Chiral Diphosphine–Palladium-Catalyzed Sequential Asymmetric Double-Friedel–Crafts Alkylation and <i>N</i>‑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.