585-08-0Relevant articles and documents
The catalytic function of a silica gel-immobilized Mn(II)-hydrazide complex for alkene epoxidation with H2O2
Ghorbanloo, Massomeh,Monfared, Hassan Hosseini,Janiak, Christoph
experimental part, p. 12 - 20 (2011/10/05)
An efficient and highly selective heterogeneous catalyst was developed by immobilization of a manganese complex on an inorganic support to yield (silica gel)-O2(EtO)Si-L1-Mn(HL2) [(L1) - modified salicylaldiminato and H2L2(E)- N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide]. Mn(II) has been anchored on the surface of functionalized silica by means of N,O-coordination to the covalently Si-O bound modified salicylaldiminato Schiff base ligand. The prepared material (silica gel)-O2(EtO)Si-L1-Mn(HL 2), was characterized by elemental and thermogravimetric analyses (TGA and DTA), UV-vis and FT-IR spectroscopy. This new material is demonstrated to be a very active catalyst in clean epoxidation reactions using a combined oxidant of aqueous hydrogen peroxide and actonitrile in the presence of aqueous sodium hydrogencarbonate. The effects of reaction parameters such as solvent, NaHCO3 and oxidant in the epoxidation of cis-cyclooctene were investigated. Cycloalkenes were oxidized efficiently to their corresponding epoxide with 87-100% selectivity in the presence of this catalyst. This catalytic system showed also good activities in the epoxidation of linear alkenes. The obtained results show that this catalyst is a robust and stable heterogeneous catalyst which can be recovered quantitatively by simple filtration and reused multiple times without loss of its activity.
Manganese catalysts for C-H activation: An experimental/theoretical study identifies the stereoelectronic factor that controls the switch between hydroxylation and desaturation pathways
Hull, Jonathan F.,Balcells, David,Sauer, Effiette L.O.,Raynaud, Christophe,Brudvig, Gary W.,Crabtree, Robert H.,Eisenstein, Odile
experimental part, p. 7605 - 7616 (2010/07/08)
We describe competitive C-H bond activation chemistry of two types, desaturation and hydroxylation, using synthetic manganese catalysts with several substrates. 9,10-Dihydrophenanthrene (DHP) gives the highest desaturation activity, the final products being phenanthrene (P1) and phenanthrene 9,10-oxide (P3), the latter being thought to arise from epoxidation of some of the phenanthrene. The hydroxylase pathway also occurs as suggested by the presence of the dione product, phenanthrene-9,10-dione (P2), thought to arise from further oxidation of hydroxylation intermediate 9-hydroxy-9,10- dihydrophenanthrene. The experimental work together with the density functional theory (DFT) calculations shows that the postulated Mn oxo active species, [Mn(O)(tpp)(Cl)] (tpp = tetraphenylporphyrin), can promote the oxidation of dihydrophenanthrene by either desaturation or hydroxylation pathways. The calculations show that these two competing reactions have a common initial step, radical H abstraction from one of the DHP sp3 C-H bonds. The resulting Mn hydroxo intermediate is capable of promoting not only OH rebound (hydroxylation) but also a second H abstraction adjacent to the first (desaturation). Like the active MnV=O species, this Mn IV-OH species also has radical character on oxygen and can thus give H abstraction. Both steps have very low and therefore very similar energy barriers, leading to a product mixture. Since the radical character of the catalyst is located on the oxygen p orbital perpendicular to the Mn IV-OH plane, the orientation of the organic radical with respect to this plane determines which reaction, desaturation or hydroxylation, will occur. Stereoelectronic factors such as the rotational orientation of the OH group in the enzyme active site are thus likely to constitute the switch between hydroxylase and desaturase behavior.
