- Study of the addition of monoalkylphosphonic acids onto trialkyl-substituted epoxides
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The addition of 2-chloroethylphosphonic acid (or ethephon), a well-known stimulating molecule for the production of latex by Hevea brasiliensis, onto 2,3-epoxy-2-methylbutane was investigated to enhance the understandings on the addition mechanisms of reagents of alkylphosphonic acid type onto trialkyl-substituted epoxides. It was demonstrated that the addition occurs according to a three-step mechanism including a rapid nucleophilic attack of the phosphorated anion on the most alkyl-substituted carbon of the oxirane, followed by formation of a dioxaphospholane structure with release of water, and finally a hydrolytic cleavage of the dioxaphospholane cycle to generate the regioisomer 1:1 adduct where the phosphorated group is on the less alkyl-substituted carbon of the initial oxirane.
- Derouet,Cauret,Brosse
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- Kinetics of 2-methylbutene-2 epoxidation with 2-methylbutane hydroperoxide
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The kinetics of 2-methylbutene-2 epoxidation with 2-methylbutane hydroperoxide was studied in the presence of a molybdenum catalyst. The mathematical description of the hydroperoxide consumption and 2-methyl-butene-2 oxide formation was derived, and the most probable scheme of the process was suggested. The main kinetic constants were calculated.
- Petukhova,Sapunov,Kharlampidi,Petukhov
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- ESR Evudence for Localized Forms of C - C Ring-Opened Oxirane Radical Cations
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Localized forms of the C...C ring-opened oxirane and methyl-substituted oxirane radical cations have been detected by ESR spectroscopy following γ-irradiation of solid solutions of the parent compounds in the CFCl2CF2Cl matrix.For oxirane, 1,2-dimethyloxirane, and tetramethyloxirane, he localized forms possess the RCH2., RCHMe., and the RCMe2. radical centers, respectively.In the unsymmetrically substituted methyloxiranes, the radical center is localized at the oxirane carbon with the least number of methyl groups.The temperature needed to bring about the formation of of the localized species increases with methyl substitution at the localized radical center, the oxirane and methoxirane species being formed during irradiation at 77 K while the tetramethyloxirane species is produced subsequently from the delocalized planar form of the of ring-opened cation at 105-110 K.In contrast, only the delocalized forms of the oxirane cations have been observed in CFCl3, CF3CCl3, and CCl4, even at much higher temperatures (145-215 K) close to the softening points of these matrices.The possible structures of the localized forms of the oxirane radical cations are discussed, the two most reasonable models being either an orthogonal structure with noninteracting radical and carbocation centers or a similar species in which the carbocation center is complexed with the solvent or combined with a chloride ion.Despite the lack of ESR and other evidence for some type of solvent haloen participation in the localized structure, the latter model cannot be ruled out at present.
- Qin, Xue-Zhi,Snow, Larry D.,Williams, Ffrancon
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- Catalytic Radical-Polar Crossover Reactions of Allylic Alcohols
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Radical-polar crossover hydrofunctionalizations of tertiary allylic alcohols are described. Depending on the structure of the catalyst, corresponding epoxides or semipinacol rearrangement products are selectively obtained in good yields. Experimental evidence points to the participation of alkylcobalt complexes as electrophilic intermediates.
- Touney, Eric E.,Foy, Nicholas J.,Pronin, Sergey V.
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supporting information
p. 16982 - 16987
(2018/12/14)
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- Regioselective Organocatalytic Formation of Carbamates from Substituted Cyclic Carbonates
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A highly regioselective catalytic approach has been developed towards carbamates derived from cyclic organic carbonates by reaction of the latter with amine reagents under organocatalytic control. For various combinations of carbonate and amine substrates, an organocatalyst (TBD: 1,5,7-triazabicyclo[4.4.0]dec-5-ene) was used to increase the reaction kinetics while exerting excellent regioselective control. The current method is the first general approach towards the control over the regioselectivity of this reaction using a wide variety of easily accessed substituted organic carbonates. (Figure presented.) .
