Highly Regio‐, Stereo‐, and Enantioselective Copper‐Catalyzed B−H Bond Insertion of α‐Silylcarbenes: Efficient Access to Chiral Allylic gem‐Silylboranes

Herein, we report the development of a method for highly regio‐, stereo‐, and enantioselective B−H bond insertion reactions of α‐silylcarbenes generated from 1‐silylcyclopropenes in the presence of a chiral copper(I)/bisoxazoline catalyst for the construction of chiral γ,γ‐disubstituted allylic gem‐silylboranes, which cannot be prepared by any other known methods. This reaction is the first highly enantioselective carbene insertion reaction of α‐silylcarbenes ever to be reported. The method shows general applicability for various 3,3‐disubstituted silylcyclopropenes and exclusively affords E‐products. The novel chiral γ,γ‐disubstituted allylic gem‐silylborane products are versatile allylic bimetallic reagents with high stability and have great synthetic potential, especially for the construction of complex molecules with continuous chiral centers. We developed a highly regio‐, stereo‐, and enantioselective CuI‐catalyzed ring‐opening/B−H bond insertion reaction between 1‐silylcyclopropenes and borane adducts, which represents the first highly enantioselective carbene insertion reaction of α‐silylcarbenes, and enriches the accesses and type of chiral gem‐bimetallic reagents.