- 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)
-
- Synthesis and mass spectra of rearrangement bio-signature metabolites of anaerobic alkane degradation via fumarate addition
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Metabolite profiling in anaerobic alkane biodegradation plays an important role in revealing activation mechanisms. Apart from alkylsuccinates, which are considered to be the usual biomarkers via fumarate addition, the downstream metabolites of C-skeleton rearrangement can also be regarded as biomarkers. However, it is difficult to detect intermediate metabolites in both environmental samples and enrichment cultures, resulting in lacking direct evidence to prove the occurrence of fumarate addition pathway. In this work, a synthetic method of rearrangement metabolites was established. Four compounds, namely, propylmalonic acid, 2-(2-methylbutyl)malonic acid, 2-(2-methylpentyl)malonic acid and 2-(2-methyloctyl)malonic acid, were synthesized and determined by four derivatization approaches. Besides, their mass spectra were obtained. Four characteristic ions were observed at m/z 133 + 14n, 160 + 28n, 173 + 28n and [M - (45 + 14n)]+ (n = 0 and 2 for ethyl and n-butyl esters, respectively). For methyl esterification, mass spectral features were m/z 132, 145 and [M - 31]+, while for silylation, fragments were m/z 73, 147, 217, 248, 261 and [M - 15]+. These data provide basis on identification of potential rearrangement metabolites in anaerobic alkane biodegradation via fumarate addition.
- Chen, Jing,Zhou, Lei,Liu, Yi-Fan,Hou, Zhao-Wei,Li, Wei,Mbadinga, Serge Maurice,Zhou, Jing,Yang, Tao,Liu, Jin-Feng,Yang, Shi-Zhong,Wu, Xiao-Lin,Gu, Ji-Dong,Mu, Bo-Zhong
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- Ir-catalyzed tandem hydroformylation-transfer hydrogenation of olefins with (trans-/cis-)formic acid as hydrogen source in presence of 1,10-phenanthroline
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The one-pot tandem hydroformylation-reduction to synthesize alcohols from olefins is in great demand but suffering from low yields, poor selectivity and harsh condition. Herein, 1,10-phenanthroline (L1) modified Ir-catalyst proved to exhibit multiple cata
- Chen, Xiao-Chao,Gao, Han,Liu, Lei,Liu, Ye,Lu, Yong,Xia, Fei,Yang, Shu-Qing
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p. 183 - 193
(2020/04/08)
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- Bimetallic Paddlewheel-type Dirhodium(II,II) Acetate and Formamidinate Complexes: Synthesis, Structure, Electrochemistry, and Hydroformylation Activity
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Classical hydroformylation catalysts use mononuclear rhodium(I) complexes as precursors; however, very few examples of bimetallic systems have been reported. Herein, we report fully substituted dirhodium(II,II) complexes (C1-C6) containing acetate and diphenylformamidinate bridging ligands (L1-L4). The structure and geometry around these paddlewheel-type, bimetallic cores were confirmed by single-crystal X-ray diffraction. The complexes C3-C6 show electrochemical redox reactions, with the expected reduction (Rh24+/3+) and two oxidation (Rh24+/5+ and Rh25+/6+) electron transfer processes. Furthermore, the bimetallic complexes were evaluated as catalyst precursors for the hydroformylation of 1-octene, with the acetate-containing complexes (C1 and C2) showing near quantitative conversion (>99%) of 1-octene, excellent activity and chemoselectivity toward aldehydes (>98%), with moderate regioselectivity toward linear products. Replacement of the acetate with diphenylformamidinate ligands (complexes C3-C6) yielded moderate-to-good chemoselectivity and regioselectivity, favoring linear aldehydes.
- Casimiro, Anna,De Doncker, Stephen,Kotze, Izak A.,Ngubane, Siyabonga,Smith, Gregory S.
