Synthesis of pyrano[3,4-c]thieno[3,2-e][1,2,4]triazolo[4,3-a]pyridines, representatives of a new fused heterocyclic system

New effective synthesis of functionalized pyrano[3,4-c]thieno-[3,2-e][1,2,4]triazolo[4,3-a]pyridines comprises nucleophilic substitution in 8-morpholino-6-thioxopyrano[3,4-c]pyridine-5-carbonitrile with hydrazine hydrate followed by sequential heterocyclization with formic acid and chloroacetic acid derivatives.