- Selective epoxidation of olefins by vanadylporphyrin [V IV O(TPP)] and electron deficient nonplanar β-octabromovanadylporphyrin [V IV O(TPPBr8)]
-
Meso-tetraphenylporphyrinatooxidovanadium(IV) [VIVO(TPP)] (1) and 2,3,7,8,12,13, 17,18-octabromo-meso-tetraphenylporphyrinatooxidovanadium(IV) [VIVO(TPPBr8)] (2) were synthesized and characterized by various spectroscopic techniques. 1 and 2 were utilized
- Maurya, Mannar R.,Prakash, Ved,Sankar, Muniappan
-
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- Enantiocomplementary Epoxidation Reactions Catalyzed by an Engineered Cofactor-Independent Non-natural Peroxygenase
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Peroxygenases are heme-dependent enzymes that use peroxide-borne oxygen to catalyze a wide range of oxyfunctionalization reactions. Herein, we report the engineering of an unusual cofactor-independent peroxygenase based on a promiscuous tautomerase that accepts different hydroperoxides (t-BuOOH and H2O2) to accomplish enantiocomplementary epoxidations of various α,β-unsaturated aldehydes (citral and substituted cinnamaldehydes), providing access to both enantiomers of the corresponding α,β-epoxy-aldehydes. High conversions (up to 98 %), high enantioselectivity (up to 98 % ee), and good product yields (50–80 %) were achieved. The reactions likely proceed via a reactive enzyme-bound iminium ion intermediate, allowing tweaking of the enzyme's activity and selectivity by protein engineering. Our results underscore the potential of catalytic promiscuity for the engineering of new cofactor-independent oxidative enzymes.
- Crotti, Michele,Kataja, Kim M.,Poelarends, Gerrit J.,Saravanan, Thangavelu,Xu, Guangcai
-
supporting information
p. 10374 - 10378
(2020/04/23)
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- Palladium-catalysed regio- And stereoselective arylative substitution of γ,δ-epoxy-α,β-unsaturated esters and amides by sodium tetraaryl borates
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Palladium-catalysed reactions of γ,δ-epoxy-α,β-unsaturated esters and amides with NaBAr4 reagents proceeded regio- and stereoselectively, producing allylic homoallyl alcohols with aryl-substituents in the allylic position for a wide range of substrates. A
- Artok, Levent,Bilgi, Yasemin,Ku?, Melih
-
supporting information
p. 6378 - 6383
(2020/09/07)
-
- Characteristics and hazards of the cinnamaldehyde oxidation process
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Pressure and temperature behavior of the cinnamaldehyde oxidation process was determined using a custom-designed mini closed pressure vessel test (MCPVT), which is a new method to investigate the stability and hazard assesment of the cinnamaldehyde oxidation reaction. The oxidation products were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that cinnamaldehyde was stable under nitrogen atmosphere but very unstable under oxygen atmosphere. The initial oxidation products were analyzed by iodimetry and the cinnamaldehyde peroxide value could reach 139.44 mmol kg?1when the oxidation temperature was 308 K. The oxidation kinetics of cinnamaldehyde were studied by using the pressureversustime (P-t) curves obtained from the MCPVT process. The reaction is a second-order reaction, the kinetic equation is ln k= ?2233.66 × (1/T) + 11.19, and the activation energyEais 18.57 kJ mol?1at 308-338 K. The explosion of the cinnamaldehyde oxidation reaction was observed by MCPVT, in which the onset temperature was 373 K. The main products of cinnamaldehyde oxidation are acetaldehyde, benzaldehyde, phenylacetaldehyde, acetophenone, 2-hydroxyphenyl acetone, cinnamaldehyde epoxide, benzoic acid, and cinnamic acid. Oxidation is a three-step process: (1) cinnamaldehyde reacts with oxygen to form peroxides; (2) complex oxidation reactions are caused by the thermal decomposition of peroxides; (3) rapid oxidation and thermal decomposition lead to explosion hazard.
- Dai, Su-Yi,Lai, Fang,Li, Wei-Guang,Li, Yuan-Lin,Liang, Min,Liu, Xiong-Min,Ma, Li,Yu, Chang
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p. 19124 - 19133
(2020/06/08)
-
- Borylation and rearrangement of alkynyloxiranes: A stereospecific route to substituted α-enynes
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1,3-Enynes are important building blocks in organic synthesis and also constitute the key motif in various bioactive natural products and functional materials. However, synthetic approaches to stereodefined substituted 1,3-enynes remain a challenge, as they are limited to Wittig and cross-coupling reactions. Herein, stereodefined 1,3-enynes, including tetrasubstituted ones, were straightforwardly synthesized from cis or trans-alkynylated oxiranes in good to excellent yields by a one-pot cascade process. The procedure relies on oxirane deprotonation, borylation and a stereospecific rearrangement of the so-formed alkynyloxiranyl borates. This stereospecific process overall transfers the cis or trans-stereochemistry of the starting alkynyloxiranes to the resulting 1,3-enynes.
- Fuentespina, Ruben Pomar,De La Cruz, José Angel Garcia,Durin, Gabriel,Mamane, Victor,Weibel, Jean-Marc,Pale, Patrick
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p. 1416 - 1424
(2019/07/10)
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- Synthesis of Phostones via the Palladium-Catalyzed Ring Opening of Epoxy Vinyl Phosphonates
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The reaction of epoxy aldehydes with tetraethyl methylenediphosphonate gave γ,δ-epoxy vinyl phosphonates. The palladium-catalyzed addition of primary alcohols gave the monoprotected diols as single diastereoisomers. The trans- and cis-epoxides lead to opp
- Gnawali, Giri Raj,Rath, Nigam P.,Spilling, Christopher D.
