- Highly efficient NHC-iridium-catalyzed β-methylation of alcohols with methanol at low catalyst loadings
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The methylation of alcohols is of great importance since a broad number of bioactive and pharmaceutical alcohols contain methyl groups. Here, a highly efficient β-methylation of primary and secondary alcohols with methanol has been achieved by using bis-N-heterocyclic carbene iridium (bis-NHC-Ir) complexes. Broad substrate scope and up to quantitative yields were achieved at low catalyst loadings with only hydrogen and water as by-products. The protocol was readily extended to the β-alkylation of alcohols with several primary alcohols. Control experiments, along with DFT calculations and crystallographic studies, revealed that the ligand effect is critical to their excellent catalytic performance, shedding light on more challenging Guerbet reactions with simple alcohols. [Figure not available: see fulltext.].
- Lu, Zeye,Zheng, Qingshu,Zeng, Guangkuo,Kuang, Yunyan,Clark, James H.,Tu, Tao
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p. 1361 - 1366
(2021/06/30)
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- Iridium-Catalyzed Domino Hydroformylation/Hydrogenation of Olefins to Alcohols: Synergy of Two Ligands
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A novel one-pot iridium-catalyzed domino hydroxymethylation of olefins, which relies on using two different ligands at the same time, is reported. DFT computation reveals different activities for the individual hydroformylation and hydrogenation steps in the presence of mono- and bidentate ligands. Whereas bidentate ligands have higher hydrogenation activity, monodentate ligands show higher hydroformylation activity. Accordingly, a catalyst system is introduced that uses dual ligands in the whole domino process. Control experiments show that the overall selectivity is kinetically controlled. Both computation and experiment explain the function of the two optimized ligands during the domino process.
- Beller, Matthias,Huang, Weiheng,Jackstell, Ralf,Jiao, Haijun,Tian, Xinxin
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supporting information
(2022/01/13)
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- Carbon monoxide and hydrogen (syngas) as a C1-building block for selective catalytic methylation
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A catalytic reaction using syngas (CO/H2) as feedstock for the selective β-methylation of alcohols was developed whereby carbon monoxide acts as a C1 source and hydrogen gas as a reducing agent. The overall transformation occurs through an intricate network of metal-catalyzed and base-mediated reactions. The molecular complex [Mn(CO)2Br[HN(C2H4PiPr2)2]]1comprising earth-abundant manganese acts as the metal component in the catalytic system enabling the generation of formaldehyde from syngas in a synthetically useful reaction. This new syngas conversion opens pathways to install methyl branches at sp3carbon centers utilizing renewable feedstocks and energy for the synthesis of biologically active compounds, fine chemicals, and advanced biofuels.
- Kaithal, Akash,H?lscher, Markus,Leitner, Walter
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p. 976 - 982
(2021/02/06)
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- Manganese(I)-Catalyzed β-Methylation of Alcohols Using Methanol as C1 Source
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Highly selective β-methylation of alcohols was achieved using an earth-abundant first row transition metal in the air stable molecular manganese complex [Mn(CO)2Br[HN(C2H4PiPr2)2]] 1 ([HN(C2H4PiPr2)2]=MACHO-iPr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β-methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β-position, opening a pathway to “biohybrid” molecules constructed entirely from non-fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal–ligand cooperation at the Mn-pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C?C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules.
- Kaithal, Akash,van Bonn, Pit,H?lscher, Markus,Leitner, Walter
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supporting information
p. 215 - 220
(2019/12/03)
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- Diastereoselective synthesis of functionally substituted alkene dimers and oligomers, catalysed by chiral zirconocenes
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The research addresses the reaction of terminal alkenes and propene with AlR3 (R = Me, Et) in the presence of chiral Zr complexes, rac-[Y(η5-C9H10)2]ZrCl2 (Y = C2H4, SiMe2) or (NMI)2ZrCl2 (NMI- η5–neomenthylindenyl), and methylaluminoxane. The effect of reaction conditions, catalyst and trialkylalane structure on the substrate conversion and the reaction chemo- and stereoselectivity has been studied. The reaction predominantly goes via the stage of alkene methyl(ethyl)zirconation with subsequent introduction of substrate molecules into the Zr-C bond. As a result, a diastereoselective one-pot method for the synthesis of functionally substituted linear terminal alkene dimers and propene oligomers was developed.
- Kovyazin, Pavel V.,Abdullin, Il'giz N.,Parfenova, Lyudmila V.
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p. 144 - 152
(2018/11/21)
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- HYDROGENATION OF CARBONYLS WITH TETRADENTATE PNNP LIGAND RUTHENIUM COMPLEXES
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The present invention relates to catalytic hydrogenation processes, using Ru complexes with tetradentate ligands of formula L in hydrogenation processes for the reduction of ketone, aldehyde, ester or lactone into the corresponding alcohol or diol respectively. The described processes use a ruthenium complex of the formula (1) as defined below, and where the ligand (L) is defined by the Markush formula shown above.
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Page/Page column 27; 36
(2019/10/04)
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- Acid-Promoted Hydroformylative Synthesis of Alcohol with Carbon Dioxide by Heterobimetallic Ruthenium-Cobalt Catalytic System
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The acid-aided heterobimetallic ruthenium-cobalt catalytic system for the reductive hydroformylation with carbon dioxide was established. Various alkenes, including waste from biomass and petroleum industry, could be upgraded to valuable alcohols with this protocol. Acid-promoted reverse water-gas shift (RWGS), thereby accelerating the hydroformylative synthesis of alcohol. The theoretical computations revealed that acid promoted RWGS by facilitating the dehydroxylation of ruthenium hydroxy carbonyl intermediate.
