Metalloporphyrin chiral oxidations

Oxometalloporphyrins were taken as models of intermediates in the catalytic cycle of cytochrome P-450 and peroxidases. The oxygen transfer from iodosyl aromatics to sulfides with metalloporphyrins Fe(III) or Mn(III) as catalysts is very clean, giving sulfoxides, The first examples of asymmetric oxidation of sulfides to sulfoxides with significant enantioselectivity were published in 1990 by Naruta et al, who used chiral twin coronet iron porphyrin 27 as the catalyst (Figure 6C.2) [79], This C2 symmetric complex efficiently catalyzed the oxidation... 

Finally, it is very important to note that more sophisticated catalysts have been prepared either by introducing bulky and/or chiral substituent on the meso-aryl or pyrrole rings [for recent reviews see, for instance, 36,56e,56f,63] or by inserting the metalloporphyrin into various polymeric materials [64-75, for recent reviews see also 76], These results have shown that this was a good strategy not only toward asymmetric oxidation catalysts, but also toward more regioselec-tive and/or efficient and stable catalysts. 

Y. Ferrand, R. Daviaud, P. Le Maux, G. Simonneaux, Catalytic asymmetric oxidation of sulfide and styrene derivatives using macroporous resins containing chiral metalloporphyrins (Fe, Ru), Tetrahedron Asymmetry 17 (2006) 952. 

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... 

Epoxidation of alkenes with iodosylbenzene can be effectively catalyzed by the analogous salen or chiral Schiff base complexes of manganese(in), ruthenium(II), or ruthenium(III). For example, the oxidation of indene with iodosylbenzene in the presence of (/ ,5)-Mn-salen complexes as catalysts affords the respective (15,2/ )-epoxyindane in good yield with 91-96% ee [704]. Additional examples include epoxidation of alkenes with iodosylbenzene catalyzed by various metalloporphyrins [705-709], corrole metal complexes, ruthenium-pyridinedicarboxylate complexes of terpyridine and chiral bis(oxazoUnyl)pyridine [710,711]. 

Various oxidations with [bis(acyloxy)iodo]arenes are also effectively catalyzed by transition metal salts and complexes [726]. (Diacetoxyiodo)benzene is occasionally used instead of iodosylbenzene as the terminal oxidant in biomimetic oxygenations catalyzed by metalloporphyrins and other transition metal complexes [727-729]. Primary and secondary alcohols can be selectively oxidized to the corresponding carbonyl compounds by PhI(OAc)2 in the presence of transition metal catalysts, such as RuCls [730-732], Ru(Pybox)(Pydic) complex [733], polymer-micelle incarcerated ruthenium catalysts [734], chiral-Mn(salen)-complexes [735,736], Mn(TPP)CN/Im catalytic system [737] and (salen)Cr(III) complexes [738]. The epox-idation of alkenes, such as stilbenes, indene and 1-methylcyclohexene, using (diacetoxyiodo)benzene in the presence of chiral binaphthyl ruthenium(III) catalysts (5 mol%) has also been reported however, the enantioselectivity of this reaction was low (4% ee) [739]. 

Not only the porphyrins having binaphthyl groups, strapped type metalloporphyrins are also able to catalyze asymmetric epoxidation. For example, Mansuy et al. synthesized a "Basket-Handle" iron porphyrin bearing L-phenylalanine residues (Fig. 11(d)) [297]. Collman et al. employed threitol-strapped Mn porphyrins (Fig. 11(e)) [298]. Metalloporphyrin complexes conjugated with glycosylated groups [299], p-cyclodextrin [300], and camphanoyl groups [301] were also prepared. These chiral metalloporphyrin complexes were shown to catalyze asymmetric oxidations. 

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