From 1,2,3,4-thiatriazoles

Type A Syntheses [N—C—S + C—N]. From 1,2,3A-thiatriazoles. Two independent reports of the production of a variety of 1,2,4-thiadiazolidines from a reactive species (37) arising from the thermolysis of 4-alkyl-5-arylsulphonyl-imino-4,5-dihydro-l,2,3,4-thiatriazoles (36) have appeared. The intermediates (37) undergo 1,2-addition with isocyanates or carbodi-imides to afford excellent yields of the 3-oxo- (38) or 3-imino-1,2,4-thiadiazolidines (39). Their structure was confirmed by alternative established syntheses. 

4-Thiadiazoles have been isolated as minor by-products in certain reactions of 5-(dialkylamino)-3-imino-l,2,4-dithiazoles in aceto- or benzo-nitrile as a result of 1,3-dipolar addition of the solvent. 

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Phenylthiazirine (40) can be isolated as an intermediate in the photolysis of 5-phenyl-1,2,3,4-thiatriazole and also from other five-membered ring heterocycles capable of losing stable fragments see Scheme 2 (81AHC(28)231). Photolysis of 5-phenylthiatriazole in the presence of cyclohexene yields cyclohexene episulfide (60CB2353) by trapping the sulfur atom. 

From thiohydrazides, R CS NHNHg, in which R is an aromatic or a heterocyclic group, 1,2,3,4-thiatriazoles may in general be obtained in good yield by treatment with nitrous acid. ... 

From 5-chloro-l,2,3,4-thiatriazole and secondary amines Lieber et al. have prepared some 5-disubstituted-amino-l,2,3,4-thiatria-zoles. It seems possible that several other types of compounds could be prepared from 5-chlorothiatriazole, which, however, is very unstable (explosive). 

The free acid, l,2,3,4-thiatriazole-5-thiol, may be prepared from hydrogen azide and carbon disulfide, but the simplest way to obtain the acid is to treat a chilled solution of the sodium salt with concen-... 

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)... 

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. 

However, Sahasrabudhey thinks that the compound formed from 5-amino-1,2,3,4-thiatriazole does not have the composition CSN2H3CI, but (CSN2H4C1)2, and is in fact the dihydrochloride of formamidine disulfide, the oxidation product of thiourea. This con-... 

Table III Since this table was prepared R. G. Dubenko, I. N. Berzina, and P. S. Pel kis [Zh. Obshch. Khim. 33, 274 (1963)] have described eighteen 5-aryl-amino-1,2,3,4-thiatriazoles of which only five are listed in Table III. The melting points given for these five compoimds differ considerably from those listed in Table lil o-tolyl, 117-118° p-tolyl, 151-152° o-methoxyphenyl, 109-110° p-methoxyphenyl, 129-130° and p-chlorophenyl, 162-163°.

The third volume of this series covers three specific groups of compounds the carbolines (reviewed by R. A. Abramovitch and I. D. Spenser), the thiatriazoles (K. A. Jensen and C. Pedersen), and the pentazoles (I. Ugi). The remaining four chapters deal with topics of general chemical interest from the heterocyclic viewpoint the quaternization of heterocyclics (G. F. Duffin), carbene reactions (C. W. Rees and C. E. Smithen), applications of the Hammett equation (H. H. Jaffe and H. Lloyd Jones), and some aspects of the nucleophilic substitution of heterocyclic azines (G. Rluminati). 

Addition of thiophosgene to the reaction mixture of ImCSIm and trimethylsilylazide causes the yield to become quantitative.11301,11323 In the conversion with trimethylsilyl azide the required ImCSIm could also be made in situ from trimethylsilylimidazole and thiophosgene, giving the thiatriazoles in 70—80% yield.11321... 

Evidence for the formation of thiiren by photoelimination of nitrogen from 1,2,3-thiadiazoles has been described,351 and several thiirens, prepared in this way, have been identified in an argon matrix at 8K.352 Phenylthiazirine (422) appears to be an intermediate in the related transformation of 5-phenyl-l,2,3,4-thiatriazole (423) into benzonitrile sulfide (424),353 and further... 

