Alkenediazonium Salts: A New Chapter of Classical Organic Chemistry

Abstract

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.

Divergent Asymmetric Synthesis of Polycyclic Compounds via Vinyl Triazenes

“…Vinyl triazenes are expected to display a similar reactivity pattern. Protonation of the triazene, followed by cleavage of the nitrogen–nitrogen bond, would give unstable vinyl diazonium compounds, which could be intercepted with different nucleophiles. In fact, vinyl triazenes have been used successfully as masked vinyl cations, but as compared to the well‐established chemistry of 1‐aryl triazenes, there are only very scarce reports on the synthesis and reactivity of vinyl triazenes .…”

Reactions of Alkenediazonium Salts. Part 1. 2,2‐Diethoxyethene‐diazonium hexachloroantimonate: A diazonium, a carbenium or an oxonium salt?

“…This simple picture becomes, however, more complicated if the analogous reaction of 1 with methanol is considered. In this case, one would expect the formation of ethyl methoxyacetate (5) and/or its transesterification product, methyl methoxyacetate (6). Compound 6 was indeed found, but instead of 5 methyl ethoxyacetate (7) was identified (GUMS).…”

“…Relatively few experimental data are available for reactions of substituted vinyldiazonium ions. They indicate ambient reactivities depending on substituents and reagents [ 5 ] ; for example, 2-halosubstituted vinyldiazonium ions react with nucleophiles at C(2) before they lose N2 in a dediazoniation [ 6 ] .…”

“…Structure l a seems to be supported by the high N=N stretching frequency as compared to ethyl diazoacetate [7], but no other chemical or physical indications are available. Compound 1 decomposes under the influence of various nucleophiles [ 5 ] , but the decomposition products have so far not been elucidated. Saalfrank & Ackermann reported [9] [ 101 that 1 reacts with primary amines to give triazoles.…”

Divergent Asymmetric Synthesis of Polycyclic Compounds via Vinyl Triazenes

“…[1] Numerous functional groups can be introduced in that fashion, thus making aromatic triazenes interesting and valuable intermediates for the latestage diversification of arenes.Vinyl triazenes are expected to display as imilar reactivity pattern. Protonation of the triazene,f ollowed by cleavage of the nitrogen-nitrogen bond, would give unstable vinyl diazonium compounds, [3] which could be intercepted with different nucleophiles.I n fact, vinyl triazenes have been used successfully as masked vinyl cations, [4] but as compared to the well-established chemistry of 1-aryl triazenes,t here are only very scarce reports on the synthesis and reactivity of vinyl triazenes. [4][5][6] Notably,t he utilization of alkenyl triazenes as intermediates for divergent organic syntheses is completely unexplored.…”