Mechanistische und präparative Aspekte der Chemie der Vinylkationen

Hanack, Michael

doi:10.1002/ange.19780900506

Cited by 44 publications

(16 citation statements)

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“…This ion is precipitated by the readily soluble isopentadecylammonium hexachloroantimonate as the salt (13)[331. The replacement of fluorine by chlorine, necessary for the formation of (13), probably takes place in the resonance-stabilized cationic intermediate (30 by a tert-butyl group, or if both chlorine atoms are replaced by a tert-butyl group and bromine, or by the I-adamantyl substituent and bromine, the thermal stability of the resulting diazonium salt is decreased. A similar introduction of a trichlorovinyl or 2,2'-biphenylyl group decreases the stability to a smaller extent.…”

Section: Alkenediazonium Salts From Sulfonylhydrazonesmentioning

confidence: 98%

Section: Diazonium Salts From Aldehyde Sulfonylhydrazones[' 91mentioning

confidence: 99%

“…The protonation product ( 3 2 ) of the azo compound (17) [= (15 a ) ] , which corresponds to the short-lived intermediates (30) and (31), can be observed directly in sulfuric acid, since transformation of the dark red (32) into the olive-green cation of (19) goes to completion only after one or two minutes even at room temperature.…”

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confidence: 99%

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Alkenediazonium Salts: A New Chapter of Classical Organic Chemistry

Bott

1979

Angew. Chem. Int. Ed. Engl.

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Whereas the protonation of a-diazo-0-diketones and r-diazo-P-oxo esters with hydrogen chloride and antimony pentachloride yields the corresponding hydroxyalkenediazonium hexachloroantimonates, the "acid-sensitive'' r-diazomonocarbonyl compounds can be transformed into resonance-stabilized alkenediazonium salts by an analogous 0-alkylation with triethyloxonium hexachloroantimonate. A general route for synthesizing these compounds consists in the transformation of the p-toluenesulfonylhydrazones of a-halogenated aldehydes and ketones with Lewis acids. Alkenediazonium ions which are not resonance stabilized can be isolated at room temperature only if their decomposition at higher temperatures leads, uia evolution of nitrogen, to vinyl cations in particularly high energy levels. Facile substitution reactions at the CC double bond with anisole and methanol demonstrate the strongly electrophilic nature of alkenediazonium salts. When electron-donating substituents are attached to C2 of an ethylenediazonium ion, the bond order of the NN triple bond can be reduced to a level comparable with that in diazoacetic ester.

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Section: Alkenediazonium Salts From Sulfonylhydrazonesmentioning

confidence: 98%

Section: Diazonium Salts From Aldehyde Sulfonylhydrazones[' 91mentioning

confidence: 99%

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Alkenediazonium Salts: A New Chapter of Classical Organic Chemistry

Bott

1979

Angew. Chem. Int. Ed. Engl.

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“…[18,19] Collapse of A by C À C bond formation would result in assembly of the first ring and creating of the new and reactive vinyl cation B. [20] The latter affords 2 c by subsequent ring closure involving participation of the phenyl group attached to sulfur.…”

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confidence: 99%

A Novel Domino Reaction: Cyclization of Alkynyl Sulfides by Reaction with IPy2BF4

Barluenga

Romanelli

Alvarez‐Garcia

et al. 1998

Angewandte Chemie International Edition

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“…[16] Zur Erklärung unserer Ergebnisse postulieren wir einen Reaktionsmechanismus, demzufolge zunächst das elektrophile Iodatom an der Dreifachbindung von 1 c angreift, wobei das relativ stabile, in a-Stellung Schwefel-substituierte Vinylkation A entsteht (Schema 3). [17±19] Dieses reagiert unter C-C-Bindungsknüpfung, wobei der erste Ring geschlossen wird und sich das reaktive Vinylkation B bildet, [20] das sich in einer weiteren Cyclisierung unter Beteiligung der Schwefel-gebundenen Phenylgruppe zu 2 c umwandelt. Wir haben hiermit eine neuartige und präparativ wertvolle intramolekulare exo-endo-Cyclisierung von a,w-Diinen entwickelt und die Anwendbarkeit intermolekularer Kupplungen untersucht.…”

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