While the neutral 1,2,3,4-oxatriazoles (1) still await synthesis, some of their properties have been predicted by theoretical calculations. AMI calculations combined with a principal component analysis loading data from other related heteroaromatics have been used to estimate geometric characteristics, aromaticity, energy of formation, and N chemical shifts <90JPR885>. The oxatriazoles (1) and (7) and the 1,2,3,5-thiatriazoles, which also have not been prepared, are calculated to be in the group with the lowest classical and magnetic aromaticity. 

Thio-l,2,3,4-thiatriazole was originally thought to have an open structure, azidodithiocarbonic acid, but Lieber et al. concluded from infrared spectroscopic measurements that it aetually possesses the closed 1,2,3,4-thiatriazole structure <57JOC1750>. 

As an overall conclusion two routes seem to operate in the thermal degradation of 1,2,3,4-thiatriazoles a major route leading to nitrile (28) and dinitrogen sulfide (29) (Equation (1)), and another leading to isothiocyanate (27) most likely via thioacyl azide (24) from the Z-form (32) and presumably accompanied by formation of nitrile (28) from the -form (31). 

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>. 

L abbe and Vermeulen have proposed salts of type (105) as key intermediates in the reactions of 5-aminothiatriazole (10) with acyl chlorides (Scheme 19) <81BSB89>. The intermediate is expected to undergo cyclization to 3-imino-A -l,2,4-oxathiazoline (106) followed by reaction with a second molecule of acyl chloride to give the corresponding thiapentalene (107). The formation of the 1,2,4-thiadiazole (104) was explained as a result of an addition of V-acetylcyanamide (108), formed by extrusion of nitrogen and loss of sulfur from 5-acetamido-1,2,3,4-thiatriazole, to the key intermediate... 

Graubaum and Martin isolated the acetylhydrazino thiatriazole (142) in approximately 50% yield from the reaction of 5-hydrazinothiatriazole (133) with acetic anhydride <85ZC136>. On heating to 40 °C, (142) extruded nitrogen and sulfur to give 2-amino-5-methyl-1,3,4-oxadiazole (143) (Scheme 29). 

Thiatriazole-5-thiol and its salts are readily obtained from the water-soluble alkali or alkaline earth azides with CS2 at 40 °C <64AHC(3)263>. However, these salts should be handled with extreme care as violent explosions have been reported when the alkali salts are spread on a porous plate or rubbed with a spatula. The slightly soluble heavy-metal salts are very sensitive to shock even under water. An improved method for the preparation and storage of sodium thiatriazole-5-thiolate has been reported. The free acid is obtained by addition of concentrated hydrochloric acid to a chilled solution of the sodium salt but can also be prepared from hydrazoic acid and carbon disulfide (Scheme 38). 

Allyloxy- (146) and propargyloxythiatriazoles (154) are obtained in a similar way by treating the corresponding chlorothioformates with sodium azide (92AG865). However, substituted allyloxy (150) and propargyloxy thiatriazoles (158) were obtained from 5-chloro-l,2,3,4-thiatriazole (175) in the presence of sodium hydride and the corresponding alcohols (35-70% yield) <92AG865>. 

Upon acylation of the copper complex with benzoyl chloride the corresponding 5-benzoylthio-1,2,3,4-thiatriazole is formed. The reaction product is (apparently) incorrectly assigned by the authors to 4-benzoyl-1,2,3,4-thiatriazole-5-thione based upon comparison with the product obtained from direct acylation of thiatriazol-5-thiol and citation of the older incorrect structure assignments. The thiothiatriazolato-copper(I) complexes are formulated as Cu-N(4) complexes. However, this assignment is based upon an IR band at 1200 cm attributed to a thiocarbonyl group, again upon comparison with the older literature. Further characterization therefore seems necessary. 

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