- Enantioselective and Diastereodivergent Synthesis of Spiroindolenines via Chiral Phosphoric Acid-Catalyzed Cycloaddition
-
A diastereodivergent and enantioselective synthesis of chiral spirocyclohexyl-indolenines with four contiguous stereogenic centers is achieved by a chiral phosphoric acid-catalyzed cycloaddition of 2-susbtituted 3-indolylmethanols with 1,3-dienecarbamates. Modular access to two different diastereoisomers with high enantioselectivities was obtained by careful choice of reaction conditions. Their functional group manipulation provides an efficient access to enantioenriched spirocyclohexyl-indolines and -oxindoles. The origins of this stereocontrol have been identified using DFT calculations, which reveal an unexpected mechanism compared to our previous work dealing with enecarbamates.
- Gandon, Vincent,Masson, Géraldine,Mati?i?, Mateja,Neuville, Luc,Van Elslande, Elsa,Varlet, Thomas
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supporting information
p. 11611 - 11619
(2021/08/16)
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- Ruthenium-Catalyzed Oxidative Cross-Coupling Reaction of Activated Olefins with Vinyl Boronates for the Synthesis of (E, E)-1,3-Dienes
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An oxidative cross-coupling reaction between activated olefins and vinyl boronate derivatives has been developed for the highly stereoselective construction of synthetically useful (E,E)-1,3-dienes. The highlight of this reaction is that exclusive stereoselectivity (only E,E-isomer) was achieved from a base-free, ligand-free, and mild catalytic condition with a less expensive [RuCl2(p-cymene)]2 catalyst.
- Dethe, Dattatraya H.,Beeralingappa, Nagabhushana C.,Uike, Amar
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p. 3444 - 3455
(2021/02/16)
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- Protection of COOH and OH groups in acid, base and salt free reactions
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We report an iron-catalyzed general functional group protection method with inexpensive reagents. This environmentally benign process does not use acids or bases, and does not produce waste products. Further purification beyond filtration and evaporation is, in most cases, unnecessary. Free COOH and OH groups can be protected in a one-pot reaction.
- Zhu, Xiaotao,Qian, Bo,Wei, Rongbiao,Huang, Jian-Dong,Bao, Hongli
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supporting information
p. 1444 - 1447
(2018/04/12)
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- Efficient flow fischer esterification of carboxylic acids with alcohols using sulfonic acid-functionalized silica as supported catalyst
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Flow Fischer esterification of carboxylic acids using hydroxy-substituted sulfonic acid-functionalized silica (HOSAS) packed into a stainless steel column reactor was investigated. HO-SAS well catalyzed flow esterification of long chain carboxylic acids with methanol within 3min of residence time at 110°C, and the methyl esters were quantitatively obtained. The flow esterification protocol was applied to the synthesis of a variety of esters (19 examples) and scalable synthesis was also successful.
- Furuta, Akihiro,Fukuyama, Takahide,Ryu, Ilhyong
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p. 607 - 612
(2017/06/19)
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- Studies on [2?+?3] cycloaddition reaction of nitrile oxides to linear dipolarophiles bearing multiple double bonds
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Abstract: Site selectivity, regioselectivity, and stereoselectivity of [2?+?3] cycloaddition of benzonitrile oxides to polyunsaturated esters were examined. Site selectivity was correlated with electron charges of unsaturated carbon atoms. Structure of the products has been established by an extensive application of 1H and 13C NMR spectroscopy and electrospray ionization mass spectrometry. Graphical abstract: [Figure not available: see fulltext.]
- Gucma, Miros?aw,Go??biewski, W. Marek,Michalczyk, Alicja Katarzyna
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p. 1809 - 1818
(2016/09/28)
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- Copper-Catalyzed O-Methylation of Carboxylic Acids Using DMSO as a Methyl Source
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A copper-catalyzed O-methylation of carboxylic acids using dimethyl sulfoxide (DMSO) as the methyl source is disclosed. This transformation exhibits a broad substrate scope and excellent functional group tolerance. Mechanistic studies indicate that a methyl radical is generated from dimethyl sulfoxide in the reaction process.
