- Multiple-Functional Diphosphines: Synthesis, Characterization, and Application to Pd-Catalyzed Alkoxycarbonylation of Alkynes
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A series of diphosphine ligands (L1-L5) containing bis-phosphino fragments and bis-amido groups as well as intensive electron-withdrawing F atoms were synthesized and fully characterized. The structures of the prepared complex of Pd-L5 demonstrate that as for L5, the incorporated two phosphino fragments participate in the chelation to the Pd center inversely along with two Cl-ligands to present a typical square-planar configuration, whereas the two amido groups simultaneously develop a hydrogen-bond interaction with Cl-ligands to facilitate the timely dissociation of Cl-ligands from the Pd center. It was found that L5 enabled the Pd complex to be more active in the alkoxycarbonylation of alkynes with MeOH for the synthesis of branched/linear α,β-unsaturated carboxylic esters with general yields of 60-89%. In L5, the incorporated diphosphino fragments, diamino groups, and F atoms conferred a catalytic effect to the Pd complex synergetic toward the reaction.
- Chen, Xiao-Chao,Guo, Lin,Liu, Lei,Liu, Ye,Lu, Yong,Yao, Yin-Qing,Zhao, Kai-Chun,Zhao, Xiao-Li
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p. 750 - 760
(2022/04/03)
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- Thieme Chemistry Journals Awardees - Where Are They Now? Bis(2-pyridyl)amides as Readily Cleavable Amides under Catalytic, Neutral, and Room-Temperature Conditions
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Mild solvolytic cleavage of bis(2-pyridyl)amide under neutral and room-temperature conditions is described. The inherently stable amide was readily activated by catalytic amounts of metal cations to react with alcohols. Based on X-ray crystallographic analysis, the primary driving force was considered to be amide distortion induced by the metal coordination of two pyridyl groups in a bidentate fashion without affecting the amide functionality. The compatibility of the acid/base-sensitive functionalities and the absence of racemization during solvolysis highlight the mildness of the present protocol.
- Adachi, Shinya,Kumagai, Naoya,Shibasaki, Masakatsu
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p. 301 - 305
(2018/02/10)
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- An ionic liquid catalyzed probase method for one-pot synthesis of α,β-unsaturated esters from esters and aldehydes under mild conditions
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A one-pot synthesis of α,β-unsaturated esters from unactivated esters and aldehydes using strong bases, such as sodium alkoxide and potassium tert-butoxide, was reported. However, the ionic liquid (IL) catalyzed probase method for producing α,β-unsaturated esters was not reported until now. In this work, a series of ILs with fluoride anions were firstly prepared and used as catalysts in combination with the probase N,O-bis(trimethylsilyl) acetamide (BSA) for the α,β-unsaturated esters synthesis. This process could also be promoted through the introduction of another IL with Lewis acid sites. The yield and selectivity of the product could reach up to 84.2% and 95.0%, respectively, when [Bmim]F was used in combination with [Bmim]Cl/AlCl3 (the molar fraction of AlCl3 is 0.67). The mechanism investigation through GC-MS indicates that BSA would convert into onium amide, which acted as a strong base for α-H abstraction, with the catalysis of [Bmim]F. Meanwhile, [Bmim]Cl/AlCl3 played an important role in the condensation step between enolates and aldehydes. On the basis of mechanism insights, kinetic and thermodynamic studies were also carried out for a better understanding of this new route.
- Wang, Gang,Xu, Yiming,Zhang, Suojiang,Li, Zengxi,Li, Chunshan
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p. 4838 - 4848
(2017/10/23)
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- Investigation of two- and three-bond carbon–hydrogen coupling constants in cinnamic acid based compounds
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Two- and three-bond coupling constants (2JHC and 3JHC) were determined for a series of 12 substituted cinnamic acids using a selective 2D inphase/antiphase (IPAP)-single quantum multiple bond correlation (HSQMBC) and 1D proton coupled 13C NMR experiments. The coupling constants from two methods were compared and found to give very similar values. The results showed coupling constant values ranging from 1.7 to 9.7 Hz and 1.0 to 9.6 Hz for the IPAP-HSQMBC and the direct 13C NMR experiments, respectively. The experimental values of the coupling constants were compared with discrete density functional theory (DFT) calculated values and were found to be in good agreement for the 3JHC. However, the DFT method under estimated the 2JHC coupling constants. Knowing the limitations of the measurement and calculation of these multibond coupling constants will add confidence to the assignment of conformation or stereochemical aspects of complex molecules like natural products. Copyright
- Pierens, Gregory K.,Venkatachalam, Taracad K.,Reutens, David C.
