Conjugate Addition of Chiral Allenylcopper Species to Vinyl Bis(sulfone) To Access an All-Carbon Quaternary Center

Asymmetric formation of all-carbon quaternary centers has been recognized as a challenging area in organic synthesis. Herein, we report a copper-catalyzed approach toward coupling of two alkenyl substrates, resulting in the formation of a chiral all-carbon quaternary center. In the reaction, axially chiral tetrasubstituted allenylcopper species were generated catalytically and chemoselectively, in situ from the substituted enynes, and remarkably performed as an efficient organometallic nucleophile in conjugate addition to unsaturated sulfones.