- Unexpected formation of a trans-syn-fused linear triquinane from a trimethylenemethane (TMM)-diyl-mediated [2+3] cycloaddition reaction
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trans-Fused triquinane: Intramolecular-trimethylenemethane-mediated [2+3] cycloaddition reaction of a highly congested substrate proceeded stepwise to produce highly strained triquinane structures along with tricyclo[5.3.1.0 2, 6]undecanes.
- Kim, Won-Yeob,Kim, Byung Gyu,Kang, Taek,Lee, Hee-Yoon
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Read Online
- SOLVENT-CONTROLLED ADDITIONS OF ORGANOTITANIUM REAGENTS TO OLEFINIC DOUBLE BONDS
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Under carefully chosen working conditions (solvent, temperature), methyltitanium reagents smoothly convert homoallyl alcohols having a terminal double-bond into (E)-3-penten-1-ols whereas non-terminal 3-alken-1-ols afford 4-methyl-branched derivatives with configurational inversion of the chain (Z -> E; E -> Z), stereoselectivities being better than 99percent.
- Moret, Etienne,Schlosser, Manfred
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Read Online
- Alkyne Aminopalladation/Heck and Suzuki Cascades: An Approach to Tetrasubstituted Enamines
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Alkyne aminopalladation reactions starting from tosylamides are reported. The emerging vinylic Pd species are converted either in an intramolecular Heck reaction with olefinic units or in an intermolecular Suzuki reaction by using boronic acids exhibiting broad functional group tolerance. Tetra(hetero)substituted tosylated enamines are obtained in a simple one-pot process.
- Geffers, Finn J.,Jones, Peter G.,Kurth, Florens R.,Werz, Daniel B.
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supporting information
p. 14846 - 14850
(2021/10/19)
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- Highly Regioselective 5-endo-tet Cyclization of 3,4-Epoxy Amines into 3-Hydroxypyrrolidines Catalyzed by La(OTf)3
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Highly regioselective intramolecular aminolysis of 3,4-epoxy amines has been achieved. Key features of this reaction are (1) chemoselective activation of epoxides in the presence of unprotected aliphatic amines in the same molecules by a La(OTf)3 catalyst and (2) excellent regioselectivity for anti-Baldwin 5-endo-tet cyclization. This reaction affords 3-hydroxy-2-alkylpyrrolidines stereospecifically in high yields. DFT calculations revealed that the regioselectivity might be attributed to distortion energies of epoxy amine substrates. The use of this reaction was demonstrated by the first enantioselective synthesis of an antispasmodic agent prifinium bromide.
- Hoshino, Yoshihiko,Iwabuchi, Yoshiharu,Kuriyama, Yuse,Sasano, Yusuke,Uesugi, Shun-ichiro,Yamaichi, Aoto
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supporting information
p. 1961 - 1965
(2021/01/04)
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- Method for synthesizing (9Z, 12E)-9,12-tetradecadien-1-ol acetate
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The invention belongs to the technical field of green pesticide synthesis, and discloses a novel method for synthesizing (9Z, 12E)-9,12-tetradecadien-1-ol acetate. According to the method, malonic acid and 9-bromo-1-nonyl alcohol are used as two starting raw materials. The method comprises the following steps: carrying out a Knoevenagel condensation reaction on malonic acid and propionaldehyde inthe presence of piperidine acetate to generate (E)-3-pentenoic acid, then carrying out lithium aluminum hydride reduction to obtain (E)-3-penten-1-ol, carrying out bromination reaction, and refluxingwith triphenylphosphine in acetonitrile to obtain (E)-3-pentenyltriphenylphosphine bromide; carrying out a PCC oxidation reaction on 9-bromo-1-nonanol to obtain 9-bromononanal, and then reacting the 9-bromononanal with potassium acetate to obtain 9-acetoxynonanal; and finally, carrying out a Wittig reaction on (E)-3-pentenyltriphenylphosphine bromide and 9-acetoxynonanal so as to obtain (9Z, 12E)-9,12-tetradecadien-1-ol acetate. An E-type double bond is constructed by utilizing the Knoevenagel condensation reaction of malonic acid and propionaldehyde, and the method has the advantages of mildreaction conditions, environmental friendliness, simple synthetic route and the like.
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Paragraph 0011; 0029-0031
(2020/06/16)
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- Dynamic ?-Bonding of Imidazolyl Substituent in a Formally 16-Electron Cp Ru(2-P, N)+ Catalyst Allows Dramatic Rate Increases in (E)-Selective Monoisomerization of Alkenes
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Alkene isomerization can be an atom-economical approach to generating a wide range of alkene intermediates for synthesis, but fully equilibrated mixtures of disubstituted internal alkenes typically contain significant amounts of the positional as well as geometric (E and Z) isomers. Most classical catalyst systems for alkene isomerization struggle to kinetically control either positional or E/Z isomerism. We report coordinatively unsaturated, formally 16-electron Cp Ru catalyst 5, which facilitates simultaneous regio- A nd stereoselective isomerization of linear 1-alkenes to their internal analogues, providing consistent yields of (E)-2-alkenes greater than 95%. Because nitrile-free catalyst 5 is more than 400 times faster than previously published nitrile-containing analogues 2 + 2a, very reasonable 0.1-0.5 mol % loadings of 5 complete ambient-temperature reactions within 15 min to 4 h. UV-vis, NMR, and computational studies depict the imidazolyl fragment on the phosphine as a hemilabile, four-electron donor in 2-P,N coordination. For the first time, we show direct experimental evidence that the PN ligand has accepted a proton from the substrate by characterizing the intermediate Cp Ru[??3-allyl][1-P)P-N+H], which highlights the essential role of the bifunctional ligand in promoting rapid and selective alkene isomerizations. Moreover, kinetic studies and computations reveal the role of alkene binding in selectivity of unsaturated catalyst 5.
