NOVELTY - 3-Amino-adamantanol, potassium iodide, organic base and 480 g acetonitrile are added to reactor and heated at 75-80 degrees C, and 530 g acetonitrile and 100 g 0.5793 mol (S)-1-(2-chloroacetyl chloride)pyrrolidine-2-carbonitrile are added to mixture, dissolved and reacted. After completion of reaction, the temperature is decreased to 20-30 degrees C and the mixture is filtered. The solvent in filtrate is removed, to obtain pale yellow solid. Pale yellow solid is recrystallized with 210 g organic solvent (c), to obtain vildagliptin.    USE - Synthesis of vildagliptin (claimed).    ADVANTAGE - The method enables synthesis of vildagliptin with high yield by simple, efficient and environmentally-friendly method.    DETAILED DESCRIPTION - 100 g 0.8772 mol L-Prolinamide, triethylamine and 640 g mixed organic solvent are mixed to form a suspension. The suspension is stirred and cooled to -35 degrees C to -25 degrees C. Acetyl chloride is dripped to suspension and reacted at -35 degrees C for -15 degrees C for 1 hour, to obtain (S)-1-(2-chloroacetylchloride)pyrrolidine-2-carboxamide suspension. The molar ratio of triethylamine and L-prolinamide is 1:1.1-1:1.3. The molar ratio of acetyl chloride and L-prolinamide is 1:1.2-1:1.4. (S)-1-(2-chloroacetylchloride)pyrrolidine-2-carboxamide suspension is heated at -5 degrees C to 20 degrees C, and N,N-dimethylformamide and phosphorus oxychloride are dripped to mixture and reacted at -5 degrees C to 20 degrees C for 2 hours. 700 g Water is added to mixture, quenched and separated, to obtain aqueous layer. The aqueous layer is twice extracted with 350 g organic solvent (a). The combined organic phase is washed, and solvent is removed, to obtain oil. Oil is added to 200 g organic solvent (b) and recrystallized, to obtain (S)-1-(2-chloroacetyl chloride)pyrrolidine-2-carbonitrile. The molar ratio of N,N-dimethylformamide and L-prolinamide is 1:2-1:2.5. The molar ratio of phosphorus oxychloride and L-prolinamide is 1:1.1-1:1.3. 3-Amino-adamantanol, potassium iodide, organic base and 480 g acetonitrile are added to reactor and heated at 75-80 degrees C, and 530 g acetonitrile and 100 g 0.5793 mol (S)-1-(2-chloroacetyl chloride)pyrrolidine-2-carbonitrile are added, dissolved and reacted at 75-80 degrees C for 1 hour. After completion of reaction, the temperature is decreased to 20-30 degrees C and the mixture is filtered to remove hydrochloride salt of organic base. The solvent in filtrate is removed, to obtain pale yellow solid. Pale yellow solid is recrystallized with 210 g organic solvent (c), to obtain vildagliptin. The molar ratio of 3-amino-adamantanol and (S)-1-(2-chloroacetyl chloride)pyrrolidine-2-carbonitrile is 1:1.1-1:1.3. The molar ratio of potassium iodide and (S)-1-(2-chloroacetyl chloride)pyrrolidine-2-carbonitrile is 1:0.05. The molar ratio of organic base and (S)-1-(2-chloroacetyl chloride)pyrrolidine-2-carbonitrile is 1:1.4-1:1.8.