The oxidation of 3-chloro-1-phenylisoquinoline-4-carbaldehyde (I) with KMnO4 in acetone - aqueous phosphate buffer gives 3-chloro-1-phenylisoquinoline-4-carboxylic acid (II), which is then condensed with piperazine (III) by heating at 150 C to yield the free base (IV). The HCl salt is formed with ethanolic HCl.