CuCl/Ionic Liquid Catalyzed Cascade Transformation of CO2 and Alkyne-1,2-Diols: Synthesis of Keto-Functionalized Cyclic Carbonates

The cyclization of propargyl alcohols with CO2 represents a highly significant method for the utilization of CO2. The resulting cyclic carbonates possesses high chemical value and hold great potential for applications in battery electrolytes, polymer precursors, and pharmaceutical intermediates. However, most existing reports on this cyclization have been limited to simple propargyl alcohol substrates that are substituted with inert alkyl, cycloalkyl, and phenyl groups. For functionalized propargyl alcohols, such as alkyne-1,2-diols, only a single report has been documented thus far. In this study, we have developed an innovative catalytic system comprising cost-effective copper salts and environmentally friendly ionic liquids (CuCl/1-ethyl-3-methylimidazolium acetate) for the cyclization of alkyne-1,2-diols with CO2. Compared to the previously reported AgF/bulky monophosphine ligand (BrettPhos) system, our system is free of traditional volatile solvents, phosphine ligands, and additives. Notably, this is the first reported Cu(I)-catalyzed system for this cyclization, offering significant advantages in terms of cost-effectiveness and reduced toxicity compared to silver salts. Moreover, the use of ionic liquids ensures considerable recyclability, further enhancing the sustainability and practicality of this approach.