Chiral Bis‐Oxalamide‐Rare Earth Complex Catalyzed Inverse‐ Electron‐Demand Asymmetric oxa‐Hetero‐Diels‐Alder Reaction for Optically Active Dihydropyran Core Structures

Chiral bis‐oxalamide (CBOA)/rare‐earth metal complexes‐catalyzed asymmetric inverse‐electron‐demand oxa‐hetero‐Diels‐Alder (HDA) reactions were investigated under mild reaction conditions, which was performed between β,γ‐unsaturated α‐ketoesters and various electron‐riched dienophiles, such as cyclopentadiene, 2,3‐dihydrofuran, 3,4‐dihydro‐2H‐pyran, tetrahydropyridine as well as phenyl(vinyl)sulfane. Several series of optically active functionalized 3,4‐dihydro‐2H‐pyran or ring fused dihydropyran derivatives were obtained in high yields with high diastereo‐ and enantioselectivity. The procedure was able to tolerate a relatively wide range of substrates. The coordination mode of chiral bis‐oxalamide with Sc(III) was demonstrated by the X‐ray crystallographic structure, and DFT calculations were carried out to uncover the regio‐ and stereocontrol.