title: Regio- and stereocontrol in the Michael-initiated ring-closure reactions of γ,δ-epoxy-α,β-unsaturated esters, ketones, sulfones, and amides.
abstract: Organozincates or Grignard reagents in the presence of zinc catalysts undergo Michael initiated ring closure (MIRC) reactions with γ,δ-epoxy-α,β-enoates, enones, enesulfones, and enamides to afford 1,2,3-trisubstituted cyclopropanes. The direction of diastereoselectivity is solvent dependent for alkyl Grignard reagents reacting with epoxy enoates, ensulfones, and enamides but solvent independent for the enones. Excellent diastereoselectivity can be achieved for the epoxy enoates, enones, and ensulfones, while the enamides afford modest diastereoselectivity under optimal conditions. The MIRC reaction can be achieved with phenylmagnesium chloride and these substrates under reaction conditions designed to minimize biphenyl formation.
authors.affiliation: Hunter Laboratory, Department of Chemistry, Clemson University , Clemson, South Carolina 29634-0973, United States.
authors.forename: Ramesh C
authors.initials: RC
authors.lastname: Dhakal
authors.forename: R Karl
authors.initials: RK
authors.lastname: Dieter