Sulfate radical anions (SO(4)(*)(-)) as donor of atomic oxygen in anionic transannular, self-terminating, oxidative radical cyclizations.

SO(4)()(-) generated by the Fenton redox system S(2)O(8)(2)(-)- Fe(2+) induces a novel anionic, transannular, self-terminating, oxidative radical cyclization in the reactions with the ten-membered cycloalkyne 1 and the cycloalkynone 7, yielding the bicyclic ketones 5 and 6 or the alpha,beta-epoxy ketones 8 and 9, respectively. In these reactions SO(4)()(-) acts as an oxygen transfer reagent and can thus be considered as a donor of atomic oxygen in solution.