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p. 941 - 946
(2016/11/16)
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- Appel reaction of carboxylic acids with tribromoisocyanuric acid/triphenylphosphine: A mild and acid-free preparation of esters and amides
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A facile and efficient method for esterification and amidation of carboxylic acids under neutral conditions has been developed. Esters and amides can be prepared by reacting a carboxylic acid (1 mmol) with tribromoisocyanuric acid (0.37 mmol) and triphenylphosphine (1 mmol) in dichloromethane at room temperature, followed by addition of an alcohol or an amine, respectively.
- Da Cunha Sindra, Haryadylla,De Mattos, Marcio C.S.
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p. 1129 - 1136
(2016/07/06)
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- Attractive aerobic access to the α,β-unsaturated acyl azolium intermediate: Oxidative NHC catalysis via multistep electron transfer
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To replace high molecular weight oxidants with air (O2) we introduce multistep electron transfer NHC catalysis. The method provides a general and selective oxidation of the α,β-unsaturated aldehyde derived homoenolate to the synthetically useful α,β-unsaturated acyl azolium intermediate. Several independent oxidative NHC-catalyzed reactions are viable with this strategy and the products can be isolated in high to excellent yields.
- Ta,Axelsson,Sundén
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supporting information
p. 686 - 690
(2016/02/12)
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- Borane-Catalyzed Reductive α-Silylation of Conjugated Esters and Amides Leaving Carbonyl Groups Intact
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Described herein is the development of the B(C6F5)3-catalyzed hydrosilylation of α,β-unsaturated esters and amides to afford synthetically valuable α-silyl carbonyl products. The α-silylation occurs chemoselectively, thus leaving the labile carbonyl groups intact. The reaction features a broad scope of both acyclic and cyclic substrates, and the synthetic utility of the obtained α-silyl carbonyl products is also demonstrated. Mechanistic studies revealed two operative steps: fast 1,4-hydrosilylation of conjugated carbonyls and then slow silyl group migration of a silyl ether intermediate.
- Kim, Youngchan,Chang, Sukbok
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supporting information
p. 218 - 222
(2016/01/25)
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- Palladium-catalyzed aerobic oxidative double allylic C-H oxygenation of alkenes: A novel and straightforward route to α,β-unsaturated esters
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A mild tandem oxidative functionalization of allyl aromatic hydrocarbons was accomplished using the catalytic system of Pd(OAc)2/DMA under 1 atm O2. The green twofold C-O bond formation involving double allylic C-H oxygenation unlocks opportunities for markedly different synthetic strategies. Moreover, the reaction affords aryl α,β-unsaturated esters directly from readily available terminal olefins in moderate to good yields with excellent chemo- and stereoselectivities.
- Yang, Wanfei,Chen, Huoji,Li, Jianxiao,Li, Chunsheng,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 9575 - 9578
(2015/06/08)
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- Oxidative esterification of alcohols and aldehydes using supported iron oxide nanoparticle catalysts
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The synthesis of esters has become an important industrial methodology over the past years because of the role that they serve in the chemical industry. In this study, we present the use of a novel catalyst for the direct conversion of aldehydes into esters. The yields obtained using supported iron oxide nanoparticle catalysts (FeNP) are very high (>90%). The catalyst is also shown to be very stable as shown by the recyclability study (up to 11 times).
