- Diphenylacetaldehyde and Its Enol: Determination of the Keto-Enol and Hydration Equilibrium Constants and the pKa's of the Aldehyde, Enol, and Hydrate. Comparison with Sterically Hindered System
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The enol isomer of diphenylacetaldehyde was generated in aqueous solution from its potassium salt, formed by treating the aldehyde, with potassium hydride, and rates of ketonization of this enol were measured at 25 deg C in perchloric acid and sodium hydroxide solutions and acetic acid and bicarbonate ion buffers.These data, coupled with rates of enolization of the aldehyde measured at 25 deg C in acetic acid buffer and sodium hydroxide solutions, lead to duplicate independent determinations of the keto-enol equilibrium constant, , , the acid dissociation constant of the enol ionizing as an oxygen acid, , , and the acid dissociation constant of the aldehyde ionizing as a carbon acid, , .The equilibrium constant for formation of the aldehyde hydrate, Kh=4.7+/-0.2, was also determined by two independent methods, and the acid dissociation constant of the hydrate ionizing as an oxygen acid, , , was evaluated from kinetic data.The unusually large values of KE and for this system are attributed to stabilization of the carbon-carbon double bonds of the enol and enolate ion by the phenyl substituents.Comparison with literature data on sterically hindered, stable, "Fuson" enols bearing mesityl substituents suggests that a substantial portion of the thermodynamic stability of Fuson enols is provided by similar phenyl group stabilization of their double bonds; the methyls of the mesityl substituents of Fuson enols, however, do appear to play a critical role in conferring kinetic stability upon these substances.
- Chiang, Y.,Kresge, A.J.,Krogh, E.T.
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- Pd(0)-catalyzed amphiphilic allylation of aldehydes with vinyl epoxide
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Under Pd(0)-Et3B catalysis, vinyl epoxide serves as a formal 3-butenyl 2-anion-1-cation equivalent, and the cation reacts with aldehydes at the α-position, and the anion, at the carbonyl carbon, furnishing 2-vinylcyclobutanols in one pot. Copyright
- Kimura, Masanari,Mukai, Ryutaro,Tamaki, Takato,Horino, Yoshikazu,Tamaru, Yoshinao
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- Palladium-Catalyzed Allenamide Carbopalladation/Allylation with Active Methine Compounds
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A palladium-catalyzed allenamide carbopalladation/allylation with active methine compounds has been developed. Various indoles and isoquinolinones bearing a quaternary carbon center were achieved with good efficiency, a broad substrate scope and good functional group tolerance. This reaction underwent cascade oxidative addition, carbopalladation, and allylic alkylation, and two new C-C bonds were formed in one pot.
- Zhu, Xiaoyi,Li, Ruibo,Yao, Hequan,Lin, Aijun
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p. 4630 - 4634
(2021/06/28)
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- B(C6F5)3-catalyzed tandem protonation/deuteration and reduction of: In situ -formed enamines
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A highly efficient B(C6F5)3-catalyzed tandem protonation/deuteration and reduction of in situ-formed enamines in the presence of water and pinacolborane was developed. Regioselective β-deuteration of tertiary amines was achieved with high chemo- and regioselectivity. D2O was used as a readily available and cheap source of deuterium. Mechanistic studies indicated that B(C6F5)3 could activate water to promote the protonation and reduction of enamines. This journal is
- Wu, Rongpei,Gao, Ke
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supporting information
p. 4032 - 4036
(2021/05/19)
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- Competition Between Cα-S and Cα-Cβ Bond Cleavage in β-Hydroxysulfoxides Cation Radicals Generated by Photoinduced Electron Transfer?
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A kinetic and product study of the 3-cyano-N-methyl-quinolinium photoinduced monoelectronic oxidation of a series of β-hydroxysulfoxides has been carried out to investigate the competition between Cα-S and Cα-Cβ bond cleavage within the corresponding cation radicals. Laser flash photolysis experiments unequivocally established the formation of sulfoxide cation radicals showing their absorption band (λmax ≈ 520?nm) and that of 3-CN-NMQ? (λmax ≈ 390?nm). Steady-state photolysis experiments suggest that, in contrast to what previously observed for alkyl phenyl sulfoxide cation radicals that exclusively undergo Cα-S bond cleavage, the presence of a β-hydroxy group makes, in some cases, the Cα-Cβ scission competitive. The factors governing this competition seem to depend on the relative stability of the fragments formed from the two bond scissions. Substitution of the β-OH group with -OMe did not dramatically change the reactivity pattern of the cation radicals thus suggesting that the observed favorable effect of the hydroxy group on the Cα-Cβ bond cleavage mainly resides on its capability to stabilize the carbocation formed upon this scission.
- Lapi, Andrea,D'Alfonso, Claudio,Del Giacco, Tiziana,Lanzalunga, Osvaldo
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p. 1310 - 1321
(2021/06/07)
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- A Bifunctional Iron Nanocomposite Catalyst for Efficient Oxidation of Alkenes to Ketones and 1,2-Diketones
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We herein report the fabrication of a bifunctional iron nanocomposite catalyst, in which two catalytically active sites of Fe-Nx and Fe phosphate, as oxidation and Lewis acid sites, were simultaneously integrated into a hierarchical N,P-dual doped porous carbon. As a bifunctional catalyst, it exhibited high efficiency for direct oxidative cleavage of alkenes into ketones or their oxidation into 1,2-diketones with a broad substrate scope and high functional group tolerance using TBHP as the oxidant in water under mild reaction conditions. Furthermore, it could be easily recovered for successive recycling without appreciable loss of activity. Mechanistic studies disclose that the direct oxidation of alkenes proceeds via the formation of an epoxide as intermediate followed by either acid-catalyzed Meinwald rearrangement to give ketones with one carbon shorter or nucleophilic ring-opening to generate 1,2-diketones in a cascade manner. This study not only opens up a fancy pathway in the rational design of Fe-N-C catalysts but also offers a simple and efficient method for accessing industrially important ketones and 1,2-diketones from alkenes in a cost-effective and environmentally benign fashion.
