regioselectivity with respect to copper-catalyzedconjugateadditions of various Grignard reagents to cyclic enynones. The use of Cu(OTf)2 and NHC ligand L1 as the catalyst combination in CH2Cl2 led to the unique formation of the 1,4 adduct. This selectivity does not follow the general trend previously observed in the literature using extended Michael acceptors. Moreover these reactions allowed for the creation
Formation of Quaternary Stereogenic Centers by NHC-Cu-Catalyzed Asymmetric Conjugate Addition Reactions with Grignard Reagents on Polyconjugated Cyclic Enones
The copper‐catalyzedconjugateaddition of various Grignard reagents to polyconjugated enones (dienone and enynone derivatives) is reported. The catalyst system, composed of copper triflate and an NHC ligand, led to the unusual selective formation of the 1,4‐addition products. This reaction allows for the creation of all‐carbon chiral quaternary centers with enantiomeric excesses up to 99 %. The remaining