- A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles
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A new heterogeneous catalytic system consisting of cobalt nanoparticles (CoNPs) supported on MgO and tert-butyl hydroperoxide (TBHP) as oxidant is presented. This CoNPs@MgO/t-BuOOH catalytic combination allowed the epoxidation of a variety of olefins with good to excellent yield and high selectivity. The catalyst preparation is simple and straightforward from commercially available starting materials and it could be recovered and reused maintaining its unaltered high activity.
- Rossi-Fernández, Lucía,Dorn, Viviana,Radivoy, Gabriel
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supporting information
p. 519 - 526
(2021/03/31)
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- SO2F2-Mediated Epoxidation of Olefins with Hydrogen Peroxide
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An inexpensive, mild, and highly efficient epoxidation protocol has been developed involving bubbling SO2F2 gas into a solution of olefin, 30% aqueous hydrogen peroxide, and 4 N aqueous potassium carbonate in 1,4-dioxane at room temperature for 1 h with the formation of the corresponding epoxides in good to excellent yields. The novel SO2F2/H2O2/K2CO3 epoxidizing system is suitable to a variety of olefinic substrates including electron-rich and electron-deficient ones.
- Ai, Chengmei,Zhu, Fuyuan,Wang, Yanmei,Yan, Zhaohua,Lin, Sen
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p. 11928 - 11934
(2019/10/02)
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- Remarkable increase in the rate of the catalytic epoxidation of electron deficient styrenes through the addition of Sc(OTf)3 to the MnTMTACN catalyst
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The effect of Lewis acids on the catalytic activity of [Mn2(μ-O)3(TMTACN)2](PF6)2 in the epoxidation of styrenes using hydrogen peroxide as the oxidant has shown that the addition of Sc(OTf)3 at low catalytic loading results in a very significant increase in the efficiency of the catalyst and a reduction of the reaction time to only 3 minutes in most cases.
- Nodzewska, Aneta,Watkinson, Michael
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supporting information
p. 1461 - 1464
(2018/02/19)
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- Regioselective hydrosilylation of epoxides catalysed by nickel(II) hydrido complexes
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Bench-stable nickel fluoride complexes bearing NNN pincer ligands have been employed as precursors for the regioselective hydrosilylation of epoxides at room temperature. A nickel hydride assisted epoxide opening is followed by the cleavage of the newly formed nickel oxygen bond by σ-bond metathesis with a silane.
- Wenz, Jan,Wadepohl, Hubert,Gade, Lutz H.
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supporting information
p. 4308 - 4311
(2017/04/21)
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- The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
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The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Br?nsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular heterodimer, kinetic studies on the catalytic cycle, and a thorough analysis of transition states by DFT calculations for the rationalization of the catalyst structure-selectivity relationship. On the basis of these investigations, we developed a kinetic resolution of racemic epoxides, which proceeds with high selectivity (up to s = 93), giving the unreacted epoxides and the corresponding protected 1,2-diols in high enantiopurity. Moreover, this approach could be advanced to an unprecedented stereodivergent resolution of racemic α-chiral carboxylic acids, thus providing access to a variety of enantiopure nonsteroidal anti-inflammatory drugs and to α-amino acid derivatives.
- Monaco, Mattia Riccardo,Fazzi, Daniele,Tsuji, Nobuya,Leutzsch, Markus,Liao, Saihu,Thiel, Walter,List, Benjamin
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supporting information
p. 14740 - 14749
(2016/11/18)
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- One-Pot Synthesis of N-tert-Butylsulfinylimines and Homoallylamine Derivatives from Epoxides
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The reaction of epoxides with tert-butanesulfinamide in the presence of a Lewis acid, such as erbium triflate or boron trifluoride–diethyl ether, in THF as solvent, under microwave or thermal activation, produces N-tert-butylsulfinylimines in reasonable yields. Aromatic and gem-disubstituted and trisubstituted alkyl epoxides performed better than mono-alkyl-substituted compounds. After imine formation, a subsequent indium-promoted allylation can be carried out in the same reaction flask in a single synthetic operation leading to homoallylamine derivatives with generally high yields.
- Lahosa, Alejandro,Foubelo, Francisco,Yus, Miguel
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supporting information
p. 4067 - 4076
(2016/08/24)
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- Catalytic Enantioselective Conversion of Epoxides to Thiiranes
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A highly efficient and enantioselective Br?nsted acid catalyzed conversion of epoxides to thiiranes has been developed. The reaction proceeds in a kinetic resolution, furnishing both epoxide and thiirane in high yields and enantiomeric purity. Heterodimer formation between the catalyst and sulfur donor affords an effective way to prevent catalyst decomposition and enables catalyst loadings as low as 0.01 mol %.
