Tetraarylphosphonium Salt-Catalyzed Carbon Dioxide Fixation at Atmospheric Pressure for the Synthesis of Cyclic Carbonates

Phosphonium salts exhibit great utility in organic synthesis. However, tetraarylphosphonium salts (TAPS) have found limited use as catalysts. We demonstrate the TAPS-catalyzed carbon dioxide fixation at atmospheric pressure for the coupling reaction with epoxides. Five-membered cyclic carbonates were obtained, including enantio-enriched carbonates. Mechanistic studies revealed the origin of the behavior of TAPS to be the in situ formation of an active species by TAPS addition to epoxides via halohydrin intermediates.