The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Laureano Oliveros - One of the best experts on this subject based on the ideXlab platform.
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Mixed cellulose-derived benzoates bonded on allylsilica gel as HPLC chiral stationary phases: influence of the introduction of an aromatic moiety in the fixation substituent
Tetrahedron-asymmetry, 2003Co-Authors: Jordi Garcés, Laureano Oliveros, Pilar Franco, Cristina MinguillónAbstract:Abstract Several mixed alkenoxybenzoyl/benzoates and 10-undecenoyl/benzoates of cellulose were fixed onto allylsilica gel by the radical coupling of double bonds. The introduction of an aromatic group in the fixation substituent modifies the chiral recognition ability of the resulting chiral stationary phases (CSPs) in comparison with the 10-Undecenoate/benzoate cellulose derivatives. Better enantioselectivity values are achieved when the electronic and geometric characteristics of both substituents, fixating and derivatizing, are similar.
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First synthesis of the two enantiomers of α‐methyldiphenylalanine [(αMe)Dip] by HPLC resolution
Chirality, 2001Co-Authors: Soledad Royo, Laureano Oliveros, Ana I. Jiménez, Pilar López, Carlos CativielaAbstract:A strategy for the preparation of enantiomerically pure (R)- and (S)-α-methyldiphenylalanine, constrained phenylalanine analogs, is described. A racemic precursor was prepared in high yield from easily available starting products and subjected to HPLC resolution on a noncommercial chiral stationary phase. More than 600 mg of each enantiomer was isolated in optically pure form by using a 150 × 20 mm ID column containing mixed 10-Undecenoate/3,5-dimethylphenylcarbamate of cellulose covalently bonded to allylsilica gel and a mixture of n-hexane/2-propanol/acetone as the mobile phase. Chirality 14:39–46, 2002. © 2002 Wiley-Liss, Inc.
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Efficient access to all four stereoisomers of phenylalanine cyclopropane analogues by chiral HPLC
Chirality, 1999Co-Authors: Carlos Cativiela, María D. Díaz-de-villegas, Ana I. Jiménez, Pilar López, Michel Marraud, Laureano OliverosAbstract:: Bonded polysaccharide-derived chiral stationary phases were found to be useful for the preparation of the four stereoisomers of the cyclopropane analogue of phenylalanine (c(3)Phe) as well as for the direct determination of the enantiomeric purity of c(3)Phe derivatives by HPLC. Three chiral stationary phases, consisting of cellulose and amylose derivatives chemically bonded on allylsilica gel, were tested. The mixed 10-Undecenoate/3, 5-dimethylphenylcarbamate of cellulose, 10-Undecenoate/3, 5-dimethylphenylcarbamate of amylose and 10-Undecenoate/p-methylbenzoate of cellulose were the starting polysaccharide derivatives for CSP-1, CSP-2, and CSP-3, respectively. Using mixtures of n-hexane/chloroform/2-propanol as mobile phase on a semi-preparative column (150 mm x 20 mm ID) containing CSP-2, we separated about 1.7 g of racemic cis-methyl 1-tert-butoxycarbonylamino-2-phenylcyclopropanecarboxylate (cis-6) and 1.2 g of racemic trans-methyl-1-tert-butoxycarbonylamino-2-phenylcycloprop-anecarboxyl ate (trans-6) by successive injections. Copyright 1999 Wiley-Liss, Inc.
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Carbamates of cellulose bonded on silica gel: Chiral discrimination ability as HPLC chiral stationary phases
Chirality, 1998Co-Authors: Laureano Oliveros, Antonio Senso, Pilar Franco, Cristina MinguillónAbstract:Four cellulose mixed 10-Undecenoate/carbamate derivatives, simultaneously bearing 10-undecenoyl and variously substituted phenylaminocarbonyl groups, were chemically bonded on allylsilica gel. The study of the effect of these substitutions on the performance of the resulting chiral supports, and a comparison with the recently described 10-Undecenoate/3,5-dimethylphenylcarbamate derivative, are presented. In this study heptane/2-propanol or heptane/chloroform mixtures were used as mobile phases. Chirality 10:283–288, 1998. © 1998 Wiley-Liss, Inc.
