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

Abstract

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.