Phosphonium Salt as a Catalyst of Carbon Dioxide Fixation Reaction

(2-Carboxyethyl)triphenylphosphonium bromide (1) is most commonly applied to Wittig reactions on carbonyl substrates. An additional and green application of the phosphonium salt is in the CO₂ fixation of epoxides to furnish cyclic carbonates. In the presence of catalytic amounts of 1 and heating under CO₂ atmosphere, epoxides react with CO₂ to afford cyclic carbonates in high yields. This reaction proceeds under metal- and solvent-free conditions and requires only 0.5 mol% of 1 as a catalyst. In this way, 1 is employed as a green catalyst for CO₂ fixation reactions.