State of the art in the development of biomimetic oxidation catalysts

Work during the last decade laid down the basis for biomimetic oxidation catalysis, which has become an established technique. Preliminary work relied on the use of metal complexes of 5,10,15,20-tetrakisphenylporphyrin (TPP), but these proved to be inadequate to perform the catalytic function. Further, derivatives of TPP with suitable and adequately positioned substituents, allowed the preparation of high performance catalysts, in terms of catalytic efficiency and stability, for some selected oxidations under specific reaction conditions and for a diversity of oxygen donors. The first oxidations were achieved using the 'special' oxygen donor iodosylbenzene, but cheaper and generally available oxidants such as sodium hypochlorite or hydrogen peroxide are presently used as the oxidants. Catalysts capable of promoting stereoselective catalysis are reported. Conditions for the efficient use of the catalysts so far reported require particular specificities and the catalytic activity is only shown, in the majority of the reported works, in the presence of selected species to act as axial ligands to the metal ion of the catalyst. Specific porphyrin structures were reported where the addition of a specific axial ligand can be avoided.