Synthesis of pyrimidinones by action of benzamidine on a benzocycloheptenic β‐keto ester

The synthesis of a polycyclic heterocyclic ring system compound, ethyl 7‐hydroxy‐4‐oxo‐2‐phenyl‐4,5‐dihydro‐3H‐benzo[6,7]cyclohepta[1,2‐d]pyrimidine‐6‐carboxylate was carried out by condensation of benzamidine on diethyl 5,9‐dihydroxy‐7H‐benzo[a]cycloheptene‐6,8‐dicarboxylate, after opening and then closure of the seven membered ring.