- Asymmetric Epoxidation of Enones Promoted by Dinuclear Magnesium Catalyst
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Asymmetric synthesis with cheaper and non-toxic alkaline earth metal catalysts is becoming an important and sustainable alternative to conventional catalytic methodologies mostly relying on precious metals. In spite of some sustainable methods for enantioselective epoxidation of enones, the development of a well-defined and efficient catalyst based on magnesium complexes for these reactions is still a challenging task. In this perspective, we present the application of chiral dinuclear magnesium complexes for asymmetric epoxidation of a broad range of electron-deficient enones. We demonstrate that the in situ generated magnesium-ProPhenol complex affords enantioenriched oxiranes in high yields and with excellent enantioselectivities (up to 99% ee). Our extensive study verifies the literature data in this area and provides a step forward to better understand the factors controlling the oxygenation process. Elaborated catalyst offers mild reaction conditions and a truly wide substrate scope. (Figure presented.).
- Jaszczewska-Adamczak, Joanna A.,Mlynarski, Jacek
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supporting information
p. 4247 - 4255
(2021/07/17)
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- Tandem Lewis acid catalysis for the conversion of alkenes to 1,2-diols in the confined space of bifunctional TiSn-Beta zeolite
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The generation of multifunctional isolated active sites in zeolite supports is an attractive method for integrating multistep sequential reactions into a single-pass tandem catalytic reaction. In this study, bifunctional TiSn-Beta zeolite was prepared by a simple and scalable post-synthesis approach, and it was utilized as an efficient heterogeneous catalyst for the tandem conversion of alkenes to 1,2-diols. The isolated Ti and Sn Lewis acid sites within the TiSn-Beta zeolite can efficiently integrate alkene epoxidation and epoxide hydration in tandem in a zeolite microreactor to achieve one-step conversion of alkenes to 1,2-diols with a high selectivity of >90%. Zeolite confinement effects result in high tandem rates of alkene epoxidation and epoxide hydration as well as high selectivity toward the desired product. Further, the novel method demonstrated herein can be employed to other tandem catalytic reactions for sustainable chemical production.
- Lei, Qifeng,Wang, Chang,Dai, Weili,Wu, Guangjun,Guan, Naijia,Hunger, Michael,Li, Landong
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p. 1176 - 1184
(2021/02/16)
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- Pyrenediones as versatile photocatalysts for oxygenation reactions with: In situ generation of hydrogen peroxide under visible light
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Pyrenediones (PYDs) are efficient photocatalysts for three oxygenation reactions: Epoxidation of electron deficient olefins, oxidative hydroxylation of organoborons, and oxidation of sulfides via in situ generation of H2O2 under visible light irradiation, using oxygen as a terminal oxidant and IPA as a solvent and a hydrogen donor.
- Zhang, Yuannian,Yang, Xin,Tang, Haidi,Liang, Dong,Wu, Jie,Huang, Dejian
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supporting information
p. 22 - 27
(2020/01/13)
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- On the ozonolysis of unsaturated tosylhydrazones as a direct approach to diazocarbonyl compounds
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The scope and limitations are described of reacting unsaturated tosylhydrazones with O3 followed by Et3N for the generation of 1,4- and 1,5-diazocarbonyl systems. Tosylhydrazones, from tosylhydrazide condensation with readily available δ- and ?-unsaturated α-ketoesters, led in the former case to a 2-pyrazoline whereas the latter cases led to α-diazo-?-ketoesters, although a terminal alkene produced a tetrahydropyridazinol. Using the ozonolysis-Et3N strategy, tosylhydrazones from cyclic enones give 2,5- and 2,6-diazoketones with aldehyde or ester functionality at the 1-position; the α-diazoaldehydes prefer the s-trans conformation, with a rotation barrier of 74 kJ mol-1 at 25 °C determined by NMR. This one-pot ozonolysis/Bamford-Stevens chemistry demonstrates both the tolerance of tosylhydrazones to ozone, and the subsequently added amine playing a dual role to directly transform the intermediate tosylhydrazone ozonides into products containing reactive diazo and ketone functionalities; such adducts are of particular value as precursors to cyclic carbonyl ylides for 1,3-dipolar cycloadditions.
