In a similar manner to Example 7, a mixture of 4-aminomethylpiperidine (2.9 g), 4'-chloroacetophenone (3.94 g), toluene (100 ml) and a catalytic amount of p-toluenesulphonic acid was boiled under reflux for five hours with removal of the water formed using a Dean and Stark apparatus. The mixture was cooled and treated with 2-bromoethyl 3-chlorophenyl ether (6.0 g) followed by triethylamine (3.54 ml). The mixture was boiled under reflux for 6 hours and then evaporated to dryness. 6M Hydrochloric acid (50 ml) was added and the mixture heated on a steam bath for 16 hours to give 4-aminomethyl-1-[2-(3-chlorophenoxy)ethyl]piperidine, as an oil. The oil, obtained on work up, was treated with 98% formic acid (5.0 ml) and formaldehyde (5.0 ml, 38% aqueous solution). The mixture was heated on a steam bath for 4 hours. After extractive work up as described in Example 7, the oil obtained was distilled at 120° C. at 0.13 mbar. The distillate was treated with ethereal hydrogen chloride to give 1-[2-(3-chlorophenoxy)ethyl]-4-(dimethylaminomethyl)piperidine dihydrochloride, m.p. 258°-260° C., after recrystallisation from absolute ethanol.
