- A stand-alone cobalt bis(dicarbollide) photoredox catalyst epoxidates alkenes in water at extremely low catalyst load
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The cobalt bis(dicarbollide) complex, Na[3,3′-Co(η5-1,2-C2B9H11) (Na[1]), is an effective photoredox catalyst for the oxidation of alkenes to epoxides in water. Advantageous features of Na[1] include its lack of photoluminescence, high solubility and surfactant behavior in aqueous media, as well as the donor ability of the carborane ligand and high oxidizing power of the Co4+/3+ couple. These features differentiate it from the well-known and widely used photosensitizer tris (2,2′-bipyridine) ruthenium(ii) ([Ru(bpy)3]2+), which also participates in electron transfer through an outer sphere mechanism. A comparison of the catalytic performance of [Ru(bpy)3]2+ with Na[1] for alkene photo-oxidation is fully in favor of Na[1], as the former shows very low or null efficiency. With a catalyst loading of 0.1 mol% conversions between 65-97% have been obtained in short reaction times, 15 minutes, with moderate selectivity for the corresponding epoxide, due to the formation of side products as diols. But when the catalyst loading is reduced to 0.01 mol%, the selectivity for the corresponding epoxide increased considerably, being the only compound formed after 15 minutes of reaction (selectivity >99%). High TON values have been obtained (TON = 8500) for the epoxidation of aromatic and aliphatic alkenes in water. We have verified that Na[3,3′-Co(η5-1,2-C2B9H11)2] acts as a photocatalyst in both the epoxidation of alkenes and in their hydroxylation in aqueous medium with a higher rate for epoxidation than for hydroxylation. Preliminary photooxidation tests using methyl oleate as the substrate led to the selective epoxidation of the double bond. These results represent a promising starting point for the development of practical methods for the processing of unsaturated fatty acids, such as the valorisation of animal fat waste using this sustainable photoredox catalyst. This journal is
- Guerrero, Isabel,Romero, Isabel,Teixidor, Francesc,Vi?as, Clara
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p. 10123 - 10131
(2021/12/27)
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- Synthesis of fatty ketoesters by tandem epoxidation-rearrangement with heterogeneous catalysis
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Unsaturated fatty esters can be easily transformed into ketoesters through a two-step process. The highly efficient epoxidation is carried out with tert-butyl hydroperoxide (TBHP) in α,α,α-trifluorotoluene (TFT) using a Ti-silica heterogeneous catalyst. The formed epoxide is easily rearranged by a heterogeneous Br?nsted acid, with Nafion-silica SAC13 as the most efficient one. Both reactions can be combined in a tandem process, with separation of the Ti-silica catalyst by filtration from the reaction medium and addition of the second acid catalyst to perform the second reaction. Each catalyst is separated individually and can be reused, with or without re-activation, under the same conditions to maximize the productivity.
- Dorado, Vicente,Fraile, José M.,Gil, Lena,Herrerías, Clara I.,Mayoral, José A.
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p. 1789 - 1795
(2020/04/09)
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- An assay for DNA polymerase β lyase inhibitors that engage the catalytic nucleophile for binding
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DNA polymerase β (Pol β) repairs cellular DNA damage. When such damage is inflicted upon the DNA in tumor cells treated with DNA targeted antitumor agents, Pol β thus diminishes their efficacy. Accordingly, this enzyme has long been a target for antitumor therapy. Although numerous inhibitors of the lyase activity of the enzyme have been reported, none has yet proven adequate for development as a therapeutic agent. In the present study, we developed a new strategy to identify lyase inhibitors that critically engage the lyase active site primary nucleophile Lys72 as part of the binding interface. This involves a parallel evaluation of the effect of the inhibitors on the wild-type DNA polymerase β (Pol β) and Pol β modified with a lysine analogue at position 72. A model panel of five structurally diverse lyase inhibitors identified in our previous studies (only one of which has been published) with unknown modes of binding were used for testing, and one compound, cis-9,10-epoxyoctadecanoic acid, was found to have the desired characteristics. This finding was further corroborated by in silico docking, demonstrating that the predominant mode of binding of the inhibitor involves an important electrostatic interaction between the oxygen atom of the epoxy group and Nε of the main catalytic nucleophile, Lys72. The strategy, which is designed to identify compounds that engage certain structural elements of the target enzyme, could find broader application for identification of ligands with predetermined sites of binding.
