- Structural characterisation of solution species implicated in the palladium-catalysed Heck reaction by Pd K-edge X-ray absorption spectroscopy: Palladium acetate as a catalyst precursor
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Energy dispersive EXAFS (EDE), Quick EXAFS (QEXAFS), 13C NMR and X-ray crystallography have been used to probe the co-ordination sphere of palladium in the course of the phosphine free Heck reaction. [Pd2I6][NBu3H]2 has been isolated from the precatalytic solution and its crystal structure determined. EDE and QEXAFS spectra of the complexes Pd(OAc)2, Pd(PPh3)4 and [Pd2I6][NEt3H]2 illustrated the value of the technique in structure elucidation. EXAFS of the precatalytic solution detects [Pd2I6]2- and no co-ordinated carbon. EXAFS of the catalytic solution shows a first co-ordination sphere of 2 carbon atoms and a second of 2-2.5 iodines. A scheme involving an equilibrium between the oxidative addition product and the olefin co-ordination species, has been proposed to explain these results.
- Evans, John,O'Neill, Lynn,Kambhampati, Vijaya L.,Rayner, Graham,Turin, Sandra,Genge, Anthony,Dent, Andrew J.,Neisius, Thomas
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Read Online
- A BINOL-phosphoric acid and metalloporphyrin derived chiral covalent organic framework for enantioselective α-benzylation of aldehydes
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The catalytic asymmetric α-benzylation of aldehydes represents a highly valuable reaction for organic synthesis. For example, the generated α-heteroarylmethyl aldehydes, such as (R)-2-methyl-3-(pyridin-4-yl)propanal ((R)-MPP), are an important class of synthons to access bioactive drugs and natural products. We report herein a new and facile synthetic approach for the asymmetric intermolecular α-benzylation of aldehydes with less sterically hindered alkyl halides using a multifunctional chiral covalent framework (CCOF) catalyst in a heterogeneous way. The integration of chiral BINOL-phosphoric acid and Cu(ii)-porphyrin modules into a single COF framework endows the obtained (R)-CuTAPBP-COF with concomitant Br?nsted and Lewis acidic sites, robust chiral confinement space, and visible-light induced photothermal conversion. These features allow it to highly promote the intermolecular asymmetric α-benzylation of aldehydes via visible-light induced photothermal conversion. Notably, this light-induced thermally driven reaction can effectively proceed under natural sunlight irradiation. In addition, this reaction can be easily extended to a gram-scale level, and its generality is ascertained by asymmetric α-benzylation reactions on various substituted aldehydes and alkyl bromides.
- Chen, Gong-Jun,Dong, Yu-Bin,Ma, Hui-Chao,Sun, Ya-Nan
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p. 1906 - 1911
(2022/02/25)
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- A robust and stereocomplementary panel of ene-reductase variants for gram-scale asymmetric hydrogenation
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We report an engineered panel of ene-reductases (ERs) from Thermus scotoductus SA-01 (TsER) that combines control over facial selectivity in the reduction of electron deficient C[dbnd]C double bonds with thermostability (up to 70 °C), organic solvent tolerance (up to 40 % v/v) and a broad substrate scope (23 compounds, three new to literature). Substrate acceptance and facial selectivity of 3-methylcyclohexenone was rationalized by crystallisation of TsER C25D/I67T and in silico docking. The TsER variant panel shows excellent enantiomeric excess (ee) and yields during bi-phasic preparative scale synthesis, with isolated yield of up to 93 % for 2R,5S-dihydrocarvone (3.6 g). Turnover frequencies (TOF) of approximately 40 000 h?1 were achieved, which are comparable to rates in hetero- and homogeneous metal catalysed hydrogenations. Preliminary batch reactions also demonstrated the reusability of the reaction system by consecutively removing the organic phase (n-pentane) for product removal and replacing with fresh substrate. Four consecutive batches yielded ca. 27 g L?1 R-levodione from a 45 mL aqueous reaction, containing less than 17 mg (10 μM) enzyme and the reaction only stopping because of acidification. The TsER variant panel provides a robust, highly active and stereocomplementary base for further exploitation as a tool in preparative organic synthesis.
- Nett, Nathalie,Duewel, Sabine,Schmermund, Luca,Benary, Gerrit E.,Ranaghan, Kara,Mulholland, Adrian,Opperman, Diederik J.,Hoebenreich, Sabrina
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- Your mother was right, washing matters: An alkyne-analog of ibuprofen reveals unwanted reactivity of aromatic compounds with proteins during copper-catalyzed click chemistry
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Bioorthogonal chemistry, in particular the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), has enabled the robust identification of covalent protein targets of probes and drugs. Ibuprofen is commonly used pain and fever reducer and is sold as an enantiomeric racemate. Interestingly, the stereoisomers can be enzymatically converted through an ibuprofen-CoA thioester intermediate, which might non-specifically react with protein nucleophiles. Here, we use an alkyne-analog of ibuprofen to make two discoveries. First, we find that ibuprofen likely does not result in notable chemical labeling of proteins. However, we secondly find that aromatic compounds can react with proteins during the CuAAC reaction unless they are appropriately washed out of the mixture. This second discovery of false positive labeling has important technical implications for the application of this approach.
- Cutolo, Giuliano,Pratt, Matthew R.,Shankar, Sahiti N.
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- Organic Ligand-Free Hydroformylation with Rh Particles as Catalyst?
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An efficient and organic ligand-free heterogeneous catalytic system for hydroformylation of olefins is highly desirable for both academy and industry. In this study, simple Rh black was employed as a heterogeneous catalyst for hydroformylation of olefins in the absence of organic ligand. The Rh black catalyst showed good catalytic activity for a broad substrate scope including the aliphatic and aromatic olefins, affording the desired aldehydes in good yields. Taking the hydroformylation of ethylene as an example, 86% yield of propanal and TOF of 200 h–1 were obtained, which was superior to the reported homogeneous catalytic systems. In addition, the catalyst could be reused five times without loss of activity under identical reaction conditions, and the Rh leaching was negligible after each cycle.
- Liu, Shujuan,Dai, Xingchao,Wang, Hongli,Wang, Xinzhi,Shi, Feng
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p. 139 - 143
(2020/01/03)
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- Binuclear Pd(I)-Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes
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Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>107 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh- or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)-Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.
- Zhang, Yang,Torker, Sebastian,Sigrist, Michel,Bregovi?, Nikola,Dydio, Pawe?
