-substituted ketone was converted directly into a hydroxylated lactone in good yield and regioselectively.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    Small Libraries of Polymer-Supported Amino Alcohols: An Application to the Enantioselective Reduction of Acetophenone by LAH (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2263-2267 
    Details
    ISSN: 1434-193X
    Keywords: Amino alcohols ; Polymers ; Enantioselective reagents ; Catalysis ; Merrifield resins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from simple amino acid esters and Merrifield resins, a small library of polymer-bound chiral-β-amino alcohols can be prepared. By reaction with LiALH4 the corresponding chiral reducing agents are obtained, having structural variations at both the α and β positions. All supported reagents are able to reduce acetophenone to 1-phenylethanol. Enantioselectivity is observed when the steric hindrance in the chiral fragment is increased. Best results are obtained for the supported derivative of α,α-diphenyl phenylalaninol.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New Hydrogen Transfer Catalysts (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2219-2230 
    Details
    ISSN: 1434-193X
    Keywords: Retrodisproportionation ; Arenes ; EPR spectroscopy ; Thermochemistry ; Coal liquefaction ; Catalysis ; Hydrogen transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transfer of hydrogen from excess 9,10-dihydroanthracene (DHA) to acceptors such as α-methylstyrene is catalyzed, i.e. occurs at temperatures in the range 200-260 °C instead of 280-320 °C, when hydrocarbons with weaker C-H bonds than DHA, e.g. 6H-benzo[cd]pyrene (4), 7H-dibenzo[a,kl]anthracene (5), 4-methyl-7H-benzo[de]naphthacene (6) or 8H-dibenzo[b,fg]pyrene (7), are added to the reaction mixture. The reactions are initiated by bimolecular H-atom transfer from 4-7 to the acceptor (retrodisproportionation) and proceed by nonchain radical mechanisms. This is supported by isotopic labelling and kinetic isotope effects, substituent and solvent effects, EPR spectroscopy of intermediate radicals, and by a comparison of the thermochemical and kinetic characteristics of these reactions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Vinyl- and Divinylcyclopentadienes by Rhodium-Catalyzed Condensation of Alkynes with Cross-Conjugated Amino Metallahexatrienes [= (1-Amino-1,3-butadien-2-yl)carbene Complexes] (M = Cr, W) (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2545-2561 
    Details
    ISSN: 1434-193X
    Keywords: Carbene complexes ; Catalysis ; Metallahexatrienes ; Vinyl cyclopentadienes ; Transmetallation ; Rhodium ; Tungsten ; Chromium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report on the first example of a transition metal-catalyzed cyclization reaction of a Fischer carbene complex. It comprises the generation of vinyl- and divinyl cyclopentadienes under exceedingly mild conditions at 20 °C by condensation of (1-amino-1,3-butadien-2-yl)carbene complexes (= cross-conjugated metallahexatrienes) (CO)5M=C(OEt)C(=CHNR2)CR1=CHR23 (M = Cr, W) with alkynes R3C≡CH 4 (R3 = Ph, cyclohex-1-enyl, isopropenyl, methoxymethyl, 1-trimethylsiloxycyclohex-1-yl) in the presence of catalytic amounts of [(COD)RhCl]2. The starting compounds 3 are accessible in high yields by addition of enamines (E)-R2NCH=CHR22 to (1-alkynyl)carbene complexes (CO)5M=C(OEt)C≡CR11 (M = Cr, W; R1 = Ph, cyclohex-1-enyl).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    A New Access to Diarylmaleic Anhydrides (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1421-1426 
    Details
    ISSN: 1434-193X
    Keywords: Anhydrides ; Coupling reaction ; Enols ; Palladium ; Tin ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A new three-step synthesis of diarylmaleic anhydrides 6, starting from 3-aryl-2-hydroxybut-2-enedioates 2, is reported.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 11
    Electronic Resource
    Electronic Resource
    Electronic Effects on the Stereoselectivity of Epoxidation Reactions Catalysed by Manganese Porphyrins (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3281-3286 
    Details
    ISSN: 1434-193X
    Keywords: Alkenes ; Epoxidation ; Manganese ; Porphyrins ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of MnIII porphyrins progressively halogenated in the β-pyrrolic positions was employed to catalyse the epoxidation of cis-stilbene by iodosylbenzene, and to study the role of the electronic effects on the stereoselectivity of this process. A gradual improvement in the stereoselectivity on increasing the number of β-halogen atoms was observed. The role of steric effects upon the epoxidation was also investigated by placing ortho-substituents in the meso-phenyl rings, and it was found that steric effects are more important than electronic effects toward the stereoselectivity of this process. These results can be rationalised by proposing a competition between a nonstereoselective electrophilic pathway of addition and a stereospecific pathway of oxygen insertion, the former being disfavoured by electron-withdrawing substituents. Alternatively, the formation of an open intermediate between the MnV oxene and the substrate could be suggested, where the stereoselectivity ought to be determined by the competition between closure of the epoxide ring and rotation around the C-C bond. In this case, the enhanced stereoselectivity given by our polyhalogenated porphyrins might be attributed to an acceleration of the epoxide ring closure caused by the electron-withdrawing effect of the halogen substituents.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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