- Enantioselective manganese-porphyrin-catalyzed epoxidation and C-H hydroxylation with hydrogen peroxide in water/methanol solutions
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The asymmetric epoxidation of alkene and hydroxylation of arylalkane derivatives by H2O2 to give optically active epoxides (enantiomeric excess (ee) up to 68%) and alcohols (ee up to 57%), respectively, were carried out in water/methanol solutions using chiral water-soluble manganese porphyrins as catalysts.
- Srour, Hassan,Maux, Paul Le,Simonneaux, Gerard
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experimental part
p. 5850 - 5856
(2012/07/14)
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- Enantioselective water-soluble iron-porphyrin-catalyzed epoxidation with aqueous hydrogen peroxide and hydroxylation with iodobenzene diacetate
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The asymmetric epoxidation of styrene derivatives by H2O 2 (or UHP) to give optically active epoxides (ee up to 81%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 78%) were carried out in methanol and water using chiral water-soluble iron porphyrins as catalysts.
- Maux, Paul Le,Srour, Hassan F.,Simonneaux, Gérard
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experimental part
p. 5824 - 5828
(2012/09/11)
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- A non-heme iron(III) complex with porphyrin-like properties that catalyzes asymmetric epoxidation
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In this report, we describe an iron(III) complex containing a carbazole-based tridentate ligand that catalyzes highly enantioselective asymmetric epoxidation of (E)-alkenes at room temperature. The non-heme iron(III) complex has a five-coordinated trigonal-bipyramidal structure, and its two-electron oxidized state has the similar electronic structure as that of iron porphyrins.
- Niwa, Takashi,Nakada, Masahisa
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supporting information; experimental part
p. 13538 - 13541
(2012/10/08)
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- Mass-spectrometric and kinetic studies on the mechanism and degradation pathways of titanium salalen catalysts for asymmetric epoxidation with aqueous hydrogen peroxide
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The composition and degradation of a highly active and enantioselective titanium salalen in situ catalyst for the asymmetric epoxidation of olefins with aqueous hydrogen peroxide was investigated. Kinetic data and ESI-MS studies point to a mononuclear tit
- Berkessel, Albrecht,Brandenburg, Marc,Schaefera, Mathias
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supporting information; experimental part
p. 1287 - 1294
(2009/06/17)
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- Catalase and epoxidation activity of manganese salen complexes bearing two xanthene scaffolds
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A series of manganese Hangman salen ligand platforms functionalized by tert-butyl groups in the 3 and 3′ positions using the Suzuki cross-coupling methodology are presented. The Hangman platforms support multielectron chemistry mediated by proton-coupled
- Yang, Jenny Y.,Nocera, Daniel G.
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p. 8192 - 8198
(2008/02/11)
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- Control of epoxidation enantioselectivity by axial ligation in manganese chiroporphyrins with diastereotopic faces
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A manganese(III) chiroporphyrin with alternate pentafluorophenyl and chiral cyclopropyl meso-substituents in the αFαF conformation has been shown by X-ray crystallography to have its chloro axial ligand predominantly on the non-chiral β face. Epoxidation of 1,2-dihydronaphthalene by iodosylbenzene induced by the neat catalyst in dichloromethane solution shows a twofold increase in enantioselectivity relative to the same reaction in the presence of pyridine. These observations suggest that the location of the chloro ligand on the β face can block that face from participating in catalytic epoxidation, and direct the reaction to take place on the chiral a face. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Liu, Shu-Qing,Pecaut, Jacques,Marchon, Jean-Claude
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p. 1823 - 1826
(2007/10/03)
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- A New Synthetic Route to Non-K and Bay Region Arene Oxide Metabolites From cis-Diols
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Arene oxides of naphthalene, quinoline, tripphenylene, benzoppyrene, and dibenzanthracene have been synthesised in enantiopure (1a-c) or racemic form (1d-f), free from oxepine isomers (3d-f) from cis-diol precursors (7a-f) via chloroacetate (9a-f) or dimesylate (13a) intermediates.
- Boyd, Derek R.,Sharma, Narain D.,Agarwal, Rajiv,Kerley, Nuala A.,McMordie, R. Austin S.,et al.