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p. 12928 - 12940
(2020/09/15)
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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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- Ruthenium(II)-Catalyzed β-Methylation of Alcohols using Methanol as C1 Source
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Selective introduction of methyl branches into the carbon chains of alcohols can be achieved with low loadings of ruthenium precatalyst [RuH(CO)(BH4)(HN(C2H4PPh2)2)] (Ru-MACHO-BH) using methanol both as methylating reagent and as reaction medium. A wide range of structurally divers alcohols was β-methylated with excellent selectivity (>99 %) in fair to high yields (up to 94 %) under standard conditions, and turnover numbers up to 18,000 could be established. The overall reaction rate of the complex catalytic network appears to be governed by interconnection of the individual subcycles through availability of the reactive intermediates. The synthetic procedure opens pathways to important structural motifs following the Green Chemistry principles.
- Kaithal, Akash,Schmitz, Marc,H?lscher, Markus,Leitner, Walter
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p. 5287 - 5291
(2019/05/28)
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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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- Reductive-hydroformylation of 1-octene to nonanol using fibrous Co3O4 catalyst
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This work reports, reductive-hydroformylation of 1-octene to nonanol in the presence of fine fibrous cobalt oxide (Co3O4) nano-catalyst prepared via urea reduction method under phosphine-free and additive free condition. Co3O4 nano-catalyst was prepared by the wet chemical method and was characterized using various instrumental techniques like FEG-SEM, EDS, XRD, TPR and FTIR. The effects of various reaction parameters such as temperature, synthesis gas (CO/H2) pressure/ratio, catalyst loading, solvent and time were studied. The reaction was successfully achieved in tetrahydrofuran (THF) as the solvent medium. This reaction believed to takes place through the generation of HCox(CO)y active catalyst species. The Co3O4 nano-catalyst could be recycled up to three consecutive cycles.
- Bhagade, Sachin S.,Chaurasia, Shivkumar R.,Bhanage, Bhalchandra M.
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p. 147 - 152
(2017/09/06)
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- C -Methylation of Alcohols, Ketones, and Indoles with Methanol Using Heterogeneous Platinum Catalysts
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A versatile, selective, and recyclable heterogeneous catalytic method for the methylation of C-H bonds in alcohols, ketones, and indoles with methanol under oxidant-free conditions using a Pt-loaded carbon (Pt/C) catalyst in the presence of NaOH is reported. This catalytic system is effective for various methylation reactions: (1) the β-methylation of primary alcohols, including aryl, aliphatic, and heterocyclic alcohols, (2) the α-methylation of ketones, and (3) the selective C3-methylation of indoles. The reactions are driven by a borrowing-hydrogen mechanism. The reaction begins with the dehydrogenation of the alcohol(s) to afford aldehydes, which subsequently undergo a condensation reaction with the nucleophile (aldehyde, ketone, or indole), followed by hydrogenation of the condensation product by Pt-H species to yield the desired product. In all of the methylation reactions explored in this study, the Pt/C catalyst exhibits a significantly higher turnover number than other previously reported homogeneous catalytic systems. Moreover, it is demonstrated that the high catalytic activity of Pt can be rationalized in terms of the adsorption energy of hydrogen on the metal surface, as revealed by density functional theory calculations on different metal surfaces.
- Siddiki, S. M. A. Hakim,Touchy, Abeda S.,Jamil, Md. A. R.,Toyao, Takashi,Shimizu, Ken-Ichi
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p. 3091 - 3103
(2018/04/14)
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- Hydrofunctionalization of olefins to value-added chemicals: Via photocatalytic coupling
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A green strategy was developed for the synthesis of various value-added chemicals using methanol, acetonitrile, acetic acid, acetone and ethyl acetate as the hydrogen source by coupling them with olefins over heterogeneous photocatalysts. A radical coupling mechanism was proposed for the hydrofunctionalization of olefins with methanol to higher aliphatic alcohols over the Pt/TiO2 catalyst as the model reaction. C-H bond cleavage and C-C bond formation between photogenerated radicals and terminal olefins were accomplished in a single reaction at high efficiency. Our approach is atomically economical with high anti-Markovnikov regioselectivity and promising application potential under mild reaction conditions.
