- A Note on Stereochemical Observation of the Deprotonation of Ethyl-2-Alkenoates
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Deprotonation of ethyl (E)-2-alkenoates 1, 3 and 4 yields after protonation the double bond migrated (3 Z)-isomers 5, 7 and 9 as major products.In contrast, deprotonation and reprotonation of ethyl (Z)-2-pentanoate (2) gives the (3 E)-isomer 6 exclusively
- Krebs, Ernst-Peter
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- Epoxidation of Fatty Acid Esters with Aqueous Hydrogen Peroxide in the Presence of Molybdenum Oxide-Tributyltin Chloride on Charcoal Catalyst
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The epoxidation of fatty acid esters was carried out with a 30percent aqueous hydrogen peroxide in the presence of a molybdenum oxide-tributyltin chloride on a charcoal catalyst in 2-propanol at 50 degC.Such inner olefins as ethyl erucate and ethyl oleate gave good yields of 77 and 76percent, respectively.Ethyl elaidate, a trans-form of ethyl oleate, was less reactive (40percent yield).Several vegetable oils such as rapeseed oil, olive oil, soybean oil, cottonseed oil, corn oil, and linseed oil were oxidized with the oxirane oxygen contents of 5.3 to 3.5percent.
- Itoi, Yasushi,Inoue, Masami,Enomoto, Saburo
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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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- (BDP)CuH: A "hot" Stryker's reagent for use in achiral conjugate reductions
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(Chemical Equation Presented) A ligand-modified, economical version of Stryker's reagent (SR) has been developed based on a bidentate, achiral bis-phosphine. Generated in situ, "(BDP)CuH" smoothly effects conjugate reductions of a variety of unsaturated substrates, including those that are normally unreactive toward SR. Substrate-to-ligand ratios typically on the order of 1000-10000:1 can be used leading to products in high yields.
- Baker, Benjamin A.,Boskovic, Zarko V.,Lipshutz, Bruce H.
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p. 289 - 292
(2008/09/19)
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- Silica-supported dendrimer-palladium complex-catalyzed selective hydrogenation of dienes to monoolefins
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The selective hydrogenation of cyclic and acyclic dienes to monoolefins occurs under very mild conditions, in the presence of silica-supported PAMAM-Pd complexes. The activity and selectivity of this reaction is sensitive to the dendrimer structure. These dendritic complexes display excellent recycle properties, retaining activity for up to eight recycles.
- Zweni, Pumza P.,Alper, Howard
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p. 725 - 731
(2007/10/03)
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- "Syn-effect" in the conversion of (e)-α,β-unsaturated esters into the corresponding β,γ-unsaturated esters and aldehydes into silyl enol ethers
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The stereochemistry in the conversion of (E)-α,β-unsaturated esters into the corresponding β,γ-unsaturated esters, and that in the conversion of aldehydes into the silyl enol ethers, were investigated. The Z/E ratios of the resulting β,γ-unsaturated ester
- Guha, Samar Kumar,Shibayama, Atsushi,Abe, Daisuke,Sakaguchi, Maki,Ukaji, Yutaka,Inomata, Katsuhiko
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p. 2147 - 2157
(2007/10/03)
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- A Stereospecific Access to Allylic Systems Using Rhodium(II)-Vinyl Carbenoid Insertion into Si-H, O-H, and N-H Bonds
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Rhodium-catalyzed decomposition of α-vinyldiazoesters in the presence of silanes, alcohols, ethers, amines, and thiols have been shown to produce the corresponding α-silyl, α-hydroxy, α-alkoxy, α-amino, and α-thioalkoxy esters in generally good yield with a complete retention of the stereochemistry of the double bond of the diazo precursor. An extension of the process in homochiral series has also been devised using either a chiral auxiliary attached to the ester function or achiral α-vinyldiazoesters and Doyle's chiral catalyst Rh2(MEPY)4. In the former approach, pantolactone as chiral auxiliary gave diastereoselectivities of up to 70%, while the second approach produced the desired allylsilane with ee as high as 72%. On the other hand, Rh2(MEPY)4-catalyzed insertion into the O-H bond of water led to poor or no enantioselectivity in good agreement with recent literature reports.
- Bulugahapitiya, Priyadarshanie,Landais, Yannick,Parra-Rapado, Liliana,Planchenault, Denis,Weber, Valery
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p. 1630 - 1641
(2007/10/03)
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