- Imidazolium Based Fluorous N-Heterocyclic Carbenes as Effective and Recyclable Organocatalysts for Redox Esterification
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A series of new highly fluorophilic ionic liquids (f > 110) was synthetized from 3-iodopropyltris(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane and N-alkyl imidazoles, followed by anion exchange. N-heterocyclic carbenes generated in situ from obtained imidazolium salts were employed to catalyze redox esterification (umpolung) of cinnamaldehyde with alcohols. The most effective N-methyl derivative with iodide as a counter anion was studied in detail with respect to the optimization of reaction conditions, substrate scope and recyclability. Recovery of the precatalyst was achieved using either fluorous extraction or performing the reaction in suitable fluorous biphase system with direct recycling of the fluorinated precatalyst phase. For both tested options, the catalytic activity did not significantly decrease within 5 subsequent cycles. The redox esterification was shown to proceed also in supercritical carbon dioxide (scCO2) as an alternative solvent where the activity of the fluorinated catalyst was also superior to the nonfluorinated model, while retaining the benefit of easy recycling.
- ?ervenková ??astná, Lucie,Bílková, Veronika,Cézová, Tereza,Cu?ínová, Petra,Karban, Jind?ich,?ermák, Jan,Krupková, Alena,Stra?ák, Tomá?
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p. 3591 - 3598
(2020/06/17)
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- Ionic liquid catalytic synthesis of styrene-acrylic acid ester derivative of the method (by machine translation)
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The invention provides an ionic liquid catalytic synthesis of styrene-acrylic acid ester derivative of the method, the method adopts the imidazole ionic liquid as catalyst, in order to cinnamic aldehyde or its derivatives and nandrolone or testosterone alcohol or phenol derivatives as raw materials, without any additional acid and alkali, one-step reaction, to obtain the styrene-acrylic acid ester derivative. Compared with the prior art, the maximum of this invention is characterized in that the raw materials are all simple and easy to obtain, security and stability of the compound, the reaction time is short, after the reaction by simple extraction, concentration or crystallization can be obtained pure product, at the same time can also be realized in the use of the recycling of the catalyst, catalyst recycled is very convenient and almost no "wastes" problem. The invention it has less catalyst levels, the reaction selectivity is high, and the yield is high, the operation is simple, pollution is small, green high degree of several advantages; in the setting under the reaction conditions, the conversion of raw materials and the yield of the product are as high as 90% or more. (by machine translation)
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Paragraph 0031
(2019/05/08)
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- Enantio- and Diastereoselective Hydrofluorination of Enals by N-Heterocyclic Carbene Catalysis
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In contrast to well-established asymmetric hydrogenation reactions, enantioselective protonation is an orthogonal approach for creating highly valuable methine chiral centers under redox-neutral conditions. Reported here is the highly enantio- and diastereoselective hydrofluorination of enals by an asymmetric β-protonation/α-fluorination cascade catalyzed by N-heterocyclic carbenes (NHCs). The two nucleophilic sites of a homoenolate intermediate, generated from enals and an NHC, are sequentially protonated and fluorinated. The results show that controlling the relative rates of protonation, fluorination, and esterification is crucial for this transformation, and can be accomplished using a dual shuttling strategy. Structurally diverse carboxylic acid derivatives with two contiguous chiral centers are prepared in a single step with excellent d.r. and ee values.
- Wang, Leming,Jiang, Xinhang,Chen, Jiean,Huang, Yong
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supporting information
p. 7410 - 7414
(2019/05/10)
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- Oxidative Decarboxylation Enables Chemoselective, Racemization-Free Esterification: Coupling of α-Ketoacids and Alcohols Mediated by Hypervalent Iodine(III)
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An α-ketoacid could be converted into a reactive acylating agent by treatment with hypervalent iodine(III) species, and in so doing, we discovered a novel decarboxylative acylation of alcohols that affords a variety of esters in excellent yields. The esterification has been applied to a sterol bearing a free carboxylic acid and shows unique chemoselectivity. The procedure is racemization-free and operates under mild conditions.
