- Ozonation of decalin as a model saturated cyclic molecule: A spectroscopic study
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Ozonolysis is used for oxidation of a model cyclic molecule-decalin, which may be consid-ered as an analog of saturated cyclic molecules present in heavy oil. The conversion of decalin exceeds 50% with the highest yield of formation of acids about 15–17%. Carboxylic acids, ketones/aldehydes, and alcohols are produced as intermediate products. The methods of UV-visible, transmission IR, at-tenuated total reflection IR-spectroscopy, NMR and mass-spectrometry were used to identify reaction products and unravel a possible reaction mechanism. The key stage of the process is undoubtedly the activation of the first C-H bond and the formation of peroxide radicals.
- Bykov, Gennadii L.,Ershov, Boris G.,Krasovskiy, Vladimir G.,Kustov, Alexander L.,Kustov, Leonid M.,Panich, Nadezhda M.
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- Alkane oxidation catalysed by a self-folded multi-iron complex
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A preorganised ligand scaffold is capable of coordinating multiple Fe(II) centres to form an electrophilic CH oxidation catalyst. This catalyst oxidises unactivated hydrocarbons including simple, linear alkanes under mild conditions in good yields with selectivity for the oxidation of secondary CH bonds. Control complexes containing a single metal centre are incapable of oxidising unstrained linear hydrocarbons, indicating that participation of multiple centres aids the CH oxidation of challenging substrates.
- Mettry, Magi,Moehlig, Melissa Padilla,Gill, Adam D.,Hooley, Richard J.
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p. 120 - 128
(2016/11/09)
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- Chemoselective hydroxylation of aliphatic sp3 C-H bonds using a ketone catalyst and aqueous H2O2
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The first ketone-catalyzed method for the oxidation of aliphatic C-H bonds is reported. The reaction conditions employ aryl trifluoromethyl ketones in catalytic amounts and hydrogen peroxide as the terminal oxidant. Hydroxylation is stereospecific and chemoselective for tertiary over secondary C-H bonds. A catalytic cycle invoking a dioxirane as the active oxidant is proposed.
- Pierce, Conor J.,Hilinski, Michael K.
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supporting information
p. 6504 - 6507
(2015/01/16)
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- Selective activation of secondary C-H bonds by an iron catalyst: Insights into possibilities created by the use of a carboxyl-containing bipyridine ligand
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In this work, we report the discovery of a carboxyl-containing iron catalyst 1 (FeII-DCBPY, DCBPY = 2,2′-bipyridine-4,4′- dicarboxylic acid), which could activate the C-H bonds of cycloalkanes with high secondary (2°) C-H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C-H bonds, 1 always preferred to oxidise the 2° C-H bonds to the corresponding ketone and alcohol products; the 2°/3° ratio ranged between 78/22 and >99/1 across 7 examples. 18O isotope labelling experiments, ESR experiments, a PPh3 method and the catalase method were used to characterize the reaction process during the oxidation. The success of 1 showed that, in addition to using a bulky catalyst, high 2° C-H bond selectivity could also be achieved using a less bulky molecular iron complex as the catalyst.
- Cheng, Shi,Li, Jing,Yu, Xiaoxiao,Chen, Chuncheng,Ji, Hongwei,Ma, Wanhong,Zhao, Jincai
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p. 3267 - 3273
(2013/10/01)
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- An iron catalyst for oxidation of alkyl C-H bonds showing enhanced selectivity for methylenic sites
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Many are called but few are chosen: A nonheme iron complex catalyzes the oxidation of alkyl C-H bonds by using H2O2 as the oxidant, showing an enhanced selectivity for secondary over tertiary C-H bonds (see scheme). Copyright
- Prat, Irene,Gomez, Laura,Canta, Merce,Ribas, Xavi,Costas, Miquel
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supporting information
p. 1908 - 1913
(2013/03/14)
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- Efficient stereo- and regioselective hydroxylation of alkanes catalysed by a bulky polyoxometalate
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Direct functionalization of alkanes by oxidation of C-H bonds to form alcohols under mild conditions is a challenge for synthetic chemistry. Most alkanes contain a large number of C-H bonds that present difficulties for selectivity, and the oxidants employed often result in overoxidation. Here we describe a divanadium-substituted phosphotungstate that catalyses the stereo- and regioselective hydroxylation of alkanes with hydrogen peroxide as the sole oxidant. Both cyclic and acyclic alkanes were oxidized to form alcohols with greater than 96% selectivity. The bulky polyoxometalate framework of the catalyst results in an unusual selectivity that can lead to the oxidation of secondary rather than the weaker tertiary C-H bonds. The catalyst also avoids wasteful decomposition of the stoichiometric oxidant, which can result in the production of hydroxyl radicals and lead to non-selective oxidation and overoxidation of the desired products.
