Some factors influencing the selectivity of styrene oxidation by active oxygen donors catalyzed by three generations of ironporphyrins

In this work, we used representatives of 3 generations of metalloporphyrins [Fe(TPP)Cl, 1st generation; Fe(Cl6P)Cl, 2nd generation; and Fe(Cl14P)Cl, 3rd generation] as catalysts in the oxidation of styrene by PhIO and t-BuOOH to evaluate the influence of the reaction conditions on the mechanisms and catalytic efficiency of these catalysts. Increased substitution of hydrogen atoms on the phenyl groups and β-pyrrolic rings for electron-withdrawing elements such as halogens makes the catalytic species more reactive and prevents ironporphyrin self-destruction. However, an excess of such substituents in the 3rd generation complex is not a guarantee of high product yields, because of the steric effect of these substituents on the reaction mechanisms. In turn, other parameters such as solvent, oxidant, and axial ligands can be set up in order to favor the mechanism responsible for the high selectivity for the desired product.