- Fan, Yonghui,Li, Shenggang,Bao, Jingxian,Shi, Lei,Yang, Yanzhang,Yu, Fei,Gao, Peng,Wang, Hui,Zhong, Liangshu,Sun, Yuhan
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supporting information
p. 3450 - 3456
(2018/08/06)
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- OPEN-FLASK HYDROBORATION AND THE USE THEREOF
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The present disclosure generally relates to a process for hydroboration of an alkene or alkyne using ammonia borane (AB). In particular, the present invention relates to hydroboration of an alkene or alkyne in the presence of air or moisture, and a clean process for facile preparation of an alcohol by oxidizing the organoborane so formed with hydrogen peroxide. The products, including aminodialkylboranes, ammonia trialkylborane complexes, as well as various alcohols so prepared, are within the scope of this disclosure.
- -
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Paragraph 0046; 0058; 0059
(2018/03/25)
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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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- A non-dissociative open-flask hydroboration with ammonia borane: Ready synthesis of ammonia-trialkylboranes and aminodialkylboranes
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Under open-flask conditions, ammonia borane hydroborates olefins in refluxing tetrahydrofuran. Unlike conventional hydroboration, the Lewis base (ammonia) is not dissociated from the boron center. Terminal alkenes selectively provide ammonia-trialkylborane complexes. On the other hand, internal alkenes afford aminodialkylboranes via a metal-free hydroboration-dehydrogenation sequence. Alkaline hydrogen peroxide oxidation of the products provides the corresponding alcohols in high yields.
- Ramachandran, P. Veeraraghavan,Drolet, Michael P.,Kulkarni, Ameya S.
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supporting information
p. 11897 - 11900
(2016/10/09)
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- Covalent grafting of cobalt carbonyl cluster on functionalized mesoporous SBA- 15 molecular sieve and its applications towards hydroformylation of 1-octene
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Cobalt carbonyl cluster was anchored through a facile route on the surface of organo-functionalized SBA-15 molecular sieve by post-synthetic approach. The successful grafting of organofunctional ligand and cobalt carbonyl cluster was evident thorough 29Si-MAS NMR, 13C-MAS NMR and FT-IR studies. The resultant cobalt clusters anchored functionalized SBA-15 material (SBA-15-RCo) showed promising catalytic activity on hydroformylation of 1-octene (97% conversion) with excellent selective towards hydroformylated products (90%).
- Ahmed, Maqsood,Sakthivel, Ayyamperumal
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- From alkenes to alcohols by cobalt-catalyzed hydroformylation-reduction
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The cobalt-catalyzed hydroformylation of alkenes in the presence of a range of novel cyclic phosphine ligands was investigated. The effect of various parameters such as solvents, additives, cobalt/phosphine ratio, CO/H2 (1:2), and nature of the alkenes was examined. The results revealed that both terminal and internal alkenes are hydroformylated in high yields to give mainly linear products at moderate temperature and syn gas pressure. The linearity ranges from 43 to 85%, with Lim-10 giving the highest proportion of linear product.
- Achonduh, George,Yang, Qian,Alper, Howard
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supporting information
p. 1241 - 1246
(2015/03/05)
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- Structure-property relationships in a series of diglycerol tetraether model lipids and their lyotropic assemblies: The effect of branching topology and chirality
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Three novel diglycerol tetraether lipids with one membrane-spanning chain have been synthesized. These lipids contain only two or four racemic methyl branches at selected positions of the hydrophobic chains in contrast to natural lipids from archaebacterial membranes with an isoprenoid substitution pattern. The insertion of the methyl moieties was realized starting from either (RS)-citronellyl bromide or the inexpensive methyl malonic acid ethyl ester. For chain elongation the Cu-catalysed Grignard coupling reaction was used. The preparation of diglycerol tetraethers was either performed by condensing suitable blocked monoglycerol diethers by Grubbs metathesis or by reaction of the transmembrane C32-chain with blocked glycerols followed by further alkylation steps. Finally, we could show that the resulting lipids can form closed lipid vesicles comparable to the optically pure counterparts. Therefore, these much simpler lipids compared to the natural lipids from archaebacterial membranes are also suitable for preparation of stable tailored liposomes. This journal is the Partner Organisations 2014.
