- Stereoselective catalytic hydrogenation of sorbic acid and sorbic alcohol with new Cp*Ru complexes
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The new Cp*Ru complexes [Cp*Ru(η4-MeCH=CHCH=CHCO2H)]+X- (X- = CF3SO3- or [B{C6H3(CF3)2-3,5}4]-) are very effective catalysts for the hydrogenation of sorbic acid to cis-hex-3-enoic acid and of sorbic alcohol to cis-hex-3-en-1-ol (leaf alcohol) under mild conditions in liquid two-phase systems.
- Steines, Stephan,Englert, Ulli,Driessen-Hoelscher, Birgit
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Read Online
- Rh2(R -TPCP)4-catalyzed enantioselective [3+2]-cycloaddition between nitrones and vinyldiazoacetates
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Rhodium-catalyzed reaction of vinyldiazoacetates with nitrones results in a formal [3+2]-cycloaddition to generate 2,5-dihydroisoxazoles with high levels of asymmetric induction. The cascade reaction begins with a vinylogous addition event, followed by an iminium addition ring-closure/hydride migration/alkene isomerization cascade. Dirhodium tetrakis(triarylcyclopropanecarboxylates) are the optimum catalysts for this process.
- Qin, Changming,Davies, Huw M. L.
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Read Online
- Palladium-Catalyzed Amide-Directed Enantioselective Hydrocarbofunctionalization of Unactivated Alkenes Using a Chiral Monodentate Oxazoline Ligand
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A Pd-catalyzed amide-directed enantioselective hydrocarbofunctionalization of unactivated alkenes with C-H nucleophiles has been developed using a chiral monodentate oxazoline (MOXin) ligand. Various indoles react at C3 position with aminoquinoline-coupled 3-alkenamides to give γ addition products in good to excellent yield and enantioselectivity. This study represents an important advance of the development of chiral monodentate oxazoline ligands, which have been underexplored for asymmetric catalysis.
- Wang, Hao,Bai, Zibo,Jiao, Tangqian,Deng, Zhiqiang,Tong, Huarong,He, Gang,Peng, Qian,Chen, Gong
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supporting information
p. 3542 - 3546
(2018/03/21)
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- Characterization of an epoxide hydrolase from the Florida red tide dinoflagellate, Karenia brevis
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Epoxide hydrolases (EH, EC 3.3.2.3) have been proposed to be key enzymes in the biosynthesis of polyether (PE) ladder compounds such as the brevetoxins which are produced by the dinoflagellate Karenia brevis. These enzymes have the potential to catalyze kinetically disfavored endo-tet cyclization reactions. Data mining of K. brevis transcriptome libraries revealed two classes of epoxide hydrolases: microsomal and leukotriene A4 (LTA4) hydrolases. A microsomal EH was cloned and expressed for characterization. The enzyme is a monomeric protein with molecular weight 44 kDa. Kinetic parameters were evaluated using a variety of epoxide substrates to assess substrate selectivity and enantioselectivity, as well as its potential to catalyze the critical endo-tet cyclization of epoxy alcohols. Monitoring of EH activity in high and low toxin producing cultures of K. brevis over a three week period showed consistently higher activity in the high toxin producing culture implicating the involvement of one or more EH in brevetoxin biosynthesis.
- Sun, Pengfei,Leeson, Cristian,Zhi, Xiaoduo,Leng, Fenfei,Pierce, Richard H.,Henry, Michael S.,Rein, Kathleen S.
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- Regioselective ring opening and isomerization reactions of 3,4-epoxyesters catalyzed by boron trifluoride
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Efficient ring opening of 3,4-epoxyesters with alcohols to produce 4-alkoxy-3-hydroxyesters and their isomerization into 4-ketoesters using boron trifluoride as the catalyst are presented. Both transformations are simple and efficient methods for the synthesis of the above named synthetically useful compounds.
- Izquierdo, Javier,Rodriguez, Santiago,Gonzalez, Florenci V.
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supporting information; experimental part
p. 3856 - 3859
(2011/09/19)
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- Method for regio- and stereoselective synthesis of (E)-Β,γ- unsaturated acids from aldehydes under solvent-free conditions
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Synthesis of (E)-β,-γunsaturated acids from aldehydes with malonic acid has been explored under solvent-free conditions. The modified Knoevenagel condensation reaction with N-methyl morpholine (NMM) as catalyst exhibits highly β,-γ regioselectivity and exclusively E-stereoselectivity. A mechanism accounting for both regio- and stereoselectivity has been proposed and preliminarily studied. Copyright Taylor & Francis Group, LLC.
