- ZWITTERIONIC CATALYSTS FOR (TRANS)ESTERIFICATION: APPLICATION IN FLUOROINDOLE-DERIVATIVES AND BIODIESEL SYNTHESIS
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An amide/iminium zwitterion catalyst has a catalyst pocket size that promotes transesterification and dehydrative esterification. The amide/iminium zwitterions are easily prepared by reacting aziridines with aminopyridines. The reaction can be applied a wide variety of esterification processes including the large-scale synthesis of biodiesel. The amide/iminium zwitterions allow the avoidance of strongly basic or acidic condition and avoidance of metal contamination in the products. Reactions are carried out at ambient or only modestly elevated temperatures. The amide/iminium zwitterion catalyst is easily recycled and reactions proceed in high to quantitative yields.
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Paragraph 0015; 0028
(2021/01/29)
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- Esterification of Tertiary Amides by Alcohols Through C?N Bond Cleavage over CeO2
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CeO2 has been found to promote ester forming alcoholysis reactions of tertiary amides. The present catalytic system is operationally simple, recyclable, and it does not require additives. The esterification process displays a wide substrate scope (>45 examples; up to 93 % isolated yield). Results of a density functional theory (DFT) study combined with in situ FT-IR observations indicate that the process proceeds through rate limiting addition of a CeO2 lattice oxygen to the carbonyl group of the adsorbed acetamide species with energy barrier of 17.0 kcal/mol. This value matches well with experimental value (17.9 kcal/mol) obtained from analysis of the Arrhenius plot. Further studies by in situ FT-IR and temperature programmed desorption using probe molecules demonstrate that both acidic and basic properties are important, and consequently, CeO2 showed the best performance for the C?N bond cleavage reaction.
- Toyao, Takashi,Nurnobi Rashed, Md.,Morita, Yoshitsugu,Kamachi, Takashi,Hakim Siddiki,Ali, Md. A.,Touchy,Kon, Kenichi,Maeno, Zen,Yoshizawa, Kazunari,Shimizu, Ken-ichi
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p. 449 - 456
(2018/09/11)
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- Amide/Iminium Zwitterionic Catalysts for (Trans)esterification: Application in Biodiesel Synthesis
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A class of zwitterionic organocatalysts based on an amide anion/iminium cation charge pair has been developed. The zwitterions are easily prepared by reacting aziridines with aminopyridines. They are catalytically applicable to transesterifications and dehydrative esterifications. Mechanistic studies reveal that the amide anion and iminium cation work synergistically in activating the reaction partners, with the iminium cationic moiety interacting with the carbonyl substrates through nonclassical hydrogen bonding. The reaction can be applied to large-scale synthesis of biodiesel under mild conditions.
- Lam, Ying-Pong,Ng, Wing-Hin,Tan, Fei,Tse, Ying-Lung Steve,Wang, Xinyan,Yeung, Ying-Yeung
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p. 8083 - 8092
(2019/08/26)
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- Palladium on carbon-bromobenzene mediated esterification and transesterification
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A series of carboxylic acids were converted into their corresponding esters using the Pd/C catalyzed hydrogenation conditions in the presence of catalytic bromobenzene in alcohols and the method could also be applicable for the transesterification of esters. Good to excellent yields were obtained for different aliphatic or aromatic starting materials. The success of this esterification relies on the in situ generation of hydrobromic acid (HBr) from bromobenzene which provides a mild and acidic reaction environment. The palladium catalyst exhibits a remarkable activity and is reusable for up-to three consecutive cycles.
- Aavula, Sanjeev Kumar,Chikkulapalli, Anil,Hanumanthappa,Jyothi, Indira,Vinod Kumar,Manjunatha, Sulur G.
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p. 5690 - 5694
(2013/09/24)
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- CeO2 as a versatile and reusable catalyst for transesterification of esters with alcohols under solvent-free conditions
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CeO2 acted as an efficient and reusable heterogeneous catalyst for transesterification of esters with alcohols under the solvent-free conditions at 160 °C. Among the 11 kinds of metal oxides, CeO2 is the most suitable catalyst in terms of catalytic activity, leaching-resistance and reusability. This catalytic system tolerates various esters and alcohols, and valuable esters such as heteroaromatic esters and benzyl benzoates are produced, demonstrating a practical utility of the system. On the basis of kinetic analysis and in situ IR studies of adsorbed species, a reaction mechanism is proposed, in which proton abstraction of alcohol by a Lewis base site of CeO2 to yield alkoxide species is the rate-limiting step.
