Hydrazoic acid and its derivatives

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

This reaction was first carried out by Noelting and Michel and may be used in all cases in which a primary amine undergoes diazotiza-tion, except where the dizizonium compound subsequendy reacts before hydi oic acid is introduced into the reaction medium (e.g. diazotization of o-aminodiphenylamine results in spontaneous cycliza-tion of the diazonium compound with the formation ofl-phenylbenzo-triazole ). 

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. 

257 which were formed in 85% and 15% yield respectively. It is significant in the light of the work of Lewis and Johnson that product 

These conclusions were subsequently confirmed by Huisgen, Ugi and collaborators who isolated the intermediate pentazoles and 

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The formation of hydrazoic acid and its derivatives together with ammonia from diazo compounds under the influence of hydrazine or its derivatives was explained by Thiele [68]. At an intermediate stage a diazohydrazine, e.g. C6H5N2NHNH2, is formed which then undergoes decomposition according to two parallel reactions ... 

In this chapter, we first describe the successful methods for the hydroazidation of a,P-unsaturated carbonyl compounds. The classic approach for the addition of hydrazoic acid and its derivatives onto non-activated double bonds is then examined. In the last section, we present our own work in this area and our progress towards a general method for the hydroazidation of olefins. 

Addition of Hydrazoic Acid and Its Derivatives to Non-Activated Olefins... 

Audrieth, L. F. Hydrazoic acid and its inorganic derivatives. Chem. Rev. 

Of the aromatic dibasic acids, the three phthalic acids on treatment with hydrazoic acid yield the corresponding aminobenzoic acids with mere traces of the diaminobenzenes. > Anthranilic acid and its derivatives in which one hydrogen on the amino group is replaced by acetyl, benzoyl, or p-toluyl are inert to hydrazoic acid. These compounds thus resemble in activity a-amino acids and their derivatives in the aliphatic series. The following pyridine and quinoline acids resemble -amino acids and also do not react pyridine-2-carboxylic acid, pyridine-2,3-... 

There are two methods for the manufacture of hydrazoic acid or its salts. One is derived from a number of investigations by Curtius [1] and is based on the action of nitrous acid on hydrazine ... 

Production of 4,4 -diaminobiphenyl (benzidine) and its derivatives is normally carried out by reduction of the corresponding nitrobenzenes with zinc powder in high-boiling solvents, such as o-dichlorobenzene, to yield the respective hydrazo-benzene, which is converted into the benzidine form in acid solution. Since benzidine is carcinogenic, special care should be taken in its production manufacture is banned in many countries, because of its toxicity. 

Most of the important general methods of forming IZf-triazole derivatives involve azides several reviews discuss aspects of the formation of triazoles in this way. a-Diketones are also important precursors of both H- and 2 f-triazoles. Triazoles unsubstituted on nitrogen can be prepared by the direct addition of hydrazoic acid or of azide ion, but it is often more convenient to obtain these compounds by removal of a substituent from a H- or 2if-substituted triazole (Section IV, E). 

The organic derivatives of hydrazoic acid which contain an aromatic ring with nitro groups comprise an important group of initiators. Picryl azide (VII), m.p. 89-90°C is a typical example. It has been prepared both by the action of nitrous acid on trinitrophenylhydrazine (Purgotti [154], Schrader [155] and Korczynski [156]) and by the action of sodium azide on picryl chloride. Rathsburg [157] suggested... 

Analogously, Bognar and coworkers45-46 prepared the same thiourea derivative 33, and synthesized some other N-glycosyl heterocyclic derivatives, such as thiazole 36, 1,3,4-thiadiazole 38, and 1,2,3,4-thiatriazole 39, using as the starting material isothiocyanate 2, or its ureido (34) or semicar-bazide (37) analogs. It is noteworthy that treatment of semicarbazide 37 with a nitroso acid at 0° afforded the 1,2,3,4-thiatriazole derivative 39 by addition and cyclization. The same 1,2,3,4-thiatriazole derivative 39 was obtained by treatment of isothiocyanate 2 with hydrazoic acid. 

This synthesis of hydrazoic acid, said D. I. Mendeleeff, marks one of the most important achievements of the year 1890. This remarkable acid has no structural parallel among the inorganic acids, and in that respect it occupies an isolated position. The phenyl derivative of this acid, CflHg.N3, was discovered by J. P. Griess in 1867. 

In connection with the hydrolysis of benzoylazide, it is interesting to recall that triazo-benzene or phenylazide, C H6N4, is so stable that it cannot be directly hydrolyzed by the action of acids on alkalies to form hydrazoic acid, but E. NSiting and E. Grandmougin were able to show that if an acidic radicle, say a nitro-group, be introduced into the phenyl radicle—say by treatment with nitric acid whereby p-nitrophenylazide, C,H., N02)N3, is formed—the product is readily hydrolyzed by alkali-lye. Similar remarks apply to the ortho-derivatives, while, curiously enough, the meta-derivatives are not so readily hydrolyzed. 

The compound hydrazoic acid, HN3, is 98-percent nitrogen. In the pure state it is, as expected, explosive but it can be studied in aqueous solution. Numerous salts and organic derivatives (both called azides) have been made. The sodium salt can be prepared by reaction of nitrous oxide with the strong base sodamide. Under the anhydrous conditions used for the reaction, the adduct (or perhaps its tautomer) loses water to form the azide ion as shown ... 

The instability of tert-butyl chioroformate limits its use for preparing Boc derivatives.102 /ert-Butyl fluoroformate (bp 40-42 aC/23.3 kPa)103104 is more stable than the chloro derivative and more reactive than rm-butyl azidoformate (HAZARD). Both reagents should be prepared afresh. rm-Butyl azidoformate (bp 36.5-37.5 °C/1.3 kPa)105 has the added frisson of being explosive hence, it should be prepared in situ from the reaction of Boc-hydrazide with nitrous acid and used without purification. Moreover, the by-product of aqueous workup, hydrazoic acid, is highly toxic. 

Hydrazoic Acid.—The third compound, which is the other one containing only nitrogen and hydrogen, is not an ammonia derivative. It is known as hydrazoic acid or tri-azoic acid. Its formula is N3H. It is a mono-basic acid while ammonia, NH3, is a base. It forms a salt with ammonia, NH4N3, ammonium hydrazoate. Hydrazoic acid was also discovered by Curtius in 1890. 

It is noteworthy that compounds such as cinnamaldehyde and cinnamic acid derivatives, in which the conjugation is extended into a benzene ring, do not add hydrazoic acid even in abnormally vigorous conditions It has been suggested that the extension of con-... 

Ketene also appears to react with hydrazoic acid according to the general mechanism outlined in equation (88). Carbamoyl azides are produced and it is thought that the reaction proceeds by initial protonation and subsequent attack by azide ion to afford an acyl azide further reaction of the derived isocyanate would then lead to the observed product (equation 90). 

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