- Kamata, Keigo,Yonehara, Kazuhiro,Nakagawa, Yoshinao,Uehara, Kazuhiro,Mizuno, Noritaka
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scheme or table
p. 478 - 483
(2010/09/17)
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- The selective functionalization of saturated hydrocarbons. Part 46. An investigation of Udenfriend's system under Gif conditions
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Under Gif conditions using ascorbic acid as reductant and oxygen as oxidant in pyridine, the selectivity for secondary hydrogen functionalization is exceptional. EDTA (ethylenediamine-tetra-acetic acid) is not needed as a ligand for iron.
- Barton, Derek H.R.,Delanghe, Nathalie C.
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p. 4471 - 4476
(2007/10/03)
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- Oxidation with the "O2 - H2O2 - Vauauium complex - Pyrazine-2-carboxylic acid" reagent 9. Oxidation of cyclohexene and decalin
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The oxidation of cyclohexene with hydrogen peroxide catalyzed by a vanadium complex and pyrazine-2-carboxylic acid (PCA) in air results in the formation of cyclohex-2-enyl hydroperoxide as the main product and cyclohex-2-enol, cyclohex-2-enone, cyclohex-3-enyl hydroperoxide, cyclohex-3-enol, cyclohexanol, cyclohexane, and 1,2-epoxycyclohexane in lesser amounts. The composition of the products of oxidation of decalin isomers with the system in question is similar to those obtained in the photochemical oxidation with hydrogen peroxide in air and in the oxidation with air in the presence of anthraquinone. A proposed mechanism for the oxidation includes the initiation by hydroxyl radicals generated from hydrogen peroxide under the action of the V - PCA system.
- Schuchardt,Guerreiro,Shul'pin
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p. 247 - 252
(2007/11/27)
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- Oxidations by Methyl(trifluoromethyl)dioxirane. 2. Oxyfunctionalization of Saturated Hydrocarbons
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The reaction of methyl(trifluoromethyl)dioxirane (1b), a novel dioxirane species, with two open-chain, four cyclic, and five polycyclic saturated hydrocarbons and two aralkyl hydrocarbons in CH2Cl2/1,1,1-trifluoropropanone has been studied; under mild conditions (-22 to 0 deg C), it gives alcohols and/or ketones (deriving from further oxidation of secondary alcohols) in high yields and within very short reaction times.Primary C-H bonds are not appreciably oxidized and high regioselectivities were determined for attack at tertiary over secondary C-H bonds, with theexception of norbornane, which showed opposite regioselectivity.The reaction is also highly stereoselective, since hydroxylations of cis- and trans-decalin and of cis- and trans-1,2-dimethylcyclohexane were found to be in each case stereospecific with retention.From kinetic data, Ea = 14.3 kcal mol-1 and log A = 9.9 were estimated for cyclohexane oxidation.Relative rates change in the order cyclohexane (0.78) octane (9.2) adamantane (146); cis-1,2-dimethylcyclohexane was observed to be 7-fold more reactive than its trans isomer, demonstrating remarkable discrimination for equatorial vs axial C-H attack (also noticed in the case of cis- and trans-decalin).The relative rate of oxidation of cumene vs ethylbenzene was found to be ca. 3.1 (after statistical correction), i.e., in sharp excess over values usually recorded in classical radical H-atom abstraction from benzylic position.Rate constants determined for the reactions of cumene and of ethylbenzene show the title dioxirane (1b) is more reactive than dimethyldioxirane (1a) by factors of ca. 600 and over 700, respectively.The whole of theobservations is better accommodated by an "oxenoid" mechanism, involving concerted O-atom insertion by dioxirane into C-H bonds of hydrocarbons.
