Chiral Imidodiphosphoric Acids-Catalyzed Friedel-Crafts Reactions of Indoles/Pyrroles with 3-Hydroxy-indolyloxindoles: Enantioselective Synthesis of 3,3-Diaryloxindoles

The first enantioselective Friedel–Crafts alkylation of indoles and pyrroles with 3‐hydroxy‐3‐indolyloxindoles to access two novel types of 3,3‐diaryloxindoles catalyzed by chiral imidodiphosphoric acids has been reported. A range of quaternary carbon centered 3,3‐diaryloxindoles were synthesized in high yield (up to >99%) with excellent enantioselectivity (up to 98% ee) at low catalyst loadings (as low as 0.5 mol%). The Friedel–Crafts reaction between indoles and 3‐hydroxy‐3‐indolyloxindoles is amenable to gram scale syntheses.