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.