- Conversion of α,β-unsaturated ketones into α-hydroxy ketones using an Mn(III) catalyst, phenylsilane and dioxygen: Acceleration of conjugate hydride reduction by dioxygen
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Treatment of a variety of α,β-unsaturated ketones with Mn(dpm)3 (3 mol%)/PhSiH3 (1.3 equiv.)/isopropyl alcohol/O2, followed by reductive work-up with P(OEt)3 resulted in the formation of α-hydroxy-ketones. (C) 2000 Elsevier Science Ltd.
- Magnus,Payne,Waring,Scott,Lynch
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Read Online
- Reduction of Ketones and Aldehydes via Catalytic Hydrosilylation Using Triethoxysilane and Trimethoxysilane
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It was found that ketones and aldehydes can be effectively reduced via catalytic hydrosilylation using triethoxysilane and trimethoxysilane in the presence of RhCl(PPh3)3 or RuCl2(PPh3)3, followed by ethanolysis or methanolysis.
- Matsumoto, Hideyuki,Hoshino, Yoshikazu,Nagai, Yoichiro
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Read Online
- Bioluminescence in the limpet-like snail, latia neritoides
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Latia neritoides is a small limpet-like snail that produces a bright green bioluminescence; it is found only in New Zealand streams. The light-emitting system is unique. Although Latia bioluminescence has been studied since 1880, its mechanism is unclear. Shimomura and Johnson clarified the elements of the mechanism, including the structures of luciferin and luciferase, in 1968. However, neither the emitter nor the mechanism of the excited state of luciferin has been determined. We studied molecular mechanisms to clarify the characteristics of luciferin and luciferase and to produce a new application for this system.
- Ohmiya, Yoshihiro,Kojima, Satoshi,Nakamura, Mitsuhiro,Niwa, Haruki
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Read Online
- Synthesis of Latia luciferin benzoate analogues and their bioluminescent activity
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The bioluminescent system of the univalve shell Latia neritoides exhibits a luciferin-luciferase reaction. We study the enol formate structure of Latia luciferin, which is expected to be important for luminescent activity. The Latia luciferin analogues with an enol substituted benzoate moiety were synthesized and their bioluminescent activity was measured. The Latia luciferin benzoate analogues delay emission for natural luciferin in bioluminescence, indicating that the Latia bioluminescent activity can be controlled by the design of the enol ester.
- Nakamura, Mitsuhiro,Masaki, Mizuki,Maki, Shojiro,Matsui, Ryo,Hieda, Minako,Mamino, Masashi,Hirano, Takashi,Ohmiya, Yoshihiro,Niwa, Haruki
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Read Online
- Asymmetric Cation-Olefin Monocyclization by Engineered Squalene–Hopene Cyclases
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Squalene–hopene cyclases (SHCs) have great potential for the industrial synthesis of enantiopure cyclic terpenoids. A limitation of SHC catalysis has been the enzymes’ strict (S)-enantioselectivity at the stereocenter formed after the first cyclization step. To gain enantio-complementary access to valuable monocyclic terpenoids, an SHC-wild-type library including 18 novel homologs was set up. A previously not described SHC (AciSHC) was found to synthesize small amounts of monocyclic (R)-γ-dihydroionone from (E/Z)-geranylacetone. Using enzyme and process optimization, the conversion to the desired product was increased to 79 %. Notably, analyzed AciSHC variants could finely differentiate between the geometric geranylacetone isomers: While the (Z)-isomer yielded the desired monocyclic (R)-γ-dihydroionone (>99 % ee), the (E)-isomer was converted to the (S,S)-bicyclic ether (>95 % ee). Applying the knowledge gained from the observed stereodivergent and enantioselective transformations to an additional SHC-substrate pair, access to the complementary (S)-γ-dihydroionone (>99.9 % ee) could be obtained.
- Aeberli, Natalie,Berweger, Raphael,Bornscheuer, Uwe T.,Buller, Rebecca,Dossenbach, Sandro,Eichenberger, Michael,Eichhorn, Eric,Flachsmann, Felix,Hüppi, Sean,Hortencio, Lucas,Patsch, David,Voirol, Francis,Vollenweider, Sabine
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p. 26080 - 26086
(2021/09/20)
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- Highly Selective Hydrogenation of C═C Bonds Catalyzed by a Rhodium Hydride
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Under mild conditions (room temperature, 80 psi of H2) Cp*Rh(2-(2-pyridyl)phenyl)H catalyzes the selective hydrogenation of the C═C bond in α,β-unsaturated carbonyl compounds, including natural product precursors with bulky substituents in the β position and substrates possessing an array of additional functional groups. It also catalyzes the hydrogenation of many isolated double bonds. Mechanistic studies reveal that no radical intermediates are involved, and the catalyst appears to be homogeneous, thereby affording important complementarity to existing protocols for similar hydrogenation processes.
