GENERAL STEPS: L-thioproline (0.11 mol) and potassium chloride solution (100 mL) were added to the reaction vessel. The stirring speed was controlled at 150 rpm. the reaction mixture was heated to 85°C. A solution of 85% 2-thienylacetonitrile (50 mL) was slowly added dropwise with a controlled drip time of 40 min. The stirring rate was maintained and the reaction was continued for 120 minutes. Upon completion of the reaction, a reduced pressure distillation (2.3 kPa) was performed to separate the solid product. To the resulting solid, 90% p-xylene (80 mL) was added and heated to completely dissolve the solid. Decolorization was performed by adding decolorizing molecular sieves, maintaining the solution temperature at 15°C for 35 min. The solid impurities were removed by filtration and dehydrated using phosphorus pentoxide to give the final white N-acetyl-L-thioproline (1) (17.13 g, 89% yield).
