Cycloaddition of carbon dioxide to propylene oxide catalyzed by ionic liquids

In room temperature ionic liquids based on 1-n-butyl-3-methylimidazolium and n-butylpyridinium salts, cycloaddition of carbon dioxide to propylene oxide without any additional organic solvents has been investigated. It was found that 1-n-butyl-3-methylimidazolium tetrafluoroborate was the most active catalyst with almost 100% selectivity, and a suitable CO2–propylene oxide molar ratio was needed for high conversion. The ionic liquid used as catalyst for the reaction was recyclable.