Oxidation of Hydroquinones with Oxygen in the Presence of Bis(1,3-propanediaminato)copper(II) Chloride

Treatment of hydroquinones such as 1,2-dihydroxybenzene, 1,4-dihydroxybenzene and its 2-methyl derivative, 1,2,4-trihydroxy-6-methylbenzene, 1,2- and 1,4-dihydroxynaphthalene with oxygen in ethanol in the presence of bis (1,3-propanediaminato)copper(II) chloride and a few drops of acetic acid effects oxidative C-C coupling plus oxidation of the hydroquinone to the quinone system to afford the corresponding biquinones in yields exceeding 75%.