A stirred solution of 6.1 g of 2,3-dihydro-1'-benzyl-6-chlorospiro[benzofuran-2,4'-piperidine], free base of Example 5, and 2.5 g of ethylchloroformate in 150 ml of benzene is refluxed for 18 hours. Thereafter, the solution is successively permitted to cool to ambient temperature, washed with water, washed with a saturated sodium bicarbonate solution, washed with a saturated sodium chloride solution, dried and concentrated to dryness, leaving 2,3-dihydro-6-chloro-1'-ethoxycarbonylspiro[benzofuran-2,4'-piperidine] as a dark oil. The oil is taken up in a mixture of 50 ml of a 50% potassium hydroxide solution and 100 ml of ethyl alcohol and this mixture is refluxed for 18 hours and then permitted to cool to room temperature before removal of the ethyl alcohol under reduced pressure. The remaining aqueous suspension is extracted with ether and the combined ether extracts are washed with 3 N hydrochloric acid, the acidic wash is basified with 6 N sodium hydroxide and the basified solution is extracted with ether. The combined ether extracts are dried before being concentrated to dryness, leaving on off-white solid. The solid is dissolved in ether where it is converted to its hydrogen chloride salt which is recrystallized twice from ethyl alcohol providing the product, 2,3-dihydro-6-chlorospiro[benzofuran-2,4'-piperidine]hydrochloride, mp 281°-288° C.
