To comprehend the reactivity of copper(II) chelates of hydroxynaphthoquinones towards their ‘redox’ nature, the oxidation reactions are studied. The N-bromosuccinimide (NBS) in chloroform is used as oxidizing agent. The reaction products are analysed by elemental analyses, ir, nmr, electronic and esr spectral studies. The stereospecificity of ligand C-3 substituents in chelates of lawsone, phthiocol and their oximes, govern two reaction mechanisms for NBS reactant viz. electrophilic substitution SE and free radical. In chelates of phthiocol and its oxime, the ‘oxidative’ addition occurs in a unique way, by oxidation of the equatorial semiquinone ligand to a quinone rather than metal, with simultaneous axial addition of bromine on metal.

M. P. Mulay, P. L. Garge, S. B. Padhye, R. C. Haltiwanger, L. A. deLearie and C. G. Pierpont, J. Chem. Soc., Chem. Commun., 1987, 581 DOI: 10.1039/C39870000581