Alkoxy-l,2,3,4-thiatriazoles

Sodium azide does not react with carbonyl sulfide to form 5-hydroxy-1,2,3,4-thiatriazole, nor with carboxymethyl xanthates, RO-CS SCH2COOH, to form 5-alkoxy-l,2,3,4-thiatriazoles. The latter, however, could be prepared from xanthogenhydrazides (RO-CS NHNH2) and nitrous acid. They are very unstable and may decompose explosively at room temperature only the ethoxy compound (6) has been examined in detail. This is a solid which decomposes rapidly at room temperature and even at 0°C is transformed after some months into a mixture of sulfur and triethyl isocyanurate. In ethereal solution at 20° C the decomposition takes place according to Eq. (16) 

As mentioned in Section I, the product obtained by Freund and Schander in 1896 by the reaction of thiosemicarbazide with one 

Substituents on amino group Melting point, ° C References 

From 4-phenylthiosemicarbazide Freund and HempeH obtained a product to which they assigned the structure of a tetrazolinethione. When heated in alkaline solution it was isomerized to a compound which, on the basis of adequate chemical evidence, was considered to be 5-mercapto-l-phenyltetrazole. According to Lieber and Ramach-andran, however, the initial product is 5-phenylamino-l,2,3,4-thia-triazole. Lieber and Slutkin have also converted some di(thiosemi- 

Accordingly, 5-substituted-amino-l,2,3,4-thiatriazoles (Tables III and IV) are formed quite generally from 4-substituted-thiosemicarb-azides. When the substituent is an aryl group these initial products are isomerized to 5-mercaptotetrazoles on treatment with alkali whereas this is not the case when the substituent is an alkyl group. 

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Xanthogenhydrazides, RO-CS NHNH2, give 5-alkoxy-l,2,3,4-thiatriazoles on treatment with nitrous acid, and dithiocarbazinic esters, RS-CS-NHNH2, give 5-alkylmercapto-l,2,3,4-thiatriazoles. ... 

Of the higher aza-compounds, only derivatives of 1,2,3,4-thiatriazole are well defined, but even here alkyl derivatives decompose at or below 0 C, though 5-aryl- and amino derivatives are generally fairly stable. Many other derivatives are, however, dangerously explosive, for example the 5-chloro and thiolate derivatives. The controlled decomposition of 5-alkoxy-l,2,3,4-thiatriazoles (for example the 5-ethoxy-derivative in ether at 20 C) has been recommended as the best preparation of pure alkyl cyanates thermal decomposition of 5-aryl compounds gives the corresponding nitrile. ... 

The highly explosive 5-chloro-l, 2,3,4-thiatriazole (prepared from thiophosgene and sodium azide) has been used for the preparation of 5-substituted 1,2,3,4-aminothiatriazoles and certain 5-alkoxy-thiatriazoles (Section 4.19.7). Great care should be exercised in handling any reaction product of thiophosgene and azide ion. In particular the reaction of 5-chloro-l,2,3,4-thiatriazole with azide ion yielded a product assumed to be 5-azido-l,2,3,4-thiatriazole which gave rise to explosion as a suspension in water (61J0C1644>. 

The only data on hand to distinguish between the two mechanisms are the kinetic studies of Jensen on a variety of 5-alkoxy- and on 5-phenoxy-l,2,3,4-thiatriazoles. The energies of activation and the activation entropies are nearly the same for all compounds studied = 24-6 kcal mole" and = 4-4 e.u. Jensen interprets this as indicating a stepwise mechanism, in which thioacyl azide is formed in... 

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