The Application of N‐Protected 3‐Vinylindoles in Chiral Phosphoric Acid‐Catalyzed [3+2] Cyclization with 3‐Indolylmethanols: Monoactivation of the Catalyst to Vinyliminium

A highly enantioselective [3+2] cyclization of 3‐vinylindoles with isatin‐derived 3‐indolylmethanols has been established in the presence of chiral phosphoric acid, which constructed the enantioenriched cyclopenta[ b ]indole scaffold linking a 3‐vinylindole moiety in generally good yields, considerable diastereoselectivities and high enantioselectivities (up to 93%, >95:5 dr , >99.5:0.5 er ). More importantly, this reaction utilized N‐protected 3‐vinylindoles as competent reactants, which confronted the challenge in realizing a successful monoactivation mode of chiral phosphoric acid to vinyliminium in 3‐indolylmethanol‐involved enantioselective transformations. Besides, this protocol also settled the challenge in realizing a highly enantioselective [3+2] cyclization of 3‐vinylindoles with 3‐indolylmethanols, which would serve as a useful strategy for constructing an enantioenriched cyclopenta[ b ]indole scaffold linking a 3‐vinylindole moiety.