- Nanjo, Takeshi,Kato, Natsuki,Takemoto, Yoshiji
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supporting information
p. 5766 - 5769
(2018/09/12)
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- Catalytic, Enantioselective β-Protonation through a Cooperative Activation Strategy
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The NHC-catalyzed transformation of unsaturated aldehydes into saturated esters through an organocatalytic homoenolate process has been thoroughly studied. Leveraging a unique “Umpolung”-mediated β-protonation, this process has evolved from a test bed for homoenolate reactivity to a broader platform for asymmetric catalysis. Inspired by our success in using the β-protonation process to generate enals from ynals with good E/Z selectivity, our early studies found that an asymmetric variation of this reaction was not only feasible, but also adaptable to a kinetic resolution of secondary alcohols through NHC-catalyzed acylation. In-depth analysis of this process determined that careful catalyst and solvent pairing is critical for optimal yield and selectivity; proper choice of nonpolar solvent provided improved yield through suppression of an oxidative side reaction, while employment of a cooperative catalytic approach through inclusion of a hydrogen bond donor cocatalyst significantly improved enantioselectivity.
- Wang, Michael H.,Barsoum, David,Schwamb, C. Benjamin,Cohen, Daniel T.,Goess, Brian C.,Riedrich, Matthias,Chan, Audrey,Maki, Brooks E.,Mishra, Rama K.,Scheidt, Karl A.
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p. 4689 - 4702
(2017/05/12)
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- Studies of the Electronic Effects of Zinc Cluster Catalysts and Their Application to the Transesterification of β-Keto Esters
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The electronic effects of tetranuclear zinc cluster catalysts on transesterification were investigated by changing the carboxylate ligands in the clusters. High catalyst activity crucially depended on the balance between Lewis acidity and Br?nsted basicity of the catalyst; this was consistent with the dual activation of both the electrophile and nucleophile by the cooperative zinc centers. In addition, tetranuclear zinc cluster catalysts achieved the transesterification of β-keto esters with unprecedented levels of broad substrate generality, in which a newly developed pentafluoropropionate-bridged zinc cluster and 4-dimethylaminopyridine additive greatly improved the reactivity of sterically congested α- and α,α-disubstituted β-keto esters. Lewis versus Br?nsted: High catalyst activity of zinc clusters on transesterification crucially depend on a balance between Lewis acidity and Br?nsted basicity of the catalyst. Zinc clusters, including a newly developed pentafluoropropionate-bridged zinc cluster, achieved the transesterification of β-keto esters with unprecedented levels of broad substrate generality (see figure).
- Agura, Kazushi,Hayashi, Yukiko,Wada, Mari,Nakatake, Daiki,Mashima, Kazushi,Ohshima, Takashi
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supporting information
p. 1548 - 1554
(2016/06/01)
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- A General and mild catalytic α-alkylation of unactivated esters using Alcohols
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Catalytic α-alkylation of esters with primary alcohols is a desirable process because it uses low-toxicity agents and generates water as the by-product. Reported herein is a NCP pincer/Ir catalyst which is highly efficient for α-alkylation of a broad scope of unactivated esters under mild reaction conditions. For the first time, alcohols alkylate unactivated α-substituted acyclic esters, lactones, and even methyl and ethyl acetates. This method can be applied to the synthesis of carboxylic acid derivatives with diverse structures and functional groups, some of which would be impossible to access by conventional enolate alkylations with alkyl halides. In a pinch: An NCP pincer/iridium catalyst is highly efficient for the α-alkylation of unactivated esters using alcohol under mild reaction conditions. The reaction is simple, clean, and scalable (1-10 mmol), and the scope with respect to the ester is wide.