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Solvent versatility of bonded cellulose-derived chiral stationary phases for high-performance liquid chromatography and its consequences in column loadability
Journal of Chromatography A, 1998Co-Authors: Pilar Franco, Cristina Minguillón, Laureano OliverosAbstract:The chromatographic behaviour of a 10-Undecenoate/3,5-dimethylphenylcarbamate of cellulose bonded on allylsilica gel is tested using four organic mobile-phase modifiers (2-propanol, chloroform, tetrahydrofuran and ethyl acetate). The advantages of the broad choice of solvents offered by this kind of chiral stationary phases and their resistance are discussed. The loadability of the column and its dependence both on the racemate to be resolved and on the solvent used as mobile phase are also discussed.
Cristina Minguillón - One of the best experts on this subject based on the ideXlab platform.
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Mixed cellulose-derived benzoates bonded on allylsilica gel as HPLC chiral stationary phases: influence of the introduction of an aromatic moiety in the fixation substituent
Tetrahedron-asymmetry, 2003Co-Authors: Jordi Garcés, Laureano Oliveros, Pilar Franco, Cristina MinguillónAbstract:Abstract Several mixed alkenoxybenzoyl/benzoates and 10-undecenoyl/benzoates of cellulose were fixed onto allylsilica gel by the radical coupling of double bonds. The introduction of an aromatic group in the fixation substituent modifies the chiral recognition ability of the resulting chiral stationary phases (CSPs) in comparison with the 10-Undecenoate/benzoate cellulose derivatives. Better enantioselectivity values are achieved when the electronic and geometric characteristics of both substituents, fixating and derivatizing, are similar.
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Carbamates of cellulose bonded on silica gel: Chiral discrimination ability as HPLC chiral stationary phases
Chirality, 1998Co-Authors: Laureano Oliveros, Antonio Senso, Pilar Franco, Cristina MinguillónAbstract:Four cellulose mixed 10-Undecenoate/carbamate derivatives, simultaneously bearing 10-undecenoyl and variously substituted phenylaminocarbonyl groups, were chemically bonded on allylsilica gel. The study of the effect of these substitutions on the performance of the resulting chiral supports, and a comparison with the recently described 10-Undecenoate/3,5-dimethylphenylcarbamate derivative, are presented. In this study heptane/2-propanol or heptane/chloroform mixtures were used as mobile phases. Chirality 10:283–288, 1998. © 1998 Wiley-Liss, Inc.
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Solvent versatility of bonded cellulose-derived chiral stationary phases for high-performance liquid chromatography and its consequences in column loadability
Journal of Chromatography A, 1998Co-Authors: Pilar Franco, Cristina Minguillón, Laureano OliverosAbstract:The chromatographic behaviour of a 10-Undecenoate/3,5-dimethylphenylcarbamate of cellulose bonded on allylsilica gel is tested using four organic mobile-phase modifiers (2-propanol, chloroform, tetrahydrofuran and ethyl acetate). The advantages of the broad choice of solvents offered by this kind of chiral stationary phases and their resistance are discussed. The loadability of the column and its dependence both on the racemate to be resolved and on the solvent used as mobile phase are also discussed.
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Preparative isolation of the eutomer of cyclothiazide by high-performance liquid chromatography on a cellulose-derived chiral stationary phase with toluene-acetone as the mobile phase
Journal of Chromatography A, 1996Co-Authors: Laureano Oliveros, Cristina Minguillón, Bernard Serkiz, Florent Meunier, Jean-pierre Volland, Alex A. CordiAbstract:The enantiomeric pair containing the eutomer of cyclothiazide can be resolved by HPLC on commercially available cellulose-derived chiral stationary phases (CSPs). However, the poor solubility of cyclothiazide in solvents compatible with this kind of CSP makes this separation difficult on a preparative scale. This operation was achieved with a CSP constituted by a 3,5-dimethylphenylcarbamate/10-Undecenoate derivative of cellulose fixed on allylsilica gel. This CSP is resistant to all the polar solvents usually applied in HPLC.
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Chromatographic resolution of several racemic 9-fluorenyl derivatives on a bonded cellulose derived chiral stationary phase for HPLC
Tetrahedron-asymmetry, 1996Co-Authors: Dolores Velasco, Pilar Franco, Zhanru Yu, Cristina MinguillónAbstract:Abstract The enantiomers of several 9-fluorenyl derivatives have been successfully resolved by HPLC on a chiral stationary phase (CSP) based on a mixed 10-Undecenoate/3,5-dimethylphenylcarbamate of cellulose bonded to allylsilica gel. Previous attempts at resolution, such as NMR methods, GC and the use of a multiple interaction type chiral column for HPLC, were unsuccessful.
