Enantioselective Construction of Tetrasubstituted Carbon Stereocenters via Chiral Phosphoric Acid-Catalyzed Friedel–Craft Alkylation of Indoles with 5‑Substituted Hydroxybutyrolactams

The first intermolecular organocatalytic enantioselective
addition
of indoles to prochiral 5-membered cyclic N-acyliminium
ions, generated from 5-hydroxy-α,β-unsaturated pyrrolidin-2-ones,
is reported hereinafter. The reaction proceeds smoothly with a range
of 5-hydroxy-5-substituted-α,β-unsaturated pyrrolidin-2-ones
and indoles using BINOL-derived phosphoric acid catalyst to afford
α,β-unsaturated lactams embedding a tetrasubstituted stereogenic
center in high yields and enantioselectivities.