- Ma, Zhiming,Ren, Peng,Song, Tao,Xiao, Jianliang,Yang, Yong,Yuan, Youzhu
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p. 4617 - 4629
(2020/05/19)
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- Method for preparing substituted carbonyl compound by catalyzing pinacol rearrangement reaction through molecular sieve
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The invention discloses a method for preparing a substituted carbonyl compound by catalyzing pinacol rearrangement reaction through a molecular sieve. The method is characterized in that substituted pinacol as a substrate and toluene as solvent are subjected to a rearrangement reaction for 2-5h under the catalysis of an MCM-41, SBA-15, USY, Beta ZSM-5 or other aluminum-containing H-type acidic molecular sieve, the reaction temperature is 80-110 DEG C, the mass ratio of the substituted pinacol to the toluene to the catalyst is 100: 100: (10-50), the catalyst is filtered out after the reaction is finished, and purifying is performed to obtain a product, namely, the substituted carbonyl compound. Compared with the prior art, the method provided by the invention has the advantages of wide substrate application range, cheap catalyst, easy preparation, stability, no pollution to the environment, recyclability, realization of gram-scale preparation, and high reaction yield.
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Paragraph 0015-0020
(2020/09/12)
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- Formal [3+2] cycloaddition reactions of electron-rich aryl epoxides with alkenes under Lewis acid catalysis affording tetrasubstituted tetrahydrofurans
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We report on the regio- and stereoselective synthesis of tetrahydrofurans by reaction between epoxides and alkenes in the presence of a Lewis acid. This is an unprecedented formal [3+2] cycloaddition reaction between an epoxide and an alkene. The chemical reaction represents a very concise synthesis of tetrahydrofurans from accessible starting compounds.
- Macías-Villamizar, Víctor E.,Cuca-Suárez, Luís,Rodríguez, Santiago,González, Florenci V.
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- Silica-supported orthophosphoric acid (OPA/SiO2): preparation, characterization, and evaluation as green reusable catalyst for pinacolic rearrangement
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In this paper, we report an easy-to-prepare, cost-effective, efficient, and reusable silica-supported orthophosphoric acid (OPA) catalyst for pinacolic rearrangement. The surface properties of this catalyst were successfully characterized with the help of 31P NMR, TGA, DSC, FT-IR, titration, and microscopy. OPA, hydrogen bonded on the surface, is actually the active species and the reaction seems to occur in the liquid phase embedded in the silica support. As a consequence, the extracting solvent should be chosen with cautious to guarantee the recyclability of the catalyst. As example, pinacol rearrangement reactions were successfully realized with this catalyst and OPA/SiO2 proved to be as efficient as homogeneous orthophosphoric acid to promote the reaction of pinacol derivatives. When using dichloromethane as extracting solvent, OPA/SiO2 can be reuse up to ten times without a significant loss of activity. After ten runs, no physical damage of the catalyst has been observed by microscopy proving its suitability for such application.
- Billamboz, Muriel,Banaszak, Estelle
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p. 1029 - 1040
(2019/04/10)
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- Epoxidation of Cyclooctene Using Water as the Oxygen Atom Source at Manganese Oxide Electrocatalysts
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Epoxides are useful intermediates for the manufacture of a diverse set of chemical products. Current routes of olefin epoxidation either involve hazardous reagents or generate stoichiometric side products, leading to challenges in separation and significant waste streams. Here, we demonstrate a sustainable and safe route to epoxidize olefin substrates using water as the oxygen atom source at room temperature and ambient pressure. Manganese oxide nanoparticles (NPs) are shown to catalyze cyclooctene epoxidation with Faradaic efficiencies above 30%. Isotopic studies and detailed product analysis reveal an overall reaction in which water and cyclooctene are converted to cyclooctene oxide and hydrogen. Electrokinetic studies provide insights into the mechanism of olefin epoxidation, including an approximate first-order dependence on the substrate and water and a rate-determining step which involves the first electron transfer. We demonstrate that this new route can also achieve a cyclooctene conversion of ~50% over 4 h.
- Jin, Kyoungsuk,Maalouf, Joseph H.,Lazouski, Nikifar,Corbin, Nathan,Yang, Dengtao,Manthiram, Karthish
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supporting information
p. 6413 - 6418
(2019/05/02)
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- Electrochemically Enabled Carbohydroxylation of Alkenes with H2O and Organotrifluoroborates
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Unprecedented hydroxy-alkynylation and -alkenylation reactions of arylalkenes have been developed through electrochemically enabled addition of an organotrifluoroborate reagent and H2O across the double bond of the alkene. The use of electrochemistry to promote these oxidative alkene 1,2-difunctionalization reactions not only obviates the need for transition-metal catalysts and oxidizing reagents but also ensures high regio- and chemoselectivity to afford homopropargylic or homoallylic alcohols. The possibility of extending the electrochemical alkene difunctionalization strategy to other alkene carbo-heterofunctionalization reactions has been demonstrated.
- Xiong, Peng,Long, Hao,Song, Jinshuai,Wang, Yaohui,Li, Jian-Feng,Xu, Hai-Chao
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p. 16387 - 16391
(2018/11/23)
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- Selective ligand-free cobalt-catalysed reduction of esters to aldehydes or alcohols
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Cobalt(ii) salts combined with NaBHEt3 and eventually a base catalyse efficiently and selectively the reduction of esters to aldehydes or alcohols through hydrosilylation by using phenylsilane. Catalyst characterisation by XRD, XPS, TEM and STEM analyses indicates the materials were partially crystalline with the presence of cobalt nanoparticles. Control experiments suggested low valent Co(0) was the active catalytic species involved.
