General procedure for the synthesis of dimethyl succinosuccinate from methyl 4-chloroacetoacetate: Under stirring conditions, methyl 4-chloroacetoacetate (10 g, 0.06 mol) was slowly added to a mixed solution containing potassium carbonate (17 g, 0.12 mol) and DMSO (50 mL). The reaction mixture was first stirred at room temperature for 3 hours, then warmed to 60 °C and continued stirring for 10 hours. After completion of the reaction, the mixture was cooled to room temperature, diluted with an appropriate amount of water and subsequently filtered. The filtrate was extracted with ether and the extract was dried over anhydrous magnesium sulfate and the solvent was removed by distillation to give a yellow crystal product (14 g, 52% yield) with a melting point of 152-153 °C. The structure of the product was confirmed by 1H NMR and 13C NMR spectra: 1H NMR (δ, ppm): 3.20 (s, 2H, CH2), 3.80 (s, 3H, CH3O), 3.90 (s, 3H, CH3O), 7.45 (s, 1H, CH=), 9.80 (s, 1H, OH), 12.10 (s, 1H, OH). 13C NMR (CDCl3, δ, ppm): 28.42, 52.33, 53.07, 95.94, 118.00, 120.05, 151.32, 168.00, 171.36. Elemental analytical results are in accordance with the theoretical values: measured (%): C 52.78, H 5.17; theoretical (C10H12O6, %): C 52.63, H 5.26.
