Enantioselective synthesis of N–C axially chiral indoles through chiral palladium-catalyzed 5-endo-hydroaminocyclization

In the presence of (R)-SEGPHOS-PdCl2 catalyst, 5-endo-hydroaminocyclization of various 2-(tert-butyl)-N-(2-ethynylphenyl)anilines proceeds enantioselectively to afford optically active N–C axially chiral N-(2-tert-butylphenyl)indole derivatives in good yields. The enantioselectivity depends strongly on the bulkiness of ortho-substituents and the electron density on the arylethynyl group, and it is explained by the dynamic axial chirality generated by the twisting of the aryl substituent.