- Using Neighboring-Group Participation for Acyclic Stereocontrol in Diastereoselective Substitution Reactions of Acetals
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Neighboring-group participation of an ester enabled stereocontrol in substitution reactions of acyclic acetals. The ester group formed a trans-fused dioxolenium ion intermediate, which underwent a substitution reaction at the acetal carbon atom to afford the product with high diastereoselectivity. Neighboring-group participation was confirmed by isolating dioxolane products resulting from nucleophilic addition at C-2 of a 1,3-dioxolenium ion intermediate. Using a pivaloate ester as the participating group in combination with strong nucleophiles produced substitution products with diastereoselectivities of ≥90:10.
- Ramdular, Amanda,Woerpel, K. A.
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supporting information
(2020/06/08)
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- Lewis Base/Br?nsted Acid Co-Catalyzed Asymmetric Thiolation of Alkenes with Acid-Controlled Divergent Regioselectivity
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A divergent strategy for the facile preparation of various enantioenriched phenylthio-substituted lactones was developed based on Lewis base/Br?nsted acid co-catalyzed thiolation of homoallylic acids. The acid-controlled regiodivergent cyclization (6-endo vs. 5-exo) and acid-mediated stereoselective rearrangement of phenylthio-substituted lactones were explored. Experimental and computational studies were performed to clarify the origins of the regioselectivity and enantioselectivity. The calculation results suggest that C?O and C?S bond formation might occur simultaneously, without formation of a commonly supposed catalyst-coordinated thiiranium ion intermediate and the potential π–π stacking between substrate and SPh as an important factor in the enantio-determining step. Finally, this methodology was applied in the rapid syntheses of the bioactive natural products (+)-ricciocarpin A and (R)-dodecan-4-olide.
- Luo, Hui-Yun,Dong, Jia-Wei,Xie, Yu-Yang,Song, Xu-Feng,Zhu, Deng,Ding, Tongmei,Liu, Yuanyuan,Chen, Zhi-Min
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supporting information
p. 15411 - 15418
(2019/11/14)
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- Enantioselective addition of selenosulfonates to α,β-unsaturated ketones
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An organo-catalyzed enantioselective addition of selenosulfonates to α,β-unsaturated ketones was developed for the first time. With a chiral squaramide as an efficient catalyst, the desired α-selenylated ketones were obtained in a good yields with high enantioselectivity up to 89% ee, and good results could be obtained on a gram scale. The products could also be efficiently transformed into useful building blocks with a propenylic stereocenter; the strategy presented in this study may find further applications in organic synthesis.
- Luo, Shilong,Zhang, Nan,Wang, Zhen,Yan, Hailong
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supporting information
p. 2893 - 2901
(2018/05/03)
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- An organocatalyzed Stetter reaction as a bio-inspired tool for the synthesis of nucleic acid-based bioconjugates
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An N-Heterocyclic Carbene (NHC) catalyzed biomimetic Stetter reaction was applied for the first time as a bioconjugation reaction to sensitive nucleoside-type biomolecules to provide original pyrrole linked nucleolipids. A versatile approach allowed the functionalization of thymidine at the three reactive positions (O-5′, O-3′ and N-3) providing a structural diversity oriented synthesis. This strategy was applied to the synthesis of an original glyconucleolipid amphiphile in the hope that the pyrrole aromatic moiety would induce additional self-assembling properties.
- Hamoud, Aladin,Barthélémy, Philippe,Desvergnes, Valérie
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supporting information
p. 1760 - 1769
(2018/03/21)
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- Solvent-Free Aerobic Epoxidation of Dec-1-ene Using Gold/Graphite as a Catalyst
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The oxidation of dec-1-ene has been investigated using gold nanoparticles supported on graphite in the presence of a radical initiator (α,α-azobisisobutyronitrile) using oxygen from air as oxidant. We have investigated the influence of the reaction temperature (70-100 °C), catalyst mass and reaction time on the epoxide yield. In the absence of a radical initiator the reaction does not proceed, although auto-oxidation can occur at higher temperatures in the range studied. However, in the presence of an initiator, selective oxidation occurs and the initiator propagates the reaction through the formation of a peroxy-radical at the allylic C3 position. Graphite enhances the formation of the allylic products dec-1-en-3-ol, dec-1-en-3-one, and dec-2-en-1-ol; however, the addition of gold nanoparticles to the graphite, enhances formation of 1,2-epoxydecane. It is suggested that gold suppresses the formation of allylic products via a Russell termination. Graphical Abstract: [Figure not available: see fulltext.]
- Gupta, Upendra Nath,Dummer, Nicholas F.,Pattisson, Samuel,Jenkins, Robert L.,Knight, David W.,Bethell, Donald,Hutchings, Graham J.
