- Oxidation of zinc organometallics prepared by hydrozincation or carbozincation using oxygen
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Organozinc compounds prepared by the hydrozincation or carbazincation of functionalized unsaturated molecules can be directly oxidized by oxygen affording alcohols after reductive workup in satisfactory yields.
- Klement, Ingo,Luetjens, Henning,Knochel, Paul
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- Regioselective addition of stannylcyanocuprates to acetylenic ethers: A chemical and spectroscopic study
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The reactions of acetylenic ether 1 with higher order cuprates 2a, 2b and 2c were studied chemically and spectroscopically. Conditions were developed to efficiently and regioselectively prepare α- and β-stannylvinyl ethers. 1H and 13C NMR studies of these reactions suggest that in the presence of HMPA, higher order stannylcyanocuprate, (Bu3Sn)2Cu(CN)Li2, 2a, exists in equilibrium with Gilman cuprate, (Bu3Sn)2CuLi.
- Cabezas,Oehlschlager
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- Electrophilic Etherification of α-Heteroaryl Carbanions with Monoperoxyacetals as a Route to Ketene O, O- And N, O-Acetals
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Alkyl ketene acetals are useful reactants in a variety of synthetic processes, and yet, there are limited routes to their formation as isolable products. We now report the successful synthesis and isolation of heteroaryl ketene acetals through intermolecular transfer of alkoxyl (δ+OR) from electrophilic peroxides to lithiated benzofurans, indoles, and pyridines. Primary and secondary peroxyacetals enable selective transfer of the nonanomeric alkoxy group in moderate to high yield; substrates bearing an electron-donating substituent show enhanced reactivity toward electrophilic oxygen. Heteroaryl ketene acetals are remarkably stable throughout traditional purification techniques; the superior stability of ketene N,O-acetals compared to ketene O,O-acetals is presumably due to increased aromaticity of the indole and pyridine structures. The presented method overcomes typical problems associated with alkyl ketene acetal synthesis as reported products withstood workup and flash column chromatography procedures.
- Paris, Timothy J.,Schwartz, Chris,Willand-Charnley, Rachel
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- Highly selective and stable ZnO-supported bimetallic RuSn catalyst for the hydrogenation of octanoic acid to octanol
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The chemoselective hydrogenation of biomass-derived carboxylic acids is promising for the development of biorefineries. Herein, the selective conversion of octanoic acid to octanol over bimetallic RuSn/ZnO in a fixed-bed continuous reactor system, is reported. Almost complete conversion (99.4 %) of octanoic acid was achieved, with a remarkably high selectivity to octanol (93.0 %), when using specific reaction conditions (300°C, a weight hourly space velocity (WHSV) of 2 h?1, and 30 atm H2). Characterizations of the catalysts by BET, CO pulse chemisorption, ICP-AES, XRD, XPS and STEM-EDS revealed that the addition of Sn to Ru/ZnO resulted in the formation of a Ru3Sn7 alloy phase as well as SnOx. Comparison with Ru/ZnO catalyst gives an insight that the presence of Ru3Sn7 alloy was most likely the active site and it significantly improved the hydrogenation activity and selectivity to octanol. The SnOx and ZnO favored the formation of octyl octanoate by esterification of the formed octanol and octanoic acid, although it was successfully suppressed by optimizing the reaction conditions. Long-term stability tests revealed that RuSn/ZnO retained its activity for 1000 h with no coke formation. This study reveals the potential of RuSn/ZnO for the valorization of medium-chain fatty acids into value-added chemicals.
- Hidajat, Marcel Jonathan,Hwang, Dong-Won,Yun, Gwang-Nam
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- Identification of a marine NADPH-dependent aldehyde reductase for chemoselective reduction of aldehydes
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A putative aldehyde reductase gene from Oceanospirillum sp. MED92 was overexpressed in Escherichia coli. The recombinant protein (OsAR) was characterized as a monomeric NADPH-dependent aldehyde reductase. The kinetic parameters Km and kcat of OsAR were 0.89 ± 0.08 mM and 11.07 ± 0.99 s-1 for benzaldehyde, 0.04 ± 0.01 mM and 6.05 ± 1.56 s-1 for NADPH, respectively. This enzyme exhibited high activity toward a variety of aromatic and aliphatic aldehydes, but no activity toward ketones. As such, it catalyzed the chemoselective reduction of aldehydes in the presence of ketones, as demonstrated by the reduction of 4-acetylbenzaldehyde or the mixture of hexanal and 2-nonanone, showing the application potential of this marine enzyme in such selective reduction of synthetic importance.
- Li, Guangyue,Ren, Jie,Wu, Qiaqing,Feng, Jinhui,Zhu, Dunming,Ma, Yanhe
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- A facile zirconium(IV) chloride catalysed selective deprotection of t-butyldimethylsilyl (TBDMS) ethers
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A simple and efficient protocol for the selective deprotection of t-butyldimethylsilyl (TBDMS) ethers using 20 mol% ZrCl4 in 20-45 min and in high yields, is reported, wherein it is demonstrated that acid and base sensitive groups and allylic and benzylic groups are unaffected.
- Sharma,Srinivas,Radha Krishna, Palakodety
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- Engineering carboxylic acid reductase for selective synthesis of medium-chain fatty alcohols in yeast
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Medium-chain fatty alcohols (MCFOHs, C6 to C12) are potential substitutes for fossil fuels, such as diesel and jet fuels, and have wide applications in various manufacturing processes. While today MCFOHs are mainly sourced from petrochemicals or plant oils, microbial biosynthesis represents a scalable, reliable, and sustainable alternative. Here, we aim to establish a Saccharomyces cerevisiae platform capable of selectively producing MCFOHs. This was enabled by tailoring the properties of a bacterial carboxylic acid reductase from Mycobacterium marinum (MmCAR). Extensive protein engineering, including directed evolution, structure-guided semirational design, and rational design, was implemented. MmCAR variants with enhanced activity were identified using a growth-coupled high-throughput screening assay relying on the detoxification of the enzyme’s substrate, medium-chain fatty acids (MCFAs). Detailed characterization demonstrated that both the specificity and catalytic activity of MmCAR was successfully improved and a yeast strain harboring the best MmCAR variant generated 2.8-fold more MCFOHs than the strain expressing the unmodified enzyme. Through deletion of the native MCFA exporter gene TPO1, MCFOH production was further improved, resulting in a titer of 252 mg/L for the final strain, which represents a significant improvement in MCFOH production in minimal medium by S. cerevisiae.
- Hu, Yating,Zhu, Zhiwei,Gradischnig, David,Winkler, Margit,Nielsen, Jens,Siewers, Verena
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- Intrinsic isotope effects suggest that the reaction coordinate symmetry for the cytochrome P-450 catalyzed hydroxylation of octane is isozyme independent
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The mechanism of the ω-hydroxylation of octane by three catalytically distinct, purified forms of cytochrome P-450, namely, P-450(b), P-450(c), and P-450(LM2), was investigated by using deuterium isotope effects. The deuterium isotope effects associated with the ω-hydroxylation of octane-1,1,1-2H3, octane-1,8-2H2, and octane-1,1,8,8-2H4 by all three isozymes were determined. From these data the intrinsic isotope effects were calculated and separated into their primary and secondary components. The primary intrinsic isotope effect for the reaction ranged from 7.69 to 9.18 while the secondary intrinsic isotope effect ranged from 1.13 to 1.25. Neither the primary nor secondary isotope effect values were statistically different for any of the isozymes investigated. These data are consistent with a symmetrical transition state for a mechanism involving initial hydrogen atom abstraction followed by hydroxyl radical recombination which is essentially independent of the specific isozyme catalyzing the reaction. It is concluded that (1) in general the porphyrin-[FeO]3+ complex behaves as a source of a triplet-like oxygen atom, (2) the regioselectivity for the site of oxidation is dictated by the apoprotein of the specific isozyme of cytochrome P-450 catalyzing the reaction, and (3) the maximum primary intrinsic isotope effect for any cytochrome P-450 catalyzed oxidation of a carbon center is about 9, assuming no tunneling effects.
- Jones,Rettie,Trager
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- Dod-S-Me and methyl 6-morpholinohexyl sulfide (MMS) as new odorless borane carriers
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Odorless Dod-S-Me (1) and MMS (3) are developed as efficient borane carriers. The yields of hydroborations and reductions with borane complex 2 of 1 are very high and the recovery of 1 after the reaction is quantitative. The borane complexes 4 and 5 of 3 are also useful. In the latter case chromatographic separation is unnecessary when excess oxidizing agent (alkaline H2O2) is used after hydroboration.
- Patra, Pranab K.,Nishide, Kiyoharu,Fuji, Kaoru,Node, Manabu
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- 2-pyridylsilyl group as a multifunctional 'phase tag' for solution phase synthesis
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2-Pyridyldimethylsilyl (2-PyMe2Si) group was found to serve as effective 'phase tag' for acid-base extraction for solution phase synthesis. Acid-base extraction of octyl(2-pyridyl)dimethylsilane gave rise to 98% recovery. The introduction of 2-PyMe2Si group to organic molecules was easily accomplished by Rh catalyzed hydrosilylation of alkenes with 2- PyMe2SiH. The removal of 2-PyMe2Si group was achieved by the oxidation with H2O2/KF (Tamao oxidation). In order to demonstrate the utility of 2- PyMe2Si group as a 'phase tag', a sequential multi-step transformation was conducted. The products of each steps were easily isolated by acid-base extraction, and were sufficiently pure for the direct use in the next step of the sequence.
- Yoshida, Jun-ichi,Itami, Kenichiro,Mitsudo, Koichi,Suga, Seiji
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- Experimental study of chemical equilibria in the liquid-phase reaction between 1-octanol and ethanol to 1-ethoxyoctane
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The equilibrium constants for the liquid-phase dehydration reaction between 1-octanol and ethanol to 1-ethoxyoctane (EOE) and water and the dehydration reaction between two ethanol molecules to ethoxyethane (DEE) and water were determined over Amberlyst 70 in the temperature range (410 to 463) K in a batch reactor. Both reactions were greatly shifted to products at the chemical equilibrium. In particular, product concentrations found for EOE synthesis were higher than those measured for DEE formation. Besides, both liquid-phase etherification reactions proved to be exothermic, with a reaction enthalpy change of (-18.9 ± 1.3) kJ·mol-1 for EOE synthesis and (-13.1 ± 0.9) kJ·mol-1 for DEE one, at 298 K. The EOE standard formation enthalpy value of (-436 ± 7) kJ·mol -1, in good agreement with the estimated value by a modified Benson method, and the EOE standard molar entropy value in the liquid phase of (434 ± 11) J·mol-1·K-1, slightly underestimated by the Benson method, are found.
