An efficient synthesis of novel pyridothieno-fused thiazolo[3,2-a]pyrimidinones via Pictet–Spengler reaction

Abstract An efficient method for the synthesis of novel pyrido[3″,2″:4′,5′]thieno[3′,2′:2,3]pyrido [4,5: d ][1,3]thiazolo[3,2- a ]pyrimidine-4-one derivatives ( 5 ) has been developed using a Pictet–Spengler reaction between 2-(3-aminothieno[2,3- b ]pyridin-2-yl)thiazolo[3,2- a ] pyrimidin-5-one ( 3 ), which could be obtained from the condensation of 7-(chloromethyl)-5 H -thiazolo[3,2- a ]pyrimidin-5-one ( 1 ) with 3-cyanopyridine-2-thione ( 2 ) via Thorpe–Ziegler isomerization, and aromatic aldehydes under NH 2 SO 3 H as catalysis in good yields.