Reaction of 5-halo-1,2,3-thiadiazoles with arylenediamines as a new approach to tricyclic 1,3,6-thiadiazepines

Abstract

A multistep reaction of 5-halo-1,2,3-thiadiazoles and 1,2-phenylenediamines provides a new route to fused 1,3,6thiadiazepines. The overall process consists of the known stepwise formation of 5-[1-(2-aminophenyl)-1,2,3-triazol-5ylsulfanyl]-1,2,3-thiadiazole, and a novel ring transformation which involves the Smiles and Dimroth rearrangements followed by an intramolecular nucleophilic substitution of the thiol group, affording di[1,2,3]triazolo[1,5-a:5Ј,1Ј-d ]-[3,1,5]benzothiadiazepines. The influence of the substituents on the 1,2,3-thiadiazole and phenyl rings on this reaction was discussed.

Thiadiazoles

“…The transformation of hydrazones 195 into 1,2,3-triazoles 196 by treatment with PCl 5 could proceed by the same reaction route, although the mechanism has not been perfectly elucidated (Scheme 14.49) [107,108].…”

“…A double Dimroth rearrangement has been reported for the conversion of ethylene bis(thiadiazol-5-amine) (197) into the intermediate bis thiol, which undergoes an intramolecular nucleophilic substitution reaction with loss of H 2 S to give tricyclic triazole 199 (Scheme 14.50) [108]. Oxidation of 1,2,3-benzothiadiazole 9 with hydrogen peroxide leads to 1-oxo-1,2,3-benzothiadiazole (216), which thermally decomposes into benzoxathiete 217 or its valence tautomer 218.…”

Condensed 1,2,3-triazoles (review)

“…When triazoledicarbohydrazide 87 was heated in 10% hydrochloric acid the triazolopyridazinedione 88 was obtained [62,63]. The action of triethylamine on 5-[1-(2-aminophenyl)-1,2,3-triazol-5-ylsulfanyl]-1,2,3-thiadiazole 89 leads to intramolecular nucleophilic substitution of the thiol group, accompanied by rearrangement of the thiadiazole ring to a triazole ring and the release of hydrogen sulfide with the formation of di[1,2,3]triazolo-[1,5-a:5',1'-d] [3,1,5]benzothiadiazepine 90 [64]. Treatment of the amine 96 with acetic anhydride followed by reaction with sodium hydride in DMF leads to the formation of 6-aminopyrazolo [3,4-d][1,2,3]triazole 95 [67].…”

Chemical Properties of 1,2,3‐Thiadiazoles

“…Most probably, a double Dimroth rearrangement occurs in the first step of the novel transformation of bisthiadiazol-5-aminoethane 76 to tricyclic triazole 77. 43 The intermediate bisthiol 77 then undergoes an intramolecular nucleophilic substitution reaction, with loss of hydrogen sulfide.…”