3-Phenylisoquinolinone (II) was synthesized by addition of benzonitrile to the dilithium derivative of N-methyltoluamide (I). Conversion of (II) to the 1-chloroisoquinoline (III) was achieved by heating with POCl3. Then, displacement of the chlorine atom of (III) with N-methylpiperazine (IV) in refluxing DMF furnished the title compound.