- Guo, Le,Ma, Xiaochen,Fang, Huaquan,Jia, Xiangqing,Huang, Zheng
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supporting information
p. 4023 - 4027
(2015/03/30)
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- Oxidative enantioselective α-fluorination of aliphatic aldehydes enabled by N-heterocyclic carbene catalysis
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Described is the first study on oxidative enantioselective α-fluorination of simple aliphatic aldehydes enabled by N-heterocyclic carbene catalysis. N-fluorobis(phenyl)-sulfonimide serves as a an oxidant and as an "F" source. The C-F bond formation occurs
- Li, Fangyi,Wu, Zijun,Wang, Jian
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supporting information
p. 656 - 659
(2015/03/04)
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- A recyclable CO surrogate in regioselective alkoxycarbonylation of alkenes: Indirect use of carbon dioxide
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Herein, we report a Pd-catalysed alkoxycarbonylation of alkenes based on the use of a recyclable CO2 reduction product, the crystalline and air-stable N-formylsaccharin, as a CO surrogate. The carbonylation proceeds under ambient conditions in an exceptionally complementary regioselective fashion yielding the desired branched products from styrene derivatives and valuable linear esters from alkyl-substituted alkenes.
- Gehrtz,Hirschbeck,Fleischer
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supporting information
p. 12574 - 12577
(2015/08/06)
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- Ionic liquid-catalyzed internal redox esterification reaction
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The internal redox esterification of α,β-unsaturated aldehydes and alcohols was carried out using different ionic liquids (ILs) as catalysts and reaction solvents. The basic ionic liquid, 1-butyl-3-methylimidazolium acetate ([bmim]OAc), exhibited the best activity for this reaction. The influences of the amount of ionic liquid catalyst and reaction time on yield of saturated ester have been investigated. The results showed that ionic liquid anions have a crucial effect on the redox esterification of α,β- unsaturated aldehydes and alcohols. The nucleophilic carbenes generated in situ from the ionic liquid cation were believed to be actual active species for this reactions.
- Yu, Yinyin,Hua, Li,Zhu, Wenwen,Shi, Yu,Cao, Ting,Qiao, Yunxiang,Hou, Zhenshan
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p. 1287 - 1298
(2013/03/29)
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- Enzyme-like catalysis via ternary complex mechanism: Alkoxy-bridged dinuclear cobalt complex mediates chemoselective O-esterification over N-amidation
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Hydroxy group-selective acylation in the presence of more nucleophilic amines was achieved using acetates of first-row late transition metals, such as Mn, Fe, Co, Cu, and Zn. Among them, cobalt(II) acetate was the best catalyst in terms of reactivity and selectivity. The combination of an octanuclear cobalt carboxylate cluster [Co4(OCOR)6O]2 (2a: R = CF3, 2b: R = CH3, 2c: R = tBu) with nitrogen-containing ligands, such as 2,2′-bipyridine, provided an efficient catalytic system for transesterification, in which an alkoxide-bridged dinuclear complex, Co2(OCOtBu)2(bpy) 2(μ2-OCH2-C6H4-4- CH3)2 (10), was successfully isolated as a key intermediate. Kinetic studies and density functional theory calculations revealed Michaelis-Menten behavior of the complex 10 through an ordered ternary complex mechanism similar to dinuclear metallo-enzymes, suggesting the formation of alkoxides followed by coordination of the ester.
- Hayashi, Yukiko,Santoro, Stefano,Azuma, Yuki,Himo, Fahmi,Ohshima, Takashi,Mashima, Kazushi
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supporting information
p. 6192 - 6199
(2013/05/23)
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- Efficient direct ester condensation between equimolar amounts of carboxylic acids and alcohols catalyzed by trifluoromethanesulfonic acid (TfOH) in Solkane365mfc
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A simple, practical, and environmentally benign esterification protocol has been devised on the basis of TfOH as the catalyst and Solkane365mfc as the reaction medium. The direct condensation of equimolar amounts of various carboxylic acids and alcohols was conveniently carried out without recourse to any additional water removal technique, giving the desired carboxylic esters in excellent yields.
- Xu, Xiu-Hua,Azuma, Ayaka,Taniguchi, Misaki,Tokunaga, Etsuko,Shibata, Norio
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p. 3848 - 3852
(2013/04/23)
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- Umpolung reactions in an ionic liquid catalyzed by electrogenerated N-heterocyclic carbenes. Synthesis of saturated esters from activated α,β-unsaturated aldehydes
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The umpolung reaction of α,β-unsaturated aldehydes to saturated esters has been carried out in an ionic liquid by organocatalysis of electrogenerated NHC. The roles of solvent, precatalyst and proton donor of the ionic liquid have been verified and good to high yields of esters have been obtained using a "green" and mild methodology.
