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

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Reaction Steps

6.22 g (53.5 mmol) of maleic acid are dissolved in a glass flask in 130 ml of ethyl acetate and then added dropwise with stirring to a solution, adjusted to a temperature of 50° C., of 12.48 g (53.5 mmol) of (+)-(1R,2R)-3-[2-(dimethylamino)methyl-(cyclohex-1-yl)]-phenol in 40 ml of ethyl acetate. After the addition of 20 to 25 ml, a white precipitate forms. After addition of the entire solution, the finely crystalline white solid is filtered out of the warm solution and washed with a little cold ethyl acetate. The residue is dried by having air drawn through it. 18.38 g (98.3% 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) with a melting point of 177-179° C. DSC analysis reveals two peaks at 165.5 and 177.2° C.

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