Substrate-Triggered Stereoselective Preparation of Highly Substituted Organic Carbonates

Trisubstituted cyclic organic carbonates with multiple though well-defined stereochemical configurations are difficult to prepare. Here we present a conceptual design toward these CO2-based synthons using hydroxyl-substituted cyclic epoxide precursors and their catalytic conversion, to afford these challenging target compounds with fused ring sizes of up to eight under excellent stereocontrol. The observed stereochemistry of the organic carbonates combined with various control experiments revealed that these compounds are formed through a mechanistic manifold that involves a depolymerization reaction within an oligomeric carbonate induced by a pendant hydroxyl nucleophile. This manifold therefore provides an alternative approach toward CO2 valorization into functional cyclic carbonate scaffolds of use in synthetic chemistry.