p-Quinoneimine as an intermediate in the oxidative coupling of 2-amino-5-methylphenol to 4a,7-dimethyldihydro-2-aminophenoxazinone catalyzed by a monomeric copper(II) complex

•Bis-benzimidazol ligand and its copper(II) complex•Oxidation of 2-amino-5-methylphenol•p-Quinoneimine intermediate formation•The reaction is self- inhibiting with increasing substrate concentration.•4a,7-Dimethyldihydro-2-aminophenoxazinone is found as the final product.

Copper(II) complex of a tetradentate N-picolatedbisbenzimidazolyl ligand is synthesized and characterized. XRD study reveals that copper(II) is in a distorted square plane comprising of two imine nitrogen, one oxygen atom from nitrate and another from a water molecule. This complex carries out the oxidative coupling of aminomethylphenol to phenoxazinone through an intermediate p-quinoneimine. The reaction is pseudo first order with respect to the catalyst and is self-inhibiting with increasing substrate concentration. Anion like acetate is found to increase the rate of reaction by nine times. EPR monitoring indicates the formation of a Cu(I) species which is the likely cause of inhibition of the catalytic reaction.

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