Organocatalytic coupling of carbon dioxide with epoxides: the unexpected booster effect of fluoroalcohols

Valorising CO2 as a C1 feedstock for producing added value building blocks is seducing as it is a free and in exhaustive waste resulting from human activity. Carbon dioxide is a thermodynamically and kinetically stable molecule that can be converted into cyclic carbonates by coupling with epoxides. Cyclic carbonates are valuable products that find applications as solvents, electrolytes or as monomers for polyurethanes synthesis. Although the CO2/epoxide coupling reaction has been extensively studied, the development of organocatalysts that are highly efficient under mild experimental conditions still remains a challenge. Onium salts are the most common catalysts that show reasonable catalytic activity at high pressure (> 100 bars) and high temperature (> 100°C) only. Fortunately, the efficiency of these organocatalysts can be improved by addition of appropriate hydrogen bond donors activators (HBD). In this talk, we will report the development of a new highly efficient catalytic platform consisting in an onium halide salt combined with HBD activators for the fast and solvent-free synthesis of cyclic carbonates by coupling CO2 with epoxides. The cocatalytic effect of series of HBDs will be demonstrated by detailed online kinetics studies under pressure using Raman or IR spectroscopy. We will show that our new organocatalytic platform facilitates the fast conversion of epoxy groups into cyclic carbonates under mild experimental conditions, and can be easily implemented to the modification of epoxidized vegetable oils. The synergistic effects between HBDs and onium salt will be highlighted by a detailed mechanistic study of the reaction through DFT calculations.