Chiral Arene Ligand as Stereocontroller for Asymmetric C-H Activation

Development of chiral ligands is the most fundamental task in metal-catalyzed asymmetric synthesis. In the last 60 years, various kinds of ligands have been sophisticatedly developed. However, it remains a long-standing challenge to develop practically useful chiral η6-arene ligands, thereby seriously hampering the asymmetric synthesis promoted by arene-metal catalysts. Herein, we report the design and synthesis of a class of facilely tunable, C2 symmetric chiral arene ligands derived from [2.2]paracyclophane. Its ruthenium(II) complexes have been successfully applied in the enantioselective C-H activation to afford a series of axially chiral biaryl compounds (up to 99% yield and 96% ee). This study not only lays chemists’ longstanding doubts about whether it is possible to use chiral arene ligand to stereocontrol asymmetric C-H activation, but also opens up a new avenue to achieve asymmetric C-H activation.