A novel route to tetracyclic fused tetrazines and thiadiazines

Abstract magnified image The reaction between 3‐amino‐2,3‐dihydro‐7,9‐dimethyl‐2‐thioxo‐pyrido3′,2′:4,5thieno3,2‐ d ‐pyrimidin‐4(1 H )‐one 4 or its 2‐methylthio derivative 5 with hydrazonoyl halides 6 in dioxane in the presence of triethylamine under reflux has followed heterocyclization reaction to yield pyrido3″,2″:4′,5′‐thieno3′,2′:4,5pyrimido2,1‐ c 1,2,4,5tetrazin‐6(4 H )‐ones 9 . On the other hand, reaction of compound 4 with hydrazonoyl halides 6 in sodium ethoxide at room temperature led to formation of hydrazonothioate compounds 10 . The latter on treatment with glacial acetic acid produced tetracyclic compounds, namely 2‐arylhydrazonopyrido3″,2″:4′,5′thieno 3′,2′:4,5pyrimido2,1‐ b 1,3,4thiadiazinones 11 . An alternative method was carried out to prove the structure of product 11 . The mechanism of the reaction under study was proposed and the products were screened for their biological activity.