- Fegheh-Hassanpour, Younes,Ebrahim, Faisal,Arif, Tanzeel,Sintim, Herman O.,Claridge, Timothy D. W.,Amin, Nader T.,Hodgson, David M.
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p. 2876 - 2884
(2018/05/03)
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- A procedure for the preparation of Ti-Beta zeolites for catalytic epoxidation with hydrogen peroxide
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Ti-Beta zeolite has been successfully prepared via a reproducible and scalable two-step post-synthesis strategy, which consists of creating vacant T sites with associated silanol groups by dealumination of H-Beta and subsequent dry impregnation of the resulting Si-Beta with titanocene dichloride. The mechanism of Ti incorporation into the framework of Beta is investigated by diffuse reflectance infrared Fourier transform (DRIFT) and multinuclear solid-state nuclear magnetic resonance (SSNMR) spectroscopy. Characterization results obtained from diffuse reflectance ultraviolet-visible (UV-vis) and X-ray photoelectron spectroscopy (XPS) reveal that the majority of incorporated Ti species exist in the form of isolated tetrahedrally coordinated Ti(iv) in the zeolite framework while a minority exists in the form of isolated octahedrally coordinated Ti(vi) at framework or extra-framework positions. The obtained Ti-Beta zeolites are highly active and selective catalysts for the epoxidation of unsaturated ketones, e.g. 2-cyclohexen-1-one, with hydrogen peroxide as an oxidant. A quasilinear correlation between the epoxidation rate and the number of framework Ti(iv) species could be drawn evidencing that these Ti(iv) species are responsible for the epoxidation activity of the Ti-Beta zeolites under study. The impact of preparation parameters and reaction conditions on the catalytic performances of the Ti-Beta zeolites in the epoxidation of unsaturated organic compounds with hydrogen peroxide is discussed in detail. the Partner Organisations 2014.
- Tang, Bo,Dai, Weili,Sun, Xiaoming,Guan, Naijia,Li, Landong,Hunger, Michael
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p. 2281 - 2291
(2014/04/17)
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- Transition-metal-catalyzed synthesis of aspergillide B: An alkyne addition strategy
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A catalytic enantioselective formal total synthesis of aspergillide B is reported. This linchpin synthesis was enabled by the development of new conditions for Zn-ProPhenol catalyzed asymmetric alkyne addition. This reaction was used in conjunction with ruthenium-catalyzed trans-hydrosilylation to affect the rapid construction of a late-stage synthetic intermediate of aspergillide B to complete a formal synthesis of aspergillide B in a highly efficient manner.
- Trost, Barry M.,Bartlett, Mark J.
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supporting information; experimental part
p. 1322 - 1325
(2012/04/23)
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- Development of Zn-prophenol-catalyzed asymmetric alkyne addition: Synthesis of chiral propargylic alcohols
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The development of a general and practical zinc-catalyzed enantioselective alkyne addition methodology is reported. The commercially available ProPhenol ligand (1) has facilitated the addition of a wide range of zinc alkynylides to aryl, aliphatic, and α,β-unsaturated aldehydes in high yield and enantioselectivity. New insights into the mechanism of this reaction have resulted in a significant reduction in reagent stoichiometry, enabling the use of precious alkynes and avoiding the use of excess dimethylzinc. The enantioenriched propargylic alcohols from this reaction serve as versatile synthetic intermediates and have enabled efficient syntheses of several complex natural products. A precious few: A general and practical zinc-catalyzed enantioselective alkyne addition methodology is reported (see scheme). New insights into the mechanism of this reaction have resulted in a significant reduction in reagent stoichiometry, enabling the use of precious alkynes and avoiding the use of excess dimethylzinc. This methodology has enabled the efficient synthesis of several complex natural products.
