Chiral <i>η</i> ^<i>6</i> -Benzene Ruthenium(II)-Catalyzed Asymmetric C−H Activation/Annulation To Construct C−N Axially Chiral Indoles

Asymmetric C−H activation enabled by chiral η6-benzene ruthenium (BenRu) catalysts is an emerging research field. Herein, we report the asymmetric C−H activation/annulation of anilines with alkynes catalyzed by a chiral BenRuᴵᴵ complex derived from (S)-H8−BINOL. A variety of C−N axially chiral indoles were obtained (up to 97% yield and 98% ee). Mechanistic investigations, including H/D exchange experiments and kinetic isotope effect studies, were conducted. A metallacyclic intermediate was isolated, characterized, and shown to be catalytically active in the model reaction.