Collect. Czech. Chem. Commun. 1982, 47, 3268-3282

Synthesis and investigation of enamine-imine tautomerism of 2,6-disubstituted 4H-1,3-thiazin-4-ones

Ján Imrich and Pavol Kristian

Department of Organic Chemistry and Biochemistry, Šafárik University, 041 67 Košice


Substituted thioureas, obtained by reaction of 3-chloro-3-phenylpropenoyl isothiocyanate with primary aliphatic or aromatic amines, were cyclized to 2-N-alkyl(aryl)amino-6-phenyl-4H-1,3-thiazin-4-ones. The enamine-imine tautomerism was investigated by means of infrared and ultraviolet spectra and also by model substances prepared either by reacting the starting isothiocyanate with secondary amines, or by methylation of 2-N-alkyl(aryl)amino-6-phenyl-4H-1,3-thiazin-4-ones. The structure of the synthesized compounds was corroborated by 1H NMR and electron impact mass spectra. 2-N-Arylamino derivatives dissolved in chloroform exist prevalently an imino form whereas 2-N-alkylamino derivatives is an amino form. Reaction of 3-chloro-3-phenylpropenoyl isothiocyanate with aliphatic thiols gave 2-alkylthio-6-phenyl-4H-1,3-thiazin-4-ones and with sodium hydrosulfide (hydroselenide) 6-phenyl-2-thioxo-2,3-dihydro-4H-1,3-thiazin(selenazin)-4-ones.