- Trost, Barry M.,Bartlett, Mark J.,Weiss, Andrew H.,Vonwangelin, Axel Jacobi,Chan, Vincent S.
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supporting information
p. 16498 - 16509
(2013/02/23)
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- Amino-acid-mediated epoxidation of α,β-unsaturated ketones by hydrogen peroxide in aqueous media
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Amino acids, such as arginine and lysine, can be used as an efficient catalyst in the epoxidation of α,β-unsaturated ketones with aqueous hydrogen peroxide. Up to >99% conversion was obtained in the reaction toward 11 α,β-unsaturated ketones.
- Kim, Juhyun,Jung, Suhyun,Park, Seongsoon,Park, Sojung
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experimental part
p. 2866 - 2868
(2011/06/21)
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- PYRAZOLO[1,5-A]PYRIDINES AS MARK INHIBITORS
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The invention encompasses pyrazolo[1,5-a]pyridine derivatives which selectively inhibit microtubule affinity regulating kinase (MARK) and are therefore useful for the treatment or prevention of Alzheimer's disease. Pharmaceutical compositions and methods of use are also included.
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Page/Page column 50; 91
(2010/04/03)
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- A comparison of intrazeolite and solution singlet oxygen ene reactions of allylic alcohols
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The singlet oxygen ene reactions of four allylic alcohols and for comparison an allylic ether have been examined both in solution and in zeolite Y. Bronsted acid sites in the zeolite were shown to induce decomposition of several of the allylic alcohols. Treatment of the zeolites with pyridine removed these acid sites and allowed intrazeolite reactions of the allylic alcohols without interference from decomposition. Control reactions with an allylic alcohol that is inert to decomposition provided evidence that the presence of pyridine in the zeolite labyrinth does not influence the product composition.
- Clennan, Edward L.,Zhang, Dong,Singleton, Jamie
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p. 1226 - 1232
(2008/02/09)
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- Epoxidation of electron-deficient αβ-unsatured carbonyl compounds over Keggin heteropoly compounds with acqueous H2O 2
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The epoxidation of a variety of electron-deficient α,β- unsaturated carbonyl compounds has been studied using a series of heteropoly compounds and aqueous hydrogen peroxide in acetonitrile. Among the heteropoly compounds investigated, (CTP)3VMo12O40 showed the highest catalytic performance for the epoxidation of these compounds.
- Gao, Qiang,Ding, Yong,Liu, Haitao,Suo, Jishuan
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p. 716 - 718
(2007/10/03)
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- Electrosynthesis of hydrogen peroxide in room temperature ionic liquids and in situ epoxidation of alkenes
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Hydrogen peroxide can be electrosynthesized from oxygen in [bmim][BF 4]-water and used in situ for the epoxidation of alkenes. The Royal Society of Chemistry 2005.
- Tang, Michael Chi-Yung,Wong, Kwok-Yin,Chan, Tak Hang
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p. 1345 - 1347
(2008/09/17)
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- Sustainable Epoxidation of Electron-Poor Olefins with Hydrogen Peroxide in Ionic Liquids and Recovery of the Products with Supercritical CO2
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An efficient procedure is described for the epoxidation of electron-deficient olefins, in particular Vitamin K3 and analogues, with aqueous basic solutions of hydrogen peroxide in different ambient temperature ionic liquids (ILs) [bmim+][X-] {[bmim +] = 1-butyl-3-methylimidazolium; [X-] = [BF 4-], [CF3SO3-], [PF 6-], [N(CF3SO2)2 -]}. Various factors affecting epoxide yield (in the range 80-99%), reaction rate and reproducibility have been examined. The almost quantitative extraction of the epoxides from the reaction media has been obtained with supercritical CO2. The ionic liquid was then recovered and reused in subsequent cycles. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Bortolini, Olga,Campestrini, Sandro,Conte, Valeria,Fantin, Giancarlo,Fogagnolo, Marco,Maietti, Silvia
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p. 4804 - 4809
(2007/10/03)
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- Synthesis of alkylated iridolactone analogs
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Bicyclic δ-lactones, iridolactones analogs with an alkyl group at the bicyclic junction, are obtained from α-alkyl-α-hydroxymethylcyclopentanones via an intramolecular Horner-Wadsworth-Emmons reaction.
