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  • 1
    Electronic Resource
    Electronic Resource
    On the Reaction of Nitrilium Salts with Heterocyclic Nitrones (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 243-250 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nitrilium hexachloroantimonates 1a-c react with pyridine N-oxides 2a, d, f, j, m, o to afford bicyclic 2,3-dihydropyridinium salts 5a-p. The constitution of 5f was secured by an X-ray crystallographic analysis. Compounds 5 proved to be thermally labile (23-82°C) rearranging to 2-acylamino- pyridinium salts 6a, f-i or decomposing to tars. The benzimidazole-3-oxide 7 reacts with nitrilium salts 1a, b to 2-acylaminobenzimidazoles 9a, b. The experimental results as well as AM1 calculations support a mechanism for the reaction of nitrilium cations with heterocyclic nitrones, which has originally been suggested by Abramovitch [25, 26].
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380149
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  • 2
    Electronic Resource
    Electronic Resource
    Neues aus der Chemie der IminiumsalzeDiesem Fortschrittsbericht liegt der Inhalt der am 23./24. 9. 1993 in Neresheim-Ohmenheim stattgefundenen „1. Fachtagung Iminiumsalze“ zu Grunde. (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 390-403 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recent Developments in Iminium Salt ChemistryIminium salts are of continuing interest as versatile building blocks in organic synthesis. This progress report from different laboratories highlights some current research activities in iminium salt chemistry. Several contributions focus on novel synthetic applications of isolable, functionalized iminium systems such as α,β-unsaturated iminium salts (e.g. vinamidinium, 3-trifloxy, 3-chloro-, 3-isocyanato- and 3-thiopropene iminium, as well as propyne iminium salts), furthermore on phosgene iminium chloride and trifluoromethyl-substituted iminium salts. Iminium intermediates occur in various synthetic transformations; for example, cyclopropane iminium ions are intermediates in nucleophilic substitution reactions at bicyclic aminocyclopropanes. Also reported is the synthesis of a variety of novel orthoamides and their use as synthetic building blocks. Research directed to the application of vinamidinium salts in materials science is also presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360503
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  • 3
    Electronic Resource
    Electronic Resource
    Meerwein's Catalytic Beckmann RearrangementPresented at the second conference on iminium salts, Stimpfach-Rechenberg, Germany, September 20-22, 1995 (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 460-467 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Meerwein recommended nitrilium salts (2) as catalysts for the Beckmann rearrangement of oximes (1) under neutral and water-free conditions. For the first time, primary adducts (Z)-(3) of oximes to nitrilium salts have been isolated. Reported are activation energies for Beckmann rearrangements of these adducts, and an X-ray structural analysis of (Z)-3a. Rearrangement of 3 produces mixtures of up to four different N-acylamidinium salts 5-8, which arise from fast reactions of primary-formed secondary amides (4) with nitrilium salts (2). Because of their ambident electrophilic character the N-acylamidinium salts react with excess of oxime not only to amides (4) but to mixtures of products. It is shown that nitrilium salts cannot be used as catalysts for the Beckmann rearrangement.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380188
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  • 4
    Electronic Resource
    Electronic Resource
    On the Reaction of Acylium Salts with Isocyanates (1995)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 385-390 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkyl isocyanates (3) react with acylium salts (2) in a 2:1 ratio to furnish 3,4-dihydro-2,4-dioxo-2H-1,3,5-oxadiazinium salts 4. These cyclic N-acyliminium salts are decomposed with catalytic amounts of water to give either oxadiazinium salts 5 or pyrimidinium salts 7. With aqueous base compounds 4 are transformed into acylureas 6. Hetero substituted open chain N-acyliminium salts (8a,11c,12c,13f,15g,16a) are produced from 4 by treatment with heteronucleophiles such as methanol, p-anisidine, p-cresol, thiophenol, 1,3-dimethylurea, or benzohydrazide, respectively. Excess of nucleophile furnishes further degradation products of 4, e.g. oxonium salts (9a) and iminium salts (14f).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19953370182
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    Paper (German National Licenses)
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