- Paulson, Erik R.,Moore, Curtis E.,Rheingold, Arnold L.,Pullman, David P.,Sindewald, Ryan W.,Cooksy, Andrew L.,Grotjahn, Douglas B.
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p. 7217 - 7231
(2019/08/27)
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- Catalyst versus Substrate Control of Forming (E)-2-Alkenes from 1-Alkenes Using Bifunctional Ruthenium Catalysts
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Here we examine in detail two catalysts for their ability to selectively convert 1-alkenes to (E)-2-alkenes while limiting overisomerization to 3- or 4-alkenes. Catalysts 1 and 3 are composed of the cations CpRu(κ2-PN)(CH3CN)+ and Cp?Ru(κ2-PN)+, respectively (where PN is a bifunctional phosphine ligand), and the anion PF6-. Kinetic modeling of the reactions of six substrates with 1 and 3 generated first- and second-order rate constants k1 and k2 (and k3 when applicable) that represent the rates of reaction for conversion of 1-alkene to (E)-2-alkene (k1), (E)-2-alkene to (E)-3-alkene (k2), and so on. The k1:k2 ratios were calculated to produce a measure of selectivity for each catalyst toward monoisomerization with each substrate. The k1:k2 values for 1 with the six substrates range from 32 to 132. The k1:k2 values for 3 are significantly more substrate-dependent, ranging from 192 to 62 000 for all of the substrates except 5-hexen-2-one, for which the k1:k2 value was only 4.7. Comparison of the ratios for 1 and 3 for each substrate shows a 6-12-fold greater selectivity using 3 on the three linear substrates as well as a >230-fold increase for 5-methylhex-1-ene and a 44-fold increase for a silyl-protected 4-penten-1-ol substrate, which are branched three and five atoms away from the alkene, respectively. The substrate 5-hexen-2-one is unique in that 1 was more selective than 3; NMR analysis suggested that chelation of the carbonyl oxygen can facilitate overisomerization. This work highlights the need for catalyst developers to report results for catalyzed reactions at different time points and shows that one needs to consider not only the catalyst rate but also the duration over which a desired product (here the (E)-2-alkene) remains intact, where 3 is generally superior to 1 for the title reaction.
- Paulson, Erik R.,Delgado, Esteban,Cooksy, Andrew L.,Grotjahn, Douglas B.
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supporting information
p. 1672 - 1682
(2019/01/04)
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- Regioselective Epoxidations by Cytochrome P450 3A4 Using a Theobromine Chemical Auxiliary to Predictably Produce N-Protected β- or γ-Amino Epoxides
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N-Protected β- and γ-amino epoxides are useful chiral synthons. We report here that the enzyme cytochrome P450 3A4 can catalyze the formation of such compounds in a regio- and stereoselective manner, even in the presence of multiple double bonds or aromatic substituents. To this end, the theobromine chemical auxiliary is used not only to control the selectivity of the enzyme, but also as a masked amine, and to facilitate product recovery. Theobromine predictably directed epoxidation at the double bond of the fourth carbon from the theobromine group. Unlike with most catalysts, the selectivity did not depend on electronic or steric factors but rather on the position of the olefin relative to the theobromine group. (Figure presented.).
- Polic, Vanja,Cheong, Kin Jack,Hammerer, Fabien,Auclair, Karine
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supporting information
p. 3983 - 3989
(2017/11/30)
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- Terminal alkene monoisomerization catalysts and methods
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The invention provides novel catalysts and methods of using catalysts for controlling the position of a double bond and cis/trans-selectivity in isomerization of terminal alkenes to their 2-isomers. Catalysts such as (pentamethylcyclopentadienyl)Ru formulas 1 and 3 having a bifunctional phosphine can be used in the methods. A catalyst loading of 1 mol % of formulas 1+3 can be employed for the production of (E)-2-alkenes at 40-70° C.; lower temperatures can be used with higher catalyst loading. Acetonitrile-free catalysts can be used at lower loadings, room temperature, and in less than a day to accomplish the same results as catalysts 1+3. The novel catalyst systems minimize thermodynamic equilibration of alkene isomers, so that the trans-2-alkenes of both non-functionalized and functionalized alkenes can be generated.
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Page/Page column 52; 53
(2017/08/07)
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- A 2-methyl-3-tetrahydrofuran thiol acetate method for preparing trans isomer
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The invention relates to a simple preparation method for a 2-methyl-3-tetrahydrofuranthiol acetate cis-trans-isomer which has the structural formula as shown in the specification. The simple preparation method comprises the following steps: propionaldehyde and propandioic acid are subjected to condensation through Knoevenagel to obtain (E)-3-pentenoic acid, the (E)-3-pentenoic acid is reduced through lithium aluminum hydride to obtain (E)-3-pentene-1-alcohol, and then the (E)-3-pentene-1- alcohol reacts with methylsulfonyl chloride to obtain (E)-3-pentene-1-alcohol methanesulfonate, wherein the three-step overall reaction yield is 24%; (E)-3-pentene-1-alcohol methanesulfonate is oxidized with hydrogen peroxide and methanoic acid, and are cyclizated under the alkaline condition to obtain trans-2- methyl-3-hydroxytetrahydrofuran, and hydroxyl is transformed into methanesulfonate which reacts with thioacetic acid to obtain cis-2-methyl-3-tetrahydrofuranthiol acetate, wherein the three-step overall reaction yield is 61%; (E)-3-pentene-1-alcohol methanesulfonate is oxidized with potassium permanganate to obtain cis-2-methyl-3-hydroxytetrahydrofuran, and hydroxyl is transformed into methanesulfonate which reacts with thioacetic acid to obtain trans-2-methyl-3-tetrahydrofuranthiol acetate, wherein the three-step overall reaction yield is 63%.
