Synthetic mimics of tyrosinase: catechols from ortho-, meta- and para-substituted phenols and copper(I) complexes

Catechols are obtained by reacting phenols bearing electron-withdrawing substituents at C-2, C-3 and C-4 and two copper(I) complexes, followed by dioxygen oxidation. A preference for the 3,4-catechol over the 2,3-catechol is observed with 3-substituted phenols. Ortho substituted phenols give very low yields in catechol. A binuclear μ-η2:η2-peroxocopper(II) phenolato complex is suggested to be the intermediate. Force field calculations permit explanation of the observed reactivity and the regiochemistry noted with meta-substituted compounds