- Rysak, Vincent,Descamps-Mandine, Armel,Simon, Pardis,Blanchard, Florent,Burylo, Laurence,Trentesaux, Martine,Vandewalle, Maxence,Collière, Vincent,Agbossou-Niedercorn, Francine,Michon, Christophe
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p. 3504 - 3512
(2018/07/29)
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- Iron(III) nitrate-induced aerobic and catalytic oxidative cleavage of olefins
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Microwave-assisted catalytic oxidative cleavage of olefins using Fe(NO3)3·9H2O under O2 is reported. This reaction system is particularly effective when 9-benzylidene-9H-fluorene derivatives are used as substrates even though they are tri- and tetra-substituted olefins.
- Amaya, Toru,Fujimoto, Hayato
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supporting information
p. 2657 - 2660
(2018/06/04)
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- Selective One-Pot Three-Step Cascade Reaction: From Aromatic Aldehydes to 2,2-Diphenylethanol Derivatives
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We report herein a green and scalable one-pot, three-step, pinacol-coupling-rearrangement-reduction cascade reaction useful for the formation of 2,2-diphenylethanol derivatives. The reaction is carried out in water in the presence of a commercially available and regenerable supported acid under moderate pressure. A dozen of aromatic aldehydes have been successfully submitted to the standard protocol giving the target 2,2-diarylethanol derivatives in good yield (70-85%).
- Billamboz, Muriel,Imbs, Claire,Banaszak-Léonard, Estelle,Len, Christophe
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p. 835 - 843
(2017/06/23)
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- Rhenium complex-catalyzed Meinwald rearrangement reactions of oxiranes
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The Meinwald rearrangement reaction of oxiranes to the corresponding carbonyl compounds is efficiently catalyzed by the ReBr(CO)5 complex.
- Umeda, Rui,Muraki, Masahito,Nakamura, Yuudai,Tanaka, Tomoyuki,Kamiguchi, Kyohei,Nishiyama, Yutaka
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supporting information
p. 2393 - 2395
(2017/05/29)
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- A Versatile Iridium(III) Metallacycle Catalyst for the Effective Hydrosilylation of Carbonyl and Carboxylic Acid Derivatives
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A versatile iridium(III) metallacycle catalysed rapidly and selectively the reduction of a large array of challenging esters and carboxylic acids as well as various ketones and aldehydes. The reactions proceeded in high yields at room temperature by hydrosilylation followed by desilylation. Although the reactions of various aldehydes and ketones resulted exclusively in alcohols, the hydrosilylation of esters led to alcohols or ethers, depending on the type of substrate. Regarding the carboxylic acids, again the nature of the reagent controlled the outcome of the hydrosilylation reaction, either alcohols or aldehydes being formed.
- Corre, Yann,Rysak, Vincent,Trivelli, Xavier,Agbossou-Niedercorn, Francine,Michon, Christophe
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supporting information
p. 4820 - 4826
(2017/09/07)
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- α,α-Diarylethylene Glycols as Valuable Precursor for Synthesis of 1,1-Diarylethenes and α,α-Diaryl Acetaldehydes
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Towards assembling of diarylmethine unit present in biologically important molecules, we have developed a new Weinreb Amide (WA) based building block derived from glycolic acid. The WA functionality present in this building block permits the sequential addition of various arylmagnesium bromide reagents in a controlled manner that enables assembly of a diarylmethine unit. The developed synthetic route provides easy access to important diarylethenes and α,α-diarylethylene glycols. The synthesized α,α-diarylethylene glycols provide access to synthetically important symmetrical and unsymmetrical α,α-diaryl acetaldehydes as valuable intermediates.
- Tiwari, Praveen Kumar,Sivaraman, Balasubramaniam,Aidhen, Indrapal Singh
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supporting information
p. 3594 - 3605
(2017/07/22)
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- Reductive activation of O2 by a bioinspired Fe complex for catalytic epoxidation reactions
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Aerobic epoxidation of olefins catalyzed by iron complexes without the use of a sacrificial coreductant is unknown. We report the reductive activation of O2 by a bioinspired [(bTAML)FeIII(H2O)]- (1) complex to catalyze the epoxidation of alkenes with TONs of up to 80. Spectroscopic and kinetic evidence indicates the involvement of FeV(O) as the active oxidant during the reaction.
- Singh, Kundan K.,Gupta, Sayam Sen
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supporting information
p. 5914 - 5917
(2017/07/11)
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- Ionic Pathways in the Photochemistry of Cyclic Sulfite Esters
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The photochemistry of cyclic carbonate esters proceeds by the photochemical extrusion of carbon dioxide to give 1, 3-diradicals which produce oxiranes as well as other radical derived species. The corresponding cyclic sulfite esters, upon irradiation, give intermediates that are trapped by alcohols yet generate no oxiranes. These results are consistent with ionic intermediates.
- White, Rick C.,Arney Jr, Benny E.,Perry, Jacob,Thompson, Nathan,Pithan, Phil M.,von Gradowski, Sebastian,Ihmels, Heiko
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p. 1656 - 1659
(2017/03/27)
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- Convenient method for the transformation of epoxide to aldehyde and acetonide mediated by Cr-PLM
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Chromium-pillared montmorillonite (Cr-PLM) could be synthesized and efficiently utilized for styrene oxide transformations. The target aldehyde product could be quantitatively achieved from the isomerization of styrene oxide by using 10 wt% of Cr-PLM under reflux temperature for 15 min. The acetonide product could be achieved in excellent yield from the reaction of styrene oxide and acetone by using 10 wt% of Cr-PLM under room temperature for 20 min. The catalyst could be recovered and reused at least five times without loss of activity.
- Chareonsiriwat, Laddawan,Chavasiri, Warinthorn
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p. 257 - 267
(2017/02/10)
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- Efficient epoxide isomerization within a self-assembled hexameric organic capsule
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The isomerization of epoxides to the corresponding carbonyl compounds is efficiently catalyzed by the supramolecular organic nano-capsule formed by the self-assembly of six resorcin[4]arene units. The capsule provides a combination of weak Br?nsted acidity and a suitable nano-environment that favors the metal-free isomerization reaction.
