Catalytic Aerobic Oxidation of Alcohols using Recoverable IAPNO α-Hydrogen Nitroxyl Radicals.

α-Hydrogen-substituted nitroxyl radicals are of considerable interest as catalysts for oxidation and polymerization, but are usually inherently unstable. We report herein the catalytic activity of a new family of stable iso-azaphenalene (IAPNO) α-hydrogen nitroxyl radicals in the copper/bipyridine/ N-methylimidazole co-catalyzed aerobic oxidation of alcohols. The nitroxyl radical Mes/TIPSO-IAPNO (TIPSO=triisopropyloxy, IAPNO=isoazaphenalene N-oxyl) displays higher activity than TEMPO in the oxidation of benzylic and allylic alcohols. Alkyl, benzyl, allyl, and propargyl alcohols are oxidized with yields up to 96 %. The readily prepared nitroxyl catalysts are recovered in 75-90 % yield after purification of the reaction mixture and are recycled. [ABSTRACT FROM AUTHOR]