Polyfunctional fused heterocyclic compounds via indene‐1,3‐diones

Abstract 2‐Dimethylaminomethylene‐ and 2‐ethoxymethylene‐1,3‐indendione 1a,b react with 6‐amino‐2‐thioxopyrimidin‐4(3H)‐one 2 in boiling acetic acid to give 2‐thioxo‐1,3‐dihydroindeno[3,2‐d]pyrimidino[4,5‐b]pyridine‐4,9‐dione (4). The latter compound reacts with hydrazonoyl chlorides 5a–c to afford products 12a–c. Formamidine 15 reacts with indene‐1,3‐dione in boiling ethanol to give acyclic compound 16, which cyclizes to 12a in boiling glacial acetic acid. Also, enaminone 1a reacts with heterocyclic amines 17a–e in boiling ethanol, affording the corresponding substitution products 18a–c, respectively. The latter products 18a–c cyclize in glacial acetic acid to give 19a–c, respectively. The structures of the newly synthesized compounds are established on the basis of chemical and spectroscopic evidence.