- Zhang, Shi-Jie,Hu, Wei-Xiao
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experimental part
p. 3093 - 3100
(2010/12/19)
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- General and practical conversion of aldehydes to homologated carboxylic acids
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(Chemical Equation Presented) The reaction of aldehydes with trichloromethide followed by sodium borohydride or sodium phenylseleno(triethyl) borate under basic conditions affords homologated carboxylic acids in high yields. This operationally simple procedure provides a practical, efficient alternative to other homologation protocols. The approach is compatible with sensitive aldehydes including enals and enolizable aldehydes. It also offers convenient access to α-monodeuterated carboxylic acids.
- Cafiero, Lauren R.,Snowden, Timothy S.
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supporting information; experimental part
p. 3853 - 3856
(2009/07/01)
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- Process for preparing cis alkenes and new catalysts therefor
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In a method for preparation of cis-alkenes (I) by hydrogenating conjugated, non-cyclic dienes (II) in presence of homogeneously soluble transition metal catalyst (III), the new feature is that (III) is prepared in situ. In a method for preparation of cis-alkenes (I) by hydrogenating conjugated, non-cyclic dienes (II) in presence of homogeneously soluble transition metal catalyst (III), the new feature is that (III) is prepared in situ. (III) are of formulae (IIIa) or (IIIb). M = in (IIIa), a transition metal of Group VI in zero oxidation state, or in (IIIb) a metal of Group VIII in +2 oxidation state, Group IX in +1 oxidation state or Group X in +2 oxidation state; L1 = polydentate neutral or anionic ligand; L2 and L3 = together a conjugated, non-cyclic diene ligand; L4 = monodentate neutral ligand; L5 = polydentate neutral ligand; X = anion; and n = 1 or 2. Independent claims are also included for the following: (1) transition metal complex (C) for stereoselective hydrogenation of conjugated dienes to cisoid compounds that comprises a central ruthenium(II), an eta5 ligand, a bidentate, non-cyclic conjugated diene ligand and optionally a non-coordinating counterion for electrical neutrality, provided that when the ligand is pentamethylcyclopentadienyl (CpMe5) and the diene is sorbic acid, then the counterion is not triflate (trifluoromethylsulfonate) nor the BARF anion; and (2) methods for preparing specific (C).
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Page/Page column 9
(2010/02/05)
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- Stereoselective access to functionalized β-γ unsaturated acids
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Stereoselective synthesis of vinylstannanes bearing a carboxylic acid function was achieved from β-γ alkynoic acids via hydrostannation, stannylcupration or silastannation reactions. Regioselectivity is highly dependent on the nature of the stannylanions used and on protection of the carboxylic acid function.
- Thibonnet, Jér?me,Abarbri, Mohamed,Parrain, Jean-Luc,Duchêne, Alain
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p. 4433 - 4441
(2007/10/03)
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- Chromium catalyzed oxidation of (homo-)allylic and (homo-)propargylic alcohols with sodium periodate to ketones or carboxylic acids
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Primary and secondary (homo-)allylic and (homo-)propargylic alcohols can be oxidized under slightly acidic conditions at or below room- temperature with sodium periodate in the presence of sodium dichromate as the catalyst to the corresponding carboxylic acids and ketones, respectively.
- De Vondervoort, Lizette Schmieder-Van,Bouttemy, Sabine,Padrón, José M.,Le Bras, Jean,Muzart, Jacques,Alsters, Paul L.
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p. 243 - 246
(2007/10/03)
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- Synthesis of different deuterated carboxylic acids from unsaturated acids promoted by samarium diiodide and D2O
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An easy, and rapid reduction of the C=C bond of α,β-unsaturated acids by means of samarium diiodide in the presence of D2O provides an efficient method for synthesizing 2,3-dideuterio acids. Starting from alka-2,4-dienoic acids, (E)-α,δ-dideuterio-βγ-unsaturated acids are obtained, the new C=C bond being generated with complete diastereoselectivity. When H2O is used instead of D2O, saturated carboxylic acids and (E)-β,γ-unsaturated acids are isolated. A mechanism to explain each synthesis has been proposed.