- Jia, Jing,Jiang, Qing,Zhao, An,Xu, Bin,Liu, Qiang,Luo, Wei-Ping,Guo, Can-Cheng
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p. 421 - 428
(2016/01/28)
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- On the Functional Group Tolerance of Ester Hydrogenation and Polyester Depolymerisation Catalysed by Ruthenium Complexes of Tridentate Aminophosphine Ligands
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The synthesis of a range of phosphine-diamine, phosphine-amino-alcohol, and phosphine-amino-amide ligands and their ruthenium(II) complexes are reported. Five of these were characterised by X-ray crystallography. The activities of this collection of catalysts were initially compared for the hydrogenation of two model ester hydrogenations. Catalyst turnover frequencies up to 2400 h-1 were observed at 85 °C. However, turnover is slow at near ambient temperatures. By using a phosphine-diamine RuII complex, identified as the most active catalyst, a range of aromatic esters were reduced in high yield. The hydrogenation of alkene-, diene-, and alkyne-functionalised esters was also studied. Substrates with a remote, but reactive terminal alkene substituent could be reduced chemoselectively in the presence of 4-dimethylaminopyridine (DMAP) co-catalyst. The chemoselective reduction of the ester function in conjugated dienoate ethyl sorbate could deliver (2E,4E)-hexa-2,4-dien-1-ol, a precursor to leaf alcohol. The monounsaturated alcohol (E)-hex-4-en-1-ol was produced with reasonable selectivity, but complete chemoselectivity of C=O over the diene is elusive. High chemoselectivity for the reduction of an ester over an alkyne group was observed in the hydrogenation of an alkynoate for the first time. The catalysts were also active in the depolymerisation reduction of samples of waste poly(ethylene terephthalate) (PET) to produce benzene dimethanol. These depolymerisations were found to be poisoned by the ethylene glycol side product, although good yields could still be achieved. A simple catalyst for difficult reductions: Ruthenium complexes of P,N,N and P,N,O ligands catalyse the reduction of esters with high activities. The Ru complex of a phosphine-diamine ligand (see scheme) has been found to be a good catalyst for reducing alkene-, diene-, and alkyne-functionalised esters, displaying good activity and chemoselectivity. This catalyst was also active in the hydrogenation of waste poly(ethylene terephthalate) (PET).
- Fuentes, José A.,Smith, Samuel M.,Scharbert, M. Theresa,Carpenter, Ian,Cordes, David B.,Slawin, Alexandra M. Z.,Clarke, Matthew L.
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supporting information
p. 10851 - 10869
(2015/07/20)
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- Extending the stetter reaction with 1,6-acceptors
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Pace Stetter: A new N-heterocyclic carbene (NHC)-catalysed transformation is described-the intramolecular vinylogous Stetter reaction. This transformation can be effected with both thiazolium and triazolium-based catalysts, using aromatic and aliphatic aldehydes, employing α,β,γ,δ- unsaturated esters, ketones, phosphonates and N-acylpyrroles, and can be conducted enantioselectively (see scheme). Copyright
- Law, Katherine R.,McErlean, Christopher S. P.
-
supporting information
p. 15852 - 15855
(2014/04/03)
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- New and concise syntheses of the bicyclic oxamazin core using an intramolecular nitroso diels-alder reaction and ring-closing olefin metathesis
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Herein two new and concise synthetic approaches for making an unsaturated bicyclic oxamazin core are reported. The first involves the use of an intramolecular Diels-Alder reaction to form both of the fused rings in one step. The second approach incorporates ring-closing olefin metathesis in the final step to form the second fused ring of the core. The scope of the second approach was also expanded further to afford larger ringed bicyclic systems.
- Watson, Kyle D.,Carosso, Serena,Miller, Marvin J.
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supporting information
p. 358 - 361
(2013/03/13)
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- A novel catalytic asymmetric route towards skipped dienes with a methyl-substituted central stereogenic carbon
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A highly efficient method for the enantioselective synthesis of 1,4-dienes (skipped dienes) with a methyl-substituted central stereogenic carbon using copper-catalysed asymmetric allylic alkylation of diene bromides was developed. Excellent regio- and enantioselectivity (up to 97 : 3 SN2′/ SN2 ratio and 99% ee) were achieved with broad substrate scope. The Royal Society of Chemistry 2013.
- Huang, Yange,Fananas-Mastral, Martin,Minnaard, Adriaan J.,Feringa, Ben L.
