Binaphthyl iron porphyrins

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... 

Rose, E., Ren, Q.-z., Andrioletti, B. A unique binaphthyl strapped iron-porphyrin catalyst for the enantioselective epoxidation of terminal olefins. Chem.-Eur. J. 2004, 10, 224-230. 

Catalytic asymmetric C-H oxidation has also been achieved using metal porphyrins and metal(salen) complexes. Benzylic oxidations using vaulted binaphthyl iron(III) porphyrins,and manganese(III)(salen) complexes have suffered from moderate yields and/or enantioselectivities. However, Miyafuji and Katsuki have obtained reasonable yield and good enantioselectivity for C-H... 

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. 

Naruta et al. [225, 226] designed the twin-coronet porphyrin ligands (62) and (63) with binaphthyl derivatives as chiral substituents (Figure 13). Each face of the macrocycle is occupied by two binaphthyl units and the ligand has C2 symmetry. Iron complexes of these compounds can be very effective catalysts in the epoxidation of electron-deficient alkenes. Thus, nitro-substituted styrenes are readily epoxidized in 76-96% ee [226]. The degree of enantioselectivity can be explained on the basis of electronic interactions between the substrate aromatic ring and the chiral substituents rather than on the basis of steric interactions. 

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