A method of benzenesulfonic acid with clopidogrel form prepared III

The present invention discloses a process for preparing clopidogrel Form Ⅲ acid, comprising: (a) the (S) - (+) - clopidogrel base is dissolved in ketone solvent; (b) the resulting mixture was cooling, addition of an aqueous acid, the reaction was stirred; (c) a ketone solvent was distilled off to partially saturated, seeded, stirred crystallization, or a ketone solvent was distilled off, adding a hydrocarbon solvent to crystallize with stirring; (d) filtering, washed, and dried to give benzenesulfonic acid with clopidogrel form ⅲ. The present invention uses readily available market aqueous acid to a salt, low cost, simple operation and high purity of clopidogrel crystal Form III obtained, suitable for pharmaceutical use.