Biomimetic Iron‐Catalyzed Asymmetric Epoxidation of Aromatic Alkenes by Using Hydrogen Peroxide

Gelalcha, Feyissa Gadissa; Anilkumar, Gopinathan; Tse, Man Kin; Brückner, Angelika; Beller, Matthias

doi:10.1002/chem.200800595

Cited by 134 publications

(63 citation statements)

References 51 publications

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“…[150] Thel atter radicals (HOC and the oxyl radical of cyclohexenol) were trapped as DMPO adducts (vide supra)a nd identified by EPR, following the method describedb yB eller. [82] Reaction of the complexes with H 2 O 2 wass tudied by UV-Vis and EPR spectroscopy and the formation of (L10)FeOOH and (L11)FeOOH intermediates was proposed. Such low-spin intermediates have been found to slowly build up and then decay in the presence of the substrates.…”

Section: Other Imine-based Iron Complexesmentioning

confidence: 99%

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Non‐Heme Imine‐Based Iron Complexes as Catalysts for Oxidative Processes

2016

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Non-heme iron complexes are emerging as powerful and versatile catalysts in several oxidative transformations. Them ost investigated iron complex structures are based on aminopyridine ligands,b ut an umber of imine-based ligands have been also tested. In this review ac ollection of recent results obtained in oxidation catalysisw ith non-heme iminebased iron complexes is presented. Theirc atalytic performances in C À H, C=Ca nd À S À oxidation are spread over aw ide range of efficiency,g oing from very low to quite high.S uch performances are discussed, whenever possible,i nl ight of the operating reactionm echanismsa nd of catalyst stability.I n order to facilitate the discussion,a ni nitial survey of the most useful mechanistic tools widelya pplied to distinguish am etal-based oxidation from ar adicalchain process is also reported. Imine-basedc atalysts are divided into twoc lasses:( i) salen-Fec omplexes, and (ii)i mine-Fe complexes.I ns ome cases clues for free-radical oxidation mechanisms have been reported whilei no ther casese vidence for metal-based mechanisms has been collected. Thep referredm echanisticp athway is shown to be af unction of catalyst structure and features

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Section: Other Imine-based Iron Complexesmentioning

confidence: 99%

“…[81] According to the protocold eveloped by Beller et al, [82] trace amounts of the desired radical trap are added to the reaction mixture under catalytic conditions.T he solution is rapidly freezequenched at 77 Ka nd analyzed by EPR spectroscopy.…”

Section: Use Of Radical Trapsmentioning

confidence: 99%

Non‐Heme Imine‐Based Iron Complexes as Catalysts for Oxidative Processes

2016

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“…Of a selection of alkenes screened, the substrate with a 2-naphthyl group was oxidised in the highest ee -which could be raised to 97% through the use of 5 additional catalyst. In detailed follow-up studies, 66 a comparison of TsDPEN derivatives was made, and the effect of catalyst loading was studied; above 12 mol% ligand gave little improvement to the yield and a reduction in ee was observed. 10 Detailed mechanistic studies revealed that several iron complexes form within the mixture, several of which were identified by ESIMS.…”

Section: ) Oxidation Reactions Of Alkenesmentioning

confidence: 99%

Asymmetric catalysis using iron complexes – ‘Ruthenium Lite’?

Darwish

Wills

2012

Catal. Sci. Technol.

175

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“…This method afforded the correspongding epoxides in good to excellent yields. [22][23][24][25][26] Recently, they also reported a simpler system that uses imidazole derivatives, rather than dipicolinic acid and amines, 27,28) as ligands. However, the reactivity of this system was moderate, and the ligands which resulted in relatively high yields had to be synthesized ad hoc before use because of commercial inavailability.…”

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confidence: 99%

A Simple, Iron-Catalyzed, Pyridine-Assisted Hydrogen Peroxide Epoxidation System

Jiao

Matsunaga

Ishizuka

2011

CHEMICAL & PHARMACEUTICAL BULLETIN

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A simple and inexpensive system comprised of H 2 O 2 -pyridine-FeCl 3 · 6H 2 O for the catalysis of olefin epoxidation was established. Intriguingly, the reactivity of this system greatly depends on the amounts of pyridine. Various substrates, including aromatic and aliphatic olefins, were epoxidized by this simple system in moderate to excellent yields.Key words hydrogen peroxide; iron(III) chloride; olefin epoxidation; pyridine; acceleration Epoxides are highly desirable building blocks for the formation of fine chemicals, which are used in the production of pharmaceuticals, agricultural chemicals, industrial products or synthetic intermediates.1-3) Peracids are often used as oxidants. In particular, m-chloroperbenzoic acid (m-CPBA) has received considerable interest for use in the epoxidation of olefins to obtain the corresponding epoxides. [4][5][6] However, because of the cost, toxicity, and by-products of m-CPBA, a more cost-effective, harmless and clean oxidant is needed. Consequently, hydrogen peroxide has been extensively investigated as an alternative oxidant. Because hydrogen peroxide is safe and inexpensive, possesses a high oxygen content, and generates water as the only by-product, it is a viable candidate for use in epoxidation reactions. 7-10)Metal-catalyzed epoxidations with hydrogen peroxide results in outstanding yields.11-13) Nevertheless, although the superior metal catalysts like Re 14) or Pt 15,16) have excellent reactivity, the disadvantages of these metals cannot be ignored-namely, their high cost and quantitative insufficiency. Thus, our research focus has been on iron salts, which are relatively inexpensive compared with other transition metals, due to their natural abundance. Furthermore, iron salts have little risk to human health and are commercially available. [17][18][19][20][21] Beller and co-workers performed epoxidation of olefins in a reaction system comprised of FeCl 3 · 6H 2 O and H 2 O 2 , employing dipicolinic acid and an amine to activate the reaction. This method afforded the correspongding epoxides in good to excellent yields. [22][23][24][25][26] Recently, they also reported a simpler system that uses imidazole derivatives, rather than dipicolinic acid and amines, 27,28) as ligands. However, the reactivity of this system was moderate, and the ligands which resulted in relatively high yields had to be synthesized ad hoc before use because of commercial inavailability. Moreover its versatility regarding the use of different olefin substrates was limited. 27,28) We performed a more economical and practical H 2 O 2 -oxidized epoxidation of trans-stilbene 1 with a catalytic iron salt and a different ligand. This simple, FeCl 3 · 6H 2 O and pyridine combinative system catalyzed the reaction in excellent yield within only 30 min. In addition, this system was suitable for other substrates, such as aromatic and aliphatic olefins, both of which displayed good reactivity and excellent mass balance.At the onset of this work, a model catalytic epoxidation of trans-stilbene 1 was co...

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Biomimetic Iron‐Catalyzed Asymmetric Epoxidation of Aromatic Alkenes by Using Hydrogen Peroxide

Cited by 134 publications

References 51 publications

Non‐Heme Imine‐Based Iron Complexes as Catalysts for Oxidative Processes

Non‐Heme Imine‐Based Iron Complexes as Catalysts for Oxidative Processes

Asymmetric catalysis using iron complexes – ‘Ruthenium Lite’?

A Simple, Iron-Catalyzed, Pyridine-Assisted Hydrogen Peroxide Epoxidation System

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