Hydrochloric Acid → 4-(Piperidin-4-yl)Morpholine hydrochloride

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A stirred mixture of Pd(OH)2 (20% on carbon (<50% wet), 390 mg, 25 wt %), methanol (50 mL), and ≦1.7 M HCl (3 eq, ˜10.6 mL—including water added later when ppt was seen) under nitrogen was exchanged to 1 atm. hydrogen atmosphere by flushing (˜20 sec) using a balloon of nitrogen into the vessel and out through an oil bubbler. After 20 min. the reaction mixture under hydrogen was heated to 50° C. and 4-(morpholin-4-yl)-1-benzylpiperidine (1.56 g, 6.0 mmol) in methanol (8 mL) was added dropwise over 30 min. After 10 h, tlc indicated all starting amine was consumed to a more polar spot (ninhydrin active). The reaction mixture was then filtered through Celite and evaporated to yield the 4-(morpholin-4-yl)piperidine dihydrochloride as an off-white solid. This material was subjected to free-basing using excess basic resin (>16 g, Bio-Rad Laboratories, AG 1-X8, 20-50 mesh, hydroxide form, methanol washed two times) and a methanol mixture of the amine hydrochloride. After swirling with the resin for 30 min., the methanol solution was decanted and evaporated to yield 932 mg of 4-(morpholin-4-yl)piperidine free base as a waxy crystalline solid.

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