- Caneva, Thomas,Sperni, Laura,Strukul, Giorgio,Scarso, Alessandro
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p. 83505 - 83509
(2016/11/01)
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- Anti-Markovnikov Oxidation of β-Alkyl Styrenes with H2O as the Terminal Oxidant
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Oxygenation of alkenes is one of the most straightforward routes for the construction of carbonyl compounds. Wacker oxidation provides a broadly useful strategy to convert the mineral oil into higher value-added carbonyl chemicals. However, the conventional Wacker chemistry remains problematic, such as the poor activity for internal alkenes, the lack of anti-Markovnikov regioselectivity, and the high cost and chemical waste resulted from noble metal catalysts and stoichiometric oxidant. Here, we describe an unprecedented dehydrogenative oxygenation of β-alkyl styrenes and their derivatives with water under external-oxidant-free conditions by utilizing the synergistic effect of photocatalysis and proton-reduction catalysis that can address these challenges. This dual catalytic system possesses the single anti-Markovnikov selectivity due to the property of the visible-light-induced alkene radical cation intermediate.
- Zhang, Guoting,Hu, Xia,Chiang, Chien-Wei,Yi, Hong,Pei, Pengkun,Singh, Atul K.,Lei, Aiwen
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supporting information
p. 12037 - 12040
(2016/09/28)
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- Acceleration of acid-catalyzed hydrolysis in a biphasic system by sodium tetracyanocyclopentadienides
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The hydrolysis of tert-butyldimethylsilyl L-menthyl ether (3) in a CH2Cl2-1 M HCl biphasic solvent system was accelerated by the addition of sodium tetracyanocyclopentadienides 1. Particularly, the reaction rate was enhanced using sodium salt 1a-c with a lipophilic substituent on the cyclopentadienide ring. From the results obtained by a triphasic experiment, hydrolysis proceeds via the formation of hydronium ion 2 in the aqueous phase by ion exchange, followed by the transfer of 2 to the CH2Cl2 phase.
- Sakai, Takeo,Bito, Mariko,Itakura, Makoto,Sato, Honami,Mori, Yuji
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p. 930 - 934
(2016/07/13)
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- Nanoporous alumino- and borosilicate-mediated Meinwald rearrangement of epoxides
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Nanoporous alumino- and borosilicate materials, produced using an evaporation-induced self-assembly approach (EISA), efficiently catalyse the Meinwald rearrangement of epoxides in dimethyl carbonate (DMC) to produce the corresponding carbonyl compounds in high yield and excellent selectivity.
- Davies, Thomas E.,Kondrat, Simon A.,Nowicka, Ewa,Kean, Joseline L.,Harris, Christopher M.,Socci, Joseph M.,Apperley, David C.,Taylor, Stuart H.,Graham, Andrew E.
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- Multifunctional catalysis promoted by solvent effects: Ti-mcm41 for a one-pot, four-step, epoxidation-rearrangement-oxidation-decarboxylation reaction sequence on stilbenes and styrenes
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Titanium sites grafted on several siliceous supports are able to act as multifunctional catalytic centers, activating tert-butyl hydroperoxide for oxidation reactions, as redox centers, and promoting rearrangements, as Lewis acids. In the one-pot, four-step conversion of stilbene into benzophenone, the best results were obtained over Ti-MCM41. Under suitable conditions, the catalyst promotes a tandem sequence: alkene epoxidation, epoxide rearrangement, aldehyde oxidation, and oxidative decarboxylation. α,α,α-Trifluorotoluene and a fluorinated glycerol-derived solvent were the optimal solvents for this tandem process, due to their polar aprotic character that allows the efficient oxidation reactions and a poor coordinating ability to prevent any deactivation of the Lewis acid character of the sites. The result of the tandem sequence of reactions is a ketone with loss of a carbon atom that, depending on the starting alkene, is the same result as that of an ozonolysis but under safer and milder conditions. Interesting and new insights on the mechanism of the different reactions involved are also described.
- Fraile, José M.,García, Nuria,Mayoral, José A.,Santomauro, Fabio G.,Guidotti, Matteo
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p. 3552 - 3561
(2015/06/16)
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- Complexes of (η6-benzene)ruthenium(ii) with 1,4-bis(phenylthio/seleno-methyl)-1,2,3-triazoles: synthesis, structure and applications in catalytic activation of oxidation and transfer hydrogenation
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1,4-Bis(phenylthio/seleno methyl)-1,2,3-triazoles (L1-L4) synthesized by a 'Click' reaction react with [{(η6-C6H6)RuCl(μ-Cl)}]2 and NH4PF6 resulting in complexes [(η6-C6H6)RuClL]PF6 (1-4 for L = L1-L4) in which the ligands coordinate in a bidentate mode through S/Se and N of triazole. The CH2EPh (E = S or Se) attached to nitrogen of triazole remains pendent. Ligands and complexes have been authenticated with multinuclei NMR, IR and HR-MS. Single crystal structures of complexes 1-4 have been solved. The Ru-S and Ru-Se bond lengths (?) are respectively 2.388(2)/2.3902(19) and 2.5007(4)/2.5262(19). The disposition of benzene ring, N, S/Se and Cl around Ru is of a piano stool type. For catalytic oxidation of alcohols [Oppenauer-type and with N-methylmorpholine-N-oxide (NMO)] and transfer hydrogenation (TH) of carbonyl compounds [with 2-propanol and glycerol] all the four complexes have been found efficient. The optimum catalyst loadings (in mol%) are: 0.01 (NMO), 0.1 (Oppenauer), 0.01 (TH with 2-propanol) and 0.5 (TH with glycerol). Interestingly, time profiles (under optimum conditions) of two catalytic oxidations and TH's are almost similar, suggesting that they are competitive on appropriate catalyst loading. DFT calculations are consistent with somewhat low reactivity of 1 in comparison to those of 2-4.
- Saleem, Fariha,Rao, Gyandshwar K.,Kumar, Satyendra,Singh, Mahabir Pratap,Singh, Ajai K.
