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.P(=O)(O)(O)O.[OH-].[K+]>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 80 ml of 80 wt % formic acid, heating to 80° C. and holding for 3 hours. Cooling to the room temperature and adding 75 ml of 85% phosphoric acid to hydrolyze at 80° C. for 1 hour. Adjusting with 10% potassium hydroxide aqueous solution to a pH of 12. Extracting with toluene 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 a white solid. Drying the solid and re-crystallizing with ethanol to yield 61.0 g of pure Memantine Hydrochloride. The yield is 68.8% (GC 99.5%).
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