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p. 8724 - 8730
(2019/07/03)
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- Highly Regio- and Stereodivergent Access to 1,2-Amino Alcohols or 1,4-Fluoro Alcohols by NHC-Catalyzed Ring Opening of Epoxy enals
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Described is an unprecedented NHC-catalyzed (NHC=N-heterocyclic carbene), stereoselective ring opening of epoxy and cyclopropyl enals to deliver valuable compounds bearing multiple stereocenters. A straightforward three-step procedure involving two catalytic enantioselective transformations has been developed and leads to a regio- and stereodivergent synthesis of either 1,2-amino alcohols/diamines or 1,4-fluoro alcohols with excellent diastereo- and enantiopurity.
- Poh, Si Bei,Ong, Jun-Yang,Lu, Shenci,Zhao, Yu
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supporting information
p. 1645 - 1649
(2018/02/06)
-
- Stable Copper Nanoparticle Photocatalysts for Selective Epoxidation of Alkenes with Visible Light
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Selective epoxidation of various alkenes with molecular oxygen (O2) under mild conditions is a longstanding challenge in achieving syntheses of epoxides. Cu-based catalysts have been found to be catalytically active for selective epoxidations. However, the application of copper nanoparticles (CuNPs) for photocatalyzed epoxidations is encumbered by the instability of CuNPs in air. Herein we report that CuNPs supported on titanium nitride (TiN) without additional stabilizers not only are stable in air but also can catalyze selective epoxidation of various alkenes with O2 or even air as a benign oxidant under light irradiation. CuNPs remain in the metallic state due to the significant charge transfer that occurs between CuNPs and TiN. The epoxidation is driven by visible light irradiation at moderate temperatures, achieving good to high yields and excellent selectivity. The photocatalytic process is applicable to the selective epoxidation of various alkenes. In this photocatalytic system, reactant alkenes chemically adsorb on CuNPs, forming Cu-alkene surface complexes, and light irradiation can activate the complexes for reaction. The cyclic ether solvent also plays a key role, reacting with O2 on the surface of CuNPs under light irradiation, yielding oxygen adatoms. The activated surface complexes react with the adatoms, yielding the corresponding epoxides. Analysis of the influence of irradiation wavelength and intensity on the epoxidation suggests that light-excited electrons of CuNPs drive the reaction. The adatoms formed react with alkenes, producing the final product epoxides. We also observed interesting product stereoselectivity, predominantly generating the trans isomers for the epoxidation of stilbene (up to 97%). The findings reported here not only provide an effective and selective reaction system for alkene epoxidations but also are a step toward demonstrating the practical use of CuNPs as photocatalysts for various applications.
- Huang, Yiming,Liu, Zhe,Gao, Guoping,Xiao, Gang,Du, Aijun,Bottle, Steven,Sarina, Sarina,Zhu, Huaiyong
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p. 4975 - 4985
(2017/08/17)
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- Nanosheet-enhanced efficiency in amine-catalyzed asymmetric epoxidation of Α, Β-unsaturated aldehydes via host-guest synergy
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Amine-catalyzed asymmetric epoxidation of α, β-unsaturated aldehydes has been promoted by attaching the nanosheets of layered double hydroxides (LDHs), a natural and/or synthetic anionic layered compound. 76% of epoxide yield and 93% ee of major diastereomer have been afforded in the asymmetric epoxidation of cinnamaldehyde. The amine sites employed here are the amino group in α-amino acid anion intercalated in the interlayer space of LDHs. The nanosheets of LDHs have been revealed to play key role in the enhancement of catalytic activity by affording the desired basicity and the boost of enantioselectivity by serving as the rigid substituent of amino acids. The hydrophobic interlayer microenvironment and ordered arrangement of intercalated amino acid anions additionally contribute to the catalytic efficacy. Stronger interlayer hydrophobicity favors the conversion and epoxide yield and better arrangement of interlayer anions favors the ee.
- Liu, Hui,An, Zhe,He, Jing
-
-
- Electronic Structure and Multicatalytic Features of Redox-Active Bis(arylimino)acenaphthene (BIAN)-Derived Ruthenium Complexes
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The article examines the newly designed and structurally characterized redox-active BIAN-derived [Ru(trpy)(R-BIAN)Cl]ClO4 ([1a]ClO4-[1c]ClO4), [Ru(trpy)(R-BIAN)(H2O)](ClO4)2 ([3a](ClO4)2-[3c](ClO4)2), and BIAO-derived [Ru(trpy)(BIAO)Cl]ClO4 ([2a]ClO4) (trpy = 2,2′:6′,2′′-terpyridine, R-BIAN = bis(arylimino)acenaphthene (R = H (1a+, 3a2+), 4-OMe (1b+, 3b2+), 4-NO2 (1c+, 3c2+), BIAO = [N-(phenyl)imino]acenapthenone). The experimental (X-ray, 1H NMR, spectroelectrochemistry, EPR) and DFT/TD-DFT calculations of 1an-1cn or 2an collectively establish {RuII-BIAN0} or {RuII-BIAO0} configuration in the native state, metal-based oxidation to {RuIII-BIAN0} or {RuIII-BIAO0}, and successive electron uptake processes by the α-diimine fragment, followed by trpy and naphthalene π-system of BIAN or BIAO, respectively. The impact of the electron-withdrawing NO2 function in the BIAN moiety in 1c+ has been reflected in the five nearby reduction steps within the accessible potential limit of -2 V versus SCE, leading to a fully reduced BIAN4- state in [1c]4-. The aqua derivatives ({RuII-OH2}, 3a2+-3c2+) undergo simultaneous 2e-/2H+ transfer to the corresponding {RuIV-O} state and the catalytic current associated with the RuIV/RuV response probably implies its involvement in the electrocatalytic water oxidation. The aqua derivatives (3a2+-3c2+) are efficient and selective precatalysts in transforming a wide variety of alkenes to corresponding epoxides in the presence of PhI(OAc)2 as an oxidant in CH2Cl2 at 298 K as well as oxidation of primary, secondary, and heterocyclic alcohols with a large substrate scope with H2O2 as the stoichiometric oxidant in CH3CN at 343 K. The involvement of the {RuIV-O} intermediate as the active catalyst in both the oxidation processes has been ascertained via a sequence of experimental evidence.
