- Oxidant-free dehydrogenation of alcohols heterogeneously catalyzed by cooperation of silver clusters and acid-base sites on alumina
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A γ-alumina-supported silver cluster catalyst - Ag/Al 2O3-has been shown to act as an efficient heterogeneous catalyst for oxidant-free alcohol dehydrogenation to carbonyl compounds at 373 K. The catalyst shows higher activity than conventional heterogeneous catalysts based on platinum group metals (PGMs) and can be recycled. A systematic study on the influence of the particle size and oxidation state of silver species, combined with characterization by Ag K-edge XAFS (X-ray absorption fine structure) has established that silver clusters of sizes below 1 nm are responsible for the higher specific rate. The reaction mechanism has been investigated by kinetic studies (Hammett correlation, kinetic isotope effect) and by in situ FTIR (kinetic isotope effect for hydride elimination reaction from surface alkoxide species), and the following mechanism is proposed: 1) reaction between the alcohol and a basic OH group on the alumina to yield alkoxide on alumina and an adsorbed water molecule, 2) CH activation of the alkoxide species by the silver cluster to form a silver hydride species and a carbonyl compound, and 3) H2 desorption promoted by an acid site in the alumina. The proposed mechanism provides fundamental reasons for the higher activities of silver clusters on acid-base bifunctional support (Al 2O3) than on basic (MgO and CeO2) and acidic to neutral (SiO2) ones. This example demonstrates that catalysts analogous to those based on of platinum group metals can be designed with use of a less expensive d10 element - silver - through optimization of metal particle size and the acid-base natures of inorganic supports.
- Shimizu, Ken-Ichi,Sugino, Kenji,Sawabe, Kyoichi,Satsuma, Atsushi
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- Highly selective, economical and efficient oxidation of alcohols to aldehydes and ketones by air and sunlight or visible light in the presence of porphyrins sensitizers
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In this work, a new aerobic route is introduced for the selective oxidation of a variety of aromatic and aliphatic alcohols to the corresponding aldehyde and ketone derivatives by molecular oxygen in the presence of free base porphyrins and metalloporphyrins as sensitizers using white light or sunlight in an organic solvent. The method shows a wide scope, exhibits chemoselectivity and proceeds under mild reaction conditions. The resulting products are obtained in good conversions in a reasonable time. The Royal Society of Chemistry.
- Hajimohammadi, Mahdi,Safari, Nasser,Mofakham, Hamid,Deyhimi, Farzad
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- 1-Alkenylcycloalkoxy Radical Chemistry. A Two-Carbon Ring Expansion Methodology
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The exploitation of alkoxy radicals derived from 1-ethenylcycloalkanols for use in a two-carbon ring expansion protocol was proposed.Direct one-pot alkoxy radical-mediated fragmentation-cyclization was not feasible since the reactive intermediate was quenched by iodine in the reaction mixture.However, via the use of iodo epoxides 3, the tandem fragmentation-cyclization sequence could be accomplished.This afforded ring-expanded products via an endo mode of cyclization, although in one example product from an exo mode of cyclization was also isolated.This methodologywas shown to be valid for large ring compounds as well.The intermediary of iodo epoxides 3 also afforded improved yields as compared to the direct cyclization of iodo enones 4.These results are the first examples of radical cyclization to medium-sized carbocycles.
- Galatsis, Paul,Millan, Scott D.,Faber, Tim
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- Concerning the Mechanism of 'Gif' Oxidations of Cycloalkanes
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The oxygen atom of cyclodecanone, formed by oxidation of cyclodecane using FeCl3-H2O2 in pyridine-acetic acid, is largely derived from molecular oxygen: taken in conjunction with results of radical-trapping experiments, this supports a free-radical mechanism for the hydrocarbon activation.
