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
摘要:
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.
The Knoevenagel reaction of 5-aryl-2,3-dihydrofuran-2,3-diones with ethyl cyanoacetate or malonodinitrile yields 2-substituted 6-aryl-3,4-dihydroxy-6-oxo-2,4-hexadienoic acid esters or amides which exhibit biological activity. The structure of the products is discussed, taking into account the structure of known 3,4-dihydroxy-6-oxo-2,4-hexadienoic acid esters and 1,6-diaryl-3,4-dihydroxy-2,4-hexadiene-1,6-diones.