- Highly Selective Hydrogenation of Phenols to Cyclohexanone Derivatives Using a Palladium@N-Doped Carbon/SiO2Catalyst
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A new palladium-based heterogeneous material was synthesized by means of immobilization of Pd(OAc)2/1,10-phenanthroline on commercially available SiO2and subsequent pyrolysis at 600 °C for 2 h in air, namely, a Pd@N-doped carbon/SiO2catalyst. The obtained catalyst was studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) techniques, and was effectively applied in the highly selective hydrogenation of phenols to give the corresponding cyclohexanone derivatives with 93-98% yields at 100 °C under 0.4 MPa H2in EtOH. It was demonstrated that introducing nitrogen could effectively promote the Pd dispersion and enhance the electronic interaction of Pd, both of which facilitate the improvement of the catalytic activity and selectivity. The likely reaction pathway was outlined to elucidate the selective hydrogenation mechanism according to experimental results.
- Sheng, Xueru,Wang, Chao,Wang, Wentao
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supporting information
p. 2425 - 2431
(2021/11/16)
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- Oxidation of Alkanes by Periodate Using a MnV Nitrido Complex as Catalyst
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The design of catalytic systems that can selectively oxidize unactivated C?H bonds under mild conditions is a challenge to chemists. We report here that the manganese(V) nitrido complex [MnV(N)(CN)4]2? is a highly efficient catalyst for the oxidation of alkanes by periodate (IO4 ?) at ambient conditions. Excellent yields of alcohols and ketones (>95 %) are obtained with a maximum turnover number (TON) of 3000.
- Ma, Li,Chen, Lingjing,Lau, Tai-Chu
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p. 2846 - 2848
(2016/10/25)
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- From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
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A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
- Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
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supporting information
p. 2043 - 2046
(2016/02/05)
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- Stereoselective oxidation of alkanes with: M -CPBA as an oxidant and cobalt complex with isoindole-based ligands as catalysts
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Two complexes with isoindole-core ligands of general formula [M{C6H4C(NH2)NC(ONCMe2)2}2](NO3)2 (M = Co for 1 and M = Ni for 2) were studied as catalysts for the mild stereoselective alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as a main model substrate. Complex 1 disclosed a pronounced activity, with high retention of stereoconfiguration of substrates (>98% for cis-1,2-DMCH) and highest cis/trans ratio of tertiary alcohols (products) of 56, under mild conditions. The best achieved yields of tertiary cis-alcohols were of 13.7 and 50.5%, based on the substrate (cis-1,2-DMCH) and the oxidant (m-CPBA) respectively. Kinetic experiments, high bond and stereoselectivity parameters, kinetic isotope effect of 7.2(2) in the oxidation of cyclohexane, and incorporation of 18O from H218O support the involvement of CoIVO high-valent metal-oxo intermediates as main C-H attacking species.
- Nesterova, Oksana V.,Kopylovich, Maximilian N.,Nesterov, Dmytro S.
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p. 93756 - 93767
(2016/10/21)
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- Catalytic oxidation of alkanes by a (salen)osmium(VI) nitrido complex using H2O2 as the terminal oxidant
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The osmium(vi) nitrido complex, [OsVI(N)(L)(CH3OH)]+ (1, L = N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion) is an efficient catalyst for the oxidation of alkanes under ambient conditions using H2O2 as the oxidant. Alkanes are oxidized to the corresponding alcohols and ketones, with yields up to 75% and turnover numbers up to 2230. Experimental and computational studies are consistent with a mechanism that involves O-atom transfer from H2O2 to [OsVI(N)(L)]+ to generate an [OsVIII(N)(O)(L)]+ active intermediate.
