A manganese-catalyzed regioselective ring-opening peroxidation of cyclobutanols has been disclosed. With this protocol, the C(sp 3 )À OOBu-t bond could be efficiently constructed via the radical-mediated CÀ C bond cleavage/coupling, allowing the facile access to a variety of 4-oxo peroxides. Besides, the obtained peroxidation products could be readily transformed into other synthetically attractive skeletons.