Metallaphotoredox-Catalyzed Three-Component Asymmetric Cross-Electrophile Coupling for Chiral Boronate Synthesis

Here, we report a photoredox and
nickel-catalyzed cross-electrophile
coupling strategy for the asymmetric three-component 1,2-alkylarylation
of vinyl boronates with (hetero)aryl bromides and (2°, 3°)-alkyl
redox-active esters in the presence of Hantzsch ester. With a fluorinated
pyridyl-substituted chiral biimidazoline ligand, this reaction enables
straightforward access to a wide variety of synthetically valuable
chiral α-aryl boronates from readily available starting materials.
This reaction features mild conditions, broad substrate generality,
and good functional group tolerance and proceeds without using metal
reductants or alkyl halides. Furthermore, alkenyl halides and other
electron-deficient alkenes such as acrylates and vinyl phosphonates
can be applied successfully. Preliminary mechanistic studies shed
light on the potential reaction pathways and roles of organic amines.