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  • 1
    Electronic Resource
    Electronic Resource
    100 years of the biginelli dihydropyrimidine synthesis
    Amsterdam : Elsevier
    Tetrahedron 49 (1993), S. 6937-6963 
    Details
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0040-4020(01)87971-0
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  • 2
    Electronic Resource
    Electronic Resource
    [2+4] Cycloaddition reactions of neat dipivaloylketene (1993)
    Springer
    Monatshefte für Chemie 124 (1993), S. 1133-1141 
    Details
    ISSN: 1434-4475
    Keywords: Hetero-Diels-Alder reaction ; Cycloaddition ; α-Oxo ketenes ; Flash-vacuum-pyrolysis ; 1,3-Dioxin-4-ones ; 1,3-Oxazin-4-ones ; 4-Pyrones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung [2+4]-Hetero-Diels-Alder-Reaktionen des Dipivaloylketens (2) mit polaren Mehrfachbindungssystemen werden beschrieben. Aldehyde und Ketone cyclisieren mit2 zu den 1,3-Dioxin-4-onen7, Imine und Heterokumulene (X=C=N) bilden die 1,3-Oxazin-4-one9 und11. Analoge Reaktionen von2 mit Ethylvinylether, Ethoxyacetylen, Diethylcyanamid und Thioadamantanon ergeben die [2 + 4]-Addukte12, 14, 15 und16. Diese Cycloadditionen verlaufen unter sehr milden Reaktionsbedingungen und mit hohen Ausbeuten.
    Notes: Summary Various [2+4] hetero-Diels-Alder cycloddition reactions of dipivaloylketene (2) with polarized multiple bond systems are described. Aldehydes and ketones react with2 to furnish 1,3-dioxin-4-ones7, imines and heterocumulenes (X=C=N) form 1,3-oxazin-4-ones9 and11, respectively. Analogous reactions of2 with ethyl vinyl ether, ethoxyacetylene, diethylcyanamide, and adamantanethione leading to [2 + 4] adducts12, 14, 15 and16 are also reported. All these cycloadditions proceed in high yield at very mild reaction conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810021
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  • 3
    Electronic Resource
    Electronic Resource
    Conformation and reactivity of α-oxo-ketenes: Ab initio and semiempirical (AM1, PM3) calculations (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 132-143 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio MP2/6-31G*//MP2/6-31G* and semiempirical AM1 and PM3 calculations on a series of differently substituted α-oxo-ketenes are used to investigate E/Z-isomerism and rotational barriers in these molecules. Sterically crowded derivatives are found to exist solely as s-E conformers. The unusual stability of these derivatives thus can be attributed to their inability to adopt the s-Z conformation required for the normal α-oxo-ketene reactions. With respect to structures and energies, the PM3 method (especially in the case of highly crowded molecules) is found to be less reliable than AM1. Ab initio HF/3-21G and PM3 vibrational frequencies appear to be of sufficient accuracy for a distinction between s-Z and s-E conformers. In this respect, the AM1 method appears less reliable. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540150203
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  • 4
    Electronic Resource
    Electronic Resource
    Direct Observation and Trapping of a Heterocyclic α-Oxo Ketene: 3-Carbonyl-1,3-dihydro-1-methyl-2H-indol-2-one (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2357-2360 
    Details
    ISSN: 0009-2940
    Keywords: α-Oxo ketenes ; Wolff rearrangement ; Matrix isolation ; Ketenes, α-oxo- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound 8a was generated by both flash vacuum pyrolysis and matrix photolysis of diazoquinolone 7 and identified by Ar-matrix IR spectroscopy and mass spectrometry. Trapping of the highly reactive α-oxo ketene 8a with methanol leads to β-keto ester 9, whereas dimerization of 8a furnishes spiro compound 10.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261026
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