6-Disubstituted phenols are oxidized with tris(2,4-pentanedionato)manganese(III), [Mn(acac)3], in glacial acetic acid to give the corresponding 4,4′-biphenyldiols in high yields, whereas similar reactions using manganese(III) acetate, [Mn(OAc)3], insted of [Mn(acac)3] quantitatively yield the corresponding 4,4′-diphenoquinones. Cross-coupling reactions of 2,6-di-t-butylphenol and other substituted phenols afford