Preparation method for key intermediate rabeprazole thioether

The invention discloses a preparation method for rabeprazole thioether 2-[[[4-(3- methoxypropoxy)-3-methylpyridin-2-yl] methyl] sulfo]-1H-benzimidazole. By using Mitsunobu reaction, the rabeprazole thioether is prepared from rabeprazole oxhydryl in one-step synthesis way without chlorination reaction. In the reaction process, the high-corrosive chloride agent, such as, thionyl chloride, is not used, so that the violent corrosion of the reaction to the device is obviously reduced, and meanwhile, the reaction yield is obviously increased due to the shortened reaction step. According to the invention, the process is simple, the reaction condition is mild, the corrosion to the device is small, the yield is higher (70%-80%) and the method is suitable for industrial production.