Mechanistic investigation of the catalytic system based on N-hydroxy-phthalimide with vanadium co-catalysts for aerobic oxidation of alcohols with dioxygen

[n-Bu4N]VO3 or a combination of vanadium complexes with some additives, as chloride salts or amines, are attractive and effective co-catalysts for aerobic oxidation of alcohols with dioxygen catalyzed by N-hydroxyphthalimide (NHPI). The role of the additives relates to the formation of more labile six co-ordinate vanadium complexes. A mechanism for the aerobic oxidation of alcohols with dioxygen is proposed and its essential steps are the formation of oxotrialkoxyvanadium(V) complexes and generation of a phthalimide-N-oxyl (PINO•) radical as result of reaction of NHPI with oxovanadium(V) compounds. The oxidation of alcohols concerns to both radical and molecular pathways.