Asymmetric Construction of 1,4-Diketone Derivatives Containing a Less Accessible Acyclic Quaternary Carbon Stereocenter via Michael Addition/Rearrangement Cascade

The stereoselective conjugate addition of β,β-disubstituted enesulfinamides to α-substituted nitroolefins, followed by transposition of sulfinylamino group, provides an efficient asymmetric synthetic route to 1,4-diketone derivatives. The resulting γ-imino ketone products feature an acyclic quaternary stereocenter bearing two sterically and electronically similar substituents (e.g., methyl and ethyl groups), which are challenging to construct by the conventional synthetic protocols involving C-C bond formation. The synthetic application of the described protocol was demonstrated by the asymmetric formal synthesis of the natural product hamigeran B.