The Carboxylation of Epoxides Catalyzed by PEG₆₀₀₀-(NBu₃Br)₂ in scCO₂

Significance

The synthesis of carbonates from various epoxides and CO₂ promoted by PEG₆₀₀₀ resin-supported quaternary ammonium salt 1 was demonstrated. The carboxylation of propylene oxide 2a by using catalyst 1 was performed in supercritical CO₂ to give propylene carbonate 3b in 98% yield. Catalyst 1 was reused five times without any loss of its catalytic activity (see scheme for details). Five examples of the carboxylation of various epoxides were demonstrated (92-99% yields). The carboxylation of (R)-styrene oxide (R)-2b was carried out under same conditions to give (R)-1-phenyl-1,2-ethanediol carbonate (R)-3b in 99% ee with retention of stereochemistry.