- Tamura, Masazumi,Hakim Siddiki,Shimizu, Ken-Ichi
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p. 1641 - 1646
(2013/09/24)
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- CeO2-catalysed one-pot selective synthesis of esters from nitriles and alcohols
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Thirteen kinds of metal oxides were tested for one-pot selective synthesis of esters from nitriles and alcohols. Ceria (CeO2) showed more than two orders of magnitude higher activity than the other oxides. CeO2 acted as a reusable and effective catalyst for the ester synthesis from various nitriles and alcohols under neutral and solvent-free conditions at 160 °C. This method provides a rare example for the synthesis of heteroaromatic esters, which have been difficult to synthesize by conventional catalytic esterification methods. Valuable esters such as picolinic acid alkyl esters and niacin benzyl esters were synthesized, demonstrating a practical aspect of the present method. Kinetic studies suggested the following reaction mechanism: (1) H2O and ROH dissociate on CeO2, (2) nucleophilic attack of hydroxyl species (OHδ-) to the adsorbed nitrile on CeO2, leading to the formation of the primary amide, (3) nucleophilic attack of alkoxide species (ORδ-) to the amide as the rate-limiting step.
- Tamura, Masazumi,Tonomura, Takuya,Shimizu, Ken-Ichi,Satsuma, Atsushi
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experimental part
p. 984 - 991
(2012/06/18)
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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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- o-benzenedisulfonimide as reusable bronsted acid catalyst for acid-catalyzed organic reactions
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Acid-catalyzed organic reactions, such as etherification, esterification, acetal synthesis, cleavage, and interconversion, and pinacol rearrangement were carried out in the presence of catalytic amounts of o-benzenedisulfonimide as Bronsted acid catalyst; the conditions were mild and selective. The catalyst was easily recovered and purified, ready to be used in further reactions, with economic and ecological advantages. Georg Thieme Verlag Stuttgart.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano,Venturello, Paolo
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p. 1379 - 1388
(2008/12/21)
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- Reactivity of anionic nucleophiles in ionic liquids and molecular solvents
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The nucleophilic reactivity of a representative series of anions has been measured in [hmim][ClO4] 3i, [hm2im][ClO4] 3′i, and [hmim][PF6] 3l ILs in the reaction with n-alkyl methanesulfonates and compared with that found in common molecular solvents (MeOH, DMSO, PhCl). The reactivity is found to depend on both the imidazolium cation-anion interaction and the specific solvation by water present in the IL, the water playing the main effect, in particular with hydrophilic anions. Removal of the largest quantity of water remarkably increases the ion pair reactivity in the IL up to rate constant value k comparable with those obtained in DMSO and in low polarity media (PhCl).
- Betti, Cecilia,Landini, Dario,Maia, Angelamaria
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p. 1689 - 1695
(2008/09/18)
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- o-benzenedisulfonimide: A novel and reusable catalyst for acid-catalyzed organic reactions
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The o-benzenedisulfonimide is used as Br?nsted acid in catalytic amounts in various acid-catalyzed organic reactions, such as etherification, esterification, and acetalization; the conditions required are mild and in the considered examples the results are always good. A useful aspect of the use of this catalyst is its easy recovery in high yield from the reaction mixture and its reuse in other reactions, with economic and ecological advantages. Georg Thieme Verlag Stuttgart.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano,Venturello, Paolo
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p. 2209 - 2212
(2008/02/10)
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- A facile, catalytic and environmentally benign method for esterification of carboxylic acids and transesterification of carboxylic esters with nearly equimolar amounts of alcohols
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A practical and green chemical process for the esterification of carboxylic acids with alcohols and transesterification of carboxylic esters in good to excellent yields by using K5CoW12O14· 3H2O (0.1 mol%) as catalyst is reported. The catalyst exhibited remarkable reusable activity. Georg Thieme Verlag Stuttgart.
- Bose, D. Subhas,Satyender, Apuri,Das, A. P. Rudra,Mereyala, Hari Babu
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p. 2392 - 2396
(2008/02/08)
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- Esterification of carboxylic acids with alcohols under microwave irradiation in the presence of zinc triflatet
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The esterification of aliphatic and aromatic carboxylic acids with various alcohols (1°, 2°, 3°, benzylic) was studied under microwave irradiation in the presence of zinc triflate as catalyst; the reaction times were short and the yield of reactions was good to excellent.
