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

Abstract

Abstractα‐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.