Sodium triacetoxyborohydride → 1-(2-{4-[(2,3-Dihydro[1,4]dioxino[2,3-c]pyridin-7-ylmethyl)amino]piperidin-1-yl}ethyl)-7-methoxyquinolin-2(1H)-one

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A solution of 1-[2-(4-aminopiperidin-1-yl)ethyl]-7-methoxyquinolin-2(1H)-one (Intermediate 1, crude, 60 mg, 0.20 mmol) and 2,3-dihydro[1,4]dioxino[2,3-c]pyridine-7-carbaldehyde (WO 2004/058144) (33 mg, 0.20 mmol) in dry chloroform/methanol (5 mL, 1:1) was heated over 3 Å molecular sieves at 70° C. for 3 hours. The reaction mixture was cooled to 0° C., and sodium triacetoxy borohydride (127 mg, 0.6 mmol) was added. The resulting reaction mixture was stirred at room temperature for 30 minutes and then was filtered through a 0.45 μm membrane and concentrated to dryness under reduced pressure. The residue was taken up in dichloromethane (50 mL) and saturated aqueous sodium hydrogen carbonate solution (5 mL). The pH of the aqueous phase was adjusted to a pH of 10 with 1M aqueous sodium hydroxide solution. The aqueous phase was back extracted twice with dichloromethane (2×20 mL) and the combined organic phases were dried over sodium sulfate and concentrated under reduced pressure. Chromatography on silica gel with dichloromethane/methanol (8:1 to 4:1) gave the free base of the title compound as a colorless oil. The free base was taken up in dichloromethane (2 mL), ethanol (7 mL) was added, followed by addition of 1M HCl in ether (0.3 mL). The colorless precipitate was collected by filtration and gave 50 mg (48%) of the bis-hydrochloride salt of the product, mp 243° C.

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