Base‐Free β‐Boration of α,β‐Unsaturated Imines Catalysed by Cu2O with Concurrent Enhancement of Asymmetric Induction

The stereoselective synthesis of γ-aminoalcohols from the catalytic asymmetric β-boration of α,β-unsaturated imine precursors has been streamlined with the use of Cu2O as the catalyst, readily accessible (R)-(+)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl as the chiral ligand and no additional base. The new simplicity of the catalytic system has the added value of in situ formation of the imines, which allows access to cyclic and acyclic β-boryl imines. The reaction was followed by using in situ IR spectroscopy, which demonstrated the imine formation– β-boration sequence and that the new catalytic system is superior to those employed for this reaction previously.