This paper reports the allylic bromide rearrangement of 3-bromo-3-alkenyl-azetidin-2-ones, induced by m-chloroperbenzoic acid, N-bromosuccinimide or benzoylperoxide as radical initiators. The substitution of bromide by resin supported acids, followed by hydrolysis of the ester moiety, allowed an hydroxyl- or keto-function to be introduced in the C3 side chain of the azetidinone, thus giving access to a new class of potential cholesterol absorption inhibitors.