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Paragraph 0012; 0013
(2016/12/01)
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- ARYLOXYACETYLINDOLES AND ANALOGS AS ANTIBIOTIC TOLERANCE INHIBITORS
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The disclosure provides compounds and pharmaceutical compositions of aryloxyacetylindoles compounds and analogs useful for treating chronic and acute bacterial infections. Certain of the compounds are compounds of general Formula (I) (I) or a pharmaceutically acceptable salt or prodrug thereof. Certain compounds of this disclosure are MvfR inhibitors. MvfR inhibitors reduce the formation of antibiotic tolerant bacterial strains and are useful for treating Gram-negative bacterial infections and reducing the virulence of Pseudomonas aeruginosa. Methods of treating bacterial infections in a subject, including Pseudomonas aeruginosa infections, are also provided by the disclosure.
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Paragraph 0740
(2016/08/10)
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- Enantioselective syntheses and sensory properties of 2-methyl-tetrahydrofuran-3-thiol acetates
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The enantioselective synthesis of four stereoisomers of 2-methyl-tetrahydrofuran-3-thiol acetate was achieved. The two enantiomers of the important intermediate cis-2-methyl-3-hydroxy-tetrahydrofuran were obtained by Sharpless asymmetric dihydroxylation (AD), whereas the two enantiomers of trans-2-methyl-3-hydroxy-tetrahydrofuran were derived from the corresponding optically active cis-isomers by Mitsunobu reaction. Each stereoisomer of 2-methyl-3-hydroxy-tetrahydrofuran went through mesylation and nucleophilic substitution to afford the corresponding product with specific configuration. (2R,3S)- and (2R,3R)-2-methyl-tetrahydrofuran-3-thiol acetate were obtained in 80% ee, whereas the (2S,3R)- and (2S,3S)-isomers were in 62% ee. The odor properties of the synthesized four stereoisomers were evaluated by gas chromatography - olfactometry (GC-O), which revealed perceptible di fferences among stereoisomers both in odor features and in intensities.
- Dai, Yifeng,Shao, Junqiang,Yang, Shaoxiang,Sun, Baoguo,Liu, Yongguo,Ning, Ting,Tian, Hongyu
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p. 464 - 468
(2015/01/30)
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- Copper-Catalyzed Oxy-Alkenylation of Homoallylic Alcohols to Generate Functional syn-1,3-Diol Derivatives
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A novel method for the synthesis of a wide range of functionalized 1,3-diol derivatives is reported. Employing a copper-catalyzed oxy-alkenylation strategy, a range of readily available, substituted homoallylic alcohol derivatives and alkenyl(aryl) iodonium salts combine to form syn-1,3-carbonates in excellent yield and with high selectivity. Furthermore, the products formed are amenable to an iterative reaction sequence, thus affording highly complex polyketide-like fragments. Polyols: The reported copper-catalyzed oxy-alkenylation strategy works well for a range of readily available, substituted homoallylic alcohol derivatives and alkenyl(aryl) iodonium salts to form syn-1,3-carbonates in excellent yield and high selectivity. Furthermore, the products formed are amenable to an iterative reaction sequence, thus affording highly complex polyketide-like fragments.
- Holt, Dean,Gaunt, Matthew J.
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supporting information
p. 7857 - 7861
(2015/06/30)
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- Palladium-Catalyzed Enantioselective Heck Alkenylation of Acyclic Alkenols Using a Redox-Relay Strategy
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We report a highly enantioselective intermolecular Heck reaction of alkenyl triflates and acyclic primary or racemic secondary alkenols. The mild reaction conditions permit installation of a wide range of alkenyl groups at positions β, γ, or δ to a carbonyl group in high enantioselectivity. The success of this reaction is attributed to the use of electron-withdrawing alkenyl triflates, which offer selective β-hydride elimination followed by migration of the catalyst through the alkyl chain to give the alkenylated carbonyl products. The synthetic utility of the process is demonstrated by a two-step modification of a reaction product to yield a tricyclic core structure, present in various natural products.
- Patel, Harshkumar H.,Sigman, Matthew S.
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supporting information
p. 3462 - 3465
(2015/03/30)
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- Influence of the chemical structure on odor qualities and odor thresholds in homologous series of alka-1,5-dien-3-ones, alk-1-en-3-ones, alka-1,5-dien-3-ols, and alk-1-en-3-ols
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Odor qualities and odor thresholds in air in homologous series of synthesized alk-1-en-3-ols and alka-1,5-dien-3-ols and their corresponding ketones were evaluated by gas chromatography-olfactometry. In the series of the alk-1-en-3-ols and alk-1-en-3-ones the odor quality changed successively from pungent for the compounds with five carbon atoms via metallic, vegetable-like for the six- and seven-carbon odorants to mushroom-like for the compounds with eight and nine carbon atoms. With further increase in chain length the mushroom-like impression decreased and changed to citrus-like, soapy, or herb-like. In both series, two odor threshold minima were found for the six-carbon and also for the eight- and nine-carbon odorants, respectively. In contrast to this, the odor qualities in the series of the (Z)- and (E)-alka-1,5-dien-3-ols and their corresponding ketones did not change significantly with geranium-like, metallic odors and an increasing mushroom-like odor note with increasing chain length. The lowest thresholds were found for the eight- and nine-carbon (Z)-compounds, respectively.
