Regioselective Synthesis of Imidazo[4,5-e][1,3]Thiazino[3,2-b][1,2,4]Triazines as New Heterocyclic System Derivatives

A series of new 4a,7a-diarylperhydroimidazo[4,5-e][1,2,4]triazine-3-thiones were synthesized from 4,5-diaryl-4,5-dihydroxyimidazolidin-2-ones and thiosemicarbazide in high yields, and their interaction with ethyl phenylpropiolate was studied. An effective method for the regioselective synthesis of imidazo[4,5-e][1,3]thiazino[3,2-b][1,2,4]triazines as new heterocycic system derivatives was proposed based on the reaction of aforementioned imidazotriazinethiones with ethyl phenylpropiolate in the presence of MeONa in methanol. The reaction is initiated by a Michael-type addition of the imidazotriazinethiones to the triple bond of ethyl phenylpropiolate followed by intramolecular cyclization.