Singletoxygenation of 2,2,3,3-tetraaryloxadisiliranes 1a-d gives the corresponding 1,2,4,3,5-trioxadisilolanes 2a-d, derivatives of a novel class of cyclic peroxides. The reaction mechanism is discussed in terms of possible peroxonium ion intermediate 6a as a nucleophilic oxidizing species.