Triazoles

Triazoles (pyrro-a and (3'-diazoles), in organic chemistry, a series of heterocyclic compounds containing the ring complex (annexed formula). Derivatives were obtained by J. A. Bladin HC -N (Ber., 1892, 25, p. 183) by the action of acetic)NH anhydride on dicyanophenylhydrazine (formed N: CH from cyanogen and phenylhydrazine), the resulting acetyl derivative losing water and yielding phenylmethylcyanotriazole, which, on hydrolysis, gives the free acid. By eliminating carbon dioxide, phenylmethyltriazole results. In a similar manner, formic acid and dicyanophenylhydrazine yields a phenyl-triazole carboxylic acid, in which the phenyl group may be nitrated, the nitro group reduced to the amino group, and the product oxidized to a triazole carboxylic acid, which, by elimination of carbon dioxide, yields the free triazole: HO 2 CC=N H02CC =N ,NPh-> N :CH N :CH They also result when the acidylthiosemicarbazides are strongly heated, the mercapto-triazoles so formed being converted into triazoles on oxidation with hydrogen peroxide (M. Freund, Ber., 1896, 29, p. 2483); by the condensation of hydrazides with acid amides; and by the distillation of the triazolones (see below) with phosphorus pentasulphide. The triazoles behave as weak bases, the imido-hydrogen being replaceable by metal.

The keto-dihydrotriazoles or triazolones are obtained by the action of hydrazines on acetyl urethane (A. Andreocci, Ber., 1892, 25, p. 225). These compounds may be considered as 5-triazolones, a series of isomeric 3-triazolones resulting from the condensation of phenylsemicarbazide with aromatic aldehydes in the presence of an oxidant. The diketotetrahydrotriazoles, or urazoles, are formed by condensing urea derivatives with hydrazine salts, urazole itself resulting by the action of urea or biuret on hydrazine or its salts. It behaves as a strong acid and on treatment with phosphorus pentachloride at high temperatures gives triazole.

HC=N CONH CONH HNCO ›NH, N=CH? NH' NHCO ? NH.

5-Triazolone. 3-Triazolone. Urazole.

Isomeric triazoles of the following constitutions are known:- HC :N N :CH N-N?

HC:N ›NH N:CH ›NH HC:CH" Osotriazole (aa'). Iminotriazole OW). a(3-Triazole.

The osotriazoles are obtained by heating the osazones of orthodiketones with mineral acids; by the action of acetic anhydride on the hydrazoximes of orthodiketones, or by condensing diazo-methane with cyanogen derivatives (A. Peratones and E. Azzarello, R. Acad. Lincei, 1907 [v.], 16, pp. 237, 318). They are feeble bases which distil unchanged. The ring is very stable to most reagents. The iminobiazoles are formed by conversion of diacylhydrazines into iminochlorides which with ammonia or bases yield the required triazoles (R. Stolle, Journ. prak. Chem., 1906 [ii.], 74, pp. I, 13). M. Busch (Ber., 1905, 38, pp. 856, 4049) has isolated a series of bridged ring compounds which he describes as endo-iminodihydrotriazoles, the triphenyl derivative (annexed formula) being prepared by condensing triphenylaminoguanidine with formic acid. The nitrate of this base (known as nitron) is so insoluble that nitrates may be gravimetrically estimated with its help. These bases combine with the alkyl iodides to yield quaternary ammonium salts.