L-Proline as a Catalyst for the Synthesis of Polysubstituted Pyran Derivatives via Multicomponent Reaction

An operationally simple, one-pot multicomponent protocol has been developed for the assembly of polysubstituted pyrans via an atom-economic transformation incorporating benzaldehyde, 4-hydroxycoumarin (dimedone, or cyclohexane-1,3-dione), and benzoylacetonitriles. This process involves L-proline-catalyzed domino condensation and Michael addition. The reaction is carried out by simply mixing the reactants and the catalyst in ethanol, followed by heating at 70°C, and the products are isolated in good yields after convenient workup.