- Zhang, Xuehua,Tian, Xinxin,Shen, Chaoren,Xia, Chungu,He, Lin
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p. 1986 - 1992
(2019/03/17)
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- Synthesis and Absolute Configuration of Natural 2-Pyrones
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2-Pyrones are frequently produced by microorganisms and often exhibit interesting bioactivities. Therefore, a short and easy synthetic access to these natural products is desirable. Synthetic routes to nectriapyrone, gibepyrone A, racemic gulypyrone A, (+)-germicidin C, (ent)-desoxygermicidin C and (ent)-prolipyrone A via a modular approach are presented, allowing the assignment of the absolute configurations of the latter three chiral compounds. The method failed for the synthesis of (ent)-phomapyrone B that was thus synthesized via a different route, resulting in an assignment of the absolute configuration of natural phomapyrone B.
- Burkhardt, Immo,Dickschat, Jeroen S.
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supporting information
p. 3144 - 3157
(2018/07/06)
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- Robust cobalt oxide catalysts for controllable hydrogenation of carboxylic acids to alcohols
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The selective catalytic hydrogenation of carboxylic acids is an important process for alcohol production, while efficient heterogeneous catalyst systems are still being explored. Here, we report the selective hydrogenation of carboxylic acids using earth-abundant cobalt oxides through a reaction-controlled catalysis process. The further reaction of the alcohols is completely hindered by the presence of carboxylic acids in the reaction system. The partial reduction of cobalt oxides by hydrogen at designated temperatures can dramatically enhance the catalytic activity of pristine samples. A wide range of carboxylic acids with a variety of functional groups can be converted to the corresponding alcohols at a yield level applicable to large-scale production. Cobalt monoxide was established as the preferred active phase for the selective hydrogenation of carboxylic acids.
- Song, Song,Wang, Dong,Di, Lu,Wang, Chuanming,Dai, Weili,Wu, Guangjun,Guan, Naijia,Li, Landong
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p. 250 - 257
(2018/02/20)
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- Synthesis and fungicidal activity of 2-methylalkyl isonicotinates and nicotinates
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Abstract: Homologs and analogs of 2-methylheptyl isonicotinate (new, natural antifungal and antibacterial antibiotic isolated from Streptomyces sp. 201): racemic 2-methylalkyl isonicotinates 4 and nicotinates 5 and enantiomerically enriched in the R and S isomers, 2-methylpentyl isonicotinate and nicotinate were obtained. Fungistatic activity of the compounds was evaluated. Nicotinates 5a–c show significant activity against phytopathogenic fungi: Fusarium culmorum, Phytophthora cactorum, Rhizoctonia solani. The activity of the enantiomerically enriched compounds was comparable to the activity of racemic ones. There was no significant difference in fungistatic activity between the enantiomerically enriched R and S isomers. Investigated compounds and their oxalates have proven to be active against chalkbrood disease caused by fungal species Ascosphaera apis. The activity of the nicotinates 5a and 5b and oxalates 5a–c against Ascosphaera apis was higher than the activity of oxalic acid itself. Especially high activity was shown for 2-methylbutyl nicotinate 5a and oxalate of 2-methylpentyl nicotinate 5b. Graphical abstract: [InlineMediaObject not available: see fulltext.]
- Huras, Bogumi?a,Zakrzewski, Jerzy,Krawczyk, Maria,Bombińska, Danuta,Cieniecka-Ros?onkiewicz, Anna,Michalczyk, Alicja
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p. 509 - 517
(2017/02/15)
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- Iridium Clusters Encapsulated in Carbon Nanospheres as Nanocatalysts for Methylation of (Bio)Alcohols
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C?H methylation is an attractive chemical transformation for C?C bonds construction in organic chemistry, yet efficient methylation of readily available (bio)alcohols in water using methanol as sustainable C1 feedstock is limited. Herein, iridium nanocatalysts encapsulated in yolk–shell-structured mesoporous carbon nanospheres (Ir@YSMCNs) were synthesized for this transformation. Monodispersed Ir clusters (ca. 1.0 nm) were encapsulated in situ and spatially isolated within YSMCNs by a silica-assisted sol–gel emulsion strategy. A selection of (bio)alcohols (19 examples) was selectively methylated in aqueous phase with good-to-high yields over the developed Ir@YSMCNs. The improved catalytic efficiencies in terms of activity and selectivity together with the good stability and recyclability were contributable to the ultrasmall Ir clusters with oxidation chemical state as a consequence of the confinement effect of YSMCNs with interconnected nanostructures.
- Liu, Qiang,Xu, Guoqiang,Wang, Zhendong,Liu, Xiaoran,Wang, Xicheng,Dong, Linlin,Mu, Xindong,Liu, Huizhou
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p. 4748 - 4755
(2017/12/15)
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- Catalytic Reductive Pinacol-Type Rearrangement of Unactivated 1,2-Diols through a Concerted, Stereoinvertive Mechanism
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A catalytic pinacol-type reductive rearrangement reaction of internal 1,2-diols is reported herein. Several scaffolds not usually amenable to pinacol-type reactions, such as aliphatic secondary–secondary diols, undergo the transformation well without the need for prefunctionalization. The reaction uses a simple boron catalyst and two silanes and proceeds through a concerted, stereoinvertive mechanism that enables the preparation of highly enantiomerically enriched products. Computational studies have been used to rationalize the preference for migration over direct deoxygenation.
- Drosos, Nikolaos,Cheng, Gui-Juan,Ozkal, Erhan,Cacherat, Bastien,Thiel, Walter,Morandi, Bill
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supporting information
p. 13377 - 13381
(2017/10/17)
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- Advances and Setbacks in the Total Synthesis of the Fungal Metabolite Curvicollide C: Synthesis and Elaboration of Non-Aldol Stereotriads from Gosteli-Type Allyl Vinyl Ethers
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Advances and setbacks are reported in regard to the asymmetric total synthesis of the fungal metabolite curvicollide C relying on a synthetic strategy that exploits non-aldol stereotriads as chiral building blocks. A catalytic asymmetric Gosteli-Claisen rearrangement, a two-step aldehyde-to-alkyne-homologation, and a Julia-Kocienski olefination served as key C/C-connecting transformations.
