Asymmetric Construction of Ethenyl-Substituted Acyclic Quaternary Stereocenters at the α-Position of Carbonyl Surrogates via Stereoselective Sulfonylvinylation-Reductive Desulfonylation.

N -Sulfinyl metalloenamines, derived from geometry-defined β,β-disubstituted enesulfinamides, undergo conjugate addition-elimination reaction with β-tosyl nitroolefin to afford α-sulfonylvinylated ketimines with high stereocontrol. Further desulfonylation using sodium naphthalenide gives carbonyl surrogates bearing a less-accessible acyclic quaternary α-stereocenters substituted with an ethenyl group and two sterically and electronically similar groups (e.g., methyl and ethyl). Synthetic application of the described protocol was demonstrated by enantioselective synthesis of ( S )-bakuchiol.