- Liao, Saihu,Leutzsch, Markus,Monaco, Mattia Riccardo,List, Benjamin
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supporting information
p. 5230 - 5233
(2016/05/19)
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- Oxidation of styrene and of some derivatives with H2O 2 catalyzed by novel imidazolium-containing manganese porphyrins: A mechanistic and thermodynamic interpretation
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The oxidation of styrene and derivatives with H2O2 catalyzed by manganese porphyrins in acetonitrile is described. The effect of the imidazolium substituent on the catalytic efficiency has been also considered. The thermodynamic analysis has indicated that enthalpy rules styrene oxidation when catalysts Mn(Porph)-1 and Mn(Porph)-2 are used whereas the entropy is the driven force for Mn(Porph)-3 and Mn(Porph)-4 catalyzed reactions. Interestingly, an enthalpy-entropy compensation phenomenon is observed when comparing the thermodynamic results obtained for catalysts Mn(Porph)-3 and Mn(Porph)-4. Hammett plots for the studied manganese porphyrins provided small ρ-values, and this is typical for multi-step reactions, indicating that there is no significant charge separation in the transition state. For Mn(Porph)-1 and Mn(Porph)-2 the formation of multiple active species can be put forward whereas for Mn(Porph)-3 and Mn(Porph)-4 a concerted-type mechanism, via metalloxetane intermediate, fits well with the values obtained for those catalysts. The imidazolium-based catalysts have shown to be efficient catalysts in styrene and derivatives oxidation with hydrogen peroxide.
- De Paula, Rodrigo,Sim?es, Mário M.Q.,Neves, M. Graa P.M.S.,Cavaleiro, José A.S.
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experimental part
p. 1 - 11
(2011/10/05)
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- A simple and versatile method for alkene epoxidation using aqueous hydrogen peroxide and manganese salophen catalysts
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We describe a simple and versatile method for the catalytic epoxidation of a broad range of olefins (e.g., ketones, esters, and alkyl halides) with aqueous H2O2 using manganese salophen catalysts. Low catalyst loading, short reaction times, and a simple reaction setup (e.g., no pH buffer is required) are salient features of the system, which unites the benefits of H2O2 as an oxidant with the versatility and modularity of salen-based catalysts.
- Liu, Shih-Yuan,Nocera, Daniel G.
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p. 1923 - 1926
(2007/10/03)
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- Trimanganese complexes bearing bidentate nitrogen ligands as a highly efficient catalyst precursor in the epoxidation of alkenes
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A series of trinuclear manganese complexes coordinated with neutral bidentate nitrogen ligands, [Mn3L2-(OAc)6], were prepared from manganese acetate and the corresponding ligands. Using peracetic acid as the oxidant, the air- and moisture-stable manganese clusters exhibited excellent catalytic activity and selectivity in the epoxidation of olefins under mild conditions. The highest activity was observed with a trinuclear complex containing a 2-pyridylimino ligand, [Mn3(ppei) 2(OAc)6] (ppei = 2-pyridinal-1-phenylethylimine). With this system, the substrate scope was extremely wide to include terminal and electron-deficient double bonds of both aliphatic and aromatic alkenes. The high activity was undiminished under the reaction conditions even directly using a mixture of the pyridylimino ligands and manganese acetates, making this process more convenient. It was also observed that analogous trinuclear complexes, such as [Mn3(bipy)2(OAc)6] and [Mn 3(phen)2(OAc)6], displayed excellent activities. While radical intermediacy was inferred from the product distribution, kinetic data revealed that the epoxidation is roughly first-order in manganese cluster precursor and oxidant, respectively, and zero-order in olefin. These results led us to propose that the trinuclear complexes [Mn 3L2(OAc)6] serve as catalyst precursors that dissociate into monomeric species with the formulation of [MnL 2(OAc)2] under the reaction conditions.
- Kang, Byungman,Kim, Min,Lee, Junseong,Do, Youngkyu,Chang, Sukbok
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p. 6721 - 6727
(2007/10/03)
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- Poly(ethylene glycol)-supported ααα-trifluoroacetophenone in dioxirane mediated alkene epoxidation reactions
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Poly(ethylene glycol) (PEG) was used for the immobilization of ααα-trifluoroacetophenone and the utility of this supported ketone has been examined in dioxirane mediated epoxidation of alkenes. The PEG-ketone reagent was found to be an effective homogeneous catalyst for the epoxidation of a variety of alkenes in the presence of Oxone A? and was readily recovered from the reaction mixtures and reused.
