Maleic Acid → (+)-(1R,2R)-3-[2-(dimethylamino)methyl-(cyclohex-1-yl)]-phenol maleate

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Reaction Conditions

Reaction Steps

8.92 g of maleic acid are dissolved at 55° C. in a glass flask in 120 ml of ethyl acetate. In another glass flask 17.96 g of (+)-(1R,2R)-3-[2-(dimethylamino)methyl-(cyclohex-1-yl)]-phenol are likewise dissolved at 55° C. at room temperature in 108 ml of ethyl acetate and slowly added dropwise within 30 minutes to the solution of maleic acid. After the addition of approx. half, a white, voluminous, finely crystalline solid precipitates out. The suspension is stirred for a further 3 hours at 55° C. once addition is complete. It is then left to cool by itself to room temperature and stirred again overnight. The precipitate is filtered out and washed once with 20 ml of ethyl acetate and dried by having air drawn through it (5 minutes). 26.26 g (97.7% of theoretical) of (+) -(1R,2R)-3-[2-(dimethylamino)methyl-(cyclohex-1-yl)]-phenol maleate are obtained as crystalline form A (according to the X-ray diffraction pattern). DSC analysis reveals two peaks at 166.03 and 177.03° C.

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