- K?rner, Marleen,Hiersemann, Martin
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p. 2466 - 2482
(2016/07/28)
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- Structure-odor correlations in homologous series of alkanethiols and attempts to predict odor thresholds by 3d-qsar studies
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Homologous series of alkane-1-thiols, alkane-2-thiols, alkane-3-thiols, 2-methylalkane-1-thiols, 2-methylalkane-3-thiols, 2-methylalkane-2-thiols, and alkane-1,??-dithiols were synthesized to study the influence of structural changes on odor qualities and odor thresholds. In particular, the odor thresholds were strongly influenced by steric effects: In all homologous series a minimum was observed for thiols with five to seven carbon atoms, whereas increasing the chain length led to an exponential increase in the odor threshold. Tertiary alkanethiols revealed clearly lower odor thresholds than found for primary or secondary thiols, whereas neither a second mercapto group in the molecule nor an additional methyl substitution lowered the threshold. To investigate the impact of the SH group, odor thresholds and odor qualities of thiols were compared to those of the corresponding alcohols and (methylthio)alkanes. Replacement of the SH group by an OH group as well as S-methylation of the thiols significantly increased the odor thresholds. By using comparative molecular field analysis, a 3D quantitative structure-activity relationship model was created, which was able to simulate the odor thresholds of alkanethiols in good agreement with the experimental results. NMR and mass spectrometric data for 46 sulfur-containing compounds are additionally supplied.
- Polster, Johannes,Schieberle, Peter
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p. 1419 - 1432
(2015/03/05)
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- A facile asymmetric synthesis of (S)-14-methyl-1-octadecene, the sex pheromone of the peach leafminer moth
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An asymmetric synthesis of 14-methyl-1-octadecene, the sex pheromone of the peach leafminer moth has been achieved. The target molecule was synthesized in six linear steps and in 30.3% overall yield from commercially available hexanoyl chloride, (S)-4-benzyloxazolidin-2-one and 1,9-nonanediol. The hexanoyl chloride was connected with (S)-4-benzyloxazolidin-2-one, and with the induction of the chiral oxazolidinone auxiliary, after chiral methylation, LAH reduction and then tosylation gave the chiral key intermediate 5 in high stereoselectivity. 1,9-Nonanediol, was selectively brominated, THP protected and subjected to Li2CuCl4-mediated C-C coupling to afford a C12 intermediate. The target molecule, (S)-14-methyl-1-octadecene, was obtained after the two parts were subjected to a second Li 2CuCl4-mediated C-C coupling. Our synthetic approach represents the first time a substrate-control asymmetric synthesis of (S)-14-methyl-1-octadecene has been reported.
- Zhang, Tao,Ma, Wei-Li,Li, Tian-Rui,Wu, Jia,Wang, Jun-Run,Du, Zhen-Ting
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p. 5201 - 5208
(2013/06/27)
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- COMPOUND HAVING BRANCHED ALKYL OR BRANCHED ALKENYL, OPTICALLY ISOTROPIC LIQUID CRYSTAL MEDIUM AND OPTICAL ELEMENT
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The first object of the invention is to provide a liquid crystal compound that is stable to heat, light and so on, and has a large optical anisotropy, a large dielectric anisotropy and a low melting point. The second object is to provide a liquid crystal medium that is stable to heat, light and so on, has a broad temperature range of a liquid crystal phase, a large optical anisotropy and a large dielectric anisotropy, and exhibits an optically isotropic liquid crystal phase. The third object is to provide a variety of optical elements containing the liquid crystal medium, which can be used in a broad temperature range and has a short response time, a high contrast and a low driving voltage. A liquid crystal compound with branched alkyl or branched alkenyl as represented by formula (1), a liquid crystal medium (a liquid crystal composition or a polymer/liquid crystal composite material) containing the liquid crystal compound, and an optical element containing the liquid crystal medium are described. In formula (1), R1 is branched alkyl of C3-20 or branched alkenyl of C3-20. The ring A1, A2, A3, A4 or A5 is 1,4-phenylene or 1,3-dioxane-2,5-diyl, for example. Z1, Z2, Z3 and Z4 are independently a single bond or C1-4 alkylene, for example. Y1 is fluorine, for example, m, n and p are independently 0 or 1, and 1≤m+n+p≤3.
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- Chemo- and regioselective homogeneous rhodium-catalyzed hydroamidomethylation of terminal alkenes to N-alkylamides
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A rhodium/xantphos homogeneous catalyst system has been developed for direct chemo- and regioselective mono-N-alkylation of primary amides with 1-alkenes and syngas through catalytic hydroamidomethylation with 1-pentene and acetamide as model substrates. For appropriate catalyst performance, it appears to be essential that catalytic amounts of a strong acid promoter, such as p-toluenesulfonic acid (HOTs), as well as larger amounts of a weakly acidic protic promoter, particularly hexafluoroisopropyl alcohol (HORF) are applied. Apart from the product N-1-hexylacetamide, the isomeric unsaturated intermediates, hexanol and higher mass byproducts, as well as the corresponding isomeric branched products, can be formed. Under optimized conditions, almost full alkene conversion can be achieved with more than 80 % selectivity to the product N-1-hexylamide. Interestingly, in the presence of a relatively high concentration of HORF, the same catalyst system shows a remarkably high selectivity for the formation of hexanol from 1-pentene with syngas, thus presenting a unique example of a selective rhodium-catalyzed hydroformylation-hydrogenation tandem reaction under mild conditions. Time-dependent product formation during hydroamidomethylation batch experiments provides evidence for aldehyde and unsaturated intermediates; this clearly indicates the three-step hydroformylation/condensation/hydrogenation reaction sequence that takes place in hydroamidomethylation. One likely role of the weakly acidic protic promoter, HORF, in combination with the strong acid HOTs, is to establish a dual-functionality rhodium catalyst system comprised of a neutral rhodium(I) hydroformylation catalyst species and a cationic rhodium(III) complex capable of selectively reducing the imide and/or ene-amide intermediates that are in a dynamic, acid-catalyzed condensation equilibrium with the aldehyde and amide in a syngas environment. Taking control: A rhodium/xantphos homogeneous catalyst system has been developed for direct chemo- and regioselective mono-N-alkylation of primary amides with 1-alkenes and syngas through the new catalytic hydroamidomethylation reaction (see picture). Copyright
- Raoufmoghaddam, Saeed,Drent, Eite,Bouwman, Elisabeth
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p. 1759 - 1773
(2013/10/21)
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- Highly enantioselective iridium-catalyzed hydrogenation of α,β-unsaturated esters
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α,β-Unsaturated esters have been employed as substrates in iridium-catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic- and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals. Asymmetric hydrogenation: A variety of α,β-unsaturated esters were hydrogenated with high enantioselectivities (see scheme). The hydrogenated products have been used in synthetic transformations as well as in formal total syntheses. Copyright
- Li, Jia-Qi,Quan, Xu,Andersson, Pher G.
