Copper(ii) mediated phenol ring nitration by nitrogen dioxide

Abstract

Cu(II) complexes of N₂O₂ type ligands, L¹H₂ and L²H₂ [L¹H₂ = 6,6′-(((pyridin-2-ylmethyl)azanediyl)bis(methylene))bis(2,4-di-tert-butylphenol); L²H₂ = 2,4-di-tert-butyl-6-(((3-(tert-butyl)-2-hydroxy-5-methylbenzyl)(pyridin-2-yl-methyl)amino)methyl)phenol], have been synthesized. Addition of nitrogen dioxide (NO₂) in THF solutions of the complexes resulted in the nitration at the 4-position of a coordinated equatorial phenolate ring of the ligand frameworks. This nitration did not occur at the phenol ring which is axially coordinated to the metal center. Spectroscopic evidence suggests that the reaction proceeds through a phenoxyl radical complex formation.