Metal-Free Synthesis of Cyclic and Acyclic Carbonates from CO2 and Alcohols

Diverse cyclic and acyclic carbonates such as ethylene carbonate, propylene carbonate, glycerol carbonate, and dimethyl carbonate were synthesized in moderate to good yields by the direct coupling of the corresponding alcohols with carbon dioxide in the absence of metal catalysts and inorganic bases. The direct carbonation mechanism of alcohols in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, 1-butyl-3-methylimidazolium hexafluorophosphate, and dibromomethane was probed by O-18-labeling experiments and chiral alcohol experiments.