- Markowski, Thomas,Drescher, Simon,Meister, Annette,Blume, Alfred,Dobner, Bodo
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p. 3649 - 3662
(2014/06/09)
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- Tandem hydroformylation-acetalization with a ruthenium catalyst immobilized in ionic liquids
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For the first time, a ruthenium catalyzed hydroformylation-acetalization reaction of olefins is presented. The tandem reaction proceeds well with 1,2- or 1,3-diols, trapping the intermediary formed aldehydes as cyclic acetals. In this manner the hydrogenation of the aldehydes to the corresponding alcohols usually observed with Ru catalysts is prevented. The optimized catalytic system consisting of Ru catalyst, ionic liquids, acetic acid and ammonium salt can be recycled and reused for at least two further runs. Interestingly, styrenes as substrate give preferentially terminal acetals.
- Norinder, Jakob,Rodrigues, Claudia,B?rner, Armin
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p. 139 - 143
(2014/05/20)
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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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- Efficient hydroxymethylation reactions of iodoarenes using CO and 1,3-dimethylimidazol-2-ylidene borane
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A hydroxymethylation reaction of a variety of iodoarenes proceeded effectively in the presence of CO, NHC-borane, diMeImd-BH3 (2) as a radical mediator, and a catalytic amount of AIBN. The reaction took place chemoselectively at the aryl-iodine bond but not at the aryl-bromine and aryl-chlorine bonds. A three-component coupling reaction comprising aryl iodides, CO, and electron-deficient alkenes also proceeded well to give unsymmetrical ketones in good yields. Control experiments show that 2 would act as a hydrogen donor to acyl radicals and iodinated NHC-borane as a reducing agent of aldehydes.
- Kawamoto, Takuji,Okada, Takuma,Curran, Dennis P.,Ryu, Ilhyong
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supporting information
p. 2144 - 2147
(2013/06/05)
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- From olefins to alcohols: Efficient and regioselective ruthenium-catalyzed domino hydroformylation/reduction sequence
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Exploring the alternatives: Ruthenium imidazoyl phosphine complexes catalyze the domino hydroformylation/reduction of alkenes to alcohols in good yields and with good selectivities (see scheme). Linear aliphatic alcohols are synthesized under reaction conditions typically used in industrial hydroformylations. Copyright
- Fleischer, Ivana,Dyballa, Katrin Marie,Jennerjahn, Reiko,Jackstell, Ralf,Franke, Robert,Spannenberg, Anke,Beller, Matthias
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supporting information
p. 2949 - 2953
(2013/04/10)
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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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- Formation of acetals under rhodium-catalyzed hydroformylation conditions in alcohols
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Hydroformylation of terminal alkenes in alcohol solvents leads to the selective formation of the corresponding acetals. The Xantphos ligand gave the best results as well as acetal selectivities higher than 99% and linear/branched ratios of up to 52 were obtained. The scope of the reaction was studied. Acetals were found to be unreactive under hydroaminomethylation conditions. Copyright
- Diebolt, Olivier,Cruzeuil, Clement,Mueller, Christian,Vogt, Dieter
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supporting information; experimental part
p. 670 - 677
(2012/04/23)
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- NONYL ALCOHOLS WITH A LOW DEGREE OF BRANCHING AND THEIR DERIVATIVES
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The invention relates to nonyl alcohols with a low degree of branching and derivatives produced using them. In particular the present invention relates to mixture of primary nonyl alcohols in which at least 80% of the alkyl chains are linear and at least 15% of the alkyl chains are branched at the 2-carbon position and its derivatives. The low degree of branching produces derivatives that are more elongated and less bulky that similar derivatives produced with more highly branched alcohols.
