H2O2-and alkyl hydroperoxide-supported para hydroxylation of aniline by alkaline hematin

Under alkaline conditions and in the presence of reductant, NADH or NADPH, and molecular oxygen, hemin catalyzes the regiospecific para-hydroxylation of aniline to form p-aminophenol [P. A. Adams, D. A. Baldwin, and M. C. Berman, J. Chem. Soc. (Lond) Chem. Commun. 856 (1979); P. A. Adams and M. C. Berman, J. Inorg. Biochem. 17, 1 (1982)]. The reaction has now been studied in the presence of H2O2 and alkyl hydroperoxides and in the absence of oxygen and reductant. Results indicate that the H2O2- and alkyl hydroperoxide-supported processes proceed via different mechanisms involving, on the one hand, the hydroperoxide anion (HO2-) and on the other, the undissociated alkyl hydroperoxide molecule (ROOH). The addition of superoxide dismutase to the reaction had no effect, unlike the NADH/O2 supported reaction where the enzyme completely inhibits reaction. Similarities between the hemin-mediated peroxide-supported reactions reported here, and the cytochrome P-450-mediated peroxide-supported reactions reinforce our earlier contentions that the alkaline hemin system appears to be a good model for the in vivo activation of oxygen by hemoproteins.