Readily accessible oxazolidine nitroxyl radicals: bifunctional cocatalysts for simplified copper based aerobic oxidation

Using a two-step procedure a range of bifunctional oxazolidine nitroxyl radicals have been prepared. The application of these co-catalysts to the copper-based aerobic oxidation of alcohols was then investigated. From these studies it was found that the parent tetramethyloxazolidine nitroxyl radical L1 was competent for oxidation in the presence of 2,2 -bipyridine, and the bifunctional pyridyl-containing nitroxyl radicals L2 and L3 could be used in the absence of additional coordinating ligands. Following optimization, the scope of this simplified transformation was explored, demonstrating that a range of primary and secondary benzylic alcohols are readily oxidized. In addition, the oxidation of allylic alcohols and hydroquinone can be achieved.