- Knight, Candice,Perkins, M. John
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Read Online
- Reactions of OH radicals with C6 - C10 cycloalkanes in the presence of NO: Isomerization of C7 - C10 cycloalkoxy radicals
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Rate constants have been measured for the reactions of OH radicals with a series of C6 - C10 cycloalkanes and cycloketones at 298 ± 2 K, by a relative rate technique. The measured rate constants (in units of 10-12 cm3 molecule-1s-1) were cycloheptane, 11.0 ± 0.4; cyclooctane, 13.5 ± 0.4; cyclodecane, 15.9 ± 0.5; cyclohexanone, 5.35 ± 0.10; cycloheptanone, 9.57 ± 0.41; cyclooctanone, 15.4 ± 0.7; and cyclodecanone, 20.4 ± 0.8, where the indicated errors are two least-squares standard deviations and do not include uncertainties in the rate constant for the reference compound n-octane. Formation yields of cycloheptanone from cycloheptane (4.2 ± 0.4%), cyclooctanone from cyclooctane (0.85 ± 0.2%), and cyclodecanone from cyclodecane (4.9 ± 0.5%) were also determined by gas chromatography, where the molar yields are in parentheses. Analyses of products by direct air sampling atmospheric pressure ionization mass spectrometry and by combined gas chromatography - mass spectrometry showed, in addition to the cycloketones, the presence of cycloalkyl nitrates, cyclic hydroxyketones, hydroxydicarbonyls, hydroxycarbonyl nitrates, and products attributed to carbonyl nitrates and/or cyclic hydroxynitrates. The observed formation of cyclic hydroxyketones from the cycloheptane, cyclooctane and cyclodecane reactions, with estimated molar yields of 46%, 28%, and 15%, respectively, indicates the occurrence of cycloalkoxy radical isomerization. Potential reaction mechanisms are presented, and rate constants for the various alkoxy radical reactions are derived. (Figure presented)
- Aschmann, Sara M.,Arey, Janet,Atkinson, Roger
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Read Online
- Complementary and selective oxidation of hydrocarbon derivatives by two cytochrome P450 enzymes of the same family
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The cytochrome P450 enzymes CYP101B1 and CYP101C1, which are from the bacterium Novosphingobium aromaticivorans DSM12444, can hydroxylate norisoprenoids with high activity and selectivity. With the goal of expanding and establishing their substrate range with a view to developing applications, the oxidation of a selection of cyclic alkanes, ketones and alcohols was investigated. Cycloalkanes were oxidised, but both enzymes displayed moderate binding affinity and low levels of productive activity. We improved the binding and activity of these substrates with CYP101B1 by making the active site more hydrophobic by switching a histidine residue to a phenylalanine (H85F). The presence of a ketone moiety in the cycloalkane skeleton significantly improved the oxidation activity with both enzymes. CYP101C1 preferably catalysed the oxidation of cycloalkanones at the C-2 position whereas CYP101B1 oxidised these substrates with higher productivity and at positions remote from the carbonyl group. This demonstrates that the binding orientation of the cyclic ketones in the active site of each enzyme must be different. Linear ketones were also oxidised by both enzymes but with lower activity and selectivity. Cyclic substrates with an ester directing group were more efficiently oxidised by CYP101B1 than CYP101C1. Both enzymes catalysed oxidation of these esters with high regioselectively on the ring system remote from the ester directing group. CYP101C1 selectively oxidised certain terpenoid ester substrates, such as α-terpinyl and citronellyl acetate more effectively than CYP101B1. Overall, we establish that the high selectivity and activity of these enzymes could provide new biocatalytic routes to important fine chemicals.
- Sarkar, Md. Raihan,Bell, Stephen G.
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p. 5983 - 5995
(2020/10/08)
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- Ruthenium Trichloride Catalyst in Water: Ru Colloids versus Ru Dimer Characterization Investigations
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An easy-to-prepare ruthenium catalyst obtained from ruthenium(III) trichloride in water demonstrates efficient performances in the oxidation of several cycloalkanes with high selectivity toward the ketone. In this work, several physicochemical techniques were used to demonstrate the real nature of the ruthenium salt still unknown in water and to define the active species for this Csp3-H bond functionalization. From transmission electron microscopy analyses corroborated by SAXS analyses, spherical nanoobjects were observed with an average diameter of 1.75 nm, thus being in favor of the formation of reduced species. However, further investigations, based on X-ray scattering and absorption analyses, showed no evidence of the presence of a metallic Ru-Ru bond, proof of zerovalent nanoparticles, but the existence of Ru-O and Ru-Cl bonds, and thus the formation of a water-soluble complex. The EXAFS (extended X-ray absorption fine structure) spectra revealed the presence of an oxygen-bridged diruthenium complex [Ru(OH)xCl3-x]2(μ-O) with a high oxidation state in agreement with catalytic results. This study constitutes a significant advance to determine the true nature of the RuCl3·3H2O salt in water and proves once again the invasive nature of the electron beam in microscopy experiments, routinely used in nanochemistry.
