- Aracyl triflates as derivatizing agents for biological betaines
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Several trifluoromethanesulfonates of general structure ArCOCH 2OTf were prepared and their suitability for use as derivatizing agents for the HPLC analysis of betaines was assessed. Four of them (Ar=2′-naphthyl, 2′-fluorenyl, 6′-methoxynaphtha
- Happer, D. Alan R.,Hayman, Colin M.,Storer, Malina K.,Lever, Michael
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- Selective conversion of primary amides to esters promoted by KHSO4
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Primary amides, either aliphatic or aromatic, are easily converted to the corresponding esters via reflux in lower primary alcohols in the presence of KHSO4. Secondary amides lead to complicated mixtures under analogous conditions, whereastertiary amides were inert. Use of isopropyl alcohol resulted inthe formation of product atslower rate and lower yieldalong withside products, whereas, use of tertiary alcoholsdid not give successful conversion andallyl and benzyl alcohol provided complex mixtures.
- Sattenapally, Narsimha,Sharma, Jhanvi,Hou, Yuqing
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p. 174 - 183
(2018/09/10)
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- Hybrid Catalysis Enabling Room-Temperature Hydrogen Gas Release from N-Heterocycles and Tetrahydronaphthalenes
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Hybrid catalyst systems to achieve acceptorless dehydrogenation of N-heterocycles and tetrahydronaphthalenes-model substrates for liquid organic hydrogen carriers-were developed. A binary hybrid catalysis comprising an acridinium photoredox catalyst and a Pd metal catalyst was effective for the dehydrogenation of N-heterocycles, whereas a ternary hybrid catalysis comprising an acridinium photoredox catalyst, a Pd metal catalyst, and a thiophosphoric imide organocatalyst achieved dehydrogenation of tetrahydronaphthalenes. These hybrid catalyst systems allowed for 2 molar equiv of H2 gas release from six-membered N-heterocycles and tetrahydronaphthalenes under mild conditions, i.e., visible light irradiation at rt. The combined use of two or three different catalyst types was essential for the catalytic activity.
- Kato, Shota,Saga, Yutaka,Kojima, Masahiro,Fuse, Hiromu,Matsunaga, Shigeki,Fukatsu, Arisa,Kondo, Mio,Masaoka, Shigeyuki,Kanai, Motomu
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supporting information
p. 2204 - 2207
(2017/02/23)
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- Erbium trifluoromethanesulfonate catalyzed Friedel-Crafts acylation using aromatic carboxylic acids as acylating agents under monomode-microwave irradiation
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Erbium trifluoromethanesulfonate is found to be a good catalyst for the Friedel-Crafts acylation of arenes containing electron-donating substituents using aromatic carboxylic acids as the acylating agents under microwave irradiation. An effective, rapid and waste-free method allows the preparation of a wide range of aryl ketones in good yields and in short reaction times with minimum amounts of waste.
- Tran, Phuong Hoang,Hansen, Poul Erik,Nguyen, Hai Truong,Le, Thach Ngoc
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p. 612 - 618
(2015/02/19)
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- Palladium-Catalyzed Carbonylative Esterification of Primary Alcohols with Aryl Chlorides through Dehydroxymethylative C-C Bond Cleavage
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Aryl chlorides in the presence of Pd/C catalyst and NaF react with primary alcohols to form esters, arenes, and alkanes. In this reaction, aryl chlorides act as both oxidants and coupling partners, whereas alcohols serve as both carbonyl sources and alkoxy components of the ester products. (Formula Presented).
- Park, Hyo-Soon,Kim, Dong-Su,Jun, Chul-Ho
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p. 397 - 401
(2015/04/27)
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- Calcium and magnesium chlorides-catalyzed oxidative esterification of aromatic aldehydes
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An interesting procedure for the oxidative esterification of aromatic aldehydes has been developed. By using catalytic amount of CaCl2 or MgCl2, various methyl benzoates were isolated in good yields with hydrogen peroxide as the terminal oxidant.
- Feng, Jian-Bo,Gong, Jin-Long,Li, Qin,Wu, Xiao-Feng
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p. 1657 - 1659
(2014/03/21)
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- Facile preparation of aromatic esters from aromatic bromides with ethyl formate or DMF and molecular iodine via aryllithium
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Various aromatic bromides were treated with n-BuLi and subsequently with ethyl formate, followed by the reaction with ethanol and molecular iodine in the presence of K2CO3 to provide the corresponding aromatic ethyl esters in good yields. Moreover, aromatic bromides could be transformed into the corresponding aromatic methyl esters in good yields by the treatment with n-BuLi and subsequently with DMF, followed by the reaction with methanol, molecular iodine, and K2CO3. Some aromatics could be also converted into the corresponding aromatic esters in good yields by the treatment with n-BuLi, and subsequently with ethyl formate or DMF, followed by the reaction with molecular iodine and K2CO3. The present reactions offer a novel route for the transition-metal-free, carbon-monoxide-free, and therefore environmentally benign one-pot conversion of aromatic bromides and aromatics into aromatic esters.
