Regio- and Stereocontrol in the Michael-Initiated Ring-Closure Reactions of γ,δ-Epoxy-α,β-unsaturated Esters, Ketones, Sulfones, and Amides

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.