- Gu, Yiting,Lisnyak, Vladislav G.,Norton, Jack R.,Salahi, Farbod,Snyder, Scott A.,Zhou, Zhiyao
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supporting information
p. 9657 - 9663
(2021/07/19)
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- Capturing the Monomeric (L)CuH in NHC-Capped Cyclodextrin: Cavity-Controlled Chemoselective Hydrosilylation of α,β-Unsaturated Ketones
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The encapsulation of copper inside a cyclodextrin capped with an N-heterocyclic carbene (ICyD) allowed both to catch the elusive monomeric (L)CuH and a cavity-controlled chemoselective copper-catalyzed hydrosilylation of α,β-unsaturated ketones. Remarkably, (α-ICyD)CuCl promoted the 1,2-addition exclusively, while (β-ICyD)CuCl produced the fully reduced product. The chemoselectivity is controlled by the size of the cavity and weak interactions between the substrate and internal C?H bonds of the cyclodextrin.
- Bistri-Aslanoff, Olivia,Derat, Etienne,Leloux, Sébastien,Leyssens, Tom,Ménand, Micka?l,Meijide Suárez, Jorge,Riant, Olivier,Roland, Sylvain,Sollogoub, Matthieu,Xu, Guangcan,Zhang, Pinglu,Zhang, Yongmin
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supporting information
p. 7591 - 7597
(2020/03/23)
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- Recyclable Polyisobutylene-Bound HMPA as an Organocatalyst in Recyclable Poly(α-olefin) Solvents
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This work describes the synthesis of a PIB-bound hexamethylphosphoramide (HMPA) analog and its applications as a recyclable catalyst in allylation of aldehydes and reduction of enones in a recyclable poly(α-olefin) (PAO) polymeric solvent. Kinetic studies of the allylation reaction show that this PIB-bound HMPA analog is as active as HMPA in dichloromethane and PAO and that this PIB-bound catalyst is comparably reactive in heptane and in a PAO solvent. The PIB-bound HMPA catalyst has high phase selective solubility in PAO versus a polar solvent. By using this catalyst in a nonvolatile separable PAO solvent, this catalyst recyclability can be coupled to solvent recyclability, something that is less feasible in a conventional heptane solvent. The result is good recycling of catalyst and solvent through at least 5 cycles using simple gravity-based liquid/liquid extractions. This is in contrast to HMPA or conventional solvents which are less recyclable.
- Fu, Ying-Hua,Bergbreiter, David E.
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p. 6050 - 6058
(2020/10/19)
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- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
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Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
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supporting information
p. 21176 - 21182
(2020/09/17)
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- Method of preparing gamma-ketene from alpha, gamma-unsaturated diketene
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The invention provides a method of preparing gamma-ketene from alpha, gamma-unsaturated diketene. According to the method, single hydrogen silane is used as a silicon hydrogen reducing agent, a palladium complex is used as a catalyst, a Lewis acid is used as an auxiliary agent, and alpha, gamma-unsaturated diketene are subjected to silicon hydrogen reduction reactions to obtain gamma-ketene through a one-step method. The method has the advantages of mild conditions, simple operation, high product selectivity and yield, cheap and easily available silicon hydrogen reducing agent, high catalystactivity, little using amount, and low cost, and has potential of industrial scale-up.
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Paragraph 0038-0055; 0062-0067
(2020/04/06)
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- A ruthenium complex compound for the selective hydrogenation of the dienone method
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The invention provides a selective hydrogenation of ruthenium complex α, γ - unsaturated dienone method, and in particular relates to a method for using the hydrogen in the catalyst under the action of the α, γ - unsaturated dienone is reduced to the corresponding γ - unsaturated ketone of the method, the catalyst employed for ruthenium complex, a ruthenium precursor and the ligand in-situ prepared. Major advantage of this invention is characterized in that the catalyst is composed of metal precursor and the ligand in-situ prepared, simple operation, high catalyst activity; pyridine, quinoline nitrogen-containing aromatic heterocycle such as the adding of the poisoned medicinal preparation, effectively restraining the product γ - unsaturated ketone transition hydrogenation reaction, an excellent selectivity, the cost is low.
