Organocatalytic Trapping of Elusive Carbon Dioxide Based Heterocycles by a Kinetically Controlled Cascade Process

A conceptually novel approach is described for the synthesis of six‐membered cyclic carbonates derived from carbon dioxide. The approach utilizes homoallylic precursors that are converted into five‐membered cyclic carbonates having a β‐positioned alcohol group in one of the ring substituents. The activation of the pendent alcohol group through an N‐heterocyclic base allows equilibration towards a thermodynamically disfavored six‐membered carbonate analogue that can be trapped by an acylating agent. Various control experiments and computational analysis of this manifold are in line with a process that is primarily dictated by a kinetically controlled acylation step. This cascade process delivers an ample diversity of six‐membered cyclic carbonates in excellent yields and chemoselectivities under mild reaction conditions. A new organocatalytic cascade process converts alcohol‐functionalized five‐membered cyclic carbonates into six‐membered analogues using organocatalysis at room temperature. This methodology delivers a wide range of elusive, substituted CO2‐based heterocycles in good yields. The chemoselectivity is kinetically controlled, offering a unique manifold to forge larger‐ring cyclic organic carbonates.