Addition Reaction of Halogens to Vinyl(pentafluorocyclopropanes): Competition between a Radical Addition and an Electrophilic Addition

Vinylpentafluorocyclopropanes 1 react with I(2) to give the (Z)-1,5-adduct 2, whereas 1 reacts with Cl(2), Br(2) or I-Cl to produce (Z)-1,5-adduct 3 predominantly along with small amounts of 1,2-adduct 4, which are formed by a radical mechanism and an ionic mechanism, respectively.