Azines and azoles: CXXVII. 5-phenyl-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones: Synthesis and structure

Abstract

Reactions of 1-acylthiosemicarbazides with methyl 3-phenylprop-2-ynoate provide a new one-step procedure for the synthesis of 2-substituted 5-phenyl-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones. The product structure was determined on the basis of scalar spin-spin coupling constants 2 J(1H-15N) and 3 J(1H-15N) in the 1H and 15N NMR spectra and was proved by X-ray analysis. Methyl 3-phenylprop-2-ynoate reacted with 1-acetylthiosemicarbazide in ethanol in the presence of H2SO4 to give 3-methyl-7-phenyl[1,2,4]triazolo[3,4-b]-[1,3]thiazin-5-one as the only product.