- Sope?a, Sergio,Laserna, Victor,Guo, Wusheng,Martin, Eddy,Escudero-Adán, Eduardo C.,Kleij, Arjan W.
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supporting information
p. 2172 - 2178
(2016/07/16)
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- EFFICIENT PROCESS FOR PRODUCING EPOXIDES BY OXIDATION OF OLEFINS IN THE HOMOGENEOUS GAS PHASE
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An economical one-step process is provided for the preparation of epoxides by oxidation of olefins in a homogeneous gas phase reaction, wherein the olefin is reacted in a flow reactor with a gas mixture of ozone and NO2 and/or NO as oxidants without use of a catalyst, and wherein ozone and NO2 and/or NO are mixed in a mixing chamber connected upstream to the flow reactor. The process is characterized in that the olefin in the reaction zone of the flow reactor is reacted at a reaction temperature of approximately 150° C. to approximately 450° C. and a pressure of 250 mbar to 10 bar with the gas mixture of the oxidant, that the carrier gas flow containing the olefin is heated in a preheating zone of the flow reactor to a temperature of 250° C. to 650° C., and that the gas mixture of the oxidant from the mixing chamber, having ambient temperature, is turbulently mixed with the olefin in the reaction zone of the flow reactor, so that the reaction temperature is reached during the mixing and the ratio of olefin-gas flow and gas flow of the oxidant is 5:1 to 1:1.
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Page/Page column 2
(2011/06/26)
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- (4 S,5 S)-2,2,4-Triethyl-5-methyl-1,3-dioxolane: A new volatile released by a triatomine bug
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Adults of the triatomine bug Triatoma brasiliensis release 2,2,4-triethyl-5-methyl-1,3-dioxolane (1) as a mixture of the (4S,5S)- and (4R,5R)-enantiomers in a ratio of 4:1. Among the volatile acetals identified from insects so far, this is the first example resulting from an intermolecular condensation of a carbonyl moiety and a diol substructure.
- Unelius,Bohman,Lorenzo,Troeger,Franke,Francke
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supporting information; experimental part
p. 5601 - 5603
(2011/03/20)
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- Transition-state geometry measurements from13C isotope effects. the experimental transition state for the epoxidation of alkenes withoxaziridines
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We here suggest and evaluate a methodology for the measurement of specific interatomic distances from a combination of theoretical calculations and experimentally measured 13C kinetic isotope effects. This process takes advantage of a broad diversity of transition structures available for the epoxidation of 2-methyl-2-butene with oxaziridines. From the isotope effects calculated for these transition structures, a theory-independent relationship between the C-O bond distances of the newly forming bonds and the isotope effects is established. Within the precision of the measurement, this relationship in combination with the experimental isotope effects provides a highly accurate picture of the C-O bonds forming at the transition state. The diversity of transition structures also allows an evaluation of the Schramm process for defining transition-state geometries on the basis of calculations at nonstationary points, and the methodology is found to be reasonably accurate.
- Hirschi, Jennifer S.,Takeya, Tetsuya,Hang, Chao,Singleton, Daniel A.
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experimental part
p. 2397 - 2403
(2009/07/30)
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- WO3 Nanoparticles on MCM-48 as a Highly Selective and Versatile Heterogeneous Catalyst for the Oxidation of Olefins, Sulfides, and Cyclic Ketones
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It is shown that nanosized WO3 particles supported on MCM-48 work as a highly efficient and selective heterogeneous catalyst for the oxidation of olefins, sulfides, and cyclic ketones using hydrogen peroxide or peracetic acid. The catalytic activity of the supported tungstate was dependent on the nature of the supporting materials and particle size. The catalyst system employs environmentally benign oxidants in halide-free solvents, and it does not require phase-transfer agents and pH control.