- Feroci, Marta,Chiarotto, Isabella,Orsini, Monica,Pelagalli, Romina,Inesi, Achille
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supporting information; experimental part
p. 5361 - 5363
(2012/06/30)
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- ZINC CLUSTER
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Disclosed is a novel zinc cluster compound represented by general formula (1): Zn4O (OCOR)6 (RCOOH)n, wherein R represents an alkyl group which has 1 to 4 carbon atoms and may be substituted with a halogen atom, and n repr
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Page/Page column 4
(2012/07/14)
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- One-pot sequential synthesis of ethers from an aliphatic carboxylic acid and an alcohol by indium-catalyzed deoxygenation of an ester
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We have developed a widely applicable and direct method of etherification from a carboxylic acid and an alcohol by indium-catalyzed deoxygenation of the transient ester formed in a one-pot reaction. This simple catalytic reducing system appears to be remarkably tolerant of several functional groups including alkenes, halogens, nitro and heterocyclic groups. A reducing system composed of InBr3 and an economical hydrosiloxane, PMHS (polymethylhydrosiloxane) , enabled one-pot etherification by using a variety of aliphatic carboxylic acids and alcohols. Copyright
- Sakai, Norio,Usui, Yuta,Moriya, Toshimitsu,Ikeda, Reiko,Konakahara, Takeo
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p. 4603 - 4608
(2012/10/30)
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- α-Aroyloxyaldehydes: Scope and limitations as alternatives to α-haloaldehydes for NHC-catalysed redox transformations
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α-Aroyloxyaldehydes are readily prepared bench stable synthetic intermediates. Their ability to act as α-haloaldehyde surrogates for NHC-promoted redox esterifications and in [4+2] cycloadditions is described.
- Ling, Kenneth B.,Smith, Andrew D.
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supporting information; experimental part
p. 373 - 375
(2011/02/24)
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- ACYLATION REACTION OF HYDROXYL GROUP
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Disclosed is a selective ester production process of an alcoholic hydroxyl group, which proceeds under chemically mild conditions, while having adequate environmental suitability, operability and economical efficiency. Specifically disclosed is a process for producing an ester compound, which is characterized in that an alcohol and a carboxylic acid ester compound are reacted in the presence of a compound containing zinc element, thereby selectively acylating a hydroxyl group of the alcohol.
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Page/Page column 12; 14
(2010/07/03)
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- N-Heterocyclic carbene-catalyzed oxidations
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N-Heterocyclic carbenes catalyze the oxidation of allylic and benzylic alcohols as well as saturated aldehydes to esters with manganese(IV) oxide in excellent yields. A variety of esters can be synthesized, including protected carboxylates. The oxidation proceeds under mild conditions, with low loadings of a simple triazolium salt pre-catalyst in the presence of base. Substrates containing potentially epimerizable centers are oxidized while preserving stereochemical integrity. The acyl triazolium intermediate generated under catalytic conditions can be employed as a chiral acylating agent in the desymmetrization of meso-diols.
- Maki, Brooks E.,Chan, Audrey,Phillips, Eric M.,Scheidt, Karl A.