Michael A. R. Meier - One of the best experts on this subject based on the ideXlab platform.
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Catalytic transesterification of cellulose in ionic liquids: Sustainable access to cellulose esters
2020Co-Authors: Alexander M. Schenzel, Andrea Hufendiek, Christopher Barner-kowollik, Michael A. R. MeierAbstract:Catalytic transesterifications of cellulose were studied under homogeneous conditions using the ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl) as a solvent. Cellulose was thus efficiently converted into cellulose esters employing various methyl esters and 10 mol% of 1,5,7-triazabicyclo[4.4.0]dec-5- ene (TBD) as catalyst. 1H NMR analysis of the products revealed up to 2.3 turnovers of the methyl esters per catalyst molecule, leading to degrees of substitution (DS) of up to 0.69. Although a comparatively low turnover number (TON) is observed, the developed methodology represents the first successful homogeneous catalytic reaction on cellulose. Furthermore, the new method is an important step forward in terms of sustainability, since the BMIMCl-DMSO mixture can be recycled and reused for the reaction, and toxic and corrosive chemicals commonly employed for cellulose esterification (such as anhydrides, acid chlorides and bromides, organic bases, all in overstoichiometric amounts) are avoided. To demonstrate the versatility of this transesterification, an aromatic (cellulose benzoate), an aliphatic (cellulose butyrate), and a fatty acid containing cellulose ester (cellulose 10-Undecenoate) were prepared. Additionally, cellulose 10-Undecenoate was successfully used for thiol-ene grafting onto reactions employing two thiols for efficient thiol-ene addition reactions. This journal is © the Partner Organisations 2014.
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Catalytic Oxyfunctionalization of Methyl 10‐undecenoate for the Synthesis of Step‐Growth Polymers
Macromolecular Chemistry and Physics, 2017Co-Authors: Marc Von Czapiewski, Michael A. R. MeierAbstract:An efficient synthesis strategy for the preparation of two renewable polyesters and one renewable polyamide via catalytic oxyfunctionalization of methyl 10-Undecenoate, a castor oil derived platform chemical, is described. The keto-fatty acid methyl ester (keto-FAME) is synthesized applying a cocatalyst-free Wacker oxidation process using a high-pressure reactor system. For this purpose, catalytic amounts of palladium chloride are used in the presence of a dimethylacetamide/water mixture and molecular oxygen as sole reoxidant. The thus derived AB monomers (hydroxy-esters, amine-ester) are synthesized from the obtained keto-FAME through Baeyer–Villiger oxidation and subsequent transesterification, reduction, or reductive amination, respectively. The resulting AB step-growth monomers are then studied in homopolymerizations using 1,5,7-triazabicyclo[4.4.0]dec-5-ene, DBU, and titanium(IV) isopropoxide as transesterification catalyst, yielding polymers with molecular weights (Mn) up to 15 kDa. The polyesters and the polyamide are carefully characterized by FTIR, SEC, 1H-NMR spectroscopy, and differential scanning calorimetry analysis.
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Catalytic transesterification of cellulose in ionic liquids: sustainable access to cellulose esters
Green Chemistry, 2014Co-Authors: Alexander M. Schenzel, Andrea Hufendiek, Christopher Barner-kowollik, Michael A. R. MeierAbstract:Catalytic transesterifications of cellulose were studied under homogeneous conditions using the ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl) as a solvent. Cellulose was thus efficiently converted into cellulose esters employing various methyl esters and 10 mol% of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst. 1H NMR analysis of the products revealed up to 2.3 turnovers of the methyl esters per catalyst molecule, leading to degrees of substitution (DS) of up to 0.69. Although a comparatively low turnover number (TON) is observed, the developed methodology represents the first successful homogeneous catalytic reaction on cellulose. Furthermore, the new method is an important step forward in terms of sustainability, since the BMIMCl–DMSO mixture can be recycled and reused for the reaction, and toxic and corrosive chemicals commonly employed for cellulose esterification (such as anhydrides, acid chlorides and bromides, organic bases, all in overstoichiometric amounts) are avoided. To demonstrate the versatility of this transesterification, an aromatic (cellulose benzoate), an aliphatic (cellulose butyrate), and a fatty acid containing cellulose ester (cellulose 10-Undecenoate) were prepared. Additionally, cellulose 10-Undecenoate was successfully used for thiol–ene grafting onto reactions employing two thiols for efficient thiol–ene addition reactions.