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p. 19141 - 19152
(2015/11/17)
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- A mild access to chiral syn 1,2-diaryl glycols by stereoselective ring opening of ortho substituted trans 2,3-diaryl-oxiranes using Amberlyst 15 in H2O/THF system
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Amberlyst 15 was an efficient and green catalyst for the reaction of 2,3-diaryloxiranes with H2O in organic co-solvent to prepare glycols in high yield. Ortho substituted trans 2,3-diaryloxiranes afforded the corresponding syn glycols stereo- and enantiospecifically. Stereoselectivity appeared related to the coordination ability of the substituents, irrespective of their electronic properties. Indeed o-OCH3 and o-OBn substituted syn glycols were obtained in high stereochemical ratios (6/1 and 10/1, respectively), and o-OTIPS and o-NO2 substituted ones were obtained as exclusive products, with the same ee of the parent epoxides.
- Lupattelli, Paolo,Chiummiento, Lucia,Funicello, Maria,Tramutola, Francesco,Marmo, Antonella,Gliubizzi, Natascia,Tofani, Daniela
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p. 5662 - 5668
(2015/08/03)
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- Catalytic, regioselective, and green methods for rearrangement of 1,2-diaryl epoxides to carbonyl compounds employing metallic triflates, Br?nsted-acidic ionic liquids (ILs), and IL/microwave; experimental and computational substituent effect study on aryl versus hydrogen migration
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The Lewis-acid catalyzed rearrangement of parent trans-stilbene oxide 1 was studied with M(OTf)3/DCM and M(OTf)3/[BMIM][BF4] (M = Bi, Al, Ga, Sc, and Yb; [BMIM] = butylmethylimidazolium) and Zn(NTf2)2, and with Bi(OTf)3/[BMIM][X] (X = NTf2, OTf, PF6, and BF4), employing 5 mol% of catalyst. Selective formation of 2,2-dipheylacetaldehyde 2 (phenyl migration product) was observed in all cases, with Bi(OTf)3 proving most efficient. The rearrangement of 1 was also effected in [BMIM][X] (X = NTf2, OTf, PF6, and BF4) without an added catalyst under microwave MW irradiation, and X = PF6 gave the highest yield and selectivity. Efficient and selective rearrangement of 1-2 was also observed with 0.1-0.3equiv. of [BMIM(SO3H)][OTf] in DCM and in [BMIM][X]. A substituent effect study was performed with a series of singly substituted 1,2-diphenyl oxiranes (with X = OMe, Me, F, CN, and NO2) with 5mol% Bi(OTf)3 in DCM and in [BMIM][NTf2]. Notable formation of ketones was observed with the NO2 and CN derivatives. Competing formation of ketones was also observed in [BMIM][PF6] under MW and under Br?nsted acid catalysis with [BMIM(SO3H)][OTf] in DCM and in [BMIM][NTf2]. The aryl versus H migration was studied computationally by DFT and MP2 methods and by including solvation effects (IEFPCM).
- Jamalian, Arezu,Rathman, Benjamin,Borosky, Gabriela L.,Laali, Kenneth K.
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- An air-stable cationic iridium hydride as a highly active and general catalyst for the isomerization of terminal epoxides
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We describe the use of an air-stable iridium hydride catalyst for the isomerization of terminal epoxides into aldehydes with perfect regioselectivity. The system operates at low loadings of catalyst (0.5 mol%), is highly practical, scalable, and tolerates functional groups that would not be compatible with Lewis acids typically used in stoichiometric amounts. Evidence for a rare hydride mechanism are provided. This journal is the Partner Organisations 2014.
- Humbert, Nicolas,Vyas, Devendra J.,Besnard, Céline,Mazet, Clément
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supporting information
p. 10592 - 10595
(2014/10/15)
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- Catalysed anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and transformation of methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant
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Anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and transformation of N-methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant under mild conditions have been achieved with moderate to good product yields using [FeIII(TF4DMAP)OTf] as catalyst. This journal is
- Du, Yi-Dan,Tse, Chun-Wai,Xu, Zhen-Jiang,Liu, Yungen,Che, Chi-Ming
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supporting information
p. 12669 - 12672
(2015/05/20)
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- Fukuyama reduction and integrated thioesterification/fukuyama reduction of thioesters and acyl chlorides using continuous flow
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Fukuyama reduction of thioesters has been achieved using a polymer-supported Pd[0] catalyst (Pd/XAD-4), and continuous flow conditions. The generality of this reaction is good with a range of aldehydes prepared in excellent yields. In addition, an integrated multistep thioesterfication/ Fukuyama reduction has been developed that allows acyl chlorides to be directly converted to the corresponding aldehydes. Integral to this process is the use of polymer-supported amine and isocyanate reagents to achieve thioesterification and scavenge unreacted thiol. In addition, catch-and-release purification has been employed to enable isolation of the aldehyde from silylthioether byproducts without the need for chromatographic purification.
- Asadi, Mousa,Bonke, Shannon,Polyzos, Anastasios,Lupton, David W.
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p. 2070 - 2074
(2014/06/24)
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- Investigation of axial ligand effects on catalytic activity of manganese porphyrin, evidence for the importance of hydrogen bonding in cytochrome-P450 model reactions
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Various nitrogenous bases, such as imidazoles, pyridines and amines were employed as axial ligands in epoxidation reaction of cyclooctene bytetra-n-butylammonium hydrogen monopersulfate (n-Bu4NHSO5), in the presence of Mn(III)-tetrakis(2,3-dimethoxyphenyl)porphyrin-acetate (T(2,3-OMeP)PorMnOAc). T(2,3-OMeP)PorMnOAc is a fairly stable catalyst, with the ability of producing hydrogen bonding. High epoxidation yield of 85 ± 6% was obtained in the presence of imidazole axial ligand with 100% selectivity in 30 min. Higher conversion of around 100% was obtained by pyridine axial base, while selectivity was reduced to 69%. Further epoxidation reactions were also performed using Mn(III)-Tetrakis(2,3-dihydroxyphenyl)porphyrin-acetate (T(2,3-OHP)PorMnOAc) as catalyst. In addition to the usual electronic and steric effects, it is proposed that the catalytic activity depends on the existence and kind of hydrogen bonding between the axial base and the ortho-methoxy or hydroxy groups on the phenyl rings of manganese porphyrin. The cis to trans ratio of cis-stilbene oxide formed by imidazole and pyridine axial bases were obtained as 7.5 and 2.5 respectively. In addition GC-Ms and UV-vis studies were employed to find the nature of active species and product formation. Our DFT calculations disclosed that pyridine hydrogen bonding with moiety of the macrocycle rings strongly affects the relative energies of S/Q spin states in [T(2,3-OMeP)PorMnV(O)(Py)]+, in that it results in the longer Mn-O bond and reactivity toward substrates.