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p. 689 - 696
(2015/08/04)
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- A concise total synthesis of lyngbic acid, hermitamides A and B
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A concise total syntheses of lyngbic acid, hermitamides A and B have been accomplished in a highly enantioselective manner involving CBS asymmetric reduction, hydroboration, and stereospecific Julia-Lythgoe olefination.
- Satyanarayana,Reddy, B.V. Subba,Narender
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p. 6027 - 6029
(2015/01/08)
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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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- The effect of encapsulated Zn-POM on the catalytic activity of MIL-101 in the oxidation of alkenes with hydrogen peroxide
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Zinc monosubstituted Keggin heteropolyanion [PZnMo2W 9O39]5- was electrostatically bound to nanocages of MIL-101 polymer matrix. The Zn-POM@MIL-101 catalyst was characterized by XRD, N2 adsorption, atomic absorption (AAS), and FT-IR spectroscopic methods. The catalytic activity of the new composite material, Zn-POM@MIL-101, was assessed in the oxidation of alkenes using aqueous hydrogen peroxide as oxidant. Zn-POM@MIL-101/H2O2 catalytic system demonstrated good catalytic activity in the oxidation reactions. Zn-POM@MIL-101 was reusable for three catalytic cycles. While the MIL-101 matrix is an active catalyst in these oxidation reactions, the presence of Zn-POM significantly changed the selectivity and reaction times. Copyright
- Saedi, Zahra,Tangestaninejad, Shaharm,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
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experimental part
p. 463 - 473
(2012/05/20)
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- Preparation of allyl and vinyl silanes by the palladium-catalyzed silylation of terminal olefins: A silyl-heck reaction
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Installing silicon is easy! A high-yielding protocol for the palladium-catalyzed silylation of terminal alkenes is reported. This method allows facile conversion of styrenes to E-β-silyl styrenes by using iodotrimethylsilane (TMSI) or chlorotrimethylsilane/lithium iodide (see scheme). Terminal allyl silanes with good E/Z ratios are also readily accessed from α-olefins.
- McAtee, Jesse R.,Martin, Sara E. S.,Ahneman, Derek T.,Johnson, Keywan A.,Watson, Donald A.
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supporting information; experimental part
p. 3663 - 3667
(2012/05/20)
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- Catalytic ring expansion of vinyl oxetanes: Asymmetric synthesis of dihydropyrans using chiral counterion catalysis
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Acid Showdown! The first catalytic ring expansion of vinyl oxetanes to 3,6-dihydro-2H-pyrans is described. Copper(II) triflate emerged as the best catalyst for this new transformation, which has broad scope as demonstrated by the eighteen examples included. The symmetric vinyl oxetane substrate can be asymmetrically desymmetrized when using either chiral Lewis or Bronsted acids as catalysts. Copyright
- Guo, Boying,Schwarzwalder, Gregg,Njardarson, Jon T.
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supporting information; experimental part
p. 5675 - 5678
(2012/07/03)
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- Allylation of nitrosobenzene with pinacol allylboronates. A regioselective complement to peroxide oxidation
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Addition of nitrosobenzene to pinacol allylboronates leads to oxidation of the organoboron with concomitant rearrangement of the substrate alkene. This reaction appears to proceed by allylboration of the nitroso group in analogy to carbonyl and imine allylation reactions. Remarkably, the N-O bond is cleaved during the reaction such that simple alcohols are the final reaction product.
- Kyne, Robert E.,Ryan, Michael C.,Kliman, Laura T.,Morken, James P.
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scheme or table
p. 3796 - 3799
(2010/10/21)
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- Cationic NHC-gold(I) complexes: Synthesis, isolation, and catalytic activity
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The reaction of [(NHC)AuCl] complexes (NHC = N-heterocyclic carbene) with a chloride abstractor of the type AgX, where X is a non-coordinating anion, led, in the presence of a neutral coordinating solvent S, to a series of cationic gold(I) complexes of formulae [(NHC)Au(S)]X. Hence, different cationic NHC-gold(I) species bound to acetonitrile, pyridine, 2-Br-pyridine, 3-Br-pyridine, norbornadiene, and THF could be synthesized and characterized by 1H and 13C NMR spectroscopies. Among these, the results of X-ray diffraction studies for [(IPr)Au(NCMe)]SbF6, [(IAd)Au(NCMe)]PF6, [(IPr)Au(pyr)]PF6, [(IPr)Au(2-Br-pyr)]PF6, [(IPr)Au(3-Br-pyr)]PF6 are discussed. As special feature, the structure of [(IPr)Au(2-Br-pyr)]PF6 presented a secondary interaction between the gold and bromine atoms. Additionally, while attempting to obtain crystals of [(IPr)Au(nbd)]PF6, we crystallized a decomposition product featuring a very rare PF4- anion as bridging ligand with formulae [(μ-PF4)((IPr)Au)2]PF4. The observation of a possible P-F bond activation has important implications for cationic Au-based homogeneous catalysis. Finally, we compared the catalytic activities of the different cationic [(NHC)Au(S)]X complexes in the allylic acetate rearrangement reaction and notably observed the inertness of pyridine-based catalysts.
