Oxidative using iron porphyrin complexes

Dioxo-ruthenium porphyrin (19) undergoes epoxidation.69 Alternatively, the complex (19) serves as the catalyst for epoxidation in the presence of pyridine A-oxide derivatives.61 It has been proposed that, under these conditions, a nms-A-oxide-coordinated (TMP)Ru(O) intermediate (20) is generated, and it rapidly epoxidizes olefins prior to its conversion to (19) (Scheme 8).61 In accordance with this proposal, the enantioselectivity of chiral dioxo ruthenium-catalyzed epoxidation is dependent on the oxidant used.55,61 In the iron porphyrin-catalyzed oxidation, an iron porphyrin-iodosylbenzene adduct has also been suggested as the active species.70... 

Collman et al.99 reported the asymmetric epoxidation of terminal olefins catalyzed by iron porphyrin complex 129. The catalyst was synthesized by connecting binaphthyl moieties to a readily available aa/ / -tetrakis(aminophenyl)-porphyrin (TAPP). Epoxidation of unfunctinalized olefins was carried out using iodosylbenzene as the oxidant. As shown in Scheme 4-46, excellent results were... 

An anionic ligand effect in iron porphyrin complex-catalyzed competitive epoxidations of cis- and frawi-stilbenes by BU4NHSO5 has been studied in detail . Oxidation of the thiophosphite to the thiophosphate in solid phase oligonucleotide synthesis using BU4NHSO5 was also reported. ... 

Synthetic iron porphyrin complexes such as Fe(TPP) (tetraphenylporphyrin = TPP), Fe(TMP) (Tetramesitylporphyrin = TMP), and Fe(TDCPP) (tetrakis (dichlorophenyl)porphyrin = TDCPP) (Fig. 9) have been used as models for P450 and peroxidase (9, 50-54). Early pioneering work showed that epoxida-tion catalyzed by Feln(TPP) was successfully carried out by the use of iodosylbenzene (Ph—1=0) as an oxidant (50). A very interesting feature of this model epoxidation is that the cis olefin is readily oxidized while the trans olefin is hardly oxidized (e.g., d.v-stylbene can be oxidized in 80% yield, but fraws-stylbene gave only a trace amount of the epoxide under the same conditions) (50, 55). Most of the model reactions are carried out in homogeneous organic solvents such as chloroform, dichloromethane, and acetonitrile, thus, the c/.v-epoxidation is expected to be a kinetically favorable process over the trans-epoxidation. 

N-substituted iron porphyrins form upon treatment of heme enzymes with many xenobiotics. The formation of these modified hemes is directly related to the mechanism of their enzymatic reactivity. N-alkyl porphyrins may be formed from organometallic iron porphyrin complexes, PFe-R (a-alkyl, o-aryl) or PFe = CR2 (carbene). They are also formed via a branching in the reaction path used in the epoxidation of alkenes. Biomimetic N-alkyl porphyrins are competent catalysts for the epoxidation of olefins, and it has been shown that iron N-alkylporphyrins can form highly oxidized species such as an iron(IV) ferryl, (N-R P)Fe v=0, and porphyrin ir-radicals at the iron(III) or iron(IV) level of metal oxidation. The N-alkylation reaction has been used as a low resolution probe of heme protein active site structure. Modified porphyrins may be used as synthetic catalysts and as models for nonheme and noniron metalloenzymes. 

Cytochrome P-450s carrying an iron-porphyrin complex at their active sites are representative oxidizing enzymes that catalyze the oxidation of C-H and C=C bonds. To reproduce these stereoselective biological reactions in a flask, various chiral metalloporphyrin complexes have been prepared as model compounds of the active site of P-450 [3] and used as catalysts for C-H and C=C oxidation in the... 

Heme (30), an iron porphyrin complex (Scheme 6-14), is the catalytic group in many oxidizing enzymes, including the cytochrome P-450s. Thus there has been a serious effort to mimic various aspects of these enzymes using metalloporphyrins. In the gener-... 

The use of porphyrin complexes for the electrocatalytic detection of 8O2 is limited. Iron and titanium porphyrin peroxo complexes (TPPFe-O-FeTPP or TiP(02)) interact with 8O2 to give sulfato complexes of the porphyrins or to give free sulfate Carballo et al. showed that NiPPIX polymerized on GCE catalyzed the oxidation of 8O2, and the modified electrode was stable under hydro-dynamic conditions of a flow cell . ... 

Numerous model systems for cytochrome P-450 have focussed upon the use of porphyrin complexes of chromium, manganese and iron in the presence of O2, peracids, hydroperoxides, AT-oxides or iodosylarenes as terminal oxidant [5, 6]. It is generally agreed that these systems generate a high valent metal-oxo species which participates in a rebound mechanism to shuttle an oxygen atom to a hydrocarbon... 

Pioneering work by Groves and his co-workers showed the possible use of simple synthetic heme models such as Fe (TPP) as oxidation catalysts [43-48]. In 1979, they reported alkanes and alkenes oxidations by iodosylbenzene in the presence of a catalytic amount of Fe (TPP)Cl at room temperature [39]. Chang and coworkers examined intramolecular hydroxylation by using an iron porphyrin complex having alkyl chain... 

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