- Rajabi, Fatemeh,Arancon, Rick A.D.,Luque, Rafael
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p. 101 - 103
(2015/02/19)
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- Oxidative esterification of aldehydes using mesoionic 1,2,3-triazolyl carbene organocatalysts
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The synthesis and catalytic activity of a new class of 1,2,3-triazolyl N-heterocyclic carbene organocatalysts is described. These new catalysts chemoselectively facilitate the oxidative esterification of aldehydes. NMR acidity studies show an inverse correlation between triazolium acidity and reactivity. Kinetic studies show that the resting state of the catalyst involves a NHC-aldehyde adduct. A catalytically active intermediate was synthesized and characterized by X-ray diffraction as the initial carbene-aldehyde adduct.
- Berry, Matthew T.,Castrejon, Disnay,Hein, Jason E.
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supporting information
p. 3676 - 3679
(2014/08/05)
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- Highly efficient direct aerobic oxidative esterification of cinnamyl alcohol with alkyl alcohols catalysed by gold nanoparticles incarcerated in a nanoporous polymer matrix: A tool for investigating the role of the polymer host
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The selective aerobic oxidation of cinnamyl alcohol to cinnamaldehyde, as well as direct oxidative esterification of this alcohol with primary and secondary aliphatic alcohols, were achieved with high chemoselectivity by using gold nanoparticles supported in a nanoporous semicrystalline multi-block copolymer matrix, which consisted of syndiotactic polystyrene-co-cis-1,4- polybutadiene. The cascade reaction that leads to the alkyl cinnamates occurs through two oxidation steps: the selective oxidation of cinnamyl alcohol to cinnamaldehyde, followed by oxidation of the hemiacetal that results from the base-catalysed reaction of cinnamaldehyde with an aliphatic alcohol. The rate constants for the two steps were evaluated in the temperature range 10-45 °C. The cinnamyl alcohol oxidation is faster than the oxidative esterification of cinnamaldehyde with methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol or 1-octanol. The rate constants of the latter reaction are pseudo-zero order with respect to the aliphatic alcohol and decrease as the bulkiness of the alcohol is increased. The activation energy (Ea) for the two oxidation steps was calculated for esterification of cinnamyl alcohol with 1-butanol (Ea=57.8±11.5 and 62.7±16.7 kJ mol -1 for the first and second step, respectively). The oxidative esterification of cinnamyl alcohol with 2-phenylethanol follows pseudo-first-order kinetics with respect to 2-phenylethanol and is faster than observed for other alcohols because of fast diffusion of the aromatic alcohol in the crystalline phase of the support. The kinetic investigation allowed us to assess the role of the polymer support in the determination of both high activity and selectivity in the title reaction. Golden boost to the esterification: The highly efficient and selective aerobic oxidation of cinnamyl alcohols, catalysed by gold nanoparticles supported in a nanoporous polymer matrix, in the presence of primary and secondary alkyl alcohols afforded alkyl cinnamates (see figure). The active role of the host-polymer matrix was investigated.
- Buonerba, Antonio,Noschese, Annarita,Grassi, Alfonso
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p. 5478 - 5486
(2014/05/20)
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- Influence of electronically and sterically tunable cinnamate ligands on the spectroscopic, kinetic, and thermodynamic properties of bis(triphenylphosphine) palladium(0) olefin complexes
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A detailed study of the influence of electronic and steric characteristics of cinnamic acid esters on the spectroscopic, kinetic, and thermodynamic properties of bis(triphenylphosphine)palladium(0) cinnamic acid ester complexes is presented (51 different new complexes included). These complexes show a dynamic behavior on the NMR spectroscopic time scale. Therefore, the rotational barriers of the olefin about the metalolefin bond as well as the dissociation entropy and enthalpy of the olefin and the dissociation mechanism could be determined. These findings are interpreted together with the NMR spectroscopic, IR spectroscopic, and X-ray structural data (7 new structures included) concerning the influence of the different olefin ligands on the complex properties by means of Hammett plots. DFT calculations were performed to support the mechanistic conclusions.
