Organocatalytic Synthesis of Substituted Vinylene Carbonates.

The organocatalytic synthesis of substituted vinylene carbonates from benzoins and acyloins was studied using diphenyl carbonate as a carbonyl source. A range of N-Heterocyclic Carbene (NHC) precursors were screened and it was found that imidazolium salts were the most active for this transformation. The reaction occurs at 90 °C under solvent-free conditions. A wide range of substituted vinylene carbonates (symmetrical and unsymmetrical, aromatic or aliphatic), including some derived from natural products, were prepared with 20-99% isolated yields (24 examples). The reaction was also developed using thermomorphic polyethylene-supported organocatalysts as recoverable and recyclable species. The use of such species facilitates the workup and allows the synthesis of vinylene carbonates on the preparative scale (>30 g after 5 runs). [ABSTRACT FROM AUTHOR]