Diazonium ions, aromatic azides

The so-called transdiazotizations are mechanistically related to the introduction of diazonio groups using sulfonic acid azides. An aromatic diazonium ion forms a triazene (diazoamino compound) with an aromatic amine the triazene tautomerizes and dissociates at the Na-Np bond of the original diazonium ion. This reaction is important for the synthesis of the 4-aminobiphenyl-4,-diazonium ion, which cannot be obtained by direct (mono-)diazotization of 4,4 -diaminobiphenyl (Allan and... 

The reaction of azide ions with aliphatic diazo compounds was investigated by Kirmse et al. (1979 for a discussion see Zollinger, 1995, Sec. 6.1). Here we mention only that cyclopropanediazonium ions react similarly to the aromatic diazonium ions, i.e., by TV-coupling to 1-cyclopropylpentazene and dediazoniation to cyclopropyl azide. In about 60% of the 1-cyclopropylpentazene the cyclopropyl azide is formed directly by dediazoniation of the original diazonio group, while in 40% the route is via the cyclopropylpentazole. 

A second group of aromatic substitution reactions involves aryl diazonium ions. As for electrophilic aromatic substitution, many of the reactions of aromatic diazonium ions date to the nineteenth century. There have continued to be methodological developments for substitution reactions of diazonium intermediates. These reactions provide routes to aryl halides, cyanides, and azides, phenols, and in some cases to alkenyl derivatives. 

Other Substituted Diazonium Ions. A series of aminodiazonium ions have been prepared under superacidic conditions [Eq. (4.141)]. Schmidt495 described the preparation and IR spectra of protonated hydrazoic acid 212 and methylazide as their hexachloroantimonate salts. Olah and co-workers496 have carried out a comprehensive study on aminodiazonium ions (protonated azides) by H, 13C, and 15N NMR spectroscopy. Even the electrophilic aminating ability of aromatics of 212 has been explored.496 The tetrachloroaluminate salt of 212 has also been prepared496... 

Aryl substrates containing suitable leaving and activating groups react readily with moderately strong nucleophiles such as azide ion and a number of aromatic azides have been prepared in this manner (Table 4). Such Ar reactions complement the synthesis of aromatic azides from diazonium compounds zind are of particular value in forming azides of heteroaromatic systems in which dizizotization procedures are unsatisfactory,... 

Aromatic azides may be synthesized from diazonium compounds using hydrazoic acid or azide ion as the nucleophile (equation 133). 

In an interesting technique for the preparation of aromatic azides, aryl diazonium salts are treated with azide ions." "" At least in a very formal sense, one can consider this reaction as a substitution process, although the real mechanism of this transformation is much more complicated. An excellent... 

In diazo transfer reactions both N-atoms, i. e., the entire diazo group, are introduced into a suitable substrate from a diazo donor (2-46). In most cases this transfer reagent is a sulfonyl azide (Y=N2 = Ar-S02N=N2 or R-S02-N=N2), from which the N(yff)- and N(y)-atoms will form the diazo group in the product. There are, however, also cases in which the diazo group of an aromatic diazonium ion or of a diazoalkene is transferred. Such examples are of minor importance. 

Diazotization of aromatic and heteroaromatic amines and subsequent treatment with sodium azide has been used for the synthesis of aryl azide (Scheme 3.34). This reaction does not involve the cleavage of the carbon-heteroatom bond. Instead, after the addition of the azide onto the diazonium ion, an open pentazene or a cyclic pentazole is formed, followed by the release of nitrogen to yield the aryl This approach can be... 

The synthesis of azidocycloimonium fluoborates, compounds which possess a quasi-aromatic heterocyclic nucleus, has been reported by BalU and Kersting . Halogen atoms adjacent to quaternary nitrogens in heteroaromatic salts such as 154 157 undergo replacement by azide ion at low temperatures to produce the resonance stabilized azidinium salts (158). On the basis of infrared studies and reactivity towards nucleophiles, Balli has suggested that these salts are best considered as iV-diazonium compounds... 

Fuseo et al., 1963 Rosenberger et al., 1964). As a reaction of general scope, it was not recognized for another decade. One reason may have been that diazocyclopenta-diene was considered — in our opinion correctly — as an aromatic diazonium zwit-terion. Furthermore, diazo group transfer from 4-toluenesulfonyl azide to phenoxide ions yields also aromatic diazo compounds (see Zollinger, 1994, Sect. 2.6). The method was, however, not yet tested at that time for the synthesis of typical diazoalkanes. 

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