- Guilera, Jordi,Ramirez, Eliana,Iborra, Montserrat,Tejero, Javier,Cunill, Fidel
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- Novel Cu and Cu2In/aluminosilicate type catalysts for the reduction of biomass-derived volatile fatty acids to alcohols
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This work relates to the consecutive reduction of short chain carboxylic acids (volatile fatty acids, VFAs) to alcohols as main products. Acetic acid (AA) was used as a reactant to model the VFAs that can be produced by either thermochemical or biological biomass degradation. The amorphised zeolite supported copper catalysts (Cu/SiAl), especially the In-modified CuIn/SiAl catalysts, showed high hydroconversion activity and selectivity for alcohol, ester and aldehyde. Catalysts containing dispersed copper particles in amorphous aluminosilicate were obtained by dehydrating and H2-reducing Cu-forms of low-silica synthetic zeolites (A, X, P). The activity of the highly destructed Cu-aluminosilicates was found to depend on the structure of the zeolite precursor. The formation of ethyl acetate could be suppressed by adding water to the AA feed and by modifying the catalyst, e.g. by In2O 3 additive. In the catalysts modified by In2O3 additive formation of copper-indium alloy phase (Cu2In intermetallic compound) was detected resulting in a different selectivity than the one recorded for the Cu/SiAl.
- Harnos, Szabolcs,Onyestyak, Gyoergy,Barthos, Robert,Valyon, Jozsef,Stolcova, Magdalena,Kaszonyi, Alexander
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- REDUCTION OF ALDEHYDES AND KETONES WITH TETRAALKYLAMMONIUM BOROHYDRIDES
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Misinterpretations regarding the selectivity of tetraalkylammonium borohydride reductions in dichloromethane are resolved.Tetrabutylammonium borohydride offers several advantages, but both it and tetraethylammonium borohydride are highly useful synthetic reagents.
- Raber, Douglas J.,Guida, Wayne C.,Shoenberger, Douglas C.
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- Modulation of photodeprotection by the sunscreen protocol
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A protocol for the selective photoremoval of alcohol protecting groups modulated by the presence of auxiliary light absorbing molecules is presented. Thus, by this method, a single light source was used to selectively remove a specific protecting group in the presence of another chromophore with a lower molar absorption coefficient. The use of a molecular sunscreen, either internal or external, was found to be crucial to achieve high selectivities.
- Eivgi, Or,Levin, Efrat,Lemcoff, N. Gabriel
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- In Vivo Reduction of Medium- to Long-Chain Fatty Acids by Carboxylic Acid Reductase (CAR) Enzymes: Limitations and Solutions
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Fatty aldehyde production by chemical synthesis causes an immense burden to the environment. Within this study, we explored a sustainable, aldehyde-selective and mild alternative approach by utilizing carboxylic acid reductases (CARs). CARs from Neurospora crassa (NcCAR), Thermothelomyces thermophila (TtCAR), Nocardia iowensis (NiCAR), Mycobacterium marinum (MmCAR) and Trametes versicolor (TvCAR) were overexpressed in E. coli K-12 MG1655 RARE (DE3) and screened for medium- to long-chain fatty acid (C6–C18) reduction. MmCAR showed the broadest tolerance towards all carbon-chain lengths and was selected for further investigations of fatty aldehyde synthesis in whole cells. To yield relevant product concentrations, different limitations of CAR whole-cell conversions were elucidated and compensated. We coupled an in vitro cofactor recycling system to a whole-cell biocatalyst to support cofactor supply and achieved 12.36 g L?1 of octanal (STY 0.458 g L?1 h?1) with less than 1.5 % of 1-octanol.
- Horvat, Melissa,Winkler, Margit
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- Ternary (Cu, Ni and Co) Nanocatalysts for Hydrogenation of Octanal to Octanol: An Insight into the Cooperative Effect
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Abstract: Ternary metal oxides (Cu–Ni–Co) with different wt% loadings were supported on alumina by using an ultrasonic cavitation-impregnation method. A comparative silica catalyst was also prepared. Powder X-ray diffraction (XRD) showed the presence of the metal oxides on the surface of the supports and from in situ XRD results, the formation of metallic phases under a reducing atmosphere were observed. Temperature-programmed desorption (TPD) revealed the presence of Lewis and Br?nsted acidic sites in the catalysts. The metals supported on alumina showed a better dispersion compared to that on the silica support. All the catalysts were tested for the hydrogenation of octanal in a mixture of 10% octanal in octanol in a continuous flow fixed bed reactor by varying the pressure, temperature and hydrogen molar ratios. Under the hydrogenation conditions, the trimetallic catalysts (with Cu, Ni and Co) showed best catalytic performance for octanal hydrogenation when compared to bimetallic catalysts. The conversion of octanal and the selectivity towards octanol increased in proportion to an increase in the total metallic content and metal dispersion. The alumina based catalysts showed better activity compared to the silica catalyst due to higher metal dispersion. The silica supported catalyst showed a high selectivity towards C24 acetal due to its higher acidity and the product distribution over all the catalysts is in agreement with the distribution of acidic sites. Graphical Abstract: [Figure not available: see fulltext.]
- Valand, Jignesh,Dasireddy, Venkata D. B. C.,Singh, Sooboo,Friedrich, Holger B.
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- Pentaco-ordinate Silicon Compounds in Synthesis: Chemo- and Stereo-selective Reduction of Carbonyl Compounds using Trialkoxy-substituted Silanes and Alkali Metal Alkoxides
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Carbonyl compounds are reduced with trialkoxy-substituted silane to the corresponding alcohols chemo- and stereo-selectively in the presence of alkali metal alkoxide under mild conditions; reduction occurs very smoothly by using an alkoxide derived from pinacol as a bidentate ligand.
- Hosomi, Akira,Hayashida, Hisashi,Kohra, Shinya,Tominaga, Yoshinori
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- Bacterial CYP153A monooxygenases for the synthesis of omega-hydroxylated fatty acids
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CYP153A from Marinobacter aquaeolei has been identified as a fatty acid ω-hydroxylase with a broad substrate range. Two hotspots predicted to influence substrate specificity and selectivity were exchanged. Mutant G307A is 2- to 20-fold more active towards fatty acids than the wild-type. Residue L354 is determinant for the enzyme ω-regioselectivity.
- Honda Malca, Sumire,Scheps, Daniel,Kuehnel, Lisa,Venegas-Venegas, Elena,Seifert, Alexander,Nestl, Bettina M.,Hauer, Bernhard
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- Quantitative Evaluation of the Effect of the Hydrophobicity of the Environment Surrounding Br?nsted Acid Sites on Their Catalytic Activity for the Hydrolysis of Organic Molecules
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Sulfo-functionalized siloxane gels with a variety of surface hydrophobicities were fabricated to elucidate the effect of the environment surrounding the Br?nsted acid site on their catalytic activity for the hydrolysis of organic molecules. A detailed structural analysis of these siloxane gels by elemental analysis, X-ray photoelectron spectroscopy, Fourier-transformed infrared (FT-IR), and 29Si MAS NMR revealed the formation of gel catalysts with a highly condensed siloxane network, which enabled us to quantitatively evaluate the hydrophobicity of the environment surrounding the catalytically active sulfo-functionality. A sulfo group in a highly hydrophobic environment exhibited excellent catalytic turnover frequency for the hydrolysis of acetate esters with a long alkyl chain, whereas not only conventional solid acid catalysts but also liquid acids showed quite low catalytic activity. Detailed kinetic studies corroborated that the adsorption of oleophilic esters at the Br?nsted acid site was facilitated by the surrounding hydrophobic environment, thus significantly promoting hydrolysis under aqueous conditions. Furthermore, sulfo-functionalized siloxane gels with a highly hydrophobic surface showed excellent catalytic activity for the hydrolytic deprotection of silyl ethers.
- Miura, Hiroki,Kameyama, Shutaro,Komori, Daiki,Shishido, Tetsuya
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- Nickel catalyzed hydroboration with catecholborane
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Hydroborations of alkenes and alkyne with catecholborane were found to be catalyzed by activated nickel powder.
- Kabalka,Narayana,Reddy
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- Indium, as an efficient co-catalyst of Cu/Al2O3 in the selective hydrogenation of biomass derived fatty acids to alcohols
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Octanoic acid (OA) as model reactant of medium chain length, and its reduced products, octanal and octanol were hydroconverted over different components of a CuIn/Al2O3 composite catalyst. A fixed-bed flow through reactor was used at 21 bar total pressure in the temperature range of 240-360 °C. Fatty acid hydroconversion activity of alumina supported Cu catalyst and mainly the yield of selectively produced octanol can be greatly increased by In2O3 doping, suppressing the dehydration side reactions. Appearance of metallic indium on alumina supported reduced copper catalyst can arrest the consecutive catalytic reaction at the alcohol formation step prior to further dehydration to ether or alkenes. An industrial, conventionally used Adkins catalyst (72 wt.% CuCr2O4 and 28 wt.% CuO) and the novel bimetallic composite (CuIn/Al2O 3) were compared: both produce octanol with high selectivity, but the new chromium-free fatty acid hydrogenation catalyst is more active, nearly as active as earlier investigated NiIn/Al2O3.
- Onyestyák, Gy?rgy,Harnos, Szabolcs,Kalló, Dénes
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- Deprotection of Acetals and Silyl Ethers Using Some ?-Acceptors
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Hydrolysis of dodecanol dimethyl acetal and dodecyl silyl ethers in MeCN-H2O was examined using a catalytic silyl amount of ?-acceptors such as 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetracyanoethylene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF4), and chloranil (CA).Cleavage of dodecyl triethylsilyl ether with TCNQ and CA was caused by room light.By application of DDQ-catalyzed deprotection of acetals to hydrolysis of tetrahydropyranyl ethers, the corresponding alcohols were obtained in quantitative yields.
- Tanemura, Kiyoshi,Suzuki, Tsuneo,Horaguchi, Takaaki
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- A unique structural distribution pattern discovered for the cerebrosides from starfish Asterias amurensis
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Cerebroside is an important family of the mono-glycosylated ceramides involved in the larger family of glycosphingolipid and sulfatide. Cerebroside is synthesized from ceramide by the transfer of glucose from UDP-glucose, and degraded back to ceramide, which plays an important role at the epidermis protecting interior of the body as a barrier. Because cerebroside is regarded as the source molecule of ceramide and is amphiphilic in nature, cerebroside is considered valuable as the ingredient of cosmetic lotion. Various sources can be considered as raw material of cerebrosides. Starfish is considered as one of such potent source. However, the structure of the ceramide part of cerebroside is not fully investigated. Therefore, the individual structures of cerebroside molecules need to be identified including sphingosine and fatty acyl group composition to assess the potential of the molecule. We investigated and determined the structures of cerebrosides in starfish Asterias amurensis using LC-MS, GC-MS, tandem mass spectrometry (MS/MS), and 1H NMR. We also discovered a characteristic structure distribution that was divided into three major groups: 1) a group composed of a relatively long sphingosine (C22) and a short length of fatty acyl group (less than C16), 2) a group composed of a typical C18 sphingosine and long fatty acyl groups (greater than C23), and 3) a group composed of C18 sphingosine and fatty acyl groups with their length less than C18. The calculated Log P values of cerebrosides ranging from 9 to 11 covered about 80% of the molecules that were in the range of those used in cosmetics, thus showing the potential usefulness of starfish Asterias amurensis as a source of raw material for cerebrosides.
