Formation of Quaternary Chiral Centers by N-Heterocyclic Carbene-Cu-Catalyzed Asymmetric Conjugate Addition Reactions with Grignard Reagents on Trisubstituted Cyclic Enones
The copper‐catalyzedconjugateaddition 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.