- Mesbahi, Elnaz,Safari, Nasser,Gheidi, Mahin
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p. 354 - 365
(2015/05/20)
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- Catalytic, regioselective, and green methods for rearrangement of 1,2-diaryl epoxides to carbonyl compounds employing metallic triflates, Br?nsted-acidic ionic liquids (ILs), and IL/microwave; Experimental and computational substituent effect study on aryl versus hydrogen migration
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The Lewis-acid catalyzed rearrangement of parent trans-stilbene oxide 1 was studied with M(OTf)3/DCM and M(OTf)3/[BMIM][BF 4] (M = Bi, Al, Ga, Sc, and Yb; [BMIM] = butylmethylimidazolium) and Zn(NTf2)2, and with Bi(OTf)3/[BMIM][X] (X = NTf2, OTf, PF6, and BF4), employing 5 mol% of catalyst. Selective formation of 2,2-dipheylacetaldehyde 2 (phenyl migration product) was observed in all cases, with Bi(OTf)3 proving most efficient. The rearrangement of 1 was also effected in [BMIM][X] (X = NTf 2, OTf, PF6, and BF4) without an added catalyst under microwave MW irradiation, and X = PF6 gave the highest yield and selectivity. Efficient and selective rearrangement of 1-2 was also observed with 0.1-0.3 equiv. of [BMIM(SO3H)][OTf] in DCM and in [BMIM][X]. A substituent effect study was performed with a series of singly substituted 1,2-diphenyl oxiranes (with X = OMe, Me, F, CN, and NO2) with 5 mol% Bi(OTf)3 in DCM and in [BMIM][NTf2]. Notable formation of ketones was observed with the NO2 and CN derivatives. Competing formation of ketones was also observed in [BMIM][PF6] under MW and under Br?nsted acid catalysis with [BMIM(SO3H)][OTf] in DCM and in [BMIM][NTf2]. The aryl versus H migration was studied computationally by DFT and MP2 methods and by including solvation effects (IEFPCM).
- Jamalian, Arezu,Rathman, Benjamin,Borosky, Gabriela L.,Laali, Kenneth K.
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- Regioselective and stereoselective entry to β,β-disubstituted vinyl ethers via the sequential hydroboration/Suzuki-Miyaura coupling of ynol ethers
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A highly regio- and stereoselective synthesis of stereodefined β,β-disubstituted alkenyl ethers featuring the sequential hydroboration/Suzuki-Miyaura coupling of ynol ethers has been described. A number of functional groups, including OMe, Ac, CO2Et, CN, halides, and alkyl, (hetero)aryl, and alkenyl groups, are well-tolerated under the reaction conditions. Furthermore, it allows a facile entry to the labile diarylacetaldehydes by TFA-mediated hydrolysis of β,β-disubstituted vinyl ethers.
- Cui, Weijian,Mao, Mengyi,He, Zuying,Zhu, Gangguo
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p. 9815 - 9821
(2013/10/22)
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- Isomerization of terminal epoxides by a [Pd-H] catalyst: A combined experimental and theoretical mechanistic study
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An unusual palladium hydride complex has been shown to be a competent catalyst in the isomerization of a variety of terminal and internal epoxides. The reaction displayed broad scope and synthetic utility. Experimental and theoretical evidence are provided for an unprecedented hydride mechanism characterized by two distinct enantio-determining steps. These results hold promise for the development of an enantioselective variant of the reaction.
- Vyas, Devendra J.,Larionov, Evgeny,Besnard, Celine,Guenee, Laure,Mazet, Clement
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supporting information
p. 6177 - 6183
(2013/06/04)
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- Complementary catalytic strategies to access α-chiral aldehydes
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The present article summarizes the development of two novel and complementary catalytic methods to access α-chiral aldehydes. A C1-symmetric chiral (P,N) ligand with a structure derived from the ubiquitous binepine scaffold has been specifically designed for the Pd-catalyzed α arylation of aldehydes to access indane derivatives with a well-defined quaternary stereocenter in high yields and excellent enantioselectivities. In addition, a dinuclear palladium hydride catalyst has been synthesized for the isomerization of terminal and trisubstituted epoxides into aldehydes and ketones respectively. Combined experimental and theoretical investigations pointed to an unprecedented 'epoxide-opening/hydride-transfer' sequence. The mechanism also features two distinct enantio-determining steps in the kinetic resolution of racemic epoxides. Schweizerische Chemische Gesellschaft.
- Mazet, Clement
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p. 658 - 662
(2013/11/06)
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- Counterion effects in the preparation of aldehyde-bisulfite adducts
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The identification and development of an aldehyde-bisulfite adduct as an isolable starting material in the synthesis of the CETP inhibitor Evacetrapib are described. The physical properties of the sodium and potassium analogs are compared, and the extension of the scope of this study to include an investigation into the solid state properties of a range of sodium and potassium bisulfite adducts of commonly encountered aldehydes is discussed.
- Kissane, Marie G.,Frank, Scott A.,Rener, Gregory A.,Ley, Christopher P.,Alt, Charles A.,Stroud, Paul A.,Vaid, Radhe K.,Boini, Sathish K.,McKee, Laura A.,Vicenzi, Jeffrey T.,Stephenson, Gregory A.
