- Mechanochemical, Water-Assisted Asymmetric Transfer Hydrogenation of Ketones Using Ruthenium Catalyst
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Asymmetric catalytic reactions are among the most convenient and environmentally benign methods to obtain optically pure compounds. The aim of this study was to develop a green system for the asymmetric transfer hydrogenation of ketones, applying chiral Ru catalyst in aqueous media and mechanochemical energy transmission. Using a ball mill we have optimized the milling parameters in the transfer hydrogenation of acetophenone followed by reduction of various substituted derivatives. The scope of the method was extended to carbo- and heterocyclic ketones. The scale-up of the developed system was successful, the optically enriched alcohols could be obtained in high yields. The developed mechanochemical system provides TOFs up to 168 h?1. Our present study is the first in which mechanochemically activated enantioselective transfer hydrogenations were carried out, thus, may be a useful guide for the practical synthesis of optically pure chiral secondary alcohols.
- Kolcsár, Vanessza Judit,Sz?ll?si, Gy?rgy
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- Deep eutectic solvents as H2-sources for Ru(II)-catalyzed transfer hydrogenation of carbonyl compounds under mild conditions
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The employment of easily affordable ruthenium(II)-complexes as pre-catalysts in the transfer hydrogenation of carbonyl compounds in deep eutectic media is described for the first time. The eutectic mixture tetrabutylammonium bromide/formic acid = 1/1 (TBABr/HCOOH = 1/1) acts both as reaction medium and hydrogen source. The addition of a base is required for the process to occur. An extensive optimization of the reaction conditions has been carried out, in terms of catalyst loading, type of complexes, H2-donors, reaction temperature and time. The combination of the dimeric complex [RuCl(p-cymene)-μ-Cl]2 (0.01–0.05 eq.) and the ligand dppf (1,1′-ferrocenediyl-bis(diphenylphosphine)ferrocene) in 1/1 molar ratio has proven to be a suitable catalytic system for the reduction of several and diverse aldehydes and ketones to their corresponding alcohols under mild conditions (40–60 °C) in air, showing from moderate to excellent tolerability towards different functional groups (halogen, cyano, nitro, phenol). The reduction of imine compounds to their corresponding amine derivatives was also studied. In addition, the comparison between the results obtained in TBABr/HCOOH and in organic solvents suggests a non-innocent effect of the DES medium during the process.
- Cavallo, Marzia,Arnodo, Davide,Mannu, Alberto,Blangetti, Marco,Prandi, Cristina,Baratta, Walter,Baldino, Salvatore
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supporting information
(2021/02/22)
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- Galantamine-curcumin hybrids as dual-site binding acetylcholinesterase inhibitors
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Galantamine (GAL) and curcumin (CU) are alkaloids used to improve symptomatically neurodegenerative conditions like Alzheimer's disease (AD). GAL acts mainly as an inhibitor of the enzyme acetylcholinesterase (AChE). CU binds to amyloid-beta (Aβ) oligomers and inhibits the formation of Aβ plaques. Here, we combine GAL core with CU fragments and design a combinatorial library of GAL-CU hybrids as dual-site binding AChE inhibitors. The designed hybrids are screened for optimal ADME properties and BBB permeability and docked on AChE. The 14 best performing compounds are synthesized and tested in vitro for neurotoxicity and anti-AChE activity. Five of them are less toxic than GAL and CU and show activities between 41 and 186 times higher than GAL.
- Atanasova, Mariyana,Atanasova, Teodora,Doytchinova, Irini,Ivanov, Stefan,Konstantinov, Spiro,Lukarski, Atanas,Philipova, Irena,Stavrakov, Georgi,Zheleva, Dimitrina,Zhivkova, Zvetanka D.
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- New Zinc Catalyst for Hydrosilylation of Carbonyl Compounds
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A new zinc complex was synthesized and applied in the catalytic hydrosilylation of carbonyl compounds. Optimization of the reaction conditions showed that the presence a substoichiometric amount of methanol accelerates the process significantly. The reaction can proceed at very low catalyst load (down to 0.1 molpercent) under mild reaction conditions. The reaction tolerates the presence of C=C bonds, and thus can be useful for the synthesis of allylic alcohols from α,β-unsaturated aldehydes and ketones.
- Alshakova, Iryna D.,Nikonov, Georgii I.
