Azides and Diazonium Compounds

A reinvestigation of the reaction of hydrazoic acid with dimethyl acetylenedicar-boxylate has revealed that the enazide product is a mixture of E- and Z-stereoisomers.  

The attempted diazotization of (36) leads unexpectedly to a 65% yield of the diazodiketone (37), and other 3-substituted 2-amino-IH-phenalen-l-ones have also been found to undergo anomalous diazotization to diazodiketones in good yield. 

In a similar vein, 3-amino-2-nitrobenzofuran undergoes an anomalous reaction with ethylene oxide, in 90% acetic acid, to give the diazolactone (38).  

Celerier, E. Deloisy, P. Kapron, G. Lhommet, and P. Maitte, SynthesiSf 1981, 130. 

Polymer-anchored sulphonylazide has been compared with its efficiency in the diazo-group transfer reaction of tosylazide. Although yields with the polymeric reaction are slightly lower than with tosylazide, the greater thermostability of the polymeric reagent and ease of work-up make this an attractive synthetic alternative. 

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Since many azides may be explosive compounds, investigators planning to work with them should consult the literature and take special precautions. See Volume I, Chapter 15, Diazo and Diazonium Compounds, for additional information about diazo hydrocarbons. 

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,... 

Table 11. Synthesis of aryl azides from diazonium compounds and...

Hydrazino compounds can react with one or two equivalents of arenediazonium ions. In reactions of arylhydrazines without substituents at the P-nitrogen in mineral acid media the initial product, the 1,4-diaryltetraz-1-ene (6.24), disproportionates rapidly into aryl azide and amine (Scheme 6-17). As shown by 15N labeling experiments (Clusius and Craubner, 1955), equal amounts of all the products shown in Scheme 6-17 are obtained. In acetate buffer the reaction is regiospecifically different. The diazonium ion attacks the a-, not the P-nitrogen, and a 1,3-diaryltetraz-l-ene is formed (6.25). 

Both 2- and 3-azidodibenzothiophene have been prepared by the action of sodium azide on the appropriate diazonium compound (>90%). Heating 2-azidodibenzothiophene in polyphosphoric acid yields 2,2 -azodibenzothiophene (54%). ... 

A number of reactions of organomagnesium compounds with compounds containing nitrogen-nitrogen multiple bonds give products containing new carbon-nitrogen bonds [A, E], but few of them are useful in synthesis. The main exceptions are reactions with azides, and some reactions of diazonium salts. 

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... 

Boyer and Canter suggested that the reaction proceeds through the intervention of a triazene, and further implied that this intermediate is subsequently oxidized to the azide by halogen or the anion (equation 114). In support of this suggestion it has been observed that in the absence of oxidant some diazonium compounds form tri-azenes with ammonia. 

Methyl-, benzyl- and toluene-sulphonamide react with aromatic diazonium compounds to give isolable triazenes which decompose in the presence of alkali with the formation of the corresponding aromatic azide and the alkyl- or aryl-sulphinic acid salt . This sequence (equation 123), known as the Dutt-Wormall reaction, is mechanisti-... 

This procedure has found wdde application in the synthesis of aromatic and heteroaromatic azides the yields are usually high and often quantitative. General procedures have been developed by Smith and co-workers the method of choice mainly being determined by the basicity of the amine involved or the solubility of its salts. Weakly basic amines, for example, are diazotized with amyl nitrite in an acetic acid-concentrated sulphuric acid mixture and aqueous sodium azide is subsequently added. Amines which form insoluble salts with common mineral acids zu e converted to the more soluble 2-hydroxyethanesulphonic acid salts prior to diazotization. This procedure has been applied in the diazotization of the N-(aminophenyl)phthalimides (254). Treatment of the resulting diazonium compounds (255) with hydrazoic acid and removal of the protecting phthalimido group affords the otherwise inaccessible azidoanilines (equation 134). Some representative examples of azides recently synthesized by these methods, are shown in Table 11. 

Azo Compounds, Azirines, Diazirines, Diazo Compounds, Diazonium Salts, Azides,. V-Oxides, Nitrite Esters and Heteroaromatic Compounds Photofragmentation and Photorearrangement... 

The initial intent to cover the subject exhaustively had to be abandoned because of the overwhelming amount of relevant literature. The following reactions are not covered but are briefly discussed, with references to reviews and seminal papers, in the section on Comparison with Other Methods reactions of carbanions and enolates and their surrogates with nitrogen oxides, nitrite and nitrate esters, and nitroso and nitro compounds reactions of enolates with diazonium salts, including the Japp-Klingemann reaction the diazo transfer reaction except as it interferes with the synthesis of azides the animation of boranes and the Neber rearrangement. 

Several reviews have dealt with the photochemical reactions of the types of compounds included in this chapter. Alkynes, J. D. Coyle m The Chemistry of the Carbon-Carbon Triple Bond (Ed. S. Patai), Wiley, Chichester, 1978, p. 523 Nitriles, in The Chemistry of the Cyano Group, diazonium salts and diazo compounds by W. Ando, m The Chemistry of Diazonium and Diazo Groups (Ed. S. Patai), Wiley, Chichester, 1978, p. 341 and radiation chemistry by Z. B. Alfassi, m The Chemistry of Functional Groups, Supplement C(Eds. S. Patai and Z. Rappoport), Wiley, Chichester, 1983, p. 187. Azides have been the subject of another extensive review [E. F. Scriven and K. Turnbull, Chem. Rev., 88,298 (1988)]. In addition to these references, extensive information on the photochemical reactivity of such groups is to be found in the appropriate chapters in Volumes 1-24 of Photochemistry published by the Royal Society of Chemistry, London, from 1968-1993. 

You met diazonium salts in Chapter 22. Arene diazonium salts are stable compounds, but alkyl diazonium salts, which are formed by protonation of diazo compounds, are not. They decompose rapidly with loss of N2—this was how the carboxylic acid got methylated at the beginning of the chapter. Other relatives of the azo and diazo compounds are alkyl azides. Alkyl azides have three nitrogen atoms and are usually stable but azides of low molecular weight may explode on impact or heating. 

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