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Page/Page column 1-2
(2012/12/14)
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- Heterogenised N-heterocyclic carbene complexes: Synthesis, characterisation and application for hydroformylation and C-C bond formation reactions
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The imidazolium salts: 1-mesityl-3-(3-trimethoxysilylpropyl)imidazolium iodide and 1-tert-butyl-3-(3-trimethoxysilylpropyl)imidazolium iodide, abbreviated as (tmpMes)HI (3a) and (tmptBu)HI (3b), respectively, have been synthesised. The palladium(ii) complexes (η3-C 3H5) (tmpMes)PdCl (5a) and (η3-C 3H5)(tmptBu)PdCl (5b), rhodium(i) and iridium(i) complexes (η4-1,5-COD) (tmpMes)MCl, M = Rh (6a), Ir (7a) and (η4-1,5-COD)(tmptBu)MCl, where M = Rh (6b), Ir (7b), were synthesised by silver transmetallation reactions using the silver(i) complexes (tmpMes)AgI (4a) and (tmptBu)AgI (4b). The iridium complex 7b has been structurally characterised. The Pd(ii) and Rh(i) complexes have been immobilised by attachment to chemically modified MCM-41. The immobilised palladium(ii) materials have been tested as recyclable catalysts for Suzuki type C-C bond formation reactions in water and the immobilised rhodium(i) materials have been examined for their catalytic ability for the hydroformylation of 1-octene.
- Dastgir, Sarim,Coleman, Karl S.,Green, Malcolm L. H.
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experimental part
p. 661 - 672
(2011/02/28)
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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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- Black-light-induced radical/ionic hydroxymethylation of alkyl iodides with atmospheric co in the presence of tetrabutylammonium borohydride
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(Figure Presented) Tin-free radical/ionic hydroxymethylation of secondary and tertiary alkyl iodides proceeded efficiently in the presence of tetrabutylammonium borohydride as the hydrogen source under atmospheric pressure of CO In conjunction with photoirradiation using black light. Two possible mechanisms were proposed, both of which involve hybrid radical/ionic processes.
- Kobayashi, Shoji,Kawamoto, Takuji,Uehara, Shohei,Fukuyama, Takahide,Ryu, Ilhyong
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supporting information; scheme or table
p. 1548 - 1551
(2010/07/06)
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- Stable crystalline annulated diaminocarbenes: Coordination with rhodium(i), iridium(i) and catalytic hydroformylation studies
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Stable annulated diaminocarbene ligands 7,9-bis(2,4,6-trimethylphenyl)-6b, 9a-dihydroace naphtha[1,2-d]imidazolin-2-ylidene and 7,9-bis(2,6- diisopropylphenyl)-6b,9a-dihydroacenaphtho[1,2-d]imidazolin-2-ylidene; designated as (BIAN-SIMes, 5a,) and (BIAN-SIPr, 5b), respectively, have been prepared. The base dependent decomposition of imidazolinium salts via ring opening at the backbone was also observed. The corresponding rhodium(i) and iridum(i) complexes (η4-1,5-COD)M(BIAN-SIMes)Cl and (η4-1,5-COD)M(BIAN-SIPr)Cl; M= Rh (6a, 6b) and Ir (7a, 7b) have been synthesised by the reaction of free carbene with [M(η4-1,5- COD)(μ-Cl)]2; where M= Rh, Ir. The cationic Ir(i) complexes [(η4-1,5-COD)Ir(BIAN-SIMes)Py]BF48a and [(η4-1,5-COD)Ir(BIAN -SIPr)Py]PF68b have also been synthesised. Compounds 4b, 5a, 6a, 6b, 7b and 8b have been structurally characterised. The catalytic activities for the rhodium(i) complexes 6a and 6b were evaluated for the hydroformylation of 1-octene.
- Dastgir, Sarim,Coleman, Karl S.,Cowley, Andrew R.,Green, Malcolm L. H.
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experimental part
p. 7203 - 7214
(2010/02/15)
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- Supramolecular catalyst for aldehyde hydrogenation and tandem hydroformylation-hydrogenation
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The chemoselective reduction of aldehydes and the tandem hydroformylation-hydrogenation of terminal alkenes are possible with a supramolecular catalyst that operates by a novel mechanism involving substrate activation by hydrogen bonding and subsequent metalligand bifunctional hydrogenation (see scheme).