- Guerrab, Zineb,Daou, Boujemaa,Fkih-Tetouani, Souad,Ahmar, Mohammed,Cazes, Bernard
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p. 5727 - 5730
(2007/10/03)
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- Highly efficient epoxidation of α,β-unsaturated ketones by hydrogen peroxide with a base hydrotalcite catalyst prepared from metal oxides
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The base hydrotalcite, prepared from MgO and Al2O3, acted as a highly efficient catalyst for the epoxidation of α,β-unsaturated ketones using aqueous hydrogen peroxide as an oxidant. This heterogeneous epoxidation has the advantages of a high efficiency of H2O2 utilization without organic solvents, a simple workup procedure, and reusability of the hydrotalcite catalyst.
- Honma, Takayuki,Nakajo, Michiko,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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p. 6229 - 6232
(2007/10/03)
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- Preparation of 2,3-epoxycycloalkanones from bicyclo[n.1.0]Alkan-1-ols
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Copper- or iron-catalyzed oxidative rearrangement of bicyclo[n.1.0]alkan-1-ols yields 3-hydroperoxycycloalkanones and/or bicyclic peroxyhemiketals, which are transformed into 2,3-epoxycycloalkanones by treatment with a base.
- Barnier,Morisson,Blanco
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p. 349 - 357
(2007/10/03)
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- Epoxidation of α,β-Unsaturated Ketones Using Hydrogen Peroxide in the Presence of Basic Hydrotalcite Catalysts
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The basic layered hydrotalcites have been used as catalysts for the epoxidation of α,β-unsaturated ketones in heterogeneous reaction media using hydrogen peroxide as an oxidant. A wide variety of α,β-unsaturated ketones were oxidized to the corresponding epoxyketones in excellent yields under mild reaction conditions. For example, 2-cyclohexen-1-one gave 2,3-epoxycyclohexanone in 91% yield at 40°C for 5 h with high efficiency in hydrogen peroxide. The catalytic activity of the hydrotalcites increased as the basicity of their surfaces increased. In the case of the epoxidation of less reactive substrates, adding a cationic surfactant such as n-dodecyltrimethylammonium bromide (DTMAB) to the above oxidation system accelerated the epoxidation reaction. These hydrotalcite catalysts were easily separated from the reaction mixture and were reusable.
- Yamaguchi, Kazuya,Mori, Kohsuke,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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p. 6897 - 6903
(2007/10/03)
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- An easy deoxygenation of conjugated epoxides
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An easy and high yielding transformation of epoxyketones and phenyl substituted epoxides to trans olefins in a convergent diastereoselective process is reported. The method was applied to the selective C-25 hydroxy- functionalisation of 3-keio-Δ4-cholestan-3-one, a key intermediate for the synthesis of C-25 hydroxy vitamin D3. (C) 2000 Elsevier Science Ltd.
- Righi, Giuliana,Bovicelli, Paolo,Sperandio, Anna
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p. 1733 - 1737
(2007/10/03)
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- Lithium naphthalenide induced reductive cleavage of α,β-epoxy ketones: An efficient procedure for the preparation of β-hydroxy ketones
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Lithium naphthalenide presents itself as a mild and efficient reagent for the cleavage of α,β-epoxy ketones to give the corresponding β-hydroxy ketones in good yields.
