Br[C:2]12[CH2:11][C:6]3([CH3:12])[CH2:7][CH:8]([CH2:10][C:4]([CH3:13])([CH2:5]3)[CH2:3]1)[CH2:9]2.[NH2:14]C(N)=O.Cl>C(O)=O>[NH2:14][C:2]12[CH2:11][C:6]3([CH3:12])[CH2:7][CH:8]([CH2:10][C:4]([CH3:13])([CH2:5]3)[CH2:3]1)[CH2:9]2To 100 g of 1-bromo-3,5-dimethyl adamantane and 86 g of urea, adding 72 ml of 94 wt % formic acid, heating to 120° C. and holding for 2 hours. Cooling to the room temperature and adding 385 ml of 10% hydrochloric acid to hydrolyze at 100° C. for about 1 hour. Adjusting with 30% sodium hydroxide solution to a pH of 12, extracting with butyl acetate twice, combining the organic layers and washing with water. Concentrating under reduced pressure to yield a limpid yellow solution as 1-amino-3,5-dimethyl adamantane crude. To the crude, adding 150 ml of ethanol and concentrated hydrochloric acid, heating to dissolve and crystallizing to yield white solid. Drying the solid and re-crystallizing with water to yield 60.4 g of pure Memantine Hydrochloride. The yield is 68.1% (GC 99.1%).
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