- Chen, Man,Pan, Yi,Kwong, Hoi-Ki,Zeng, Raymond J.,Lau, Kai-Chung,Lau, Tai-Chu
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supporting information
p. 13686 - 13689
(2015/09/02)
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- Highly efficient alkane oxidation catalyzed by [MnV(N)(CN) 4]2-. Evidence for [MnVII(N)(O)(CN) 4]2- as an active intermediate
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The oxidation of various alkanes catalyzed by [MnV(N)(CN) 4]2- using various terminal oxidants at room temperature has been investigated. Excellent yields of alcohols and ketones (>95%) are obtained using H2O2 as oxidant and CF3CH 2OH as solvent. Good yields (>80%) are also obtained using (NH4)2[Ce(NO3)6] in CF 3CH2OH/H2O. Kinetic isotope effects (KIEs) are determined by using an equimolar mixture of cyclohexane (c-C6H 12) and cyclohexane-d12 (c-C6D12) as substrate. The KIEs are 3.1 ± 0.3 and 3.6 ± 0.2 for oxidation by H2O2 and Ce(IV), respectively. On the other hand, the rate constants for the formation of products using c-C6H12 or c-C6D12 as single substrate are the same. These results are consistent with initial rate-limiting formation of an active intermediate between [Mn(N)(CN)4]2- and H2O2 or CeIV, followed by H-atom abstraction from cyclohexane by the active intermediate. When PhCH2C(CH3)2OOH (MPPH) is used as oxidant for the oxidation of c-C6H12, the major products are c-C6H11OH, c-C6H10O, and PhCH2C(CH3)2OH (MPPOH), suggesting heterolytic cleavage of MPPH to generate a Mn=O intermediate. In the reaction of H2O2 with [Mn(N)(CN)4]2- in CF 3CH2OH, a peak at m/z 628.1 was observed in the electrospray ionization mass spectrometry, which is assigned to the solvated manganese nitrido oxo species, (PPh4)[Mn(N)(O)(CN)4] -·CF3CH2OH. On the basis of the experimental results the proposed mechanism for catalytic alkane oxidation by [MnV(N)(CN)4]2-/ROOH involves initial rate-limiting O-atom transfer from ROOH to [Mn(N)(CN)4]2- to generate a manganese(VII) nitrido oxo active species, [MnVII(N)(O) (CN)4]2-, which then oxidizes alkanes (R'H) via a H-atom abstraction/O-rebound mechanism. The proposed mechanism is also supported by density functional theory calculations.
- Ma, Li,Pan, Yi,Man, Wai-Lun,Kwong, Hoi-Ki,Lam, William W.Y.,Chen, Gui,Lau, Kai-Chung,Lau, Tai-Chu
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p. 7680 - 7687
(2014/06/10)
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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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- 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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- Catalyst-controlled aliphatic c-h oxidations with a predictive model for site-selectivity
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Selective aliphatic C-H bond oxidations may have a profound impact on synthesis because these bonds exist across all classes of organic molecules. Central to this goal are catalysts with broad substrate scope (small-molecule-like) that predictably enhance or overturn the substrate's inherent reactivity preference for oxidation (enzyme-like). We report a simple small-molecule, non-heme iron catalyst that achieves predictable catalyst-controlled site-selectivity in preparative yields over a range of topologically diverse substrates. A catalyst reactivity model quantitatively correlates the innate physical properties of the substrate to the site-selectivities observed as a function of the catalyst.