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supporting information
p. 3309 - 3311
(2013/06/04)
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- Concise and highly selective asymmetric synthesis of acosamine from sorbic acid
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Diastereoselective conjugate addition of lithium (R)-N-benzyl-N-(α- methylbenzyl)amide to tert-butyl sorbate and subsequent chemo- and diastereoselective ammonium-directed olefinic oxidation of the resultant conjugate addition product {tert-butyl (3S,αR)-3-[N-benzyl-N-(α- methylbenzyl)amino]hex-4-ene} have been used as the key steps in a concise and highly selective asymmetric synthesis of the 2,3,6-trideoxy-3-aminohexose l-acosamine. This sequence of two chemical operations allows rapid assembly of the molecular architecture and facilitates the de novo asymmetric synthesis of methyl N,O-diacetyl-α-l-acosaminide in only 7 steps from commercially available sorbic acid in 15% overall yield.
- Bagal, Sharan K.,Davies, Stephen G.,Fletcher, Ai M.,Lee, James A.,Roberts, Paul M.,Scott, Philip M.,Thomson, James E.
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scheme or table
p. 2216 - 2220
(2011/05/09)
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- The acyl nitroso Diels-Alder (ANDA) reaction of sorbate derivatives: An X-ray and 15N NMR study with an application to amino-acid synthesis
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We present a study of the acyl nitroso Diels-Alder (ANDA) reaction of sorbate esters and sorbic alcohol derivatives, using alkoxycarbonyl nitroso dienophiles. An optimisation of the reaction conditions for ethyl sorbate is first presented, and the product is used in an efficient synthesis of 5-methylornithine. Structure-reactivity trends in sorbic alcohol (E,E-2,4-hexadien-1-ol) and its acylated analogues are then discussed. We present single-crystal X-ray structural proof for key adducts in both series and present in detail a novel HMBC/HSQC (1H-15N) criterion for ready distinction of regioisomers arising from such ANDA reactions.
- Bollans, Lee,Bacsa, John,Iggo, Jonathan A.,Morris, Gareth A.,Stachulski, Andrew V.
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supporting information; experimental part
p. 4531 - 4538
(2009/12/25)
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- Asymmetric synthesis of Sedum alkaloids via lithium amide conjugate addition
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Conjugate addition of lithium (R)-N-allyl-N-(α-methylbenzyl)amide or lithium (R)-N-but-3-enyl-N-(α-methylbenzyl)amide to an alkyl hexa-2,4-dienoate or alkyl hepta-2,6-dienoate, followed by ring-closing metathesis of the olefin functionalities within the resultant β-amino ester, generates a range of diastereoisomerically pure azacycles in good yield. These homochiral templates are readily transformed to a range of piperidine alkaloids of the Sedum family, and the corresponding five-, seven- and eight-membered ring homologues.
- Davies, Stephen G.,Fletcher, Ai M.,Roberts, Paul M.,Smith, Andrew D.
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experimental part
p. 10192 - 10213
(2010/02/28)
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- METHOD OF RAPID METHYLATION OF ALKENE COMPOUND AND KIT FOR PET TRACER PREPARATION USING THE SAME
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To provide a method of rapid methylation of alkenes, which is applicable to the preparation of a PET tracer and which enables alkenes to be methylated through cross coupling between SP2 (alkenyl) and SP3 (alkyl) carbon atoms rapidly and in a high yield. Methyl iodide and an alkenyltrialkylstannane are subjected to cross coupling in an aprotic polar solvent in the presence of a palladium complex having a valence of 0, a phosphine ligand, a cuprous halide, and a carbonate and/or alkali metal fluoride.
- -
-
Page/Page column 5; 6
(2008/12/07)
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- Quantitative structure-activity relationship studies for prediction of antimicrobial activity of synthesized 2,4-hexadienoic acid derivatives
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A new series of 2,4-hexadienoic acid derivatives (S1-S42) has been synthesized and evaluated as antimicrobial agents against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Candida albicans, and Aspergillus niger. Quantitative structure-activity relationship (QSAR) investigation using Hansch analysis was applied to find out correlation between antimicrobial activities with physicochemical properties of the synthesized compounds. Various physicochemical descriptors and experimentally determined minimum inhibitory concentration values for different microorganisms were used as independent and dependent variables, respectively. The QSAR revealed that topological parameters especially molecular connectivity indices (χ2, 0χv, 2χv) were found to have overall significant correlation with antimicrobial activity of 2,4-hexadienoic acid derivatives. The statistical results of training set, cross-validated r2 and conventional r values gave reliability to the prediction of molecules with activity using QSAR models.