- Ushijima, Sousuke,Moriyama, Katsuhiko,Togo, Hideo
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experimental part
p. 4701 - 4709
(2012/07/28)
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- An efficient photoinduced deprotection of aromatic acetals and ketals
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A novel type of photodeprotection reaction of simple aromatic acetals and ketals is described. The deprotection is highly efficient under optimized conditions. The aromatic ring confers the photoreactivity to the compounds. The efficiency of the process depends on the structure of the acetal moiety. The common minor side reaction, the photooxidation, becomes the major reaction pathway in the cases of cyclic acetals. The use of photon as only reagent makes this procedure especially attractive for acetal deprotection.
- Thevenet, Damien,Neier, Reinhard
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body text
p. 331 - 346
(2011/04/22)
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- Two methods for direct ortho-arylation of benzoic acids
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Two new palladium-catalyzed methods for the direct ortho-arylation of free benzoic acids have been developed. The first method employs stoichiometric silver acetate for iodide removal, aryl iodide as the coupling partner, and acetic acid solvent. This method is applicable to the arylation of electron-rich to moderately electron-poor benzoic acids and tolerates chloride and bromide substituents on both coupling partners. The second method involves the use of aryl chloride, cesium carbonate base, n-butyl-di-1-adamantylphosphine ligand, and DMF solvent and is suitable for both electron-rich and electron-poor benzoic acids. Mechanistic studies of the second method point to the heterolytic C-H bond cleavage as the rate-determining step.
- Chiong, Hendrich A.,Pham, Quynh-Nhu,Daugulis, Olafs
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p. 9879 - 9884
(2008/02/13)
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- Lithium bromide as a flexible, mild, and recyclable reagent for solvent-free cannizzaro, tishchenko, and meerwein-ponndorf-verley reactions
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A room temperature convenient disproportionation or reduction of aldehydes prompted by lithium bromide and triethylamine is described in a solvent-free environment. Distribution of the products to selectively direct the process toward Cannizzaro or Tishchenko reactions is controlled by the type of workup selection. The presence of hydrogen donor alcohols in the mixture completely diverts the process toward the MeerweinPonndorf-Verley reaction.
- Mojtahedi, Mohammad M.,Akbarzadeh, Elahe,Sharifi, Roholah,Abaee, M. Saeed
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p. 2791 - 2793
(2008/02/05)
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- [IrCl(cod)]2-catalyzed direct oxidative esterification of aldehydes with alcohols
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[IrCl(cod)]2 catalyzed the oxidative esterification of a variety of aldehydes with methanol as a solvent in combination with K2CO3 under mild conditions (rt, 12 h). The oxidative esterification reaction of aliphatic aldehydes also took place with olefinic alcohols as reagents in toluene under similar conditions.
- Kiyooka, Syun-ichi,Wada, Yosuke,Ueno, Mahuyu,Yokoyama, Takeshi,Yokoyama, Reiko
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p. 12695 - 12701
(2008/03/14)
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- A new and efficient route toward the preparation of diazo ketones using cyanuric chloride and diazomethane
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A new method for the preparation of diazo ketones has been developed. 2,4,6-Trichloro-1,3,5-triazine (cyanuric chloride) has been found to be an excellent coupling reagent allowing for the efficient transfer of diazomethane to a carboxylic acid. Preparation of diazo ketones using carboxylic acids and triazine reagents is considerably more convenient than classical diazo transfer protocols because water does not have to be stringently removed and the entire procedure can be carried out in one-pot. Electron deficient and neutral aryl carboxylic acids were found to give better results than electron rich or aliphatic carboxylic acids. (C) 2000 Elsevier Science Ltd.