- Lorber, Katja,Schieberle, Peter,Buettner, Andrea
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p. 1025 - 1031
(2014/03/21)
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- Influence of the chemical structure on odor qualities and odor thresholds in homologous series of alka-1,5-dien-3-ones, alk-1-en-3-ones, alka-1,5-dien-3-ols, and alk-1-en-3-ols
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Odor qualities and odor thresholds in air in homologous series of synthesized alk-1-en-3-ols and alka-1,5-dien-3-ols and their corresponding ketones were evaluated by gas chromatography-olfactometry. In the series of the alk-1-en-3-ols and alk-1-en-3-ones the odor quality changed successively from pungent for the compounds with five carbon atoms via metallic, vegetable-like for the six- and seven-carbon odorants to mushroom-like for the compounds with eight and nine carbon atoms. With further increase in chain length the mushroom-like impression decreased and changed to citrus-like, soapy, or herb-like. In both series, two odor threshold minima were found for the six-carbon and also for the eight- and nine-carbon odorants, respectively. In contrast to this, the odor qualities in the series of the (Z)- and (E)-alka-1,5-dien-3-ols and their corresponding ketones did not change significantly with geranium-like, metallic odors and an increasing mushroom-like odor note with increasing chain length. The lowest thresholds were found for the eight- and nine-carbon (Z)-compounds, respectively.
- Lorber, Katja,Schieberle, Peter,Buettner, Andrea
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p. 1025 - 1031
(2015/04/22)
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- Isothiourea-mediated asymmetric functionalization of 3-alkenoic acids
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Isothiourea HBTM-2.1 promotes the catalytic asymmetric α- functionalization of 3-alkenoic acids through formal [2 + 2] cycloadditions with N-tosyl aldimines and formal [4 + 2] cycloadditions with either 4-aryltrifluoromethyl enones or N-aryl-N-aroyl diazenes, providing useful synthetic building blocks in good yield and with excellent enantiocontrol (up to >99% ee). Stereodefined products are amenable to further synthetic elaboration through manipulation of the olefinic functionality.
- Morrill, Louis C.,Smith, Samuel M.,Slawin, Alexandra M. Z.,Smith, Andrew D.
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p. 1640 - 1655
(2014/03/21)
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- Preparation and odour of cis- and trans-2-methyltetrahydrofuran-3-thiol acetates
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The preparation of cis- and trans-2-methyltetrahydrofuran-3-thiol acetates from (E)-3-penten-1-ol is reported. The mesylate of (E)-3-penten-1-ol was converted into trans- or cis-2-methyl-3-hydroxytetrahydrofuran by oxidation with H2O2 and HCOOH or with KMnO4. cis- or trans-2-Methyltetrahydrofuran-3-thiol acetate was prepared by mesylation and an SN2 nucleophilic substitution with AcSH from trans- or cis-2-methyl-3-hydroxytetrahydrofuran respectively. The configuration of the products was confirmed by their synthesis. Olfactory evaluation of cis- and trans-2-methyltetrahydrofuran-3-thiol acetates indicated some differences both in odour feature and intensity.
- Dai, Yifeng,Sun, Baoguo,Yang, Shaoxiang,Liu, Yongguo,Tian, Hongyu,Shao, Junqiang
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p. 236 - 239
(2014/05/06)
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- General catalyst control of the monoisomerization of 1-alkenes to trans -2-alkenes
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After searching for the proper catalyst, the dual challenges of controlling the position of the double bond, and cis/trans-selectivity in isomerization of terminal alkenes to their 2-isomers are finally met in a general sense by mixtures of (C5Me5)Ru complexes 1 and 3 featuring a bifunctional phosphine. Typically, catalyst loadings of 1 mol % of 1 and 3 can be employed for the production of (E)-2-alkenes at 40-70 C. Catalyst comprising 1 and 3 avoids more than any other known example the thermodynamic equilibration of alkene isomers, as the trans-2-alkenes of both nonfunctionalized and functionalized alkenes are generated.
- Larsen, Casey R.,Erdogan, Gulin,Grotjahn, Douglas B.
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supporting information
p. 1226 - 1229
(2014/02/14)
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- A dioxane template for highly selective epoxy alcohol cyclizations
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Ladder polyether natural products are a class of natural products denoted by their high functional-group density and large number of well-defined stereocenters. They comprise the toxic component of harmful algal blooms (HABs), having significant negative economic and environmental ramifications. However, their mode of action, namely blocking various cellular ion channels, also denotes their promise as potential anticancer agents. Understanding their potential mode of biosynthesis will not only help with developing ways to limit the damage of HABs, but would also facilitate the synthesis of a range of analogs with interesting biological activity. 1,3-Dioxan-5-ol substrates display remarkable 'enhanced template effects' in water-promoted epoxide cyclization processes en route to the synthesis of these ladder polyether natural products. In many cases, they provide near complete endo-to-exo selectivity in the cyclization of epoxy alcohols, thereby strongly favoring the formation of tetrahydropyran (THP) over tetrahydrofuran (THF) rings. The effects of various Br?nsted and Lewis acidic and basic conditions are explored to demonstrate the superior selectivity of the template over the previously reported THP-based epoxy alcohols. In addition, the consideration of other synthetic routes are also considered with the goal of gaining rapid access to a plethora of potential starting materials applicable towards the synthesis of ladder polyethers. Finally, cascade sequences with polyepoxides are investigated, further demonstrating the versatility of this new reaction template. Reversed selectivity: 1,3-Dioxan-5-ol templated epoxy alcohols undergo a remarkably selective cyclization, which occurs with near complete endo selectivity that is opposite to that predicted by Baldwin's rules. This endo preference in water near pH 7.0 is an order of magnitude larger relative to that of a previously disclosed THP-templated cyclization (see scheme), suggesting that "templates" may be important in the biosynthesis of marine ladder polyethers. Copyright
- Mousseau, James J.,Morten, Christopher J.,Jamison, Timothy F.
