Mechanistic studies of copper(II)-mediated oxidation of vic-dioxime to furoxan

Abstract

The oxidation of vic-dioximes to furoxans by copper(II) perchlorate in acetonitrile as the oxidant has been discussed. This method was found to be applicable for a broad range of vic-dioximes. Copper complexes of 1,10-phenanthroline derived furoxans were isolated by oxidation of the corresponding copper(II) complexes of 1,10-phenanthroline based dioximes. In exploring the mechanism of copper(II)-mediated oxidative cyclization of vic-dioxime, a transient blue species was observed in the reaction pathway. Based on the spectroscopic signatures and reactivity patterns, the intermediate was proposed to be a dioximate-copper(II)-dinitrosoalkene complex. These results along with the role of metal ion and solvent in the oxidative transformation reaction are discussed in this review. © 2012 Indian Academy of Sciences.