- Mello, Rossella,Fiorentino, Michele,Fusco, Caterina,Curci, Ruggero
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p. 6749 - 6757
(2007/10/02)
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- FUNCTIONALISATION OF SATURATED HYDROCARBONS. Part X. A COMPARATIVE STUDY OF CHEMICAL AND ELECTROCHEMICAL PROCESSES (GIF AND GIF-ORSAY SYSTEMS) IN PYRIDINE, IN ACETONE AND IN PYRIDINE-CO-SOLVENT MIXTURES
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Six saturated hydrocarbons (cyclohexane, 3-ethylpentane, methylcyclopentane, cis- and trans-decalin and adamantane) were oxidised by the Gif system (iron catalyst, oxygen, zinc, carboxylic acid) and its electrochemical equivalent (Gif-Orsay system).Results obtained using various solvents (pyridine, acetone, pyridine-acetone mixtures) were similar for both systems.Total or partial replacement of pyridine with acetone affects the selectivity for secondary positions and lowers the ketone/secondary alcohol ratio.The formation of the same ratio of cis- and trans-decal-9-ol from both cis- and trans-decalin clearly demonstrates that tertiary alcohols result from a mechanism essentially radical in nature.
- Belavoine, Gilbert,Barton, Derek H. R.,Boivin, Jean,Gref, Aurore,Coupanec, Pascale Le,et al.
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p. 1091 - 1106
(2007/10/02)
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- Oxidation of trans-Decahydronaphthalene in Acetic Anhydride
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The oxidation of trans-decahydronaphthalene (1) was carried out in acetic anhydride with oxygen in the presence of Co(OAc)2, Ce(OAc)3, and NH4Br.Decahydronaphthyl acetates were obtained as main oxidation products in a selectivity of 81 molpercent at 120 degC.In addition, relative reactivities of hydrogen atoms of 1 were determined at temperatures from 90 to 120 degC.
- Yazu, Kaumasa,Wakabayashi, Takeshige,Nakayama, Tetsuo
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p. 1409 - 1412
(2007/10/02)
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- β-Fisson of 9-Decalinoxyl Radicals: Reversible Formation of 6-Ketocyclodecyl Radical
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Rearrangement at 0 deg C of trans-9-decalinyl hypobromide (1trans, X=Br), formed by interaction of 1trans (X=H) with bromine and silver acetate or mercuric oxide, gives 6-bromocyclodecanone(4, X=Br) whereas the same reaction at 81 deg C gives 2-(4-bromobutyl)cyclohexanone (6, X=Br).The cis isomer (1cis, X=Br) behaves similarly.The relative yields of the nitroso dimers, 11, 12, and 13, formed by photolysis of 1cis (X=NO) and 1trans (X=NO), also depend on the reaction temperature.Reduction of 6-bromocyclodecanone (4, X=Br) with tribytylstannane in high concentration gives mainly cis- and trans-9-decalinol, with the former predominating.These results indicate (i) that 9,10-bond fisson of the 9-decalinoxyl radicals, 2cis and 2trans, is rapid but reversible, (ii) that 1,9-bond fisson of 2cis and 2trans is relatively slow and is essentially irreversible under the conditions used here, and (iii) that ring closure of the radical (5) favors formation of the cis product (2cis).
- Beckwith, Athelstan L.J.,Kazlauskas, Rymantas,Syner-Lyons, Mark R.
