Nickel-Catalyzed Boron-Stereogenic Hydroboration

Hydroboration is one of the most widely utilized reactions
for
olefin functionalization and organoboron synthesis. While asymmetric
hydroboration is well established for creating homochiral alkanes
with stereogenic carbon centers, catalytic hydroboration to incorporate
boron stereocenters remains an unresolved challenge. In this work,
through the rational design of a nickel/chiral phosphoramidite catalyst
system, we report a boron-stereogenic hydroboration of a wide range
of unactivated and activated olefins using a prochiral, four-coordinate
vinylborane reagent. This reaction enables the construction of enantioenriched
B(sp3)–C(sp3) skeletons containing both
boron and carbon stereocenters. Experimental and computational studies
reveal a unique ligand-to-ligand hydrogen transfer pathway for the
activation and metalation of inert B(sp3)–H bonds,
providing mechanistic insights into the observed enantioselectivity.
With its broad substrate scope and remarkable functional group compatibility,
this protocol offers access to various acyclic chiral organoboranes
with structural diversity.