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Cyclization of thiohydrazonate esters and azo‐hydrazone tautomerism of 2‐arylhydrazono‐3‐oxo‐1,4‐benzothiazines
Author(s) -
Shawali Ahmad S.,
Elsheikh Said,
Párkányi Cyril
Publication year - 2003
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570400202
Subject(s) - chemistry , triethylamine , benzothiazine , ethanol , potassium hydroxide , tautomer , hydrazone , organic chemistry , medicinal chemistry
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 .