- Yamaguchi, Ryosuke,Kanie, Yoshimi,Kanie, Osamu,Shimizu, Yoshitaka
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- Effects of Organic Modifiers on a Palladium Catalyst in the Competitive Hydrogenation of 1-Octene Versus Octanal: An Evaluation of Solid Catalysts with an Ionic Liquid Layer
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The competitive hydrogenation between 1-octene and octanal has been investigated with a ≈5% palladium on alumina catalyst prepared in situ with the following organic modifiers: pyridine, 1-methylimidazole, 1,3-dimethylimidazole methylsulfate, 1,3-dimethylimidazole bis(trifluoromethylsulfonyl)imide and methyltri-sec-butylphosphonium methylsulfate. The results of these investigations indicate that the ionic liquid modifiers have significant and specific effects on catalytic performance, for example, certain systems can completely suppress octanal conversion. In addition, analytical techniques reveal that the matrix and quantity of organic species on the used catalysts are different if different ionic liquids are used as modifiers. Surface studies also reveal that the modifiers have a noticeable effect on the crystallite size and chemisorption properties of the catalysts.
- Miller, Stuart F.,Friedrich, Holger B.,Holzapfel, Cedric W.,Dasireddy, Venkata D. B. C.
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- Hydroboration. 59. Thexylchloroborane-Methyl Sulfide. A New Stable Monohydroborating Agent with Exceptional Regioselectivity
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Under selected conditions, the hydroboration of 2,3-dimethyl-2-butene with 1 equiv of BH2Cl*SMe2 proceeds cleanly in solution (CH2Cl2, ClCH2CH2Cl, Et2O) or under neat conditions to give exclusively the monohydroboration product, thexylchloroborane-methyl sulfide (ThxBHCl*SMe2).Stock solutions of ThxBHCl*SMe2 in CH2Cl2 or Et2O have unusual thermal stability at ambient temperatures or below.The hydroboration of reactive olefins, such as terminal or unhindered disubstituted alkenes, with ThxBHCl*SMe2 proceeds quantitatively with high regiospecificity in CH2Cl2,ClCH2CH2Cl, Et2O, and THF to produce isomerically pure thexylalkylchloroborane intermediates.Subsequent oxidation produces the desired alcohols in nearly quantitative yield with high regiospecificity.With less reactive olefins, such as 1-methylcyclopentene, cyclohexene, or α-pinene, 11B NMR showed that the desired thexylalkylchloroborane products were contaminated with alkyldichloroborane species, indicating that a significant amount of product redistribution had occured.This was reflected in a lower observed regioselectivity in the hydroboration of some less reactive alkenes with ThxBHCl*SMe2.
- Brown, Herbert C.,Sikorski, James A.,Kulkarni, Surendra U.,Lee, Hsiupu D.
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- Highly active and selective platinum(0)-carbene complexes. Efficient, catalytic hydrosilylation of functionalised olefins
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Readily available N-heterocyclic platinum-carbene complexes 1 are highly efficient catalysts for the regioselective hydrosilylation of alkenes. These novel organometallics tolerate a wide range of functional and protecting groups, can be stored for prolonged periods of time and are particularly active (TON > 106).
- Marko, Istvan E.,Sterin, Sebastien,Buisine, Olivier,Berthon, Guillaume,Michaud, Guillaume,Tinant, Bernard,Declercq, Jean-Paul
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- OXIDATIVE CLEAVAGE OF SILICON-CARBON BOND WITH TRIMETHYLAMINE-N-OXIDE. NEW ACCESS TO PRIMARY ALCOHOLS AND ALDEHYDES FROM TERMINAL ALKENES AND ALKYNES
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Oxidative cleavage of carbon-silicon bond of organosilanes with trimethylamine-N-oxide is achieved under mild conditions.The reaction occurs chemoselectively irrespective of the presence of amino and thio groups to give formally anti-Markovnikov hydration product of 1-alkenes and 1-alkynes via hydrosilylation.
- Sakurai, Hideki,Ando, Masatomo,Kawada, Nobuo,Sato, Kazuhiko,Hosomi, Akira
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- Improving the catalytic behavior of Ni/Al2O3 by indium in reduction of carboxylic acid to alcohol
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Octanoic acid (OA) was used as reactant with medium chain length to model the aliphatic carboxylic acids which can be produced by catalytic, thermochemical or biological degradation of biomass. A flow through reactor was applied at 21 bar total pressure (in general 20 bar hydrogen and 1 bar octanoic acid partial pressures) and 240-360°C. Fatty acid conversion activity of alumina supported Ni catalysts and the yield of selectively produced alcohol can be increased drastically by In2O3 doping. Appearance of metallic indium can effectively direct the step by step catalytic reduction to alcohol formation over partly reduced Ni catalysts instead of chain shortening hydrodecarbonylation. On comparing a commercial, conventionally used Adkins catalyst (consisting of 72 wt.% CuCr2O4 and 28 wt.% CuO) and novel bimetallic alumina supported composite (InNi/Al2O 3) producing alcohol with high selectivity, the chromium-free, environmental benign hydrogenation catalyst seems to be much more active.
- Onyestyák, Gy?rgy,Harnos, Szabolcs,Kalló, Dénes
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- Regulation of Iron-Catalyzed Olefin Hydroboration by Ligand Modifications at a Remote Site
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An amide-derived N,N,N-Fe(II) complex catalyzes the hydroboration of alkenes at room temperature. Alkylation of a remote site on the ligand backbone was used as a late-stage modification to provide a more electrophilic complex as determined by electrochemical studies. The alkylated variant, compared to the parent complex, catalyzes olefin hydroboration with an increased reaction rate and exhibits distinct regioselectivity for internal alkene hydroboration. (Figure Presented).
- Tseng, Kuei-Nin T.,Kampf, Jeff W.,Szymczak, Nathaniel K.
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- Alkyne [2 + 2 + 2] Cyclotrimerization Catalyzed by a Low-Valent Titanium Reagent Derived from CpTiX3 (X = Cl, O- i-Pr), Me3SiCl, and Mg or Zn
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Inter-, partially intra-, and intramolecular [2 + 2 + 2] cycloadditions of alkynes were catalyzed by a low-valent titanium species generated in situ from the reduction of CpTi(O-i-Pr)3, CpTiCl3, or Cp?TiCl3 with Mg or Zn powder in the presence of Me3SiCl. The role of Me3SiCl as an additive in the reaction mechanism is discussed.
- Okamoto, Sentaro,Yamada, Takeshi,Tanabe, Yu-Ki,Sakai, Masaki
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- Amides as Nucleophiles: Reaction of Alkyl Halides with Amides or with Amides and Water. A New Look at an Old Reaction
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Heating of formamide with an alkyl halide (with or without water) affords a mild, nonhydrolytic, high-yield synthesis of alcohols and formate esters.Yet the way in which substitution on the alkyl halide actually occurs remains obscure.To explore this question, thermal reaction of 1-bromooctane (1a) with formamides (HC(O)NHR, R=H, Me; 2a, 2b) was studied quantitatively.Major products are 1-octanol (3) and n-octyl formate (5); minor products are 1-octene (4), di-n-octyl ether (6), and N-octylformamide (7, from 2a, only).Solid coproduct is HC(=NR)NHR + Br(1-) (e.g., 8a, R=H, methanimidamide hydrobromide).Analogously, 1a and N-methylformamide (2b) give alkylated products 3,5, and 6 along with 8b (R=Me). 1-Iodooctane (1b) reacts similarly.Probe samples show that 1-octanol (3) is first formed, followed by 5 and 6.Occurence of 8a-c is key to a mechanistic interpretation of the reaction.An imidate ("salt I"), e.g., from 1a and 2b, is first formed and reacts with amide 2b to give and 3.Now alcohol 3 is converted to ester 5 and 8b by reaction with this same formylamidine.Water, if present, adds to the imidate and gives a new tetrahedral intermediate that cleaves to ester 5 and amide salt, RNH3X.Analogous reaction steps are proposed to generate side products 4, 6, and 7.Alkylation of formamide by C6F13CH2CH2I (1c) is considerably slower and less efficient than alkylation by 1-bromooctane.This result stands in sharp contrast to fast, efficient reaction of 1c with N-methylformamide or with DMF and water.
- Brace, Neal O.
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- An efficient oxidative cleavage of carbon-silicon bonds by a dioxygen/hydroquinone system
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Carbon-silicon bonds in alkylalkoxysilanes readily undergo cleavage by dioxygen in the presence of hydroquinone derivatives to give the corresponding alcohols in good yields. The real oxidant is dry hydrogen peroxide generated in situ. The oxidation proceeds with complete retention of configuration at an sp3 carbon center.
- Tamao,Hayashi,Ito
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- H2-driven biotransformation of n-octane to 1-octanol by a recombinant Pseudomonas putida strain co-synthesizing an O2-tolerant hydrogenase and a P450 monooxygenase
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An in vivo biotransformation system is presented that affords the hydroxylation of n-octane to 1-octanol on the basis of NADH-dependent CYP153A monooxygenase and NAD+-reducing hydrogenase heterologously synthesized in a bacterial host. The hydrogenase sustains H2-driven NADH cofactor regeneration even in the presence of O2, the co-substrate of monooxygenase.
- Lonsdale, Thomas H.,Lauterbach, Lars,Honda Malca, Sumire,Nestl, Bettina M.,Hauer, Bernhard,Lenz, Oliver
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- Unveiling the dual role of the cholinium hexanoate ionic liquid as solvent and catalyst in suberin depolymerisation
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Disruption of the three-dimensional network of suberin in cork by cholinium hexanoate leads to its efficient and selective isolation. The reaction mechanism, which likely involves selective cleavage of some inter-monomeric bonds in suberin, was still unanswered. To address this question, the role of the ionic liquid during suberin depolymerisation and during cleavage of standard compounds carrying key chemical functionalities was herein investigated. A clear demonstration that the ionic liquid catalyses the hydrolysis of acylglycerol ester bonds was attained herein, both experimentally and computationally (DFT calculations). This behaviour is related to cholinium hexanoate capacity to activate the nucleophilic attack of water. The data showed also that the most favourable reaction is the hydrolysis of acylglycerol ester bonds, with the C2 position reporting the faster kinetics, whilst most of the linear aliphatic esters remained intact. The study emphasises that the ionic liquid plays the dual role of solvent and catalyst and leads to suberin efficient extraction through a mild depolymerisation. It is also one of the few reports of ionic liquids as efficient catalysts in the hydrolysis of esters.