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supporting information
p. 18251 - 18265
(2020/11/02)
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- High iso Aldehyde Selectivity in the Hydroformylation of Short-Chain Alkenes
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The hydroformylation of propene to give predominantly iso-butanal has been achieved; class-leading selectivity is possible even at higher temperatures that deliver fast conversion. Racemic rhodium complexes of bidentate phospholane phosphites derived from tropos-biphenols and unusual solvent systems are the key to the selectivity observed.
- Iu, Leo,Fuentes, José A.,Janka, Mesfin E.,Fontenot, Kevin J.,Clarke, Matthew L.
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supporting information
p. 2120 - 2124
(2019/01/25)
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- TETRAHYDRO-IMIDAZO QUINOLINE COMPOSITIONS AS CBP/P300 INHIBITORS
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The present disclosure is directed to inhibitors of the CBP/p300 family of bromodomains. The compounds can be useful in the treatment of disease or disorders associated with the inhibition of the CBP/p300 family of bromodomains. For instance, the disclosure is concerned with compounds and compositions for inhibition of the CBP/p300 family of bromodomains, methods of treating, preventing, or ameliorating diseases or disorders associated with the inhibition of CBP/p300 family of bromodomains, and methods of synthesis of these compounds.
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Paragraph 00119
(2019/04/11)
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- CO-Free Enantioselective Hydroformylation of Functionalised Alkenes: Using a Dual Catalyst System to Give Improved Selectivity and Yield
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The scope of carbon monoxide-free Asymmetric Transfer HydroFormylation (ATHF) procedures using a highly active single catalyst system derived from 1,2-bis-((2,5)-diphenylphospholano)ethane as chiral ligand has been studied. This reveals some highly successful reactions, but also significant limitations. The development of a new protocol in which a catalyst for formaldehyde decomposition to CO and H2 is combined with the catalyst of choice for the subsequent asymmetric hydroformylation is described. This enables ATHF reactions that were problematic to be significantly improved. The new method has been used in the synthesis of several key precursors to biologically active molecules. (Figure presented.).
- Pittaway, Rachael,Dingwall, Paul,Fuentes, José. A.,Clarke, Matthew. L.
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supporting information
p. 4334 - 4341
(2019/08/21)
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- Carbonylative Transformation of Allylarenes with CO Surrogates: Tunable Synthesis of 4-Arylbutanoic Acids, 2-Arylbutanoic Acids, and 4-Arylbutanals
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In this Communication, procedures for the selective synthesis of 4-arylbutanoic acids, 2-arylbutanoic acids, and 4-arylbutanals from the same allylbenzenes have been developed. With formic acid or TFBen as the CO surrogate, reactions proceed selectively and effectively under carbon monoxide gas-free conditions.
- Wu, Fu-Peng,Li, Da,Peng, Jin-Bao,Wu, Xiao-Feng
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supporting information
p. 5699 - 5703
(2019/08/01)
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- Iron Catalyzed Hydroformylation of Alkenes under Mild Conditions: Evidence of an Fe(II) Catalyzed Process
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Earth abundant, first row transition metals offer a cheap and sustainable alternative to the rare and precious metals. However, utilization of first row metals in catalysis requires harsh reaction conditions, suffers from limited activity, and fails to tolerate functional groups. Reported here is a highly efficient iron catalyzed hydroformylation of alkenes under mild conditions. This protocol operates at 10-30 bar syngas pressure below 100 °C, utilizes readily available ligands, and applies to an array of olefins. Thus, the iron precursor [HFe(CO)4]-[Ph3PNPPh3]+ (1) in the presence of triphenyl phosphine catalyzes the hydroformylation of 1-hexene (S2), 1-octene (S1), 1-decene (S3), 1-dodecene (S4), 1-octadecene (S5), trimethoxy(vinyl)silane (S6), trimethyl(vinyl)silane (S7), cardanol (S8), 2,3-dihydrofuran (S9), allyl malonic acid (S10), styrene (S11), 4-methylstyrene (S12), 4-iBu-styrene (S13), 4-tBu-styrene (S14), 4-methoxy styrene (S15), 4-acetoxy styrene (S16), 4-bromo styrene (S17), 4-chloro styrene (S18), 4-vinylbenzonitrile (S19), 4-vinylbenzoic acid (S20), and allyl benzene (S21) to corresponding aldehydes in good to excellent yields. Both electron donating and electron withdrawing substituents could be tolerated and excellent conversions were obtained for S11-S20. Remarkably, the addition of 1 mol % acetic acid promotes the reaction to completion within 16-24 h. Detailed mechanistic investigations revealed in situ formation of an iron-dihydride complex [H2Fe(CO)2(PPh3)2] (A) as an active catalytic species. This finding was further supported by cyclic voltammetry investigations and intermediacy of an Fe(0)-Fe(II) species was established. Combined experimental and computational investigations support the existence of an iron-dihydride as the catalyst resting state, which then follows a Fe(II) based catalytic cycle to produce aldehyde.
- Pandey, Swechchha,Raj, K. Vipin,Shinde, Dinesh R.,Vanka, Kumar,Kashyap, Varchaswal,Kurungot, Sreekumar,Vinod,Chikkali, Samir H.
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supporting information
p. 4430 - 4439
(2018/04/05)
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- Branched-Selective Hydroformylation of Nonactivated Olefins Using an N-Triphos/Rh Catalyst
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We report a catalytic system comprised of nitrogen-centered di- or triphosphine ligands in conjunction with rhodium that is capable of delivering branched aldehydes from terminal olefin substrates which commonly give more linear aldehydes than branched. The incorporation of an apical nitrogen atom into the ligand backbone dramatically improves the reaction rate. Mechanistic and labeling studies suggest the unusual selectivity is due to the irreversible trapping of the Rh-alkyl species along the branched pathway, in comparison to the more reversible linear pathway. A precatalytic equilibrium mixture of rhodium species was observed by high-pressure in situ NMR spectroscopy, suggesting this equilibrium is the catalytic resting state.