- Chen, Shengxi,Cheng, Qi,Daskalova, Sasha M.,Eisenhauer, Brian M.,Fahmi, NourEddine,Feng, Xizhi,Gao, Mingxuan,Hecht, Sidney M.,Ji, Xun,Khdour, Omar M.
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supporting information
(2020/07/21)
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- Tungstenocene-grafted silica catalysts for the selective epoxidation of alkenes
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Tungstenocene(IV) dichloride was successfully deposited and grafted on the surface of a commercially-available non-ordered silica support via either a liquid-phase or a dry impregnation approach. After a high-temperature calcination step, two W(VI)-grafted silica catalysts, with a metal loading around 1.2–1.7 wt.%, were obtained. They were fully characterized by physisorption and spectroscopic techniques, which evidenced well-dispersed tungsten oxide polyoxo cluster sites, for the catalyst prepared via liquid-phase grafting, and evenly dispersed larger monoclinic tungsten(VI) oxide aggregates, for the catalyst prepared via dry impregnation, respectively. Both W/SiO2 solids showed moderate to good conversion values in the epoxidation of (R)-(+)-limonene and methyl oleate (up to 68%), in the presence of aqueous hydrogen peroxide, with good selectivity to the desired epoxides (63% and 78%, respectively). The heterogeneous character of the most interesting W/SiO2 catalyst prepared via dry impregnation was confirmed by a hot centrifugation test and by an extended recovery and reuse of the solid in six catalytic runs.
- Bisio, Chiara,Gallo, Alessandro,Psaro, Rinaldo,Tiozzo, Cristina,Guidotti, Matteo,Carniato, Fabio
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p. 133 - 142
(2019/06/18)
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- Fatty acid based biocarbonates: Al-mediated stereoselective preparation of mono-, di- and tricarbonates under mild and solvent-less conditions
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A catalytic method for the preparation of a series of fatty acid derived biocarbonates has been developed using a binary Al-complex/PPNCl catalyst. This catalyst system allows conversion of fatty acid derived epoxides under comparatively mild reaction conditions (70-85 °C, 10 bar) while maintaining high levels of diastereospecificity with cis/trans ratios of up to 97:3 in the products. The comparative catalysis data obtained for the reactions catalysed only by the nucleophilic halide based components show that the presence of the Al-complex is crucial for the retention of the original stereochemistry.
- Pe?a Carrodeguas,Cristòfol,Fraile,Mayoral,Dorado,Herrerías,Kleij
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supporting information
p. 3535 - 3541
(2017/08/15)
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- Allyl-Palladium-Catalyzed α,β-Dehydrogenation of Carboxylic Acids via Enediolates
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A highly practical and step-economic α,β-dehydrogenation of carboxylic acids via enediolates is reported through the use of allyl-palladium catalysis. Dianions underwent smooth dehydrogenation when generated using Zn(TMP)2?2 LiCl as a base in the presence of excess ZnCl2, thus avoiding the typical decarboxylation pathway of these substrates. Direct access to 2-enoic acids allows derivatization by numerous approaches.
- Zhao, Yizhou,Chen, Yifeng,Newhouse, Timothy R.
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supporting information
p. 13122 - 13125
(2017/09/13)
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- Cooperative catalyst system for the synthesis of oleochemical cyclic carbonates from CO2 and renewables
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Phosphonium salts and various (transition-) metals were studied as catalysts in the synthesis of carbonated oleochemicals from the corresponding epoxides and carbon dioxide. In combination with tetra-n-butylphosphonium bromide molybdenum compounds were identified as highly active co-catalysts for the formation of cyclic carbonates. The co-catalyst accelerates the conversion of the epoxidized fatty acid ester considerably. The chemo- as well as the stereoselectivity of the carbonated oleochemicals can be controlled by the choice of the catalyst and the reaction conditions. Under optimized reaction conditions this new catalyst system allows the conversion of both mono- and polyepoxidized oleo compounds into the corresponding carbonates in good to excellent yields up to >99% under comparatively mild reaction conditions. This procedure has been applied to the synthesis of a potential renewable plasticizer and works well even at larger scale (200 g).