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p. 3305 - 3312
(2019/08/28)
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- Polypyridyl iridium(III) based catalysts for highly chemoselective hydrogenation of aldehydes
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Iridium-catalyzed transfer hydrogenation (TH) of carbonyl compounds using HCOOR (R = H, Na, NH4) as a hydrogen source is a pivotal process as it provides the clean process and is easy to execute. However, the existing highly efficient iridium catalysts work at a narrow pH; thus, does not apply to a wide variety of substrates. Therefore, the development of a new catalyst which works at a broad pH range is essential as it can gain a broader scope of utilization. Here we report highly efficient polypyridyl iridium(III) catalysts, [Ir(tpy)(L)Cl](PF6)2 {where tpy = 2,2′:6′,2′'-Terpyridine, L = phen (1,10-Phenanthroline), Me2phen (4,7-Dimethyl-1,10-phenanthroline), Me4phen (3,4,7,8-Tetramethyl-1,10-phenanthroline), Me2bpy (4,4′-Dimethyl-2–2′-dipyridyl)} for the chemoselective reduction of aldehydes to alcohols in aqueous ethanol and sodium formate as the hydride source. The reaction can be carried out efficiently in broad pH ranges, from pH 6 to 11. These catalysts are air stable, easy to prepare using commercially available starting materials, and are highly applicable for a wide range of substrates, such as electron-rich or deficient (hetero)arenes, halogens, phenols, alkoxy, ketones, esters, carboxylic acids, cyano, and nitro groups. Particularly, acid and hydroxy groups containing aldehydes were reduced successfully in basic and acidic reaction conditions, demonstrating the efficiency of the catalyst in a broad pH range with high conversion rates under microwave irradiation.
- Pandrala, Mallesh,Resendez, Angel,Malhotra, Sanjay V.
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p. 283 - 288
(2019/09/30)
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- Cobalt-Catalyzed Hydroboration of Alkenes, Aldehydes, and Ketones
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An operationally convenient and general method for hydroboration of alkenes, aldehydes, and ketones employing Co(acac)3 as a precatalyst is reported. The hydroboration of alkenes in the presence of HBpin, PPh3, and NaOtBu affords good to excellent yields with high Markovnikov selectivity with up to 97:3 branched/linear selectivity. Moreover, Co(acac)3 could be used effectively to hydroborate aldehydes and ketones in the absence of additives under mild reaction conditions. Inter- and intramolecular chemoselective reduction of the aldehyde group took place over the ketone functional group.
- Tamang, Sem Raj,Bedi, Deepika,Shafiei-Haghighi, Sara,Smith, Cecilia R.,Crawford, Christian,Findlater, Michael
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supporting information
p. 6695 - 6700
(2018/11/21)
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- Methanol as hydrogen source: Transfer hydrogenation of aromatic aldehydes with a rhodacycle
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A cyclometalated rhodium complex has been shown to perform highly selective and efficient reduction of aldehydes, deriving the hydrogen from methanol. With methanol as both the solvent and hydrogen donor under mild conditions and an open atmosphere, a wide range of aromatic aldehydes were reduced to the corresponding alcohols, without affecting other functional groups.
- Aboo, Ahmed H.,Bennett, Elliot L.,Deeprose, Mark,Robertson, Craig M.,Iggo, Jonathan A.,Xiao, Jianliang
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supporting information
p. 11805 - 11808
(2018/11/10)
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- Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions
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We recently reported a novel hybrid batch-flow synthesis of the antipsychotic drug clozapine in which the reduction of a nitroaryl group is described under flow conditions using sodium dithionite. We now report the expansion of this method to include the reduction of aldehydes. The method developed affords yields which are comparable to those under batch conditions, has a reduced reaction time and improved space-time productivity. Furthermore, the approach allows the selective reduction of aldehydes in the presence of ketones and has been demonstrated as a continuous process.
- Neyt, Nicole C.,Riley, Darren L.
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supporting information
p. 1529 - 1536
(2018/07/05)
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- Iron Catalyzed Hydroboration of Aldehydes and Ketones
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We report an operationally convenient room temperature hydroboration of aldehydes and ketones employing Fe(acac)3 as precatalyst. The hydroboration of aldehydes and ketones proceeded efficiently at room temperature to yield, after work up, 1° and 2° alcohols; chemoselective hydroboration of aldehydes over ketones is attained under these conditions. We propose a σ-bond metathesis mechanism in which an Fe-H intermediate is postulated to be a key reactive species.
