Stereodivergent dehydrative allylation of ß-keto esters using a Ru/Pd synergistic catalyst.

α-Alkylation of a ß-keto ester is a frequently used reaction for carbon-carbon bond formation. However, extension to a stereoselective reaction remains a significant challenge, because the product easily racemizes under acidic or basic conditions. Here, we report a hybrid system consisting of Pd and Ru complexes that catalyzes the asymmetric dehydrative condensation between cinnamyl-type allylic alcohols and ß-keto esters. α-Non-substituted ß-keto ester can be allylated to afford an α-mono-substituted product with high regio-, diastereo-, and enantioselectivity. No epimerization occurs owing to the nearly neutral conditions, which is achieved by a rapid proton transfer from Pd-enolate formation to Ru π-allyl complex formation. Four diastereomers can be synthesized on demand by changing the stereochemistry of the Pd or Ru complex. Eight stereoisomers with three adjacent stereogenic centers can be synthesized by employing diastereoselective reduction of the ketone in the products. The formal synthesis of (+)-pancratistatin demonstrates the utility of the reaction.

Water, an Essential Element for a ZnII -Catalyzed Asymmetric Quinone Diels-Alder Reaction: Multi-Selective Construction of Highly Functionalized cis-Decalins.

A ZnII complex of a C2 -chiral bisamidine-type sp2 N 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 H2 O (H2 O: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 "H2 O-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 1 H NMR study, kinetics, X-ray crystallographic analyses of the related ZnLR complexes, and ligand and substrate structure-reactivity-selectivity relationship.

Revisiting the CuII-Catalyzed Asymmetric Friedel-Crafts Reaction of Indole with Trifluoropyruvate.

A CuII complex of bisamidine ligand L S catalyzes the Friedel-Crafts (FC) reaction of indole with trifluoropyruvate with high generality, yielding the highly enantiomerically enriched FC adduct. Electron-rich indoles have high reactivity due to a dual activation mechanism showing second-order kinetics for CuII, whereas indoles with a soft substituent at C(4) proceed at a rate that is three orders of magnitude lower via a coordination mechanism, which reverses the sense of enantioselectivity.