- Singha Hazari, Arijit,Ray, Ritwika,Hoque, Md Asmaul,Lahiri, Goutam Kumar
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p. 8160 - 8173
(2016/08/24)
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- Asymmetric epoxidation of α,β-unsaturated aldehydes catalyzed by a spiro-pyrrolidine-derived organocatalyst
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The asymmetric epoxidation of α,β-unsaturated aldehydes, catalyzed by a spiro-pyrrolidine (SPD)-derived organocatalyst, has been accomplished with good diastereoselectivities (up to dr >20:1) and with high to excellent enantioselectivities (up to 99% ee).
- Xu, Ming-Hui,Tu, Yong-Qiang,Tian, Jin-Miao,Zhang, Fu-Min,Wang, Shao-Hua,Zhang, Shi-Heng,Zhang, Xiao-Ming
-
supporting information
p. 294 - 300
(2017/03/01)
-
- Diastereoselective synthesis of 3-acetoxy-4-(3-aryloxiran-2-yl)azetidin-2-ones and their transformation into 3,4-oxolane-fused bicyclic β-lactams
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cis-3-Acetoxy-4-(3-aryloxiran-2-yl)azetidin-2-ones were prepared through a Staudinger [2+2]-cyclocondensation between acetoxyketene and the appropriate epoxyimines in a highly diastereoselective way. Subsequent potassium carbonate-mediated acetate hydrolysis, followed by intramolecular ring closure through epoxide ring opening, afforded stereodefined 3-aryl-4-hydroxy-2-oxa-6-azabicyclo[3.2.0]heptan-7-ones as a novel class of C-fused bicyclic β-lactams. Selective benzylic oxidation of bicyclic N-(4-methoxybenzyl)-β-lactams with potassium persulfate and potassium dihydrogen phosphate provided the corresponding N-aroyl derivatives as interesting leads for further β-lactamase inhibitor development.
- Piens, Nicola,De Craene, Sven,Franceus, Jorick,Mollet, Karen,Van Hecke, Kristof,Desmet, Tom,D'Hooghe, Matthias
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p. 11279 - 11288
(2016/12/07)
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- Efficient oxidation of cinnamon oil to natural benzaldehyde over Β-cyclodextrin-functionalized MWCNTs
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We have designed and prepared β-cyclodextrin (β-CD)-functionalized multi-walled nanotubes (MWCNTs-g-CD) for the oxidation of cinnamon oil to natural benzaldehyde under aqueous conditions. The synergistic effect of combining MWCNTs with β-CD led to a remarkable increase in the performance of the MWCNTs-g-CD for the catalytic oxidation of cinnamaldehyde, which exhibited 95% cinnamaldehyde conversion and 85% selectivity to natural benzaldehyde with a short reaction time of 10 min. The MWCNTs-g-CD also exhibited outstanding recyclability with good stability, showing no discernible decrease in their catalytic activity over five reaction cycles.
- Yang, Zujin,Zhang, Xia,Fang, Yanxiong,Rui, Zebao,Ji, Hongbing
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p. 2086 - 2097
(2017/01/16)
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- Selective photocatalytic oxidation of alcohols to corresponding aldehydes in solvent-free conditions using porphyrin sensitizers
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Abstract: In this work, selective and aerobic photooxidation of a range of aromatic, aliphatic and α,β-unsaturated alcohols to corresponding carbonyl compounds has been performed with tetraphenylporphyrin (H2TPP), ClFeTPP and ZnTPP as sensitizers using visible light and in the presence of molecular oxygen in solvent-free conditions. The conversion rates for alcohols oxidations were in the order of free-base porphyrin (H2TPP)?>?metalloporphyrin (ClFeTPP) and (ZnTPP). This method has a wide range of applications, remarkable conversion and product yield in reasonable time, does not include cumbersome work-up, exhibits chemoselectivity, and proceeds under mild reaction conditions. As the matter of oxidation of cycloheptanol and cyclooctanol using H2TPP as photosensitizer, the TON reached up to 1686 and 2464, respectively and selectivity more than 99?%. Graphical abstract: [Figure not available: see fulltext.]
- Mehrabi-Kalajahi, Seyed Saeed,Hajimohammadi, Mahdi,Safari, Nasser
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p. 1069 - 1076
(2016/05/02)
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- Oxidation with air by ascorbate-driven quinone redox cycling
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Transition metal-free oxidation with air at room temperature has been achieved by simply using ascorbate (vitamin C) and catalytic amounts of menadione (vitamin K3). A combination of the mentioned vitamins transforms atmospheric oxygen into hydrogen peroxide, which is able to oxidize arylboronic acids and other chemical moieties. This journal is
- Silveira-Dorta, Gastón,Monzón, Diego M.,Crisóstomo, Fernando P.,Martín, Tomás,Martín, Víctor S.,Carrillo, Romen
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supporting information
p. 7027 - 7030
(2015/04/22)
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- Electron deficient nonplanar β-octachlorovanadylporphyrin as a highly efficient and selective epoxidation catalyst for olefins
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We have synthesized 2,3,7,8,12,13,17,18-octachloro-meso-tetraphenylporphyrinatooxidovanadium(iv) (VOTPPCl8) and characterized by various spectroscopic (UV-Vis, IR and EPR) techniques, MALDI-TOF mass spectrometry and elemental analysis. The DFT optimized structure of VOTPPCl8 in CH3CN exhibited a highly nonplanar saddle shape conformation of the porphyrin macrocycle. The cyclic voltammogram of VOTPPCl8 showed a 500 mV anodic shift in the first ring reduction potential and 220 mV in the first ring oxidation potential compared to VOTPP indicating the electron deficient nature of the porphyrin π-system and further proving the existence of a nonplanar conformation of the macrocycle in solution. Further, VOTPPCl8 exhibited very high thermal stability till 390 °C as indicated in its thermogram. The oxidation state of the metal ion (VIV) was confirmed by EPR spectroscopy and VOTPPCl8 exhibited an axial spectrum which corresponds to the axially compressed dxy1 configuration. VOTPPCl8 was utilised for the selective epoxidation of various olefins in good yields with very high TOF numbers (6566-9650 h-1) in the presence of H2O2 as an oxidant and NaHCO3 as a promoter in a CH3CN/H2O mixture. The oxidoperoxidovanadium(v) species is expected to be the intermediate during the catalytic reaction which is probed by 51V NMR spectroscopy and MALDI-TOF mass analysis. Notably, VOTPPCl8 is stable after the catalytic reaction and doesn't form a μ-oxo dimer due to the highly electron deficient nonplanar porphyrin core and can be reused for several cycles.