- Narasimhan, Balasubramanian,Judge, Vikramjeet,Narang, Rakesh,Ohlan, Ruchita,Ohlan, Sucheta
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p. 5836 - 5845
(2008/03/18)
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- A de novo asymmetric approach to achiral deoxy-melodorinol analogues
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A short and highly efficient route to deoxy-Melodorinol analogues has been developed. The key to the overall transformation is the use of an enantioselective Sharpless asymmetric dihydroxylation of an (Z,E)-dienoate to control the regioselectivity of the dihydroxylation reaction and a Mitsunobu elimination reaction to control the E-stereochemistry of the,δ-double bond. The highly efficient synthesis stereoselectively prepared four analogues in 3 steps from 4-substituted crotonaldehydes.
- Ahmed, Md. Moinuddin,Akhmedov, Novruz G.,Cui, Hu,Friedrich, Dirk,O'Doherty, George A.
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p. 223 - 233
(2008/02/02)
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- HISTONE DEACETYLASE INHIBITORS
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The present invention provides histone deacetylase inhibitors of general formula (I), process for the preparation of such compounds and uses of the compounds in medicine.
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- A Simple and Efficient Esterification Method
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A convenient and practical esterification was realized and this reaction proceeded without a dehydrating reagent or water removal equipment. The synthesis of esters by reaction of carboxylic acids with various alcohols such as methyl, ethyl, isopropyl, isobutyl, allyl, benzyl, propargyl and decanyl alcohols were achieved with a catalytic amount of CBr4 under refluxing reaction condition.
- Ming-Yi, Chen,Lee, Adam Shih-Yuan
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p. 103 - 108
(2007/10/03)
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- Geometrically specific hydrogen transfer in the reaction of terminally alkyl-substituted 1,3-dienes with 1,4-quinones
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Reaction of certain geometrically defined 1,1-dioxy-4-alkyl- and -4,4-dialkyl-substituted buta-l,3-dienes with halogenated quinones does not involve Diels-Alder or Michael addition chemistry. Instead, rapid competitive oxidation of the dienes to give 2,4-dienoate esters was observed. This new reaction involves strong spatial association between diene and quinone, hydrogen being transferred specifically from the (4E)-alkyl group. Its scope is compared with addition of the same terminally substituted dienes towards the reactive non-quinonoid dienophile tetracyanoethylene. CSIRO 2000.
- Cameron, Donald W.,Heisey, Ross M.
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p. 109 - 121
(2007/10/03)
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- Highly cis-selective Horner-Wadsworth-Emmons (HWE) reaction of methyl bis(2,4-difluorophenyl) phosphonoacetate
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Of the previously reported Homer-Wadsworth-Emmons (HWE) reaction, the olefination of methyl bis(2,4-difluorophenyl)phosphonoacetate (1a) with various aldehydes gave unsaturated esters in the highest cis-selectivity.
- Kokin, Keisuke,Motoyoshiya, Jiro,Hayashi, Sadao,Aoyama, Hiromu
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p. 2387 - 2392
(2007/10/03)
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- Palladium-Catalyzed Reactions of Alkenyloxiranes with Carbon Monoxide
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Reaction of alkenyloxiranes with carbon monoxide in the presence of palladium catalysts gives unsaturated esters, β-lactones, dienes, and allylic alcohols.The selectivity of the reaction depends on the nature of the alkenyloxiranes.Carbonylation products were obtained in the reaction of terminal alkenyloxiranes and alkenyloxiranes having electron-donating substituents, whereas carbonylation scarcely took place in the reaction of alkenyloxiranes having electron-withdrawing groups; dienes and allylic alcohols were produced instead of carbonylation products.
