Difference of Chemical Behavior of Carbon Dioxide and Carbon Disulfide on the Reaction with DBU Forming Dialkyl Carbonates and Trithiocarbonatest

Abstract

DBU absorbs CO₂ effectively at room temperature in the presence of water or alcohol. Subsequently, DBU carbonate salts produced react with alkylating reagents to form the corresponding dialkyl carbonates in fairly good yields under mild reaction conditions.
On the other hand, the mixture of water, CS₂, and DBU (molar ra tios 2: 3: 4) gives 2moles of DBU trithiocarbonate salt, with evolution of 1 mole of CO₂, by heating at 80°C and the reaction of the resulting salt with alkylating reagents affords dialkyl trithiocarbonates in good yields.
The main difference between the above two cases could be ascribed to the stronger nucleophilicity of the preformed anion of sulfur than that of oxygen.