When γ,δ-epoxy-α,β-unsaturated esters or amides were treated with 2 equiv of Grignard reagents in the presence of 10−24 mol % FeCl2, regio- and stereoselective substitution of the epoxide moiety with the Grignard reagent occurred to give exclusively δ-hydroxy-γ-alkyl or aryl-α,β-unsaturated esters or amides in good yields.