Organocatalyst system for disubstituted carbonates from cycloaddition between CO2 and internal epoxides

Abstract

An organocatalyst system, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and nBu4NCl, was developed for the conversion of CO2 and internal epoxides to the corresponding disubstituted cyclic carbonates under rather mild conditions (1–4 atm of CO2 and 100–120 °C). Catalyst screening revealed that small Cl− opens epoxide rings more effectively than larger Br− and I− do when used as the counter anion of nBu4N+, suggesting that the steric hindrance of the internal epoxides is a factor. A practical and economical alternative system, DBU and nBuCl, is also presented.