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Cross‐metathesis versus palladium‐catalyzed CH activation: Acetoxy ester functionalization of unsaturated fatty acid methyl esters
European Journal of Lipid Science and Technology, 2012Co-Authors: Marc Von Czapiewski, Oliver Kreye, Hatice Mutlu, Michael A. R. MeierAbstract:Two synthetic approaches to functionalize plant oil derived platform chemicals were investigated. For this purpose, methyl 10-Undecenoate, which can be obtained by pyrolysis of castor oil, was used in olefin cross-metathesis under neat conditions forming an unsaturated a,?-acetoxy ester. A catalyst screening with 11 different ruthenium-based metathesis catalysts was performed, revealing that well-suited catalysts allow for full conversion and very good cross-metathesis selectivity at a loading of only 0.5?mol%. An alternative possibility to the aforementioned synthetic method is a palladium-catalyzed reaction of methyl 10-Undecenoate with acetic acid in the presence of dimethyl sulfoxide. Here, the formation of linear and branched unsaturated acetoxy esters as well as a ketone was observed. The conversion as well as the selectivity of this procedure was studied under different reaction conditions and compared to the cross-metathesis results. Based on the successful functionalization of methyl 10-Undecenoate, methyl oleate was investigated in this palladium-catalyzed C?H activation reaction. Due to the lower reactivity of the internal double bond the desired acetoxy ester was only obtained in moderate conversion in this case. In summary, this study clearly shows that palladium-catalyzed functionalization of unsaturated fatty compounds via C?H activation is an attractive alternative to the well-established olefin cross-metathesis procedure.
Jürgen O. Metzger - One of the best experts on this subject based on the ideXlab platform.
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Manganese(III) acetate induced radical addition of azide to unsaturated fatty compounds
European Journal of Lipid Science and Technology, 2013Co-Authors: Ursula Biermann, Ursula Linker, Jürgen O. MetzgerAbstract:Nitrogen functionalities can be introduced in the alkyl chain of unsaturated fatty compounds by addition of azide mediated by manganese(III) acetate. The respective reaction of methyl oleate 1 containing an internal C,C double bond gave allyl azide 3 as a mixture of 4 regioisomers while the addition of azide to the terminal C,C double bond of methyl 10-Undecenoate 2 afforded the vicinal diazide 6. Azide 3 could be easily converted to the saturated amine 4 by catalytic hydrogenation and to the allyl amines 5 by the Staudinger reaction.
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Lewis Acid Induced Additions to Unsaturated Fatty Compounds
Fett-lipid, 2006Co-Authors: Ursula Biermann, Jürgen O. MetzgerAbstract:Unsaturated fatty compounds such as oleic acid, which are of interest as renewable raw materials, can be functionalized at the C,C-double bond by Lewis acid induced addition reactions. The products are branched and highly functionalized fatty compounds which may have interesting properties. SnCl 4 -induced additions of nitriles to methyl oleate and ethyl 10-Undecenoate give the corresponding esters of the N-acylamino fatty acids. Alkylaluminium halide induced ene additions of formadehyde to unsaturated fatty compounds yield primary homoallylic alcohols.
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ELECTRON TRANSFER INITIATED FREE RADICAL ADDITIONS OF PERFLUOROALKYL IODIDES AND DIIODIDES TO ALKENES
Liebigs Annalen, 2006Co-Authors: Jürgen O. Metzger, Ralf Mahler, Andreas SchmidtAbstract:Perfluoroalkyl iodides were added in very good yields to 1,2-dialkyl substituted double bonds of e.g. petroselinic acid initiated by lead/copper(II) acetate in methanol and by copper without solvent, respectively. Using the new initiator system lead/copper(II) acetate, we also obtained good yields in the additions of perfluoroalkyl iodides to allyl alcohol and ω-unsaturated alcohols and of perfluoroalkyl 1,ω-diiodides to methyl 10-Undecenoate.
