Asymmetric cationic methyl pyridyl and pentafluorophenyl porphyrin encapsulated in zeolites: A cytochrome P-450 model


In this work the iron(III)tris(4-N-methylpyridyl)-mono(pentafluorophenyl)-porphyrin. was impregnated (FeP-NaYimp) and encapsulated (FeP-NaY) in the NaY zeolite and had been used as catalyst in the hydrocarbon oxidation by iodosylbenzene (PhIO) in 1,2-dichloroethane. Cyclohexane, (Z)-cyclooctene and adamantane were used as substrate. fit the case of cyclohexane. both homogeneous (FePCl4) and heterogeneous (FeP-NaYnop and FeP-NaY) systems are 100% selective towards the formation of cyclohexanol, indicating that oxygen rebound mechanism is operating. The same systems were able to epoxide (Z)-cyclooctene with yields of 92% or cisepoxycyclooctane for heterogeneous catalysts, For the FcPCl(4) system the yield of cis-epoxycyclooctane obtained was 40%. Probably. this fact is due the low solubility of the FeP in this organic media (1,2-dichloroethane) because when the Cl counter-ions were exchanged for PF6 and the solvent used was a mixture consisting of 1,2-dichloroethane/acetonitrile (1: 1) the yield of cis-epoxycyclooctane increased from 40 to 95%. Hydroxylation of adamantane shows a preferable alkane oxidation at the terciary C-H bonding as expected for a P-450 model system. The total adamantanol yields were 58, 66 and 81% for [Fe{T(4-N-MePy)MFPP}]Cl-i in solution. [Fe{T(4-N-MePy)MFPP}]Cl-4-NaYimp and [Fe{T(4-N-MePy)MFPP}]Cl-4-NaY, respectively. Concerning selectivity. the 1-adamantanol (Ad-1-oh/2-adamantanol (Ad-2-ol) ratio of 19: 1 for [Fe{T(4-N-McPy)MFPP}]Cl-4; in solution. 19:1 for [Fe{T(4-N-MePy)MFPP}]Cl4NaYm,p and 17:1 for [Fe{T(4-N-MePy)MFPP}]Cl-4-NaY were obtained (after statistic correction). These data indicate a free radical activation of the C-H bonds of adamantane. as is expected for a P-450 model. 2-Adamantanone was not obtained in any of the cases. (c) 2005 Elsevier B.V. All rights reserved.






Skrobot, FC; Rosa, ILV; Marques, APA; Martins, PR; Rocha, J; Valente, AA; Iamamoto, Y

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