- Ferreira, Rui,Garcia, Helga,Sousa, Andreia F.,Guerreiro, Marina,Duarte, Filipe J. S.,Freire, Carmen S. R.,Calhorda, Maria Jose,Silvestre, Armando J. D.,Kunz, Werner,Rebelo, Luis Paulo N.,Silva Pereira, Cristina
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- Influence of sorption to dissolved humic substances on transformation reactions of hydrophobic organic compounds in water. Part II: Hydrolysis reactions
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The effect of dissolved humic acid (HA) on two types of hydrolysis reactions was investigated: (I) dehydrochlorination of γ-hexachlorocyclohexane (HCH) and 1,1,2,2-tetrachloroethane (TeCA) as a reaction involving hydroxide ions (OH-) and (II) hydrolysis of 1-octyl acetate (OA) which is catalyzed by H+ at the applied pH value (pH 4.5). The rate of TeCA hydrolysis was not affected by addition of 2 g l-1 of HA at pH 10 (k′ = 0.33 h-1) but HCH hydrolysis was significantly inhibited (k′ = 4.6 × 10-3 h-1 without HA and 2.8 × 10-3 h-1 at 2 g l-1 HA). HCH is sorbed by 51% whereas TeCA sorption is insignificant at this HA concentration. Sorbed HCH molecules are effectively protected due to electrostatic repulsion of OH- by the net negative charge of the HA molecules. In contrast, OA hydrolysis at pH 4.5 (k′ = 1.6 × 10-5 h-1) was drastically accelerated after addition of 2 g l-1 HA (k′ = 1.1 × 10-3 h-1). The ratio of the pseudo-first-order rate constants of the sorbed and the freely dissolved ester fraction is about 70. H+ accumulation in the microenvironment of the negatively charged HA molecules was suggested to contribute to the higher reaction rate for the sorbed fraction in case of this H+-catalyzed reaction. Analogous effects from anionic surfactants are known as micellar catalysis.
- Georgi, Anett,Trommler, Ulf,Reichl, Annett,Kopinke, Frank-Dieter
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- MOF-derived Cu@C catalyst for the liquid-phase hydrogenation of esters
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MOF derived core-shell Cu@C was prepared by the pyrolysis of Cu-BTC and applied in the liquid-phase hydrogenation of ester. The severe aggregation of copper species was inhibited by the carbon shell. Compared with traditional Cu/AC-H2 catalyst, Cu@C-N2 displayed higher activity in the hydrogenation of butyl butyrate due to its higher Cu dispersion. Further reduction of Cu@C-N2 catalyst in H2 greatly improved the activity, as a result of the appropriate ratio of Cu+/Cu0, which can activate both ester and H2 molecules.
- Zhao, Yujun,Wu, Xiaoqian,Zhou, Jiahua,Wang, Yue,Wang, Shengping,Ma, Xinbin
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- Mild and efficient tetrahydropyranylation and deprotection of alcohols catalyzed by heteropoly acids
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A simple, mild and effective method to form 2-tetrahydropyranyl ethers of alcohols and phenol and the removal of this protective group in the presence of heteropoly acids as catalysts are described.
- Molnar, Arpad,Beregszaszi, Timea
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- Electrocatalytic hydrogenation of octyl aldehyde over Pd catalysts
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The electrocatalytic hydrogenation (ECH) of octyl aldehyde (octanal) to octyl alcohol (octan-1-ol) was investigated using commercial Pd/alumina catalysts in aqueous ethanol. The influence of different parameters, such as catalyst support, current intensity, polarity of solvent, supporting electrolyte, and octanal concentration, on the electrocatalytic hydrogenation of octanal was studied.
- Cirtiu, Ciprian M.,Menard, Hugues
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- Hydrolysis of Water-insoluble Esters by Octadecyl Immobilized H-ZSM-5 Catalyst in a Water-Toluene System
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In the hydrolysis of water-insoluble esters in a water-toluene system octadecyltrichlorosilane-treated ZSM-5, which floated at the interface of the two liquids, was observed to be a solid interface catalyst.
- Ogawa, Haruo,Tensai, Koh,Taya, Kazuo,Chihara, Teiji
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- A Remarkably Simple Class of Imidazolium-Based Lipids and Their Biological Properties
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A series of imidazolium salts bearing two alkyl chains in the backbone of the imidazolium core were synthesized, resembling the structure of lipids. Their antibacterial activity and cytotoxicity were evaluated using Gram-positive and Gram-negative bacteria and eukaryotic cell lines including tumor cells. It is shown that the length of alkyl chains in the backbone is vital for the antibiofilm activities of these lipid-mimicking components. In addition to their biological activity, their surface activity and their membrane interactions are shown by film balance and quartz crystal microbalance (QCM) measurements. The structure-activity relationship indicates that the distinctive chemical structure contributes considerably to the biological activities of this novel class of lipids. Lipids! A series of imidazolium salts bearing two alkyl chains in the backbone were synthesized, resembling the structure of lipids. The biological activity resulting from their surface activity and membrane interaction are shown (see figure), which were determined by the alkyl chain length.
- Wang, Da,Richter, Christian,Rühling, Andreas,Drücker, Patrick,Siegmund, Daniel,Metzler-Nolte, Nils,Glorius, Frank,Galla, Hans-Joachim
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- Selective Electroenzymatic Oxyfunctionalization by Alkane Monooxygenase in a Biofuel Cell
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Aliphatic synthetic intermediates with high added value are generally produced from alkane sources (e.g., petroleum) by inert carbon–hydrogen (C?H) bond activation using classical chemical methods (i.e. high temperature, rare metals). As an alternative approach for these reactions, alkane monooxygenase from Pseudomonas putida (alkB) is able to catalyze the difficult terminal oxyfunctionalization of alkanes selectively and under mild conditions. Herein, we report an electrosynthetic system using an alkB biocathode which produces alcohols, epoxides, and sulfoxides through bioelectrochemical hydroxylation, epoxidation, sulfoxidation, and demethylation. The capacity of the alkB binding pocket to protect internal functional groups is also demonstrated. By coupling our alkB biocathode with a hydrogenase bioanode and using H2 as a clean fuel source, we have developed and characterized a series of enzymatic fuel cells capable of oxyfunctionalization while simultaneously producing electricity.
- Abdellaoui, Sofiene,Chen, Hui,Kummer, Matthew J.,Malapit, Christian A.,Minteer, Shelley D.,You, Chun,Yuan, Mengwei
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- Novel hydroborating agents from Silylamine-boranes
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Exhibiting a broad spectrum of hydroboration reactivities, seven (7) new silylamine-borane complexes (1) were efficiently prepared from diborane and the corresponding silylated amines (2). Most are crystalline solids which are air-stable, concentrated borane sources. All provide convenient alternatives to other hydroborating agents, 2 undergoing complete hydrolysis to volatile and/or water soluble by-products upon aqueous work-up, thereby greatly facilitating the isolation of the borane-derived reaction products.
- Soderquist, John A.,Medina, Jesus R.,Huertas, Ramon
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- Asymmetric transformation of enones with Synechococcus sp. PCC 7942
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Asymmetric transformation of enones was investigated with cultured cells of Synechococcus sp. PCC 7942 (a cyanobacterium). The cells reduced both the endocyclic C-C double bond of s-trans enones and the exocyclic C-C double bond of s-cis enones with high enantioselectivity to afford optically active α-substituted (S)-ketones under illumination. In addition, the reduction of the double bond of these enones was accompanied by the formation of saturated alcohols. The cells preferentially reduced simple aliphatic ketones rather than cyclic ones to the corresponding (S)-alcohols with excellent enantioselectivity.
- Shimoda, Kei,Kubota, Naoji,Hamada, Hiroki,Yamane, Shin-Ya,Hirata, Toshifumi
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- Regiodivergent Reductive Opening of Epoxides by Catalytic Hydrogenation Promoted by a (Cyclopentadienone)iron Complex
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The reductive opening of epoxides represents an attractive method for the synthesis of alcohols, but its potential application is limited by the use of stoichiometric amounts of metal hydride reducing agents (e.g., LiAlH4). For this reason, the corresponding homogeneous catalytic version with H2 is receiving increasing attention. However, investigation of this alternative has just begun, and several issues are still present, such as the use of noble metals/expensive ligands, high catalytic loading, and poor regioselectivity. Herein, we describe the use of a cheap and easy-To-handle (cyclopentadienone)iron complex (1a), previously developed by some of us, as a precatalyst for the reductive opening of epoxides with H2. While aryl epoxides smoothly reacted to afford linear alcohols, aliphatic epoxides turned out to be particularly challenging, requiring the presence of a Lewis acid cocatalyst. Remarkably, we found that it is possible to steer the regioselectivity with a careful choice of Lewis acid. A series of deuterium labeling and computational studies were run to investigate the reaction mechanism, which seems to involve more than a single pathway.
- De Vries, Johannes G.,Gandini, Tommaso,Gennari, Cesare,Jiao, Haijun,Pignataro, Luca,Stadler, Bernhard M.,Tadiello, Laura,Tin, Sergey
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p. 235 - 246
(2022/01/03)
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- BiCl3-Facilitated removal of methoxymethyl-ether/ester derivatives and DFT study of -O-C-O- bond cleavage
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A simple method for the cleavage of methoxymethyl (MOM)-ether and ester derivatives using bismuth trichloride (BiCl3) is described. The alkyl, alkenyl, alkynyl, benzyl and anthracene MOM ether derivatives, as well as MOM esters of both aliphatic and aromatic carboxylic acids, were deprotected in good yields. To better understand the molecular roles of BiCl3and water for MOM cleavage, two possible binding pathways were investigated using the density functional theory (DFT) method. The theoretical results indicate the differential initial binding site preferences of phenolic and alcoholic MOM substrates to the Bi atom and suggest that water plays a key role in facilitating the cleavage of the MOM group.
- Pacherille, Angela,Tuga, Beza,Hallooman, Dhanashree,Dos Reis, Isaac,Vermette, Mélodie,Issack, Bilkiss B.,Rhyman, Lydia,Ramasami, Ponnadurai,Sunasee, Rajesh
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supporting information
p. 7109 - 7116
(2021/05/03)
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- Radical Chain Reduction via Carbon Dioxide Radical Anion (CO2?-)
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We developed an effective method for reductive radical formation that utilizes the radical anion of carbon dioxide (CO2?-) as a powerful single electron reductant. Through a polarity matched hydrogen atom transfer (HAT) between an electrophilic radical and a formate salt, CO2?- formation occurs as a key element in a new radical chain reaction. Here, radical chain initiation can be performed through photochemical or thermal means, and we illustrate the ability of this approach to accomplish reductive activation of a range of substrate classes. Specifically, we employed this strategy in the intermolecular hydroarylation of unactivated alkenes with (hetero)aryl chlorides/bromides, radical deamination of arylammonium salts, aliphatic ketyl radical formation, and sulfonamide cleavage. We show that the reactivity of CO2?- with electron-poor olefins results in either single electron reduction or alkene hydrocarboxylation, where substrate reduction potentials can be utilized to predict reaction outcome.