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experimental part
p. 3102 - 3109
(2009/09/05)
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- Protic acid immobilized on solid support as an extremely efficient recyclable catalyst system for a direct and atom economical esterification of carboxylic acids with alcohols
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(Chemical Equation Presented) A convenient and clean procedure of esterification is reported by direct condensation of equimolar amounts of carboxylic acids with alcohols catalyzed by an easy to prepare catalyst system of perchloric acid immobilized on silica gel (HClO4-SiO2). The direct condensation of aryl, heteroaryl, styryl, aryl alkyl, alkyl, cycloalkyl, and long-chain aliphatic carboxylic acids with primary/secondary alkyl/cycloalkyl, allyl, propargyl, and long-chain aliphatic alcohols has been achieved to afford the corresponding esters in excellent yields. Chiral alcohol and N-t-Boc protected chiral amino acid also resulted in ester formation with the representative carboxylic acid or alcohol without competitive N-t-Boc deprotection and detrimental effect on the optical purity of the product demonstrating the mildness and chemoselectivity of the procedure. The esters of long-chain (>C10) acids and alcohols are obtained in high yields. The catalyst is recovered and recycled without significant loss of activity. The industrial application of the esterification process is demonstrated by the synthesis of prodrugs of ibuprofen and a few commercial flavoring agents. Other protic acids such as H2SO4, HBr, TfOH, HBF4, and TFA that were adsorbed on silica gel were less effective compared to HClO4-SiO2 following the order HClO4-SiO 2 ? H2SO4-SiO2 > HBr-SiO 2 > TfOH-SiO2 ? HBF4-SiO2 ≈ TFA-SiO2. When HClO4 was immobilized on other solid supports the catalytic efficiency followed the order HClO4-SiO 2 > HClO4-K10 > HClO4-Al 2O3 (neutral) > HClO4-Al2O 3 (acidic) > HClO4-Al2O3 (basic).
- Chakraborti, Asit K.,Singh, Bavneet,Chankeshwara, Sunay V.,Patel, Alpesh R.
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supporting information; experimental part
p. 5967 - 5974
(2009/12/24)
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- N-heterocyclic carbene-catalyzed oxidation of unactivated aldehydes to esters
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(Chemical Equation Presented) N-Heterocyclic carbenes catalyze the oxidation of unactivated aldehydes to esters with manganese(IV) oxide in excellent yield. The reaction proceeds through a transient activated alcohol, which when generated in situ allows for the selective oxidation of the aldehyde under mild conditions. These conditions successfully oxidize potentially epimerizable aldehydes and alcohols while preserving stereochemical integrity. A variety of ester derivatives can be synthesized with variation of the acylated alcohol as well as the unactivated aldehyde.
- Maki, Brooks E.,Scheldt, Karl A.
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supporting information; experimental part
p. 4331 - 4334
(2009/06/06)
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- Protonation of homoenolate equivalents generated by N-heterocyclic carbenes
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Homoenolate equivalents are generated by Lewis basic N-heterocyclic carbene catalysts and then protonated to generate efficiently saturated esters from unsaturated aldehydes. This reactivity is extended to the generation of β-acylvinyl anions from alkynyl aldehydes. The asymmetric protonation of a homoenolate equivalent generated from a β,β-disubstituted aldehyde can be accomplished with a chiral N-heterocyclic carbene. Georg Thieme Verlag Stuttgart.
- Maki, Brooks E.,Chan, Audrey,Scheidt, Karl A.
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p. 1306 - 1315
(2008/12/22)
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- A versatile, practical, and inexpensive reagent, pyridine-3-carboxylic anhydride (3-PCA), for condensation reactions
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A highly useful method for the preparation of carboxylic esters and carboxamides from various carboxylic acids was established by using a novel condensing reagent, pyridine-3-carboxylic anhydride (3-PCA), in the presence of 4-(dimethylamino)pyridine as an activator. The reactions of various carboxylic acids with nucleophiles, such as alcohols or amines, afforded the corresponding carboxylic acids or carboxamides in good to high yields under mild conditions by using simple experimental procedure. In addition, it was confirmed that this protocol was applicable to a gram-scale synthesis and the by-products, including pyridine-3-carboxylic acid and pyridine-3-carboxylate (or pyridine-3- carboxamide) produced in situ, were easily removed by using a simple aqueous workup.