- Gormisky, Paul E.,White, M. Christina
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supporting information
p. 14052 - 14055
(2013/10/21)
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- Site-selective oxidation of unactivated C sp 3-H bonds with hypervalent iodine(III) reagents
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By design: The site-selective oxidation of unactivated secondary C sp 3-H bonds was accomplished with hypervalent iodine(III) reagents and tert-butyl hydroperoxide (see scheme). The preparation and derivatization of the hypervalent iodine(III) reagent are simple, thus allowing the rational design of these reagents to optimize the site selectivity of the oxidation. Copyright
- Moteki, Shin A.,Usui, Asuka,Zhang, Tiexin,Solorio Alvarado, Cesar R.,Maruoka, Keiji
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supporting information
p. 8657 - 8660
(2013/09/12)
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- Hydrocarbon oxidation catalyzed by manganese and iron complexes with the hexadentate ligand N,N′-di(ethylacetate)-N,N′-bis(2-pyridyl-methyl)- 1, 2-ethanediamine
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Analogs of recently reported manganese and iron catalysts for alkene and alkane oxidation reactions have been prepared with the potentially hexadentate ligand N,N′-di(ethylacetate)-N,N′-bis(2-pyridylmethyl)-1, 2-ethanediamine (debpn). The Mn(II) and Fe(II) complexes, which were previously found to be hepta-coordinate in the solid state, are capable of catalyzing alkene epoxidation and aliphatic C-H activation reactions, although these activities are inferior to those of related complexes with less coordinating ligands. The hydrocarbon oxidation catalyzed by iron is more severely disrupted. Cyclic voltammetry indicates that the +2 oxidation states for both debpn complexes' metal ions are stabilized by the two additional chelate arms. Product analysis of the C-H activation and olefin epoxidation chemistries suggest that ligand-substrate steric interactions may exert additional inhibitory effects on the reactivity for the manganese catalysts.
- Zhang, Qiao,Goldsmith, Christian R.
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p. 301 - 306
(2013/10/22)
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- Oxidation of alkane using Pt/Eu2O3/TiO 2/SiO2 catalyst with O2 and H2 in acetic acid under mild conditions
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A new solid catalyst of Pt/Eu2O3/TiO 2/SiO2 for oxidation of alkane was developed. Oxidation of adamantane using the multi-components supported catalyst with O2 and H2 was studied in acetic acid at 313 K. Several multi-components supported catalysts were prepared and tested the oxidation activity. It is found that loading order of Eu2O3, TiO2 and Pt on the SiO2 support strongly affected the oxidation catalysis. The active catalysts model was proposed from TEM-EDS analysis that very small Pt particles well dispersed on amorphous Eu2O3 and TiO 2 on the SiO2 support. Eu and Ti oxides concertedly activated O2 with electrons supplied from H2 on Pt, and active oxygen species efficiently oxidized adamantane and other alkanes to oxygenated compounds. Active oxygen species could not be identified but its reactivity was studied. It showed radical nature for oxidation of alkanes and a cleavage of C-H bond was the rate-determining step during the oxidation.
- Yamanaka, Ichiro,Suzuki, Yuta,Toida, Masashi
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experimental part
p. 286 - 290
(2011/01/04)
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- Combined effects on selectivity in Fe-catalyzed methylene oxidation
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Methylene C-H bonds are among the most difficult chemical bonds to selectively functionalize because of their abundance in organic structures and inertness to most chemical reagents. Their selective oxidations in biosynthetic pathways underscore the power of such reactions for streamlining the synthesis of molecules with complex oxygenation patterns. We report that an iron catalyst can achieve methylene C-H bond oxidations in diverse natural-product settings with predictable and high chemo-, site-, and even diastereoselectivities. Electronic, steric, and stereoelectronic factors, which individually promote selectivity with this catalyst, are demonstrated to be powerful control elements when operating in combination in complex molecules. This small-molecule catalyst displays site selectivities complementary to those attained through enzymatic catalysis.