- Tenhumberg, Nils,Büttner, Hendrik,Sch?ffner, Benjamin,Kruse, Daniela,Blumenstein, Michael,Werner, Thomas
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supporting information
p. 3775 - 3788
(2016/07/07)
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- Mild catalytic oxidations of unsaturated fatty acid methyl esters (FAMEs) by oxovanadium complexes
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A selection of unsaturated fatty acid methyl esters, namely methyl oleate (C18:1), methyl linoleate (C18:2) and methyl linolenate (C18:3) has been oxidized under mild homogeneous catalytic conditions, using a series of oxovanadium(IV) complexes containing 4-acyl-5-pyrazolone donor ligands with different substituents on acyl residue. The main goal was to evaluate the catalytic role exerted by oxovanadium(IV) metal center, as precursor complex, in the selective oxyfunctionalization of carbon-carbon double bonds of these bio-renewable resources, as a greener alternative to more drastic processes currently used at the industrial level. The three substrates, oxidized using tert-butylhydroperoxide as main oxidant, with or without solvents, showed high conversions of starting materials and high selectivities in the formation of corresponding mono- di- and tri-epoxides, especially under solvent-less conditions. Investigations on a probable catalytic cycle mechanism operative in the tert-butylhydroperoxide oxidation of a simple FAME model substrate, have been performed by means of ESI-MS.
- Cecchini, Martina Maya,De Angelis, Francesco,Iacobucci, Claudio,Reale, Samantha,Crucianelli, Marcello
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p. 120 - 128
(2016/03/22)
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- Substrate dependent synergetic and antagonistic interaction of ammonium halide and polyoxometalate catalysts in the synthesis of cyclic carbonates from oleochemical epoxides and CO2
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Organic halides and polyoxometalates (POMs) were studied as catalyst systems for the insertion of carbon dioxide into epoxides originating from plant oils as biogenic feedstock. In the formation of methyl oleate carbonate, synergistic rate acceleration and increased cis-selectivity were observed using ammonium halide and transition metal substituted silicotungstate POMs catalysts in a combined system. Mechanistic insight into the cooperative action was gained by kinetic measurements and analysis of the stereochemical outcome of the reaction. For poly-epoxidised oleochemicals as substrates, the simple ammonium halide catalyst gave better performance as side reactions were encountered with the POM-containing system.
- Langanke, Jens,Greiner, Lasse,Leitner, Walter
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p. 1173 - 1182
(2013/06/27)
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- A highly efficient, green and recoverable catalytic system for the epoxidation of fatty esters and biodiesel with H2O2
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A highly efficient and green strategy for the epoxidation of fatty esters, combining a green oxidant (aqueous hydrogen peroxide) and a recyclable catalyst (a seleninic acid derivative) is presented. The possibility of integrating renewable solvents derived from glycerol in the productive cycle of biodiesel commodities is also explored. Fluorinated solvents (both commercial and glycerol-derived) play a double key role on this methodology: on the one hand, they strongly accelerate epoxidation reaction with respect to common non-fluorinated solvents and, on the other hand, some of them allow catalyst recycling. Mono- and polyunsaturated fatty esters, as well as soy biodiesel have been epoxidized with excellent yields and selectivities towards epoxide under the optimal conditions and with minimum catalyst loads.
- De Torres, Miriam,Arends, Isabel W.C.E.,Mayoral, José A.,Pires, Elisabet,Jiménez-Osés, Gonzalo
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experimental part
p. 91 - 96
(2012/07/13)
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- Catalyzed ring opening of epoxides: Application to bioplasticizers synthesis
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The ring opening of mono, di or tri-substituted epoxides by acetic anhydride to corresponding diacetates is catalyzed by weak bases such as hydrotalcite in the carbonated form. This reaction is performed at 423 K without solvent and the solid catalyst is reused after simple regeneration for 4 runs with constant conversion. Ring-opening of methyl oleate epoxide leads to the formation of useful diacetate methyl oleate. Starting from vegetable oils, polyacetate derivatives are prepared in three catalytic steps (methanolysis, epoxidation then ring opening). Plastisol was prepared by mixing these products with PVC and their rheological properties were evaluated. The recorded data show that they can act as bioplasticizer with similar behaviour as phthalate reference.