- Shimizu, Isao,Maruyama, Takashi,Makuta, Toshiyuki,Yamamoto, Akio
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p. 2135 - 2138
(2007/10/02)
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- Addition of Organocopper Reagents to Cyclic Sulfites or Carbonates of γ,δ-Dihydroxy (E)-α,β-Enoates
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Reaction of cyclic sulfites or carbonates of γ,δ-dihydroxy (E)-α,β-enoates with R2Cu(CN)Li2, BF3; RCu(CN)Li, BF3 (R=Me-, n-Bu-) afforded either diastereoselective SN2' products or reductive elimination product depending on reaction conditions.Addition of R2Cu(CN)Li2, BF3 (R=Me-, n-Bu-) to cyclic sulfite (1) or cyclic carbonate (3) (inverse addition) afforded highly regio-, (E)-stereo- and diastereoselectivity α-alkylation products (6 and 8).By using this methodology, (2S, 5S)-trans-2-methyl-5-hexanolide, the pheromone of the carpenter bee Xylocopa hirutissima was synthesized.
- Kang, Suk-Ku,Park, Young-Won,Lee, Dong-Ha,Sim, Hyeong-Su,Jeon, Jae-Hoon
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p. 705 - 708
(2007/10/02)
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- Diels alder reactions of P-chloro (bistrimethylsilyl) methylene phosphine
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The electrophilic dienophile, P-chloro (bistrimethylsilyl) methylene phosphine reacts with electron poor or rich dienes to give the [47π + 2π] cycloadducts whose structures are determined by NMR. The regiospecificity of the reaction is satisfactorily predicted by the second order perturbation theory.
- Abbari, Mustafa,Cosquer, Paul,Tonnard, Francois,Ko, Yeung Yat Cheng Yeung Lam,Carrie, Roben
-
-
- A CONVENIENT STEREOSELECTIVE SYNTHESIS OF CONJUGATED DIENOIC ESTERS AND AMIDE
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(2E,4E)-Dienoic esters and amides could be synthesized via the stereoselective isomerization of the corresponding 2-ynoic esters and amides, respectively, under the catalysis of ruthenium or iridium complexes.
- Ma, Dawei,Lu, Xiyan
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p. 3189 - 3198
(2007/10/02)
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- Vinylcyclobutane-Cyclohexane Rearrangements: Zwitterions as Discrete Intermediates
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Donor-acceptor-substituted vinylcyclobutanes 1 rearrange to cyclohexenes 2 at temperatures between 20 and 195 deg C.In solvents of low polarity, cycloreversion competes with ring enlargement.Under acidic conditions, addition of nucleophiles to vinylcyclobutanes 1 with ring opening is observed.Stereospecificity of rearrangement and cycloreversion are functions of temperature, solvent polarity and acid catalysis.Strong dependence on solvent polarity is found for the rates of both reactions.The mechanisms of the thermally induced and acid-catalyzed reactions are discussed on the basis of stereospecificity, kinetic parameters and trapping of intermediates.Two structurally different zwitterions 13 and 14 are proposed as intermediates, one of which is responsible for rearrangement, the other for diastereomerization and cycloreversion.
- Gruseck, Ursula,Heuschmann, Manfred
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p. 1911 - 1926
(2007/10/02)
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- FACILE SYNTHESIS OF (2E,4E)-DIENOIC ESTERS VIA STEREOSELECTIVE ISOMERIZATION OF 2-YNOIC ESTERS
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(2E,4E)-Dienoic esters were synthesized stereoselectively from the corresponding 2-ynoic esters in high yield under the catalysis of an iridium hydride or ruthenium hydride complex.
- Ma, Dawei,Lu, Xiyan
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p. 843 - 844
(2007/10/02)
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- An Efficient One-Pot Preparation of 2,4-Pentadienoic Esters from α,β-Unsaturated Aldehydes
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α,β-Unsaturated aldehydes react with monoalkyl malonates in pyridine with a catalytic amount of dimethylaminopyridine (DMAP) in a regio- and stereoselective process to yield almost exclusively 2,4-pentadienoic esters with essentially (and in many cases exclusively) the 2E-stereochemistry.
- Rodriguez, J.,Waegell, B.