- Koo, Dong Hyun,Kim, Min,Chang, Sukbok
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p. 5015 - 5018
(2007/10/03)
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- Kinetics and mechanism of the liquid-phase rearrangement of 2-Methyl-2,3-epoxybutane in the presence of a magnesium bromide complex
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The mechanism of intramolecular rearrangement of epoxides in the presence of the MgBr2 · 2H2O · 4DMF catalytic complex was proposed on the basis of a kinetic study of the liquid-phase isomerization of 2-methyl-2,3-epoxybutane and data on the influence of the ligand environment of the catalyst, solvent nature, and the epoxide structure. Copyright
- Mel'nik,Khvatova,Moskvichev,Srednev
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p. 275 - 278
(2007/10/03)
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- Asymmetric alkene epoxidation catalysed by a novel family of chiral metalloporphyrins: Effect of structure on catalyst activity, stability and enantioselectivity
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A selection of alkenes has been epoxidised with iodosylbenzene, catalysed by three related iron(III) tetraarylporphyrins: 1*, 2* and 3* with four 2,6-di(1-phenylbutoxy)phenyl groups, with one pentafluorophenyl and three 2,6-di(1-phenylbutoxy)phenyl groups and with two pentafluorophenyl and two 2,6-di(1-phenylbutoxy)phenyl groups, respectively. 1* is very sterically hindered and prone to self-oxidation which makes it a relatively poor epoxidation catalyst. Introducing the smaller pentafluorophenyl groups, in place of 2,6-di(1-phenylbutoxy)phenyl, increases catalyst reactivity, stability and selectivity. This change allows easier access of the substrates to the active oxidant and also, by decreasing the electron density on the porphyrin ligand, increases the reactivity of the oxoiron intermediate and its stability towards self-oxidation. A family of five homochiral catalysts, 1, 2 and 3, [the analogues of 1*, 2* and 3*, prepared from (R,R)-2,6-di(1-phenylbutoxy)benzaldehyde] and catalyst 4 with three pentafluorophenyl and one (R,R)-2,6-di(1-phenylbutoxy)phenyl group and 5 the manganese(III) analogueof 3 have been used to epoxidise three prochiral alkenes. All the reactions give low enantioselectivities. Using styrene as the substrate, (S)-styrene epoxide is the major enantiomer obtained with all the catalysts except 1 which leads to the (R)-styrene epoxide being preferred. In contrast cis-hept-2-ene and 2-methylbut-2-ene give the same major epoxide enantiomer with all the catalysts. The dependence of the ee values on catalyst and substrate structure, temperature and solvent is examined and discussed.
- Lindsay Smith, John R.,Reginato, Gloriana
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p. 2543 - 2549
(2007/10/03)
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- Direct formation of pinacols from olefins over various titano-silicates
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The epoxidation and successive pinacol formation of tri- and tetraalkyl-substituted olefins using Ti-β/H2O2/H2O as the catalytic system has been investigated. Aluminum-free Ti-β exhibits better activity and pinacol selectivity than TS-1, TS-2, Ti-MCM-22, and mesoporous Ti-MCM-41. Pinacol (vic-diol) is obtained as the major product with small amounts of the side products pinacolone, alcohol (via hydration), and oligomers. The conversion and pinacol selectivity increase with an increase in reaction temperature and time. The change in product distribution with reaction time over Ti-β shows that the epoxide is the initial product which undergoes a secondary reaction to give pinacol as the major product. The conversion and H2O2 selectivity decrease with the bulkiness of the substituents at the C=C bond but the selectivity of pinacol is not significantly affected. The reactivity of cyclic 1-methyl-1-cyclohexene is considerably lower than that of the corresponding open-chain analogue 2-methyl-2-butene. The symmetrical tetramethyl-substituted 2,3-dimethyl-2-butene led to the formation of small amount of dimers over medium-pore titanium silicates TS-1, TS-2, and Ti-MCM-22. The epoxidation of these substituted olefins proceeded more rapidly when using acetonitrile as a cosolvent than under triphase conditions. Mechanistically, the primary epoxide product undergoes acid-catalyzed nucleophilic ring opening by H2O molecules to give pinacol.