- Fogassy, Gabriella,Ke, Pan,Figueras, Fran?ois,Cassagnau, Philippe,Rouzeau, Sophie,Courault, Valérie,Gelbard, Georges,Pinel, Catherine
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experimental part
p. 1 - 8
(2011/11/11)
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- Synthesis of biobased polyurethane from oleic and ricinoleic acids as the renewable resources via the AB-type self-condensation approach
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Polyurethane (PU) from methyl oleate (derived from sunflower oil) and ricinoleic acid (derived from castor oil) was synthesized using the AB-type self-polycondensation approach for the first time. In the present work, three novel AB-type monomers, namely, a mixture of 10-hydroxy-9-methoxyoctadecanoyl azide/9-hydroxy-10-methoxyoctadecanoyl azide (HMODAz), 12-hydroxy-9-cis- octadecenoyl azide (HODEAz) and methyl-N-11-hydroxy-9-cis-heptadecen carbamate (MHHDC) were synthesized from methyl oleate and ricinoleic acid using simple reaction steps. Out of these, HMODAz and HODEAz monomers were polymerized by the acyl-azido and hydroxyl AB-type self-condensation approach, while MHHDC monomer was polymerized through AB-type self-condensation via transurethane reaction. The acyl-azido and hydroxyl self-condensations were carried out at various temperatures (50, 60, 80. and 110 °C) in bulk with and without catalyst. A FTIR study of the polymerization, using HMODAz at 80 °C without catalyst, indicates in situ formation of an intermediate isocyanate group in the first 15?30 min, and further onward, the molar mass increases as observed by SEC analysis. In the case of the MHHDC monomer, a transurethane reaction was used to obtain a similar PU (which was obtained by AB-type acyl-azido and hydroxyl self-condensation of HODEAz) in the presence of titanium tetrabutoxide as a catalyst at 130 °C. HMODAz, HODEAz, MHHDC, and corresponding polyurethanes were characterized by FTIR, 1H NMR, 13C NMR, and MALDI-TOF mass spectroscopy. Differential scanning calorimetric analysis of polyurethanes derived from HMODAz, HODEAz, and MHHDC showed two different glass transition temperatures for soft segments (at lower temperature) and hard segments (at higher temperature), indicating phase-separated morphology.
- Palaskar, Dnyaneshwar V.,Boyer, Aurelie,Cloutet, Eric,Alfos, Carine,Cramail, Henri
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experimental part
p. 1202 - 1211
(2011/02/23)
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- New methodology for the conversion of epoxides to alkenes
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Epoxides have been transformed in good yields to alkenes by a process involving (i) ring-opening of the epoxide with 2-mercaptobenzothiazole, (ii) oxidation of the derived ss-hydroxy thioethers to the corresponding sulfones, and (iii) thermal or base-promoted fragmentation of these sulfones to alkenes. The stereochemistry of the starting epoxide is transfer-red faithfully to the alkene product, because of the SN2 epoxide ring-opening reactions and the antiperiplanar SO2 elimination reaction of the ss- alkoxysulfinate intermediates. This methodology may form the basis of a new protecting group strategy for alkenes.
- Wu, Feng-Ling,Ross, Benjamin P.,McGeary, Ross P.
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experimental part
p. 1989 - 1998
(2010/06/15)
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- Conversion of methyl oleate to branched-chain hydroxy fatty acid derivatives
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As part of a project to develop new and expanded uses of oilseed products and by-products (such as biodiesel, fuel additives, and lubricants), studies were conducted on the synthetic conversion of oleic acid (in the ester form) to branched-chain fatty acid ester derivatives. In these studies, methyl oleate was epoxidized and subsequently treated with four different organocuprate reagents in the presence of boron trifluoride diethyl etherate to produce novel branched-chain hydroxy acid derivatives. For each reaction, the two distinct isomeric products (methyl 9-alkyl-10-hydroxyoctadecanoate and methyl 9-hydroxy-10-alkyloctadecanoate) were isolated in the pure forms. Details of the synthesis and characterization (GC-MS, NMR, and differential scanning calorimetry) of these compounds will be discussed.
- Dailey Jr., Oliver D.,Prevost, Nicolette T.,Strahan, Gary D.