-
supporting information
p. 10609 - 10616
(2012/11/07)
-
- Stereochemical investigations reveal the mechanism of the bacterial activation of n-alkanes without oxygen
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Anaerobic growth of the bacterium strain HxN1 with n-hexane gives nearly equal amounts of (2R,1 R)- and (2S,1 R)-(1-methylpentyl)succinate, which are formed by the radical addition of the hydrocarbon to fumarate (see scheme). The highly selective attack on the pro-S hydrogen atom at C2 of n-hexane is associated with inversion of the configuration at C2 during binding to fumarate and exhibits isotopic discrimination against a C-2H bond. Copyright
- Jarling, Rene,Sadeghi, Masih,Drozdowska, Marta,Lahme, Sven,Buckel, Wolfgang,Rabus, Ralf,Widdel, Friedrich,Golding, Bernard T.,Wilkes, Heinz
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supporting information; experimental part
p. 1334 - 1338
(2012/03/27)
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- Formic acid: A promising bio-renewable feedstock for fine chemicals
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In light of the growing scarcity of petroleum-based raw materials, carbon dioxide (CO2) is becoming increasing attractive as organic carbon source. In this perspective, formic acid (HCOOH) might be an interesting bio-renewable solution to store, transport, and activate carbon dioxide for the synthesis of value-added chemicals. Herein, HCOOH has been successfully used as C1 building block for the synthesis of a library of alcohols via a catalysed oxo-synthesis, under green experimental conditions. Copyright
- Mura, Manuel G.,Luca, Lidia De,Giacomelli, Giampaolo,Porcheddu, Andrea
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supporting information
p. 3180 - 3186
(2013/01/15)
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- LIGANDS FOR SELECTIVE ASYMMETRIC HYDROFORMYLATION
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In an aspect, the invention provides compounds of the formula 4: wherein the constituent variables are defined herein.
- -
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Page/Page column 19-20
(2012/02/13)
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- Convergent enantioselective syntheses of two potential C25-C40 subunits of (-)-caylobolide A
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The convergent syntheses of two possible diastereomers of the C25-C40 subunit resident in (-)-caylobolide A have been accomplished. The key reaction featured a chemoselective Ru-catalyzed cross-metathesis between a fully elaborated type I and two function
- De Joarder, Dripta,Jennings, Michael P.
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scheme or table
p. 5124 - 5127
(2011/10/19)
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- Enantioselectivity of chiral zirconocenes as catalysts in alkene hydro-, carbo- and cycloalumination reactions
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The enantioselectivity of chiral Zr catalysts L1L2ZrCl2 [L1 = L2 = 1-neomenthylindenyl (Ind*), 1; L1 = Cp, L2 = Ind* 2; L1 = Cp, L2 = 1-neomenthylindenyl-4,5,6,7-tetrahydroindenyl (Cp*) 3] in the hydro-, carbo- and cycloalumination of alkenes by organoaluminium compounds (OAC) (AlMe3, AlEt3, HAlBu2i) has been studied. It was found that OAC exhibit the most effect on the reaction chemo- and enantioselectivity. The reaction chemo- and enantioselectivity depend on the catalyst structure and reaction conditions (solvent type, catalyst concentration, temperature) as well. It is shown that the lack of asymmetric induction in the reaction of α-methylstyrene hydroalumination by HAlBu2i, catalyzed with complexes 1 or 3, is the result of the formation of Zr hydride complexes of different structures as reaction intermediates. MTPA was used as a derivatization reagent for the enantiomeric excess estimation and absolute configuration assignment of β-chiral alcohols obtained after the oxidation and hydrolysis of the reaction products. The applicability of MTPA for the assignment of the absolute configuration of the stereogenic centre in β-ethyl substituted primary alcohols and β-alkyl-1,4-butanediols is shown.
- Parfenova, Lyudmila V.,Berestova, Tatyana V.,Tyumkina, Tatyana V.,Kovyazin, Pavel V.,Khalilov, Leonard M.,Whitby, Richard J.,Dzhemilev, Usein M.
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experimental part
p. 299 - 310
(2010/06/14)
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- Modelling proposed intermediates in the hydrocarbonylation of alkenes catalysed by rhodium complexes of PBui3 and PPr i3
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In ethanol, hydrocarbonylation reactions of alkenes catalysed by triethylphosphine complexes of rhodium give alcohols as the products with low linear selectivity, whilst rhodium complexes of PPri3 or PBui3 give mainly aldehydes, again with low linear selectivity. Modelling the proposed acyl intermediates by studying [Rh(C(O)Me)(CO)m(L)4-m] (L = PPri3 or PBui3) shows that they exist as monophosphine species under the normal reaction conditions. In the absence of CO, [Rh(=C(OH)Me)(CO) L2]+ can also be formed. The implications of these NMR studies for the chemo- and regio-selectivity of the hydrocarbonylation reactions are discussed. The Royal Society of Chemistry.
