Cascade Transformation of Carbon Dioxide and Alkyne-1,n-diols into Densely Substituted Cyclic Carbonates

A silver-catalyzed cascade conversion of modular alkyne-1,n-diols and carbon dioxide has been developed allowing for the selective formation of keto-functionalized cyclic carbonates. The protocol is characterized by its operational simplicity, excellent scope of carbonate-based heterocycles, and mild reaction conditions. In situ IR studies, control experiments, and detailed computational analysis of these manifolds reveal the intermediacy of an α-alkylidene carbonate that is intercepted by an intramolecular alcohol nucleophile. The synthetic potential of this conceptually attractive CO₂ transformation is demonstrated in the preparation of larger ring carbonates and their thermal rearrangement to sterically crowded, five-membered fused carbonate products.