Oxidation of Phenols and Hydroquinones by Mercury(II) Trifluoroacetate and Mercury(II) Oxide

Treatment of phenols with mercury(II) salts normally results in rapid electrophilic aromatic mercuration and formation of arylmercurial derivatives in good yield. The use of mercury(II) salts as oxidants for phenols and hydroquinones has not, however, been investigated in any detail. In 1935, Montignie reported that hydroquinone reduced mercury(II) iodide to mercury(O), but the organic reaction product was not identified.¹ A similar observation was made by Koton,² who found that reaction of hydroquinone, 4-hydroxy-aniline and pyrogallol with mercury(II) acetate did not result in mercuration but led to formation of mercury(0), while Ohno has described the “strong reducing action” of catechol and nitrohydroquinones to mercury(II) salts.³ Mercury(II) acetate has been shown to oxidise hydroquinone and 1,4-bis[β-(2,5-dihydroxyphenyl)-α-methylethylamino] anthraquinone to the corresponding quinones,^4,5 and treatment of 2,6-di-t-butyl-4-methylphenol—with mercury(II) oxide has been found to give the expected products of phenolic oxidative coupling via quinone methide formation.⁶