- Funasaka, Setsuo,Mukaiyama, Teruaki
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experimental part
p. 148 - 159
(2009/04/06)
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- Pyridine-3-carboxylic anhydride (3-PCA): A versatile, practical, and inexpensive reagent for condensation reaction between carboxylic acids and alcohols
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A synthesis of carboxylic esters from various carboxylic acids and alcohols is successfully carried out by using a condensation reagent, pyridine-3-carboxylic anhydride (3-PCA). This reaction materialized synthesis of various carboxylic esters to be carried out under mild conditions by simple experimental procedure. Copyright
- Mukaiyama, Teruaki,Funasaka, Setsuo
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p. 326 - 327
(2008/02/04)
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- Conversion of α,β-unsaturated aldehydes into saturated esters: An umpolung reaction catalyzed by nucleophilic carbenes
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(Chemical Equation Presented) N-Heterocyclic carbenes derived from benzimidazolium salts are effective catalysts for generating homoenolate species from α,β-unsaturated aldehydes. These nucleophilic intermediates can be protonated, and the resulting activated carbonyl unit is trapped with an alcohol nucleophile, thereby promoting a highly efficient conversion of an α,β-unsaturated aldehyde into a saturated ester. A kinetic resolution of secondary alcohols can be achieved using chiral imidazoylidene catalysts.
- Chan, Audrey,Scheidt, Karl A.
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p. 905 - 908
(2007/10/03)
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- A new method for the synthesis of carboxylic esters and lactones with di-2-thienyl carbonate (2-DTC) by the promotion of DMAP and iodine
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The esterification of carboxylic acids with alcohols by using di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino) pyridine (DMAP) proceeded smoothly to afford the corresponding esters in good-to-high yields along with 2(5H)-thiophenone. This esterification was accelerated by the addition of an equimolar amount of iodine to afford the esters in higher yields within a shorter reaction time. Further, cyclization of ω-hydroxycarboxylic acids with an equimolar amount of 2-DTC in the presence of a catalytic amount of DMAP, followed by the addition of 1-4 equimolar amounts of iodine, afforded the corresponding lactones in good-to-high yields under mild conditions. This method was successfully employed in the synthesis of erythro-aleuritic acid lactone.
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
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p. 1508 - 1519
(2007/10/03)
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- Efficient method for the esterification of carboxylic acids with alcohols using di-2-thienyl carbonate promoted by catalytic amounts of DMAP and Hf(OTf)4
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Esterification of carboxylic acids with alcohols including bulky secondary ones by using an equimolar amount of di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino)pyridine (DMAP) followed by addition of a catalytic amount of hafnium(IV) trifluoromethanesulfonate (Hf(OTf)4) afforded the corresponding esters in good to high yields. Copyright
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
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p. 190 - 191
(2007/10/03)
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- An Effective Use of Benzoic Anhydride and Its Derivatives for the Synthesis of Carboxylic Esters and Lactones: A Powerful and Convenient Mixed Anhydride Method Promoted by Basic Catalysts
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Various carboxylic esters are obtained at room temperature in excellent yields with high chemoselectivities from nearly equimolar amounts of carboxylic acids and alcohols using 2-methyl-6-nitrobenzoic anhydride with triethylamine by the promotion of a basic catalyst such as 4-(dimethylamino)pyridine. A variety of lactones are also prepared in high yields at room temperature from the corresponding ω-hydroxycarboxylic acids with use of 2-methyl-6-nitrobenzoic anhydride in the presence of 4-(dimethylamino)pyridine. A similar reaction occurs with triethylamine when using a catalytic amount of 4-(dimethylamino)pyridine 1-oxide as an effective promoter for the intramolecular condensation reaction. These methods are successfully applied to the synthesis of erythro-aleuritic acid lactone and an eight-membered-ring lactone moiety of octalactins A and B. The efficiency of the cyclizations is compared to those of other reported lactonizations.
- Shiina, Isamu,Kubota, Mari,Oshiumi, Hiromi,Hashizume, Minako
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p. 1822 - 1830
(2007/10/03)
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- Conversion of α-haloaldehydes into acylating agents by an internal redox reaction catalyzed by nucleophilic carbenes
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Reactivity umpolung allows us to consider nontraditional bond disconnections. We report herein that treatment of an α-haloaldehyde with a nucleophile in the presence of catalytic amounts of nucleophilic carbenes results in an internal redox reaction giving rise to a dehalogenated acylating agent as an intermediate by a new reaction manifold. A brief illustration of the scope of this reaction is presented along with evidence supporting the direct intervention of the carbene in the acylation step. Copyright
- Reynolds, Nathan T.,De Alaniz, Javier Read,Rovis, Tomislav
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p. 9518 - 9519
(2007/10/03)
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- A Convenient Protocol for the Esterification of Carboxylic Acids with Alcohols in the Presence of di-t-Butyl Dicarbonate
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Stoichiometric mixtures of carboxylic acids and primary or secondary alkyl alcohols are cleanly converted into their corresponding esters by treatment with di-t-butyl dicarbonate [(BOC)2O] in the presence of catalytic amounts of N,N′-dimethylaminopyridine (DMAP). This convenient procedure provides a general access to a broad variety of esters including those bearing highly sensitive functional groups such as phenol esters or BOC-groups. Purification of the products is particularly easy since the byproducts t-BuOH and CO2 are volatile - a great advantage over the standard DCC/DMAP method.
