Water → 4-(Azetidin-1-yl)piperidine dihydrochloride

After adding 10% palladium-carbon (600 mg) to a solution of the crude 4-(azetidin-1-yl)-1-benzylpiperidine dihydrochloride (6.55 g) in 2-propanol (50 ml)-water (50 ml), the mixture was stirred for 23 hours at room temperature under a hydrogen atmosphere. The catalyst was filtered and washed with 2-propanol, and then the filtrate was concentrated. Ethanol (10 ml)-hexane (50 ml) was added to the residue to produce suspended precipitate. It was then filtered and washed with 10 ml of ethanol. The filtered precipitate was subjected to aeration drying to provide the title compound (4.26 g) as white powder.