- Diab, Lisa,Smejkal, Tomas,Geier, Jens,Breit, Bernhard
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supporting information; experimental part
p. 8022 - 8026
(2010/02/28)
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- Palladium-Catalyzed isomerization of exo-methylenic allylic alcohols
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Treatment of allylic alcohols containing a 1,1-disubstituted alkene with a palladium catalyst and hydrogen gas (1 bar) results in facile isomerization to their corresponding trisubstituted (E)-allylic alcohols, along with small amounts of the corresponding hydrogenated products.
- Fordred, Paul S.,Niyadurupola, D.Gangani,Wisedale, Richard,Bull, Stevend
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scheme or table
p. 2310 - 2314
(2009/12/27)
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- Novel tridentate phosphines and method of forming aldehyde hydrogenation catalysts
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This invention comprises a process for hydrogenation of aldehydes to alcohols using novel homogeneous catalysts. The catalysts are generated in situ under hydrogen and carbon monoxide gases in a suitable solvent, by mixing a rhodium catalyst precursor, such as Rh(CO)2 acetoacetonate and a defined ligand.
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Page/Page column 13
(2008/06/13)
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- Chiral indenes and group-4 metallocene dichlorides containing α- And β-pinenyl-derived ligand substituants: Synthesis and catalytic applications in polymerization and carboalumination reactions
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The synthesis and characterization of chiral bis(indenyl)zirconium dichlorides containing β-pinenyl-derived ligand substituents is reported. Unbridged metallocene complexes having the ∥(1S, 2S, 5S)-6,6- dimethylbicyclo[3.1.1]hept-2-yl]methyl)dimethylsilyl substituent in both 1- and 2-positions of the indenyl moiety were prepared and isolated in moderate to low yields by reaction of the corresponding indenyllithium salts with ZrCl 4 followed by work-up and crystallization procedures. The corresponding tetrahydroindenyl complexes were obtained in excellent yields by catalytic hydrogenation of the indenyl six-membered rings. In a complementary approach, a synthetic route to α-pinenyl-substituted indenyl ligand analogues was briefly evaluated, which however, suffered from low yields. Selected ss-pinenyl-substituted indenyl complexes were scanned as catalysts for the dehydropolymerization of phenylsilane upon activation with nBuLi, for polymerization of ethylene and propylene upon activation with methylalumlnoxane (MAO) as well as for enantioselective carboalumination of 1-octene with triethyland trimethylaluminum. The bis(indenyl) complexes catalyzed the carboalumination reaction, albeit only low yields (8-16%) and low enantioselectivities (ee = 0.5-10%) were obtained. The 2-substituted bis(indenyl)zirconocene/MAO catalyst system produced atactic low-molecular weight polypropylene with low polymerization activity whereas both 1-and 2-substituted complexes showed high activities in ethylene polymerization producing polyethylenes with high molecular weights (Mw > 440000).
- Silver, Satu,Puranen, Arto,Sjoeholm, Rainer,Repo, Timo,Leino, Reko
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p. 1514 - 1529
(2007/10/03)
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- Limonene-derived phosphines in the cobalt-catalysed hydroformylation of alkenes
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Cobalt complexes involved in the hydroformylation of alkenes using (4R,S)-4,8-dimethyl-2-octadecyl-2-phosphabicyclo[3.3.1]nonane (LIM-18), which consists of a mixture of two diastereomers, have been studied. Complexation to cobalt has been used to separate or enrich the enantiomers so that spectroscopic parameters can be determined for complexes of the form [Co2(CO)8-n(LIM-18)n] (n = 1 or 2) and [Co(CO)3(LIM-18)2][Co(CO)4] containing the different diastereomers. An X-ray structure of a complex of the form [Co(CO)3(LIM-18)]2 shows it to contain the (4R) isomer, but since this was isolated from a mixed solution of diastereomers, this does not definitively identify whether the (4R) or (4S) isomer is the more strongly coordinating isomer. Experimental studies backed up with molecular modelling suggest that steric and electronic effects determine which isomer reacts preferentially in coordination, protonation and methylation reactions. The (4R) isomer is the more strongly coordinating and is metallated preferentially, although the (4S) isomer is the more basic. Variable temperature and high pressure NMR studies on the acyl complex, [Co(C(O)C5H9)(CO)3(LIM-18)], suggest that product elimination may be accompanied by isomerisation to branched acyl species. Modified cobalt catalysed hydroformylation of reactions suggest that the two diastereomers of LIM-18 do not give greatly different rates or selectivities and that a long chain secondary alkyl substituent on the LIM gives lower linear selectivity and a faster rate than LIM-18. LIM-But gives a selectivity similar to that obtained using LIM-18.