- Tamang, Sem Raj,Findlater, Michael
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p. 12857 - 12862
(2017/12/08)
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- Chemoselective continuous-flow hydrogenation of aldehydes catalyzed by platinum nanoparticles dispersed in an amphiphilic resin
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A chemoselective continuous-flow hydrogenation of aldehydes catalyzed by a dispersion of platinum nanoparticles in an amphiphilic polymer (ARP-Pt) has been developed. Aromatic and aliphatic aldehydes bearing various reducible functional groups, such as keto, ester, or amide groups, readily underwent flow hydrogenation in aqueous solutions within 22 s in a continuous-flow system containing ARP-Pt to give the corresponding primary benzylic or aliphatic alcohols in ≤99% yield with excellent chemoselectivity. Moreover, the long-term continuous-flow hydrogenation of benzaldehyde for 8 days was realized, and the total turnover number of the catalyst reached 997. The flow hydrogenation system provides an efficient and practical method for the chemoselective hydrogenation of aldehydes bearing reducible functional groups.
- Osako, Takao,Torii, Kaoru,Hirata, Shuichi,Uozumi, Yasuhiro
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p. 7371 - 7377
(2017/11/09)
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- Air-Stable Gold Nanoparticles Ligated by Secondary Phosphine Oxides as Catalyst for the Chemoselective Hydrogenation of Substituted Aldehydes: A Remarkable Ligand Effect
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Air-stable and homogeneous gold nanoparticles (AuNPs, 1a-5a) ligated by various secondary phosphine oxides (SPOs), [R1R2P(O)H] (R1 = Naph, R2 = tBu, L1; R1 = R2 = Ph, L2; R1 = Ph, R2 = Naph, L3; R1 = R2 = Et, L4; R1 = R2 = Cy, L5; R1 = R2 = tBu, L6), with different electronic and steric properties were synthesized via NaBH4 reduction of the corresponding Au(I)-SPO complex. These easily accessible ligands allow the formation of well dispersed and small nanoparticles (size 1.2-2.2 nm), which were characterized by the use of a wide variety of techniques, such as transmission electron microscopy, thermogravimetric analysis, UV-vis, energy-dispersive X-ray, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR), and cross polarization magic angle spinning (CP MAS) NMR spectroscopy. A pronounced ligand effect was found, and CP MAS NMR experiments enabled us to probe important differences in the polarity of the P-O bond of the SPOs coordinated to the nanoparticle surface depending on the type of substituents in the ligand. AuNPs containing aryl SPOs carry only SPO anions and are highly selective for aldehyde hydrogenation. AuNPs of similar size made with alkyl SPOs contain also SPOH, hydrogen bonded to SPO anions. As a consequence they contain less Au(I) and more Au(0), as is also evidenced by XPS. They are less selective and active in aldehyde hydrogenation and now show the typical activity of Au(0)NPs in nitro group hydrogenation. (Chemical Equation Presented).
- Cano, Israel,Huertos, Miguel A.,Chapman, Andrew M.,Buntkowsky, Gerd,Gutmann, Torsten,Groszewicz, Pedro B.,Van Leeuwen, Piet W. N. M.
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supporting information
p. 7718 - 7727
(2015/07/01)
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- Air-stable gold nanoparticles ligated by secondary phosphine oxides for the chemoselective hydrogenation of aldehydes: Crucial role of the ligand
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The synthesis of air-stable and homogeneous gold nanoparticles (AuNPs) employing tert-butyl(naphthalen-1-yl)phosphine oxide as supporting ligand is described via NaBH4 reduction of a Au(I) precursor, [(tert-butyl(naphthalen-1-yl)phosphine oxide)AuCl]2. This highly reproducible and simple procedure furnishes small (1.24 ± 0.16 nm), highly soluble nanoparticles that are found to be highly active catalysts for the hydrogenation of substituted aldehydes, giving high conversions and chemoselectivities for a wide variety of substrates. In addition to catalytic studies the role of the novel stabilizer in the remarkable activity and selectivity exhibited by this system was interrogated thoroughly using a wide range of techniques, including ATR FT-IR, HRMAS NMR, XPS, and EDX spectroscopy. In particular, isotopic labeling experiments enabled us to probe the coordination mode adopted by the SPO ligand bound to the nanoparticle surface by ATR FT-IR spectroscopy. In combination with a series of control experiments we speculate that the SPO ligand demonstrates ligand-metal cooperative effects and plays a seminal role in the heterolytic hydrogenation mechanism.
- Cano, Israel,Chapman, Andrew M.,Urakawa, Atsushi,Van Leeuwen, Piet W. N. M.