- Sasidharan,Wu, Peng,Tatsumi, Takashi
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p. 260 - 265
(2007/10/03)
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- Hydrolysis of genotoxic methyl-substituted oxiranes: Experimental kinetic and semiempirical studies
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The kinetics of acid-catalyzed hydrolysis of seven methylated aliphatic epoxides - R1R2C(O)CR3R4 (A: R1=R2=R3=R4=H; B: R1=R2=R3=H, R4=Me; C: R1=R2=H, R3=R4=Me; D: R1=R3=H, R2=R4=Me(trans); E: R1=R3=H, R2=R4=Me(cis); F: R1=R3=R4=Me, R2=H; G: R1=R2=R3=R4=Me) - has been studied at 36 ± 1.5°C. Compounds with two methyl groups at the same carbon atom of the oxirane ring exhibit highest rate constants (k(eff) in reciprocal molar concentration per second: 11.0 ± 1.3 for C, 10.7 ± 2.1 for F, and 8.7 ± 0.7 for G as opposed to 0.124 ± 0.003 for B, 0.305 ± 0.003 for D, and 0.635 ± 0.036 for E). Ethylene oxide (A) displays the lowest rate of hydrolysis (0.027 M-1 s-1). The results are consistent with literature data available for compounds A, B, and C. To model the reactivities we have employed quantum chemical calculations (MNDO, AM1, PM3, and MINDO/3) of the main reaction species. There is a correlation of the logarithm k(eff) with the total energy of epoxide ring opening. The best correlation coefficients (r) were obtained using the AM1 and MNDO methods (0.966 and 0.957, respectively). However, unlike MNDO, AM1 predicts approximately zero energy barriers for the oxirane ring opening of compounds B, C, E and G, which is not consistent with published kinetic data. Thus, the MNDO method provides a preferential means of modeling the acidic hydrolysis of the series of methylated oxiranes. The general ranking of mutagenicity in vitro, A > B > C, is in line with the concept that this sequence also gradually leaves the expoxide reactivity optimal for genotoxicity toward reactivities leading to higher biological detoxifications.
- Kirkovsky, Leonid I.,Lermontov, Sergei A.,Zavorin, Sergei I.,Sukhozhenko, Ivan I.,Zavelsky, Vladimir I.,Thier, Ricarda,Bolt, Hermann M.
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p. 2141 - 2147
(2007/10/03)
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- Oxygen transfer reactions from an oxaziridinium tetrafluoroborate salt to olefins
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Oxaziridinium 5 efficiently epoxidises olefins. It reacts as an electrophilic reagent and does not transfer its oxygen to deactivated double-bonds or carbonyl functions. Epoxidation of cyclic allylic acetates shows a remarkable diastereoselectivity leading to the syn isomer. We propose that the epoxidation reaction proceeds through a one-step process.
- Lusinchi, Xavier,Hanquet, Gilles
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p. 13727 - 13738
(2007/10/03)
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- Steric and stereoelectronic control of the mode selectivity as a function of alkene structure in the reaction with dimethyl α-peroxy lactone: Cycloadducts and ene products versus epoxides
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The oxidation of di-, tri-, and tetrasubstituted alkenes 2 by dimethyl α-peroxy lactone (1) affords the cycloaddition, ene, and epoxidation products 3-6. In the presence of methanol, additionally the trapping products 7 are obtained. The observed dichotomy in the product distribution requires two different paths for this reaction, namely a path via an open, stretched 1,6 dipole and another path for epoxidation. Both paths arise from an SN2 attack of the double bond of the alkene 2 on the peroxide bond of the α-peroxy lactone 1, the first unsymmetrical (end-on attack), leading to the 1,6 dipole A, and the second symmetrical (central attack) with respect to the approach of the double bond, leading to epoxidation. The 1,6 dipole is postulated to afford the cycloadducts, of which the thermodynamically favored diastereomers are obtained, and the ene products. In the epoxidation, the α-lactone released after oxygen transfer oligomerizes to the polyester 8 or in the presence of methanol is trapped as α-methoxy acid 9. The reaction is regioselective both with respect to the attacked oxygen atom of the α-peroxy lactone 1, as revealed by the trapping products 7, as well as with respect to the attacking carbon atom for unsymmetrical alkenes 2c,d, as displayed by the ene products 5 and 6. The former regioselectivity is dictated by the inherent polarization of the peroxide bond through the carbonyl group which makes the alkoxy oxygen the more electrophilic one toward nucleophilic attack, while for the latter the incipient positive charge of the open 1,6 dipole is better stabilized by the more substituted carbon atom of the end-on attacking unsymmetrical alkene. The preferred reaction mode has been found to be sensitive to the structure of the alkene and the difference in reactivity has been explained in terms of steric and stereoelectronic factors. Thus, for the sterically less hindered cis-di- and trisubstitued alkenes the path along the open 1,6 dipole is favored (stereoelectronic control), while the more sterically demanding trans-di- and tetrasubstituted alkenes react by the epoxidation mode (steric control).