- Goo?en, Lukas J.,D?hring, Arno
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p. 263 - 266
(2007/10/03)
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- An effective method for the synthesis of carboxylic esters and lactones using substituted benzoic anhydrides with Lewis acid catalysts
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An efficient mixed-anhydride method for the synthesis of carboxylic esters and lactones using benzoic anhydride having electron withdrawing substituent(s) is developed by the promotion of Lewis acid catalysts. In the presence of a catalytic amount of TiCl2(ClO4)2, various carboxylic esters are prepared in high yields through the formation of the corresponding mixed-anhydrides from 3,5-bis(trifluoromethyl)benzoic anhydride and carboxylic acids. The combined catalyst consisting of TiCl 2(ClO4)2 together with chlorotrimethylsilane functions as an effective catalyst for the synthesis of carboxylic esters from free carboxylic acids and alcohols with 4-(trifluoromethyl)benzoic anhydride. Various macrolactones are prepared from the free ω-hydroxycarboxylic acids by the combined use of 4-(trifluoromethyl)benzoic anhydride and titanium(IV) catalysts together with chlorotrimethylsilane under mild reaction conditions. The lactonization of trimethylsilyl ω-(trimethylsiloxy) carboxylates using 4-(trifluoromethyl)benzoic anhydride is also promoted at room temperature in the presence of a catalytic amount of TiCl 2(ClO4)2. An 8-membered ring lactone, a synthetic intermediate of cephalosporolide D, is successfully synthesized according to this mixed-anhydride method using 4-(trifluoromethyl)benzoic anhydride by the promotion of a catalytic amount of Hf(OTf)4.
- Shiina, Isamu
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p. 1587 - 1599
(2007/10/03)
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- Efficient method for the esterification of carboxylic acids with alcohols using di-2-thienyl carbonate promoted by DMAP and iodine
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Reaction of carboxylic acids with alcohols by using an equimolar amount of di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino)pyridine (DMAP) followed by addition of an equimolar amount of iodine proceeded smoothly to afford the corresponding esters and 2(5H)-thiophenone in good to high yields.
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
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p. 968 - 969
(2007/10/03)
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- A new method for the esterification of carboxylic acids with various alcohols by using di-2-thienyl carbonate, a new coupling reagent
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Esterification of carboxylic acids with alcohols by using di-2-thienyl carbonate in the presence of a catalytic amount of 4-(dimethylamino)pyridine (DMAP) proceeded smoothly under mild conditions to afford the corresponding esters and 2(5H)-thiophenone in good to high yields.
- Mukaiyama, Teruaki,Oohashi, Yoshiaki,Fukumoto, Kentarou
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p. 552 - 553
(2007/10/03)
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- Fluoroalkyldistannoxane Catalysts for Transesterification in Fluorous Biphase Technology
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Novel, practical protocols of transesterification have been advanced with recourse to fluorous biphase technology. The fluoroalkyldistannoxane catalysts enable transesterification in FC-72 solvent to furnish 100% yields of the desired esters by use of reactants ester and alcohol in a 1:1 ratio. The catalysts also work in FC-72/organic solvent system as well as in toluene alone. A number of esters and alcohols bearing various functional groups are employable. The catalysts can be totally recovered and reused. More conveniently, the catalyst solution in FC-72 which is separated from the reaction mixture is directly used for the next reaction.