- Lebedeva, Anastasia,Albuquerque, Brunno L.,Domingos, Josiel B.,Lamonier, Jean-Fran?ois,Giraudon, Jean-Marc,Lecante, Pierre,Denicourt-Nowicki, Audrey,Roucoux, Alain
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p. 4141 - 4151
(2019/03/26)
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- Selective biocatalytic hydroxylation of unactivated methylene C-H bonds in cyclic alkyl substrates
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The cytochrome P450 monooxygenase CYP101B1 from Novosphingobium aromaticivorans selectively hydroxylated methylene C-H bonds in cycloalkyl rings. Cycloketones and cycloalkyl esters containing C6, C8, C10 and C12 rings were oxidised with high selectively on the opposite side of the ring to the carbonyl substituent. Cyclodecanone was oxidised to oxabicycloundecanol derivatives in equilibrium with the hydroxycyclodecanones.
- Sarkar, Md Raihan,Dasgupta, Samrat,Pyke, Simon M.,Bell, Stephen G.
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supporting information
p. 5029 - 5032
(2019/05/21)
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- Cp? versus Bis-carbonyl iridium precursors as CH oxidation precatalysts
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We previously reported a dimeric IrIV-oxo species as the active water oxidation catalyst formed from a Cp?Ir(pyalc)Cl {pyalc = 2-(2′-pyridyl)-2-propanoate} precursor, where the Cp? is lost to oxidative degradation during catalyst activation; this system can also oxidize unactivated CH bonds. We now show that the same Cp?Ir(pyalc)Cl precursor leads to two distinct active catalysts for CH oxidation. In the presence of external CH substrate, the Cp? remains ligated to the Ir center during catalysis; the active species-likely a highvalent Cp?Ir(pyalc) species-will oxidize the substrate instead of its own Cp?. If there is no external CH substrate in the reaction mixture, the Cp? will be oxidized and lost, and the active species is then an iridium-μ-oxo dimer. Additionally, the recently reported Ir(CO)2(pyalc) water oxidation precatalyst is now found to be an efficient, stereoretentive CH oxidation precursor. We compare the reactivity of Ir(CO)2(pyalc) and Cp?Ir(pyalc)Cl precursors and show that both can lose their placeholder ligands, CO or Cp?, to form substantially similar dimeric IrIV-oxo catalyst resting states. The more efficient activation of the bis-carbonyl precursor makes it less inhibited by obligatory byproducts formed from Cp? degradation, and therefore the dicarbonyl is our preferred precatalyst for oxidation catalysis.
- Huang, Daria L.,Vinyard, David J.,Blakemore, James D.,Hashmi, Sara M.,Crabtree, Robert H.
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p. 199 - 206
(2017/11/27)
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- Synthesis of Cyclic Peptide Mimetics by the Successive Ring Expansion of Lactams
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A successive ring-expansion protocol is reported that enables the controlled insertion of natural and non-natural amino acid fragments into lactams. Amino acids can be installed into macrocycles via an operationally simple and scalable iterative procedure, without the need for high dilution. This method is expected to be of broad utility, especially for the synthesis of medicinally important cyclic peptide mimetics.
- Stephens, Thomas C.,Lodi, Mahendar,Steer, Andrew M.,Lin, Yun,Gill, Matthew T.,Unsworth, William P.
