Synthesis method of sitagliptin phosphate intermediate

The invention relates to a synthesis method of a sitagliptin phosphate intermediate, and belongs to the technical field of organic synthesis. The method comprises the following technological steps of synthesizing a reaction liquid of 5-hydroxyl-[(2,4,5-trifluoro-phenyl)-ethylidene]-dimethyl-[1,3] dioxo-4,6-diketone from 2,4,5-trifluoro-phenylacetic acid, meldrum's acid, N,N-diisopropylethylamine, DMAP and acetylchloride; adding 3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4] triazol [4,3-alpha] pyrazine hydrochloride and trifluoroacetic acid to obtain the product. According to the method, the reaction raw materials are easily available; the reaction process is simple in operation; the requirements on reaction equipment are low; the reaction conditions are relatively mild; the yield and content are high, the quantity of waste water and solid wastes is relatively low, the cost is saved, and the method is suitable for industrial production.