- Kan, Jovi Tze Wai,Toy, Patrick
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p. 6357 - 6359
(2007/10/03)
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- Synthesis of 4-acetoxystyrene oxide and related compounds
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A method is provided of producing 4-acetoxystyrene oxide and substituted 4-acetoxystyrene oxides wherein at least one of the ring hydrogen atoms is substituted with a C1 to C10 alkyl or alkoxy, amino, halogen or nitro, wherein 4-acetoxystyrene or the corresponding substituted 4-acetoxystyrene is epoxided with peracetic acid containing no more than a trace of a mineral acid or water. The invention also includes, as new compositions of matter, 3,5-dimethyl-4-acetoxystyrene oxide and 3,5-dibromo-4-acetoxystyrene oxide.
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- Is a Linear Relationship between the Free Energies of Activation and One-Electron Oxidation Potential Evidence for One-Electron Transfer Being Rate Determining? Intermediates in the Epoxidation of Alkenes by Cytochrome P-450 Models. 4. Epoxidation of a Series of Alkenes by Oxo(meso-te...
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The mechanism of reaction of (porphyrin)CrV(O)(X) with alkenes has been investigated by combining the electrochemical determinations of redox potentials with the tools of kinetics and product identification.Studies include the following: (i) the dynamics of the reaction of oxo(meso-tetrakis(2,6-dibromophenyl)porphinato)chromium(V) ((Br8TPP)CrV(O)(X) with 16 alkenes (1,4-diphenyl-1,3-butadiene, 4-methoxystyrene, 1,1-diphenylethylene, 4-methylstyrene, 2,3-dimethyl-2-butene, cis-stilbene, styrene, 4-acetoxystyrene, cyclohexene, norbornene, cis-cyclooctene, 4-cyanostyrene, cis-2-pentene, cyclopentene, 1-hexene, 1-octene); (ii) the dynamics of the reaction of norbornene with five (porphyrin)CrV(O)(X) species (oxo(meso-tetraphenylporphinato)chromium(V), oxo(meso-tetrakis(2,4,6-trimethylphenyl)porphinato)chromium(V), oxo(meso-tetrakis(2,6-dichlorophenyl)porphinato)chromium(V), oxo(meso-tetrakis(2,6-difluorophenyl)porphinato)chromium(V), and oxo(meso-tetrakis(2,6-dibromophenyl)porphinato)chromium(V)).Alkenes were selected on the basis of their 1e oxidation potential so as to cover the widest range of E1/2 possible (1.14-2.80 V (SCE)), and the 1e oxidation potentials for the (porphyrin)CrV(O)(X) varied from 0.790 to 0.975 V (SCE).Standard solutions of (porphyrin)CrV(O)(X) were obtained by controlled-potential bulk electrolysis of the corresponding (porphyrin)CrIV(O) and used in the kinetic (CH2Cl2 solvent, 30 deg C) and product studies.The time course for the change in concentration of (Br8TPP)CrV(O)(X), (Br8TPP)CrIV(O), and (Br8TPP)CrIII(X) was simulated for the reaction of (Br8TPP)CrV(O)(X) with selected alkenes possessing "low, medium, and high" oxidation potentials.The time dependence of V(O)(X)>, IV(O)>, and III(X)> as well as the could be accurately fit to a scheme involving the following: (i) bimolecular reaction of alkene with (Br8TPP)CrV(O)(X) to provide alkene oxidation product + (Br8TPP)CrIII(X); (ii) reversible comproportionation of (Br8TPP)CrV(O)(X) + (Br8TPP)CrIII(X) to provide (Br8TPP)CrIV(O) + (Br8TPP)CrIV(X)2; (iii) a spontaneous reversion (due to oxidation of solvent or solutes) of (Br8TPP)CrV(O)(X) to (Br8TPP)CrIV(O).The remainder of the alkene oxidations were followed by the more simplistic procedure of following disappearance of (Br8TPP)CrV(O)(X).The second-order rate constants (k1) determined by either method were found to be in agreement.For about half the alkenes studied, the standard free energies for 1e oxidation by (Br8TPP)CrV(O)(X), to provide alkene-derived ? cation radicals (calculated from the potentials for 1e reduction of (Br8TPP)CrV(O)(X) and 1e oxidation of the alkenes to ? cation radicals), exceed the free energies of activation for epoxidation of alkenes by (Br8TPP)CrV(O)(X).A unified mechanism ...
- Garrison, J. Mark,Ostovic, Drazen,Bruice, Thomas C.
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p. 4960 - 4966
(2007/10/02)
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