Method for preparing substituted (S)-pyrrolidine-2-formonitrile and vildagliptin

The invention provides a method for preparing (S)-1-(2-halogenated acetyl)pyrrolidine-2-formonitrile as shown in the formula (I). Optionally in the presence of a diluent, (S)-1-(2-halogenated acetyl)pyrrolidine-2-formamide and a dehydrating agent propanephosphonic acid cyclic anhydride (T3P) react with each other. The invention also provides a method for preparing vildagliptin by using S-prolinamide involving the above reaction. The method for preparing the compound as shown in the formula (I) has the following advantages: use of expensive trifluoroacetic anhydride is not required, yield is increased, and cost is reduced; use of cyanuric chloride prepared from highly toxic raw materials is not required, and the reaction is more environmentally friendly; and an improved method for preparing vildagliptin is then obtained. In the formula (I) and formula (II), X1 is halogen. 本发明提供种制备下式(I)的(S)-1-(2-卤乙酰基)吡咯烷-2-甲腈的方法，包括任选在稀释剂存在下，用式(IV)的(S)-1-(2-卤乙酰基)吡咯烷-2-甲酰胺与脱水剂丙基磷酸酐(TP)反应；还提供种包括前述反应的、以S-脯氨酰胺为原料制备维格列汀的方法。使用所述方法制备化合