- Adam, Waldemar,Blancafort, Lluis
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p. 4778 - 4787
(2007/10/03)
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- Oxirane Formation in the Reaction of NO3 Radicals with Alkenes
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Chemical Kinetics / Mass Spectrometry / Radicals.Mass spectra of products formed in the reaction between NO3 and cis-2-butene, isobutene, 2-methyl-2-butene and 2,3-dimethyl-2-butene at 298 K and p = 3-10 mbar were obtained, using a fast flow system with molecular beam sampling.The spectra indicate formation of an oxirane in each reaction.Within experimental error the oxirane yields in the reaction of cis-2 butene and of 2,3-dimethyl-2-butene were identical (90+/-10)percent.The rate of oxirane formation was found to obey the rate equation for the reaction: NO3 + alkene oxirane + NO2. (1) Good agreement was obtained for the rate constants of reaction (1) determined from the rate of oxirane formation and those determined in earlier works from the consumption of reactants.
- Wille, U.,Rahman, M. M.,Schindler, R. N.
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p. 833 - 835
(2007/10/02)
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- TRANSFERT D'OXYGENE SUR LA DOUBLE LIAISON ETHYLENIQUE A PARTIR D'UN SEL D'OXAZIRIDINIUM
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Some examples of transfer of oxygen from an oxaziridinium salt to ethylenic derivatives to give epoxides are described.
- Hanquet, G.,Lusinchi, X.,Milliet, P.
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p. 3941 - 3944
(2007/10/02)
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- Dissociation of Positively Charged Aliphatic Epoxides. II. +. Epoxides and α,β Unsaturated Ethers
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The unimolecular dissociations of C5 epoxides ions mono- or disubstituted at C1 give exclusive loss of CH3 and exclusive formation of methoxyvinyl carbenium ion, both in the source and in the 2nd field-free region.In the case of the 1,2-disubstituted ion in the 2nd field-free region the loss of ethene is the only pathway, while a competition occurs for the trisubstituted ion leading to +. and +. ions, the structure of which are demonstrated.The first step of the different mechanisms is the cleavage of the heterocyclic C-C bond.
- Bouchoux, Guy,Djazi, Feycal,Hoppilliard, Yannik,Jaudon, Pascale,Nouts, Nathalie
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- USING THE COMPARISON OF STERIC VERSUS ELECTRONIC EFFECTS TO INFER MECHANISTIC INFORMATION IN STEPWISE ELECTROPHILIC ADDITION REACTIONS INVOLVING THREE-MEMBERED CYCLIC INTERMEDIATES
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Correlations of IP's versus relative reactivities or formation constants of reactions of alkenes with ArSCl, MeCO3H, Ag(1+), or HgCl2 reveal that complexation reactions show steric dependence, that additions with the first step rate-determining are sterically independent, and that those with the second step rate-determining are sterically dependent.
