preparation | 5g of 3 is dissolved in 50ml of mixed solvent of toluene and chloroform (volume ratio of toluene to chloroform 1:2), stirred and dissolved, then 3ml of anhydrous ethanol is added, and dry hydrogen chloride gas is introduced at 10 ℃, the weight gain of the system is 7.7g, and ventilation is stopped. Heat preservation, stirring and reaction for 24 hours, evaporation and drying under reduced pressure to obtain oil substance I; Dissolve the oil substance I with 30ml of absolute ethanol, then raise the temperature to 35 ℃, add 10g of ammonium carbonate, stir for 12 hours, add 20ml of saturated potassium carbonate solution, continue stirring for 0.5 hours, filter, scrub the filter cake with ethanol, and evaporate the filtrate to dry under reduced pressure to obtain oil substance II. Dissolve the oil substance II with 30ml of tetrahydrofuran aqueous solution (the volume ratio of tetrahydrofuran to water is 1:0.5), add 2.6g of p-toluenesulfonic acid, add 15ml of 25% ammonia water dropwise, and the precipitated solid is 1. Filter, after washing with water, vacuum drying at 60 ℃ to obtain 1, mesylate of dabigatran ethyl ester with a yield of 92.4%, and the purity is 97.7% by HPLC detection. |