We report an efficient process for the synthesis of diethyl malonate (DEM) and other malonates through the palladium-catalyzed carbonylation of chloroacetates. Excellent selectivity (96 %) and yield (94 %) were obtained without the formation of Pd black. For the first time, a weakly alkaline buffer was used to control the selectivity for DEM in the reaction and we discuss the relationship between the buffer medium and selectivity in the reaction. The combination of anisole as the solvent and a Na2HPO4/NaH2PO4 buffer was beneficial for completely restraining the phase-transfer-catalyzed substitution of DEM with ethyl chloroacetate, as well as accommodating the proposed [(PPh3)2PdI]−[Bu4N]+ intermediate, by providing a suitable environment for its stable existence. We achieved the highest efficiency in the catalytic cycle by fine-tuning the balance between the rates of oxidative addition and reductive elimination; moreover, we synthesized a recoverable heterogeneous polymer-bound Pd catalyst in 85 % yield that could be reused without an appreciable loss in activity over four cycles.