Cu-Catalyzed β-Boration of Michael Acceptors with Bis(pinacolato)diboron

Significance

The authors describe here an improved method for performing a copper-catalyzed conjugate addition reaction of bis(pinacolato)diboron to various Michael acceptors. This protocol allows the successful addition to several classes of α,β-unsaturated compounds: substituted enones, esters, nitriles and phosphonates, using only a small amount of an inexpensive Cu-phosphine catalyst. The reaction proceeds at room temperature within several hours. The use of a chiral phosphine affords promising results in the asymmetric version of this reaction, leading after the borane oxidation to chiral β-alcohols with good enantio­selectivity.