Copper-catalyzed borylative cross-coupling of allenes and imines: Selective three-component assembly of branched homoallyl amines

Abstract

A copper-catalyzed three-component coupling of allenes, bis(pinacolato)diboron, and imines allows regio-, chemo-, and diastereoselective assembly of branched α,β-substituted-γ-boryl homoallylic amines, that is, products bearing versatile amino, alkenyl, and borane functionality. Alternatively, convenient oxidative workup allows access to α-substituted-β-amino ketones. A computational study has been used to probe the stereochemical course of the cross-coupling. A triumvirate: Copper-catalyzed three-component couplings of allenes, B2pin2, and imines furnish functionalized homoallylic amines, or Mannich-type products, after oxidative workup. The process utilizes a commercially available copper catalyst, tolerates a range of allene and imine substrates, and affords complex products in high yield with high regio- and diastereocontrol. Computational studies were employed to understand the stereochemical course of the cross-coupling.