- Hendy, Cecilia M.,Jui, Nathan T.,Lian, Tianquan,Smith, Gavin C.,Xu, Zihao
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supporting information
p. 8987 - 8992
(2021/07/01)
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- KB3H8: An environment-friendly reagent for the selective reduction of aldehydes and ketones to alcohols
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Selective reduction of aldehydes and ketones to their corresponding alcohols with KB3H8, an air- and moisture-stable, nontoxic, and easy-to-handle reagent, in water and THF has been explored under an air atmosphere for the first time. Control experiments illustrated the good selectivity of KB3H8 over NaBH4 for the reduction of 4-acetylbenzaldehyde and aromatic keto esters. This journal is
- Li, Xinying,Mi, Tongge,Guo, Wenjing,Ruan, Zhongrui,Guo, Yu,Ma, Yan-Na,Chen, Xuenian
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supporting information
p. 12776 - 12779
(2021/12/10)
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- Synergistic Effect in Ir- or Pt-Doped Ru Nanoparticles: Catalytic Hydrogenation of Carbonyl Compounds under Ambient Temperature and H2Pressure
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Poly(vinylpyrrolidone) (PVP)-stabilized Ir- or Pt-doped (10 at. ?%) Ru NPs with the average diameters of 1.3-1.5 nm (RuIr or RuPt) were prepared by a coreduction of the corresponding metal precursors. RuIr and RuPt showed remarkable activity for the hydrogenation of aromatic, cyclic, and aliphatic carbonyl compounds at 30 °C under 0.2 MPa of H2, whereas the monometallic NPs of Ru, Ir, and Pt did not show any activity under the same conditions. In particular, RuPt converted the aliphatic aldehyde and cyclohexanone to the corresponding alcohols at 30 °C under atmospheric H2 pressure. Remarkable synergistic effects were ascribed to the provision of highly active sites for H2 and enhancement of the nucleophilicity of the adsorbed hydrides.
- Ichikuni, Nobuyuki,Masuda, Shinya,Matsuda, Shotaro,Takano, Shinjiro,Tsukuda, Tatsuya
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p. 10502 - 10507
(2021/08/31)
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- PROCESS FOR PRODUCING A CATALYST, CATALYST AND USE THEREOF
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A process for producing a supported catalyst comprising metal nanoparticles, said process comprises the following steps: (a) preparing a supported catalyst comprising metal nanoparticles; (b) peducing the catalyst of step (a); (c) treating the reduced catalyst of step (b) with at least one alcohol, and (d) calcining the treated catalyst of step (c) to remove carbon species, to produce said supported catalyst. A catalyst obtainable from this process can be used in amination, hydrogenation, dehydrogenation, hydrogenolysis and aerobic oxidation reactions.
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Page/Page column 13-15; 17
(2021/06/26)
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- Photocatalytic synthesis of phenols mediated by visible light using KI as catalyst
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A transition-metal-free hydroxylation of iodoarenes to afford substituted phenols is described. The reaction is promoted by KI under white LED light irradiation and uses atmospheric oxygen as oxidant. By the use of triethylamine as base and solvent, the corresponding phenols are obtained in moderate to good yields. Mechanistic studies suggest that KI and catalysis synergistically promote the cleavage of C-I bond to form free aryl radicals.
- Huiqin, Wei,Wu, Mei
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supporting information
(2021/11/30)
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- An asymmetric Salamo-based Zn complex supported on Fe3O4MNPs: a novel heterogeneous nanocatalyst for the silyl protection and deprotection of alcohols under mild conditions
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In this study, a magnetic asymmetric Salamo-based Zn complex (H2L = salen type di-Schiff bases)-supported on the surface of modified Fe3O4(Fe3O4@H2L-Zn) as a new catalyst was designed and characterizedvianumerous analytical techniques such as FT-IR spectroscopy, XRD, EDS, ICP-AES, SEM, TEM, TGA and VSM. An efficient and sustainable synthetic protocol has been presented for the synthesis of silyl ether substructuresviathe silyl protection of alcohols under mild conditions. The synthetic protocol involves a two-component solvent-free reaction between various hydroxyl-bearing substrates and hexamethyldisilazane (HMDS) as an inexpensive silylating agent using Fe3O4@H2L-Zn MNPs as a magnetically separable, recyclable and reusable heterogeneous catalyst. Fe3O4@H2L-Zn MNPs were also applied for the removal of silyl protecting groups from hydroxyl functions using water in CH2Cl2under green conditions. The catalyst demonstrated good to excellent catalytic yield efficiency for both the reactions compared to the commercial metal-based catalysts under green conditions for a wide range of substrates.
- Yao, Hongyan,Wang, Yongsheng,Razi, Maryam Kargar
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p. 12614 - 12625
(2021/04/14)
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- The effects of metals and ligands on the oxidation of n-octane using iridium and rhodium “PNP” aminodiphosphine complexes
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Ir and Rh “PNP” complexes with different ligands are utilized for the oxidation of n-octane. Based on the obtained conversion, selectivity, and the characterized recovered catalysts, it is found that the combination of Ir and the studied ligands does not promote the redox mechanism that is known to result in selective formation of oxo and peroxo compounds [desired species for C(1) activation]. Instead, they support a deeper oxidation mechanism, and thus higher selectivity for ketones and acids is obtained. In contrast, these ligands seem to tune the electron density around the Rh (in the Rh-PNP complexes), and thus result in a higher n-octane conversion and improved selectivity for the C(1) activated products, with minimized deeper oxidation, in comparison to Ir-PNP catalysts.
- Naicker, Dunesha,Alapour, Saba,Friedrich, Holger B
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p. 282 - 289
(2020/12/01)
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- Flexible pincer backbone revisited: CuSNS complexes as efficient catalysts in paraffin oxidation
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New Cu(II) complexes containing a set of tridentate hybrid SNS ligands were synthesised and fully characterised by IR, HRMS, elemental analysis and single-crystal X-ray diffraction. The complexes with the general formula Cu[bis(Rthioethyl)phenylamine]Cl2 (1); [R = methyl (a); ethyl (b); butyl (c); cyclohexyl (d) and t-butyl (e)] exhibited five-coordinate trigonal bipyramidal geometry around each Cu(II) centre in the solid-state with the S-donor atoms occupying the axial positions. However, complex 1b crystallised as a dimer bridged through a cuprate anion denoted as [1b(μ-CuCl4)1b]. Their application as catalysts in the oxidation of n-octane with hydrogen peroxide (H2O2) as an oxidant gave high substrate conversions to C-8 oxygenate products, mainly octanols, after reduction with PPh3. Notably, complex 1d produced the highest yield of 57% in 1 h reaction time at a catalyst concentration of 1 mol%. In general, high turnover numbers (2830–3180) were recorded for the 1/H2O2 catalytic systems with substantially high combined selectivity of 22–27% to 1-octanol and octanoic acid, which are the more desired products of n-octane oxidation resulting from its terminal carbon (C(1)) activation. The high activity of the catalysts is attributed to metal–ligand cooperative catalysis involving CuII-OOH intermediates as the active species modulated by the tridentate SNS ligands. In comparison with related complexes bearing N-donor atoms, the excellent catalytic performance of these series of CuSNS complexes highlights the critical role of the phenylamine N-donor atom.
- Bala, Muhammad D.,Friedrich, Holger B.,Soobramoney, Lynette
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supporting information
(2021/07/16)
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- Reactions between lithiated 1,3-dithiane oxides and trialkylboranes
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Various 2-substituted-1,3-dithiane oxides (1-oxide and 1,3-dioxide) have been metalated and reacted for the first time with a trialkylborane (trioctylborane). The 2-chloro-1,3-dioxide results in migration of an octyl group from boron to carbon with the displacement of chloride and gives nonanoic acid after oxidation, but there is no evidence for a second migration involving displacement of a sulfenate group. The reaction involving lithiation of the 2-methoxy-1-oxide results in two migrations, with the displacement of both the methoxy group and the thiolate unit of the dithiane ring, giving dioctyl ketone after oxidation, but the yield is low, primarily because thiophilic addition of the lithiating agent predominates over lithiation. Again, there is no evidence for the displacement of the sulfenate unit. However, the intermediate prior to oxidation can be treated with trifluoroacetic anhydride to induce a Pummerer rearrangement, and the presumed trifluoroacetoxyalkylthiolate group then acts as a novel leaving group and is displaced, resulting in trioctylmethanol on oxidation, but the yield is again very low.
- El-Hiti, Gamal A.,Elliott, Mark C.,Saleh, Basil A.,Smith, Keith
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p. 591 - 603
(2021/09/22)
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- Blacklight-Induced Hydroxylation of Arylboronic Acids Leading to Hydroxyarenes Using Molecular Oxygen and Tetrabutylammonium Borohydride
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A new simple protocol for the conversion of arylboronic acids to hydroxyarenes was achieved using molecular oxygen in the presence of tetrabutylammonium borohydride under blacklight irradiation (360 nm). A radical chain mechanism in which a superoxide ion (O2?.) plays a key role is proposed.
- Kawamoto, Takuji,Ryu, Ilhyong
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- Enantiomeric synthesis of natural alkylglycerols and their antibacterial and antibiofilm activities
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Alkylglycerols (AKGs) are bioactive natural compounds that vary by alkyl chain length and degree of unsaturation, and their absolute configuration is 2S. Three AKGs (5l–5n) were synthesised in enantiomerically pure form, and were characterised for the first time together with 12 other known and naturally occurring AKGs (5a–5k, 5o). Their structures were established using 1H and 13C APT NMR with 2D-NMR, ESI-MS or HRESI-MS and optical rotation data, and they were tested for their antibacterial and antibiofilm activities. AKGs 5a–5m and 5o showed activity against five clinical isolates and P. aeruginosa ATCC 15442, with MIC values in the range of 15–125 μg/mL. In addition, at half of the MIC, most of the AKGs reduced S. aureus biofilm formation in the range of 23%–99% and P. aeruginosa ATCC 15442 biofilm formation in the range of 14%–64%. The antibiofilm activity of the AKGs assessed in this work had not previously been studied.