Stabilities and partitioning of arenonium ions in aqueous media
Lawlor, D. A.,O'Ferrall, R. A. More,Rao, S. N.
experimental part, p. 17997 - 18007 (2009/06/25)
The phenathrenonium ion is formed as a reactive intermediate in the solvolysis of 9-dichloro-acetoxy-9,10-dihydrophenanthrene in aqueous acetonitrile and undergoes competing reactions with water acting as a base and nucleophile. Measurements of product ratios in the presence of azide ion as a trap and 'clock' yield rate constants kp ) 3.7 × 10 10 and kH2O ) 1.5 × 108 s-1, respectively. Combining these with rate constants for the reverse reactions (protonation of phenanthrene and acid-catalyzed aromatization of its water adduct) gives equilibrium constants pKa ) -20.9 and pKR ) -11.6. For a series of arenonium and benzylic cations, correlation of log kp with pK a, taking account of the limit to kp set by the relaxation of water (1011 s-1), leads to extrapolation of k p ) 9.0 × 1010 s-1 and pKa ) -24.5 for the benzenonium ion and kp ) 6.5 × 1010 s-1 and pKa ) -22.5 for the 1-naphthalenonium ion. Combining these pKa's with estimates of equilibrium constants pK H2O for the hydration of benzene and naphthalene, and the relationship pKR ) pKa + pKH2O based on Hess's law, gives pKR ) -2.3 and -8.0 respectively, and highlights the inherent stability of the benzenonium ion. A correlation exists between the partitioning ratio, kp/kH2O, for carbocations reacting in water and KH2O the equilibrium constant between the respective reaction products, i.e., log(kp/kH2O) ) 0.46pK H2O - 3.7. It implies that kp exceeds kH2O only when KH2O > 108. This is consistent with the proton transfer (a) possessing a lower intrinsic reactivity than reaction of the carbocation with water as a nucleophile and (b) being rate-determining in the hydration of alkenes (and dehydration of alcohols) except when the double bond of the alkene is unusually stabilized, as in the case of aromatic molecules.
An efficient approach for aromatic epoxidation using hydrogen peroxide and Mn(III) porphyrins
Rebelo, Susana L. H.,Simoes, Mario M. Q.,Neves, M. Graca P. M. S.,Silva, Artur M. S.,Cavaleiro, Jose A. S.
, p. 608 - 609 (2007/10/03)
Efficient epoxidation, in very high conversions and selectivities, of aromatic hydrocarbons with hydrogen peroxide, in the presence of Mn III porphyrins [Mn(TDCPP)Cl, Mn(βNO2TDCPP)Cl, Mn(TPFPP)Cl] as catalysts is described; naphthalene and anthracene afford the anti-1,2:3,4-arene dioxides whereas with phenanthrene the 9,10-oxide is obtained.
Efficient electrophilic and nucleophilic epoxidations utilizing a sulfonylperoxy radical and peroxysulfate species
Park, Min Young,Yang, Seung Gak,Kim, Yong Hae
, p. 431 - 436 (2007/10/03)
Reaction of superoxide anion radical (O2-. with o-nitrobenzenesulfonyl chloride yields a o-nitrobenzenesulfonyl peroxy radical with strong oxidizing ability, which is capable of oxidizing aryl methylene moieties to aryl ketones and relatively electron-rich alkenes regioselectively to epoxides. The oxidizing species is tentatively attributed to the o-nitrobenzenesulfonyl peroxy radical of structure 1. Tetrabutylammonium peroxydisulfate (TBA)2S2O8, 2) was prepared by the reaction of tetrabutylammonium hydrogen sulfate with potassium peroxydisulfate. The epoxidation of enals and enones, such as α,β-unsaturated aldehydes or ketones, was efficiently achieved with 2 in the presence of hydrogen peroxide and base in acetonitrile or in methanol at 25°C. A base-sensitive substrate, such as cinnamaldehyde, could be successfully epoxidized under mild reaction conditions and in short reaction time.
Epoxidation of polyaromatics using HOF·CH3CN
Rozen, Shlomo,Bareket, Yifat,Blum, Jochanan
, p. 2333 - 2334 (2007/10/03)
The reaction of the HOF·CH3CN complex, made directly by passing fluorine through aqueous acetonitrile, with some phenanthrene and pyrene derivatives results in fast epoxidation.