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supporting information
p. 13314 - 13318
(2017/10/05)
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- Highly selective cycloalkane oxidation in water with ruthenium nanoparticles
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Ruthenium(0) nanospecies, with small sizes of approximately 1.75 nm, proved to be active, selective, and retrievable nanocatalysts for the oxidation of various cycloalkanes in neat water, using tert-butylhydroperoxide as an oxidant and at room temperature. Relevant conversions and selectivities (up to 97 %) were achieved towards the major formation of the ketone product, which constitutes a high-value-added intermediate for polymer or fine chemistry. The lifetime of the catalyst has been checked over several runs, with no significant loss of activity and selectivity. Kinetic and mechanistic investigations proved that radical species are involved in the oxidation process. A literature comparison showed the relevance and the usefulness of the present ruthenium nanocatalytic system in a benign reaction context. Active, selective, and retrievable! A sustainable oxidation process of cycloalkanes to the ketones with an easy-to-handle and reusable catalyst, in neat water, and under ambient conditions is described. The active catalyst is a ruthenium(0) nanospecies. t-BHP=tert-butylhydroperoxide.
- Denicourt-Nowicki, Audrey,Lebedeva, Anastasia,Bellini, Clément,Roucoux, Alain
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p. 357 - 362
(2016/02/05)
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- Direct oxidation of cycloalkanes to cycloalkanones with oxygen in water
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It doesn′t take much to oxidize cycloalkanes directly to the corresponding cyclic ketones: molecular oxygen as the oxidant, water as the solvent, the cofactor NADP+ (and a little 2-propanol to reduce it), as well as two catalytic enzymes - a hydroxylating P450 monooxygenase and an alcohol dehydrogenase (see scheme). Copyright
- Staudt, Svenja,Burda, Edyta,Giese, Carolin,Müller, Christina A.,Marienhagen, Jan,Schwaneberg, Ulrich,Hummel, Werner,Drauz, Karlheinz,Gr?ger, Harald
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p. 2359 - 2363
(2013/03/28)
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- Exaltone (=Cyclopentadecanone) from Isomuscone (=Cyclohexadecanone), a one-C-atom ring-contraction methodology via a stereospecific favorskii rearrangement: Regioselective application to (-)-(R)-muscone
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Treatment of cyclohexadecanone (1g; with I2 (2.2 mol-euqiv.) and KOH in MeOH) furnished the unsaturated (Z)-ester 2g in 83% yield, via a stereospecific Favorskii rearrangement (Scheme 1). Further treatment with 3-chloroperbenzoic acid (m-CPBA) afforded the unreported epoxy ester 3g (88% yield), which was cleaved in 33% yield to Exaltone (=cyclopentadecanone; 1f) with NaOH in MeOH/H2O and then HCl at 65°. This methodology was similarly extended to higher (C17) and lower (C15 to C11) cyclic ketone analogues, as well as regioselectively to (-)-(R)-muscone (5c) and homomuscone (5f) (Scheme 2). Olfactive properties of the corresponding macrocyclic 1-oxaspiro[2,n]alkanes and -alkenes 4 and 8, resulting from a Coreyi-Chaykovsky oxiranylation, are also presented. Copyright
- Chapuis, Christian,Robvieux, Fabrice,Cantatore, Carole,Saint-Leger, Christine,Maggi, Laurent
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p. 428 - 447
(2012/05/07)
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- Structure-reactivity relationship for alcohol oxidations via hydride transfer to a carbocationic oxidizing agent
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Second-order rate constants were determined for the oxidation of 27 alcohols (R1R2CHOH) by a carbocationic oxidizing agent, 9-phenylxanthylium ion, in acetontrile at 60°C. Alcohols include open-chain alkyl, cycloalkyl, and unsaturated alcohols. Kinetic isotope effects for the reaction of 1-phenylethanol were determined at three H/D positions of the alcohol (KIEα-D=3.9, KIEβ-D3=1.03, KIE OD=1.10). These KIE results are consistent with those we previously reported for the 2-propanol reaction, suggesting that these reactions follow a hydride-proton sequential transfer mechanism that involves a rate-limiting formation of the α-hydroxy carbocation intermediate. Structure-reactivity relationship for alcohol oxidations was deeply discussed on the basis of the observed structural effects on the formation of the carbocationic transition state (Cδ+-OH). Efficiencies of alcohol oxidations are largely dependent upon the alcohol