A mixture of 13.2 parts of 4-(phenylmethyl)-2-piperazinecarboxamide, 18.5 parts of 1,1'-(4-chlorobutylidene)bis[4-fluorobenzene], 14.8 parts of sodium carbonate, 0.1 parts of potassium iodide and 200 parts of 4-methyl-2-pentanone was stirred and refluxed for 72 hours using a water-separator. The reaction mixture was cooled to room temperature, filtered and the filtrate was evaporated. The oily residue was purified by column-chromatography over silica gel using a mixture of trichloromethane and methanol (97:3 by volume) as eluent. The pure fractions were collected and the eluent was evaporated. The residue was crystallized from 2,2'-oxybispropane. The product was filtered off and dried, yielding 17.7 parts (63.6%) of 1-[4,4-bis(4-fluorophenyl)butyl]-4-(phenylmethyl)-2-piperazinecarboxamide; mp. 79.2° C. (intermediate 46).