- Phanopoulos, Andreas,Nozaki, Kyoko
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p. 5799 - 5809
(2018/05/29)
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- Enantio- A nd regioselective: Ene-reductions using F420H2-dependent enzymes
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In the past decade it has become clear that many microbes harbor enzymes that employ an unusual flavin cofactor, the F420 deazaflavin cofactor. Herein we show that F420-dependent reductases (FDRs) can successfully perform enantio-, regio- A nd chemoselective ene-reductions. For the first time, we have demonstrated that F420H2-driven reductases can be used as biocatalysts for the reduction of α,β-unsaturated ketones and aldehydes with good conversions (>99%) and excellent regioselectivities and enantiomeric excesses (>99% ee). Noteworthily, FDRs typically display an opposite enantioselectivity when compared to the well established FMN-dependent Old Yellow Enzymes (OYEs).
- Mathew, Sam,Trajkovic, Milos,Kumar, Hemant,Nguyen, Quoc-Thai,Fraaije, Marco W.
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supporting information
p. 11208 - 11211
(2018/10/15)
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- Dess-Martin periodinane oxidative rearrangement for preparation of α-keto thioesters
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A Dess-Martin Periodinane (DMP) mediated oxidative rearrangement reaction was uncovered. The reaction proceeds via oxidation of a β-hydroxy thioester to a β-keto thioester, followed by an α-hydroxylation and then further oxidation to form a vicinal thioester tricarbonyl. This product then rearranges, extruding CO2, to form an α-keto product. The mechanism of the rearrangement was elucidated using 13C labelling and analysis of the intermediates as well as the products of the reaction. This efficient process allows for easy preparation of α-keto thioesters which are potential intermediates in the synthesis of pharmaceutically important heterocyclic scaffolds such as quinoxalinones.
- Sanichar, Randy,Carroll, Ciaran,Kimmis, Ryan,Reiz, Bela,Vederas, John C.
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p. 593 - 597
(2018/02/09)
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- Synthesis of Alkyl Citrates (-)-CJ-13,981, (-)-CJ-13,982, and (-)-L-731,120 via a Cyclobutene Diester
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An efficient and step-economic new approach to alkyl citrate natural products from a cyclobutene diester is presented. The key sequence involves a formal [2 + 2]-cycloaddition of a silylketene acetal with dimethylacetylene dicarboxylate to provide the cyclobutene diester 14 with 4.5:1 stereoselectivity. Exposure of diester 14 in acidic methanol effected a hydrolysis, intramolecular oxy-Michael reaction, and cyclobutanone methanolysis cascade to give the triester 15. Iodination and elimination then afforded a key alkyl citrate alkene intermediate, which was converted into the natural products (-)-CJ-13,982 (1), (-)-CJ-13,981 (2), and (-)-L-731,120 (3) via a cross-metathesis and subsequent reduction.
- Atkin, Liselle,Chen, Zongjia,Robertson, Angus,Sturgess, Dayna,White, Jonathan M.,Rizzacasa, Mark A.
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supporting information
p. 4255 - 4258
(2018/07/29)
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- Rhodium/Phosphine catalysed selective hydroformylation of biorenewable olefins
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This work reports rhodium catalyzed selective hydroformylation of natural olefins like eugenol, estragole, anethole, prenol and isoprenol using biphenyl based Buchwald phosphine ligands (S-Phos (L1), t-Bu XPhos (L2), Ru-Phos (L3), Johnphos (L4) and DavePhos (L5). Ru-Phos (L3) ligand exhibited high impact on the hydroformylation of eugenol providing high selectivity (90%) of linear aldehyde as major product. In addition, internal natural olefins like anethole and prenol provided moderate to high selectivity (65% and 85% respectively) of branched aldehydes as a major products. The various reaction parameters such as influence of ligands, P/Rh ratio, syngas pressure, temperature, time and solvents have been studied. A high activity and selectivity gained on the way to the linear aldehydes it may be due to the bulky, steric cyclohexyl and isopropoxy groups present in L3 phosphine ligand. Moreover, this catalytic system was smoothly converting natural olefins into corresponding linear and branched aldehydes with higher selectivity under the mild reaction conditions.
- Jagtap, Samadhan A.,Bhanage, Bhalchandra M.
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- A synthetic route to 4-alkyl-α-methylhydrocinnamylaldehydes
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The 4-Alkyl-α-methylhydrocinnamylaldehydes (alkyl-isopropyl, isobutyl, methyl) are frequently used fragrances with desired floral (lilac, cyclamen, lily-of-the-valley) scent. These substances are valued for their good stability in basic solution and, therefore, are frequently used in soaps, detergents, or shampoos. These substances are synthesized by a two-step synthesis involving base catalyzed aldol condensation of 4-alkylbenzaldehyde with propanal followed by selective hydrogenation of the C=C bond. In aldol condensation, selectivity is decreased by formation of undesired products of propanal autocondensation 2-methylpent-2-enal. In this work the reaction conditions for homogenous catalyzed aldol condensation of 4-isobutylbenzadehyde with propanal were tested (catalyst type and amount, molar ratio of reactants, solvent type). Reaction conditions giving the best results (92% conversion, 79% selectivity) were adapted to other 4-alkyl-α-methylcinnamylaldehydes preparation with similar results. In the second step—hydrogenation of aldol product different types of catalyst (nickel, cobalt, palladium or Adkins catalyst), and also different solvents, were tested. Hydrogenation conditions leading to the highest yield (72% selectivity at 95% conversion) were adapted to other 4-alkylhydrocinnamyladehydes with similar results.
- Vrbková, Eva,Vysko?ilová, Eli?ka,Rott, Martin,Zapletal, Martin,?erveny, Libor
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p. 2603 - 2613
(2017/03/22)
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- Understanding a Hydroformylation Catalyst that Produces Branched Aldehydes from Alkyl Alkenes
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This paper reports experimental and computational studies on the mechanism of a rhodium-catalyzed hydroformylation that is selective for branched aldehyde products from unbiased alkene substrates. This highly unusual selectivity relies on a phospholane-phosphite ligand prosaically called BOBPHOS. Kinetic studies using in situ high pressure IR (HPIR) and the reaction progress kinetic analysis methodology suggested two steps in the catalytic cycle were involved as turnover determining. Negative order in CO and positive orders in alkene and H2 were found and the effect of hydrogen and carbon monoxide partial pressures on selectivity were measured. Labeling studies found rhodium hydride addition to the alkene to be largely irreversible. Detailed spectroscopic HPIR and NMR characterization of activated rhodium-hydrido dicarbonyl species were carried out. In the absence of H2, reaction of the rhodium-hydrido dicarbonyl with allylbenzene allowed further detailed spectroscopic characterization of four- and five-coordinate rhodium-acyl species. Under single-turnover conditions, the ratios of branched to linear acyl species were preserved in the final ratios of aldehyde products. Theoretical investigations uncovered unexpected stabilizing CH-π interactions between the ligand and substrate which influenced the high branched selectivity by causing potentially low energy pathways to become unproductive. Energy span and degree of TOF control analysis strongly support experimental observations and mechanistic rationale. A three-dimensional quadrant model was built to represent the structural origins of regio- and enantioselectivity.
