Treatment of 2-ethoxycarbonylprop-2-enyl peroxides with potassium alkylperoxylate, the sodium enolate of diethyl malonate and a primary or secondary amine yields epoxides via a two-step process: (i) addition of the nucleophile to the acrylic unsaturated bond and (ii) intramolecular anionic substitution on the peroxidic bond.