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p. 1693 - 1694
(2007/10/02)
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- Nonempirical Confirmations of the Absolute Configuration of (+)-α-Methoxy-α-(trifluoromethyl)phenylacetic Acid
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The absolute configuration of the widely used chiral derivatizing agent α-methoxy-α-(trifluoromethyl)phenylacetic (MTPA) acid has been unambiguously determined through the use of two independent, nonempirical methods as R and S for the (+)- and (-)-enanti
- Oh, Soonsin S.,Butler, William M.,Koreeda, Masato
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p. 4499 - 4503
(2007/10/02)
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- A General Method for the Resolution of Cyclic trans-Bromohydrin Enantiomers. Absolute Configuration by Crystal Structure Analysis of a 2-Methoxy-2-phenyl-2-trifluoromethylacetate (MTPA) Diastereoisomer
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trans-Bromohydrins of 1,2,3,4-tetrahydronaphthalene (1a), 1,2,3,4-tetrahydroanthracene (1b), and 1,2,3,4-tetrahydrophenanthrene (1c) and (1d) were isolated in optically pure forms by reductive cleavage of the corresponding 2-methoxy-2-phenyl-2-trifluoromethylacetate (MTPA) diastereoisomers (2a-d) which had been separated by preparative h.p.l.c.Using reactions with established mechanisms and stereochemistry, the configurations at the chiral centres in the bromohydrins (1) were correlated with those in the tetrahydroepoxides (5), the arene oxides (7), and cis- (3) and trans- (4) tetrahydrodiols.An X-ray structure analysis of the 1,2,3,4-tetrahydroanthracene bromo-MTPA ester (+)-(2bE) indicated the trans equatorial quasi-equatorial conformation and confirmed the absolute stereochemistry of the MTPA group as (S).
- Balani, Suresh K.,Boyd, Derek R.,Cassidy, E. Sally,Devine, Gregory I.,Malone, John F.,et al.
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p. 2751 - 2756
(2007/10/02)
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- AN IMPROVED METHOD FOR THE SYNTHESIS OF OPTICALLY PURE EPOXIDE AND ALCOHOL DERIVATIVES OF CHIRAL BROMOHYDRINS
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The resolution of arene oxides, diols and other derivatives of bromohydrins has been markedly improved by the use of bromohydrin esters of (-)-(S)-α-methoxy-α-trifluoromethyl-phenylacetic acid (MTPA).
- Balani, Suresh K.,Boyd, Derek R.,Cassidy, E. Sally,Greene, Ruth M. E.,McCombe, Kenneth M.,et. al.
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p. 3277 - 3280
(2007/10/02)
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- Stereochemical and Mechanistic Aspects of Sulphoxide, Epoxide, Arene Oxide, and Phenol Formation by Photochemical Oxygen Atom Transfer from Aza-aromatic N-Oxides
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Stereoselectivity and relative yields are determined for the sulphoxide formation resulting from the u.v. irradiation of a range of aza-aromatic N-oxides in the presence of cyclic thioethers.A comparison is made with the results of oxidation by oxaziridines and by mono-oxygenase enzymes present in the fungus Aspergillus niger.The photochemical oxidation results are consistent with a transition state involving an oxaziridine intermediate where partial bonding of the oxygen atom to the ring nitrogen atom is maintained during the oxygen transfer process.Photolysis of aza-aromatic N-oxides in the presence of cis- and trans-olefins yields epoxides. cis-4-Methylpent-2-ene yielded both cis and trans-epoxides in almost equal proportions indicating that the oxygen atom addition to a carbon-carbon bond in this system is non-concerted.The photochemically induced oxygenation of perdeuteriated aromatic substrates provides no evidence for direct insertion of an oxygen atom into an aromatic carbon-hydrogen bond.Addition of an oxygen atom to form an epoxide (arene oxide) intermediate in this system is evidenced by the NIH shift in a wide range of aromatic substrates, and by the detection of arene oxide intermediates (and their isomeric phenols) from naphthalene and phenanthrene.
- Akhtar, M. Naseem,Boyd, Derek R.,Neill, John D.,Jerina, Donald M.
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p. 1693 - 1699
(2007/10/02)
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