824427-15-8Relevant articles and documents
Water, an Essential Element for a ZnII-Catalyzed Asymmetric Quinone Diels-Alder Reaction: Multi-Selective Construction of Highly Functionalized cis-Decalins
Morimoto, Kyosuke,Le, Thien Phuc,Manna, Sudipta Kumar,Kiran, I. N. Chaithanya,Tanaka, Shinji,Kitamura, Masato
supporting information, p. 3283 - 3290 (2019/11/05)
A ZnII complex of a C2-chiral bisamidine-type sp2N bidentate ligand (LR) possessing two dioxolane rings at both ends catalyzes a highly efficient quinone asymmetric Diels-Alder reaction (qADA) between o-alkoxy-p-benzoquinones and 1-alkoxy-1,3-butadienes to construct highly functionalized chiral cis-decalins, proceeding in up to a >99:1 enantiomer ratio with a high generality in the presence of H2O (H2O:ZnII=4–6:1). In the absence of water, little reaction occurs. The loading amount of the chiral ligand can be minimized to 0.02 mol % with a higher Zn/LR ratio. This first success is ascribed to a supramolecular 3D arrangement of substrates, in which two protons of an “H2O-ZnII” reactive species make a linear hydrogen bond network with a dioxolane oxygen atom and one-point-binding diene; the ZnII atom captures the electron-accepting two-points-binding quinone fixed on the other dioxolane oxygen atom via an n-π* attractive interaction. The mechanisms has been supported by 1H NMR study, kinetics, X-ray crystallographic analyses of the related ZnLR complexes, and ligand and substrate structure-reactivity-selectivity relationship.
