Step a): Sodium metal (23 g, 1 mole) was slowly added to anhydrous ethanol (500 mL) under stirring conditions until completely dissolved. Subsequently, diethyl malonate (160 g, 1 mole) was added dropwise over 30 min. After cooling the reaction mixture to 15°C, ethyl chloroacetate (117 g, 0.095 mol) was added dropwise over the same time. After the dropwise addition, the reaction mixture was refluxed for 6 hours. After completion of the reaction, the mixture was poured into 2 liters of water and the organic phase was extracted with dichloromethane (500 mL each time, three times). The organic extracts were combined, dried with anhydrous sodium sulfate, filtered and the solvent was evaporated to give an oily crude product. Finally, purification by vacuum distillation afforded triethyl ethyl-1,1,2-tricarboxylate (220 g, 89% yield).