- Buchner, Magnus R.,Bechlars, Bettina,Wahl, Bernhard,Ruhland, Klaus
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experimental part
p. 588 - 601
(2012/03/22)
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- Enantioselective cyclopropanation of enals by oxidative N-heterocyclic carbene catalysis
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Carbene catalysed redox activation of α,β-unsaturated aldehydes is applied for generation of α,β-unsaturated acyl azoliums which undergo cyclopropanation upon reaction with a sulfur ylide and an alcohol to give the corresponding cyclopropanecarboxylic acid esters. With chiral carbenes good to excellent diastereo and enantioselectivities are obtained.
- Biswas, Anup,De Sarkar, Suman,Tebben, Ludger,Studer, Armido
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supporting information; experimental part
p. 5190 - 5192
(2012/06/01)
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- One-pot preparation of phenylpropanoid esters co-catalyzed by boric acid and piperidine
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Phenylpropanoid esters, especially those with hydroxyl and/or methoxy groups on the benzene ring, are important medicinal chemicals or intermediates. They are usually prepared by esterification of their corresponding substituted cinnamic acids with various alcohols. However, the esterification procedures often suffer from environmentally hazardous problems when sulfuric acid is used as a catalyst or suffer from unsatisfactory yields and expensive raw material when enzyme is applied as a catalyst. In this paper, a convenient one-pot process for preparing various phenylpropanoid esters from substituted benzaldehydes bearing hydroxyl and/or methoxyl groups has been developed. The alcohols react first with malonic acid catalyzed by boric acid to form monomalonate, then without separation, let the resultant mixture immediately react with the injected various substituted benzaldehydes in the presence of piperidine to afford the desired esters with moderate to good yields. Springer Science+Business Media B.V. 2011.
- Wang, Huan,Wei, Qing-Yi,Jiang, Hong,Jiang, Zhen-Hua
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experimental part
p. 207 - 213
(2012/05/20)
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- Novel natural product-based cinnamates and their thio and thiono analogs as potent inhibitors of cell adhesion molecules on human endothelial cells
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In the present study, we report the design and synthesis of novel analogs of cinnamates, thiocinnamates and thionocinnamates and evaluated the potencies of these analogs to inhibit TNF-α induced ICAM-1 expression on human endothelial cells. By using whole cell-ELISA, our screening data demonstrated that ethyl 3′,4′,5′-trimethoxythionocinnamate (ETMTC) is the most potent inhibitor of TNF-α induced ICAM-1, VCAM-1 and E-selectin. As functional consequences, ETMTC abrogated TNF-α induced adhesion of neutrophils to the endothelial monolayer. Structure-activity relationship studies revealed the critical role of the chain-length of the alkyl group in the alcohol moiety, number of methoxy groups in the aromatic ring of the cinnamoyl moiety and the presence of the α, β- C-C double bond in the thiocinnamates and thionocinnamates.
- Kumar, Sarvesh,Singh, Brajendra K.,Arya, Pragya,Malhotra, Shashwat,Thimmulappa, Rajesh,Prasad, Ashok K.,Van Der Eycken, Erik,Olsen, Carl E.,Depass, Anthony L.,Biswal, Shyam,Parmar, Virinder S.,Ghosh, Balaram
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scheme or table
p. 5498 - 5511
(2011/12/15)
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- Br?nsted acidic ionic liquid as an efficient and recyclable promoter for hydroesterification of olefins catalyzed by a triphenylphosphine-palladium complex
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Several Br?nsted acidic ionic liquids (BAILs) with different acidic scales were synthesized and employed as acid promoters for the hydroesterification of olefins catalyzed by a triphenylphosphine-palladium complex. The results showed that catalysts with BAIL promoters resulted inmoderate to high conversions to the ester product with excellent selectivity, depending on the acidity of BAIL used. The reaction conversion reached a plateau when the catalyst was promoted using BAIL with a Hammett acidity function less than or equal to-0.11. This catalyst system could be reused several times for the hydroesterification of 1-hexene without a considerable decrease in the catalytic performance.
- Yang, Jing,Zhou, Hancheng,Lu, Xinning,Yuan, Youzhu
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experimental part
p. 1200 - 1204
(2011/01/03)
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- Ionic liquids as solvent for efficient esterification of carboxylic acids with alkyl halides
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The selective esterification of carboxylic acid derivatives with a variety of alkyl halides was carried out using ionic liquid as solvent in the presence of triethylamine. The reaction was found to proceed under relatively mild conditions with excellent conversions (up to 99%) and selectivities. The ionic liquid was recycled and reused. TUeBITAK.
