Abstract Functionalized 2, 3-dihydro-1, 3-thiazin-4 (1H)-one derivatives have been synthesized by cyclocondensation of 3-alkyl (aryl) amino-2-cyano-3-mercaptoacrylamides with aldehydes and ketones under acidic catalysis. 6-Alkyl (aryl) amino-5-cyano-2, 3-dihy- dro-1, 3-thiazin-4 (1H)-ones, when treated with a dilute solution of potassium hydroxide, are converted into the potassium salts of isomeric compounds, 1-alkyl-(aryl)-5-cyano-6- ...