Iridium‐Catalyzed Site‐ and Enantioselective C(sp²)‐H Borylation of Benzhydryl Ethers: Enantioselectivity Amplification by Kinetic Resolution Relay

Abstract

Comprehensive Summary We herein report a simple ether‐directed iridium‐catalyzed site‐ and enantioselective C(sp2)‐H borylation of benzhydryl ethers for the first time. Various chiral benzhydryl ethers were obtained with high enantioselectivities in the presence of a tailor‐made chiral bidentate boryl ligand. We found that the kinetic resolution relay significantly amplified the enantioselectivity. The synthetic utility of the current method was demonstrated by gram‐scale C—H borylation and C—B bond transformations.

Aryl Chloride-Directed Enantioselective C(sp2)-H Borylation Enabled by Iridium Catalysis

“…Inspired by this presence, we envisioned that Ar–Cl-directed asymmetric C­(sp 2 )-H borylation of arenes should be a viable approach in the presence of a proper chiral iridium catalyst . In the past few years, our group has developed Ir-catalyzed asymmetric C–H borylation enabled by chiral bidentate boryl ligands ( CBL s). , More recently, CBL /Ir catalysis was found to be effective in simple ether-directed asymmetric C–H borylation. , The low a of ethers encouraged us to further investigate Ar–Cl as the DG in asymmetric C–H borylation. We herein disclose an Ar–Cl-directed CBL /Ir-catalyzed enantioselective C–H borylation of 2,6-dichloro-1,1′-biphenyls to access axially chiral biaryls (Scheme C). ,, The method expands the chemical space of axially chiral biaryls by facile downstream diversification of C–B, ortho –C-H, and C–Cl bonds.…”