Organocatalytic Trapping of Elusive Carbon Dioxide Based Heterocycles by a Kinetically Controlled Cascade Process
Qiao, Chang; Villar-Yanez, Alba; Sprachmann, Josefine; Limburg, Bart; Bo, Carles; Kleij, Arjan W.
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 beta-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.
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