- de Frémont, Pierre,Marion, Nicolas,Nolan, Steven P.
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experimental part
p. 551 - 560
(2009/06/05)
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- Macrolides from the scent glands of the tropical butterflies Heliconius cydno and Heliconius pachinus
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The four major components present in scent gland extracts of the male Costa Rica longwing butterflies Heliconius cydno and Heliconius pachinus were identified as 12- and 14-membered macrolides containing a C18-carbon skeleton. By use of micro-reactions and spectrometric examinations, structural proposals were made and subsequently proven by synthesis, using ring-closing-metathesis as the key steps. These macrolides, (9Z,11E,13S)- octadeca-9,11-dien-13-olide (5, S-coriolide), (9Z,11E,13S,15Z)-octadeca-9,11,15- trien-13-olide (6), (9Z,13S)-octadec-9-en-13-olide (13), and (9Z,11S)-octadec-9-en-11-olide (25), are biosynthetically obviously derived from oleic, linoleic, and linolenic acids. Their absolute configurations were determined by gas chromatographic investigations on chiral phases, showing all to possess (S)-configuration. The Royal Society of Chemistry.
- Schulz, Stefan,Yildizhan, Selma,Stritzke, Katja,Estrada, Catalina,Gilbert, Lawrence E.
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p. 3434 - 3441
(2008/09/19)
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- The nature of oxidizing particles in the catalytic decomposition of H 2O2 with Fe(III) salts in acetonitrile
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Different oxidizing particles were shown to form in the decomposition of hydrogen peroxide in acetonitrile catalyzed by the Fe(ClO4) 3 and FeCl3 salts, namely, the HO? radical and, evidently, the ferryl ion (FeIV = O)2+, respectively. This difference was established for the examples of oxygenation of alkanes and olefins. Clear-cut differences in the kinetic behavior of the two catalytic systems and their oxidation selectivity were observed.
- Kozlov,Nizova,Shul'pin
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p. 184 - 187
(2007/10/03)
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- Hydrogen peroxide oxygenation of alkanes including methane and ethane catalyzed by iron complexes in acetonitrile
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This paper describes an investigation of the alkane oxidation with hydrogen peroxide in acetonitrile catalyzed by iron(III) perchlorate (1), iron(III) chloride (2), iron(III) acetate (3) and a binuclear iron(III) complex with 1,4,7-triazacyclononane (4). The corresponding alkyl hydroperoxides are the main products. Nevertheless in the kinetic study of cyclohexane oxidation, the concentrations of oxygenates (cyclohexanone and cyclohexanol) were measured after reduction of the reaction solution with triphenylphosphine (which converts the cyclohexyl hydroperoxide to the cyclohexanol). Methane and ethane can be also oxidized with TONs up to 30 and 70, respectively. Chloride anions added to the oxidation solution with 1 activate the perchlorate iron derivative in acetonitrile, whereas the water as additive inactivates 2 in the H 2O2 decomposition process. Pyrazine-2-carboxylic acid (PCA) added to the reaction mixture decreases the oxidation rate if 1 or 2 are used as catalysts, whereas compounds 3 and 4 are active as catalysts only in the presence of small amount of PCA. The investigation of kinetics and selectivities of the oxidations demonstrated that the mechanisms of the reactions are different. Thus, in the oxidations catalyzed by the 1, 3+PCA and 4+ PCA systems the main oxidizing species is hydroxyl radical, and the oxidation in the presence of 2 as a catalyst has been assumed to proceed (partially) with the formation of ferryl ion, (FeIV=O)2+. In the oxidation catalyzed by the 4+PCA system (TONs attain 240) hydroxyl radicals were generated in the rate-determining step of monomolecular decomposition of the iron diperoxo adduct containing one PCA molecule. A kinetic model of the process which satisfactorily describes the whole set of experimental data was suggested. The constants of supposed equilibriums and the rate constant for the decomposition of the iron diperoxo adduct with PCA were estimated.
- Shul'pin, Georgiy B.,Nizova, Galina V.,Kozlov, Yuriy N.,Cuervo, Laura Gonzalez,Su?ss-Fink, Georg
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p. 317 - 332
(2007/10/03)
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- A highly stereoselective synthesis of Z-disubstituted olefin by O-assisted Still-Wittig rearrangement
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In the Still-Wittig rearrangement, stannylated methyl (E)-allylic ethers having an aliphatic side chain (1a-c) exhibited the usual similar stereoselectivity, although the poor stereoselectivity was remarkably improved by the assistance of an alkoxy moiety on the alkenyl chain. A stannylated methyl (Z)-allylic ether bearing an alkoxy moiety on the alkenyl chain (1e) also showed a high E selectivity as previously reported.
