1-Alkoxycarbonyl-3-(2-thiazolyl) thioureas (A) were reacted with alkyl halides in presence of potassium carbonate to afford 1 (H)-alkoxycarbony1-2-alkyl-3-(2-thiazolyl)-isothioureas (D), 1-alkoxycarbony1-2-alkyl-3-(3-alkylthiazolin-2-ylidene) isothioureas (E) 2-alkylthio-thiazolo [3, 2-a]-s-triazine-4-ones (C). However, the rate of this reaction the yields of the products were dependent on the kinds of alkyl halide and thiazolyl thioureas (A). The cyclization ...