structures. Steric hindrance effect and ring strain relief effect win over the electronic effect in determining the rates of the oxidations of open-chain alkyl and cycloalkyl alcohols. Unhindered secondary alkyl alcohols would be selectively oxidized in the presence of primary and hindered secondary alkyl alcohols. Strained C7-C11 cycloalkyl alcohols react faster than cyclohexyl alcohol, whereas the strained C5 and C12 alcohols react slower. Aromatic alcohols would be efficiently and selectively oxidized in the presence of aliphatic alcohols of comparable steric requirements. This structure-reactivity relationship for alcohol oxidations via hydride-transfer mechanism is hoped to provide a useful guidance for the selective oxidation of certain alcohol functional groups in organic synthesis. Copyright
- Lu, Yun,Bradshaw, Joshua,Zhao, Yu,Kuester, William,Kabotso, Daniel
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p. 1172 - 1178
(2013/01/12)
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- Copper-containing SiCN precursor ceramics (Cu@SiCN) as selective hydrocarbon oxidation catalysts using air as an oxidant
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A molecular approach to metal-containing ceramics and their application as selective heterogeneous oxidation catalysts is presented. The aminopyridinato copper complex [Cu2(ApTMS)2] (ApTMSH = (4-methylpyridin2-yl)trimethylsilanylamine) reacts with poly(organosilazanes) via aminopyridine elimination, as shown for the commercially available ceramic precursor HTT 1800. The reaction was studied by 1H and 13C NMR spectroscopy. The liberation of the free, protonated ligand Ap TMSH is indicative of the copper polycarbosilazane binding. Crosslinking of the copper-modified poly(organosilazane) and subsequent pyrolysis lead to the copper-containing ceramics. The copper is reduced to copper metal during the pyrolysis step up to 1000 °C, as observed by solid-state 65Cu NMR spectroscopy, SEM images, and energydispersive spectroscopy (EDS). Powder diffraction experiments verified the presence of crystalline copper. All Cu@SiCN ceramics show catalytic activity towards the oxidation of cycloalkanes using air as oxidant. The selectivity of the reaction increases with increasing copper content. The catalysts are recyclable. This study proves the feasibility of this molecular approach to metal-containing SiCN precursor ceramics by using silylaminopyridinato complexes. Furthermore, the catalytic results confirm the applicability of this new class of metal-containing ceramics as catalysts.
- Glatz, Germund,Schmalz, Thomas,Kraus, Tobias,Haarmann, Frank,Motz, Guenter,Kempe, Rhett
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supporting information; experimental part
p. 4231 - 4238
(2010/07/04)
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- Unexpected nucleophilic behaviour of free-radicals generated from α-iodoketones
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The unexpected nucleophilic reactivity of free-radicals generated from α-iodoketones is reported; two different procedures, either employing tin or the more environmentally acceptable ethylsulfone-based coupling reagent 5c have been developed.
- De Dobbeleer, Corinne,Pospiil, Jii,De Vleeschouwer, Freija,De Proft, Frank,Marko, Istvan E.
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supporting information; experimental part
p. 2142 - 2144
(2009/09/06)
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- Ionic liquid promoted selective oxidation of organic compounds with NaBrO3
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1-Butyl-3-methylimidazolium bromide ([bmim]Br) as an ionic liquid promoted selectively the oxidation of alkyl arenes and alcohols to the corresponding carbonyl compounds with NaBrO3 in excellent yields under neutral conditions at the 70°C. Among the various ionic liquids examined, the [bmim]Br exhibited the best performances with NaBrO3. The ionic liquid can be recycled and reused for several runs without any significant loss of activity.
- Shaabani, Ahmad,Farhangi, Elham,Rahmati, Abbas
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experimental part
p. 905 - 908
(2009/09/06)
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- Gene encoding cyclododecanone monooxygenase
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The invention relates to a new strain of Pseudomonas putida (designated as HI-70) and to the isolation, cloning, and sequencing of a cyclododecanone monooxygenase-encoding gene (named cdnB) from said strain. The invention also relates to a new cyclododecanone monooxygenase and to a method of use of the cyclododecanone monooxygenase-encoding gene.