- Dingwall, Paul,Fuentes, José A.,Crawford, L. Ellis,Slawin, Alexandra M. Z.,Bühl, Michael,Clarke, Matthew L.
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p. 15921 - 15932
(2017/11/14)
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- Rh/Cu2O nanoparticles: Synthesis, characterization and catalytic application as a heterogeneous catalyst in hydroformylation reaction
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In this work, we report a rapid protocol for the synthesis of Rh/Cu2O nanoparticles (Rh/Cu2O NPs) in aqueous medium using microwave route. The microwave energy acts as driving force in synthesis which makes the process economical. The obtained nanoparticles were characterized with the help of FEG-SEM, TEM, HRTEM, EDS, XRD, FT-IR and ICP-AES techniques. The prepared Rh/Cu2O nanoparticles gave 100% yield of uniform spherical morphology. This is a simple, inexpensive and time saving protocol for synthesis of Rh/Cu2O nanoparticles than conventional methods. Furthermore, we showed the catalytic application of Rh/Cu2O nanoparticles in hydroformylation reaction for the conversion of 1-hexene to 1-hexanal at mild reaction conditions such as Rh/Cu2O NPs (10 mg), 35 bar pressure of H2/CO at 360 K. The reaction provides 99% conversion and high selectivity (>90%) toward aldehydes with branched aldehyde is a major product. Notably the reaction does not require the any phosphine ligand source, low catalyst loading, low temperature with major advantage of catalyst recyclability.
- Jagtap, Samadhan A.,Bhosale, Manohar A.,Sasaki, Takehiko,Bhanage, Bhalchandra M.
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p. 162 - 168
(2016/12/06)
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- Enhanced Ene-Reductase Activity through Alteration of Artificial Nicotinamide Cofactor Substituents
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The reduction of activated C=C double bonds is an important reaction in synthetic chemistry owing to the potential formation of up to two new stereogenic centers. Artificial nicotinamide cofactors were recently presented as alternative suppliers of hydride equivalents needed for alkene reduction. To study the effect of cofactors on the reduction of activated alkenes, a set of N-substituted synthetic nicotinamide cofactors with differing oxidation potentials were synthesized and their electrochemical and kinetic behavior was studied. The effects of the synthetic cofactors on enzyme activity of four ene reductases are outlined in this study, where the cofactor mimic with an N-substituted 4-hydroxy-phenyl residue led to a sixfold higher vmax relative to the natural cofactor NADH. Artificial nicotinamide cofactor substituents: A set of N-substituted synthetic nicotinamide cofactors with differing oxidation potentials were synthesized and their electrochemical and kinetic behavior was studied. The effects of the synthesized cofactors on the enzyme activity of four ene reductases are outlined. The cofactor mimic with an N-substituted 4-hydroxy-phenyl residue led to a sixfold higher vmax relative to the natural cofactor NADH.
- L?w, Sebastian A.,L?w, Isabell M.,Weissenborn, Martin J.,Hauer, Bernhard
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p. 911 - 915
(2016/03/15)
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- Synergistic Effect of Tungsten Nitride and Palladium for the Selective Hydrogenation of Cinnamaldehyde at the C=C bond
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Herein, a series of catalysts made of Pd-WN on various supports was synthesized by modifying supports with small-size WN NPs firstly and loading Pd subsequently. Their catalytic performances were evaluated for selective hydrogenation of cinnamaldehyde (CAL) to hydrocinnamaldehyde (HALD). Interestingly, it was found the synergistic effect between Pd and WN can improve conversion and selectivity of CAL to HALD. Among these catalysts, Pd-WN/SBA-15 shows best performance with highest conversion (99 %) and selectivity to HALD (97 %), which is superior to commercial 5 % Pd/C catalyst. The hydrogenation kinetics of Pd-WN/SBA-15 has been adequately represented by a standard pseudo-first-order approximation, and it discloses that the existence of WN can effectively decrease the activation energy (23.2 kJ mol-1). The synergistic effect of Pd and WN results in enriching the electron density of Pd, increasing the ratio of surface Pd0 and decreasing the size of Pd on the Pd-WN/SBA-15 catalyst.
- Wang, Dong,Zhu, Yujun,Tian, Chungui,Wang, Lei,Zhou, Wei,Dong, Yongli,Yan, Haijing,Fu, Honggang
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p. 1718 - 1726
(2016/05/19)
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- Light-driven biocatalytic reduction of α,β-unsaturated compounds by ene reductases employing transition metal complexes as photosensitizers
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Efficient and cost effective nicotinamide cofactor regeneration is essential for industrial-scale bio-hydrogenations employing flavin-containing biocatalysts such as the Old Yellow Enzymes. A direct flavin regeneration system using visible light to initiate a photoredox cycle and drive biocatalysis is described, and shown to be effective in driving biocatalytic activated alkene reduction. Using Ru(ii) or Ir(iii) complexes as photosensitizers, coupled with an electron transfer mediator (methyl viologen) and sacrificial electron donor (triethanolamine) drives catalytic turnover of two Old Yellow Enzymes with multiple oxidative substrates. Therefore, there is great potential in the development of light-driven biocatalytic systems, providing an alternative to the reliance on enzyme-based cofactor regeneration systems.
- Peers, Martyn K.,Toogood, Helen S.,Heyes, Derren J.,Mansell, David,Coe, Benjamin J.,Scrutton, Nigel S.
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p. 169 - 177
(2015/12/31)
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- Cell-free protein engineering of Old Yellow Enzyme 1 from Saccharomyces pastorianus
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In protein engineering, cell-free transcription/translation of linear mutagenic DNA templates can tremendously accelerate and simplify the screening of enzyme variants. Using the RApid Parallel Protein EvaluatoR (RAPPER) protocol, we have evaluated the impact of amino acid substitutions and loop truncations on substrate specificity and stereoselectivity of Old Yellow Enzyme 1 from Saccharomyces pastorianus. Our study demonstrates the benefit of systematically assessing amino acid variations including substrate profiling to explore sequence-function space.