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p. 534 - 535
(2007/10/02)
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- Stereoselective Synthesis of (2E,4E)- and (2Z,4E)-2,4-Alkadienoates by the Ester Enolate Claisen Rearrangement of (E)-1-Alkyl-3-trimethylsilyl-2-propenyl Glycolates Followed by the Peterson Reaction
-
The ester enolate Claisen rearrangement of (E)-1-alkyl-3-trimethylsilyl-2-propenyl glycolates gave (E)-erythro-2-hydroxy-3-trimethylsilyl-4-alkenoates with high diastereoselectivity, which were stereoselectively converted into (2E,4E)- and (2Z,4E)-2,4-alkadienoates by the Peterson reaction.
- Sato, Toshio,Tsunekawa, Hiroshi,Kohama, Hiromasa,Fujisawa, Tamotsu
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p. 1553 - 1556
(2007/10/02)
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- Lewis Acid Catalysis of Photochemical Reactions. 5. Selective Isomerization of Conjugated Butenoic and Dienoic Esters
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The effects of Lewis and Broensted acids upon the photoisomerization reactions of several conjugated butenoic and dienoic esters have been investigated.Lewis acid inhibit the photochemical deconjugation of α,β- to β,γ-unsaturated butenoic esters and shift the photoequilibrium between E and Z isomers toward the Z isomer.As such, irradiation of E α,β-unsaturated esters in the presence of EtAlCl2 provides a convenient method for the preparation of the thermodynamically less stable Z isomer.Irradiation of methyl (E,E)-2,4-hexadienoate and methyl (E,E)-5-phenyl-2,4-pentadienoate in the absence of added catalysts results in nonselective E,Z isomerization to give mixtures of all four stereoisomers in roughly comparable yields.In the presence of the Broensted acid trifluoroacetic acid, quantitative conversion of methyl 2,4-hexadienoates to methyl 3,4-hexadienoate is observed.The acid serves as a catalyst for the thermal 1,3-hydrogen shift of an allenic enol ester formed via a photochemical 1,5-hydrogen shift of the conjugated esters.Irradiation of the ground-state complexes of the conjugated esters with the Lewis acids EtAlCl2 or BF3 results in selective E,Z isomerization about the α,β-double bond in methyl 2,4-hexadienoate and the γ,δ-double bond in methyl 5-phenyl-2,4-pentadienoate.The mechanistic bases for the observed effects of Lewis acids are selective excitation of the more strongly absorbing E complex and more efficient isomerization of the excited E vs.Z complex.
- Lewis, Frederick D.,Howard, Daniel K.,Barancyk, Steven V.,Oxman, Joe D.
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p. 3016 - 3023
(2007/10/02)
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- NICKEL-CATALYZED OLIGOMERIZATION OF FUNCTIONALIZED CONJUGATED DIENES
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The cyclodimerization of several functionalized dienes with nickel(0) catalysts has been studied.When a functional group, such as a methoxycarbonyl or a trimethylsiloxy group, is bonded directly to the terminal carbon of the diene grouping, a completely regio- and stereo-selective dimerization is observed and trans-1,2-disubstituted cycloocta-3,7-dienes are formed in good yields (80-90percent).When one carbon atom separates the functional group from the diene group, the yield drops significantly (to 30percent), and the stereoselectivity and the clean nature of the reaction are completely lost.The effect of the nature of the nickel catalyst and the influence of the reductive organoaluminum species are discussed.The particular structure and the stereochemical features of the cyclooctadiene derivatives allow a better understanding of the various steps involved in the catalytic process.A reaction mechanism is proposed.
- Tenaglia, A.,Brun, P.,Waegell, B.
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p. 343 - 358
(2007/10/02)
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- SYNTHESIS AND PHASE-TRANSFER MEDIATED ALKYLATIONS OF 2-DIETHYLAMINO-4-PHENYLSULFONYL-2-BUTENENITRILE AN EFFICIENT HOMOENOLATE EQUIVALENT
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The title compound is readily prepared from N-diethylacrylamide in three steps.Alkylation of 1 under phase-transfer conditions yields α-cyanoenamines 4 which can be transformed into saturated or unsaturated (α,β or β,γ) esters.
