Synthesis of tetrahetrocyclic systems including pyrido[2′,3′:3,4]pyrazolo[1,5‐ a ]pyrimidine fused with pyrazole derivatives and isolated with 1,3,4‐oxa‐, thiadiazole, and 1,2,4‐tetrazole derivatives

A series of isolated and fused tetracyclic compounds, containing pyrido[2′,3′:3,4]pyrazolo[1,5‐ a ]pyrimidine linked with 1,3,4‐oxa‐, thiadiazole, 1,2,4‐tetrazole, and pyrazole derivatives were prepared by the reaction of 1,8,10‐trimethyl‐4‐oxo‐1,4‐dihydropyrido[2′,3′:3,4]pyrazolo[1,5‐ a ]pyrimidine‐3‐carboxylate and some common reagents to provide the product in satisfactory yields. J. Heterocyclic Chem., (2010).