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p. 10004 - 10016
(2013/08/23)
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- An asymmetric total synthesis of (+)-pentalenene
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A stereoselective total synthesis of (+)-pentalenene was achieved through the tandem cycloaddition reaction of the allenyl diazo substrate prepared from (+)-citronellal. The initial intramolecular [2+3] cycloaddition reaction between the diazo functionality and the allenyl group produced the trimethylenemethane (TMM) intermediate after immediate loss of nitrogen molecule from the cycloaddition intermediate. Subsequent [2+3] cycloaddition of the TMM with olefin produced the angularly fused triquinane structure stereoselectively.
- Kim, Yoon-Jung,Yoon, Yeokwon,Lee, Hee-Yoon
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p. 7810 - 7816
(2013/08/23)
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- Influence of a methyl substituent on the Raman spectrum of but-3-enyl methyl ether
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The Raman spectrum of but-3-enyl methyl ether, CH2=CHCH 2CH2OCH3 is reported and compared with those of its homologues in which a methyl group is substituted for a hydrogen atom on one of the carbon atoms of the alkenyl chain. Attention is focused on the influence of this methyl group on the bands in the spectrum associated with specific C-H, skeletal stretching and bending vibrations. The use of ab initio DFT quantum mechanical calculations to assist in making these assignments reveals a high degree of mode-mixing in the skeletal vibrations. The value of model studies of this kind in refining the correlations between the presence and absence of specific bands in a Raman spectrum with molecular structure is emphasised.
- Bowen, Richard D.,Edwards, Howell G.M.,Varnali, Tereza
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- Enantiodivergent and γ-selective asymmetric allylic amination
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Double agent: The title reaction using the guanidine catalyst 1 can deliver both enantiomers of the product with excellent enantioselectivity by judicious choice of the double bond geometry of the the β,γ-unsaturated carbonyl compound. Computational studies reveal the possible origin of the inversed enantioselectivity, and the potential for enantiodivergent synthesis chiral amine-containing substrates is attractive. Copyright
- Wang, Jianmin,Chen, Jie,Kee, Choon Wee,Tan, Choon-Hong
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supporting information; experimental part
p. 2382 - 2386
(2012/05/19)
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- A stereoselective total synthesis of 7,8-O-isopropylidene iriomoteolide-3a
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A stereoselective total synthesis of 7,8-O-isopropylidene iriomoteolide-3a has been achieved by using Yamaguchi esterification, Julia-Kocienski olefination, organocatalytic α-oxidation, and ring-closing metathesis reaction as key bond-forming steps.
- Zhang, Yao,Deng, Lisheng,Zhao, Gang
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scheme or table
p. 4518 - 4526
(2011/07/29)
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- A detailed investigation of the aza-prins reaction
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The development of a Lewis acid-promoted aza-Prins reaction to form piperidines and pyrrolidines is described. Indium trichloride has been found to be a highly successful and mild Lewis acid for promoting this reaction. A thorough mechanistic investigation is described, including the factors that influence the formation of the 5- or 6-membered ring product(s). The Royal Society of Chemistry.
- Dobbs, Adrian P.,Guesne, Sebastien J. J.,Parker, Robert J.,Skidmore, John,Stephenson, Richard A.,Hursthouse, Mike B.
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scheme or table
p. 1064 - 1080
(2010/06/13)
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- A supramolecular catalyst for regioselective hydroformylation of unsaturated carboxylic acids
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(Chemical Equation Presented) The quest to capture the catalytic power of enzymes is one of the great challenges of modern chemistry. A novel system inspired by the principles of enzymatic catalysis combines recognition of the substrate and transition-metal catalysis (see scheme; Do = donor, FG = functional group) and mimics enzyme properties - high efficiency, substrate selectivity, and reaction-site selectivity.
- Smejkal, Tomas,Breit, Bernhard
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p. 311 - 315
(2008/09/19)
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- Facile synthesis of mill moth's sex pheromone components
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An improved method for the preparation of mill moth's sex pheromone components in high diastereomeric purity is described. Copyright Taylor & Francis Group, LLC.
- Hornyanszky, Gabor,Rohaly, Janos,Novak, Lajos
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p. 1533 - 1540
(2008/09/20)
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- Hydration of propargylic alcohols by ruthenium catalysts, with dominant anti-Markovnikov regioselectivity, formation of α,β-unsaturated products and catalytic decarbonylation to 1-alkenes
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Ruthenium catalysts - water-soluble ruthenium sulfophthalocyanine and heterogeneous ruthenium hydroxyapatite complexes - proved to be effective for the hydration of propargylic alcohols in entirely aqueous media. 1-Phenyl-2-propyn-1-ol underwent an unprecedented catalytic hydration- decarbonylation-dehydration reaction, giving rise to styrene and carbon monoxide; 2-propyn-1-ol and 3-butyn-2-ol gave predominantly the products of anti-Markovnikov addition, together with products of hydration-dehydration (α,β-rearrangement) and, to a minor extent, the decarbonylation products, ethene or propene, respectively. Hydrations were also conducted in D2O, giving indications of the mechanism of the reactions and apparently ruling out the allenylidene route for the α,β- rearrangement. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- D'Alessandro, Nicola,Di Deo, Milena,Bonetti, Monica,Tonucci, Lucia,Morvillo, Antonino,Bressan, Mario
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p. 810 - 817
(2007/10/03)
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- A mechanistic alternative for the intramolecular hydroboration of homoallylic amine and phosphine borane complexes
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Intramolecular hydroboration is demonstrated starting from homoallylic amine boranes upon activation by iodine. The process involves a B-iodoborane complex as the intermediate and may occur via internal displacement of iodide by the alkene to generate a cationic borane-alkene π-complex on the way to hydroboration products. The reaction can be carried out using a catalytic amount of iodine. Copyright
- Scheideman, Matthew,Shapland, Peter,Vedejs, Edwin
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p. 10502 - 10503
(2007/10/03)
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- Synthesis of the C(17)-C(27) fragment of the 20-deoxybryostatins
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A synthesis of the C(17)-C(27) fragment of the 20-deoxybryostatins is described in which the key step is a palladium(0) catalysed coupling of a tributyltin enolate with a vinylic bromide. (C) 2000 Elsevier Science Ltd.
