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

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Reaction Steps

2.33 g of (+)-(1R,2R)-3-[2-(dimethylamino)methyl-(cyclohex-1-yl)]-phenol are dissolved at room temperature in 15 ml of ethyl acetate and 1.16 g of maleic acid are dissolved in 30 ml of ethyl acetate, each in a glass flask. In another glass flask, 20 ml of ethyl acetate are heated to 45° C. and then both solutions are added simultaneously dropwise with stirring. Considerable turbidity forms spontaneously. Once addition is complete, the suspension is stirred for another 3 hours at 50° C. Then it is left to cool by itself to room temperature. The precipitate is filtered out and washed once with 10 ml of ethyl acetate and dried by having air drawn through it (5 minutes). 3.41 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.

Provenance & Evidence