- Xiang, Jiannan,Orita, Akihiro,Otera, Junzo
-
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- A practical and green chemical process: Fluoroalkyldistannoxane-catalyzed biphasic transesterification
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There is no need for the recovery of the catalyst in the fluorous biphasic transesterification catalyzed by [{Cl(C6F13CH2CH2)2 SnOSn(C6F13CH2CH2) 2Cl}2] (1; see scheme), which results in quantitative conversions and yields. An FC-72 solution of the dimeric flouroalkyldistannoxane 1 can be recycled repeatedly without having to recover the neat catalyst.
- Xiang, Jiannan,Toyoshima, Shinji,Orita, Akihiro,Otera, Junzo
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p. 3670 - 3672
(2007/10/03)
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- O,O′-di(2-pyridyl) thiocarbonate as an efficient reagent for the preparation of carboxylic esters from highly hindered alcohols
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Various carboxylic esters were obtained in high yields from free carboxylic acids and several alcohols including bulky ones by using O,O′-di(2-pyridyl) thiocarbonate and a catalytic amount of DMAP.
- Saitoh, Katsuyuki,Shiina, Isamu,Mukaiyama, Teruaki
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p. 679 - 680
(2007/10/03)
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- Total asymmetric synthesis of taxol by dehydration condensation between 7-TES baccatin III and protected N-benzoylphenylisoserines prepared by enantioselective aldol reaction
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Total asymmetric synthesis of Taxol was completed by dehydration condensation between a protected N-benzoylphenylisoserine 4 or 9 and 7-TES baccatin in which was prepared from 8-membered ring enone. Taxol side chains 4, 7, 9 and 11, optically active protected N-benzoylphenylisoserines, were successfully synthesized by enantioselective aldol reaction from two achiral starting materials, benzaldehyde and an enol silyl ether derived from S-ethyl benzyloxyethanethioate.
- Shiina, Isamu,Saitoh, Katsuyuki,Frechard-Ortuno, Isabelle,Mukaiyama, Teruaki
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- A Useful Method for the Preparation of Carboxylic Esters from Free Carboxylic Acids and Alcohols
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Various carboxylic esters are prepared in excellent yields from nearly equimolar amounts of free carboxylic acids and alcohols at room temperature by combined use of 4-(trifluoromethyl)benzoic anhydride and a catalytic amount of active titanium(IV) salt together with chlorotrimethylsilane.
- Shiina, Isamu,Miyoshi, So,Miyashita, Mitsutomo,Mukaiyama, Teruaki
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p. 515 - 518
(2007/10/02)
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- Efficient acylation of alcohols with acylthiazolidine-2-thiones and cesium fluoride
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Primary alcohols are acylated in good yield under almost neutral conditions with 3-acylthiazolidine-2-thiones and cesium fluoride.For secondary alcohols, the yield is improved by the addition of zinc bromide. t-Butanol is not acylated.
- Yamada, M.,Yahiro, S.,Yamano, T.,Nakatani, Y.,Ourisson, G.
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p. 824 - 829
(2007/10/02)
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- (Trimethylsilyl)ethoxyacetylene. An Effective Reagent for Mild Dehydrative Condensation of Carboxylic Acids and H-Acidic Materials
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(Trimethylsilyl)ethoxyacetylene, a stable and easy to handle dehydrating reagent, is quite effective for the title condensation to prepare ester-, lactone-, lactam-, and peptide-linkages under mild conditions.
- Kita, Yasuyuki,Akai, Shuji,Yamamoto, Miki,Taniguchi, Miyako,Tamura, Yasumitsu
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p. 334 - 337
(2007/10/02)
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- FACILE METHOD FOR THE ACYLATION OF ALCOHOLS AND AMIDES BY THE USE OF 1,1'-DIMETHYLSTANNOCENE AND ACYL CHLORIDES
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Acylation of alcohols and amides was effected under mild conditions by the use of 1,1'-dimethylstannocene and acyl chlorides, giving the corresponding esters and imides in good to excellent yields.
- Mukaiyama, Teruaki,Ichikawa, Junji,Asami, Masatoshi
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p. 293 - 296
(2007/10/02)
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