- Quertinmont, Leann T.,Lutz, Stefan
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p. 7282 - 7287
(2016/10/29)
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- Particle size effects in the selective hydrogenation of cinnamaldehyde over supported palladium catalysts
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This work investigated the catalytic performance of palladium catalysts in the selective hydrogenation of α,β-unsaturated aldehydes, and especially the effect of Pd particle size on the hydrogenation of cinnamaldehyde (CAL). An unsupported nanosized Pd catalyst and a series of supported Pd catalysts using supports of activated carbon, SiO2, TiO2, γ-Al2O3, SiC, and graphene oxide were prepared and evaluated in the selective hydrogenation of CAL. Varied sizes of Pd particles could be obtained directly by using different Pd precursors and indirectly by introducing an inactive Ag metal over a γ-Al2O3 supported palladium catalyst. Over a reducible TiO2 support, the Pd particle size can also be controlled indirectly by the effect of strong metal-support interaction (SMSI). Combined with their TEM observations and catalytic tests, density functional theory (DFT) calculations have confirmed that smaller Pd particles favored CC-centered adsorption of CAL leading to a higher selectivity to hydrogenation of the CC bond, forming hydrocinnamaldehyde (HCAL), while on larger ones, the CC-centered adsorption would be partly substituted by CO-centered adsorption resulting in a lowered selectivity to HCAL but an increased selectivity to CO bond hydrogenation, forming hydrocinnamyl alcohol (HCOL). It is clarified that the size dependence of the catalytic selectivity originates from the strong dependence of CC/CO-centered adsorption on Pd particle size. Finally, tests using solvents with different Pd-solvent interactions and α,β-unsaturated aldehydes with remarkable steric effect variations were applied to further regulate the adsorption between palladium and substrate to alter the catalytic activity and selectivity.
- Jiang, Feng,Cai, Jian,Liu, Bing,Xu, Yuebing,Liu, Xiaohao
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p. 75541 - 75551
(2016/08/24)
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- Palladium on Charcoal Catalyzed 3,4-Hydroperoxidation of α-Substituted Enals with Triethylsilane and Water
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Aldehyde α-hydroperoxides can be accessed from α-substituted acroleins with triethylsilane and water under Pd/C catalysis and aerobic conditions. The reaction is composed of a Pd/C-catalyzed conjugate reduction step and a hydroperoxidation step. The hydroperoxidation takes place via autoxidation of sufficiently stable enols formed in situ by transfer hydrogenation. Upon reduction, 2,2-disubstituted 1,2-diols are obtained directly from aldehydes.
- Tuokko, Sakari,Pihko, Petri M.
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supporting information
p. 1649 - 1652
(2016/07/06)
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- General, Simple, and Chemoselective Catalysts for the Isomerization of Allylic Alcohols: The Importance of the Halide Ligand
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Remarkably simple IrIIIcatalysts enable the isomerization of primary and sec-allylic alcohols under very mild reaction conditions. X-ray absorption spectroscopy (XAS) and mass spectrometry (MS) studies indicate that the catalysts, with the general formula [Cp*IrIII], require a halide ligand for catalytic activity, but no additives or additional ligands are needed.
- Erbing, Elis,Vázquez-Romero, Ana,Bermejo Gómez, Antonio,Platero-Prats, Ana E.,Carson, Fabian,Zou, Xiaodong,Tolstoy, P?ivi,Martín-Matute, Belén
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p. 15659 - 15663
(2016/10/25)
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- Catalytic C-H Arylation of Aliphatic Aldehydes Enabled by a Transient Ligand
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The direct arylation of aliphatic aldehydes has been established via Pd-catalyzed sp3 C-H bond functionalization in the presence of 3-aminopropanoic acids as transient directing groups. The reaction showed excellent functional group compatibility and chemoselectivity in which a predominant preference for functionalizing unactivated β-C-H bonds of methyl groups over others was achieved. In addition, C-H bonds of unactivated secondary sp3 carbons can also be functionalized. The extreme popularity and importance of aliphatic aldehydes would result in broad applications of this novel method in organic chemistry and medicinal sciences.
- Yang, Ke,Li, Qun,Liu, Yongbing,Li, Guigen,Ge, Haibo
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supporting information
p. 12775 - 12778
(2016/10/13)
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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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- Systematic methodology for the development of biocatalytic hydrogen-borrowing cascades: Application to the synthesis of chiral α-substituted carboxylic acids from α-substituted α,β-unsaturated aldehydes
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Ene-reductases (ERs) are flavin dependent enzymes that catalyze the asymmetric reduction of activated carbon-carbon double bonds. In particular, α,β-unsaturated carbonyl compounds (e.g. enals and enones) as well as nitroalkenes are rapidly reduced. Conversely, α,β-unsaturated esters are poorly accepted substrates whereas free carboxylic acids are not converted at all. The only exceptions are α,β-unsaturated diacids, diesters as well as esters bearing an electron-withdrawing group in α- or β-position. Here, we present an alternative approach that has a general applicability for directly obtaining diverse chiral α-substituted carboxylic acids. This approach combines two enzyme classes, namely ERs and aldehyde dehydrogenases (Ald-DHs), in a concurrent reductive-oxidative biocatalytic cascade. This strategy has several advantages as the starting material is an α-substituted α,β-unsaturated aldehyde, a class of compounds extremely reactive for the reduction of the alkene moiety. Furthermore no external hydride source from a sacrificial substrate (e.g. glucose, formate) is required since the hydride for the first reductive step is liberated in the second oxidative step. Such a process is defined as a hydrogen-borrowing cascade. This methodology has wide applicability as it was successfully applied to the synthesis of chiral substituted hydrocinnamic acids, aliphatic acids, heterocycles and even acetylated amino acids with elevated yield, chemo- and stereo-selectivity. A systematic methodology for optimizing the hydrogen-borrowing two-enzyme synthesis of α-chiral substituted carboxylic acids was developed. This systematic methodology has general applicability for the development of diverse hydrogen-borrowing processes that possess the highest atom efficiency and the lowest environmental impact. This journal is
- Knaus, Tanja,Mutti, Francesco G.,Humphreys, Luke D.,Turner, Nicholas J.,Scrutton, Nigel S.
