Sodium borohydride → 1-[2-(3,4-Methylenedioxyphenyl)-2-hydroxyethyl]-4-(2-oxo-3,4-dihydro-2H-1,3-benzoxazin-3-yl)-piperidine

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Reaction Steps

In this example, 3.0 g of 1-(3,4-methylenedioxybenzoylmethyl)-4-(2-oxo-3,4-dihydro-2H-1,3-benzoxazin-3-yl)piperidine obtained in Example 2 is mixed with 150 ml of methanol. While the mixture is stirred at 0° to 10° C., 0.8 g of sodium borohydride is added thereto over a period of 3 hours. Then, the mixture is stirred overnight at room temperature. The mixture is further mixed with 0.4 g of sodium borohydride and stirred at room temperature for 3 hours. The white crystals deposited are separated by filtration, washed with methanol and water and dried to obtain 2.36 g of a crude product. In the meantime, the filtrate is concentrated under reduced pressure. The residue is mixed with water. The crystals deposited are separated by filtration, washed with water and dried to obtain 0.37 g of a crude product. The two crude products are combined and recrystallized from ethanol to obtain 2.49 g of the desired product.

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