IAPNO Nitroxyl Radical Catalyzed Aerobic Oxidation of Alcohols and Amines

Jayprakash Kumar, Chemistry, Technion-Israel Institute of Technology, Haifa, Israel
Alex Szpilman, Chemistry, Technion-Israel Institute of Technology, Haifa, Israel

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-aza-phenalene (IAPNO) α-hydrogen nitroxyl radicals in the copper/bipyridine/N-methyl-imidazole co-catalyzed aerobic oxidation of alcohols and amines. The nitroxyl radical Mes/TIPSO-IAPNO displays higher activity than TEMPO and ABNO in the oxidation of benzylic and allylic alcohols. Alkyl, benzyl, allyl, and propargyl alcohols are oxidized with isolated yields of the carbonyl products up to 96%. IAPNO can also oxidize benzylic amines to their corresponding nitriles. The best condition for the conversion from amine to nitrile is IAPNO in combination with CuI/t-BuBPy/DMAP in acetonitrile under an oxygen atmosphere. The readily prepared nitroxyl catalyst is recovered in 75-90% yield after purification of the reaction mixture.