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- Aerobic oxidation of cycloalkanes, alcohols and ethylbenzene catalyzed by the novel carbon radical chain promoter NHS (N-hydroxysaccharin)
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Replacement of Ishii's N-hydroxyphthalimide (NHPI) with the novel carbon radical chain promoter N-hydroxysaccharin (NHS) affords, in combination with metal salts, notably Co, or other additives, selective catalytic autoxidation of hydrocarbons, alcohols and alkylbenzenes under mild conditions (25-100°C, O2 1 atm). The effects of solvent, temperature and the nature of the additives were investigated to give an optimised oxidation protocol for the various systems. The NHS/Co combination was more reactive than NHPI/Co in the autoxidation of cycloalkanes. In contrast, the opposite order of reactivity was observed in the autoxidation of ethylbenzene and alcohols. It is suggested, on the basis of bond dissociation energy (BDE) considerations, that this is a result of a change in the rate-limiting step with the more reactive ethylbenzene and alcohol substrates. In the autoxidation of the model cycloalkane, cyclododecane, the best results (90% selectivity to a 4:1 mixture of alcohol and ketone at 24% conversion) were obtained with NHS/Co(acac)3 in PhCF3 at 80°C. Competition experiments revealed that, in contrast to what is commonly believed, formation of the dicarboxylic acid by ring opening is not a result of further oxidation of the ketone product. It is suggested that ring opened products are a result of β-scission of the cycloalkoxy radical formed via (metal-catalysed) decomposition of the hydroperoxide. This is suppressed in the presence of NHS (or NHPI) which efficiently scavenge the alkoxy radicals.
- Baucherel, Xavier,Gonsalvi, Luca,Arends, Isabel W. C. E.,Ellwood, Simon,Sheldon, Roger A.
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p. 286 - 296
(2007/10/03)
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- Vanadium phosphorus oxide as an efficient catalyst for hydrocarbon oxidations using hydrogen peroxide
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Calcined vanadium phosphorus oxide (VPO) prepared by an organic route is found to be an active and effective catalyst for the oxidation of various alkanes such as cyclopentane, cyclohexane, n-hexane, cycloheptane, cyclooctane, cyclodecane and adamantane in acetonitrile solvent using the environmentally benign oxidant, hydrogen peroxide, where the oxidation mechanism is believed to involve a reversible V4+/V5+ redox cycle.
- Pillai, Unnikrishnan R.,Sahle-Demessie, Endalkachew
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p. 525 - 528
(2007/10/03)
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- A new catalytic system for the selective aerobic oxidation of large ring cycloalkanes to ketones
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The combination of cobalt with N-hydroxysaccharin proved to be an effective catalyst for the aerobic oxidation of large ring cycloalkanes to the corresponding ketones.
- Baucherel, Xavier,Arends, Isabel W. C. E.,Ellwood,Sheldon, Roger A.
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p. 426 - 428
(2013/09/06)
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- PROCESS FOR PRODUCTION OF DICARBOXYLIC ACIDS
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A process of the present invention produces a corresponding dicarboxylic acid by oxidative cleavage of a cycloalkane with oxygen and performs a reaction in the presence of a catalyst including an imide compound and a metallic compound, the imide compound having a cyclic imide skeleton represented by following Formula (I): wherein X is an oxygen atom or an-OR group, and wherein R is a hydrogen atom or a hydroxyl-protecting group, under conditions of a reaction temperature of 80°C or higher and a concentration of the cycloalkane in a system of 21% by weight or more. The imide compound includes, for example, N-hydroxyphthalimide. The amount of the imide compound is, for example, from about 0.000001 to about 0.01 mole per mole of the cycloalkane. In the production of a corresponding dicarboxylic acid by catalytic oxidation of a cycloalkane with oxygen, the present invention can yield the dicarboxylic acid in a high space time yield even using a small amount of the catalyst.
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Page/Page column 14-15; 19
(2008/06/13)
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- A novel, short and repeatable two-carbon ring expansion reaction by thermo-isomerization: Easy synthesis of macrocyclic ketones
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A novel two-carbon ring enlargement procedure, in which medium- and large-ring 1-vinylcycloalkanols are thermoisomerized in a flow reactor system at temperatures of 600°C to about 650°C, produces the isomeric ring-expanded cycloalkanones directly and efficiently. This two-step ring expansion protocol can easily be applied several times successively. For e.g., the musk odorant cyclopentadecanone (Exaltone?) is prepared from cycloundecanone in two repetitive cycles. Thermo-isomerization of the corresponding ethynylic cycloalkanols gives in moderate yields the bishomologous α,β-unsaturated macrocyclic (E)-2-cycloalkenones. A reaction mechanism via alkyl hydroxyallyl biradical intermediates is proposed.