- Jankowska, Renata,Mhehe, George L.,Liu, Hsing-Jang
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p. 1581 - 1582
(2007/10/03)
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- Highly chemo- and regioselective rearrangement of α,β-epoxy ketones to 1,3-dicarbonyl compounds in 5 mol dm-3 lithium perchlorate-diethyl ether medium
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Epoxides from α,β-unsaturated ketones undergo highly chemo- and regioselective rearrangement to 1,3-dicarbonyl compounds in 5 mol dm-3 lithium perchlorate-diethyl ether medium by a 1,2-migration of the carbonyl group at ambient conditions. The Royal Society of Chemistry 1999.
- Sankararaman,Ncsakumar
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p. 3173 - 3175
(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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- 1,8-diazabicyclo[5.4.0]undec-7-ene: A remarkable base in the epoxidation of α,β-unsaturated-δ-lactones and other enones with anhydrous t-BuOOH
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1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) has been studied for the epoxidation of electron deficient alkenes with anhydrous t-BuOOH (TBHP) in dichloroethane. Steric demands are higher than that for alkaline H2O2 DBU is recognised as a remarkable base in these oxidations as other bases such as triethyl amine, diisopropylethyl amine, and 1,4-diazabicyclo[2.2.2]octane (DABCO) are absolutely inefficient. DBU is effective in promoting the oxidation of α,β-unsaturated δ-lactones where most of conventional methods either fail or perform poor.
- Yadav,Kapoor
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p. 8573 - 8584
(2007/10/02)
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- The reaction of trialkylstannylmethyllithium with α,β-epoxy ketones and α-chloro ketones
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The reactions of trialkylstannylmethyllithium with α,β-epoxy ketones afforded mainly cyclopropanols, while α-chloro ketones afforded allyl alcohols and/or cyclopropanols, in varying amounts depending upon the molar ratio of the reagent to the substrate.
- Sato, Tadashi,Kikuchi, Toshihiro,Tsujita, Hiroshi,Kaetsu, Atsushi,Sootome, Norio,Nishida, Ken-Ichiro,Tachibana, Kazutaka,Murayama, Eigoro
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p. 3281 - 3304
(2007/10/02)
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- Olefin Epoxidation Using Elemental Fluorine
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F2 reacts with water and CH3CN, apparently to produce the relatively stable complex HOF*CH3CN.This is probably the best known oxygen-transfer reagent and can epoxidize olefins quickly and efficiently.Various types of alkenes including aliphatic, benzylic, enones, dienones, maleates, and fumarates have been examined, and all react with the reagent to produce the corresponding mono- or diepoxides in good to excellent yields.This epoxidation is fully stereospecific, and the configuration of the starting olefin is fully retained in the resulting oxirane.In cases where exceptionally stable oxocarbocations can be formed as in 1,1-diphenylethene, the reaction produces vicinal glycols in good yields.Since the origin of the epoxides' oxygen is in the water, this method is very suitable for introducing the isotopes 17O and 18O in various molecules.
- Rozen, Shlomo,Kol, Moshe
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p. 5155 - 5159
(2007/10/02)
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- NOVEL TRANSFORMATIONS WITH BORONTRIFLUORIDE ETHERATE/IODIDE ION : FACILE CONVERSION OF 2-KETOOXIRANES AND 2-BROMO-2-ENONES TO THE α,β-UNSATURATED CARBONYL COMPOUNDS.
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Borontrifluoride etherate/iodide ion rapidly deoxygenates α-ketooxiranes, 3, to the corresponding α,β-unsaturated carbonyl compounds, 4, in near quantitative yields.In contrast, the reaction of 3 with borontrifluoride etherate/bromide ion, 2, yielded the corresponding 2-bromo-2-enone derivatives, 5, in excellent yields.The reagent 1, also dehalogenates a variety of 2-bromo-2-enones, 5, to the corresponding 2-en-1-one derivatives, 4, in high yields.
- Mandal, Arun K.,Mahajan, S. W.