- Fernández Montoya, Deicy J.,Contreras Jordan, Luis A.,Moreno-Murillo, Bárbara,Silva-Gómez, Edelberto,Mayorga-Wandurraga, Humberto
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supporting information
p. 2544 - 2550
(2019/11/13)
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- Chemoselective Cleavage of Si-C(sp3) Bonds in Unactivated Tetraalkylsilanes Using Iodine Tris(trifluoroacetate)
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Organosilanes are synthetically useful reagents and precursors in organic chemistry. However, the typical inertness of unactivated Si-C(sp3) bonds under conventional reaction conditions has hampered the application of simple tetraalkylsilanes in organic synthesis. Herein we report the chemoselective cleavage of Si-C(sp3) bonds of unactivated tetraalkylsilanes using iodine tris(trifluoroacetate). The reaction proceeds smoothly under mild conditions (-50 °C to room temperature) and tolerates various polar functional groups, thus enabling subsequent Tamao-Fleming oxidation to provide the corresponding alcohols. NMR experiments and density functional theory calculations on the reaction indicate that the transfer of alkyl groups from Si to the I(III) center and the formation of the Si-O bond proceed concertedly to afford an alkyl-λ3-iodane and silyl trifluoroacetate. The developed method enables the use of unactivated tetraalkylsilanes as highly stable synthetic precursors.
- Matsuoka, Keitaro,Komami, Narumi,Kojima, Masahiro,Mita, Tsuyoshi,Suzuki, Kimichi,Maeda, Satoshi,Yoshino, Tatsuhiko,Matsunaga, Shigeki
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supporting information
p. 103 - 108
(2021/01/13)
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- Sodium Aminodiboranate, a New Reagent for Chemoselective Reduction of Aldehydes and Ketones to Alcohols
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Sodium aminodiboranate (NaNH 2(BH 3) 2, NaADBH) is a new member of the old borane family, which exhibits superior performance in chemoselective reduction. Experimental results show that NaADBH can rapidly reduce aldehydes and ketones to the corresponding alcohols in high efficiency and selectivity under mild conditions. There are little steric and electronic effects on this reduction.
- Wang, Jin,Guo, Yu,Li, Shouhu,Chen, Xuenian
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supporting information
p. 1104 - 1108
(2021/05/25)
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- Catalytic enantioselective addition of alkylzirconium reagents to aliphatic aldehydes
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A catalytic methodology for the enantioselective addition of alkylzirconium reagents to aliphatic aldehydes is reported here. The versatile and readily accessible chiral Ph-BINMOL ligand, in the presence of Ti(OiPr)4 and a zinc salt, facilitates the reaction, which proceeds under mild conditions and is compatible with functionalized nucleophiles. The alkylzirconium reagents are conveniently generated in situ by hydrozirconation of alkenes with the Schwartz reagent. This work is a continuation of our previous work on aromatic aldehydes.
- Carter, Nicholas,González-Soria, María José,Maciá, Beatriz,Vaccari, Jade
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- Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
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A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
- Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
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supporting information
p. 18591 - 18598
(2021/06/28)
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- A New Protocol for Catalytic Reduction of Alkyl Chlorides Using an Iridium/Bis(benzimidazol-2′-yl)pyridine Catalyst and Triethylsilane
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The reduction of alkyl chlorides using triethylsilane is investigated. Primary, secondary, tertiary, and benzylic C-Cl bonds are effectively converted into C-H bonds using an [IrCl(cod)] 2/2,6-bis(benzimidazol-2′-yl)pyridine catalyst system. This catalyst system is quite simple since the tridentate N-ligand can be easily prepared in one step from commercially available reagents.
- Fukuyama, Takahide,Hamada, Yuki,Ryu, Ilhyong
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p. 3404 - 3408
(2021/07/14)
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- Selective hydroboration of equilibrating allylic azides
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The iridium(i)-catalyzed hydroboration of equilibrating allylic azides is reported to provide only the anti-Markovnikov product of alk-1-ene isomers in good yields and with good functional group tolerance.
- Liu, Ruzhang,Xu, Jun,Zhang, Yuanyuan
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supporting information
p. 8913 - 8916
(2021/09/13)
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- A study of the mechanism of triglyceride hydrodeoxygenation over alumina-supported and phosphatized-alumina-supported Pd catalysts
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The mechanism of catalytic hydrodeoxygenation (HDO) of fats, vegetable oils, and fatty acids was studied using alumina-supported Pd catalysts and tricaprylin and valeric acid as model reactants. The chemistry of fatty acid/catalyst interaction was studied by quasi-operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The Pd/γ–Al2O3 catalyst showed good activity in the hydrogenolysis reaction of the ester bonds to convert tricaprylin to caprylic acid, but they were of poor activity in the consecutive hydrodeoxygenation (HDO) of the acid to paraffin. The surface modification of the support alumina by phosphate groups significantly increased the HDO activity of the Pd catalyst and, consequently, the paraffin yield. The activity change was accounted partly for the partial replacement of the weak base Al–OH groups by weak acid P–OH groups but mainly for the partial elimination of Lewis acid (Al⊕) – Lewis base (O?) pair sites on the surface of the support. Both surface Al–OH and P–OH groups were shown to participate in the reaction with carboxylic acid and formed bidentate surface carboxylate species, which further reacted with hydrogen to give paraffin. Carboxylates of less basic surface sites were found to be more prone to HDO reaction than those of strong base sites. Monodentate carboxylates, formed on Al⊕ O? pair sites were of low reactivity. Phosphatizing eliminated most of the Lewis type acid-base pair sites, therefore, reactive bidentate carboxylates represented the most abundant surface intermediate (MASI) during the HDO reaction of triglyceride. The hydroxyl coverage of the carboxylated surface was shown to become somewhat higher under steady-state reaction conditions. The increased hydroxyl coverage implies that C–O bond hydrogenolysis of the surface carboxylate proceeds, regenerating OH groups and forming aldehyde that could be intermediate of paraffin formation.
- Barthos, Róbert,Domján, Attila,Hancsók, Jen?,Lónyi, Ferenc,Mihályi, Magdolna R.,Novodárszki, Gyula,Solt, Hanna E.,Valyon, József,Vikár, Anna
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- Production of γ-Valerolactone from One-Pot Transformation of Biomass-Derived Carbohydrates Over Chitosan-Supported Ruthenium Catalyst Combined with Zeolite ZSM-5
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It remains as a challenge to directly transform the biomass-derived C5 carbohydrates, such as furfural (FF) and its upstream product xylose and hemicellulose, to γ-valerolactone (GVL), a versatile renewable chemical platform, due to various restrictions in the current synthetic strategies. Using formic acid as green hydrogen source, we synthesized the recyclable chitosan-Ru/PPh3 catalyst system, effective for both the hydrogenation of FF to furfuryl alcohol (FAL) and the reduction of levulinic acid (LA) or ethyl levulinate (EL) to GVL, affording up to 99 % product yields. The combination of chitosan-Ru/PPh3 with ZSM-5 could successfully achieve up to 79 % yield of GVL from one-pot conversion of FF under mild condition. Preliminary studies indicated that this method could also be applied to the direct conversion of biomass-derived C5 carbohydrates such as xylose and hemicellulose to GVL in 37 % or 30 % yield, respectively.
- Wang, Tianlong,He, Jianghua,Zhang, Yuetao
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p. 1611 - 1619
(2020/03/04)
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- 1-D manganese(ii)-terpyridine coordination polymers as precatalysts for hydrofunctionalisation of carbonyl compounds
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Reductive catalysis with earth-abundant metals is currently of increasing importance and shows potential in replacing precious metal catalysis. In this work, we revealed catalytic hydroboration and hydrosilylation of ketones and aldehydes achieved by a structurally defined manganese(ii) coordination polymer (CP) as a precatalyst under mild conditions. The manganese-catalysed methodology can be applied to a range of functionalized aldehydes and ketones with turnover numbers (TON) of up to 990. Preliminary results on the regioselective catalytic hydrofunctionalization of styrenes by the Mn-CP catalyst are also presented.
- Johnson, Jahvon,Li, Sihan,Mo, Zixuan,Neary, Michelle C.,Zeng, Haisu,Zhang, Guoqi,Zheng, Shengping
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p. 2610 - 2615
(2020/03/05)
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- Chemoenzymatic Synthesis of 5-Hydroxymethylfurfural (HMF)-Derived Plasticizers by Coupling HMF Reduction with Enzymatic Esterification
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Biobased plasticizers, as substitutes for phthalates, have been synthesized from 5-hydroxymethylfurfural (HMF) and carboxylic acids (or esters) through a chemoenzymatic cascade process that involves as its first step the reduction of 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan (BHMF), followed by the esterification of BHMF with carboxylic acids (or esters) by using a supported lipase (Novozym 435). The reduction of HMF into BHMF is performed by using monodisperse metallic Co nanoparticles with a thin carbon shell (Co@C) with high activity and selectivity. After optimization of reaction conditions (temperature, hydrogen pressure, and solvent), it is possible to achieve 97 % conversion of HMF with 99 % selectivity to BHMF after 2 h reaction time. The reduction of HMF and esterification of BHMF using carboxylic acids or vinyl esters as acyl donors by lipase are optimized separately in batch and in fixed-bed continuous reactors. The coupling of two flow reactors (for reduction and subsequent esterification) working under optimized reaction conditions affords the diesters of BHMF in roughly 90 % yield with no loss of activity during 60 h of operation.
- Arias, Karen S.,Carceller, Jose M.,Climent, Maria J.,Corma, Avelino,Iborra, Sara
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p. 1864 - 1875
(2020/03/11)
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- Catalytic Activity of a Zr MOF Containing POCOP-Pd Pincer Complexes
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A metal-organic framework assembled from POCOP-Pd pincer complex metallolinkers (1-PdBF4, Zr6O4(OH)4(L-PdMeCN)3(BF4)3, L = (2,6-(OPAr2)2C6H3, Ar = p-C6H4CO2-) has been generated via postsynthetic oxidative I-/BF4- ligand exchange with NOBF4. 1-PdBF4 catalyzes a range of organic transformations, including transfer hydrogenation of unsaturated organic substrates, terminal alkyne hydration, and intramolecular hydroarylation of alkynes. The homogeneous analogue, tBu4POCOP-PdBF4, shows poor catalytic activity for transfer hydrogenation and alkyne hydration and decomposes under the catalytic reaction conditions. Solubility limitations and catalyst deactivation pathways observed for the homogeneous pincer complex propound the advantages of using porous solid supports to immobilize organometallic species.
- Kassie, Abebu A.,Wade, Casey R.
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p. 2214 - 2221
(2020/07/06)
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- MPV reduction of ethyl levulinate to γ-valerolactone by the biomass-derived chitosan-supported Zr catalyst
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Herein, we used the biopolymer chitosan as a support to synthesize a biomass-derived catalyst (chitosan-Zr) to achieve GVL in 97% yield from MPV reduction of EL, by using isopropanol as a hydrogen source. The catalyst system is also applicable to the reduction of various organic compounds with carbonyl groups. Additionally, we have proposed a possible mechanism for this reaction based on the systematic investigation towards the reaction. Moreover, the recycle and reuse experiment showed that this chitosan-Zr exhibited long-life catalytic performance and can maintain its high catalytic performance even after five runs of recycle and reuse experiments.