- Kumar, Ravi,Chaudhary, Nikita,Sankar, Muniappan,Maurya, Mannar R.
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p. 17720 - 17729
(2015/10/19)
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- Tunable Electrochemical and Catalytic Features of BIAN- and BIAO-Derived Ruthenium Complexes
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This article deals with a class of ruthenium-BIAN-derived complexes, [RuII(tpm)(R-BIAN)Cl]ClO4 (tpm = tris(1-pyrazolyl)methane, R-BIAN = bis(arylimino)acenaphthene, R = 4-OMe ([1a]ClO4), 4-F ([1b]ClO4), 4-Cl ([1c]ClO4), 4-NO2 ([1d]ClO4)) and [RuII(tpm)(OMe-BIAN)H2O]2+ ([3a](ClO4)2). The R-BIAN framework with R = H, however, leads to the selective formation of partially hydrolyzed BIAO ([N-(phenyl)imino]acenapthenone)-derived complex [RuII(tpm)(BIAO)Cl]ClO4 ([2]ClO4). The redox-sensitive bond parameters involving -N=C-C=N- or -Ni=C-C=O of BIAN or BIAO in the crystals of representative [1a]ClO4, [3a](PF6)2, or [2]ClO4 establish its unreduced form. The chloro derivatives 1a+-1d+ and 2+ exhibit one oxidation and successive reduction processes in CH3CN within the potential limit of ±2.0 V versus SCE, and the redox potentials follow the order 1a+ + + + ≈ 2+. The electronic structural aspects of 1an-1dn and 2n (n = +2, +1, 0, -1, -2, -3) have been assessed by UV-vis and EPR spectroelectrochemistry, DFT-calculated MO compositions, and Mulliken spin density distributions in paramagnetic intermediate states which reveal metal-based (RuII → RuIII) oxidation and primarily BIAN- or BIAO-based successive reduction processes. The aqua complex 3a2+ undergoes two proton-coupled redox processes at 0.56 and 0.85 V versus SCE in phosphate buffer (pH 7) corresponding to {RuII-H2O}/{RuIII-OH} and {RuIII-OH}/{RuIV=O}, respectively. The chloro (1a+-1d+) and aqua (3a2+) derivatives are found to be equally active in functioning as efficient precatalysts toward the epoxidation of a wide variety of alkenes in the presence of PhI(OAc)2 as oxidant in CH2Cl2 at 298 K, though the analogous 2+ remains virtually inactive. The detailed experimental analysis with the representative precatalyst 1a+ suggests the involvement of the active {RuIV=O} species in the catalytic cycle, and the reaction proceeds through the radical mechanism, as also supported by the DFT calculations.
- Hazari, Arijit Singha,Das, Ankita,Ray, Ritwika,Agarwala, Hemlata,Maji, Somnath,Mobin, Shaikh M.,Lahiri, Goutam Kumar
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p. 4998 - 5012
(2015/05/27)
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- Epoxide and hydroperoxide derived from naturally cinnamaldehyde and its Schiff base derivatives
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Thermal and photo epoxidation, photooxygenation reactions of cinnamaldehyde may be useful tool for the design of drugs to act as potent chemopreventation and anticancer agents. trans-Cinnamaldehyde was isolated from essential oil of cinnamon ( Cinnamonum verum). It was subjected to oxidation reactions either photochemically with hydrogen peroxide or thermally with 3-chloro-peroxybenzoic acid. Schiff base derivative was synthesized through condensation reaction with aniline. It subjected to photooxidation reaction in the presence of tetraphenylporphin as singlet oxygen sensitizer. photochemically oxidation reaction gave the corresponding epoxy derivative together with cis-isomerisation. Whereas, thermally oxidation reaction resulted the corresponding epoxy derivative together with cinnamic acid. In addition, photooxidation reaction of Schiff base derivative led to 1-phenyl-3-phenyliminopropen-1-yl hydroperoxide through endoperoxide derivative. The primary tested of hydroperoxide derivative showed a moderate degree of DNA degradation. trans-Cinnamaldehyde and its derivatives can act as antioxidants. They were trapped the reactive oxygen species (ROS) to give the intermediated epoxides and hydroperoxide derivatives, which could be alkylated or damage DNA, proteins and other biological species
- Elgendy, Eman M.,Khayyat, Suzan A.
