Preparation method of pantoprazole sodium

The invention provides a preparation method of pantoprazole sodium. The method comprises the following steps of: 1) generating 2-chloromethyl-3,4-dimethoxypyridine hydrochloride (III) by taking 2-hydroxymethyl-3,4-dimethoxypyridine (II) as the start raw material in the presence of chloride; 2) condensing the obtained compound (III) with 5-difluoromethoxy-2-sulfydryl-1H-benzimidazole in alkaline conditions in the presence of inorganic base to generate 5-difluoromethoxy-2-[(3,4-dimethoxy-2-pyridyl)methyl]thioxo-1H-benzimidazole (IV); and 3) salifying the obtained compound (IV) with sodium hydroxide, and oxidizing with an oxidizing agent to generate 5-difluoromethoxy-2-[(3,4-dimethoxy-2-pyridyl)methyl]sulfinyl-1H-benzimidazole sodium, namely pantoprazole sodium (I). According to the invention, the operation is simple and efficient, the reaction conditions are mild, the safety is high, the control is easy, the yield is relatively high, and the method is suitable for industrial production.