Self‐Terminating Radical Oxygenations: Probing of the Scope of the Concept by Use of Various Organic O ‐Centered Radicals

Addition of various organic O ‐centered radicals XO • {i.e. (alkoxycarbonyl)oxyl radicals, ROC(O)O • , [(alkoxycarbonyl)acyl]oxyl radicals, ROC(O)C(O)O • , (carbamoyl)oxyl radicals, R 2 NC(O)O • , alkoxyl radicals, RO • , and nitroxyl radicals, R 2 NO • } to alkynes initiates an oxidative radical cyclization cascade, which is terminated by release of a C ‐ or N ‐centered radical X • . This finding clearly highlights the generality of the recently discovered concept of self‐terminating radical oxygenations, through which C≡C triple bonds may be converted into carbonyl groups under very mild reaction conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)