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

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Reaction Conditions

Reaction Steps

In a glass flask, 1.95 g of (+)-(1R,2R)-3-[2-(dimethylamino)methyl-(cyclohex-1-yl)]-phenol are dissolved at room temperature in 40 ml of ethyl acetate. Then a solution of 0.97 g of maleic acid in 25 ml of ethyl acetate is added dropwise at room temperature. After the addition of approx. half the solution, firstly turbidity forms and then a crystalline precipitate. The suspension is stirred at 70° C. for an hour in a rotary evaporator and then cooled to room temperature. The suspension is then cooled to 4° C. in the refrigerator and the precipitate filtered out. The solid residue is washed once with 4 ml of ethyl acetate and dried by having air drawn through it (5 minutes). 2.815 g (96.4% of theoretical) of (+)-(1R,2R)-3-[2-(dimethylamino)methyl-(cyclohex-1-yl)]-phenol maleate are obtained as crystalline form B (according to the X-ray diffraction pattern) with a melting point of 177-179° C. DSC analysis reveals a peak at 177.7° C.

Provenance & Evidence