Chiral Phosphoric Acid‐Catalyzed Enantioselective Aza‐Friedel–Crafts Reaction of Indoles

Abstract A highly enantioselective 1,2‐aza‐Friedel–Crafts reaction of N ‐ tert ‐butyldimethylsilylindole with N ‐ tert ‐butoxycarbonyl aromatic imines is demonstrated using a BINOL‐derived monophosphoric acid catalyst. The present approach provides efficient access to 3‐indolylmethaneamines with aryl substituents in excellent enantioselectivities (up to 98 % ee ). An inversion in the sense of enantioselection was found between monophosphoric acid catalysts bearing different substituents introduced at the 3,3′‐position of binaphthyl backbone. We also calculated the three‐dimensional structure of the monophosphoric acid catalysts to speculate on the inversion of the stereochemical outcome.