Tailored Multiphase Catalysis Enables Efficient Catalyst Separation and Selectivity Adaption in the Ru-Catalyzed Synthesis of Cyclic Acetals from Carbon Dioxide

Herein a liquid-liquid multiphase reaction system is presented for the synthesis of cyclic acetals through the combined utilization of carbon dioxide, molecular hydrogen, and biomass-derived diols. The cationic ruthenium triphos catalyst and Lewis acid co-catalyst are immobilized in the diol substrate, while the product is recovered from the reaction phase via in situ extraction using n -decane as extraction solvent, allowing for efficient separation of catalyst and product. The multiphase approach additionally overcomes the limitation of the thermodynamic equilibrium of the acetal formation. Catalyst recycling was successfully demonstrated for ten consecutive runs, resulting in stable product formation when the byproduct water is removed after each run. The presented multiphase reaction system paves the way for the development of a continuous process for the synthesis of cyclic acetals that are increasingly interesting as sustainable fuels, solvents or monomers.