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  • 1
    Electronic Resource
    Electronic Resource
    Nitroxide (Aminyloxide), 43 Der Einfluß struktureller Faktoren auf die Dimerisierung von Vinylnitroxiden mit cyclischen Acylgruppen als β-Substituenten (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 513-521 
    Details
    ISSN: 0009-2940
    Keywords: Nitroxides, dimerization of / Vinyl nitroxides / 1,2-Oxazepines, 2,5,6,7-tetrahydro- / Nitrones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nitroxides (Aminyl Oxides), 43. - The Effect of Structural Features upon the Dimerization of Vinyl Nitroxides Substituted in β-Position by Cyclic Acyl GroupsReaction between N-alkyl- and N-arylhydroxylamines and hydroxymethylene compounds 4 (derivatives of menthone, norboranone, borananone, indanone, and γ-butyrolactone) affords nitrones existing in the tautomeric forms 5 and 6. Oxidation of these nitrones generates the β-acylated vinyl nitroxides 7, which dimerize in various ways. The N-alkyl-substituted vinyl nitroxides 7DA, De, Ea, Ga, and Gf yield simple CC-bonded dimers 8 From 7Ba dimer 10 is formed via 8Ba. The structure of 10 is confirmed by an X-ray analysis. In contrast, the N-arylsubstituted vinyl nitroxides 7 Ab, Fc, and Bc as well as the N-alkyl-substituted 7 Aa afford the bicyclic dimers 9 which arise by OC dimerization followed by an intramolecular 1,3-dipolar cycloaddition. Finally, the vinyl nitroxides 7Dc and Dd underwent further oxidation to give dehydrodimers 12. 12e is formed only if 6De is oxidized by a large excess of lead dioxide.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230318
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  • 2
    Electronic Resource
    Electronic Resource
    Intramolekulare Cycloaddition von Nitronen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1999-2014 
    Details
    ISSN: 0009-2940
    Keywords: Nitrones ; Cycloaddition, intramolecular ; Heteroanaloga of bicyclo[3.3.0]octanes, bicyclo[4.3.0]nonanes and bicyclo[4.2.1]nonanes ; γ-Amino alcohols, heterocyclic ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intramolecular Cycloaddition of NitronesNitrones 9 and 10, formed by treatment of the corresponding aldehydes with N-substituted hydroxylamines, are converted into the cis fused bicyclic compounds 11 and 12, respectively. While this intramolecular cycloaddition as a rule occurs at room temperature, the formation of compounds 17/18 and/or 20/21 from the corresponding nitrones needs refluxing in toluene with exception of 17Ca. The N-aryl-substituted nitrones 14C/15C form dimers 22C/23C spontanously at room temperature. However, dimerization is reversible; thus 22/23C afford the bicyclic compounds 17/18 and/or 20/21 on heating in toluene via the corresponding nitrone intermediates.  -  Hydrogenation cleaves isoxazolidine ring of the bicyclic compounds. Thus, 17Ca and 18Ca yield the hexahydrothiepine 27C and oxepane derivatives 28C, respectively, 21Ca gives the tetrahydropyran 30C. Diastereomerically pure 29C arises by prolonged hydrogenation of 17Ca under reinforced conditions via 27C.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901231011
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  • 3
    Electronic Resource
    Electronic Resource
    Synthese homochiraler 3-Oxa-2,7-diazabicyclo[3.3.0]octane aus Aminosäuren durch intramolekulare 1,3-dipolare Cycloaddition von Nitronen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 787-795 
    Details
    ISSN: 0009-2940
    Keywords: Heterobicyclo[3.3.0]octanes, homochiral ; Amino acids ; Nitrones ; Cycloadditions, diastereoselective, intramolecular ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Homochiral 3-Oxa-2,7-diazabicyclo[3.3.0]octanes from Amino Acids by Intramolecular 1,3-Dipolar Cycloaddition of NitronesN1-Allylamino alcohols 9 were prepared from amino acids by various methods. Swern oxidation of 9 afforded aldehydes 11. By reaction of 11 with N1-alkylhydroxylamines nitrone intermediates 4 were formed which spontaneously underwent an intramolecular 1,3-dipolar cycloaddition to yield the bicyclic compounds 6. The cycloaddition proceeds diastereoselectively furnishing homochiral compounds 6 from homochiral starting materials. The structure of 6aA was confirmed by X-ray structural analysis.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260333
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