- Polas, Anastasios,Wilton-Ely, James D.E.T.,Slawin, Alexandra M.Z.,Foster, Douglas F.,Steynberg, Petrus J.,Green, Michael J.,Cole-Hamilton, David J.
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p. 4669 - 4677
(2007/10/03)
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- Potent anandamide analogs: The effect of changing the length and branching of the end pentyl chain
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To examine the effect of changing the length and branching of the end pentyl chain (C5H11) of anandamide (AN), various analogs la-h and 2a-f were synthesized from either the known aldehyde ester 6a or from the alcohol 6b and tested for their pharmacological activity. A reproducible procedure was developed for the conversion of arachidonic acid to 6a or 6b in gram quantities (overall yield 15%). The appropriate tetraene esters 7 were prepared by carrying out a Wittig reaction, between 6a and the ylide generated from the phosphonium salt of the appropriate alkyl halide or between the ylide of 6d (prepared from 6a → 6b → 6c → 6d) and the appropriate alkyl aldehydes. They were then hydrolyzed to the corresponding acids and transformed into AN analogs 1 via their acid chlorides then treated with excess ethanolamine. α-Alkylation of esters 7 gave compounds 8 which were hydrolyzed to the corresponding acids. These acids via their acid chlorides and subsequent treatment with excess fluoroethylamine gave the target compounds 2. In this way analogs 1e and 2a-c were synthesized from 6d while all the remaining analogs were prepared from 6a. In order to assess the optimal length of the alkyl terminus, analogs la-d were prepared and showed moderately high affinities(18-55 nM). However analogs la-c failed to produce significant pharmacological effects at doses up to 30 mg/kg. Analog 1d was found to be a weak partial agonist. The reason for the lack of activity in la-c is presently not clear. Like the THCs, the branching of the end pentyl chain in AN (1e-h) increased potency both in in vitro and in vive activities; the dimethylheptyl (DMH) analog 1e was the most potent in the series. Similar alkyl substitutions were carried out in the fluoro-2-methylanandamide series (2a-f), and all of these analogs had high receptor affinities (1-14 nM), the DMH analog 2a being the most potent. With a few exceptions they showed robust pharmacological effects, and AN-like profiles. It was shown that the SAR of the end pentyl chain in AN is very similar to that of THCs. However, the magnitude of enhanced potency observed when the side chain of THC was changed from straight to branched was not observed when the end chain of AN was similarly changed.
- Ryan, William J.,Kenneth Banner,Wiley, Jenny L.,Martin, Billy R.,Razdan, Raj K.
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p. 3617 - 3625
(2007/10/03)
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- Stereospecific internal almylation of terminal γ,δ-epoxy acrylates
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The alkylation of ethyl (S)- and (R)-4,5-epoxy-2-pentenoates (11) and (12), chiral terminal γ,δ-epoxy acrylates prepared from D-mannitol, by trialkylaluminum in the presence of water occurs rcgioselectively at the γ position, i.e., at the internal position, to yield a sole product respectively with net inversion of configuration. The method provides useful chiral synthons for natural product synthesis.
- Miyazawa, Masahiro,Ishibashi, Naoki,Ohnuma, Satoshi,Miyashita, Masaaki
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p. 3419 - 3422
(2007/10/03)
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- Enantioselective Transesterifications of 2-Methyl-1-alcohols Catalysed by Lipases from Pseudomonas
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Racemic β-methyl-2-thiophenepropanol was resolved (E = 200) via transesterification catalysed by lipase from Pseudomonas fluorescens using an excess of vinyl acetate in chloroform at an initial water activity: aw = 0.32.When trying to resolve rac-2-methyl-1-alkanols more modest E-values were obtained (E = 10) and were of the same order of magnitude irrespective of substrate chainlength, water activity, immobilization, acyl donor or other Pseudomonas derived lipases.However, the reaction rates are affected by variations of these parameters.Both the rates and E-values were influenced by the nature of the solvent.