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p. 223 - 233
(2015/02/19)
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- An efficient TiCl4-catalysed method for the synthesis of para-substituted aromatic aldehydes
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An efficient and highly selective synthesis of para-substituted aromatic aldehydes has been achieved by TiCl4-catalysed Friedel-Crafts alkylation of monosubstituted benzenes with methacrolein diacetyl acetal.
- Zhou, Chenfeng,Su, Weike
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p. 555 - 557
(2015/11/27)
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- Sonocatalytic degradation of a textile dye over Gd-doped ZnO nanoparticles synthesized through sonochemical process
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The present study was performed to sonochemically synthesize GdxZn1-xO (x = 0-0.1) nanoparticles for sonocatalysis of Acid Orange 7 (AO7) in an aqueous medium. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM
- Khataee, Alireza,Soltani, Reza Darvishi Cheshmeh,Karimi, Atefeh,Joo, Sang Woo
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p. 219 - 230
(2015/02/19)
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- Aryl-based ferrocenyl phosphine ligands in the rhodium(I)-catalyzed hydroformylation of olefins
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Ferrocenyl-based phosphine ligands [Fe{1-PPh2(spacer)-2-NMe 2CH2C5H3}(C5H 5)] (spacer = 1,4-phenylene (rac-1), 1,3-phenylene (rac-2), 4,4′-biphenylene (rac-3), 2,5-thienylene (rac-4)) were applied in the rhodium(I)-catalyzed hydroformylation of various olefins (styrene, allylbenzene and 1-hexene) with higher chemo- and regioselectivity than a rhodium(I) catalyst precursor alone. The different σ-donor properties of rac-1-4 were elucidated by 31P{1H} NMR spectroscopy of the corresponding selenides.
- Madalska, Martyna,L?nnecke, Peter,Hey-Hawkins, Evamarie
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p. 137 - 142
(2014/01/17)
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- Magnetic nanoparticle supported triphenylphosphine ligand for the Rh-catalyzed hydroformylation reaction
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A magnetic recyclable nano-triphenylphosphine (nano-TPP) ligand was synthesized by simply loading a dopamine-triphenylphosphine derivative onto the surface of super paramagnetic iron oxide nanoparticle (SPION). Via the cooperation between surface neighbor TPP units, nano-TPPs can bond to Rh atoms forming magnetic recyclable nano-TPPRh complexes to catalyze the hydroformylation reaction and can be reused for 20 times with the compensation of Rh salt.
- Duanmu, Chuansong,Wu, Linlin,Gu, Jian,Xu, Xingyou,Feng, Liangdong,Gu, Xu
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- Immobilization of palladium catalyst on magnetically separable polyurea nanosupport
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This work describes a method for preparing magnetic polyurea nanoparticles (PU NPs) and their utilization as a catalyst support. The method is based on entrapment of hydrophilic magnetic nanoparticles within the polyurea matrix. The synthetic process of these magnetic polyurea nanoparticles is based on oil-in-oil nanoemulsification of an organic polar phase comprised of N,N-dimethylacetamide (DMAc), 2,6-diaminopyridine and ionic liquid modified magnetite nanoparticles (MNPs-IL), in heptane containing a suitable surfactant. This was followed by interfacial polycondensation reaction between an isocyanate monomer, polymethylenepolyphenyl isocyanate (PAPI 27), and the amine monomer producing magnetically separable polyurea nanoparticles. Subsequently, these particles were employed as a catalyst nanosupport. Two catalytic systems based on the encapsulation of Pd(OAc)2 within magnetic PU NPs or their adsorption on the surface of these particles were produced and subjected to hydrogenation reactions and selective hydrogenations of α,β-unsaturated compounds. Pd(OAc)2 adsorbed on the surface of the magnetic PU NPs demonstrated high catalytic activity and selectivity, which was superior to the conventional catalyst Pd/C or palladium nanoparticles supported directly on the surface of magnetite nanoparticles. The catalyst was easily recovered from the reaction mixture by applying an external magnetic field and recycled over five times without observing any significant loss in its catalytic efficiency. This journal is
- Natour, Suzana,Abu-Reziq, Raed
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p. 48299 - 48309
(2014/12/10)
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- METHOD FOR HYDROFORMYLATION OF UNSATURATED COMPOUNDS
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The invention relates to a method for hydroformylation of unsaturated compounds such as olefins and alkynes using mixtures of synthesis gas (CO/H2), in which either the unsaturated compounds and a catalyst are heated to a reaction temperature of 60 to 200° C. and the synthesis gas is then added, or the unsaturated compounds and the catalyst are brought into contact with pure CO at normal temperature in a preformation step, then are heated to reaction temperature and on reaching the reaction temperature the CO is replaced by the synthesis gas. The pressure is 1 to 200 bar and the CO:H2 ratio in the synthesis gas is in the range from 1:1 to 50:1. The iridium catalyst used comprises a phosphorus-containing ligand in the iridium:ligand ratio in the range from 1:1 to 1:100. With high catalyst activities and low catalyst use, very high turnover frequencies are achieved.
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Paragraph 0084
(2014/02/16)
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- Easily accessible and highly tunable bisphosphine ligands for asymmetric hydroformylation of terminal and internal alkenes
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An efficient methodology for synthesizing a small library of easily tunable and sterically bulky ligands for asymmetric hydroformylation (AHF) has been reported. Five groups of alkene substrates have been tested with excellent conversions, moderate-to-excellent regio- and enantioselectivities. Among the best result of the reported literature, application of ligand 1 c in the highly selective AHF of the challenging substrate 2,5-dihydrofuran yielded almost one isomer in up to 99 % conversion along with enantiomeric excesses (ee) of up to 92 %. Highly enantioselective AHF of dihydropyrrole substrates is achieved using the same ligand, with up to 95 % ee and up to >1:50 β-isomer/α- isomer ratio. The simpler the better! An efficient method for the easy and tunable synthesis of a series of asymmetric hydroformylation (AHF) ligands from low-cost, commercially available starting materials has been reported. These ligands can give excellent conversions and moderate to excellent regio- and enantioselectivities for a broad range of mono- and disubstituted alkenes with a low catalyst loading (substrate-to-catalyst ratios (S/C) of 1000:1 to 3000:1).