- Nelson, Donna J.,Soundararajan, Raman
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p. 6207 - 6210
(2007/10/02)
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- Epoxidation of Alkenes by Dimethyldioxirane: Evidence for a Spiro Transition State
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The relative reactivity series for the epoxidation of alkenes by dimethyldioxirane showed the reaction to be unexpectedly sensitive to steric factors; cis compounds were 8 times as reactive as the trans isomers.
- Baumstark, A. L.,McCloskey, C. J.
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p. 3311 - 3314
(2007/10/02)
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- Oxidation Reactions Using Magnesium Monoperphthalate: A Comparison with m-Chloroperoxybenzoic Acid
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Magnesium monoperphthalate hexahydrate (MMPP), a newly developed reagent with high stability at ambient temperatures, has been shown to oxidise a wide range of substrates under mild conditions: the substrates include alkenes, ketones, sulphides and sulphoxides, pyridine, and dipotassium p-tolylpentafluorosilicate.
- Brougham, Paul,Cooper, Mark S.,Cummerson, David A.,Heaney, Harry,Thompson, Nicola
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p. 1015 - 1017
(2007/10/02)
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- Selective Epoxidation of Olefins by Oxo(V) Alkylpreoxides. On the Mechanism of the Halcon Epoxidation Process
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Novel vanadium(V) alkylperoxy complexes with the general formula VO(OOR)(R'-OPhsal-R'') (II) were synthesized and characterized by physicochemical methods.These complexes most probably have a pentagonal pyramidal structure, with an axial vanadyl group and, in the pentagonal plane, three positions occupied by the Schiff base planar ligand and two positions occupied by a bidendate alkylperoxy group which is presumably weakly coordinatively bonded to the metal by the alkoxy oxygen atom.These complexes are very effective reagents for the selective transformation of olefins into epoxides, with yields ranging from 40percent for 1-octene to 98percent for tetramethylethylene.The reactivity of olefins is sensitive to steric hindrance and increases with the olefin nucleophilicity.The epoxidation of olefins by complexes II is steroselective, inhibited by water, alcohols, and basic ligands or solvents, and accelerated in polar nondonor solvents.Kinetic studies showed that the olefin coordinates to the metal prior to the decomposition of the metal-olefin complex in the rate-determining step.Competitive epoxidation of several olefins vs. cyclohexene showed that the more strongly coordinated olefins exert an inhibiting effect on the epoxidation of the less strongly coordinated ones.These data, which are similar to those of the Halcon catalytic epoxidation process, are consistent with a pseudocyclic peroxy metalation mechanism.
- Mimoun, Hubert,Mignard, Michel,Brechot, Philippe,Saussine, Lucien
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p. 3711 - 3718
(2007/10/02)
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- Reactions of Oxygenated Radicals in the Gas Phase. Part 15. Reactions of t-Butylperoxyl Radicals with Alkenes
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The photo-oxidation of mixtures of trans-2,2'-azoisobutane and some aliphatic alkenes has been studied between 313 and 393 K.Rate constants for the reaction between t-butylperoxyl radicals with ethene, 2-methylpropene, 2-methylbut-1-ene, 2-methylbut-2-ene, and 2,3-dimethylbut-2-ene have been determined at 393 K.Arrhenius parameters for the reaction (22) have been determined for 2-methylbut-2-ene and 2,3-dimethylbut-2-ene.They are log (A22/dm3mol-1s-1) of 8.16+/-0.38 and 8.58+/-0.61, and E22/kJ mol-1 of 56.6+/-2.4 and 48.7+/-4.1, respectively.The data obtained in this work are compared with that obtained for the series hydroperoxyl, and isopropylperoxyl radicals, and with rate data obtained for the addition reaction between alkenes and peracetyl radicals.
- Morgan, Morag E.,Osborne, David A.,Waddington, David J.