- Concellon, Jose M.,Rodriguez-Solla, Humberto
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p. 4493 - 4497
(2007/10/03)
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- An ionic liquid as catalyst medium for stereoselective hydrogenations of sorbic acid with ruthenium complexes
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The ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate (bmim PF6) (6) has been studied as catalyst medium for biphasic homogeneous hydrogenations of sorbic acid (1). As catalyst we used the Cp*-ruthenium-complex [Cp*Ru(η4-CH3-CH=CH-CH=CH-COOH) (CF3SO3)] which efficiently enables the stereoselective hydrogenation of sorbic acid leading to the formation of cis-3-hexenoic acid (3) in selectivities of up to 90% with turnover frequencies of up to 1100 h-1. Compared to other biphasic systems the hydrogenation in bmim PF6 proceeds with enhanced activity. The kinetics can be described with a Michaelis-Menten-equation, and the activation energy for the whole process was determined to be EA = 78 ± 5 kJ/mol. Wiley-VCH Verlag GmbH, 2000.
- Steines, Stephan,Wasserscheid, Peter,Driessen-Hoelscher, Birgit
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p. 348 - 354
(2007/10/03)
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- Conjugate addition of organolithium reagents to α,β-unsaturated carbocyclic acids
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Conjugate addition of primary, secondary, tertiary alkyi and phenyl lithium reagents to 2-alkenoic acids affords good yields of branched saturated carboxylic acids. Methyl groups at the α- and β-carbon of the 2-alkenoic acid decrease reactivity as acceptors, and foster deprotonation, respectively. The lithium enediolate resulting from the conjugate addition can react with electrophiles. PM3 calculations are in agreement with the substituent effects.
- Aurell, Maria Jose,Domingo, Luis Ramon,Mestres, Ramon,Munos, Elena,Zaragoza, Ramon Jose
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p. 815 - 830
(2007/10/03)
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- SiO2 catalysed expedient synthesis of [E]-3-alkenoic acids in dry media
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Aliphatic aldehydes with α-hydrogens and malonic acid undergo decarboxylative condensation on the surface of SiO2 when subjected to microwave irradiation generating βγ-unsaturated acids in high yields.
- Kumar, H.M. Sampath,Reddy, B.V. Subba,Reddy, E. Jagan,Yadav
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p. 2401 - 2404
(2007/10/03)
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- Selective two-phase-hydrogenation of sorbic acid with novel water soluble ruthenium complexes
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Neutral and cationic water soluble Cp*-ruthenium-complexes of the type [Cp*Ru(CO)Cl(PR3)] and [Cp*Ru(CO)(PR3)]CF3SO3 (R=CH2OH, (CH2)3OH, Ph-m-SO3Na) have been synthesized for the first time and have been used as catalysts in two-phase-hydrogenations. The neutral complexes have been fully characterized. But the cationic complexes which have not been isolated are effective catalysts for the selective hydrogenation of sorbic acid in water/n-heptane leading to the formation of cis-3-hexenoic acid and trans-3-hexenoic acid.
- Driessen-Hoelscher, Birgit,Heinen, Joerg
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p. 141 - 146
(2007/10/03)
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- Nitrolysis of carboxylic t-butyl and 1-adamantyl esters
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A cheap, less problematic, efficient and selective reagent for the removal of the t-butyl and 1-adamantyl protecting groups from carboxylic esters was found to be commercial 100% HNO3 in CH2Cl2. Incidentally, 1,1- dimethylethyl nitrate and tricyclo[3.3.1.13,7]dec-1-yl (1-adamantyl) nitrate are coproducts in a clean reaction. The procedure is in many ways superior to the method employing CF3COOH.
- Strazzolini, Paolo,Dali'Arche, Maria Grazia,Giumanini, Angelo G.
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p. 9255 - 9258
(2007/10/03)
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- Thermodynamic and nuclear magnetic resonance study of the reactions of α- and β-cyclodextrin with acids, aliphatic amines, and cyclic alcohols
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Titration calorimetry was used to determine equilibrium constants and standard molar enthalpy, Gibbs energy, and entropy changes for the reactions of a series of acids, amines, and cyclic alcohols with α- and β-cyclodextrin. The results have been examined in terms of structural features in the ligands such as the number of alkyl groups, the charge number, the presence of a double bond, branching, and the presence of methyl and methoxy groups. The values of thermodynamic quantities, in particular the standard molar Gibbs energy, correlate well with the structural features in the ligands. These structural correlations can be used for the estimation of thermodynamic quantities for related reactions. Enthalpy-entropy compensation is evident when the individual classes of substances studied herein are considered, but does not hold when these various classes of ligands are considered collectively. The NMR results indicate that the mode of accommodation of the acids and amines in the α-cyclodextrin cavity is very similar, but that the 1-methyl groups in 1-methylhexylamine and in 1-methylheptylamine and the N-methyl group in N-methylhexylamine lie outside the α-cyclodextrin cavity. This latter finding is consistent with the calorimetric results. Many of the thermodynamic and NMR results can be qualitatively understood in terms of van der Waals forces and hydrophobic effects.
