Modular Chiral Bisoxalamide-Copper Catalyzed Asymmetric Oxo-Diels-Alder Reaction: Carbonyl Coordination for High Enantio- and Diastereo-Controls

The chiral bis-oxalamides (CBOA), readily derived from opti-cally pure 1,2-diphenylethylenediamine (DPEN), were proven to be a class of efficient C2-symmetric chiral ligands for cop-per(II) catalyzed asymmetric inverse-electron demand oxo-Diels-Alder reactions between β,γ-unsaturated α-ketoesters and 2,3-dihydrofuran or 3,4-dihydro-2H-pyran. The reactions proceeded smoothly under mild conditions, to afford the corre-sponding [4+2] cycloadducts in high yields with good enanti-oselectivities (up to 94% ee) and diastereoselectivities (up to 99:1 dr). DFT calculations demonstrated that carbonyl coordi-nation of chiral ligand to Cu(II) was crucial for the high stereo-induction. These CBOA ligands exhibited high catalytic effi-ciency in this reaction, which combined with some other salient features of structural fine-tunablity, chemical stability, ready accessibility, might endow more practical applications in asymmetric catalytic reactions.