- Wang, Tianlong,Xu, Hai,He, Jianghua,Zhang, Yuetao
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p. 14686 - 14694
(2020/09/21)
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- Highly selective tetrahydropyranylation/dehydropyranylation of alcohols and phenols using porous phenolsulfonic acid-formaldehyde resin catalyst under solvent-free condition
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An efficient protocol for solvent-free chemoselective tetrahydropyranylation/depyranylation of alcohols and phenols is reported herein using mesoporous Phenolsulfonic Acid Formaldehyde Resins as a heterogeneous acid catalyst. The catalyst successfully performed chemoselective protection and deprotection reactions of a wide range of substrates ranging from primary to secondary and tertiary alcohols and also phenols. The reactions were carried out at ambient temperature under solvent-free condition (SolFC) which resulted in high yields within a very short time. FT-IR, TEM, SEM, EDS and TG-DSC analysis techniques were employed to characterize the synthesized polymeric catalyst. The chemoselective nature of our method was confirmed using 13C DEPT-135 NMR studies. The polymer catalyst was found to be recoverable even after 10th catalytic cycle without much depreciation in its activity. The heterogeneity of the catalyst was verified by hot filtration method. Good yield, energy and cost- effective method, solvent-free protocol, mild reaction conditions, no inert atmosphere, metal-free heterogeneous polymer catalyst and excellent recoverability of the catalyst are notable milestones of the reported protocol.
- Rajkumari, Kalyani,Laskar, Ikbal Bahar,Kumari, Anupama,Kalita, Bandita,Rokhum, Lalthazuala
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- Synthesis of Branched Biolubricant Base Oil from Oleic Acid
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The mature manufacturing of synthetic lubricants (poly-α-olefins, PAO) proceeds through oligomerization, polymerization, and hydrogenation reactions of petrochemical ethylene. In this work, we utilize the inexpensive bio-derived oleic acid as raw material to synthesize a crotch-type C45 biolubricant base oil via a full-carbon chain synthesis without carbon loss. It contains several cascade chemical processes: oxidation of oleic acid to azelaic acid (further esterification to dimethyl azelate) and nonanoic acid (both C9 chains). The latter is then selectively hydrogenated to nonanol and brominated to the bromo-Grignard reagent. In a next step, a C45 biolubricant base oil is formed by nucleophilic addition (NPA) of excessive C9 bromo-Grignard reagent with dimethyl azelate, followed by subsequent hydrodeoxygenation. The specific properties of the prepared biolubricant base oil are almost equivalent to those of the commercial lubricant PAO6 (ExxonMobil). This process provides a new promising route for the production of value-added biolubricant base oils.
- Chen, Shuang,Wu, Tingting,Zhao, Chen
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p. 5516 - 5522
(2020/09/07)
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- Bench-Stable Manganese NHC Complexes for the Selective Reduction of Esters to Alcohols with Silanes
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Selective reduction of esters to alcohols was accomplished through Mn(I)-mediated hydrosilylation reaction. The manganese tricarbonyl complex [Mn(bis-NHC)(CO)3Br] resulted an active pre-catalyst for the reduction of a variety of esters using phenylsilane and the cheap and readily available polymethylhydrosiloxane. An in situ examination of the catalytic reaction using 55Mn NMR spectroscopy allowed us to detect the formation of Mn(I) intermediate active species. (Figure presented.).
- Sousa, Sara C. A.,Realista, Sara,Royo, Beatriz
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p. 2437 - 2443
(2020/04/30)
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- Chemoselective Oxidation of p-Methoxybenzyl Ethers by an Electronically Tuned Nitroxyl Radical Catalyst
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The oxidation of p-methoxy benzyl (PMB) ethers was achieved using nitroxyl radical catalyst 1, which contains electron-withdrawing ester groups adjacent to the nitroxyl group. The oxidative deprotection of the PMB moieties on the hydroxy groups was observed upon treatment of 1 with 1 equiv of the co-oxidant phenyl iodonium bis(trifluoroacetate) (PIFA). The corresponding carbonyl compounds were obtained by treating the PMB-protected alcohols with 1 and an excess of PIFA.
- Hamada, Shohei,Sugimoto, Koichi,Elboray, Elghareeb E.,Kawabata, Takeo,Furuta, Takumi
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supporting information
p. 5486 - 5490
(2020/07/24)
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- Application of new Ru (II) pyridine-based complexes in the partial oxidation of n-octane
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Tridentate and bidentate Ru (II) complexes were prepared through reaction of four pyridine-based ligands: pyCH2N(R)CH2py {R = propyl, tert-butyl, cyclohexyl and phenyl; py = pyridine} with the [(η6-C6H6)Ru(μ-Cl)Cl]2 dimer. Crystal structures of the new terdentate Ru (II) complexes [Ru{pyCH2N(R)CH2py}C6H6](PF6)2 (R = C3H7 (1), C (CH3)3 (2), C6H11 (3) and the bidentate Ru (II) complex [Ru{pyCH2N(R)}C6H6]PF6 (R = C6H5 (4)) are reported. It was found that complexes 1, 2, 3 and 4 crystallised as mono-metallic species, with a piano stool geometry around each Ru centre. All complexes were active in the selective oxidation of n-octane using t-BuOOH and H2O2 as oxidants. Complexes 2 and 4 reached a product yield of 12% with t-BuOOH as oxidant, however, superior yields (23–32%) were achieved using H2O2 over all systems. The selectivity was predominantly towards alcohols (particularly 2-octanol) over all complexes using t-BuOOH and H2O2 after reduction of the formed alkylhydroperoxides in solution by PPh3. High TONs of up to 2400 were achieved over the Ru/H2O2 systems.
- Chanerika, Revana,Friedrich, Holger B.,Shozi, Mzamo L.
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- Erbium-Catalyzed Regioselective Isomerization-Cobalt-Catalyzed Transfer Hydrogenation Sequence for the Synthesis of Anti-Markovnikov Alcohols from Epoxides under Mild Conditions
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Herein, we report an efficient isomerization-transfer hydrogenation reaction sequence based on a cobalt pincer catalyst (1 mol %), which allows the synthesis of a series of anti-Markovnikov alcohols from terminal and internal epoxides under mild reaction conditions (≤55 °C, 8 h) at low catalyst loading. The reaction proceeds by Lewis acid (3 mol % Er(OTf)3)-catalyzed epoxide isomerization and subsequent cobalt-catalyzed transfer hydrogenation using ammonia borane as the hydrogen source. The general applicability of this methodology is highlighted by the synthesis of 43 alcohols from epoxides. A variety of terminal (23 examples) and 1,2-disubstituted internal epoxides (14 examples) bearing different functional groups are converted to the desired anti-Markovnikov alcohols in excellent selectivity and yields of up to 98%. For selected examples, it is shown that the reaction can be performed on a preparative scale up to 50 mmol. Notably, the isomerization step proceeds via the most stable carbocation. Thus, the regiochemistry is controlled by stereoelectronic effects. As a result, in some cases, rearrangement of the carbon framework is observed when tri-and tetra-substituted epoxides (6 examples) are converted. A variety of functional groups are tolerated under the reaction conditions even though aldehydes and ketones are also reduced to the respective alcohols under the reaction conditions. Mechanistic studies and control experiments were used to investigate the role of the Lewis acid in the reaction. Besides acting as the catalyst for the epoxide isomerization, the Lewis acid was found to facilitate the dehydrogenation of the hydrogen donor, which enhances the rate of the transfer hydrogenation step. These experiments additionally indicate the direct transfer of hydrogen from the amine borane in the reduction step.
- Liu, Xin,Longwitz, Lars,Spiegelberg, Brian,T?njes, Jan,Beweries, Torsten,Werner, Thomas
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p. 13659 - 13667
(2020/11/30)
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- Selective Room-Temperature Hydrogenation of Amides to Amines and Alcohols Catalyzed by a Ruthenium Pincer Complex and Mechanistic Insight
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We report a room-temperature protocol for the hydrogenation of various amides to produce amines and alcohols. Compared with most previous reports for this transformation, which use high temperatures (typically, 100-200 °C) and H2 pressures (10-100 bar), this system proceeds under extremely mild conditions (RT, 5-10 bar of H2). The hydrogenation is catalyzed by well-defined ruthenium-PNNH pincer complexes (0.5 mol %) with potential dual modes of metal-ligand cooperation. An unusual Ru-amidate complex was formed and crystallographically characterized. Mechanistic investigations indicate that the room-temperature hydrogenation proceeds predominantly via the Ru-N amido/amine metal-ligand cooperation.
- Ben-David, Yehoshoa,Kar, Sayan,Kumar, Amit,Leitus, Gregory,Milstein, David,Rauch, Michael
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p. 5511 - 5515
(2020/07/21)
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- Method for preparing alcohol and phenol through aerobic hydroxylation reaction of boric acid derivative in absence of photocatalyst
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The invention discloses a method for preparing alcohol and phenol through aerobic hydroxylation reaction of a boric acid derivative in the absence of a photocatalyst, wherein the boric acid derivativeis aryl boronic acid or alkyl boronic acid, and the corresponding target compounds are respectively a phenol-based compound and an alcohol-based compound. According to the method, by using a boric acid derivative as a reaction substrate, an additive is added under a solvent condition, and a hydroxylation reaction is performed under aerobic and illumination conditions to obtain a corresponding target compound. According to the invention, the new strategy is provided for the synthesis of phenols through aerobic hydroxylation of aryl boronic acid without a photocatalyst; the catalyst-free aerobic hydroxylation method for photocatalysis of aryl boronic acid or alkyl boronic acid by using triethylamine as an additive is firstly disclosed; and the new method has advantages of photocatalyst-freecondition, wide substrate range and good functional group compatibility.
- -
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Paragraph 0025-0028; 0030-0032
(2020/01/25)
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- Erratum: Redox-Noninnocent Ligand-Supported Vanadium Catalysts for the Chemoselective Reduction of C=X (X = O, N) Functionalities (Journal of the American Chemical Society (2019) 141:38 (15230-15239) DOI: 10.1021/jacs.9b07062)
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Pages 15232, 15233, and 15236. In the original paper, the doublet wave functions for 21 and 21a/21b were incorrectly (Figure Presented). reported as spin-contaminated in sections 2.3 and 2.8 (Figure 3 and Scheme 9, respectively.) This comes from the incorrectly reported expected eigenvalue of 0.75 for the spin-squared operator ??2? for the antiferromagnetically coupled doublet |↓?L|↑↑?V state (originally given in the Supporting Information). The correct expected eigenvalue for the |↓?L|↑↑?V state should be 1.75. The wave functions for 21 and 21a/21b (eigenvalues 1.79 and 1.77/1.66, respectively) are therefore not spincontaminated. The corrected Figure 3 and Scheme 9 are presented below. A corrected Supporting Information file is also provided. The corrections do not affect any of the conclusions of the Article, but slightly decrease the gap between the quartet and doublet spin surfaces. Scheme 3 has been also corrected to reflect the fact that (CH3)3SiCH2 ? radicals can only react based on spin conservation.