Novel (α,β-Epoxyalkyl)lithium Reagents via the Lithiation of Organyl-Substituted Epoxides
Eisch, John J.,Galle, James E.
, p. 4835 - 4840 (2007/10/02)
A series of epoxides bearing unsaturated organyl groups attached directly to the epoxy group was found to have sufficient kinetic acidity to undergo clean lithiation at low temperatures.Epoxides of the type is aryl, vinylic, acetylenic, alkoxycarbonyl, or cyano, were smoothly converted into by either t-BuLi or LDA in the temperature range of -80 to -115 deg C.The resulting (α,β-epoxyalkyl)lithium reagents could be transformed into a variety of substituted epoxides, such as R2C-CE(Un)-O, where E = D, R3Si, R3Sn, R, RCO, CO2H, or COH(R)2.In cases where Un is acyl, addition to the carbonyl, rather than lithiation, occurred preferentially.Attempted lithiations of aziridines and thiiranes led to extrusion of nitrogen and sulfur, respectively.Even the relatively stable intermediates generated at -90 deg C underwent carbenoid-like decomposition at higher temperatures to yield isomerization and intermolecular-insertion products.Observation of these processes gives direct corroboration of reaction mechanisms proposed for the base-promoted isomerizations of epoxides.
BIOMIMETIC HYDROXYLATION OF AROMATIC COMPOUNDS: HYDROGEN PEROXIDE AND MANGANESE-POLYHALOGENATED PORPHYRINS AS A PARTICULARLY GOOD SYSTEM.
Carrier, Marie-Noelle,Scheer, Corinne,Gouvine, Pascal,Bartoli, Jean-Francois,Battioni, Pierrette,Mansuy, Daniel
, p. 6645 - 6648 (2007/10/02)
Various iron- and manganese-porphyrins were compared as catalysts for the hydroxylation of anisole by H2O2 or PhIO.Whereas all the iron-porphyrins tested gave low hydroxylation yields, Mn(III)-meso-tetraarylporphyrins bearing halogen substituents on their meso-aryl and pyrrole groups gave good yields (up to 70percent based on the oxidant) for the para-hydroxylation of anisole, especially with H2O2 as oxidant in the presence of imidazole.Under these conditions, phenanthrene was quantitatively oxidized into its 9,10-epoxide and naphthalene was mainly oxidized into 1-naphthol (40percent yield).Hydroxylation yields appeared dependent upon the reactivity of the oxidizing system not only toward the starting aromatic compound but also toward the phenol products.
Oxidations by methyl(trifluoromethyl)dioxirane. 4.1 Oxyfunctionalization of aromatic hydrocarbons
Mello, Rossella,Ciminale, Francesco,Fiorentino, Michele,Fusco, Caterina,Prencipe, Teresa,Curci, Ruggero
, p. 6097 - 6100 (2007/10/02)
By using the title dioxirane (1a), naphthalene (2), phenanthrene (3), and anthracene (4) have been converted into anti-naphthalene-1,2;3,4-dioxide (2′), phenonthrene-9,10-oxide (3′), and anthraquinone (4′), respectively, in high yield and under mild conditions. However, the transformation of pyrene (5) - an higher homologue of the polycyclic aromatic hydrocarbon series - into the corresponding arene oxide was found to proceed much less effectively.
Direct Oxidation of Arenes to Arene Oxides by 2-Nitrobenzene Peroxysulfur Intermediate Generated from 2-Nitrobenzenesulfonyl Chloride and Superoxide
LEE, Hyeon Kye,KIM, Kyoung Soo,KIM, Jack C.,KIM, Yong Hae
, p. 561 - 564 (2007/10/02)
Acenaphthylene, phenanthrene, and pyrene, which are inert with superoxide itself, were readily oxidized to the corresponding arene oxides by a 2-nitrobenzene sulfonyl-peroxyl radical intermediate (A) generated from 2-nitrobenzenesulfonyl chloride and potassium superoxide in polar aprotic solvents such as acetonitrile, nitromethane, and dimethylformamide under mild conditions.