- Almendros,Rae,Thomas
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p. 9565 - 9568
(2007/10/03)
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- Analytical Applications of Raman Spectroscopy in Organic Chemistry: Influence of the Position, Stereochemistry and Substitution Pattern of the Double Bond on the ν(C=C) and ν(sp2CH) Stretching Bands in the Raman Spectra of Alkenyl Methyl Ethers
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The Raman spectra of 29 alkenyl methyl ethers, CnH(2n-1)OCH3, of diverse structure containing up to seven carbon atoms are reported and discussed. All these spectra contain a strong band in the region 1640-1680 cm-1 associated with the stretching vibration of the C=C double bond. Reliable correlations are found between the wavenumber of this band and the position, stereochemistry and substitution pattern of the double bond the band is at higher wavenumber for ethers containing a di- or tri-substituted bond than for those with a monosubstituted bond and at higher wavenumber for trans than cis-stereoisomers. One or more bands in the range 2995-3080 cm-1 associated with the stretching vibration(s) of the sp2C-H bond(s) are also evident in the spectra of most of the ethers, but these bands are sometimes obscured by the stronger bands corresponding to stretching vibrations of the sp3C-H bonds at slightly lower wavenumber (generally below ca. 2950 cm-1). Correlations involving the number and position(s) of these band provide confirmatory evidence on the substitution pattern and stereochemistry of the C=C group. Unequivocal assignment of the symmetric and asymmetric C-H stretching vibrations of the important terminal C=CH2 entity is possible on the basis of these studies; these conclusions are supported by analysis of the Raman spectrum of the deuterium labelled ether CD2=CH(CH2)3OCH3.
- Bowen, Richard D.,Edwards, Howell G. M.,Farwell, Dennis W.,Rusike, Irene,Saunders, Darren M.
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p. 1901 - 1918
(2007/10/03)
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- Syntheses with organoboranes. VII, monohydroboration of conjugated dienes with catecholborane catalyzed by complexes of Nickel(II) chloride and Cobalt(II) chloride with diphosphines
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The monohydroboration of representative conjugated dienes 1-7 with catecholborane in the presence of SmI3, t-BuOSmI2, LaI3, Ti(OPr(i))4, iron(II), nickel(II) and cobalt(II) chloride complexes with dppe, dppp and dppb was examined. NiCl2(dppe), NiCl2(dppp) and CoCl2(dppp) shoned catalytic activity. The 1,2-addition products were obtained, no 1,4-addition was observed. The reactivity in the presence of NiCl2(dppe) decreased in the order acyclic dienes > cyclic dienes >>1-decene.
- Zaidlewicz, Marek,Meller, Jerzy
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p. 7279 - 7282
(2007/10/03)
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- Method for inhibition of HIV related viruses
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Treatment of AIDS, inhibition of the replication of HIV and related viruses thereof, and formulations using thiourea derivative compounds or salts thereof is disclosed. Also disclosed are novel thiourea derivative compounds.
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- Stereochemical aspects of intramolecular palladium catalysed [3+2] cycloadditions of methylenecyclopropanes
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The preparation and intramolecular palladium catalysed [3+2] cycloaddition reactions of a range of substrates containing either stereochemically defined 2,3-disubstituted methylenecyclopropanes 3 or acrylate acceptors 12-15 are described. Evidence is presented which supports the hypothesis that these cycloaddition reactions proceed via palladium-trimethylenemethane type intermediates and that the two carbon-carbon bonds are formed in a highly asynchronous manner.
- Corlay, Herve,Motherwell, William B.,Pennell, Andrew M. K.,Shipman, Michael,Slawin, Alexandra M. Z.,Williams, David J.,Binger, Paul,Stepp, Michael
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p. 4883 - 4902
(2007/10/03)
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- Effect of the Structure of Unsaturated Aliphatic Alcohols on the Hydrogenation Rate over Pd-Ru Membrane Catalyst
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It is shown that the rate of hydrogenation of substituted propargyl and allyl alcohols, as measured in the liquid phase on a membrane Pd-Ru alloy catalyst is described by the two-parameter Taft equation, which accounts for the induction and steric substituent effects.A positive induction effect of the substituent group promotes the reaction, whereas a negative one slows it down; an enhancement in the steric factor decreases the rate of conversion.Both induction and steric effects are stronger in reactions with ethylenic rather than acetylenic alcohols and for trans rather than cis isomers.
- Karavanov, A. N.,Gryaznov, V. M.,Batyrev, I. G.,Olenina, E. G.