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p. 4718 - 4722
(2007/10/02)
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- Aliphatic Hydroxylation Catalyzed by Iron Porphyrin Complexes
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The hydroxylation of unactivated alkanes has been observed in a catalytic system containing iodosylbenzene and various iron porphyrins.The yields and distributions of products have been found to be sensitive to the peripheral substitution pattern of the porphyrin.The oxidation of cyclohexane with chloro(5,10,15,20-tetra-o-tolylporphyrinato)iron(III) gave a 31percent yield of cyclohexanol and 6percent cyclohexanone based on iodosylbenzene.Two samples of Fe(TTP)ClCl with differing atropisomeric composition gave different product ratios.The hydroxylation of cycloheptane under these conditions and in the presence of bromotrichloromethane gave 24percent cycloheptanol and 18percent bromocycloheptane.Steric selectivity was observed by comparing the hydroxylation of cis-decalin with Fe(TPP)Cl, Fe(TTP)Cl, Fe(TNP)Cl, and Fe(TMP)Cl.The hydrogen-isotope effect for cyclohexane hydroxylation by Fe(TTP)Cl was found to be 12.9+/- 1.A mechanism for hydroxylation is proposed on the basis of these results that involves initial oxidation of the iron porphyrin, hydrogen atom abstraction from the alkane, and rapid collapse of this radical to give the product alcohol and to regenerate the iron(III) catalyst.
- Groves, John T.,Nemo, Thomas E.
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p. 6243 - 6248
(2007/10/02)
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- VANADIUM(V) PEROXO COMPLEXES. NEW VERSATILE BIOMIMETIC REAGENTS FOR EXPOXIDATION OF OLEFINS AND HYDROXYLATION OF ALKANES AND AROMATIC HYDROCARBONS.
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Novel covalent vandium(V) oxo peroxo complexes of general formula VO(O//2)(O-N)LL prime and anionic complexes with the general formula left bracket VO(O//2)(Pic)//2 right bracket ** minus A** plus L were synthesized and characterized by physicochemical methods and X-ray crystallography. The crystal structure of VO(O//2)(Pic) multiplied by (times) 2H//2O (Ia) revealed a pentagonal-bipyramidal environment, with a significant hydrogen bonding between the peroxo moiety and the equatorial water molecule. Protonated type II complexes (A** plus equals H** plus ) are dissociated in an aqueous solution and have an acidic nature (pK//a equals 1. 8) but are undissociated in a nonprotic solution, with a presumably peracid-like oxohydroperoxo structure. It is shown that vanadium peroxo complexes are effective oxidants in nonprotic solvents under mild conditions. They transform olefins to epoxides and cleavage products in a nonsteoroselective fashion (cis-2-butene gave a mixture of cis and trans epoxides). More interestingly, they hydroxylate aromatic hydrocarbons to phenols and alkanes to alcohols and ketones.
- Mimoun,Saussine,Daire,Postel,Fischer,Weiss
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p. 3101 - 3110
(2007/12/18)
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- Model Systems for Cytochrome P450 Dependent Mono-oxygenases. Part 3. The Stereochemistry of Hydroxylation of cis- and trans-Decahydronaphthalene by Chemical Models for Cytochrome P450 Dependent Mono-oxygenases
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The stereochemistry of hydroxylation of the tertiary C-H bonds of cis- and trans-decahydronaphthalene by seven chemical models for cytochrome P450 dependent mono-oxygenases has been studied.Oxidations by three of the model systems (H2O2-Fe2+-CH3CN, O2-Fe2+-2-mercaptobenzoic acid, and diazofluorene-hν-O2) are non-stereospecific giving the same ratio of cis- to trans-decahydronaphthalen-9-ol from each substrate.However, hydroxylations with pyridine N-oxide-hν show a partial retention of configuration and with trifluoroperacetic acid or with iron(III) porphyrins and iodosylbenzene the oxidations are >97percent stereospecific.The mechanism of these hydroxylations and their usefulness as models for the cytochrome P450 dependent mono-oxygenases are discussed.
- Smith, John R. Lindsay,Sleath, Paul R.
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p. 1165 - 1170
(2007/10/02)
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