- Lombaert, Stephane De,Ghosez, Leon
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p. 3475 - 3478
(2007/10/02)
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- SYNTHESE STEREOSELECTIVE D'ESTERS α,β-ETHYLENIQUES α-METHYLES Z OU E PAR LA REACTION DE WITTIG-HORNER A PARTIR DE PHOSPHONATES OU D'OXYDES DE PHOSPHINE
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The reaction of α-branched aldehydes with diethyl 1-carbomethoxyethyl phosphonate 1b in THF/nBuLi at low temperature leads stereoselectively to Z α-methyl α,β-unsaturated esters.From a linear aldehyde, the reaction is less stereoselective, while from α,β-unsaturated ones, the E isomers are predominantly formed in good yields.From diphenyl 1-carbomethoxyethyl phosphine oxide 2b, E α-methyl α,β-unsaturated esters are stereoselectively formed either in DMF/tBuOK or in phase transfer conditions, whatever the starting aldehyde is, also in good yields.This reagent can thus advantageously replace the corresponding P-ylid.In all cases, the reaction conditions are determined so that by-products formation is minimized.
- Etemad-Moghadam, Guita,Seyden-Penne, Jacqueline
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p. 5153 - 5166
(2007/10/02)
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- Polyenic acids. I. Antifungal and bacteriostatic activities of hexa-2,4 dienoic acid derivatives
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Synthesis of esters and amides of 2,4-(2 E, 4 E) hexadienoic acid are reported. The authors have tried to modulate the polarity of these compounds by introducing sequences with hydroxyl, amino groups, ether, thioether functions and halogen atoms or heterocycles. A gain in bacteriostatic activity, compared with sorbic acid has been stated in some cases, it is accompanied by either a breakdown (compounds 3, 38, 51, and 54) or a maintenance of fungistatic activity (compounds 5, 10 and 17).
- Le Baut,Sparfel,Clairc,et al.
-
p. 441 - 445
(2007/10/02)
-
- Lithium/Ammonia Reductions of 2-Thiophenecarboxylic Acids
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Lithium/ammonia reductions of 2-thiophenecarboxylic acids (1) in the absence of a proton source afforded mixtures of products.In the presence of methanol acyclic mercapto carboxylic acids (4) were the major products.Ring closure of 4 to the corresponding thiolactones (12) showed the double bonds in 4 to be of cis geometry.Attempts were made to prepare Z olefinic compounds derived from these mercapto carboxylic acids.Lithium 2-thiophenecarboxylate salts (2) afforded good yields of the corresponding 2,5-dihydro-2-thiophenecarboxylic acids (3).The presence of substituents on the ring and the ratio of metal to acid were significant factors in determining the nature of this products.A mechanism is proposed to explain the products observed.
- Blenderman, Walter G.,Joullie, Madeleine M.,Preti, George
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p. 3206 - 3213
(2007/10/02)
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- SELECTIVE REACTIONS OF THIOLATE ANIONS WITH 4-HYDROXY-E-2-ALKENOIC ESTERS OR 4-METHANESULFONYLOXY-E-2-ALKENOIC ESTERS. SYNTHESIS OF 2-ALKEN-4-OLIDES (Δα,β-BUTENOLIDES) AND E,E-2,4-ALKADIENOIC ESTERS
-
Methyl 4-hydroxy-E-2-alkenoates prepared from aldehydes in one step, undergo the Michael reactions with thiolate anions to give 4-alkanolide derivatives, which are converted into 2-alken-4-olides.Methyl 4-methanesulfonyloxy-E-2-alkenoates undergo the substitution reactions, and subsequent treatments give methyl E,E-2,4-alkadienoates.
- Tanikaga, Rikuhei,Nozaki, Yoshihito,Tanaka, Kazuhiko,Kaji, Aritsune
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p. 1703 - 1706
(2007/10/02)
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- GRAHAMIMYCIN A1: A NOVEL DILACTONE ANTIBIOTIC FROM CYTOSPORA
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By means of spectral and chemical studies the stucture of Grahamimycin A1 1, a novel macrocyclic dilactone antibiotic from Cytospora, is established.
- Ronald, Robert C.,Gurusiddaiah S.
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p. 681 - 684
(2007/10/02)
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- Catalytic coupling of allylic compounds to substituted olefins
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Allylic compounds are carbon-to-carbon coupled to substituted olefins by contacting the two compounds in the presence of a catalyst system comprising a Group VIII metal component, a bromine or iodine component, and a Group VA component. The foregoing catalytic process also promotes the intra-molecular, carbon-carbon coupling of allylic and substituted olefin groups wherein both processes provide a method for producing sorbates and related compounds.
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