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  • 1980-1984  (4)
  • 1960-1964
  • 1930-1934
  • 1890-1899
  • 1800-1809
  • 1983  (4)
  • Heterocycles
  • 1
    Electronic Resource
    Electronic Resource
    Darstellung und Struktur von Pyrazolyl-Kationen mit Polymethin- und Methan-Gerüst (1983)
    Springer
    Monatshefte für Chemie 114 (1983), S. 219-225 
    Details
    ISSN: 1434-4475
    Keywords: Cyanine dyes ; Dipyrazolylmethanes ; Heterocycles ; N-15-NMR ; O-17-NMR ; Phenazon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The 4-pyrazoline-3-one1 reacts with 4-dimethylaminobenzaldehyde to yield the stable asymmetric cyanine dye2b which reacts with1 to give the colorless (aryl) (dipyrazolyl) methane3b. Using aldehydes with less cationstabilizing groups the polymethines2 are not isolated but only the methanes3. The structures of2b and3 are discussed by1 H,13C and Hetero NMR spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00798325
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  • 2
    Electronic Resource
    Electronic Resource
    Triazolo[4′,3′:4,5] [1,3,4]thiadiazolo[2,3-b]quinazolin-6-one (1983)
    Springer
    Monatshefte für Chemie 114 (1983), S. 339-342 
    Details
    ISSN: 1434-4475
    Keywords: Heterocycles ; Infrared ; 1H-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 3-Methyl-6H-[1,2,4]triazolo[4′ ,3′ : 4,5] [1,3,4]thiadiazolo[2,3-b]chinazolin-6-on (6) wurde mittels Kondensation von Isatoesäureanhydrid (1) mit 4-Amino-5-mercapto-3-methyl[1,2,4]triazol (2) und anschließender Cyclisierung von Zwischenverbindung3 mit POCl3 und PCl3 dargestellt. Als Alternative konnte6 auch über die Kondensation von 3-Amino-2-mercapto-3H-chinazolin-4-on (7) mitN-Carbethoxyhydrazin in Gegenwart von HCl und anschließender Cyclisierung der Zwischenverbindung8 mit Essigsäure synthetisiert werden. Die Strukturen der Verbindungen wurden mittels IR,1H-NMR und Mikroanalyse nachgewiesen.
    Notes: Abstract 3-Methyl-6H-[1,2,4]triazolo[4′,3′: 4,5] [1,3,4]thiadiazolo[2,3-b]quinazolin-6-one (6) has been synthesized by the condensation of isatoic anhydride (1) with 4-amino-5-mercapto-3-methyl-[1,2,4]triazole (2) and final cyclisation of the intermediate3 with POCl3 and PCl3. Alternatively6 could also be synthesized by the condensation of 3-amino-2-mercapto-3H-quinazolin-4-one (7) withN-carbethoxy hydrazine in presence of hydrochloric acid and final cyclisation of the intermediate8 with acetic acid. The structures have been confirmed on the basis of IR, PMR and analytical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00798956
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  • 3
    Electronic Resource
    Electronic Resource
    The Versatile Chemistry of 1,4-Diazines: Organic, Inorganic and Biochemical Aspects (1983)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 22 (1983), S. 171-190 
    Details
    ISSN: 0570-0833
    Keywords: 1,4-Diazines ; Pyrazine ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In chemical research attention is increasingly being focussed on composite “complex” systems with special properties and functions. As components of such systems 1,4-diazines are steadily gaining in popularity. Here, 1,4-diazines means pyrazine and its derivatives as well as compounds with partial pyrazine structure; examples are quinoxaline, phenazine, pteridine, flavin and their derivatives. All these compounds are characterized by a low lying unoccupied π-molecular orbital and by the ability to act as bridging ligand. Due to these two properties 1,4-diazines, and especially their parent compound pyrazine, possess a characteristic reactivity. 1,4-Diazines may be employed to study inter- and intramolecular electron transfer in organic, inorganic and biochemical reactions. In the redox system of 1,4-diazines the paramagnetic 7π-electron intermediate exhibits exceptional stability, whereas the 1,4-dihydro-1,4-diazines with 8π-electrons in a six-membered ring are not generally accessible due to their potential antiaromaticity and their large excess of π electrons. Its inherent bifunctionality and the low lying unoccupied molecular orbital permit pyrazine to form coordination polymers having unusual electrical and magnetic properties. Finally, the phenomena observed for pyrazines may be used in the interpretation of the reactivity of naturally occurring 1,4-diazines, such as flavins and bioluminescent natural products.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198301713
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  • 4
    Electronic Resource
    Electronic Resource
    Homolytic Cyclizations of N-ChloroalkenylaminesDedicated to Professor Jean-Marie Surzur on the occasion of his 50th birthday. (1983)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 22 (1983), S. 337-350 
    Details
    ISSN: 0570-0833
    Keywords: Cyclization ; Chloroamines ; Alkenylamines ; Synthetic methods ; Heterocycles ; Free radicals ; Natural products ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Many N-chloroalkylamines with double bond(s) dissociate homolytically to give chlorine atoms and aminyl radicals which undergo intramolecular cyclization reactions. Here, the nature of the aminyl radicals (neutral, protonated, or complexed to metal salts) appears to be important. The reactivity varies strongly from one species to another, and their selectivities can be different towards addition, substitution, abstraction, or dimerization reactions. A good synthetic tool appears to be the “complexed radical”, which is generated under mild conditions. A variety of β-functionalized, substituted, fused, or bridged azaheterocycles with alkaloid part structures thus become easily accessible in high yields, in a regio- and, possibly, stereoselective manner. Many examples are discussed illustrating the synthetic possibilities, limitations, and mechanistic features of this cyclization process.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198303373
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    Paper (German National Licenses)
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