- Cheliatsidou, Paraskevi,White, Daniel F. S.,Slawin, Alexandra M. Z.,Cole-Hamilton, David J.
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p. 2389 - 2394
(2008/09/20)
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- Fully reagent-controlled asymmetric synthesis of (-)-Spongidepsin via the Zr-catalyzed asymmetric carboalumination of alkenes (ZACA reaction)
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The ZACA reaction has been shown to proceed satisfactorily with internally OH-substituted 1-alkenes, provided that the OH group is unprotected and non-allylic. This reaction was used for reagent-controlled asymmetric construction of 3. Allylic alcohol was
- Zhu, Gangguo,Negishi, Ei-Ichi
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p. 2771 - 2774
(2008/02/07)
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- Enantioselective synthesis of the C8-C20 segment of curvicollide C
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The enantioselective synthesis of the C8-C20 fragment of curvicollide C has been accomplished. A catalytic asymmetric Claisen rearrangement (CAC), a diastereoselective methyl cupration of an alkynoate, and a Julia-Kocienski olefination served as key C/C-connecting transformations.
- Koerner, Marleen,Hiersemann, Martin
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p. 4979 - 4982
(2008/03/28)
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- Enantioselective syntheses of two 5, 9E diastereomers of 223V, an alkaloid from the poison frog Dendrobates pumilio
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Enantioselective syntheses of two 5, 9E diastereomers (1 and 2) of 223V (3) are described. Neither corresponded on GC-MS and GC-FTIR analyses to alkaloid 223I, previously tentatively proposed to be a 5,8-disubstituted indolizidine of the unusual 5, 9E rel
- Toyooka, Naoki,Nemoto, Hideo,Kawasaki, Masashi,Martin Garraffo,Spande, Thomas F.,Daly, John W.
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p. 1187 - 1198
(2007/10/03)
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- Synthesis, characterization, reactivity and theoretical studies of ruthenium carbonyl complexes containing ortho-substituted triphenyl phosphanes
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A series of ruthenium o-phosphane complexes was synthesized and characterized. The reactivity of the prepared complexes was studied by using them as catalysts for the hydroformylation of 1-hexene. The activities depended on the binding mode of the phosphane and on the strength of the ruthenium-phosphane interaction. Strongly coordinated chelating [2-(dimethylamino)phenyl]-(diphenyl) phosphane and [2-(methylthio)phenyl]- (diphenyl) phosphane showed poor activity, while weakly chelated [2-(methoxy)phenyl]-(diphenyl) phosphane and non-chelating phosphanes such as [2-(methyl)phenyl]-(diphenyl) phosphane or [2-(ethyl)phenyl]-(diphenyl) phosphane led to higher activities.
- Moreno, M. Andreina,Haukka, Matti,J??skel?inen, Sirpa,Vuoti, Sauli,Pursiainen, Jouni,Pakkanen, Tapani. A.
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p. 3803 - 3814
(2007/10/03)
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- Highly stereoselective alkylation of (S)-proline-based chiral auxiliaries
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Alkylation reactions with switching diastereoselectivity depending on the R1 group, resulting in a dr of up to 99:1. Alkylation of the enolates of the propanoylamides of two chiral auxiliaries (S)-(-)-2-(pyrrolidin-2-yl) propan-2-ol 1a and (S)-(-)-2-(2-methoxypropan-2-yl)pyrrolidine 1b, derived from (S)-proline, with benzyl bromide and n-butyl iodide has been studied. The auxiliaries 1a and 1b induced opposite selectivity that is (R)- and (S)-configuration, respectively, at the newly created stereogenic centre. The diastereoselectivities and conversion yields in these alkylations were moderate to excellent. When Cp2ZrCl2 was used as an enolate coordinating agent, benzylation of propanoylated 1b gave an excellent diastereomeric ratio of 99:1. The benzylated diastereomeric products from either propanoylated 1a or 1b were easily separated by liquid chromatography.
- Andersson, Fredrik,Hedenstroem, Erik
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p. 2539 - 2545
(2007/10/03)
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- Biphasic hydroformylation of 1-hexene with carbon dioxide catalyzed by ruthenium complex in ionic liquids
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Hydroformylation of 1-hexene using carbon dioxide as carbonyl carbon source attained high yield and good chemoselectivity in heptanols when a ruthenium complex was used in biphasic ionic liquid-toluene system.
- Tominaga, Ken-Ichi,Sasaki, Yoshiyuki
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- Stereoconvergent preparation of chiral vinylsilanes by cuprate substitution of α-acetoxyallylsilanes. Application to the synthesis of (S)-(+)-bishomomanicone
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Enantiomerically enriched (E)- and (Z)-configured α -acetoxyallylsilanes have been prepared starting from a chiral acylsilane bearing an asymmetric unit at the silicon portion. Treatment of these compounds with organocuprates afforded the respective vinylogous substitution products in high yields and high stereoselectivities. The transformations proceed essentially by complete anti attack of the nucleophiles to the allylic acetates and predominantly via transition states leading to the (E)-configured vinylsilane products. By the proper choice of the double bond geometry in the starting material, the configuration of the newly formed stereogenic center can be controlled. The method represents a new and flexible entry into chiral vinylsilanes that can be used for subsequent transformations. As an example, the α,β-unsaturated γ-chiral, naturally occurring ketone (S)-(+)-bishomomanicone was synthesized with this method, which represents the first synthetic access to this compound.