- Fujii, Kazushige,Hara, Osamu,Fujita, Yoko,Sakagami, Youji
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p. 389 - 392
(2007/10/03)
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- Carbon-carbon bond forming reactions with oxiranyl radicals
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Substituted oxiranyl radicals have been generated from glycidic acids. The cyclization of these species, the stereochemistry of the resultant products, and an intermolecular application of these reactive species is considered.
- Ziegler, Frederick E.,Wang, Yizhe
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p. 6299 - 6302
(2007/10/03)
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- Stereoselective Synthesis of Pyrrolizidine Alkaloids from Nitroalkanones
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Reduction of 5-nitropentadecane-2,8-dione (11), synthesized by a Michael reaction from nitromethane, methyl vinyl ketone, and dec-1-en-3-one, gave, depending on the conditions, two epimeric 3-heptyl-2,3,5,6,7,7a-hexahydro-5-methyl-1H-pyrrolizines as the main products: Catalytic hydrogenation (Pd/C) afforded the expected 7aα-hydro epimer 1b with cis-oriented H-atoms at C(3), C(5), and C(7a).NaBH3CN/NH4OAc reduction of the nitro-dione 11 yielded all four diastereoisomers with the 7aβ-hydro epimer 1a as the predominant component; 1a is a pheromone of the cryptic thief ant Solenopsis sp.The N-atom of the pyrrolizidine ring stems from NH4OAc exclusively as shown by reduction of 11 with NaBH3CN/(15N)H4OAc.
- Janowitz, Agnes,Vavrecka, Mojmir,Hesse, Manfred
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p. 1352 - 1361
(2007/10/02)
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- TRANSFORMATION OF 4-NITROALKANE-1,7-DIONES INTO PYRROLIZIDINES
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Depending on the conditions the reduction of 5-nitropentadecane-2,8-dione (4) gave as main products the two isomeric pyrrolizidines 1a (xenovenine, NaBH3CN/NH4OAc; as 15N-1a with NaBH3CN/15NH4OAc) and 1b (H2-Pd/C), respectively)
- Vavrecka, Mojmir,Janowitz, Agnes,Hesse, Manfred
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p. 5543 - 5546
(2007/10/02)
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- Synthesis of 1-Acyl-2-alkylcyclopropanecarboxylic Esters from 2-Alkenylphosphonium Salts
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The one-pot reaction of allyltriphenylphosphonium bromide with the sodium salts of β-keto esters leads to the formation of alkyl 1-acyl-2-alkylcyclopropanecarboxylates.
- Jacoby, D.,Celerier, J. P.,Petit, H.,Lhommet, G.
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p. 301 - 304
(2007/10/02)
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- GRIGNARD REAGENTS AS POWDERS : PREPARATION AND REACTIVITY
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The TDA-1 chelating agent is able to complex Grignard reagents.This complexation leads to powders.The preparation is general and the complexes "RMgX/TDA-1" are easily prepared from every type of Grignard reagents.These solids are stable under nitrogen and can be titrated and used as Grignard reagents.The study of their chemical reactivity shows a behaviour comparable to that of conventional Grignard reagents, the rate of reactions however being decreased.Selective addition onto a mixture of aldehyde and ketone is possible.Interestingly the reactions can be performed in hydrocarbon solvents (toluene, light petroleum, cyclohexane).
- Boudin, Alain,Cerveau, Genevieve,Chuit, Claude,Corriu, Robert J.P.,Reye, Catherine
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p. 171 - 180
(2007/10/02)
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- Base-catalysed Rearrangement of β-Hydroxyvinylsilanes to Allyl Silyl Ethers
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A 1,3-silyl group shift from carbon to oxygen occurs readily when β-hydroxyvinylsilanes are treated with catalytic amounts of sodium hydride in hexamethylphosphoric triamide, thus providing the first demonstration of the rearrangement of silicon from sp2-carbon to oxygen.
- Sato, Fumie,Tanaka, Youichi,Sato, Masao
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p. 165 - 166
(2007/10/02)
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- Synthesis of 1,2,3-Decanetriol Stereoisomers
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The synthesis and 13C NMR spectra of 1,2,3-decanetriol stereoisomers are described. High enantiomeric purity triols are obtained by chromatographic resolution of diastereomeric carbamates derived from 1-decyn-3-ol and (R)-1-(1-naphthyl)ethylamine. The triol is obtained by conversion of the acetylene to an olefin, stereoselective epoxidation with tert-butyl hydroperoxide and a transition-metal catalyst, and stereospecific ring opening of the epoxide with KOH.
- Rinaldi, Peter L.,Levy, George C.
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p. 4348 - 4351
(2007/10/02)
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