Asymmetric Fe^II-Catalyzed Thia-Michael Addition Reaction to α,β‑Unsaturated Oxazolidin-2-one Derivatives

A highly enantioselective Fe^II-catalyzed thia-Michael addition to α,β‑unsaturated carbonyl derivatives was developed. The scope of the reaction was demonstrated with a selection of aromatic, heterocyclic and aliphatic thiols, and various Michael acceptors. The corresponding β-thioethers were obtained in good to excellent yields (up to 98%) and moderate to excellent enantioselectivities (up to 96:4 er). Unusual hepta-coordination of the metal and chelation to α,β-unsaturated oxazolidin-2-one derivatives allowed the construction of a coherent model rationalizing the enantioselective event. DFT calculations support the proposed model for observed stereoselectivities.