- Guintchin, Boris,Bienz, Stefan
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p. 7527 - 7533
(2007/10/03)
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- Regio- and stereochemical study of sex pheromone of pine sawfly; Diprion nipponica
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Regio- and stereoisomers of 1,2,ω-trimethyldecyl propionate (ω = 5-9) were prepared from stereochemically pure chiral building blocks as sex pheromone candidates of a pine sawfly; Diprion nipponica. Among the synthesized candidates, (1S,2R,8S)-1,2,8-trimethyldecyl propionate was found to be the sex pheromone of D. nipponica, based on compatibility of its GC-MS data with that of the extract of females, and its significantly high pheromone activity in a field bioassay. The field bioassay of the synthesized compounds also revealed that (1S,2R,SR)-1,2,8-trimethyldecyl propionate, (1S,2R,7S)-1,2,7-trimethyldecyl propionate, and (1S,2R,6S)-1,2,6-trimethyldecyl propionate could attract male sawflies to some extent as pheromone mimics.
- Tai, Akira,Syouno, Emi,Tanaka, Kazuki,Fujita, Morifumi,Sugimura, Takashi,Higashiura, Yasutomo,Kakizaki, Masashi,Hara, Hideho,Naito, Tikahiko
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p. 111 - 121
(2007/10/03)
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- Syntheses of female sex pheromone precursors of pine sawfly species and of some structurally related methyl-branched long-chain 2-alkanols.
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3,7-Dimethyl-2-undecanol, 3,7,9-trimethyl-2-tridecanol, and 3,7, 11-trimethyl-2-tridecanol were synthesized as racemic mixtures in moderate yields. The alcohols are known precursors of the female sex pheromones of the pine sawfly species Diprion nipponica, Macrodiprion nemoralis, and Microdiprion pallipes, respectively. Stereoisomeric mixtures of 3,8,12-trimethyl-2-tridecanol, erythro-(2R,3R, 11R/S)-3,11-dimethyl-2-tetradecanol, 3,5-dimethyl-2-tetradecanol, and 5,7-dimethyl-2-tetradecanol, structurally related to sex pheromone alcohol precursors of pine sawfly species, were also synthesized in moderate yields. The key reaction in the syntheses was the ring opening of gamma-butyrolactones by using different alkyl lithiums as nucleophiles.
- Hedenstroem, Erik,Andersson, Fredrik
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p. 1237 - 1254
(2007/10/03)
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- Do enzymes recognise remotely located stereocentres? Highly enantioselective Candida rugosa lipase-catalysed esterification of the 2- to 8-methyldecanoic acids
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Several racemic methyl decanoic acids have been synthesised and successfully resolved in esterification with 1-hexadecanol at aw=0.8 in cyclohexane using immobilised Candida rugosa lipase (CRL) as the catalyst. The enantiomeric ratios (E=2.8-68) obtained were surprisingly high even when the methyl group was as remotely located as in 8-methyldecanoic acid (E=25). Interestingly, the lipase shows enantiopreference for the S-enantiomer when the methyl group is located on even numbered carbons i.e. for the 2-,4-,6- and 8-methyldecanoic acids and to the R-enantiomer when the methyl group is located on uneven numbered carbons i.e. for the 3-,5- and 7-methyldecanoic acids.
- Hedenstroem, Erik,Nguyen, Ba-Vu,Silks III, Louis A.
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p. 835 - 844
(2007/10/03)
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- Hydrocarbonylation reactions using alkylphosphine-containing dendrimers based on a polyhedral oligosilsesquioxane core
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Radical additions of HPR2 (R = Et, Cy) onto alkenyl groups or nucleophilic substitution reactions on chlorosilanes by LiCH2PR2 (R = Me, Hex) are used to prepare first and second-generation alkylphosphine-containing dendrimers based on a polyhedral oligomeric silsesquioxane (POSS) core. The first generation dendrimers (G1) are built on 16 or 24 arms, which are chlorides, vinyl groups or allyl moieties. Hydrosilylation (chlorosilane) followed by vinylation or allylation of octavinyl-functionalised POSS gave these G1 dendrimers. Successive hydrosilylation/allylation followed by hydrosilylation/vinylation produce the framework for the second-generation dendrimer (G2). The phosphorus-containing dendrimers are used as ligands for the hydrocarbonylation of alkenes (hex-1-ene, oct-1-ene, non-1-ene, prop-1-en-2-ol) in polar solvents (ethanol or THF) using the complexes [Rh(acac)(CO)2] or [Rh2(O2CMe)4] as metal source. Linear to branched ratios up to 3:1 for the alcohol products are obtained for the diethylphosphine dendrimers. The reactions were found to proceed mainly via the formation of the corresponding aldehydes.
- Ropartz, Loic,Foster, Douglas F.,Morris, Russell E.,Slawin, Alexandra M. Z.,Cole-Hamilton, David J.
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p. 1997 - 2008
(2007/10/03)
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- Hydroformylation of alkenes in supercritical carbon dioxide catalysed by rhodium trialkylphosphine complexes
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Rhodium complexes modified by simple trialkylphosphines can be used to carry out homogeneous hydroformylation in supercritical carbon dioxide (scCO2). The catalyst derived from PEt3 is more active and slightly more selective for the linear products in scCO2 than in toluene, and under the same reaction conditions [100°C, 40 bar of CO/H2 (1:1)] P(OPri)3 is also an effective ligand giving good catalyst solubility and activity. Other ligands such as PPh3, POct3, PCy3, and P(4-C6H4But)3 are less effective because of the low solubility of their rhodium complexes in scCO2. P(4-C6H4SiM3),Ph3-n, (n = 3 or 1) and P(OPh)3 impart activity despite their complexes only being poorly soluble in scCO2. Under subcritical conditions, using PEt3 as the ligand, C7-alcohols from hydrogenation of the first formed aldehydes are the main products whilst above a total pressure of 200 bar, where the solution remains supercritical (monophasic) throughout the reaction, aldehydes are obtained with 97% selectivity. High pressure IR studies in scCO2 using PEt3 as the ligand are reported.