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Paragraph 0035-0049
(2019/07/04)
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- Bidirectional Hiyama–Denmark Cross-Coupling Reactions of Bissilyldeca-1,3,5,7,9-pentaenes for the Synthesis of Symmetrical and Non-Symmetrical Carotenoids
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The construction of the carotenoid skeleton by Pd-catalyzed Csp2?Csp2 cross-coupling reactions of symmetrical and non-symmetrical 1,10-bissilyldeca-1,3,5,7,9-pentaenes and the corresponding complementary alkenyl iodides has been developed. Reaction conditions for these bidirectional and orthogonal Hiyama–Denmark cross-coupling reactions of bisfunctionalized pentaenes are mild and the carotenoid products preserve the stereochemical information of the corresponding oligoene partners. The carotenoids synthesized in this manner include β,β-carotene and (3R,3′R)-zeaxanthin (symmetrical) as well as 9-cis-β,β-carotene, 7,8-dihydro-β,β-carotene and β-cryptoxanthin (non-symmetrical).
- Rivas, Aurea,Pérez-Revenga, Víctor,Alvarez, Rosana,de Lera, Angel R.
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supporting information
p. 14399 - 14407
(2019/11/03)
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- Method for selectively hydrogenating alpha, beta-unsaturated carbonyl compound by cobalt complex
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The invention provides a method for selectively hydrogenating an alpha, beta-unsaturated carbonyl compound. The method for selectively hydrogenating the alpha, beta-unsaturated carbonyl compound comprises the steps that first, a cobalt metal precursor and a carbene ligand are coordinated in a solution to obtain a cobalt complex, and the cobalt complex selectively enables the alpha, beta-unsaturated carbonyl compound to be reduced into a corresponding saturated carbonyl compound in a hydrogen atmosphere under the activation of an activator. The method for selectively hydrogenating the alpha, beta-unsaturated carbonyl compound has the main advantages that cobalt is used as a catalyst, and metal cobalt is cheap and easy to obtain relative to noble metal such as palladium, ruthenium, osmium, iridium and platinum, and the catalyst cost is greatly reduced; secondly, the carbene ligand used in the method has the advantages of simple structure, low price, strong coordination ability with cobalt atoms compared with a commonly used phosphine ligand; and finally, the addition of the activator can further significantly increase the activity of the cobalt catalyst. The hydrogenation reaction condition is mild, the reaction rate is high, substantially no carbonyl hydrogenation side reaction occurs, and the carbonyl compound can be obtained in a high yield.
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Paragraph 0055-0057
(2019/11/20)
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- New biobased tetrabutylphosphonium ionic liquids: Synthesis, characterization and use as a solvent or co-solvent for mild and greener Pd-catalyzed hydrogenation processes
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Phosphonium-based Ionic Liquids (PhosILs) with natural organic derived anions (l-lactate, l-tartrate, malonate, succinate, l-malate, pyruvate, d-glucuronate, d-galacturonate, ferulate, p-coumarate) were easily prepared by acid-base method from tetrabutylphosphonium hydroxide and an excess of the corresponding acid with good yields. Their characterization was realized through classical NMR, IR and elemental analysis techniques; their viscosity and ATG parameters were also determined. These ionic liquids showed good performance and recyclability in the selective Pd-catalyzed hydrogenation of alkenes, polyenes like linoleic acid and enantioselective hydrogenation of unsaturated ketones such as isophorone at room temperature under atmospheric H2 pressure. Furthermore, NMR studies leading to computational calculations were performed to establish easily the composition of the resulting mixture obtained through the hydrogenation of linoleic acid.
- Hayouni, Safa,Robert, Anthony,Ferlin, Nadège,Amri, Hassen,Bouquillon, Sandrine
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p. 113583 - 113595
(2016/12/16)
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- Simple, chemoselective hydrogenation with thermodynamic stereocontrol
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Few methods permit the hydrogenation of alkenes to a thermodynamically favored configuration when steric effects dictate the alternative trajectory of hydrogen delivery. Dissolving metal reduction achieves this control, but with extremely low functional group tolerance. Here we demonstrate a catalytic hydrogenation of alkenes that affords the thermodynamic alkane products with remarkably broad functional group compatibility and rapid reaction rates at standard temperature and pressure.
- Iwasaki, Kotaro,Wan, Kanny K.,Oppedisano, Alberto,Crossley, Steven W. M.,Shenvi, Ryan A.
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supporting information
p. 1300 - 1303
(2014/02/14)
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- HYDROGENATION OF DIENALS WITH RHODIUM COMPLEXES UNDER CARBON MONOXIDE FREE ATMOSPHERE
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The present invention relates to the field of catalytic hydrogenation and, more particularly, to a process for the reduction by hydrogenation, using molecular H2, of a C6-C20 conjugated dienal into the corresponding deconjugated enal, characterized in that said process is carried out in the presence of a catalytic system comprising at least a base and at least one complex in the form of a rhodium complex comprising a C34-C60 bidentate diphosphine ligand (L2) coordinating the rhodium.
