Chiral Diphosphine-Palladium-Catalyzed Sequential Asymmetric Double-Friedel-Crafts Alkylation and N-Hemiketalization for Spiro-polycyclic Indole Derivatives.

An efficient cascade asymmetric Friedel-Crafts alkylation/N-hemiketalization/Friedel-Crafts alkylation reaction of 3-alkylindoles with oxindolyl β,γ-unsaturated α-ketoesters has been developed in the presence of a chiral diphosphine-palladium(II) catalyst. A series of enantiomerically enriched spiro-polycyclic indole derivatives have been constructed in high yields with excellent enantioselectivities and diastereoselectivities.