Preparation method of ofloxacin

The invention provides a preparation method of ofloxacin. The preparation method comprises the following steps of: reacting (N,N)-dimethylamino ethyl acrylate with aminopropanols in methylbenzene; directly adding lewis base serving as a catalyst and trimethylchlorosilane to protect hydroxyl and amido; after reaction is completely finished, dropwise adding (2,3,4,5)-tetrafluorobenzoyl chloride; preserving heat; performing acid washing; removing protecting groups; concentrating an organic layer to obtain an oil layer; adding a proper amount of dimethyl formamide (DMF); diluting and dropwise adding backflow DMF having anhydrous potassium fluoride; recovering DMF and adding water to centrifuge; adding acid water into a solid to hydrolyze to obtain difluorocarboxylic acid; and completely reacting difluorocarboxylic acid and N-methyl piperazine in dimethylsulfoxide (DMSO) by using triethylamine as an acid-binding agent at 90-100 DEG C to obtain ofloxacin. According to the process, hydroxyl and amido are protected by using trimethylchlorosilane, so that the utilization degree of (2,3,4,5)-tetrafluorobenzoyl chloride is effectively increased, and the generation of impurities is reduced to ensure that the reaction yield of intermediate difluorocarboxylic acid is increased by 10 percent.