- Zhang, Guoqi,Wu, Jing,Zheng, Shengping,Neary, Michelle C.,Mao, Jincheng,Flores, Marco,Trovitch, Ryan J.,Dub, Pavel A.
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supporting information
p. 16507 - 16509
(2020/10/14)
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- Catalytic upgrading of ethanol to butanol over a binary catalytic system of FeNiOx and LiOH
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Catalytic conversion of ethanol to butanol is vital to bridge the gap between huge amounts of ethanol production, the limited blending ratio of ethanol in gasoline, and the outstanding performance of butanol. In this work, a highly active binary catalytic system of FeNiOx and LiOH was developed for upgrading of ethanol to butanol. After 24 h reaction at 493 K, the selectivity to butanol reached 71% with >90% high carbon alcohols at 28% ethanol conversion, which was comparable to the performance of some noble metal homogeneous catalysts.
- Li, Xianquan,Li, Xinsheng,Liu, Shimin,Pang, Jifeng,Wang, Junhu,Wang, Zhinuo,Zhang, Tao,Zheng, Mingyuan
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p. 672 - 678
(2020/01/28)
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- Chemoselective Epoxidation of Allyloxybenzene by Hydrogen Peroxide Over MFI-Type Titanosilicate
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The chemoselective synthesis of 2-(phenoxymethyl)oxirane from allyloxybenzene is achieved with over 90 % yield in a sustainable reaction system using titanium-substituted silicalite-1 (TS-1) as a catalyst, hydrogen peroxide (H2O2) as an oxidant, and a mixture of MeOH/MeCN as a solvent at 40 °C. No acid-catalyzed side reactions prompted by the Lewis acidity of the Ti active site in TS-1 are observed. The TS-1 catalyst can also promote the formation of oxiranes from various p-substituted allyloxybenzenes in good yields. The reaction mechanism is investigated through the reaction with other allyloxy compounds. The results, which are supported by DFT calculations, indicate that an active species of Ti peroxides formed from the reaction of TS-1 with H2O2 selectively oxidizes the allyloxybenzene to 2-(phenoxymethyl)oxirane.
- Fujitani, Tadahiro,Hong, Dachao,Ito, Satoru,Ji, Xinyi,Kon, Yoshihiro,Nakashima, Takuya,Osuga, Ryota,Sato, Kazuhiko,Yokoi, Toshiyuki
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supporting information
(2020/04/15)
-
- METHOD FOR PRODUCING ALIPHATIC LINEAR PRIMARY ALCOHOLS
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Provided are a method of preparing a linear primary alcohol, a catalyst for converting an α-olefin into an alcohol, and a method of converting an α-olefin into a linear primary alcohol, and the method of preparing a linear primary alcohol according to the present invention includes: charging a reactor with a heterogeneous catalyst including a cobalt oxide and a Cn olefin (S1); bringing the heterogeneous catalyst including a cobalt oxide into contact with the Cn olefin (S2); and supplying the reactor with a synthetic gas to obtain a Cn+1 alcohol (S3).
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Paragraph 0100-0101; 0109
(2020/05/06)
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- In-Situ generation of surface-active HCo(CO)y like intermediate from gold supported on ion-promoted Co3O4 for induced hydroformylation-hydrogenation of alkenes to alcohols
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In this study, a greener and stable surface-active cobalt-carbonyl like specie [HCo(CO)y] was generated via H2 and CO spillover by gold on ion-promoted cobalt oxide. The supports and catalysts syntheses were based on inverse micelle and deposition-precipitation methods, respectively. The temperature-programmed reduction was used for optimization to obtain the best supports. The catalysts with activity (Co3O4 3O4 3O4 and Au loadings 10 percent 3O4 catalyst more active than the others and displayed excellent alcohol chemoselectivity with varying regioselectivity under milder reaction conditions. The reaction was assumed to take place via the formation of [HCo(CO)y] specie, as the active catalytic site of the catalyst. The enhanced catalytic performance was also ascribed to the low-temperature reducibility and surface basicity of the nanomaterials. The stability of the catalyst was evaluated by recycling, with its mesostructure retained after four cycles.
- Akinnawo, Christianah A.,Meijboom, Reinout,Mogudi, Batsile M.,Oseghale, Charles O.
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- Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to Cyclohexane Derivatives Using a Rh&at;SILP Catalyst
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Rhodium nanoparticles immobilized on an acid-free triphenylphosphonium-based supported ionic liquid phase (Rh&at;SILP(Ph3-P-NTf2)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO2, ionic liquid, nanoparticles) led to outstanding catalytic properties. In particular, intimate contact between the nanoparticles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh&at;SILP(Ph3-P-NTf2) catalyst was active for the hydrodeoxygenation of benzylic ketones under mild conditions, and the product distribution for non-benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh&at;SILP(Ph3-P-NTf2) catalyst opens the way to the production of a wide range of high-value cyclohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel–Crafts acylation products and lignin-derived aromatic ketones.
- Bordet, Alexis,Emondts, Meike,Leitner, Walter,Moos, Gilles
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supporting information
p. 11977 - 11983
(2020/06/02)
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- Iridium Complex-Catalyzed C2-Extension of Primary Alcohols with Ethanol via a Hydrogen Autotransfer Reaction
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The development of a C2-extension of primary alcohols with ethanol as the C2 source and catalysis by [Cp*IrCl2]2 (where Cp? = pentamethylcyclopentadiene) is described. This new extension system was used for a range of benzylic alcohol substrates and for aliphatic alcohols with ethanol as an alkyl reagent to generate the corresponding C2-extended linear alcohols. Mechanistic studies of the reaction by means of intermediates and deuterium labeling experiments suggest the reaction is based on hydrogen autotransfer.
- Kobayashi, Masaki,Itoh, Satoshi,Yoshimura, Keisuke,Tsukamoto, Yuya,Obora, Yasushi
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p. 11952 - 11958
(2020/10/23)
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- Hollow Carbon Sphere Nanoreactors Loaded with PdCu Nanoparticles: Void-Confinement Effects in Liquid-Phase Hydrogenations
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Nanoreactors with hollow structures have attracted great interest in catalysis research due to their void-confinement effects. However, the challenge in unambiguously unraveling these confinement effects is to decouple them from other factors affecting catalysis. Here, we synthesize a pair of hollow carbon sphere (HCS) nanoreactors with presynthesized PdCu nanoparticles encapsulated inside of HCS (PdCu?HCS) and supported outside of HCS (PdCu/HCS), respectively, while keeping other structural features the same. Based on the two comparative nanoreactors, void-confinement effects in liquid-phase hydrogenation are investigated in a two-chamber reactor. It is found that hydrogenations over PdCu?HCS are shape-selective catalysis, can be accelerated (accumulation of reactants), decelerated (mass transfer limitation), and even inhibited (molecular-sieving effect); conversion of the intermediate in the void space can be further promoted. Using this principle, a specific imine is selectively produced. This work provides a proof of concept for fundamental catalytic action of the hollow nanoreactors.
- Dong, Chao,Liu, Jian,Su, Panpan,Wang, Guang-Hui,Ye, Run-Ping,Yu, Qun
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supporting information
p. 18374 - 18379
(2020/08/19)
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- Non oxidative and oxidative dehydrogenation of: N -octane using FePO4: Effect of different FePO4phases on the product selectivity
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The activation of n-octane with O2 has been investigated over different phases of FePO4 which were formed under dehydrogenation and oxidative dehydrogenation (ODH) conditions. Catalytic reactions were done with the tridymite-like FePO4 catalyst which showed a high selectivity towards cracked products and carbon oxides. Under dehydrogenation conditions, tridymite phase FePO4 is transformed into the iron pyrophosphate phase (Fe2P2O7). Octenes, aromatics, C8 oxygenates, carbon oxides (COx) and cracked products were present in the product stream. The iron pyrophosphate phase, under oxidative dehydrogenation conditions, showed high selectivity towards cracked products and on regeneration (restoring of the catalytic activity) with molecular oxygen it transformed into the α-phase and quartz type phase. The regenerated catalyst (α-phase and quartz type phase) exhibited a higher selectivity to ODH products when compared to the fresh and deactivated (Fe2P2O7) catalysts. The transformation of both fresh and deactivated catalysts was evident at a temperature of 450 °C. Since the α-phase is the active phase under ODH conditions and transformations between the reduced and α-phase take place reversibly, this could explain the highest selectivity towards octenes within this temperature range. Fresh and regenerated catalysts showed steady state conversions with time under constant conditions, showing that phase transformations were mainly due to varying temperature and oxidative environment. Characterization results show that FePO4 contains fivefold coordinate Fe3+ in the regenerated and fresh catalysts, and this species is believed to be responsible for selective n-octane activation. The surface area, acidity and metal dispersion of the deactivated and regenerated catalyst showed lower values when compared to the fresh catalysts. The results obtained from M?ssbauer spectroscopy showed direct correlation with the XRD data as well as the TPR-TPO results in terms of the phase changes and oxidation state of the calcined, uncalcined, reduced and reoxidised catalyst. This journal is
- Bharuth-Ram, K.,Dasireddy, Venkata D. B. C.,Friedrich, Holger B.,Khan, Faiza B.,Singh, Sooboo
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p. 7591 - 7600
(2020/12/01)
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- A method of synthesis of primary alcohol (by machine translation)
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The invention discloses a method for synthesizing a primary alcohol, using transition metal catalysis, the use of isopropanol as a hydrogen source to synthesize primary alcohol, the reaction not only using a cheap, environmental protection of isopropanol as a hydrogen source and solvent, and has high yield, environmental protection and the like, so that the reaction has broad prospects for development. (by machine translation)
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Paragraph 0119; 0120; 0121; 0122; 0123
(2019/03/17)
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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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- Chemoselective transfer hydrogenation of aldehydes in aqueous media catalyzed by a well-defined iron(II) hydride complex
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Abstract: An iron(II) hydride PNP pincer complex is applied as catalyst for the chemoselective transfer hydrogenation of aldehydes using an aqueous solution of sodium formate as hydrogen source. A variety of aromatic, heteroaromatic, and aliphatic aldehydes could be reduced to the corresponding alcohols in good to excellent yields with a catalyst loading of 1.0?mol% at 80?°C and 1?h reaction time. If present, C–C double bonds remained unaffected in course of the reaction, even when they are conjugated to the carbonyl group of the aldehyde. The catalyst’s lifetime and activity could be improved when the reactions were conducted in an ionic liquid-based micro emulsion. Graphical abstract: [Figure not available: see fulltext.].
- Gorgas, Nikolaus,Ilic, Aleksandra,Kirchner, Karl
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p. 121 - 126
(2018/11/01)
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