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experimental part
p. 1101 - 1114
(2010/05/19)
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- The fluorine gauche effect. Langmuir isotherms report the relative conformational stability of (±)-erythro- and (±)-threo-9,10-difluorostearic acids
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(±)-Erythro- and (±)-threo-9,10-difluorostearic acids, which differ only by a stereogenic interconversion of a single C-F bond, have significantly different conformational stabilities.
- Tavasli, Mustafa,O'Hagan, David,Pearson, Christopher,Petty, Michael C.
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p. 1226 - 1227
(2007/10/03)
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- A silica gel-supported ruthenium complex of 1,4,7-Trimethyl-1,4,7-triazacyclononane as recyclable catalyst for chemoselective oxidation of alcohols and alkenes by tert-butyl hydroperoxide
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A silica gel-immobilized [(Me3tacn)RuIII(CF3 COO)2(H2O)]CF3CO2 complex (1-SiO2, Me3tacn = 1,4,7- trimethyl-1,4,7-triazacyclononane) was prepared by simple impregnation, and the catalyst was characterized by powdered X-ray diffraction, nitrogen adsorption/desorption, Raman, and diffuse reflectance UV-vis spectroscopies. The supported Ru catalyst can effect facile oxidation of alcohols by tert-butyl hydroperoxide (TBHP). Primary and secondary benzyl, allylic, and propargylic alcohols were transformed to their corresponding aldehydes and ketones in excellent yields; no oxidation of the C=C and C≡C bonds was observed for the allylic and propargylic alcohol oxidations. Likewise alkene epoxidation by TBHP can be achieved by 1-SiO2; cycloalkenes such as norbornene and cyclooctene were oxidized to their exo-epoxides exclusively in excellent yields (>95%). The 1-SiO2 catalyst can be recycled and reused for consecutive alcohol and alkene oxidations without significant loss of catalytic activity and selectivity; over 9000 turnovers have been attained for the oxidation of 1-phenyl-1-propanol to 1-phenyl-1-propanone. 4-Substituted phenols were oxidized by the "1 + TBHP" protocol to give exclusively ruthenium-catecholate complexes, which were characterized by UV-vis and ESI-MS spectroscopies. No (tert-butyldioxy)cyclohexadienone and other radical coupling/overoxidation products were produced using the "1 + TBHP" protocol. The formation of ruthenium-catecholate is proposed to proceed via ortho-hydroxylation of phenol.
- Cheung, Wai-Hung,Yu, Wing-Yiu,Yip, Wing-Ping,Zhu, Nian-Yong,Che, Chi-Ming
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p. 7716 - 7723
(2007/10/03)
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- A selenium catalyzed epoxidation in perfluorinated solvents with hydrogen peroxide
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The readily prepared 2,4-bisperfluorooctylphenyl butylselenide catalyzes the epoxidation of various olefins with hydrogen peroxide in a fluorous biphasic system. The catalyst is selectively soluble in perfluorinated solvents and can easily be recovered simply by phase separation. Furthermore, the catalyst can be reused several times without a decrease of yield and an increase of reaction time.
- Betzemeier, Bodo,Lhermitte, Frédéric,Knochel, Paul
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p. 489 - 491
(2007/10/03)
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- A NEW PARADIGM FOR ALKENE EPOXIDATION. ACTIVATION OF HYDROGEN PEROXIDE BY ORGANOPHOSPHORUS ELECTROPHILES
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Diphenylphosphinic anhydride and certain other organophosphorus electrophiles mediate the high-yield conversion of alkenes to epoxides by hydrogen peroxide in buffered aqueous tetrahydrofuran.
- Kende, Andrew S.,Delair, Philippe,Blass, Benjamin E.
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p. 8123 - 8126
(2007/10/02)
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- A facile, versatile procedure for the preparation of fatty acid esters suitable for glc or hplc analyses
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The preparation of fatty acid methyl esters for glc analyses and of various aryl esters for hplc analyses has traditionally been carried out in totally unrelated operations.This paper draws attention to the use of fatty acid-trifluoroacetic acid mixed anhydrides which may be directly and efficiently converted into either type of esters.The utility of the method was demonstrated by the preparation of series of methyl, 2-naphthyl, and vanillin fatty acid esters.The spectral characterization of some aryl fatty acid esters is recorded.
- Grossert, J. Stuart,Ratnayake, W. M. Nimal,Swee, Tiw
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p. 2617 - 2620
(2007/10/02)
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