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  • 1
    Electronic Resource
    Electronic Resource
    On the Reaction of 1-Aza-2-azoniaallene Salts with Carbodiimides (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2519-2524 
    Details
    ISSN: 0009-2940
    Keywords: 1-Aza-2-azoniaallene cations ; Carbodiimides ; 1H-1,2,4-Triazolium salts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Aza-2-azoniaallene cations 3, prepared in situ from geminal (chloroalkyl)azo compounds 2, react with carbodiimides 4 to give 4,5-dihydro-5-imino-1H-1,2,4-triazolium salts 7. An X-ray structural analysis was carried out for 71. According to AM1 calculations the cycloaddition of carbodiimides to 1-aza-2-azoniaallene cations occurs in a nonconcerted manner via cyanamidium cations 5 as intermediates. Hetero-Wagner-Meerwein rearrangements of the primary cycloadducts 6 provide the final products 7.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261128
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  • 2
    Electronic Resource
    Electronic Resource
    On the Reaction of 1-Aza-2-azoniaallene Salts with Acetylenes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 541-547 
    Details
    ISSN: 0009-2940
    Keywords: 1-Aza-2-azoniaallene cations ; Acetylenes ; 1H-Pyrazolium salts ; 4H-Pyrazolium salts ; [1,3]-Dipolar cycloadditions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Aza-2-azoniaallene cations 3, prepared in situ from geminal chloro(alkylazo) compounds 2, react with acetylenes 4 to give either 1H-pyrazolium salts 6 or 4H-pyrazolium salts 7 or mixtures of both. 4H-Pyrazolium salts with a hydrogen atom attached to C(4) rearrange to the protonated 1H-pyrazoles 8, from which the free bases 9 are obtained upon treatment with aqueous NaOH. According to AM1 calculations the cycloaddition of acetylenes to 1-aza-2-azoniaallene cations is a concerted process, which can be classified as a “1,3-dipolar cycloaddition with reverse electron demand”. The cycloaddition forming the intermediates 5 is followed by an [1,2] alkyl shift to furnish the final products 6-8. The direction of the [1,2] shift has been found to be governed by subtle steric effects.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270313
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  • 3
    Electronic Resource
    Electronic Resource
    On the Reaction of 1-Aza-2-azoniaallene Salts with Isocyanates (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 947-953 
    Details
    ISSN: 0009-2940
    Keywords: 1-Aza-2-azoniaallene cations ; Isocyanates ; 4,5-Dihydro-5-oxo-1,2,4-triazolium salts ; Cinnolinium salts ; Cycloadditions ; Calculations, AM1 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Aza-2-azoniaallene salts 3, prepared in situ from geminal chloroalkylazo compounds 2 with Lewis acids, react with isocyanates 4 to give 4,5-dihydro-5-oxo-3H-1,2,4-triazolium salts 6 and 4,5-dihydro-5-oxo-1H-1,2,4-triazolium salts 7, respectively. The intramolecular cyclization of 3u opens a new route to cinnolinium salts 11. Allenes 3 react with isobutene to give pyrazolium salts 8. According to AM1 calculations the cycloadditions of 3 to isocyanates proceed in two steps via acylium salts 5 as intermediates. Mechanistically, the rearrangements 6 → 7 resemble Wagner-Meerwein rearrangements rather than pericyclic [1,5]-sigmatropic shifts.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270524
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