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supporting information
p. 2520 - 2528
(2014/03/21)
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- Electrophilicity and nucleophilicity of commonly used aldehydes
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The present approach for determining the electrophilicity (E) and nucleophilicity (N) of aldehydes includes a kinetic study of KMNO4 oxidation and NaBH4 reduction of aldehydes. A transition state analysis of the KMNO4 promoted aldehyde oxidation reaction has been performed, which shows a very good correlation with experimental results. The validity of the experimental method has been tested using the experimental activation parameters of the two reactions. The utility of the present approach is further demonstrated by the theoretical versus experimental relationship, which provides easy access to E and N values for various aldehydes and offers an at-a-glance assessment of the chemical reactivity of aldehydes in various reactions. the Partner Organisations 2014.
- Pratihar, Sanjay
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p. 5781 - 5788
(2014/07/22)
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- Benzylic hydroxylation of aromatic compounds by P450 BM3
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Cytochrome P450 BM3 monooxygenase from Bacillus megaterium and its variants are promising catalysts for organic synthesis. Aiming at the identification of variants for selective hydroxylation of functionalised aromatic compounds, the double mutant F87A L188C showed remarkably improved catalytic activity towards a set of tested toluene derivatives. The apparent catalytic efficiency of this variant towards the model substrate methyl 2-methoxy-3-methylbenzoate was 63.6 s-1 M-1, which is 535-fold higher compared to that of wild-type BM3. Furthermore, the double mutant selectively catalysed the benzylic hydroxylation of numerous toluene derivatives, especially in the presence of carbonyl- or carboxyl-functions that are directly attached to the aromatic ring. Preparative scale conversion resulted in efficient production of methyl 3-(hydroxymethyl)-2-methoxybenzoate (73% yield) which proved that F87A L188C is a suitable, efficient and sustainable catalyst for the introduction of benzylic hydroxyl groups in general.
- Neufeld, Katharina,Marienhagen, Jan,Schwaneberg, Ulrich,Pietruszka, Joerg
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p. 2408 - 2421
(2013/09/12)
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- Multienzymatic preparation of 3-[(1R)-1-hydroxyethyl]benzoic acid and (2S)-hydroxy(phenyl)ethanoic acid
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The use of two oxidoreductases (an aldoketo reductase from Escherichia coli JM109 and an alcohol dehydrogenase from Lactobacillus brevis) has demonstrated that it is possible to prepare enatiomerically pure diols in a one-pot operation. The reactions were applied to the synthesis of (1R)-1-[3- (hydroxymethyl) phenyl]ethanol and (1S)-1-phenylethane-1,2-diol, using a two-step procedure. The yield is nearly quantitative and the enantiomeric purity is greater than 95%. A third step has been introduced by adding a cell biocatalyst showing dihydrodiol dehydrogenase activity from Pseudomonas fluorescens N3. This allows for the preparation of 3-[(1R)-1-hydroxyethyl] benzoic acid and (2S)-hydroxy(phenyl)ethanoic acid.
- Di Gennaro, Patrizia,Bernasconi, Silvana,Orsini, Fulvia,Corretto, Erika,Sello, Guido
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experimental part
p. 1885 - 1889
(2010/11/16)
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- Intermolecular antiselective and enantioselective reductive coupling of enones and aromatic aldehydes with chiral rh(phebox) catalysts
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The intermolecular reductive coupling reaction of cyclopent-2-enone and aromatic aldehydes was realized by chiral rhodium-(bisoxazolinyl)phenyl catalysts, Rh(Phebox-Ph)(OAc)2(H2O), with diphenymethylsilane as a hydride donor to give
- Shiomi, Takushi,Adachi, Takahiro,Ito, Jun-Ichi,Nishiyama, Hisao
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supporting information; experimental part
p. 1011 - 1014
(2009/07/18)
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- SELECTIVE ANDROGEN RECEPTOR MODULATORS, ANALOGS AND DERIVATIVES THEREOF AND USES THEREOF
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This invention provides new compounds and uses thereof in treating a variety of diseases or conditions in a subject, including,inter alia, prostate cancer, muscle wasting diseases and/or disorders or a bone-related diseases and/or disorders.
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Page/Page column 141; Sheet 11
(2008/06/13)
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- A NEW CLASS OF HISTONE DEACETYLASE INHIBITORS
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New histone deacetylase inhibitors according to the general formula (I) wherein: Q is a bond, CH2, CH-NR3R4, NR5 or oxygen, X is CH or nitrogen, Y is a bond, CH2, oxygen or NR6, Z is CH or
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Page/Page column 55
(2008/06/13)
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