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Page/Page column 24-25
(2012/11/14)
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- Bioactive compounds with added value prepared from terpenes contained in solid wastes from the olive oil industry
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Starting from solid wastes from two-phase olive-oil extraction, the pentacyclic triterpenes oleanolic acid and maslinic acid were isolated. These natural compounds were transformed into methyl olean-12-en-28-oate (5), which then was transformed into several seco-C-ring triterpene compounds by chemical and photolytic modifications. The triene seco-products were fragmented through several oxidative procedures to produce, simultaneously, cis- and trans-decalin derivatives, both potential synthons for bioactive compounds. The chemical behavior of the isolated fragments was investigated, and a suitable approach to several low-molecular-weight terpenes was performed. These are interesting processes for the value-addition to solid waste from the olive-oil industry.
- Parra, Andres,Lopez, Pilar E.,Garcia-Granados, Andres
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experimental part
p. 421 - 439
(2010/09/05)
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- Preparation of 9α-fluorinated sesquiterpenic drimanes and evaluation of their antifeedant activities
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The preparation of 9α-fluoro analogues of both natural and unnatural drimane-type sesquiterpenes is described. Their synthesis began with the initial preparation of methyl 8-keto-12-nordriman-11-oate from β-ionone and entailed the electrophilic fluorination of C-9 for the stereoselective introduction of the fluorine atom. The drimane skeleton was completed from, the intermediate 9α-fluoro-8-keto-12-nordrimane system by means of different reactions at the C-8 ketone carbonyl group, essentially Wittig methylenation, cyanohydrin formation or palladium-catalysed carbonylation of the corresponding enol triflate. Further manipulation of the functionalization derived from these key reactions allowed the preparation, among others, of 9α-fluorodrimanes, which are structurally and functionally related to albicanic acid, drimenin and olepupuane. Also described are the reactivities of some of the fluorine-containing systems prepared and a comparative study of the antifeedant activities of a selection of 9α-fluorodrimanes and the corresponding hydrogen analogues against several, insect species with different feeding ecologies (Spodoptera littoralis, Myzus persicae and Rhopalosiphum padi), which revealed a significant increase in the antifeedant activities of some of the fluorinated drimane analogues.
- Abad, Antonio,Agullo, Consuelo,Cunat, Ana C.,Gonzalez-Coloma, Azucena,Pardo, David
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supporting information; experimental part
p. 2182 - 2198
(2010/07/06)
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- Lewis base-catalyzed conjugate reduction and reductive aldol reaction of α,β-unsaturated ketones using trichlorosilane
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Lewis bases such as Ph3P=O and HMPA catalyze the 1,4-reduction of α,β-unsaturated ketones with trichlorosilane, and because the 1,2-reduction of aldehydes scarcely proceeded under the conditions, one-pot reductive aldol reactions with aldehydes were successfully achieved; preliminary studies using a chiral Lewis base revealed a high potential for enantioselective catalysis. The Royal Society of Chemistry.
- Sugiura, Masaharu,Sato, Norimasa,Kotani, Shunsuke,Nakajima, Makoto
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supporting information; experimental part
p. 4309 - 4311
(2009/03/12)
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- High-throughput screening of catalysts by combining reaction and analysis
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(Figure Presented) Drudgery minimized, efficiency maximized: By combining catalysis and separation in microcapillaries greater than 2 cm in length, it is possible to efficiently determine the reaction kinetics for entire libraries of substrates. This was demonstrated for hydrogenations over highly active Pd nanoparticles and ring-closing metatheses over the Grubbs 2nd generation catalyst. R: reagents, P: products.
- Trapp, Oliver,Weber, Sven K.,Bauch, Sabrina,Hofstadt, Werner
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p. 7307 - 7310
(2008/09/18)
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- Conjugate reduction of α,β-unsaturated carbonyl compounds promoted by nickel nanoparticles
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The system composed of nickel(II) chloride, lithium metal, a catalytic polymer-supported arene, and ethanol, has been efficiently applied to the conjugate reduction of a variety of α,β-unsaturated carbonyl compounds (ketones and carboxylic acid derivatives) under very mild reaction conditions. Georg Thieme Verlag Stuttgart.
- Alonso, Francisco,Osante, I?aki,Yus, Miguel
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p. 3017 - 3020
(2008/02/12)
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- Synthesis of alkenes from tertiary esters utilizing the triphenylphosphine-iodine system
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The treatment of tertiary esters with triphenylphosphine and iodine under mild conditions gives the most stable alkene in good yield. Formates, acetates and trifluoroacetates were studied.
