Enantioselective Access to Tetrahydroxanthenones Catalyzed by an Ionic Proline‐Histidine Dipeptide Derivative

An enantioselective synthesis of tetrahydroxanthenones was achieved by the reaction of salicylaldehydes with cyclohex‐2‐en‐1‐one, catalyzed by a proline‐histidine dipeptide derived ion‐tagged organocatalyst in the presence of water and a Bronsted acid additive. The transformation, which involves an oxa ‐Michael addition–aldol condensation sequence, occurs at room temperature and was successful over a range of salicylaldehydes, affording the heterotricyclic products in 33–99% yield and 29–95% ee.