- Nagel, Matthias,Hansen, Hans-Ju?rgen,Fra?ter, Georg
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p. 275 - 279
(2007/10/03)
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- Supported metalated phthalocyanine as catalyst for oxidation by molecular oxygen. Synthesis of quinones and carbonyl compounds
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Supported metalated phthalocyanine on K1O or on lamellar zirconium phosphate catalyses the oxidation of hydroquinones (and phenols) into quinones. Some interesting natural napthoquinones were also prepared (Juglone, Menadione, Lawsone, Phthiocol). Supported metalated phthalocyanine was also used in re-oxidation by oxygen of palladium and ruthenium, in the Wacker oxidation of olefins into ketones, in the oxidation of cyclohexadiene and in oxidation of benzylic alcohols in aldehydes.
- Villemin, Didier,Hammadi, Mohamed,Hachemi, Messaoud
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p. 1501 - 1515
(2007/10/03)
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- Stoichiornetric and catalytic oxidations of alkanes and alcohols mediated by highly oxidizing ruthenium-oxo complexes bearing 6,6'-dichloro-2,2'-bipyridine
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The ruthenium(II) complex cis-[Ru(6,6'-Cl2bpy)2(OH2)2](CF3SO3)2 (1) is a robust catalyst for C-H bond oxidations of hydrocarbons, including linear alkanes, using tert-butyl hydroperoxide (TBHP) as terminal oxidant. Alcohols can be oxidized by the '1 + TBHP' protocol to the corresponding aldehydes/ketones with high product yields at ambient temperature. Oxidation of 1 with Ce(IV) in aqueous solution affords cis-[Ru(VI)(6,6'-Cl2bpy)2O2]2+, which is isolated as a green/yellow perchlorate salt (2). Complex 2 is a powerful stoichiometric oxidant for cycloalkane oxidations under mild conditions. Oxidation of cis-decalin is highly stereoretentive; cis-decalinol is obtained in high yield, and formation of trans-decalinol is not observed. Mechanistic studies showing a large primary kinetic isotope effect suggest a hydrogen-atom abstraction pathway. The relative reactivities of cycloalkanes toward oxidation by 2 have been examined through competitive experiments, and comparisons with Gif-type processes are presented.
- Che,Cheng,Chan,Lau,Mak
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p. 7996 - 8000
(2007/10/03)
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- Oxidation catalytic system and oxidation process using the same
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A substrate (e.g., a cycloalkane, a polycyclic hydrocarbon, an aromatic compound having a methyl group or methylene group adjacent to an aromatic ring) is oxidized with oxygen in the presence of an oxidation catalyst comprising an imide compound of the following formula (1) (e.g., N-hydroxyphthalimide), and a co-catalyst (except phosphovanadomolybdic acid) containing an element selected from the group consisting of Group 2A elements of the Periodic Table of Elements, transition metals (Group 3A to 7A elements, Group 8 elements, Group 1B elements and Group 2B elements of the Periodic Table of Elements) and Group 3B elements of the Periodic Table of Elements, for the formation of an oxide (e.g., a ketone, an alcohol, a carboxylic acid): STR1 wherein R1 and R2 represent a substituent such as a hydrogen atom or a halogen atom, or R1 and R2 may together form a double bond or an aromatic or nonaromatic 5- to 12-membered ring, X is O or OH, and n is 1 to 3.
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- Ring Enlargement of Boracyclanes via Sequential One-Carbon Homologation. The First Synthesis of Boracyclanes in the Strained Medium Ring Range.
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We explored the Matteson homologation procedure as a means of enlarging the size of the ring in B-methoxyboracyclanes.
- Brown, Herbert C.,Phadke, Avinash S.,Rangaishenvi, Milind V.
