Chiral Phosphoric Acid Catalyzed Enantioselective Friedel‐Crafts Reaction of N‐Protected 4‐Aminoindoles with β,γ‐Unsaturated α‐Ketimino Esters

Through a hydrogen bonding guided substrate modification strategy, we have developed a chiral phosphoric acid catalyzed highly enantioselective Friedel‐Crafts reaction of N‐protected 4‐aminoindoles with β,γ‐unsaturated α‐ketimino esters. The mechanism and origins of the enantioselectivity of this process are indentified using DFT calculations. Both the experimental and calculation results indicated that the NH moiety at the indole C4 position is essential for the stereocontrol of this reaction. To further examine the potential usefulness of this method, gram scale synthesis and derivatizations of one of the products were also carried out.