Ein Nicht-Häm-Eisenkomplex als Katalysator für diecis-Dihydroxylierung von Olefinen: ein funktionelles Modell für Rieske-Dioxygenasen

Chen, Kui; Que, Lawrence

doi:10.1002/(sici)1521-3757(19990802)111:15<2365::aid-ange2365>3.0.co;2-q

Cited by 30 publications

(1 citation statement)

References 26 publications

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“…Perhaps even more compelling is the catalysis of cis ‐dihydroxylation by β ‐ 1 . Not only are the cis ‐diol/epoxide ratios increased by six‐ to tenfold relative to those observed for α ‐ 1 , but the cyclooctene cis ‐dihydroxylation product also derives both oxygen atoms from H 2 O 2 , as reported for 3 4, 6…”

Section: Methodsmentioning

confidence: 55%

Ligand Topology Tuning of Iron-Catalyzed Hydrocarbon Oxidations We thank the National Institutes of Health for financial support (GM33162 to L.Q.) and Fundacio La Caixa for a postdoctoral fellowship (M.C.).

Costas

Que

2002

Angew. Chem.

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Nature has evolved a number of nonheme iron oxygenases capable of the stereoselective oxidation of CÀH and CC bonds. [1,2] Still far from being understood are the factors that control the ability of iron centers to catalyze a range of reactions such as alkane hydroxylation, olefin epoxidation, and olefin cis-dihydroxylation. In our effort to develop bioinspired nonheme iron catalysts, we have discovered a family of iron complexes with tetradentate pyridine/amine ligands that, in combination with H 2 O 2 , are capable of carrying out the above transformations with high stereoselectivity. [3±7] Enantioselectivity has also been obtained with the chiral ligand N,N'-bis(2-pyridylmethyl)-N,N'-dimethyl-trans-1,2-di-aminocyclohexane (bpmcn). [8] A priori, tetradentate ligands with this type of architecture can adopt three different topologies (Scheme 1). [9±11] While Schiff×s base ligands (e.g. salen) often afford complexes with the trans or planar Scheme 1. Three different topologies that can be adopted by tetradentate ligands such as N,topology, ligands such as bpmcn in which the imine functionalities have been reduced give rise to complexes with cis-a and/or cis-b topologies. We have undertaken a series of systematic studies to uncover the factors that control the catalytic reactivity of the nonheme iron center in this family of complexes. [5±7] Herein we report the unexpectedly distinct oxidation behavior of two [Fe II (bpmcn)] catalysts, whose structures differ only by their ligand topologies.[Fe II (bpmcn)(OTf) 2 ] (1, OTf trifluoromethanesulfonate) complexes in both cis-a and cis-b ligand topologies can be synthesized by independent routes, and the structures of a-1 and the related b-[Fe II (5-Me 2 -bpmcn)(OTf) 2 ] have recently been established by crystallography. [8, 12] The NMR spectra of the two complexes strongly suggest that they each retain their respective ligand topologies in solution (Figure 1). Complex Figure 1. 1 H NMR spectra of a-[Fe II (bpmcn)(CD 3 CN) 2 ] 2 (a) and b-[Fe II (bpmcn)(CD 3 CN) 2 ] 2 (b) in CD 3 CN solution at ambient temperature.a-1 exhibits 12 paramagnetically shifted signals, as expected for a C 2 -symmetric high-spin Fe II complex, while the b isomer shows 24 resonances. These isomers do not interconvert even after heating solutions of either isomer in acetonitrile at 50 8C for one day. The high barrier to interconversion arises from the fact that the N-methyl groups of the ligand have distinct [6] Immunogold-Silver Staining: Principles, Methods and Applications (Ed.: M. A. ] E 1 V versus NHE(Au) and E 1/2 À 0.4 V versus NHE(NH 2 OH); NHE normal hydrogen electrode. A. J. Bard, Encyclopedia of

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Section: Methodsmentioning

confidence: 55%

Ligand Topology Tuning of Iron-Catalyzed Hydrocarbon Oxidations We thank the National Institutes of Health for financial support (GM33162 to L.Q.) and Fundacio La Caixa for a postdoctoral fellowship (M.C.).

Costas

Que

2002

Angew. Chem.

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Iron‐Catalyzed Oxidation Reactions

Mayer

Bolm

Rabe

et al. 2008

Iron Catalysis in Organic Chemistry

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Catalytic Epoxidation of Alkenes by the Manganese Complex of a Reduced Porphyrinogen Macrocycle

et al. 2012

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The present paper details the first application of a fully reduced meso-octamethylporphyrinogen macrocycle as an effective ligand for simple operative manganese-catalyzed alkene epoxidation. The efficiency of the novel catalyst was determined in the presence of various oxidants, apical ligands and acidic/basic additives. Higher reactivity was found in favour of electron-rich alkenes, whereas an electron-deficient conjugated alkene appeared as a poor substrate in the screening. Sulfur additives were active as apical ligands, whereas nitrogen-containing additives influenced the reactivity only moderately. cis-Stilbene and 3b-acetoxy-5-cholestene were epoxidized in a stereoselective manner. The X-ray structures of the new manganese complexes were determined and showed a rigid planar coordination geometry of the saturated macrocyclic ligand to the metal centre.

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Ein Nicht-Häm-Eisenkomplex als Katalysator für diecis-Dihydroxylierung von Olefinen: ein funktionelles Modell für Rieske-Dioxygenasen

Cited by 30 publications

References 26 publications

Ligand Topology Tuning of Iron-Catalyzed Hydrocarbon Oxidations We thank the National Institutes of Health for financial support (GM33162 to L.Q.) and Fundacio La Caixa for a postdoctoral fellowship (M.C.).

Ligand Topology Tuning of Iron-Catalyzed Hydrocarbon Oxidations We thank the National Institutes of Health for financial support (GM33162 to L.Q.) and Fundacio La Caixa for a postdoctoral fellowship (M.C.).

Iron‐Catalyzed Oxidation Reactions

Catalytic Epoxidation of Alkenes by the Manganese Complex of a Reduced Porphyrinogen Macrocycle

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