Solvent‐Mediated C3/C7 Regioselective Switch in Chiral Phosphoric Acid‐Catalyzed Enantioselective Friedel‐Crafts Alkylation of Indoles with α‐Ketiminoesters

The first solvent‐mediated tunable C3/C7 regio‐ and enantioselective Friedel‐Crafts alkylation of 4‐aminoindoles with α‐ketimino esters has been developed. This catalysis allows the highly regioselective formation of indole C3 and C7 alkylation products, both in high yields (up to 96%) and excellent enantioselectivities (up to 99% ee). Mechanism study revealed that the hydrogen‐bonding interactions of the solvents with the catalyst played a vital role for the regioselectivity switch. Furthermore, the corresponding products are indole containing unnatural α‐amino acid derivatives bearing a quaternary stereocenter and enable many further elaborations.