Organocatalytic Synthesis of Vinylene Carbonates Using Dimethyl Carbonate as a Carbonyl Source

Abstract Vinylene carbonates (also referred as endo‐vinylene carbonates) were prepared from α‐hydroxyketones and dimethylcarbonate as a cheap and safe carbonyl source. The reaction is performed neat at 90 °C and is catalyzed by an imidazolium salt bearing a hydrogenocarbonate counter‐ion, thus avoiding the need of an external base. The equilibrium was shifted toward the formation of the desired products by removal of methanol using 4 Å molecular sieves, placed outside the reaction vessel. Under these conditions, a range of symmetrical and unsymmetrical, aryl and alkyl vinylene carbonates was prepared with 10%–93% isolated yield (22 examples). A ten‐fold scale‐up experiment was also performed in a Soxhlet apparatus using benzoin as a starting material and the desired vinylene carbonate was obtained with 92% yield. This protocol provides a convenient access to vinylene carbonates on a multi‐gram scale.