- Nordin, Ove,Hedenstroem, Erik,Hoegberg, Hans-Erik
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p. 785 - 788
(2007/10/02)
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- Asymmetric synthesis of α-methyl carboxylic acid derivatives stereochemistry in acidic ring opening of epoxides
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Optically active α-methyl carboxylic acid derivatives were prepared via reaction of microbially produced epoxides with trimethylaluminum. Stereochemistry of the ring opening reaction was discussed through an MO calculation.
- Fukumasa,Furuhashi,Umezawa,Takahashi,Hirai
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p. 1059 - 1062
(2007/10/02)
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- Complex Catalysis with Technetium Compounds. Hydroformylation with Technetiumcarbonyl Catalysts
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The hydroformylation reaction of cyclohexene (1), propene (2) and 1-octene (3) was studied using Tc2(CO)10 and Tc(CO)10/P(n-C4H9)3, resp., as catalysts in solution.For comparison experiments have also been made with Mn2(CO)10, Mn2(CO)10/P(n-C4H9)3 and Re2(CO)10/P(n-C4H9)3 as catalysts for the hydroformylation of 1.There is always a competition between hydrogenation and hydroformylation.Tc2(CO)10/P(n-C4H9)3 gave the best results in activity and selectivity within the subgroup VII complexes studied, but is a rather poor catalyst compared with the cobalt or rhodium compounds.
- Kaden, L.,Lorenz, B.,Wahren, M.
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p. 407 - 412
(2007/10/02)
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- STEREOCHIMIE DE L'ALKYLATION DE CARBANIONS DERIVES D'α-AMINONITRILES
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Alkylations with 2-octyl iodide of carbanions generated in THF by LDA from α-aminonitriles or protected cyanohydrines occur with inversion of configuration and an important racemization; these reactions do not involve radical intermediates.
- Hebert, E.,Maigrot, N.,Welvart, Z.
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p. 4683 - 4686
(2007/10/02)
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- Application de la reaction de Guerbet a la methylation de n-alcanols primaires
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The Guerbet reaction is applied to the methylation of different primary n-alkanols.For 1-n-undecanol 1, selectivities of 70 to 80 percent in 2-methylation are obtained using an excess of methanol, sodium or sodium methoxide as bases and nickel or palladium as catalysts.These transformations which were extended to other primary n-alkanols are obtained at lower temperatures (160-200 deg C) than in the described hitherto conditions.Industrial applications of this Guerbet reaction could be of great interest in these simpler experimental conditions.
- Sabadie, Jean,Descotes, Gerard
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p. 253 - 256
(2007/10/02)
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- HIGHLY ACTIVE Rh6(CO)16-Diamine CATALYST SYSTEMS FOR ALCOHOL SYNTHESIS FROM OLEFINS USING CARBON MONOXIDE AND WATER
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α-olefins are carbonylated to give corresponding alcohols under mild water gas shift reaction (WGSR) conditions using Rh6(CO)16-N,N,N',N'-tetramethyl-1,3-propanediamine and 4-dimethylaminopyridine catalyst systems. α,β-Unsaturated carbonyl compounds give selectively C=C reduction products.
- Kaneda, Kiyotomi,Yasumura, Morito,Hiraki, Masahiko,Imanaka, Toshinobu,Teranishi, Shiichiro
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p. 1763 - 1766
(2007/10/02)
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- Condensation de reactifs organomagnesiens sur les bromhydrines du type R-CH(Br)-CH2OH. Influence des sels cuivreux.
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Various allylic, vinylic and arylic Grignard reagents are able to condense with 2-bromo-1-alkanols in THF.The catalytic use of copper salts diminishes side reactions but is not required.
- Bourgain-Commercon, Monique,Normant, Jean F.
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p. 289 - 294
(2007/10/02)
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