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ETHYLALUMINIUM DICHLORIDE INDUCED REACTIONS OF ACETALS WITH UNSATURATED CARBOXYLIC ESTERS : SYNTHESIS OF HOMOALLYL ETHERS
Liebigs Annalen, 1996Co-Authors: Jürgen O. Metzger, Ursula BiermannAbstract:The ethylaluminium dichloride induced reactions of methyl 10-Undecenoate (1) with dimethyl acetals of formaldehyde 2a, acetaldehyde 2b, isobutyraldehyde 2c, and pivaldehyde 2d gave the corresponding homoallyl ethers 3a, 3b, 3c, and 3d in yields of 48–70%. The products were obtained as mixtures of the (E) and (Z) stereoisomers. With formaldehyde dimethyl acetal (2a), methyl oleate (6), and methyl petroselinate (11) gave the corresponding regioisomeric (E)-configured homoallyl ethers 7/8 and 12/13.
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Ane Additions to Unsaturated Fatty Compounds: Thermally Initiated Additions of Alkanes to Methyl 10-Undecenoate†
Fett-lipid, 1995Co-Authors: Jürgen O. Metzger, Fritz BangertAbstract:Alkanes i.e. cyclohexane, n-heptane and alkylaromatics i.e. toluene could be added to methyl 10-Undecenoate to give the respective addition products in a thermally initiated free radical chain reaction (ane-reaction) at supercritical fluid conditions
Pilar Franco - One of the best experts on this subject based on the ideXlab platform.
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Mixed cellulose-derived benzoates bonded on allylsilica gel as HPLC chiral stationary phases: influence of the introduction of an aromatic moiety in the fixation substituent
Tetrahedron-asymmetry, 2003Co-Authors: Jordi Garcés, Laureano Oliveros, Pilar Franco, Cristina MinguillónAbstract:Abstract Several mixed alkenoxybenzoyl/benzoates and 10-undecenoyl/benzoates of cellulose were fixed onto allylsilica gel by the radical coupling of double bonds. The introduction of an aromatic group in the fixation substituent modifies the chiral recognition ability of the resulting chiral stationary phases (CSPs) in comparison with the 10-Undecenoate/benzoate cellulose derivatives. Better enantioselectivity values are achieved when the electronic and geometric characteristics of both substituents, fixating and derivatizing, are similar.
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Carbamates of cellulose bonded on silica gel: Chiral discrimination ability as HPLC chiral stationary phases
Chirality, 1998Co-Authors: Laureano Oliveros, Antonio Senso, Pilar Franco, Cristina MinguillónAbstract:Four cellulose mixed 10-Undecenoate/carbamate derivatives, simultaneously bearing 10-undecenoyl and variously substituted phenylaminocarbonyl groups, were chemically bonded on allylsilica gel. The study of the effect of these substitutions on the performance of the resulting chiral supports, and a comparison with the recently described 10-Undecenoate/3,5-dimethylphenylcarbamate derivative, are presented. In this study heptane/2-propanol or heptane/chloroform mixtures were used as mobile phases. Chirality 10:283–288, 1998. © 1998 Wiley-Liss, Inc.
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Solvent versatility of bonded cellulose-derived chiral stationary phases for high-performance liquid chromatography and its consequences in column loadability
Journal of Chromatography A, 1998Co-Authors: Pilar Franco, Cristina Minguillón, Laureano OliverosAbstract:The chromatographic behaviour of a 10-Undecenoate/3,5-dimethylphenylcarbamate of cellulose bonded on allylsilica gel is tested using four organic mobile-phase modifiers (2-propanol, chloroform, tetrahydrofuran and ethyl acetate). The advantages of the broad choice of solvents offered by this kind of chiral stationary phases and their resistance are discussed. The loadability of the column and its dependence both on the racemate to be resolved and on the solvent used as mobile phase are also discussed.
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Chromatographic resolution of several racemic 9-fluorenyl derivatives on a bonded cellulose derived chiral stationary phase for HPLC
Tetrahedron-asymmetry, 1996Co-Authors: Dolores Velasco, Pilar Franco, Zhanru Yu, Cristina MinguillónAbstract:Abstract The enantiomers of several 9-fluorenyl derivatives have been successfully resolved by HPLC on a chiral stationary phase (CSP) based on a mixed 10-Undecenoate/3,5-dimethylphenylcarbamate of cellulose bonded to allylsilica gel. Previous attempts at resolution, such as NMR methods, GC and the use of a multiple interaction type chiral column for HPLC, were unsuccessful.