- Alvarez-Manzaneda,Chahboun,Cabrera Torres,Alvarez,Alvarez-Manzaneda,Haidour,Ramos
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p. 1075 - 1077
(2007/10/03)
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- Chlorosulfonic acid as a convenient electrophilic olefin cyclization agent
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Among several sulfonic acids studied (MeSO3H, p-TsOH, H2SO4, ClSO3H, FSO3H), the scarcely used chlorosulfonic acid showed to be an efficient agent for electrophilic olefin cyclizations with internal nucleophilic termination, in a similar manner that is well-established with fluorosulfonic acid. Its availability, lower price and relatively lesser handling problems makes ClSO3H an advantageous cyclizing agent particularly for high-scale applications. The stereochemical outcome of these cyclizations has been rationalized.
- Linares-Palomino, Pablo J.,Salido, Sofía,Altarejos, Joaquín,Sánchez, Adolfo
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p. 6651 - 6655
(2007/10/03)
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- Synthesis of (+)-manoalide via a copper(I)-mediated 1,2-metalate rearrangement
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An enantiospecific synthesis of the phospholipase A2 inhibitor (+)-(4R)-manoalide is reported in which all 25 carbons of the sesterterpenoid skeleton are constructed from 3-furaldehyde, trimethylalane, oxirane, CO, β-ionone, and propargyl bromide. The overall yield for the longest linear sequence (12 steps) is 12%. Key steps include (a) a zirconium-catalyzed carboalumination reaction to construct the C10-C11 trisubstituted alkene, (b) a Cu(I)-mediated 1,2-metalate rearrangement to construct the C6-C7 trisubstituted alkene, (c) a Sharpless kinetic resolution to secure the (4R)-stereochemistry, (d) generation of a 5-stannyl-2,3-dihydrofuran by Mo-catalyzed cycloisomerization of a homopropargylic alcohol, and (e) construction of the hydroxyfuranone ring by photooxidation of a silylfuran.
- Pommier, Agnès,Stepanenko, Viatcheslav,Jarowicki, Krzysztof,Kocienski, Philip J.
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p. 4008 - 4013
(2007/10/03)
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- Total synthesis of yahazunol, zonarone and isozonarone
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The synthesis of the marine natural products zonarone and isozonarone was achieved via (+)-albicanic acid, a sesquiterpene of the drimane type. Coupling of the appropiate drimane-synthon with lithiated hydroquinone ethers led to sesquiterpene arenes, which were further modified to the target molecules. Stereoselective epoxidation followed by regioselective opening of the oxirane ring yielded yahazunol.
- Laube, Thorsten,Schr?der, J?rg,Stehle, Ralf,Seifert, Karlheinz
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p. 4299 - 4309
(2007/10/03)
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- Compounds having protected hydroxy groups
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The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
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- Compounds having protected hydroxy groups
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The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
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- Precursors for fragrant ketones and fragrant aldehydes
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The present invention refers to fragrance precursors of formula I for a fragrant ketone of formula II and one or more fragrant aldehydes or ketones of formula III and IV, These fragrance precursors are useful in perfumery, especially in the fine and functional perfumery.
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- Ketone precursors for organoleptic compounds
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The invention discloses ketones of formula I: wherein, Y is an optionally substituted alkyl, cycloalkyl, or cycloalkylalkyl, wherein each alkyl group is straight or branched and each alkyl and cycloalkyl group is saturated or unsaturated; R1is hydrogen or a C1-6alkyl group that is substituted, saturated or unsaturated, straight or branched; A is a chromophoric substituted aromatic ring or ring system; n is an integer; and with the proviso that formula I is not 2-ethoxy-1-phenyl-ethanone. These compositions are useful for the delivery of organoleptic compounds, especially of flavors, fragrances, masking agents and antimicrobial compounds.
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- A conjugate addition-radical cyclisation approach to sesquiterpene-phenol natural products
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A conjugate addition-radical cyclization approach to sesquiterpenephenol natural products was discussed. The first step involved the conjugate addition of an organocopper species to a chromone-3-carboxylate which resulted in 2,2-disubstituted chroman-4-ones. The second step was the generation of a β-ketoester radical. The last step involved a stereoselective manganese(III) acetate-mediated radical cyclization reaction.
- Crombie, Barry S.,Smith, Colin,Varnavas, Christalla Z.,Wallace, Timothy W.
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p. 206 - 215
(2007/10/03)
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- Bioluminescence activity of Latia luciferin analogs
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Latia luciferin analogs were synthesized and their bioluminescence activities were measured. The Latia luciferase was found to recognize strictly the 2,6,6-trimethylcyclohexene ring moiety in the luciferin structure. While the enol ether analogs exhibited no bioluminescence activity, the corresponding enol acetate analog possessed 60% activity compared to natural luciferin having an enol formate structure, implying that the initial step of the light producing reaction is an enzymatic hydrolysis to yield the corresponding enolate anion. (C) 2000 Elsevier Science Ltd.
