A novel route to tetracyclic fused tetrazines and thiadiazines

Abstract

Abstract magnified image The reaction between 3‐amino‐2,3‐dihydro‐7,9‐dimethyl‐2‐thioxo‐pyrido[3′,2′:4,5]thieno[3,2‐ 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 pyrido[3″,2″:4′,5′]‐thieno[3′,2′:4,5]pyrimido[2,1‐ c ][1,2,4,5]tetrazin‐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‐arylhydrazonopyrido[3″,2″:4′,5′]thieno [3′,2′:4,5]pyrimido[2,1‐ b ][1,3,4]thiadiazinones 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.