Oxidation of hindered aniline to iminocyclohexa-2,4-dienone by copper(II) complex of an N-substituted bis-benzimidazolyl ligand

•Bis-benzimidazolyl ligand and its copper(II) complex.•Oxidation of 2,4,6-tri-tert-butylaniline.•3,5-Di-tert-butyl-6-iminocyclohexa-2,4-dienone found as major product.•Copper(III)/copper(II) cycle operates during catalytic oxidation.

Copper(II) complex of an N-octylated bis-benzimidazolyl ligand is synthesized and characterized. X-ray diffraction study revealed that copper(II) is in a distorted square-planar environment of two benzimidazolyl imine nitrogens and two nitrato ligands. This complex carries out the oxidation of 2,4,6-tri-tert-butylaniline at room temperature utilizing low amounts of tert-butylhydroperoxide (TBHP) as an alternate source of oxygen. 3,5-Di-tert-butyl-6-iminocyclohexa-2,4-dienone is found to be the major product along with 3,5-di-tert-butylcyclohexa-3,5-diene-1,2-dione. The oxidation products have been isolated and characterized by 1H NMR, 13C NMR and COSY experiments. The catalytic oxidation proceeds via a copper(II)/copper(III) cycle.

Graphical abstractCopper(II) complex of an N-octylated bis-benzimidazolyl ligand, carries out the oxidation of 2,4,6-tri-tert-butylaniline in presence of low amounts of tert-butylhydroperoxide (TBHP). 3,5-Di-tert-butyl-6-iminocyclohexa-2,4-dienone is found to be the major product. The catalytic oxidation proceeds via a copper(III)/copper(II) cycle.Figure optionsDownload full-size imageDownload as PowerPoint slide