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p. 6571 - 6574
(2015/02/19)
-
- Controlling the selectivity of the manganese/bicarbonate/hydrogen peroxide catalytic system by a biphasic pyrrolidinium ionic liquid/n-heptane medium
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The Mn2+/HCO3-/H2O2 catalytic system exhibits excellent aldehyde selectivity in the oxidation of various benzylic and allyic alcohols under mild conditions and short reaction time when the reactions are carried out in a biphasic dicationic pyrrolidinium ionic liquid/n-heptane medium. The dicationic pyrrolidinium ionic liquid shows differential solubility towards alcohols and their aldehydes whereas the immiscible n-heptane instantaneously extracted and separated aldehydes from the reaction phase. This design of biphasic ionic liquid/n-heptane catalytic system prevents the over-oxidation of aldehydes to carboxylic acids effectively. Separation and recycling can also be easily done by decantation of the n-heptane layer after reaction. With the biphasic system, high conversion of benzyl alcohol to benzaldehyde was achieved with very low loadings of H 2O2 and Mn(OAc)2 catalyst at room temperature and within short reaction time. Throughout 10 reaction cycles, a total turnover number (TON) of 37,600 was achieved and excellent catalytic reactivity and selectivity were maintained with an average yield of 94%.
- Wong, Wing-Leung,Ho, Kam-Piu,Lee, Lawrence Yoon Suk,So, Ming-Him,Chan, Tak Hang,Wong, Kwok-Yin
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p. 244 - 249
(2013/03/28)
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- Highly efficient asymmetric synthesis of α,β-epoxy esters via one-pot organocatalytic epoxidation and oxidative esterification
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Highly enantioselective synthesis of α,β-epoxy esters was achieved via one-pot organocatalytic epoxidation and consequent oxidative esterification. Excellent enantioselectivities (up to 99% ee) and good yields were obtained for a variety of α,β-epoxy esters. The method was readily scaled. Furthermore the product was applied towards the synthesis of (-)-clausenamide with excellent enantioselectivities (>99% ee).
- Xuan, Yi-Ning,Lin, Han-Sen,Yan, Ming
-
supporting information
p. 1815 - 1817
(2013/04/10)
-
- Highly efficient oxidative cleavage of carbon-carbon double bond over meso-tetraphenyl cobalt porphyrin catalyst in the presence of molecular oxygen
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Highly efficient and selective carbon-carbon double bond aerobic cleavage of olefins catalyzed by metalloporphyrins was investigated, and carbonyl compounds and epoxide were produced as the main products. CoTPP (cobalt meso-tetraphenyl porphyrin) showed excellent activity for the oxidative cleavage of carbon-carbon double bond by using styrene as model compound, in which the TOF (turnover frequency) and selectivity toward benzaldehyde was obtained with 2×104 h-1 and 86%, respectively.
- Zhou, Xiantai,Ji, Hongbing
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p. 2103 - 2108,6
(2020/09/09)
-
- Fluorinated organocatalysts for the enantioselective epoxidation of enals: Molecular preorganisation by the fluorine-iminium ion Gauche effect
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The fluorine-iminium ion gauche effect is triggered upon union of a secondary β-fluoroamine and an α,β-unsaturated aldehyde, providing a useful strategy for controlling the molecular topology of intermediates that are central to organocatalytic processes. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes. A process of structural editing has revealed that the efficiency of this catalyst is due to the (fluorodiphenyl)methyl group when it is embedded in a β-fluoroiminium motif. Epoxidations of challenging cyclic α,β-disubstituted, β,β-disubstituted and α,β,β-trisubstituted enals catalysed by 1 proceed with excellent levels of enantiocontrol (up to 98 % ee). Fluorine finesse. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes (see scheme). Application of this catalyst to challenging cyclic α,β-disubstituted enals, β,β-disubstituted enals, and an α,β,β-trisubstituted enal proceeds in a highly enantioselective fashion (up to 98 % ee). Copyright
- Tanzer, Eva-Maria,Zimmer, Lucie E.,Schweizer, W. Bernd,Gilmour, Ryan
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supporting information
p. 11334 - 11342,9
(2020/08/31)
-
- Organocatalytic asymmetric epoxidation and tandem epoxidation/Passerini reaction under eco-friendly reaction conditions
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An eco-friendly synthesis of highly functionalized epoxides and their incorporation into an organocatalytic multicomponent approach are reported. For this, a modified class of diarylprolinol silyl ethers was designed to enable high catalytic activity in an environmentally benign solvent system. The one-pot procedure showed great efficiency in promoting stereoselective multicomponent transformations in a tandem, 'green' fashion. Because of its non-residual, efficient and selective character, this synthetic design shows promise for large-scale applications in both diversity and target-oriented syntheses. The Royal Society of Chemistry 2012.
- Deobald, Anna Maria,Corrêa, Arlene G.,Rivera, Daniel G.,Paix?o, Márcio Weber
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supporting information
p. 7681 - 7684
(2013/04/24)
-
- Mechanism into selective oxidation of cinnamaldehyde using β-cyclodextrin polymer as phase-transfer catalyst
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Selective oxidation of cinnamaldehyde to benzaldehyde in the presence of bicarbonate and hydrogen peroxide and catalyzed by β-cyclodextrin polymer (β-CDP) was investigated. β-CDP was utilized as the phase-transfer catalyst in this study. The immobilized β
- Yang, Zujin,Zeng, Hui,Zhou, Xiantai,Ji, Hongbing
-
experimental part
p. 5912 - 5919
(2012/09/08)
-
- A new, simple, and mild azidolysis of vinylepoxides
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A new, simple, and mild regio-and stereocontrolled azidolysis of vinylepoxides with TMSN3/BF3 system is reported. The method appears of general value and works very well particularly in the presence of electron-poor olefins, regardless of the size of substituents on the heterocyclic ring.
- Righi, Giuliana,Manni, Livia Salvati,Bovicelli, Paolo,Pelagalli, Romina
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p. 3895 - 3896
(2011/08/09)
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- N-Heterocyclic carbene-catalyzed cascade epoxide-opening and lactonization reaction for the synthesis of dihydropyrone derivatives
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N-Heterocyclic carbene was employed as an efficient organic catalyst to catalyze a cascade epoxide-opening and lactonization reaction. This organocatalytic process could transform various readily accessible γ-epoxy-α,β-enals into dihydropyrone derivatives in good to excellent yields.