- Chen, Mark S.,White, M. Christina
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scheme or table
p. 533 - 571
(2010/10/05)
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- Efficient catalytic oxidation of alkanes by lewis acid/[Os VI(N)Cl4]- using peroxides as terminal oxidants. Evidence for a metal-based active intermediate
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The oxidation of alkanes by various peroxides (tBuOOH, H 2O2, PhCH2C(CH3)2OOH) is efficiently catalyzed by [OsVI(N)Cl4]-/Lewis acid (FeCl3 or Sc(OTf)3) in CH2Cl 2/CH3CO2H to give alcohols and ketones. Oxidations occur rapidly at ambient conditions, and excellent yields and turnover numbers of over 7500 and 1000 can be achieved in the oxidation of cyclohexane with tBuOOH and H2O2, respectively. In particular, this catalytic system can utilize PhCH2C(CH 3)2OOH (MPPH) efficiently as the terminal oxidant; good yields of cyclohexanol and cyclohexanone (>70%) and MPPOH (>90%) are obtained in the oxidation of cyclohexane. This suggests that the mechanism does not involve alkoxy radicals derived from homolytic cleavage of MPPH but is consistent with heterolytic cleavage of MPPH to produce a metal-based active intermediate. The following evidence also shows that no free alkyl radicals are produced in the catalytic oxidation of alkanes: (1) The product yields and distributions are only slightly affected by the presence of O2. (2) Addition of BrCCl3 does not affect the yields of cyclohexanol and cyclohexanone in the oxidation of cyclohexane. (3) A complete retention of stereochemistry occurs in the hydroxylation of cis- and trans-1,2- dimethylcyclohexane. The proposed mechanism involves initial O-atom transfer from ROOH to [OsVI(N)Cl4]-/Lewis acid to generate [OsVIII(N)(O)Cl4]-/Lewis acid, which then oxidizes alkanes via H-atom abstraction.
- Yiu, Shek-Man,Man, Wai-Lun,Lau, Tai-Chu
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scheme or table
p. 10821 - 10827
(2009/02/05)
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- FeCl3-activated oxidation of alkanes by [Os(N)O 3]-
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Although the ion [OsVIII(N)(O)3]- is a stable species and is not known to act as an oxidant for organic substrates, it is readily activated by FeCl3 in CH2Cl2/CH 3CO2H to oxidize alkanes efficiently at room temperature. The oxidation can be made catalytic by using 2,6-dichloropyridine N-oxide as the terminal oxidant. The active intermediates in stoichiometric and catalytic oxidation are proposed to be [(O)3OsVIII≡N-Fe III] and [Cl4(O)OsVIII≡N-Fe III], respectively.
- Yiu, Shek-Man,Wu, Zhi-Biao,Mak, Chi-Keung,Lau, Tai-Chu
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p. 14921 - 14929
(2007/10/03)
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- Efficient stereoselective oxygenation of alkanes by peroxyacetic acid or hydrogen peroxide and acetic acid catalysed by a manganese(IV) 1,4,7- trimethyl-1,4,7-triazacyclononane complex
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The dinuclear manganese complex [LMn(IV)(O)3Mn(IV)L](PF6)2, where L is 1,4,7-trimethyl-1,4,7-triazacyclononane. catalyses the oxygenation of alkane by peroxyacetic acid or by H2O2 in the presence of acetic acid to give alkanols, alkanones and alkyl hydroperoxides. The reactions can give large turnovers (up to 1350 after 1 h at 20°C) and can occur with a high degree of retention of stereochemistry at tertiary carbon atoms.
- Lindsay Smith, John R.,Shul'pin, Georgiy B.
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p. 4909 - 4912
(2007/10/03)
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- Oxidation with the "H2O2 - Manganese(IV) complex - Carboxylic acid" reagent 1. Oxidation of saturated hydrocarbons with peroxy acids and hydrogen peroxide
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The complex [LMnIV(O)3MnIVL](PF6)2 (1), where L is 1,4,7-trimethyl-1,4,7-triazacyclononane, catalyzes a highly efficient stereoselective oxygenation of saturated hydrocarbons in the presence of H2O2. A carboxylic acid is an obligatory component of the reaction mixture, while acetonitrile or acetone can be used as solvent. The reaction occurs, forming alkyl hydroperoxide, ketone, and alcohol. Substitution at the tertiary carbon atom proceeds more easily than that at the secondary carbon atom, whereas primary C-H bonds are rather inactive. Oxidation of alkanes and alcohols with peroxy acids catalyzed by complex 1 occurs with lower efficiency.
- Shul'pin,Lindsay-Smith
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p. 2379 - 2386
(2007/10/03)
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- Diastereo- and enantioselective synthesis of dimethylcyclohexanamines by asymmetric reductive amination
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A series of optically active dimethylcyclohexanamines 6a-c, e, with ee values ranging from 86- > 99%, have been synthesised by asymmetric reductive amination of the corresponding racemic diastereomeric cyclohexanones 3a-c, e. Their conformation and configuration are also discussed.
