To 1 part of a solution of 2 parts of thiophene in 40 parts of ethanol are added 4.7 parts of 1-(4-fluoro-2-methylphenyl)-4-oxocyclohexanecarbonitrile, 5.4 parts of ethyl 4-phenyl-4-piperidinecarboxylate hydrochloride, 2 parts of sodium acetate and 120 parts of ethanol. The whole is hydrogenated at normal pressure and at room temperature with 2 parts of palladium-on-charocal catalyst 10%. After the calculated amount of hydrogen is taken up, the catalyst is filtered off over Hyflo and the filtrate is evaporated. From the residue, the free base is liberated in the conventional manner with ammonium hydroxide and the product is extracted with dichloromethane. The extract is dried, filtered and evaporated. The residue is purified by column-chromatography over silica gel using a mixture of trichloromethane and ethanol (98.5:1.5 by volume) as eluent. The pure fractions are collected and the eluent is evaporated. The residue is crystallized from ethanol, yielding 3 parts (33.4%) of ethyl 1-[4-cyano-4-(4-fluoro-2-methylphenyl)cyclohexyl]-4 -phenyl-4-piperidinecarboxylate; mp. 135.2° C.