- Sellin, Murielle F.,Bach, Ingrid,Webster, Jeremy M.,Montilla, Francisco,Rosa, Vitor,Aviles, Teresa,Poliakoff, Martyn,Cole-Hamilton, David J.
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p. 4569 - 4576
(2007/10/03)
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- Synthesis of enantiomerically pure cis-cyclopropylboronic esters
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Highly stable, enantiomerically pure cyclopropylboronic esters are desirable building blocks for the preparation of a plethora of different cyclopropane derivatives. Whereas trans-configured compounds proved to be readily available, we herein report the f
- Luithle, Joachim E. A.,Pietruszka, J?rg
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p. 2557 - 2562
(2007/10/03)
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- Sex pheromone of the pine sawfly, Macrodiprion nemoralis. Stereoselective synthesis of the sixteen stereoisomers of 3,7,9-trimethyl-2-tridecyl acetate
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The sixteen stereoisomers of 3,7,9-trimethyl-2-tridecyl acetate (5Ac) were prepared individually, each in over 99.5% stereochemical purity. The syntheses were based on the ring opening of a pure enantiomer of cis-3,4-dimethyl-γ-butyrolactone using a pure stereoisomer of 1-lithio-2,4-dimethyloctane, the two stereogenic centres of which were introduced with high selectivity by alkylations of the amide enolates from the appropriate enantiomers of pseudoephedrine. (2S,3R,7R,9S)-3,7,9-Trimethyl-2-tridecyl acetate (SRRS-5Ac) has recently been found to be the major component of the female sex pheromone of Macrodiprion nemoralis (Hymenoptera: Diprionidae). A synthetic method for the preparation of a sixteen isomer mixture of 5Ac is also presented. This mixture has been found to be biologically active in field tests.
- Karlsson, Staffan,Hedenstroem, Erik
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p. 620 - 630
(2007/10/03)
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- Enantioselective carbometalation of cinnamyl derivatives: New access to chiral disubstituted cyclopropanes - Configurational stability of benzylic organozinc halides
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A stoichiometric or catalytic amount of (-)-sparteine can serve asa promoter for the enantioselective carbolithiation of cinnamyl derivatives by primary and secondary organolithium compounds. The enantiofacial choice of the addition reaction is dependent on the stereochemistry of the initial double bond. The resulting benzylic organolithium compounds can be derivatized to a linear phenylated chain that bears two contiguous stereogenic centers with given configurations. The use of the dimethyl acetal of the (E)-cinnamyl alcohol allows the highest enantioselective carbolithiation and by simply warming the reaction mixture to room temperature, the resulting benzylic organo-lithium intermediate undergoes a 1,3-elimination to give the chiral disubstituted cyclopropane in high enantiomeric excess (90-95% ee). Another significant finding is the observation that the Li-Zn transmetalation in a benzylic species occurs with inversion of configuration, and the corresponding acyclic benzylic zinc halides have observable configurational stability at - 30°C.
- Norsikian, Stephanie,Marek, Ilan,Klein, Sophie,Poisson, Jean F.,Normant, Jean F.
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p. 2055 - 2068
(2007/10/03)
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- Exo- and endohormones. XVII: Synthesis of racemic 5,9-dimethyl-heptadecane, the sex pheromone for the leafminer moth Leucoptera scitella
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The paper describes two practical syntheses of 5,9-dimethyl-heptadecane, the sex pheromone of the leafminer moth Leucoptera scitella (Lepidoptera, Lyonetidae). The first route (Scheme 1) involves as key reaction the coupling of 2-methyl-hexyl magnesium bromide with 3-methyl-undecanal. The second route (Scheme 3) is based on the Schlosser-Fouquet coupling reaction of 2-decyl-magnesium bromide with 4-methyl-octyl bromide.
- Ciocan-Tarta, Ilie,Oprean, Ioan,Ghizdavu, Iustin,Pojar-Fenesan, Maria
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p. 215 - 219
(2007/10/03)
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- Hydroformylation of hex-1-ene in supercritical carbon dioxide catalysed by rhodium trialkylphosphine complexes
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Triethylphosphine complexes of rhodium catalyse the hydroformylation of hex-1-ene in supercritical carbon dioxide at rates similar to those obtained in toluene, but with a slightly improved n : i ratio; using trioctylphosphine, much lower rates are observed.
- Bach, Ingrid,Cole-Hamilton, David J.
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p. 1463 - 1464
(2007/10/03)
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- Water-Soluble Tripodal Phosphane Ligands and Their Rhodium Complexes
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The synthesis of the water-soluble tripodal phosphane ligand cis,cis-1,3,5-(PPh2)3-1,3,5-xOCH3>C6H6 (x = 30-160) (5) has been achieved in a four-step reaction sequence.The alcohol Mo(CO)3 (1) is converted to the corresponding alcoholate 2, which forms the polyethylene glycol derivative 3 in a polyaddition reaction with oxirane.After methylation of the end groups of 3, the ligand 5 is obtained by a combined photochemical/oxidative demolybdenation reaction.The water-soluble tripodal phosphane 5 and the methoxymethyl functionalized tripodal ligand 6 react with Rh(PPh3)3(CO)H to form the water-soluble and water-insoluble rhodium carbonyl hydrido complexes 5a and 6a, respectively.The catalytic activity of the rhodium complex 5a in the hydroformylation of 1-hexene was found to be comparable in a single-phase system (1-hexene/methanol) with that in the biphasic system (1-hexene/water).Only traces of alcohol were found, which demonstrates that the catalyst 5a displays higher selectivity in hydroformylation than in hydrogenation. - Keywords: Tripodal P ligands; Rhodium; Water-soluble complexes; Immobilization; Biphasic hydroformylation
- Stoesel, Philipp,Mayer, Hermann A.,Auer, Friedrich
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- Total asymmetric synthesis of the potent immunosuppressive marine natural product microcolin A
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The total asymmetric synthesis of the potent immunosuppressive compound microcolin A is reported. The synthesis establishes the absolute stereochemistry of microcolin A as C-36R, C-38R, and C-4S on the basis of the diastereoselective preparation of all four possible diastereomers of the lipid region (fragment A) and diastereoselective synthesis of fragment C starting from natural L-(S)-alanine. The strategy involves a convergent assemblage of three optically pure fragments and is amenable to chemical modifications to examine structural analogs for biological study.
