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Cyclization of thiohydrazonate esters and azo-hydrazone tautomerism of 2-arylhydrazono-3-oxo-1,4-benzothiazines

✍ Scribed by Ahmad S. Shawali; Said Elsheikh; Cyril Párkányi

Publisher
Journal of Heterocyclic Chemistry
Year
2003
Tongue
English
Weight
60 KB
Volume
40
Category
Article
ISSN
0022-152X

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✦ Synopsis

Abstract

Reaction of ethyl arylhydrazonochloroacetates (1) with 2‐aminothiophenol (2) in ethanol in the presence of triethylamine yielded the respective ethyl thiohydrazonate esters (3). Similarly, methyl arylhydrazonochloroacetates (6) gave the corresponding methyl thiohydrazonate esters (7). Treatment of both 3 and 7 with hydrogen chloride in ethanol afforded the respective 1,4‐benzothiazine derivatives 4. Identical products (4) were obtained by refluxing 1 or 6 in ethanol in the presence of triethylamine. The structure of 4 was confirmed by their alternate synthesis starting with diethyl chloromalonate in ethanol in the presence of triethylamine which yielded the intermediate 1,4‐benzothiazine derivatives 8. The subsequent coupling of 8 with diazotized anilines in ethanol in the presence of potassium hydroxide afforded 4.

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