Tetra-crowned porphyrin as P450 biomimetic model for carbamazepine oxidation
Juvenal C. S. Filho, Tatiana C. O. Mac Leod, Maria Carolina A. F. Gotardo, Marilda das Dores Assis*
Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, Ribeirão Preto 14040-901, São Paulo, Brasil
Dedicated to Professor António M. d’A. Rocha Gonçalves
A substituted porphyrin bearing four crown ether units, H2(TCP), was synthesized from the reaction between (5,10,15,20-tetra(o-aminophenyl)porphyrin) and the acyl derivative of the ether (4-carboxy-18-crown-6). The free-base porphyrin was characterized by C, N, and H elemental analysis; UV-vis and IR spectroscopies; and 1H NMR. The corresponding ironporphyrin, Fe(TCP)Cl, was obtained via iron insertion into H2(TCP). Fe(TCP)Cl was employed as catalyst for carbamazepine (CBZ) oxidation by iodosylbenzene (PhIO), 3-chloroperoxybenzoic acid (m- CPBA) or sodium hypochlorite (NaOCl), in methanol or in a biphasic water/dichloroethane system. The crowned ironporphyrin proved to be a highly efficient and selective catalyst for CBZ epoxidation even in the biphasic dichloroethane /H2O system, with no need for an additional phase transfer agent.
Keywords: Porphyrins, crown ether, oxidation, carbamazepine, catalysis
There has been considerable research interest in the synthesis of porphyrins with various substitutents in view of their ability to function as models that mimic several biofunctions such as heme oxygenation and cytochrome activity.1 The design of model compounds depends on the judicious choice of the substituent and the peripheral position to be substituted. Minor changes in the basic structure of the macrocyclic ring bring significant changes to the properties of porphyrins, a fact that has been widely employed in the design of a great variety of compounds, for purposes as specific as the preparation of metalloenzyme models and the synthesis of