- Shekarriz, Marzieh,Taghipoor, Sohrab,Khalili, Ali Asghar,Jamarani, Mohammad Soleymani
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p. 172 - 173
(2007/10/03)
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- Alkylation reactions of potassium carboxylates supported on alumina: Comparison between ball-milling, impregnation and dispersion procedures
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Potassium carboxylate alkylation by n-bromooctane on neutral alumina in "dry media" under microwave irradiation was studied for different methods of preparation of salt-support powder. Mechanical milling and impregnation techniques led to equivalent yields, much higher than those obtained through dispersion. The first method avoids using solvents and subsequent drying of powders. Crystallographic and granulometric studies of the resulting powders were performed to ascertain the results.
- Gasgnier, Michel,Szwarc, Henri,Petit, Alain,Nahmias, Jean,Loupy, Andre
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p. 1233 - 1238
(2007/10/03)
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- An efficient use of zeolite catalysts for esterification of carboxylic acids
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A mild and practical method (batch process) for the esterification of carboxylic acids with alcohols using zeolite catalysts in good to excellent yields is described. The esterification of phenylacetic acid with ethanol has also been carried out in very high yield using continuous flow fixed bed reactor.
- Gumaste, Vikas K.,Deshmukh,Bhawal
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p. 1174 - 1179
(2007/10/03)
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- CYCLOPHOSPHAZENIC POLYPODANDS AS POWERFUL CATION COMPLEXING AGENTS, EFFICIENT PHASE-TRANSFER CATALYSTS AND ANION ACTIVATORS
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A survey dealing with cyclophosphazenic polypodands 3a-c, a new class of "octopus-like" molecules is reported.These many-armed ligands are powerful complexing agents of alkali metal salts and hence behave as very efficient catalysts in many reations (nucleophilic substitutions, eliminations, alkylations, oxidations, reductions) under solid-liquid and liquid-liquid phase-transfer catalysis conditions.Their catalytic activity is much better than that of the open-chain analogues PEGs 4, 5 and TRIDENT-1, 6.Moreover, anion activation realized by cyclophosphazenic polypodands, both of homogeneous and heterogeneous systems, is comparable with that obtained with the more sophisticated and expensive crown ethers.
- Landini, Dario,Maia, Angelamaria,Podda, Gianni
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p. 583 - 588
(2007/10/03)
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- Mechanism and Anion Activation in Solid-Liquid Phase-transfer Reactions Catalysed by Cyclophosphazenic Polypodands. Comparison with Cyclic Analogue Crown Ethers
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A kinetic study of the nucleophilic substitution of the methanesulfonic group by anions (Cl-, Br-, I-, SCN-, C6H5O-, C6H5CH2COO-) catalysed by cyclophosphazenic polypodands has been performed under solid-liquid phase-transfer conditions.The results obtained show that the mechanism of PTC previously found for cyclic ligands (crown ethers, cryptands) also operates in the case of these open-chain ligands: the attack by the anionic nucleophile on the substrate occurs in the organic phase and is rate determining of the overall process.The nucleophilicity scales found (I- > C6H5O- ca.SCN- > C6H5CH2COO-; I- > Br- > Cl-) as well as the anion activation are comparable with those found for cyclic crown ethers.This indicates that the anionic reactive species involved are similar in the complexes of both ligands.
- Landini, Dario,Maia, Angelamaria,Podda, Gianni,Secci, Daniela,Yan, Yong Ming
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p. 1721 - 1724
(2007/10/02)
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- SPECIFIC HYDRATION AND NUCLEOPHILIC REACTIVITY OF ORGANIC ANIONS UNDER PHASE-TRANSFER CATALYSIS AND HOMOGENEOUS CONDITIONS
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The effect of specific hydration on the nucleophilic reactivity of the organic anions 3a-i has been studied under PhCl-aqueous NaOH (15-50percent) PTC conditions and in anhydrous chlorobenzene.The sensitivity to the specific solvation, in the order oxanion > carbanion >/= nitranion >/= thianion, can be explained on the basis of the different donor atom tendency.The data provide a useful guide to the choice of the best reaction conditions of these anions under PTC.
- Landini, Dario,Maia, Angelamaria,Rampoldi, Alessandro
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p. 513 - 518
(2007/10/02)
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