- Qi, Jing,Xie, Xingang,He, Jinmei,Zhang, Ling,Ma, Donghui,She, Xuegong
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p. 5948 - 5950
(2011/10/09)
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- Polymer-supported Oxone and tert-butyl hydroperoxide: new reagents for the epoxidation of α,β-unsaturated aldehydes and ketones
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Efficient, mild and selective epoxidation of α,β-unsaturated aldehydes and ketones was performed using polyvinylpyrrolidonesupported Oxone (Oxone/PVP) and ButOOH/PVP.
- Pourali, Ali Reza
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experimental part
p. 113 - 115
(2010/06/19)
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- Asymmetric formal trans -dihydroxylation and trans -aminohydroxylation of α,β-unsaturated aldehydes via an organocatalytic reaction cascade
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This study demonstrates the first formal asymmetric trans-dihydroxylation and trans-aminohydroxylation of α,β-unsaturated aldehydes in an organocatalytic multibond forming one-pot reaction cascade. This efficient process converts α,β-unsaturated aldehydes into optically active trans-2,3-dihydroxyaldehydes and trans-3-amino-2-hydroxyaldehydes with the aldehyde moiety protected as an acetal. The elaborated one-pot protocol proceeds via the formation of 2,3-epoxy and 2,3-aziridine aldehyde intermediates, which subsequently participate in a novel NaOMe-initiated rearrangement reaction leading to the formation of acetal protected trans-2,3-dihydroxyaldehydes and trans-3-amino-2-hydroxyaldehydes in a highly stereoselective manner. Advantageously, this multibond forming reaction cascade can be performed one-pot, thereby minimizing the number of manual operations and purification procedures required to obtain the products. Additionally, for the purpose of trans-aminohydroxylation of the α,β-unsaturated aldehydes, a new enantioselective aziridination protocol using 4-methyl-N-(tosyloxy) benzenesulfonamide as the nitrogen source has been developed. The mechanism of the formal trans-dihydroxylation and trans-aminohydroxylation of α,β-unsaturated aldehydes is elucidated by various investigations including isotopic labeling studies. Finally, the products obtained were applied in the synthesis of numerous important molecules.
- Albrecht, Lukasz,Jiang, Hao,Dickmeiss, Gustav,Gschwend, Bjoern,Hansen, Signe Grann,Jorgensen, Karl Anker
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supporting information; experimental part
p. 9188 - 9196
(2010/08/21)
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- Organocatalytic preparation of simple β-hydroxy and β-amino esters: Low catalyst loadings and gram-scale synthesis
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A combined amino- and N-heterocyclic carbene (NHC)-catalyzed one-pot reaction sequence for the synthesis of simple enantioenriched β-hydroxy and β-amino esters using commercially available catalysts at low catalyst loadings has been developed. The desired
- Jiang, Hao,Gschwend, Bjoern,Albrecht, Lukasz,Anker Jorgensen, Karl
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supporting information; experimental part
p. 5052 - 5055
(2010/12/25)
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- Oxidation catalysis of Nb(salan) complexes: Asymmetric epoxidation of allylic alcohols using aqueous hydrogen peroxide as an oxidant
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Several optically active Nb(salan) complexes were synthesized, and their oxidation catalysis was examined. A dimeric μ-oxo Nb(salan) complex that was prepared from Nb(OiPr)5 and a salan ligand was found to catalyze the asymmetric epoxidation of allylic alcohols using a urea-hydrogen peroxide adduct as an oxidant with good enantioselectivity. However, subsequent studies of the time course of this epoxidation and of the relationship between the ee of the ligand and the ee of the product indicated that the μ-oxo dimer dissociates into a monomeric species prior to epoxidation. Moreover, monomeric Nb(salan) complexes prepared in situ from Nb(OiPr)5 and salan ligands followed by water treatment were found to catalyze the epoxidation of allylic alcohols better using aqueous hydrogen peroxide in CHCl3/brine or toluene/brine solution with high enantioselectivity ranging from 83 to 95% ee, except for the reaction of cinnamyl alcohol that showed a moderate ee of 74%. This is the first example of the highly enantioselective epoxidation of allylic alcohols using aqueous hydrogen peroxide as an oxidant.
- Egami, Hiromichi,Oguma, Takuya,Katsuki, Tsutomu
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scheme or table
p. 5886 - 5895
(2010/07/05)
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- ORGANIC SALTS AND METHOD FOR PRODUCING CHIRAL ORGANIC COMPOUNDS
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The invention relates to a method for producing chiral organic compounds by asymmetric catalysis, using ionic catalysts comprising a chiral catalyst anion. The claimed method is suitable for reactions which are carried out over cationic intermediate stages, such as iminium ions or acyl pyridinium ions. The invention enables the production of chiral compounds with high ee values, that until now could only be obtained by means of costly purification methods.
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Page/Page column 9; 13
(2009/02/11)
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- Asymmetric counteranion-directed catalysis for the epoxidation of enals
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(Chemical Equation Presented) A new mode of chiral anion catalysis: A powerful chiral-counteranion strategy for catalytic asymmetric epoxidations using the newly discovered catalyst 1 has been applied to the epoxidation of α,β-unsaturated aldehydes together with tert-butyl hydroperoxide as the oxidant (see scheme). Remarkably, this system provides the corresponding epoxides in high diastereo- and enantioselectivity for both di- and trisubstituted enals.
- Wang, Xingwang,List, Benjamin
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p. 1119 - 1122
(2008/09/21)
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- Highly efficient epoxidation of electron-deficient olefins with tetrabutylammonium peroxydisulfate
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The epoxidation of α,β-unsaturated carbonyl compounds such as enones and enals was efficiently achieved with tetrabutylammonium peroxydisulfate in the presence of equimolar amounts of hydrogen peroxide and NaOH in acetonitrile or methanol at 25 °C in excellent yields. Base-sensitive substrate such as cinnamaldehyde could be successfully epoxidized in short reaction time under mild reaction conditions.