- Kojima, Satoshi,Maki, Shojiro,Hirano, Takashi,Ohmiya, Yoshihiro,Niwa, Haruki
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p. 4409 - 4413
(2007/10/03)
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- Total synthesis of the marine sesquiterpene hydroquinones zonarol and isozonarol and the sesquiterpene quinones zonarone and isozonarone
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The total synthesis of the naturally occurring sesquiterpene hydroquinones zonarol and isozonarol and the sesquiterpene quinones zonarone and isozonarone was achieved starting from β-ionone, which was transformed via (+)-albicanic acid to (+)-albicanal and (-)-drim-7-en-11-al. Coupling of the aldehydes with lithiated hydroquinone ethers and further modification of the coupling products led to the target molecules. (C) 2000 Elsevier Science Ltd.
- Schr?der, J?rg,Magg, Christine,Seifert, Karlheinz
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p. 5469 - 5473
(2007/10/03)
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- Amberlyst-15-catalyzed intramolecular S(N)2' oxaspirocyclization of secondary allylic alcohols. Application to the total synthesis of spirocyclic ethers theaspirane and theaspirone
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A variety of substituted 1-oxaspiro[4.4]non-6-ene. 1-oxaspiro[4.5]dec-6- ene, 6-oxaspiro[4.5]dec-1-ene and 1-oxaspiro[5.5]undec-7-ene systems have been prepared by utilizing Amberlyst-15-catalyzed intramolecular S(N)2' oxaspirocyclizations of secondary allylic alcohols under mild reaction conditions in quantitative yields. This oxaspirocyclization was applied to the total synthesis of theaspirane and theaspirone from β-ionone in five steps. (C) 2000 Elsevier Science Ltd.
- Young, Jenn-Jong,Jung, Liarng-Jyur,Cheng, Kuang-Ming
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p. 3415 - 3418
(2007/10/03)
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- Conjugate reduction of α,β-unsaturated ketones using an Mn(III) catalyst, phenylsilane and isopropyl alcohol
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Treatment of a variety of α,β-unsaturated ketones with Mn(dpm)3 (3 mol%)/PhSiH3 (1.3 equiv.)/isopropyl alcohol with the exclusion of air resulted in the formation of the saturated ketone. (C) 2000 Elsevier Science Ltd.
- Magnus,Waring,Scott
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p. 9731 - 9733
(2007/10/03)
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- Raney nickel: An efficient reagent to achieve the chemoselective hydrogenation of α,β-unsaturated carbonyl compounds
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Raney Nickel is an effective reagent to achieve the chemoselective reduction of conjugated olefins in σ,β-unsaturated carbonyl compounds that also contain isolated double bonds. Its use is also compatible with a variety of other functional groups.
- Barrero, Alejandro F.,Alvarez-Manzaneda,Chahboun, Rachid,Meneses
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p. 1663 - 1666
(2007/10/03)
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- Resolution of sclareolide as a key intermediate for the synthesis of Ambrox
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Sclareolide was efficiently resolved by a diastereomeric salt formation method using homochiral erythro-2-amino-1,2-diphenylethanol (ADPE) as a resolving agent.
- Koga, Tsukasa,Aoki, Yoshio,Hirose, Takuji,Nohira, Hiroyuki
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p. 3819 - 3823
(2007/10/03)
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- Total synthesis of manoalide
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Me3Al/AlCl3-mediated hetero-Diels-Alder (HDA) additions of 2-silyloxy-1,3-dienes to formylated butenolide 6 containing a protected hydroxy function afford, in one step, a variety of pyranofuranones including manoalide precursor 16, which is a stable monoprotected seco-manoalide.
- Coombs,Lattmann,Hoffmann
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p. 1367 - 1371
(2007/10/03)
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- Mild regioselective catalytic hydrogenation of α,β-unsaturated carbonyl compounds with Lindlar catalyst
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The hydrogen-Lindlar catalyst system is effective for the highly regioselective reduction of α,β-unsaturated carbonyl compounds to the corresponding α,β-saturated compounds.
- Righi, Giuliana,Rossi, Leucio
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p. 1321 - 1327
(2007/10/03)
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- Cu/SiO2: An improved catalyst for the chemoselective hydrogenation of α,β-unsaturated ketones
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Cu/SiO2 can be conveniently used for the quantitative hydrogenation of conjugated enones to saturated ketones, also when another olefinic bond is present in the molecule, under very mild conditions. Molecular H2 or 2-propanol can be used as hydrogen source.
