One‐Pot Synthesis of Pyrrolo[1,2‐a]indoles by Chiral N‐Triflyl Phosphoramide Catalyzed Friedel‐Crafts Alkylation of 4,7‐Dihydroindole with β,γ‐Unsaturated α‐Keto Esters

Abstract Chiral N‐triflyl phosphoramide was found an efficient catalyst for the enantioselective Friedel‐Crafts alkylation reaction of 4,7‐dihydroindole with β,γ‐unsaturated α‐keto esters. In the presence of 5 mol% of the optimized catalyst, various pyrrolo[1,2‐a]indoles were obtained in excellent enantioselectivity, moderate yields and up to 3:1 diastereoselectivity based on the one‐pot synthesis including the Friedel‐Crafts alkylation reaction and the subsequent p‐benzoquinone oxidation.