- Yang, Seung Gak,Hwang, Je Pil,Park, Min Young,Lee, Kieseung,Kim, Yong Hae
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p. 5184 - 5188
(2008/02/01)
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- Stereocontrolled synthesis of gem-difluoromethylenated goniodiols and goniothalamin epoxides based on ring-closing metathesis
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An efficient and general method to stereoselectively synthesize gem-difluoromethylenated goniodiols and goniothalamin epoxides has been developed. The introduction of a gem-difluoromethyl-containing group was achieved by the reaction of aldehydes with 3-bromo-3,3-difluoropropene in the presence of indium. The gem-difluoromethylenated α,β-unsaturated- δ-lactone moiety was constructed through the ring-closing metathesis of highly electron-deficient gew-difluoromethylenated acryloyl esters by Grubbs' II catalyst in toluene at reflux. Georg Thieme Verlag Stuttgart.
- You, Zheng-Wei,Zhang, Xingang,Qing, Feng-Ling
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p. 2535 - 2542
(2008/02/04)
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- The dihydrofuran template approach to furofuran synthesis
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Flash vacuum pyrrolysis of vinyl epoxides provides cis-dihydrofuran carboxylic esters in good yields and diastereoselectivities, which, on base-promoted epimerisation afford the complementary trans series. The compounds provide a viable template for a Lewis acid promoted cyclisation to provide the 2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane core found in the furofuran series of natural lignans. This strategy is stereodivergent and can be controlled to provide the exo-exo, exo-endo or endo-endo stereochemistries. The approach has been exemplified in syntheses of the sesamyl furofurans (±)-epiasarinin and (±)-asarinin. The Royal Society of Chemistry 2006.
- Aldous, David J.,Batsanov, Andrei S.,Yufit, Dmitrii S.,Dalenon, Anne J.,Dutton, William M.,Steel, Patrick G.
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p. 2912 - 2927
(2008/02/09)
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- Direct organocatalytic asymmetric epoxidation of α,β-unsaturated aldehydes
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The organocatalytic asymmetric epoxidation of α,β-unsaturated aldehydes with peroxides or sodium percarbonate is presented. Chiral pyrrolidine derivatives, proline and amino acid derived imidazolidinones mediate the asymmetric epoxidation of α,β-unsaturat
- Sundén, Henrik,Ibrahem, Ismail,Córdova, Armando
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- Highly facile homogeneous epoxidation of olefins using oxo-diperoxo tungstate(VI) complex as catalyst, bicarbonate as co-catalyst and hydrogen peroxide as a terminal oxidant
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Addition of a dilute acetic acid solution of 8-quinolinol to an H 2O2 solution of freshly precipitated H2WO 4·2H2O furnishes a yellow adduct [WO(O 2)2·2QOH] 1 which, on crystallization from a suitable solvent, affords orange-yellow complex [WO(O2)(QO) 2] 2. When 2 reacts stoichiometrically with olefinic compounds in a 1:1 molar ratio, the respective olefins are epoxidized and 2 is converted to the orange-red [WO2(QO)2] 3. When 1 is treated with an excess of H2O2 (greater than 6 equiv.) and PPh4Cl, an anionic light yellow complex PPh4[WO(O2)2(QO)] 4 is obtained. 4 reacts with cyclopentene (a representative olefin) in a 1:1 molar ratio producing cyclopentene oxide and itself is converted to PPh 4[WO2(O2)(QO)] 5. If the above reaction is conducted at a 1:2 molar ratio (instead of 1:1) then 2 moles of the corresponding epoxide is formed and 4 is converted to PPh4[WO 3(QO)] 6. All these peroxo complexes have remarkable catalytic efficiencies in the epoxidation of olefinic compounds when used in tandem with NaHCO3 as co-catalyst and H2O2 as oxidant in a CH3CN medium at room temperature, the method being green and economical. The catalyst 4 under the above experimental conditions shows so far unmatched efficiency in epoxidizing a wide variety of olefinic substrates. the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
- Maiti, Swarup K.,Dinda, Subhajit,Gharah, Narottam,Bhattacharyya, Ramgopal
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p. 479 - 489
(2007/10/03)
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- Highly efficient catalysts for epoxidation mediated by iminium salts
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A range of substituted dihydroisoquinolinium salts has been tested in the catalytic epoxidation of several alkenes. Catalyst loadings as low as 0.5 mol% have been used in the epoxidation of 1-phenylcyclohexene. Georg Thieme Verlag Stuttgart.
- Bulman Page, Philip C.,Buckley, Benjamin R.,Appleby, Louise F.,Alsters, Paul A.
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p. 3405 - 3411
(2007/10/03)
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- Organocatalytic asymmetric epoxidation reactions in water-alcohol solutions
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The diastereo- and enantioselective organocatalytic epoxidation of α,β-unsaturated aldehydes in aqueous solutions is presented. By the screening of the reaction conditions for the epoxidation of cinnamic aldehyde applying hydrogen peroxide as the oxidant and 2-[bis-(3,5-bis-trifluoromethyl- phenyl)-trimethylsilanyloxy-methyl]-pyrrolidine as the catalyst, a highly stereoselective reaction has been developed. The scope of the diastereo- and enantioselective organocatalytic epoxidation in aqueous solutions is documented by the asymmetric epoxidation of α,β-unsaturated aldehydes with enantioselectivities up to 96% ee. The Royal Society of Chemistry 2005.
