Abstract Addition reactions of 2-chloronicotinoyl isothiocyanate with primary and secondary amines and subsequent cyclization of intermediate thioureas represent new synthesis of pyrido [3, 2-e] thiouracil and pyrido [3, 2-e]-thiazine derivatives. 2-Amino-4-oxopyrido [3, 2-e]- 1, 3-thiazines are formed upon heating the reaction components in ethanol, whereas 1-alkyl (aryl) pyrido [3, 2-e]-2-thiouracils are products of alkali-catalyzed reaction. In reaction with ...