The condensation of cyclooctanone (I) with 4-fluorobenzoylacetonitrile (II) by heating with polyphosphoric acid at 120 C gives 4-fluorophenyl-5,6,7,8,9,10-hexahydrocycloocta[b]pyridin-2(1H)-one (III), which is converted to the corresponding 2-chloro derivative (IV) by treatment with refluxing phosphoryl chloride. The reaction of (IV) with 1-ethylpiperazine (V) at 170 C affords AD-5423.