- Xu, Kun,Zheng, Xin,Wang, Zhiyong,Zhang, Xumu
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p. 4357 - 4362
(2014/05/06)
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- Palladium on charcoal as a catalyst for stoichiometric chemo- and stereoselective hydrosilylations and hydrogenations with triethylsilane
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Stoichiometric quantities of triethylsilane in the presence of activated Pd/C as the catalyst can be used to effect chemo-, regio-, and stereoselective hydrosilylation and transfer hydrogenation reactions. α,β-Unsaturated aldehydes and ketones are selectively hydrosilylated to give the corresponding enol silanes or transfer hydrogenated to give the saturated carbonyl compounds in the presence of other reducible functional groups.
- Tuokko, Sakari,Pihko, Petri M.
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p. 1740 - 1751
(2015/02/19)
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- Scope and mechanism in palladium-catalyzed isomerizations of highly substituted allylic, homoallylic, and alkenyl alcohols
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Herein we report the palladium-catalyzed isomerization of highly substituted allylic alcohols and alkenyl alcohols by means of a single catalytic system. The operationally simple reaction protocol is applicable to a broad range of substrates and displays a wide functional group tolerance, and the products are usually isolated in high chemical yield. Experimental and computational mechanistic investigations provide complementary and converging evidence for a chain-walking process consisting of repeated migratory insertion/β-H elimination sequences. Interestingly, the catalyst does not dissociate from the substrate in the isomerization of allylic alcohols, whereas it disengages during the isomerization of alkenyl alcohols when additional substituents are present on the alkyl chain.
- Larionov, Evgeny,Lin, Luqing,Gune, Laure,Mazet, Clment
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supporting information
p. 16882 - 16894
(2015/01/09)
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- Selective hydroformylation of various olefins using diphosphinite ligands
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Novel diphosphinite ligands are synthesized by the reaction of various derivatives of 1,3-diols with chlorodiphenylphosphine. The synthesized ligands exhibited considerable impact on hydroformylation of various olefins with excellent regioselectivity toward branched aldehyde. The effect of solvent, temperature, pressure and catalyst loading on the hydroformylation reaction is also described. The synthesized diphosphinite ligands with rhodium precursor works under milder reaction conditions as compared to traditional phosphine and phosphite-based ligands. Copyright 2013 John Wiley & Sons, Ltd. A novel diphosphinite ligands are synthesized by the reaction of various derivatives of 1,3-diol with chlorodiphenylphosphine. The synthesized ligands exhibited a considerable impact on hydroformylation of various olefins with excellent regioselectivity toward branched aldehyde. The effect of solvent, temperature, pressure and catalyst loading on the hydroformylation reaction is also described. The synthesized diphosphinite ligands with Rhodium precursor works at milder reaction conditions as compared to traditional phosphine and phosphite based ligands. Copyright
- Khan, Shoeb R.,Bhanage, Bhalchandra M.
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p. 313 - 317
(2013/07/04)
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- Room temperature ambient pressure (RTAP)-hydroformylation in water using a self-assembling ligand
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We herein demonstrate a hydroformylation at room temperature and ambient pressure (RTAP) using our Rh/6-DPPon (1) system in aqueous media. The hydrogen bonding network of the ligand backbone stays intact, exemplified by the excellent regioselectivity for the linear aldehyde. Various substrates with different functional groups (with some prone to hydrolysis) are stable under the applied conditions and can undergo hydroformylation resulting in good yields. Copyright
- Straub, Alexander T.,Otto, Marina,Usui, Ippei,Breit, Bernhard
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supporting information
p. 2071 - 2075
(2013/08/23)
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- Oxidative esterification of aldehydes using a recyclable oxoammonium salt
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A simple, high yielding, rapid route for the oxidative esterification of a wide range aldehydes to hexafluoroisopropyl (HFIP) esters using the oxoammonium salt 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1a) is reported. These esters can be readily transformed into a variety of other functional groups. The spent oxidant (1b) can be recovered and conveniently reoxidized to regenerate the oxoammonium salt, 1a.
- Kelly, Christopher B.,Mercadante, Michael A.,Wiles, Rebecca J.,Leadbeater, Nicholas E.
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p. 2222 - 2225
(2013/06/05)
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- How phenyl makes a difference: Mechanistic insights into the ruthenium(ii)-catalysed isomerisation of allylic alcohols
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[RuCl(η5-3-phenylindenyl)(PPh3)2] (1) has been shown to be a highly active catalyst for the isomerisation of allylic alcohols to the corresponding ketones. A variety of substrates undergo the transformation, typically with 0.25-0.5 mol% of catalyst at room temperature, outperforming commonly-used complexes such as [RuCl(Cp)(PPh3) 2] and [RuCl(η5-indenyl)(PPh3) 2]. Mechanistic experiments and density functional theory have been employed to investigate the mechanism and understand the effect of catalyst structure on reactivity. These investigations suggest a oxo-π-allyl mechanism is in operation, avoiding intermediate ruthenium hydride complexes and leading to a characteristic 1,3-deuterium shift. Important mechanistic insights from DFT and experiments also allowed for the design of a protocol that expands the scope of the transformation to include primary allylic alcohols.
- Manzini, Simone,Poater, Albert,Nelson, David J.,Cavallo, Luigi,Nolan, Steven P.
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p. 180 - 188
(2014/01/06)
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- Biocatalytic asymmetric alkene reduction: Crystal structure and characterization of a double bond reductase from Nicotiana tabacum
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The application of biocatalysis for the asymmetric reduction of activated C=C is a powerful tool for the manufacture of high-value chemical commodities. The biocatalytic potential of "-ene" reductases from the Old Yellow Enzyme (OYE) family of oxidoreductases is well-known; however, the specificity of these enzymes toward mainly small molecule substrates has highlighted the need to discover "-ene" reductases from different enzymatic classes to broaden industrial applicability. Here, we describe the characterization of a flavin-free double bond reductase from Nicotiana tabacum (NtDBR), which belongs to the leukotriene B4 dehydrogenase (LTD) subfamily of the zinc-independent, medium chain dehydrogenase/reductase superfamily of enzymes. Using steady-state kinetics and biotransformation reactions, we have demonstrated the regio- and stereospecificity of NtDBR against a variety of α,β-unsaturated activated alkenes. In addition to catalyzing the reduction of typical LTD substrates and several classical OYE-like substrates, NtDBR also exhibited complementary activity by reducing non-OYE substrates (i.e., reducing the exocyclic C=C double bond of (R)-pulegone) and in some cases showing an opposite stereopreference in comparison with the OYE family member pentaerythritol tetranitrate (PETN) reductase. This serves to augment classical OYE "-ene" reductase activity and, coupled with its aerobic stability, emphasizes the potential industrial value of NtDBR. Furthermore, we also report the X-ray crystal structures of the holo-, binary NADP(H)-bound, and ternary [NADP+ and 4-hydroxy-3-methoxycinnamaldehyde (9a)-bound] NtDBR complexes. These will underpin structure-driven site-saturated mutagenesis studies aimed at enhancing the reactivity, stereochemistry, and specificity of this enzyme.
