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  • 1
    Electronic Resource
    Electronic Resource
    A Novel Synthesis of Tetraaminoethenes by Reduction of Oxalic Amidines and Subsequent Electrophilic Substitution (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 183-187 
    Details
    ISSN: 1434-193X
    Keywords: Oxalic amidines ; Lithium diamides ; Tetraaminoethenes ; Nitrogen heterocycles ; Reduction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reduction of the 1,4-diaza-1,3-butadiene substructure of hexasubstituted amidines 1 with lithium metal yields the dilithium diamides 2. Subsequent reactions of these with various electrophiles give the title substances 3, 4 and 5. The quenching reaction of 2 with organosilicon derivatives leads to open-chain 3b as well as to cyclic tetraaminoethenes 4a,b. Treatment of 2 with methanol gives 3a which in the presence of oxygen is reoxidized to the starting amidine 1. Using alkyl halides as electrophiles, compounds 3c-e and 4c,d could be obtained in moderate to good yields. X-ray structural analyses of derivatives 3e and 4c reveal sterically overloaded central C-C double bonds. Whereas phosgene and its thio derivative give the imidazolines 4e,f, methyl benzoate allows a stepwise substitution leading to tetraaminoethenes bearing different residues at the nitrogen atoms.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    A One-Pot Synthesis of New Macrocyclic Compounds with Tetraaminoethene Substructure (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1803-1810 
    Details
    ISSN: 1434-193X
    Keywords: Oxalic amidines ; Lithium diamides ; Tetraaminoethenes ; Reduction ; Macrocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A convienent one-pot synthesis of macrocycles containing a tetraaminoethene substructure is described. Starting from oxalic amidines 1, reduction with lithium and subsequent addition of phenyl isothiocyanate afforded the anionic bis(thiocarbamoyl) derivatives 3. In the final step, a ring-closure reaction using a large number of α,ω-dielectrophilic building blocks yields the new macrocyclic compounds 6-14.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    1,4,5,8-Tetraazafulvalenes - A Convenient One-Pot Synthesis and Their Conversion to Fused Ring SystemsDedicated to Professor Roland Mayer on the occasion of his 70th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 617-622 
    Details
    ISSN: 0947-3440
    Keywords: Carbenoids ; Imidoyl chlorides ; Oxalic amidines ; Tetraazafulvalenes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloacylation of formamidine with bisimidoyl chlorides of oxalic acid yields the new 1,4,5,8-tetraazafulvalenes 4 via dimerization of carbenoid intermediates. The high symmetry of the stable heterofulvalenes as well as their dye character is confirmed by NMR and UV/Vis spectral data. Whereas methylation of these substrates leads to a mixture of diastereomeric tetramethyl derivatives 9a, b, cyclization with thiophosgene or triethyl orthoformate gives mainly the fused-ring derivatives of 2H-imidazole 10 and 12a, b, respectively. In the case of 12a, the X-ray crystal structure reveals the approximately ideal planarity of the central tetraazafulvalene subunit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970325
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