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 towards these CO2 based synthons using hydroxyl-substituted cyclic epoxide precursors and their catalytic conversion, to afford these challenging target compounds with fused ring sizes up to eight under excellent stereo-control. 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 pendent hydroxyl nucleophile. This new manifold therefore provides an alternative approach towards CO2 valorization into functional, cyclic carbonate scaffolds of use in synthetic chemistry.