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p. 739 - 743
(2007/10/02)
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- Stereoselective Synthesis of Alcohols containing (Z)- and (E)-Olefins, Dienes, Enynes and Styrenes: Cyclic β-Halogeno Scissions using Samarium Diiodide as the Electron-transfer Agent
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In contrast to the sodium-mediated ring scission of 2-substituted 3-chloro ethers of the tetrahydrofuran series, samarium diiodide gives olefins of high (E)-stereoselectivity and provides (E)-conjugated and unconjugated dienes, styrenes and enynes in good yield without appreciable over-reduction.Whilst the SmI2 scission of 3-chloro-2-alkyltetrahydropyrans gives (Z)-rich (Z)/(E) olefin mixtures, the 2-(alk-1'-ynyl) members give (Z)-enyne alkohols with high stereoselectivity, providing a valuable complement to the (E)-enyne synthesis employing the tetrahydrofuran series.In electron-transfer scissions using sodium, the stereochemistry of the product alcohols is related to the ground-state conformation of the cis- and trans-pyrans and -furans.The slow SmI2-mediated reactions appear to involve samarium-complexed intermediates having structures independent of the original conformation, or of the cis- or trans-geometry of the furan or pyran, and it is the transition states from these intermediates that determine the stereochemical outcome.Scissions in the tetrahydrofuran series can be accelerated by addition of HMPA or DMPU with only a little deterioration in stereoselectivity, but in the tetrahydropyran series there are drastic changes in product stereochemistry when DMPU is added.Brief comment is made on the synthesis of tetrahydro-furan and pyran precursors.
- Crombie, Leslie,Rainbow, Linda J.
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p. 673 - 688
(2007/10/02)
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- N-(9-Phenylfluoren-9-yl)-α-amino Ketones and N-(9-Phenylfluoren-9-yl)-α-amino Aldehydes as Chiral Educts for the Synthesis of Optically Pure 4-Alkyl-3-hydroxy-2-amino Acids. Synthesis of the C-9 Amino Acid MeBmt Present in Cyclosporin
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Serine derived N-(9-phenylfluoren-9-yl)-α-amino ketones were prepared by acylation of primary organometallic reagents with amino acid isoxazolidides.When the amino and hydroxyl functions of serine were constrained in oxazolidine and oxazolidinone rings, alkylation of these ketones as their lithium enolates proceeded regiospecifically with good to excellent diasteroselectivity.Reduction of the oxazolidine and oxazolidinone ketones diastereoselectively led to N-protected 4-alkyl-branched 2-amino 1,3-diols that were subsequently oxidized in two steps, via the N-(9-phenylfluoren-9-yl)-α-amino aldehyde, to produce 4-alkyl-β-hydroxy-α-amino acids.In this way L-(+)-MeBmt (1), the C-9 amino acid of cyclosporin, and its D-(-) enantiomer were prepared in 12 steps from D- and L-serine, respectively, with 22percent overall yield and >99percent enantiomeric purity.N-(9-Phenylfluoren-9-yl)-MeBmt triple-bond and 6Z double-bond analogues 37 and 39 were also prepared.This synthetic route requires only a single chiral source (serine) and provides for configurational choice at all four diastereomeric centres.
- Lubell, William D.,Jamison, Timothy F.,Rapoport, Henry
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p. 3511 - 3522
(2007/10/02)
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- The Thermal Decomposition of Diazirines: 3-(3-Methyldiazirin-3-yl)propan-1-ol and 3-(3-Methyldiazirin-3-yl)propanoic Acid
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The thermolyses of 3-(3-methyldiazirin-3-yl)propan-1-ol (1) and 3-(3-methyldiazirin-3-yl)propanoic acid (2) have been studied in solution over the temperature range 96-125 deg C.The reactions are unimolecular and fit linear Arrhenius plots with k(1)=1013.85+/-0.69exp-1/RT>s-1 and k(2)=1012.38+/-0.43exp-1/RT>s-1.The major products are the alkenes derived from the corresponding carbenes MeC2.CH2CH2CH2OH (3) and MeC2.CH2CH2CO2H (4).The new rate data, taken together with previous work, tend to confirm that diazirine thermolysis involves ring opening to a "complex" followed either by nitrogen loss or by isomerization to a diazo compound.Whereas (1) gives no product of closure onto oxygen, the acid (2) affords about 5percent γ-valerolactone.
- Stevens, Ian D. R.,Liu, Michael T. H.,Soundararajan, N.,Paike, N.
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p. 661 - 667
(2007/10/02)
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- Indole Diterpene Synthetic Studies. 2. First-Generation Total Synthesis of (-)-Paspaline
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We record here a full account of the first total synthesis of (-)-paspaline (1), the simplest member of a rapidly growing class of architecturally complex diterpene indole alkaloids, many of which possess potent tremorgenic activity.In terms of sequential annulation, the strategy involves the following operations: DE -> CDE -> CDEF -> ABCDEF.Proceeding in 23 steps from Wieland-Miescher ketone, the synthesis afforded (-)-paspaline (1) in high enantiomeric purity.
- Mewshaw, Richard E.,Taylor, Michael D.,Smith, Amos B.
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p. 3449 - 3462
(2007/10/02)
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- THE BARRIER FOR 1,2 HYDROGEN SHIFT IN DIALKYL CARBENES
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The products from the thermolysis of 4-diazirinopentanoic acid (2) allow the estimate of an experimental value for the Ea = 1.1 +/- 1 kcal.mol-1 for the barrier height for 1,2 H shift in dialkyl carbenes.
- Stevens, Ian D. R.,Liu, Michael T. H.,Soundararajan, N.,Paike, N.