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p. 6263 - 6264
(2007/10/02)
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- Oxidation of Secondary Alcohols with t-Butyl Hypochlorite in the Presence of Pyridine
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When treated with t-butyl hypochlorite and pyridine in methylene dichloride, secondary alcohols give the corresponding ketones in very high yield.The relative reactivities of a number of p-substituted 1-phenylethanols containing electron-donating and -withdrawing substituents were investigated.Oxidation of cis- and trans-4-t-butylcyclohexanol, as well as some other cycloalkanols, proceeds with the same relative rate.On the basis of this and other data a cyclic transition state and loss of α-hydrogen of the starting alcohols as hydride ion are proposed as characteristics of the reaction mechanism.
- Milovanovic, Jovan N.,Vasojevic, Miorad,Gojkovic, Svetislav
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p. 533 - 536
(2007/10/02)
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- Oxidation of Secondary Alcohols Using Raney Nickel
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A high yield, one-step oxidation procedure has been developed for the selective oxidation of secondary alcohols.
- Krafft, Marie E.,Zorc, Branka
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p. 5482 - 5484
(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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- Medium-ring Ketone Synthesis. Synthesis of Eight- to Twelve-membered Cyclic Ketones based on the Intramolecular Cyclization of Large-Membered Lactam Sulfoxides or Sulfones
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An effective general method for the construction of medium-ring ketones from the corresponding ω-bromocarboxylic acids is described.When the diamide disulfide 10 was treated with NaBH4 and NaH in 2-propanol, reductive cleavage of the sulfur-sulfur bond and concomitant intramolecular coupling of the resulting thiolate anion with the terminal bromide took place and the large-ring lactam sulfide 7, which was the key intermediate for the synthesis of medium-ring ketones, was obtained.Although lithium diisopropyl amide (LDA) treatment of 11 followed by reductive desulfurization provided cycloundecanone (13d) in only 19.5percent yield, intramolecular cyclization of the α-methylated analogues 17 with LDA proceeded smoothly and the keto sulfoxides 18 were obtained in quantitative yields.In the case of the lactam sulfones 21, tert-BuOK was effective as a base for the intramolecular cyclization, affording the keto sulfones 22 in quantitative yields.The keto sulfoxides 18 and sulfones 22 were subjected to reductive desulfurization with Al-Hg to yield medium-ring ketones 19 and 13, respectively, in high yields.Keywords - medium-ring ketone; intramolecular cyclization; large-ring lactam sulfide; bis(2-methylaminophenyl) disulfide; 2-methylaminobenzenethiol; reductive desulfurization; sulfur-stabilized carbanion; active methylene
- Ohtsuka, Yasuo,Oishi, Takeshi
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p. 454 - 465
(2007/10/02)
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- An Asymmetric Synthesis of Acyclic and Macrocyclic α-Alkyl Ketones. The Role of (E)- and (Z)-Lithioenamines
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Metalation and alkylation of chiral imines derived from C10, C12, and C15 cyclic ketones gave, under kinetic metalation conditions, 2-alkylcycloalkanones of absolute configuration opposite to that formed from thermodynamic metalation.Thus, (S)-(-)-2-methylcyclododecanone is formed kinetically in 60percent ee, whereas (R)-(+)-methylcyclododecanone is reached in 80percent ee under thermodynamic conditions.In a similar fashion, acyclic ketones 20, via their chiral imines 17, are alkylated enantioselectively under both kinetic and thermodynamic modes.The kinetic metalation gives exclusively the (Z)-lithioenamines (19), while reflux of this lithio anion gives only the (E)-lithioenamine (19).Chiral α-substituted ketones are produced in 18-97percent ee.
- Meyers, A. I.,Williams, Donald R.,White, Steven,Erickson, Gary W.
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p. 3088 - 3093
(2007/10/02)
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- 186. Steric Effects on Reaction Rates. Rate and Equilibrium Constants for Oxidation of Cyclanols
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Equilibrium constants for oxidations of cyclanols by cyclohexanone in benzene have been determined in the presence of aluminium isopropoxide.The free energies of the equilibrium (ΔGox) are correlated with equilibrium constants for dissociation of cyanohydrins, rate constants for cyclanol oxidation with chromic acid, ketone reduction with sodium borohydride and trifluoroethanolysis of tosylates.
- Paul, Mueller,Blanc, Jacky
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p. 1759 - 1766
(2007/10/02)
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