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p. 1869 - 1873
(2007/10/02)
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- Reactions of Oxygenated Radicals in the Gas Phase. Part 12. The Reactions of Isopropylperoxyl Radicals and Alkenes
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The co-oxidation of trans-2,2'-azopropane and some aliphatic alkenes has been studied between 303 and 408 K.From the yields of molecular products, rate data have been obtained for the reaction of isopropylperoxyl radicals and the following alkenes, 2-methylbut-2-ene, 2-methylbut-1-ene, 2-methyl-propene, propene, and 3-fluoropropene (reaction (22)).It is shown that the isopropylperoxyl radical is less reactive than methylperoxyl but still shows distinct electrophilic character in these reactions.
- Sway, Mohammed I.,Waddington, David J.
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p. 139 - 144
(2007/10/02)
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- PEROXO AND ALKYLPEROXIDIC MOLYBDENUM(VI) COMPLEXES AS INTERMEDIATES IN THE EPOXIDATION OF OLEFINS BY ALKYL HYDROPEROXIDES
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Novel oxoperoxomolybdenum(VI) complexes with the general formula MoO(O2)L2X2 (III, L = DMF, HMPT) and MoO(O2)Cl(O-N)L(IV, O-N = pyridin-2-carboxylate (Pic), 8-hydroxyquinolinate (Quin)) were prepared from the reaction of Ph3COOH or H2O2 with the corresponding cis-dioxo complexes.In the reaction with Ph3COOH both oxygen atoms of the peroxo moiety were found, by 18O labeling experiments, to come from the hydroperoxide.The X-ray crystal structure of MoO(O2)Cl(Pic)(HMPT) revealed a bipyramidal pentagonal surrounding with a rather short O-O distance (1.41 Angstroem).Complexes III were found to be more reactive than MoO(O2)2,HMPT for the epoxidation of olefins (oxidative cleavage products are consecutively formed) but react by the same cyclic peroxymetalation mechanism.The absence of reaction in the case of complexes IV illustrates the necessity for the metal to possess an equatorial releasable coordination site adjacent to the peroxo group for the oxygen transfer to occur.Catalytic oxidation of olefins using Ph3COOH gave a selectivity in oxygenated products very different from that using t-BuOOH, and 18O labeling studies showed that alkyl-peroxidic rather than peroxo species are intermediates in this latter reaction.The mechanism of epoxidation of olefins by alkyl hydroperoxides catalyzed by d0 metal complexes is discussed.
- Chaumette, Patrick,Mimoun, Hubert,Saussine, Lucien,Fischer, Jean,Mitschler, Andre
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p. 291 - 310
(2007/10/02)
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- Model Systems for Cytochrome P450 Dependent Mono-oxygenases. Part 1. Oxidation of Alkenes and Aromatic Compounds by Tetraphenylporphinatoiron(III) Chloride and Iodosylbenzene
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A selection of aliphatic alkenes, substituted styrenes, and cis- and trans-stilbene have been epoxidised with tetraphenylporphinatoiron(III) chloride and iodosylbenzene, a model system for the cytochrome P450 dependent mono-oxygenases.The epoxidations are stereospecifically syn and the reactivities of the alkenes show that cis-alkenes are more reactive than their trans-isomers and that electron-releasing substituents favour the reaction.A Hammett ρ value of -0.93 is obtained from the epoxidation of the substituted styrenes.Three polycyclic hydrocarbons, phenanthrene, acenaphthylene, and pyrene, are epoxidised in low yield.The model system hydroxylates anisole and naphthalene but is insufficiently reactive to oxidise benzene; with toluene, side-chain oxidation but no ring hydroxylation occurs.The mechanisms of these oxidations and the nature of the reactive species are discussed.
- Smith, John R. Lindsay,Sleath, Paul R.
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p. 1009 - 1016
(2007/10/02)
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- Reactions of Oxygenated Radicals in the Gas Phase. Part 7. Reactions of Methylperoxyl Radicals and Alkenes
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The reactions of methylperoxyl radicals with alkenes have been studied between 373 and 403 K.The peroxyl radicals were generated by the oxidation of di-t-butyl peroxide.Arrhenius parameters for reaction (18) have been determined for 2-meth
- Osborne, David A.,Waddington, David J.
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p. 925 - 930
(2007/10/02)
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