- Ravasio, Nicoletta,Antenori, Marisa,Gargano, Michele,Mastrorilli, Piero
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p. 3529 - 3532
(2007/10/03)
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- Pd/AlPO4 CATALYSED SELECTIVE LIQUID-PHASE HYDROGENATION OF β-IONONE INTO CIS-DIHYDROIONONE
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The liquid-phase hydrogenation of β-ionone 1 was carried out at 302 K with 0.205 MPa of initial hydrogen pressure in methanol on Pd/AlPO4 catalyst (2-3 percent).The cis-dihydroionone 2 was obtained with a 83 percent selectivity which is independent of the degree of conversion.The reaction rate depends on the chloride concentration in the catalyst and the rection selectivity is a function of the support of the Pd.According to the Langmuir-Hinshelwood kinetic models and the Horiuti-Polanyi type mechanism, the reaction order with respect to β-ionone concentration is negative and of one half order with respect to the hydrogen pressure.The comparison with results obtained over Pd/C catalyst and those obtained in the catalytic hydrogenation of α-ionone suggests that the catalytic hydrogenation of β-ionone could take place on two different active sites of the Pd.
- Bouchry, Naima,Aune, Jean-Pierre,Rais, Taoufiq
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p. 439 - 448
(2007/10/02)
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- The liquid-phase catalytic hydrogenation of β-ionone has been carried out using Pd/C catalyst
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The reaction products obtained upon reduction of β-ionone were cis-dihydroionone, dihydro-β-ionone, tetrahydroionone, dihydro-α-ionone and small quantities of alcohols.Selectivity towards each product is not affected by the reaction conditions such as temperature (261-318 K), hydrogen pressure (0.11-0.53 MPa), β-ionone concentration (0.28-2.45 M) and the nature of the solvent.Under our working conditions, the order of the reaction with respect to the substrate is negative and the process is half an order in hydrogen pressure.The catalytic hydrogenation of α-ionone has been carried out in the same conditions and the selectivity of dihydro-α-ionone reaches 76percent.It appears that the conjugate ability of the system in β-ionone is responsible for the selectivity to the cis-dihydroionone (66percent) obtained during the catalytic hydrogenation of the second product. - Key words: catalytic hydrogenation / β-ionone / α-ionone / selectivity / Pd/C / apparent activation energy
- Bouchry, Naima,Aune, Jean-Pierre,Coudurier, Gisele,Rais, Taoufiq
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p. 243 - 248
(2007/10/02)
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- Isolation and synthesis of tanyolides A and B, metabolites of the nudibranch Sclerodoris tanya
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The nudibranch Sclerodoris tanya, which was collected intertidally at La Jolla, contains two sesquiterpene glyceride esters, tanyolides A (4) and B (5). The structures of the tanyolides were elucidated by interpretation of spectral data. The absolute configuration of tanyolide B (5) was determined by synthesis of both enantiomers and the structure of tanyolide A (4) was also confirmed by synthesis. The tanyolides, which are located primarily in the dorsal mantle, deter feeding by two ecologically-relevant predatory fish.
- Krug, Patrick J.,Boyd, Kenneth G.,Faulkner, D. John
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p. 11063 - 11074
(2007/10/02)
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- BIOTRANSFORMATION OF α- AND β-IONONES BY IMMOBILIZED CELLS OF NICOTIANA TABACUM
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Immobilized cells of Nicotiana tabacum reduced the carbon-carbon double bond adjacent to the carbonyl group and then the carbonyl group itself of the dienone compounds, α-ionone and β-ionone: In addition, the selectivity for the reduction of the double bond adjacent to the carbonyl group could be enhanced by performing the biotransformation in medium with a pH near the optimal pH of the enone reductase which specifically catalyses the reduction of the α,β-unsaturated double bond of s-trans-enones. - Key words: Nicotiana tabacum; Solanaceae; plant cell cultures; immobilized cells; dienone; β-ionone; α-ionone; biotransformation.
- Tang, Yi-Xiong,Suga, Takayuki
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p. 737 - 740
(2007/10/02)
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- Process for producing L-ambrox
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(-)-2,5,5,8a-Tetramethyl-1-(carboxymethyl)-2-hydroxydecalin is subjected to lactonization by dehydration to form decahydro-3a,6,6,9a-tetramethyl(3aα,5aβ,9aα,9bβ)-(+)-naphtho[2,1-b]furan-2(1H)-one, which is then reduced with a metal hydride to convert it into (-)-2,5,5,8a-tetramethyl-1-(carboxymethyl)-2-hydroxydecalin, followed by dehydrative cyclization to give L-ambrox. The (-)-2,5,5,8a-tetramethyl-1-(carboxymethyl)-2-hydroxydecalin is produced from its racemic mixture. The resolution is performed using a 1-(aryl)ethylamine. The starting material for the synthesis is beta-ionone.