- Decicco, Carl P.,Grover, Paul
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p. 3534 - 3541
(2007/10/03)
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- Direct formation of alcohols by hydrocarbonylation of alkenes under mild conditions using rhodium trialkylphosphine catalysts
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The complex [RhH(PEt3)3] catalysed the hydroformylation of hex-1-ene to heptanal and 2-methylhexanal in toluene, but heptanol and 2-methylhexanol were significant products in tetrahydrofuran especially over long reaction times (16 h). In protic solvents only alcohols were produced even after short reaction times. The reactions are very rapid and also occur readily with alkenes such as hex-2-ene, propene, ethene, styrene and 3,3-dimethylbutene. The highest rates observed are for ethene (54 000 turnovers h-1) and the products in all cases are alcohols. Other phosphines containing primary alkyl groups also produced alcohols, but in contrast reactions in ethanol using rhodium complexes containing PPh3, PPh2Et, PPhEt2 or PPri3 produced significant amounts of aldehydes and/or acetals whilst Me2PCH2CH2PMe2 inhibited the reaction. The NMR studies showed that species present in equilibrium in ethanol solution are [RhH(CO)(PEt3)3], [RhH(CO)2(PEt3)2], [Rh2(CO)4(PEt3)4], [Rh2(CO)2(PEt3)6] and PEt3 but that [RhH(CO)(PEt3)3] predominates under the catalytic conditions. Reactions carried out under D2-CO in EtOH produced 90% BuCHDCH2CD2OH/D and 10% BuCHDCH2CHDOH/D but hydrogenation of heptanal under the same conditions gave a mixture of C6H13CHDOH/D (39%) and C6H13CH2OH/D (61%). These results are interpreted to indicate that the alcohols produced from hex-1-ene are primary reaction products and not produced via intermediate aldehydes. A new mechanism for this direct hydrocarbonylation is proposed in which the key acyl intermediate becomes protonated by the alcoholic solvent because of the high electron density it bears as a result of the presence of the electron-donating trialkylphosphines. Oxidative addition of H2 followed by two H-atom transfers leads directly to the alcohol. High pressure NMR studies showed that [Rh{C(O...HOEt)Et}(CO)2(PEt3)2] is present during catalytic hydrocarbonylation of ethene in ethanol. Two different cycles are proposed to explain the products obtained from the catalytic reaction of heptanal with D2-CO. Again, protonation, this time of the metal, appears to be important.
- MacDougall, Joanna K.,Simpson, Michael C.,Green, Michael J.,Cole-Hamilton, David J.
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p. 1161 - 1172
(2007/10/03)
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- Reduction of Carboxylates to Alkanols catalysed by Colletotrichum gloeosporoides
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Sodium carboxylates (C6 - C10) are effectively reduced to the corresponding alcohols by growing cultures of Colletotrichum gloeosporoides in preparatively useful way; intermediacy of the aldehydes is established by deuterium incorporation experiments; the unusual reducing capacity is proposed as an useful procedure for the preparation of alcohols of value as aroma components.
- Fronza, Giovanni,Fuganti, Claudio,Grasselli, Piero,Servi, Stefano,Zucchi, Gioia,et al.
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p. 439 - 440
(2007/10/02)
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- Comparison of Carbon-13 Nuclear Magnetic Resonance Methods for the Analysis of Multiple Partially Deuteriated Products from Catalytic Reactions: Heptan-1-ol and 2-Methylpropanol
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Products from the hydrocarbonylation of hex-1-ene or prop-2-en-1-ol using H2-CO or D2-CO in EtOH or EtOD have been analysed using 13C NMR techniques.Where there are up to four isotopomers in the products, analysis of β-shifted resonances in the 13C- NMR spectrum can give enough information for quantification of all isotopomers.Using prop-2-en-1-ol, D2-CO and EtOH, the 2-methylpropanol produced is a mixture of 16 different isotopomers.These can be individually quantified by analysis of the 13C- NMR spectrum.In particular, the resonance from the methyl C atom shows β and γ shifts, the latter being different for different types of γ-D atom.These analytical methods are shown to be superior to other possibilities including 1H NMR and mass spectrometry.
- MacDougall, Joanna K.,Simpson, Michael C.,Cole-Hamilton, David J.
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p. 3061 - 3066
(2007/10/02)
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- Pheromone Synthesis, CXXIX - Synthesis of the (5S,9S)-Isomers of 5,9-Dimethylheptadecane and 5,9-Dimethyloctadecane, the Major and the Minor Components of the Sex Pheromone of Leucoptera malifoliella Costa
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The synthesis of (5S,9S)-5,9-dimethylheptadecane (1) as well as that of (5S,9S)-5,9-dimethyloctadecane (2) has been achieved by starting from methyl (R)-3-hydroxy-2-methylpropanoate (3a) and (S)-citronellal (7). --- Key Words: Heptadecane, 5,9-dimethyl- /
- Mori, Kenji,Wu, Jiang
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p. 439 - 444
(2007/10/02)
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- Asymmetric epoxidation of fluorinated allylic alcohols
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The asymmetric epoxidation of an α,β-difluoro primary allylic alcohol, and of two α-fluoro secondary allylic alcohols follows the pattern known with non fluorinated analogs. The fluoro epoxides thus formed can be transformed into chiral α-ketols and into an α-fluoroacid.
- Gosmini,Dubuffet,Sauvetre,Normant
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p. 223 - 230
(2007/10/02)
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