Enantioselective, Palladium-Catalyzed Conjugate Additions of Arylboronic Acids to Form Bis-benzylic Quaternary Stereocenters

We report enantioselective,
palladium-catalyzed conjugate additions
of arylboronic acids to β-aryl, β,β-disubstituted
enones to generate ketones containing bis-benzylic quaternary stereocenters.
A catalyst generated from palladium trifluoroacetate and (S)-4-tert-butyl-2-(2-pyridyl)­oxazoline
ligand ((S)-t-BuPyOx) promotes conjugate
additions of a wide range of arylboronic acids to a variety of β-aryl,
β,β-disubstituted enones. Iterative addition of the arylboronic
acid to minimize undesired protodeboronation pathways leads to efficient
formation of the corresponding ketones containing bis-benzylic quaternary
stereocenters in up to 92% yield and up to 93% enantioselectivity.