- Rekharsky, Mikhail V.,Mayhew, Martin P.,Goldberg, Robert N.,Ross, Philip D.,Yamashoji, Yuko,Inoue, Yoshihisa
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- An electrochemical approach to some insect pheromones with (E)-alkene moiety
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An easy access to some Lepidopteran pheromones containing (E)-alkene moiety via anodic oxidation of a partially neutralized mixture of trans-3-alkenoic acids and methyl hydrogen carboxylates has been described.
- Singh, Krishna Nand,Singh, Manorama,Misra, Ram Achal
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p. 431 - 434
(2007/10/02)
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- Palladium(II) catalyzed novel rearrangement of 1-allyloxy-1-siloxycyclopropanes
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Pd(II) salts catalyze the rearrangement of 1-allyloxy-1-siloxycyclopropanes to provide a mixture of Δ2-, Δ3- and Δ4-hexenonic acids. This rearrangement proceeds via a double bond isomerization followed by a ring opening of
- Yasui, Kengo,Fugami, Keigo,Tanaka, Shuji,Tamaru, Yoshinao,Ii, Atsuhiko,Yoshida, Zen-Ichi,Saidi, Mohamad R.
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p. 789 - 792
(2007/10/02)
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- TRANS-NITRILATION IN THE SERIES OF 2-ALKENOIC ACIDS
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In the case of the reaction of trans-2-hexenoic acid with acetonitrile it was established that acids of the olefinic series enter into trans-nitrilation with aliphatic nitriles; the reaction is complicated by thermal isomerization both of the initial acid and of the reaction products, i.e., the corresponding nitrile and N-acylamide.Under the conditions of the reaction of trans-2-hexenoic acid with deuteroacetonitrile-d3 1,3-hydride-deuteride shifts occur in the intermediate compounds (the N-acylamides).This leads to a redistribution of the deuterium atoms between the products of the investigated reaction.
- Polivin, Yu. N.,Karakhanov, R. A.,Vinokurov, V. A.,Mikaya, A. I.,Silin, M. A.,Makarshin, S. V.
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p. 1795 - 1798
(2007/10/02)
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- Regioselective Hydrogenation of Conjugated Dienes Catalyzed by Hydridopentacyanocobaltate Anion using β-Cyclodextrin as the Phase-Transfer Agent and Lanthanide Halides as Promotors
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β-Cyclodextrin is a useful phase-transfer agent for the hydrogenation of conjugated dienes to monoolefins catalyzed by the in situ generated hydridopentacyanocobaltate anion.This reaction, which usually proceeds by 1,2-addition to the diene, is promoted by cerium or lanthanum chloride.Polyethyleneglycol (PEG-400), with or without added lanthanide, can also used as the phase-transfer agent for the reduction process.
- Lee, Jong-Tae,Alper, Howard
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p. 1854 - 1856
(2007/10/02)
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- Regio- and Stereoselective Ring Opening of ω-Alkenyllactones Using Organocopper Reagents
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New synthetic methods are described for the preparation of (E)-3, (E)-4, and (E)-5-alkenoic acids by the regio- and stereoselective ring opening of β, γ, and δ-lactones with unsaturated substituents at the ω-position using organocopper reagents such as halomagnesium diorganocuprates or Grignard reagents in the presence of copper(I) iodide.Both the organocopper reagents with primary, secondary, tertiary alkyl, and phenyl groups gave the corresponding carbon homologated alkenoic acids in good yields.Alkadienoic acids were also obtained in good yields by the reactions of ω-alkenyllactones with divinyl- and diallylcuprates.Utilizing the ring opening of β-isopropenyl-β-propiolactone, homoterpenoid carboxylic acids were easly obtained in good yields.The ring opening of β-(1-chlorovinyl)-β-propiolactone afforded 4-chloro-3-alkenoic acids which were easly transformed to 4-oxoalkanoic acids and 4-oxo-2-alkenoic acids.
- Kawashima, Masatoshi,Sato, Toshio,Fujisawa, Tamotsu
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p. 3255 - 3264
(2007/10/02)
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- MODIFIED KNOEVENAGEL CONDENSATIONS. SYNTHESIS OF (E)-3-ALKENOIC ACIDS.
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Condensation of aliphatic aldehydes with a three molar excess of malonic acid and 0.001 mole piperidinium acetate in refluxing xylene, with continuous removal of the water formed, gave almost exclusively (E)-3-alkenoic acids, in good yield (60-85percent) and of high stereochemical purity (95-99percent).
- Ragoussis, Nikitas
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