Tetracarbonyl systems:: VII.: Reactions of 1,3,4,6-tetracarbonyl compounds with o-aminothiophenol in the synthesis of regioisomeric 3(2)-aroylmethylene-1,4-benzothiazin-2(3)ones

In reaction of 1,6-diaryl-3,4-dihydroxy-2,4-hexadiene-1,6-diones with o-aminothiophenol (3Z)-3-aroylmethylene-3,4-dihydro-2H-1,4-benzothiazin-2-ones were obtained in a preparative yield. In solution of the latter compounds an enamine-imine tautomerism was observed. In reaction of ethyl esters or an-fides of 2-substituted 6-aryl-3,4-dihydroxy-6-oxo-2,4-hexadienoic acids with the o-aminothiophenol regioisomeric 2-aroylmethylene-2H-1,4-benzothiazin-3(4H)-ones were formed.