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p. 481 - 484
(2007/10/02)
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- REDUCTION OF ALLENIC ALCOHOLS BY SACCHAROMYCES CEREVISIAE
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α-Allenic alcohols are reduced by Saccharomyces cerevisiae into the corresponding β-ethylenic alcohols, whereas β-allenic alcohols undergo an isomerization leading to their γ-acetylenic counterparts.
- Gil, Gerard,Ferre, Elisee,Barre, Michael,le Petit, Jean
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p. 3797 - 3798
(2007/10/02)
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- Ring Scission Of Cyclic β-Halogeno-ethers with Samarium Di-iodide: A Synthesis of (E)- and (Z)-Enynols
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The use of samarium di-iodide in place of sodium metal for the ring scission of cyclic β-halogeno-ethers drastically alters the stereochemistry of the resulting olefinic alcohols: using the method, highly stereoselective syntheses of enynols in (Z)- and (E)-forms are reported.
- Crombie, Leslie,Rainbow, Linda J.
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p. 6517 - 6520
(2007/10/02)
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- β-Halogeno Ether Synthesis of Olefinic Alcohols: Stereochemistry of the Ring-scission of 2-Substituted 3-Halogenotetrahydro-pyrans and -furans
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The stereochemical outcome of the sodium ring-scission of 2-substituted 3-halogenotetrahydro-pyrans and -furans, with 2-substitution represented by alkyl, alkenyl or aryl, is presented.Although the cis- and the trans-tetrahydropyran scissions are hyghly stereoselective for (E)-5-substituted pent-4-enol, this stereoselectivity breaks down when the 2-substituent is conformationally undiscriminating (deuterium) or has substantial anomeric effects (methoxy).Consideration of this, along with conformational data from the preceding paper, provides an explanation of the stereoselectivity of the tetrahydropyran scission.Evidence against a radical, and for a carbanion intermediate is presented and a common, very rapidly inverting, 3-carbanion is considered to be formed from either cis- or trans-stereoisomers.Ring scission is also rapid (the carbanion cannot be trapped), but less rapid than carbanion inversion, and takes place before the slower conformational inversion can occur so that the (E)/(Z)-nature of the unsaturated alcohol produced is controlled by the initial tetrahydropyran conformation.The unstereospecific nature of the ring scission of both cis- and trans-2-alkyl-3-chlorotetrahydrofurans is explained as a consequence of their existence in conformational equilibria. The high stereoselectivity of the ring scission of cis- and trans-3-chloro-2,3-dimethyltetrahydropyrans, and the poor stereoselectivity of the scission of 2-alkyl-3-chloro-2-methyltetrahydrpyrans, is explained; the reaction of sodium with 2-butyl-3,3-dichlorotetrahydropyran is considered.Using the ring-scission of 3-chlor-2-ethyltetrahydropyran, short syntheses of (+/-)-endo-brevicomin are described to illustrate the utility of β-halogen ether synthesis.
- Crombie, Leslie,Wyvill, Robert D.
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p. 1983 - 1996
(2007/10/02)
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- Transition-Metal-Promoted Alkylations of Unsaturated Alcohols: The Selective Methylation of Homopropargyl Alcohols via Titanium Tetrachloride-Trimethylaluminum
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The reactions of homopropargyl alcohols with titanium tetrachloride-trimethylaluminum in methylene chloride under mild conditions selectively yield after hydrolysis alkenols of the type HOCH(R)CH2CH=C(R')CH3, R =H, Me, and Et and R'= H, Me, Et, n-Pr, i-Pr, n-C4H9, n-C5H11, and Ph.
- Ewing, James C.,Ferguson, Gregory S.,Moore, Douglas W.,Schultz, Frederick W.,Thompson, David W.
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p. 2124 - 2128
(2007/10/02)
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- SYNTHESIS OF E-HOMOALLYLIC ALCOHOLS, γ-HYDROXYKETONES, AND CYCLOPROPYL KETONES FROM 3-DIPHENYLPHOSPHINOYL (Ph2PO) PROPANOLS BY ACYL TRANSFER
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Carboxyl transfer (O*C) on 3-Ph2PO propyl esters (9) gives an intermediate (10) from which the Ph2PO group may be removed by the Horner-Witting reaction or by Ph2PO transfer (C*O) to give the title compounds.
- Wallace, Paul,Warren, Stuart
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p. 5713 - 5716
(2007/10/02)
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- The Stereochemistry of the Cyclic β-Halogeno-ether Synthesis of Olefinic Alcohols
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The (Z)/(E) composition of olefinic alcohols produced by sodium ring-scission of cyclic β-halogeno-ethers can be accounted for by a mechanism involving fast electron transfer and carbanion inversion, with ring-cleavage speedier than conformational inversion.
- Crombie, Leslie,Wyvill, Robert D.
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p. 1056 - 1058
(2007/10/02)
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- 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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- TITANIUM-MEDIATED AND NEIGHBORING-GROUP ASSISTED δ-METHYLATION OF HOMOALLYL ALCOHOLS : A NEW REGIO- AND STEREOSELECTIVE CC-LINKING REACTION
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Upon treatment with dimethyltitanium dichloride or trimethylaluminium in the presence of titanium tetrachloride, a hydrogen atom at the olefinic 4-position is replaced by a methyl group.Terminal homoallyl alcohols afford (E)-isomers.If the double bond is an internal one, the carbon chain (at the other side of the hydroxy group) leaves its original position to the enterning methyl group and switches to the other one at the same carbon atom.
- Fujita, Katsuramaru,Moret, Etienne,Schlosser, Manfred
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p. 1819 - 1822
(2007/10/02)
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