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supporting information
p. 6587 - 6591
(2013/11/19)
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- Biarylphosphonite gold(I) complexes as superior catalysts for oxidative cyclization of propynyl arenes into indan-2-ones
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Striking gold: A series of variously functionalized propynyl arenes was smoothly converted into indan-2-ones by a new gold(I)-catalyzed oxidative cyclization process. [LAu]NTf2 (Tf=trifluoromethanesulfonyl) is a superior catalyst both in terms of yield and kinetics for the present transformation. Copyright
- Henrion, Guilhem,Chavas, Thomas E. J.,Le Goff, Xavier,Gagosz, Fabien
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supporting information
p. 6277 - 6282
(2013/07/11)
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- Synthesis of acyclic ketones by catalytic, bidirectional homologation of formaldehyde with nonstabilized diazoalkanes. Application of a chiral diazomethyl(pyrrolidine) in total syntheses of erythroxylon alkaloids
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This work offers a catalytic approach to convergent ketone assembly based upon formal and tandem C-H insertion of diazoalkanes in the presence of limiting amounts of monomeric formaldehyde, which is easily generated as a gas by thermolysis of the inexpensive and abundant paraformaldehyde (~30 USD/kg). The method forms di-, tri-, and even tetrasubstituted acetones with high efficiency, and it has streamlined a synthesis of (-)-dihydrocuscohygrine in which the absolute stereochemistry of a proline-based starting material is preserved. Assisted by the advent of new protocols for hydrazone oxidation, we also provide full details on handling non-carbonyl-stabilized diazo compounds.
- Wommack, Andrew J.,Kingsbury, Jason S.
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p. 10573 - 10587
(2013/11/19)
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- Organic reactivity of alcohols in superheated aqueous salt solutions: An overview
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The low dielectric constant and high self-dissociation constant of water in a temperature range between 150 and 250 °C make it a very appealing solvent for synthesis. Surprisingly, while organic chemistry in water at low temperature or around its critical point has been investigated in detail, very little seems to be known about the behaviour of organic molecules under hydrothermal conditions. The present work thus aims at shading some light on this field. As a start, we decided to investigate the reactions in which alcohols can undergo in water in the above-mentioned temperature range. Knowing that very strong salt effects on organic reactions have already been observed in super critical water, the impact of salt on the outcome of our tests was also investigated in detail.
- Avola, Sabine,Goettmann, Frederic,Antonietti, Markus,Kunz, Werner
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scheme or table
p. 1568 - 1573
(2012/10/07)
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- Tandem catalysis with a bifunctional site-isolated Lewis acid-Bronsted base metal-organic framework, NH2-MIL-101(Al)
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A metal-organic framework (MOF), NH2-MIL-101(Al), which acts as a bifunctional, site-isolated Lewis acid-Bronsted base heterogeneous catalyst, catalyzes a tandem Meinwald rearrangement-Knoevenagel condensation reaction with remarkable substrate selectivity.
- Srirambalaji, Renganathan,Hong, Soonsang,Natarajan, Ramalingam,Yoon, Minyoung,Hota, Raghunandan,Kim, Yonghwi,Ho Ko, Young,Kim, Kimoon
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supporting information
p. 11650 - 11652
(2013/01/15)
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- An alternative reaction outcome in the gold-catalyzed rearrangement of 1-alkynyloxiranes
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The gold(III)-catalyzed rearrangement of tetrasubstituted 1-alkynyloxiranes is described. This transformation led to a different reaction outcome with respect to related substrates previously studied. Thus, tertiary α-alkynylketones or alkynols can be selectively obtained. Moreover, gold(III) proved capable to catalyze the rearrangement of simple epoxides. These results indicate that gold(III) complexes act as oxophilic Lewis acids rather than π-acids in these transformations.
- Gonzalez, Maria J.,Gonzalez, Jesus,Vicente, Ruben
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supporting information
p. 6140 - 6143,4
(2020/09/16)
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- AuCl3/AgSbF6-catalyzed rapid epoxide to carbonyl rearrangement
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An efficient epoxide to carbonyl rearrangement using catalytic AuCl 3/AgSbF6 has been presented. The reactions are fast and high yielding. β-Hydrogen migration takes place exclusively when hydrogen and methyl or substituted methyl groups are present at β-carbon of epoxide. When phenyl/acetyl/benzoyl and hydrogen are available at same carbon atom, migration of the former is preferred over the latter.
- Gudla, Vanajakshi,Balamurugan, Rengarajan
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p. 5243 - 5247
(2012/11/07)
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- An electric field-induced change in the selectivity of a metal oxide-catalyzed epoxide rearrangement
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The rearrangement of cis-stilbene oxide catalyzed by Al2O 3 was studied in the presence of interfacial electric fields. Thin films of Al2O3 deposited on Si electrodes were used as the opposing walls of a reaction vessel. Application of a voltage across the electrodes engendered electrochemical double layer formation at the Al 2O3-solution interface. The aldehyde to ketone product ratio of the rearrangement was increased by up to a factor of 63 as the magnitude of the double layer charge density was increased. The results support a field-dipole effect on the selectivity of the catalytic reaction.
- Gorin, Craig F.,Beh, Eugene S.,Kanan, Matthew W.
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supporting information; experimental part
p. 186 - 189
(2012/03/07)
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- Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates
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The photochemistry of a phenyl and 1, 2-diphenyl substituted sulfite ester is reported. The performance of photoreactions under relatively mild reaction conditions enables the detection of products that have not been observed in previous studies. It is concluded that, complementary to the initially proposed carbene intermediates, diradicals may also be considered.
- White, Rick C.,Arney Jr., Benny E.,Ihmels, Heiko
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scheme or table
p. 1208 - 1212
(2012/09/22)
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- Polymer-mediated pinacol rearrangements
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Both poly(3,4-ethylenedioxythiophene) and poly(pyrrole) mediate a pinacol rearrangement of 1,2-diols. The yields of ketone or aldehyde products are comparable to those observed for treatment with mineral acids or Lewis acids. The advantage of this protocol is a two-phase reaction medium in hydrocarbon solvents that allows facile recovery of the products by simple filtration of the polymer and removal of solvents. Both the polymer and the hydrocarbon solvent may be recovered and used in subsequent reactions. Georg Thieme Verlag Stuttgart · New York.
