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First success of catalytic epoxidation of olefins by an electron-rich iron(III) porphyrin complex and H2O2: Imidazole effect on the activation of H2O2 by iron porphyrin complexes in aprotic solvent

Title
First success of catalytic epoxidation of olefins by an electron-rich iron(III) porphyrin complex and H2O2: Imidazole effect on the activation of H2O2 by iron porphyrin complexes in aprotic solvent
Authors
Nam W.Lee H.J.Oh S.-Y.Kim C.Jang H.G.
Ewha Authors
남원우
SCOPUS Author ID
남원우scopus
Issue Date
2000
Journal Title
Journal of Inorganic Biochemistry
ISSN
0162-0134JCR Link
Citation
vol. 80, no. 3-4, pp. 219 - 225
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
An electron-rich iron(III) porphyrin complex (meso- tetramesitylporphinato)iron(III) chloride [Fe(TMP)Cl], was found to catalyze the epoxidation of olefins by aqueous 30% H2O2 when the reaction was carried out in the presence of 5-chloro-1-methylimidazole (5-Cl-1-MeIm) in aprotic solvent. Epoxides were the predominant products with trace amounts of allylic oxidation products, indicating that Fenton-type oxidation reactions were not involved in the olefin epoxidation reactions. cis-Stilbene was stereospecifically oxidized to cis-stilbene oxide without giving isomerized trans-stilbene oxide product, demonstrating that neither hydroperoxy radical (HOO·) nor oxoiron(IV) porphyrin [(TMP)Fe(IV) = O] was responsible for the olefin epoxidations. We also found that the reactivities of other iron(III) porphyrin complexes such as (meso-tetrakis(2,6- dichlorophenyl)porphinato)iron(III) chloride [Fe(TDCPP)Cl], (meso- tetrakis(2,6-difluorophenyl)porphinato)iron(III) chloride [Fe(TDFPP)Cl], and (meso-tetrakis(pentafluorophenyl)porphinato)iron(III) chloride [Fe(TPFPP)Cl] were significantly affected by the presence of the imidazole in the epoxidation of olefins by H2O2. These iron porphyrin complexes did not yield cyclohexene oxide in the epoxidation of cyclohexene by H2O2 in the absence of 5-Cl-1-MeIm in aprotic solvent; however, addition of 5-Cl-1-MeIm to the reaction solutions gave high yields of cyclohexene oxide with the formation of trace amounts of allylic oxidation products. We proposed, on the basis of the results of mechanistic studies, that the role of the imidazole is to decelerate the O-O bond cleavage of an iron(III) hydroperoxide porphyrin (or H2O2-iron(III) porphyrin adduct) and that the intermediate transfers its oxygen to olefins prior to the O-O bond cleavage. (C) 2000 Elsevier Science S.A.
DOI
10.1016/S0162-0134(00)00085-4
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자연과학대학 > 화학·나노과학전공 > Journal papers
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