Processes for producing a disubstituted oxalate and/or disubstituted carbonate are disclosed. The processes use a water removal agent to tune the amount of disubstituted oxalate and/or disubstituted carbonate in the product mixture. One process includes contacting a cesium salt with one or more alcohols in the presence of an effective amount of a water removal agent under a carbon dioxide (CO2) atmosphere and reaction conditions sufficient to produce a composition that includes a disubstituted oxalate. Methanol can be used to produce dimethyl oxalate.