Hydroxylation of phenolic compounds

摘要

Phenolic compounds, e.g., phenol, are hydroxylated, preponderantly into the para-isomer, e.g., hydroquinone, by reaction with hydrogen peroxide in the presence of an effective amount of a strong acid and a catalytically effective amount of a keto compound having the formula (II): (II) in which R1 and R2, which may be identical or different, are each a hydrogen atom or an electron-donating group; n1 and n2, which may be identical or different, are numbers equal to 0, 1, 2 or 3, with the proviso that the two carbon atoms located at the alpha -position with respect to the two carbon atoms bearing the -CO group may be bonded together via a valence bond or via a -CH2- group, thereby forming a keto-containing ring member which may either be saturated or unsaturated.