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p. 2293 - 2300
(2007/10/02)
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- Fluoride-promoted Epoxidation of α,β-Unsaturated Compounds
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The epoxidation of α,β-unsaturated compounds using tetrabutylammonium fluoride is described.This method has been demonstrated to be directly applicable to base-sensitive substrates such as cinnamaldehyde and α-phenylcinnamonitrile.
- Miyashita, Masaaki,Suzuki, Toshio,Yoshikoshi, Akira
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p. 285 - 288
(2007/10/02)
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- Efficient Stereocontrolled Total Syntheses of Racemic and Natural Brefeldin-A
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Brefeldin-A, an antiobiotic fungal metabolite, has been obtained in both racemic and natural forms through a direct approach that employs norbornenone and 6-heptyn-2-ol as the basic starting materials.
- Drian, Claude Le,Greene, Andrew E.
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p. 5473 - 5483
(2007/10/02)
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- Synthesis of some bicyclooct-5-en-2-ones and bicyclooctan-2-ones. Rearrangement accompanying oxidative decarboxylation with lead tetraacetate
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1-Methoxy-2-methyl-1,4-cyclohexadiene (3), 2-methoxy-1-methyl-1,3-cyclohexadiene (2), and 2-methoxy-1,5,5-trimethyl-1,3-cyclohexadiene (14) on heating with maleic anhydride give 1-methoxy-endo-7-methylbicyclooct-5-ene-syn-2,3-dicarboxylic acid anhydride (7) and its 6-methoxy-1-methyl (16a) and 6-methoxy-1,8,8-trimethyl (16b) analogues, respectively.On hydrolysis 16a and 16b give the corresponding keto dicarboxylic acids, 18a and 18b, via keto anhydrides 17a and 17b.Treatment of 18b with lead tetraacetate gives 1,8,8-trimethylbicyclooct-5-en-2-one (19) together with products in which rearrangement to a bicyclooctane system has occured.Treatment of 17b with bis(triphenylphosphino)nickel dicarbonyl gives only 19; similar treatment of 17a gives 1-methylbicyclooct-5-en-2-one (1).Reaction of bicyclooctane-2,3-dione (27) with methyllithium gives 3-hydroxy-3-methylbicyclooctan-2-one (28), its dimer 31, and a diol 30.Treatment of 5-exo-acetoxy-1,5-endo-dimethyl-6-oxobicyclooctane-anti-2,3-dicarboxylic acid (37) with lead tetraacetate gives 3-endo-acetoxy-1,3-exo-dimethylbicyclooct-5-en-2-one (33) as a minor product; the major product is derived by rearrangement to a bicyclooctane system.It is proposed that this rearrangement, like that of 18b, involves oxidative decarboxylation of a single carboxylic acid group to give a carbonium ion that undergoes rearrangement via a 1,2-acyl migration.
- Yates, Peter,Langford, Gordon E.
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p. 344 - 355
(2007/10/02)
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- Reaction of Epoxides with Triphenylphosphine-Thiocyanogen (TPPT): Preparation of α-Thiocyanatovinyl Ketones, vis-Dithiocyanates, and vic-Dithiocyanatohydrins
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A number of epoxides smoothly react with TPPT under mild conditions to give α-thiocyanatovinyl ketones, vic-dithiocyanates, or vic-thiocyanatohydrins, depending on the structures of the epoxides used.The reactions proceed site- and stereo-specifically, to give α-thiocyanatovinyl ketones from αβ-epoxyketones, threo-dithiocyanate from trans-epoxide, erythro-dithiocyanate from cis-epoxide, and vic-thiocyanatohydrins from 1,1-disubstituted or fused epoxides, respectively.A possible mechanism for these reactions is put forward.
- Tamura, Yasumitsu,Kawasaki, Tomomi,Yasuda, Hitoshi,Gohda, Noriko,Kita, Yasuyuki
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p. 1577 - 1581
(2007/10/02)
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