- Mansell, David J.,Toogood, Helen S.,Waller, John,Hughes, John M.X.,Levy, Colin W.,Gardiner, John M.,Scrutton, Nigel S.
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p. 370 - 379
(2013/08/25)
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- Dehydrogenation of perfluoroalkyl ketones by using a recyclable oxoammonium salt
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A novel dehydrogenation reaction of perfluoroalkyl ketones by the oxoammonium salt 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (4-NHAc-TEMPO+BF4-, Bobbitt's salt, 1) is described. The reaction proceeds under mildly basic conditions and appears to be unique to perfluoroalkyl ketones. A proposed mechanism for this unusual transformation is given. The byproduct of the reaction, 4-acetylamino-2,2,6,6-tetramethyl-1-piperidinyloxy (1a), can easily be recovered and used to regenerate the oxoammonium salt. The dehydrogenation of perfluoroalkyl ketones by using an oxoammonium salt is reported. The reaction proceeds under mildly basic conditions and affords α,β-unsaturated products in fair to excellent yields. The reaction likely proceeds through a two-step sequence. The spent oxidant can easily be recovered and used to regenerate the oxoammonium salt. Copyright
- Hamlin, Trevor A.,Kelly, Christopher B.,Leadbeater, Nicholas E.
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supporting information
p. 3658 - 3661
(2013/07/19)
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- Chemoselective hydrogenation of the olefinic bonds using a palladium/magnesium-lanthanum mixed oxide catalyst
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A palladium/magnesium-lanthanum mixed oxide catalyst is found to be an efficient heterogeneous catalyst for the chemoselective hydrogenation of olefinic double bonds in the presence of various functional groups. The catalyst was recovered by centrifugation and reused for several cycles with consistent activity and selectivity. Copyright
- Kantam, Mannepalli Lakshmi,Kishore, Ramineni,Yadav, Jagjit,Sudhakar, Medak,Venugopal, Akula
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supporting information; experimental part
p. 663 - 669
(2012/04/23)
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- Layered double hydroxides supported nano palladium: An efficient catalyst for the chemoselective hydrogenation of olefinic bonds
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Chemoselective hydrogenation of olefinic double bonds in the presence of various functional groups using layered double hydroxides supported nanopalladium (LDH-Pd0) catalyst is described. LDH-Pd0 was recovered quantitatively by simple filtration and reused several times with consistent activity and selectivity.
- Lakshmi, Kantam M.,Parsharamulu,Manorama
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p. 115 - 119
(2013/01/15)
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- Chemoselective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst
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Selective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst was developed. The reduction of CO bond could be efficiently inhibited by the addition of carbonates, and high selectivity to the corresponding saturated aldehydes was achieved under mild conditions. This protocol provides an alternative for efficient preparation of saturated aldehydes.
- Du, Wen Qiang,Rong, Ze Ming,Liang, Yan,Wang, Yong,Lu, Xin Yi,Wang, Yi Fan,Lu, Lian Hai
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experimental part
p. 773 - 776
(2012/08/14)
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- An asymmetric hydroformylation catalyst that delivers branched aldehydes from alkyl alkenes
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Surprising selectivity: The first enantioselective hydroformylations of simple alkenes of type RCH2CH=CH2 to preferentially deliver the branched aldehyde product have been discovered using a new chiral ligand, named bobphos (see scheme). Established ligands are unselective in this reaction or show a slight preference towards the linear aldehyde. Copyright
- Noonan, Gary M.,Fuentes, Jose A.,Cobley, Christopher J.,Clarke, Matthew L.
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supporting information; experimental part
p. 2477 - 2480
(2012/04/18)
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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 17-19
(2012/02/13)
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- Rhodium/tris-binaphthyl chiral monophosphite complexes: Efficient catalysts for the hydroformylation of disubstituted aryl olefins
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A family of threefold symmetry phosphite ligands, P(O-BIN-OR)3 (BIN = 2,2′-binaphthyl; R = Me, Bn, CHPh2, 1-adamantyl), derived from enantiomerically pure (R)-BINOL, was developed. Cone angles within the range 240-270° were calculated for the phosphite ligands, using the computational PM6 Hamiltonian. Their rhodium complexes formed in situ showed remarkable catalytic activity in the hydroformylation of hindered phenylpropenes, under relatively mild reaction conditions, with full chemoselectivity for aldehydes, high regioselectivity, however with low enantioselectivity. The ether substituents at the ligand affected considerably the catalytic activity on the hydroformylation of 1,1- and 1,2-disubstituted aryl olefins. The kinetics of the hydroformylation of trans-1-phenyl-1-propene, using tris[(R)-2′-benzyloxy-1,1′-binaphthyl-2-yl]phosphite as model ligand, was investigated. A first order dependence in the hydroformylation initial rate with respect to substrate and catalyst concentrations was found, as well as a positive order with respect to the partial pressure of H2, and a slightly negative order with respect to phosphite concentration and CO partial pressure.
- Carrilho, Rui M.B.,Neves,Loureno, Mirtha A.O.,Abreu, Artur R.,Rosado, Mário T.S.,Abreu, Paulo E.,Eusébio, M. Ermelinda S.,Kollár, László,Bayón, J. Carles,Pereira, Mariette M.
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experimental part
p. 28 - 34
(2012/02/04)
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- A general and efficient iridium-catalyzed hydroformylation of olefins
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Breaking with conventional wisdom: Hydroformylation catalysts are generally based on rhodium; earlier, cobalt was used. Iridium, which is less expensive than rhodium, was considered too unreactive. However, iridium/phosphine complexes have now been shown to form active catalysts for the hydroformylation of olefins under mild conditions (see scheme; R1, R2=H, alkyl, aryl; R3=H, alkyl). Competing hydrogenation side reactions can be suppressed. Copyright
- Piras, Irene,Jennerjahn, Reiko,Jackstell, Ralf,Spannenberg, Anke,Franke, Robert,Beller, Matthias
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experimental part
p. 280 - 284
(2011/02/28)
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