- Forbes,Barrett,Lewis,Smith
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p. 9943 - 9947
(2007/10/03)
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- Catalytic Cyclophanes. Part XI. A Flavo-thiazolio-cyclophane as a Biomimetic Catalyst for the Preparative-Scale Electro-oxidation of Aromatic Aldehydes to Methyl Esters
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Flavo-thiazolio-cyclophane 6 was prepared on a gram scale by an 18-step synthesis (Schemes 3 and 4).This pathway involved the very efficient preparation of bromo-cyclophane 32 (37 percent yield over 13 steps), which can be readily modified to create various multiply functionalized receptors.This bromide 32 was subsequently converted into the corresponding boronic acid and connected to the 7-bromoflavin 10 (Scheme 2) via Suzuki coupling to give flavo-cyclophane 36.The thiazolium unit was then introduced after quaternization of the tertiary amino groups of 36.Flavo-thiazolio-cyclophane 6, whith both prosthetic groups attached in proximity to the well-defined cyclophane binding site, is a functional model for the enzyme pyruvate oxidase.In basic methanolic solution, 6 catalyzes the oxidation of aromatic aldehydes to their corresponding methyl esters.Cyclophane 6 shows saturation kinetics, and the turnover number calculated for the oxidation of naphthalene-2-carbaldehyde to methyl naphthalene-2-carboxylate (kcat=0.22 s-1) is one of the highest reported for an artificial enzyme.Control experiments showed that the catalytic advantages of 6 result from the macrocyclic binding and reaction site as well as from the covalent attachment of both cofactors to this site.The catalytic cycle is completed by electrochemical re-oxidation of the reduced flavin moiety at a low working electrode potential (-0.3 V vs.Ag/AgCl), and up to ca. 100 catalytic cycles can be performed on a preparative scale.The intramolecular nature of the electron transfer from the active aldehyde intermediate to the flavin is particularly conducive to the oxidation of unreactive aldehydes.
- Mattei, Patrizio,Diederich, Francois
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p. 1555 - 1588
(2007/10/03)
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- A New Indirect Application of Aggregative Activation: Synthesis of Esters by Cobalt-Catalyzed Carbonylation of Aryl, Heterocyclic, and Vinyl Halides under Atmospheric Pressure
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Sun lamp illuminated alkoxycarbonylation of aryl, heteroaryl, and vinyl halides was performed under atmospheric pressure of CO in the presence of a cobalt catalyst in situ generated from Co(OAc)2.Illunination through a Pyrex flask was sufficient to catalyze the reaction.This process avoids the use of Co2(CO)8 and excess CH3I, which were required in the earlier procedure.A SRN1 mechanism is proposed.
- Marchal, Joel,Bodiguel, Jacques,Fort, Yves,Caubere, Paul
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p. 8336 - 8340
(2007/10/02)
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- Studies in the Cycloproparene Series: The Behaviour of Alkylidenecycloproparenes Towards Nucleophiles and Oxidizing Agents
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The alkylidenecycloproparene (1) reacts with potassium t-butoxide to give the ring-expanded heptafulvene (3).Epoxidation of (1) provides the hydroxy ketone (5) probably via the spiro epoxide (4) but carbene additions fail to give spirocycle (7).Photooxygenation of (1a,b) gives products (5), (12)-(14) and (16) which are explicable in terms of initial formation of dioxetan (10); products (13) and (14) result from 1 H-cyclopropanaphthalenone (11).By comparison (1c) provides phenanthraquinone acetal (17) in low yield.With osmium tetroxide and sodium periodate, (1a) gives benzophenone (12a) in competition with hydroxy ketone (5a) and 2,2-diphenylcyclobutanaphthalenone (20).The modes of formation of the various products are discussed.
- Buckland, Simon J.,Halton, Brian,Stang, Peter J.
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p. 845 - 854
(2007/10/02)
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- OXIDATION OF ENOL ETHERS BY METAL(VI)OXIDE DIPEROXIDES
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Alkoxy(aryl) adamantylidenes react with chromium(VI) or molybdenum(VI) oxide diperoxides in CHCl3 under argon yielding the corresponding 1,2-dioxetanes and/or carbonyl products derived from the fragmentation of the dioxetanes.The reaction most likely proceeds via preliminary epoxidation of the unsaturated substrates.
- Curci, Ruggero,Lopez, Luigi,Troisi, Luigino,Rashid, S. M. Khaledur,Schaap, A. Paul
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p. 3145 - 3148
(2007/10/02)
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- SYNTHESIS OF 1,2-DIOXETANES VIA ELECTRON-TRANSFER OXYGENATION
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Thermally stable 1,2-dioxetanes have been synthesized by the reaction of enol-ethers with tris p-bromophenylammoniumyl hexachloroantimonate via a chain oxygenation reaction involving formation of enol-ether cation radicals.
- Curci, Ruggero,Lopez, Luigi,Troisi, Luigino,Rashid, S. M. K.,Schaap, Paul A.
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p. 5319 - 5322
(2007/10/02)
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- A CONVENIENT PREPARATION OF METHYL ESTERS FROM CARBOXYLIC ACIDS
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A facile procedure for the preparation of methyl esters from carboxylic acids under neutral conditions is described.
- Mohacsi, Erno
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p. 453 - 456
(2007/10/02)
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