Organocatalyzed Domino [3+2] Cycloaddition/Payne-Type Rearrangement using Carbon Dioxide and Epoxy Alcohols.

An unprecedented organocatalytic approach towards highly substituted cyclic carbonates from tri- and tetrasubstituted oxiranes and carbon dioxide has been developed. The protocol involves the use of a simple and cheap superbase under mild, additive- and metal-free conditions towards the initial formation of a less substituted carbonate product that equilibrates to a tri- or even tetrasubstituted cyclic carbonate under thermodynamic control. The latter are conveniently trapped in situ, providing overall a new domino process for synthetically elusive heterocyclic scaffolds. Control experiments provide a rationale for the observed cascade reactions, which demonstrate similarity to the well-known Payne rearrangement of epoxy alcohols.