- Goek, Yetkin,Alici, Buelent,Cetinkaya, Enginc,OeZdemir, Ismail,Oezeroglu, Ozlem
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experimental part
p. 187 - 191
(2010/09/11)
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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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- An efficient and versatile approach for the immobilization of carbene precursors via copper-catalyzed [3+ 2]-cycloaddition and their catalytic application
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Different classes of alkynyl-substituted heterazolium derivatives could be covalently immobilized on an azide-functionalized support via copper-catalyzed 1,3-dipolar cycloaddition, which efficiently yields a rigid and robust 1,2,3-triazole linkage. The catalytic performance of the corresponding nucleophilic carbenes (NHCs) was examined in intramolecular Stetter reactions (chroman-4-one products) and organocatalytic redox esterifications (α,β-unsaturated esters). The MeOPEG-im-mobilized organocatalysts are highly active, and show comparable diastereoselectivities to non-supported derivatives. Additionally, they allow simplified work-up procedures and also have proven to be recyclable.
- Zeitler, Kirsten,Mager, Ina
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p. 1851 - 1857
(2008/09/17)
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- A fast and simple method for the acylation of alcohols with acid chlorides promoted by metallic samarium
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Acylation of primary, secondary, allyl and benzyl alcohols with acid chlorides promoted by samarium metal under neutral condition gave carboxylic acid esters in good to excellent yields. Acylation of a tertiary alcohol did not occur under the same reaction conditions.
- Jia, Xue-Shun,Wang, Hai-Long,Huang, Qing,Kong, Ling-Long,Zhang, Wei-He
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p. 135 - 138
(2007/10/03)
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- Na2CO3/SOCl2: A mild and convenient reagent for the preparation of isopropyl carboxylates
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Na2CO3/SOCl2 has been used for esterification of aliphatic and aromatic acids with isopropanol. This esterification method is compatible with a wide assortment of functional groups.
- Kazemi, Foad,Kiasat, Ali Reza,Mombaini, Began
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p. 1187 - 1191
(2007/10/03)
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- Process for preparation of cinnamates using polyaniline salts as catalysts
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The present invention relates to a process for preparation of cinnamates using polyaniline salts as catalysts. The present invention more particularly relates to a process for producing cinnamic esters by the direct esterification of cinnamic acid with aliphatic alcohols over polyaniline salts as catalysts. The process of esterification may be carried out by reacting cinnamic acid with aliphatic mono hydric alcohol in presence of catalyst, removing the catalyst by conventional methods. The ester can be isolated such as filtration followed by isolation of esters by conventional column chromatography using adsorbent such as silica gel and solvent such as chloroform, ethylacetate, hexane and mixture there off
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- Silica Chloride: A Versatile Heterogeneous Catalyst for Esterification and Transesterification
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Silica chloride has been found to be an efficient catalyst for esterification of carboxylic acids (aliphatic, aromatic and conjugated) with alcohols (primary, secondary and tertiary) as well as for transesterification of esters (by both alcoholysis and acidolysis).
- Srinivas,Mahender,Das, Biswanath
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p. 2479 - 2482
(2007/10/03)
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- Syntheses and QSAR studies of sorbic, cinnamic and ricinoleic acid derivatives as potential antibacterial agents
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Amides and esters of sorbic, cinnamic and ricinoleic acid have been synthesized and evaluated for their antibacterial activity against gram (+) ve S. aureus, B. subtilis and gram (-) ve E. coli. Most of the compounds have shown moderate to good activity against microorganisms under test. Linear regression analysis of descriptors related to lipophilicity, steric and electronic parameters against antibacterial activity have been performed. QSAR studies indicated the predominance of electronic and steric parameters over the lipophilicity parameters in contributing antibacterial activity.
- Narasimhan,Kothawade,Pharande,Mourya,Dhake
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p. 2828 - 2834
(2007/10/03)
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