Chiral phosphoric acid-catalysed Friedel–Crafts alkylation reaction of indoles with racemic spiro indolin-3-ones

Chiral phosphoric acid-catalysed Friedel–Crafts alkylation reactions of indoles, pyrrole and 3-(dimethylamino)phenol with racemic spiro indolin-3-ones have been realised. With 5 mol% (S)-TRIP, Friedel–Crafts adducts bearing a quaternary stereocentre were obtained in up to 99% yield and 99% ee. The reaction features readily available, stable starting materials and delivers synthetically useful but challenging products.