Abstract: The reactions of AcON02 with the cyclic olefins cyclopentene, cyclohexene, cis- cyclooctene, methylenecyclobutane, and norbornene have been investigated or, in some cases, reinvestigated. Although many products are formed, material balances in the order of 80% have been achieved in all cases, and structures have been assigned to the products. In contrast to previous results, 1, 2-addition is found to be always a minor pathway, which is ...