- Speckenbach,Bisel,Frahm
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p. 1325 - 1330
(2007/10/03)
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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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- Mixed Organocuprates Derived from ortho-Heterosubstituted ArCu Species. Reactions with Simple α,β-Unsaturated Ketones
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We describe the reaction of new organocuprates of the form ArRTCuLi (Ar an ortho-heterosubstituted non-transferable ligand), and their reactions with simple α,β-unsaturated ketones.
- Arevalo, F.,Castedo, L.,Fernandez, B. R.,Mourino, A.,Sarandeses, L.
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p. 745 - 748
(2007/10/02)
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- On the Mechanism of the Ozonolysis of C-H Bonds: Influence of SiO2-Solvent, H/D Isotope Effect, Intermediates
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Ozonation of trans-1,2-dimethylcyclohexane (1) in CFCl3 solution, on dry silica gel, and in CFCl3/SiO2 suspension under otherwise equivalent conditions leads to comparable product distributions with very similar rates.In the presence of SiO2 mainly the fraction of retention product is definitely higher.Any activation of substrate or ozone is therefore highly improbable.This is supported by the kinetic H/D isotope effects for trishomobarrelene (10b) and spirooctane (12b), which both in solution and on SiO2 are found to be equal within the error limits.Upon ozonation of trishomobarrelene (10), trishomobullvalene (15), hexahydrobullvalene (7), and norcarane (20) hydrotrioxides occur as detectable intermediates which decompose above -40 deg C to give alcohols and singlet oxygen.Especially the secondary representatives from 7 and 20 are the first of their kind ever fully characterized by 1H NMR spectroscopy.
- Zarth, Martin,Meijere, Armin de
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p. 2429 - 2449
(2007/10/02)
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- Odorant substances
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New odoriferous compounds, particularly the compounds having the following formula: STR1 wherein R is an aliphatic residue having the formula STR2 wherein R1 is a C1-4 alkyl, C1-4 alkylidene or C2-4 alkenyl, the sum of the carbon atoms being in those residues from 2 to 5, m and n being equal to zero or 1, p being 1, 2 or 3 and the dotted lines representing one or two optional double bonds. The invention also relates to a method for the preparation of new di-ketones I: as well as the use of I as odoriferous compounds in odoriferous compositions, which are characterized by a certain proportion of compounds having the formula I.
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- Polycyclic phenols, alcohols and ketones from phenols, cyclic alcohols and cyclic ketones using a nickel oxide/manganese oxide/magnesium oxide catalyst in presence of at least one of hydrogen and nitrogen
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At least one of a polycyclic phenol, a polycyclic alcohol and a polycyclic ketone is produced under hydrogenation conditions using a nickel oxide/manganese oxide/magnesium oxide catalyst by subjecting at least one of a monocyclic ketone, a monocyclic alcohol and a monocyclic phenol to said conditions and said catalyst.
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- EFFETS DE SUBSTITUANTS EN SERIE DIALKYL-1,2 CYCLOHEXANIQUE-I. PERTURBATIONS CONFORMATIONNELLES INDUITES PAR LES INTERACTIONS STERIQUES ENTRE GROUPEMENTS VOISINS
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The equilibration of the cis and trans isomers of four epimeric pairs of 3,4-dialkyl cyclohexanones (alkyl = Me,Et) have been studied quantitatively at different temperatures.The thermodynamic constants ΔH and ΔS exhibit considerable variations depending on the nature (Me or Et) of the substituents.These quantities were also calculated from statistical considerations.Theoretical and experimental values are in agreement.The origin of the observed variation an increase of the diaxial conformer proportion due to enhanced steric hindrance in other possible conformers when a methyl group is substituted by an ethyl group.This was confirmed experimentally by an NMR study of the trans-3,4-dialkyl cyclohexanone oximes.
- Pons, A.,Chapat, J.P.
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p. 2219 - 2224
(2007/10/02)
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