Formation of quaternary chiral centers by N-heterocyclic carbene-Cu-catalyzed asymmetric conjugate addition reactions with Grignard reagents on trisubstituted cyclic enones.

The copper-catalyzed conjugate addition of Grignard reagents to 3-substituted cyclic enones allows the formation of all-carbon chiral quaternary centers. We demonstrate in this article that N-heterocyclic carbenes act as efficient chiral ligands for this transformation. High enantioselectivities (up to 96% ee) could be obtained for a variety of substrates.