We present a general, practical, and efficient approach to 5- and 6-membered organic carbonates by palladium-catalyzed direct oxidative carbonylation of 1,2- and 1,3-diols, respectively. Reactions were carried out at 100 °C in N,N-dimethylacetamide as the solvent under 20 atm (at 25 °C; 1 atm=101.3 kPa) of a 4:1 v/v CO/air mixture in the presence of 0.5–2 mol % of PdI2 and KI (KI/PdI2 molar ratio=10). Excess dehydrating agent, such as trimethyl orthoacetate, was necessary in several cases to obtain appreciable results. The method could also be applied to the synthesis of a high-value-added glycerol carbonate from glycerol, a readily available raw material. When applied to α-D-glucose, a double carbonylation process took place, with direct formation of α-D-glucofuranose 1,2:5,6-dicarbonate.