Bifunctional Thiourea-Catalyzed Asymmetric Inverse-Electron-DemandDiels–Alder Reaction of Allyl Ketones and Vinyl 1,2-Diketonesvia Dienolate Intermediate

Inverse-electron-demand Diels–Alder reactions have attracted intense research focus. However, enolate and enamine are the most employed intermediates to realize such transformation, and the use of dienolate intermediate remains elusive. Reported herein is the asymmetric inverse-electron-demand oxa-Diels–Alder reaction between allyl ketones and alkenyl 1,2-diketones using a bifunctional thiourea catalyst. The reaction afforded various highly functionalized dihydropyrans with good to excellent enantioselectivities under mild conditions, and further novel transformations on the products have also been realized.