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- Two Syntheses of Manoalide via Heteroatom-Assisted Alkyne Carbometallation
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Two approaches to the sesterterpenoid phospholipase A2 inhibitors seco-manoalide (3) and manoalide (1) are described based on carbometallation of propargylic alcohols to generate the functionalised C6-C7 trisubstituted alkene.Both syntheses also deploy the photooxidation of a furan in order to generate a 4-substituted 5-hydroxy-2(5H)-furanone moiety.
- Bury, Paul,Hareau, Georges,Kocienski, Philip,Dhanak, Dashyant
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p. 8793 - 8808
(2007/10/02)
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- Chemoselectivity in Catalytic Transfer Hydrogenation - Reduction of Alkenes and Alkynes with the H2PO2-NH4+*H2O/Pd-C System
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The H2PO2-*H2O/Pd-C system acts as an unusually powerful reducing agent, which is able to reduce cyclooctene to cyclooctane, Δ9,10-octalin to decalins, α- and β-pinenes to pinanes at room temperature in high yield without the formation of byproducts.This system reduces each of these compounds or partly (alkynes to alkenes), depending on the competition between the transfer hydrogenation to give alkanes and the protonolysis to give hydrogen gas on the palladium catalyst. - Key Words: Chemoselectivity/ Protonolysis/ Transfer hydrogenation/ Alkenes, reduction of/ Alkynes, reduction of
- Khai, Bui The,Arcelli, Antionio
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p. 2265 - 2268
(2007/10/02)
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- STUDIES TOWARD THE TOTAL SYNTHESIS OF POLYOXYGENATED LABDANES: PRELIMINARY APPROACHES
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Using the keto-ester 3 as a starting material, methods are developed for the successive introduction of hydroxy groups at C-6, C-7 and C-8 of a decalin system, as well as for elaboration of a C-9 pentadiene chain in preliminary approach to the total synthesis of trihydroxylabdadienes.
- Herlem, Denyse,Kervagoret, Jocelyne,Dahai, Yu,Khuong-Huu, Francoise,Kende, Andrew S.
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p. 607 - 618
(2007/10/02)
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- Colloidal palladium, easily formed in organic solvents, is a highly active and stable catalyst for selective hydrogenations and dehydrohalogenations
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Collidal Pd formed in organic solvents from Pd(hfacac)2 and silane or an Si-H- containing polymer is an active, stable and selective catalyst for hydrogenation and dehydrohalogenation.
- Fowley, Lissa A.,Michos, Demetrius,Luo, Xiao-Liang,Crabtree, Robert H.
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p. 3075 - 3078
(2007/10/02)
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- Internal Nucleophilic Termination in Biomimetic Acid Mediated polyene Cyclizations: Stereochemical and Mechanistic Implications. Synthesis of (+/-)-Ambrox and Its Diastereoisomers
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Treatment of 10 structurally releted trienols and dienols 5-8 with an excess of fluorosulfonic acid in 2-nitropropane at -90 deg C afforded, in 74-87percent yield, diastereoisomeric mixtures of the odoriferous norlabdane oxides 9-15 ((-)-9 (Ambrox) is a naturally occuring ambergris odorant).These tranformations represent examples of efficientbiomimetic acid-mediated cyclizations in which the hydroxyl group serves as the internal nucleophilic terminator.The stereochemical outcome of these kinetically controlled processes has been analysed in detail, and mechanistic hypotheses consistent with the results have been proposed.For the four acyclic trienols 5, the major reaction pathway can be rationalized by a totally synchronous process involving three internal anti additions via chair or skew-boat conformations of the nascent cyclohexane rings.An alternative explanation postulates a nonsynchronous process in which ring closure to an intermediate cyclohexyl cation is followed by rapid cyclization, directed by a strong kinetic preference for equatorial C-C and C-O bond formation.In contrast, for the monocyclic dienols 6-8 only a nonsynchronous process, involving prior protonation of the cyclohexenyl bond, is fully consisitent with the results.In the nonsynchronous processes, the orientation of the side chain vicinal to the cyclohexyl cation directs the stereochemical course of the cyclization.For the acyclic trienols, this factor is predetermined by the configuration of the C(7)=C(8) bond, whereas, for the monocyclic dienols, this orientation is determined by the stereoselective axial protonation of the cyclohexenyl bond in 6, or by the distribution of cyclohexene and cyclohexane conformers in 7 and 8, respectively.In the cases studied, it is clear that conformational inversion of the six-membered ring is slower than cyclization and thus ensures that an equatorial side chain leads to a trans A/B ring junction in the cyclization product, whereas an axial side chain affords a cis A/B ring junction.
- Snowden, Roger L.,Eichenberger, Jean-Claude,Linder, Simon M.,Sonnay, Philippe,Vial, Christian,Schulte-Elte, Karl H.
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p. 955 - 960
(2007/10/02)
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