- Pavlik, Christopher,Morton, Martha D.,Smith, Michael B.
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experimental part
p. 2191 - 2194
(2011/11/06)
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- Highly selective palladium-catalyzed direct c-h α-monoarylation of carbonyl compounds using water containing the surfactant polyoxyethylene- α-tocopheryl sebacate (PTS) as a solvent
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Highly selective direct C-H α-monoarylation reactions of 4-chromanones, ketones and 2-phenylacetaldehyde with aryl halides have been performed in satisfactory yields by using a tris(dibenzylideneacetone) dipalladium(0)/tri-tert-butylphosphine tetrafluoroborate catalyst system, potassium bicarbonate as the base and a solvent consisting of pure water containing a small amount of polyoxyethylene-α-tocopheryl sebacate (PTS). Analogous reaction conditions have been employed in a tandem process leading to phenyl-substituted isocoumarins from carbonyl compounds and methyl 2-bromobenzoate.
- Lessi, Marco,Masini, Tiziana,Nucara, Luca,Bellina, Fabio,Rossi, Renzo
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supporting information; experimental part
p. 501 - 507
(2011/04/15)
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- Aryl(chloro)methyl 4-tolyl sulfoxides: Synthesis and application to the synthesis of α-aryl ketones
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Aryl(chloro)methyl 4-tolyl sulfoxides were synthesized from arylmethyl 4-tolyl sulfoxides in moderate-to-good yields by sequential treatment with lithium diisopropylamide and tosyl chloride at low temperatures. Treatment of the lithium α-sulfinyl carbanion of the aryl(chloro)methyl 4-tolyl sulfoxides with aldehydes or ketones resulted in the formation of adducts in good-to-high yields. Treatment of these adducts with tert-butylmagnesium chloride gave the corresponding magnesium alkoxides. On treatment with isopropylmagnesium chloride, the alkoxides gave the corresponding magnesium β-oxido carbenoids, which rearranged to give α-aryl ketones in good-to-high yields. The magnesium enolate intermediates generated by rearrangement of the -oxido carbenoids could also be trapped with electrophiles to give α-aryl α-substituted ketones. These procedures offer a good method for the synthesis of a variety of α-aryl ketones from aldehydes and ketones. Georg Thieme Verlag Stuttgart. New York.
- Fukuda, Shigehiko,Tsuji, Kazuhito,Musashi, Jun,Nonaka, Ryo,Kimura, Tsutomu,Satoh, Tsuyoshi
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p. 3615 - 3626
(2011/12/16)
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- CF3CO2ZnEt-mediated highly regioselective rearrangement of bromohydrins to aldehydes
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A highly efficient and selective rearrangement reaction of bromohydrins to aldehydes mediated by CF3CO2ZnEt was described. The secondary and tertiary aldehydes were prepared under mild conditions in good to excellent yields (85-99%). The scope and limitations of this rearrangement process were also investigated.
- Wang, Zhihui,Li, Meiyi,Zhang, Wenqin,Jia, Jiangnan,Wang, Fei,Xue, Song
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supporting information; experimental part
p. 5968 - 5971
(2011/11/29)
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- Rapid and efficient protic ionic liquid-mediated pinacol rearrangements under microwave irradiation
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Several protic ionic liquids were tested as potential mediators for pinacol rearrangements employing microwave irradiation. Using hydrobenzoin as a model substrate, the optimal conditions were found to be heating at 80°C for 5 min using H2SO4:triethylamine as the ionic liquid. A key feature of this reaction was to keep the microwave power low (20 W) to avoid ionic liquid degradation. Application of these conditions to triphenylethylene glycol gave rearrangement products in high yield and purity, while phenylethylene glycol and styrene oxide gave pinacol products that underwent a cascade aldol condensation. These conditions represent an efficient means by which pinacol rearrangements can be carried out while avoiding the use of strong Bronsted acids, high temperatures and extended reaction times. The Royal Society of Chemistry.
- Henderson, Luke C.,Byrne, Nolene
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supporting information; experimental part
p. 813 - 816
(2011/06/20)
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- Gold-catalysed activation of epoxides: Application in the synthesis of bicyclic ketals
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Gold-catalysed generation of diol equivalents from epoxides and their intramolecular reaction with Ca≡C bonds to generate bicyclic ketals is presented. This reaction essentially involves the formation of an acetonide, which subsequently cyclises on the alkyne intramolecularly under gold catalysis conditions. This method could be extended to make optically pure bicyclic ketals. Deuterium incorporation experiments were carried out to ascertain the mechanism of the reaction. Sequential activation of epoxide and alkyne moieties by a gold catalyst in acetone as solvent has been achieved. This strategyhas been employed to synthesise bicyclic ketals from epoxy alkynes. Copyright
- Balamurugan, Rengarajan,Kothapalli, Raveendra Babu,Thota, Ganesh Kumar
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experimental part
p. 1557 - 1569
(2011/04/25)
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- Microwave-assisted grafting to MCM-41 silica and its application as catalyst in flow chemistry
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Finding environmentally gentle methods to graft Lewis acid on the surface of mesoporous materials is a topic of current interest. Herein we describe the optimization of a preparation procedure of a mesoporous silica-supported Er III catalyst using the microwave-assisted post-calcination functionalization of Mobil Composition of Matter-41 silica as the key step. The required time for functionalization was reduced from several hours to 10min using sealed-vessel microwave technology. Control experiments using conventional heating at the same temperature demonstrated that the rate increase is owing to a simple thermal/kinetic effect as a result of the higher reaction temperature. The resulting ErIII catalyst was tested for the first time as a catalyst in the continuous flow deprotection of benzaldehyde dimethylacetal and a complete leaching study was performed.
- Oliverio, Manuela,Procopio, Antonio,Glasnov, Toma N.,Goessler, Walter,Kappe, C. Oliver
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experimental part
p. 1522 - 1529
(2012/02/02)
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