- Zhuang, Wei,Marigo, Mauro,Jorgensen, Karl Anker
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p. 3883 - 3885
(2007/10/03)
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- Highly diastereoselective formation of 1,2,3-trisubstituted cyclopropane derivatives
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(Chemical Equation Presented) A highly diastereoselective formation of cyclopropane derivatives was reported. When the chiral phenylvinyl epoxide reacted with lithiated 2-alkyl-1,3-dithiane or lithiated alkyl carbonanion in the presence of HMPA, cyclopropanes bearing stereochemistry at all three positions on the ring were readily obtained in high yields of 80-97% and high dr values of 68:32-99:1. This reaction was supposed to be a tandem conjugation addition-epoxide opening sequence.
- Xie, Xingang,Yue, Guoren,Tang, Shouchu,Huo, Xing,Liang, Qiren,She, Xuegong,Pan, Xinfu
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p. 4057 - 4059
(2007/10/03)
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- A simple and highly selective biomimetic oxidation of alcohols and epoxides with N-bromosuccinimide in the presence of β-cyclodextrin in water
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A simple, mild and highly efficient biomimetic oxidation of various alcohols and epoxides with N-bromosuccinimide (NBS) catalyzed by β-cyclodextrin in water has been developed. A series of alcohols and epoxides were oxidized selectively at room temperature in excellent yields. This method is a direct one-pot synthesis under mild conditions using water as solvent and has many advantages over the existing methodologies.
- Krishnaveni, N. Srilakshmi,Surendra,Rao, K. Rama
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p. 346 - 350
(2007/10/03)
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- A Short Synthesis of (±)-Epiasarinin
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matrix presented Epiasarinin, an endo-endo furofuran, has been synthesized from piperonal via a five-step route with good stereocontrol. The sequence involves Darzens condensation, alkenyl epoxide-dihydrofuran rearrangement, and a Lewis acid mediated cyclization.
- Aldous, David J.,Dalencon, Anne J.,Steel, Patrick G.
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p. 1159 - 1161
(2007/10/03)
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- Catalytic olefin epoxidation with molecular oxygen over supported amidate-bridged platinum blue complexes
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The platinum complexes, [Pt4(NH3)8((CH3) 3CCONH)4]-(NO3)5 and [Pt2(NH3)4((CH3) 3CCONH)2](NO3)4, supported on a surface of silica gel, AL2O3, activated carbon, and poly-(4-vinylpyridine) are active heterogeneous catalysts for the liquid phase epoxidation of various olefins under 1 atm of dioxygen in the presence of isobutyraldehyde.
- Chen, Wanzhi,Yamada, Jun,Matsumoto, Kazuko
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- Efficient electrophilic and nucleophilic epoxidations utilizing a sulfonylperoxy radical and peroxysulfate species
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Reaction of superoxide anion radical (O2-. with o-nitrobenzenesulfonyl chloride yields a o-nitrobenzenesulfonyl peroxy radical with strong oxidizing ability, which is capable of oxidizing aryl methylene moieties to aryl ketones and relatively electron-rich alkenes regioselectively to epoxides. The oxidizing species is tentatively attributed to the o-nitrobenzenesulfonyl peroxy radical of structure 1. Tetrabutylammonium peroxydisulfate (TBA)2S2O8, 2) was prepared by the reaction of tetrabutylammonium hydrogen sulfate with potassium peroxydisulfate. The epoxidation of enals and enones, such as α,β-unsaturated aldehydes or ketones, was efficiently achieved with 2 in the presence of hydrogen peroxide and base in acetonitrile or in methanol at 25°C. A base-sensitive substrate, such as cinnamaldehyde, could be successfully epoxidized under mild reaction conditions and in short reaction time.
- Park, Min Young,Yang, Seung Gak,Kim, Yong Hae
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p. 431 - 436
(2007/10/03)
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- Epoxidation of olefins with peracid at low temperature with copper catalysis
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Treatment of a wide range of olefins with m-chloroperbenzoic acid (MCPBA) at low temperature in the presence of copper(I) and (II) catalysts in methylene chloride provides epoxides in good to excellent yields. (C) 2000 Elsevier Science Ltd.
- Andrus, Merritt B.,Poehlein, Benjamin W.
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p. 1013 - 1014
(2007/10/03)
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- Stereoselective synthesis of 2, 6-disubstituted-3, 7-dioxabicyclo[3.3.0]octanes
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Dihydrofurans bearing a 3-hydroxymethyl group may be efficiently combined with aldehyde dimethylacetals to provide functionalised 2, 6-disubstituted-3, 7-dioxabicyclo[3.3.0]octanes in a one pot procedure with high stereocontrol. Thieme Stuttgart-.
- Aldous, David J.,Dutton, William M.,Steel, Patrick G.
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p. 474 - 476
(2007/10/03)
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- Stereocontrolled access to polyenol ethers by conjugate elimination/ring fission reactions
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Conjugate elimination reactions are able to transform dienic acetals into the corresponding trienol diethers and efficiently convert γ-alkoxy α,β-unsaturated epoxides into hydroxy dienol ethers.
- Lancois, David,Maddaluno, Jacques
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p. 2335 - 2338
(2007/10/03)
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- KF adsorbed on alumina effectively promotes the epoxidation of electron deficient alkenes by anhydrous t-BuOOH
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KF adsorbed on alumina (KF-Al2O3) has been studied in detail for the epoxidation of electron deficient alkenes with anhydrous t-BuOOH. Aqueous base sensitive functional groups survive the reagent. Cyclopentenones are oxidized in decent to quantitative yields without showing any observable aldol products. α,β,γ,δ-Dienones are regioselectively oxidized at the α,β-position. Unlike aqueous alkaline H2O2, KF-Al2O3 is non-stereospecific and offers a mixture of cis and trans oxides from most acyclic enones. Except for the oxidation of α,β-unsaturated lactones and for the difference in reaction rates, the present reagent is, in general, similar to the t-BuOOH-DBU combination.
- Yadav,Kapoor
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p. 3659 - 3668
(2007/10/03)
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