Dynamic kinetic C(sp2)–Si cross-coupling with Si–B reagents for the atroposelective construction of unsymmetrical heterobiaryls

A dynamic kinetic C(sp2)–Si cross-coupling of heterobiaryl triflates and silylboronic acid esters as silicon pronucleophiles is reported. The deracemization reaction proceeds typically in high yields and with 99% ee when using Pd(acac)2 as the precatalyst and CuCl as a cocatalyst, and (R)-TolBINAP as the chiral ligand. The copper salt assists the transmetalation of the Si–B reagent, thereby accelerating the reaction and also improving enantioselectivity. The method tolerates a wide range of functional groups and heterocycles, and different silyl groups can be introduced.