- Efficient and Practical Transfer Hydrogenation of Ketones Catalyzed by a Simple Bidentate Mn?NHC Complex
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Catalytic reductions of carbonyl-containing compounds are highly important for the safe, sustainable, and economical production of alcohols. Herein, we report on the efficient transfer hydrogenation of ketones catalyzed by a highly potent Mn(I)?NHC complex. Mn?NHC 1 is practical at metal concentrations as low as 75 ppm, thus approaching loadings more conventionally reserved for noble metal based systems. With these low Mn concentrations, catalyst deactivation is found to be highly temperature dependent and becomes especially prominent at increased reaction temperature. Ultimately, understanding of deactivation pathways could help close the activity/stability-gap with Ru and Ir catalysts towards the practical implementation of sustainable earth-abundant Mn-complexes.
- van Putten, Robbert,Benschop, Joeri,de Munck, Vincent J.,Weber, Manuela,Müller, Christian,Filonenko, Georgy A.,Pidko, Evgeny A.
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- Synthesis, characterization and catalytic, cytotoxic and antimicrobial activities of two novel cyclotriphosphazene-based multisite ligands and their Ru(II) complexes
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Two novel cyclotriphosphazene ligands (2 and 3) bearing 3-oxypyridine groups and their corresponding Ru(II) complexes (4 and 5) were synthesized and their structures were characterized using Fourier transform infrared, 1H NMR and 31P
- irali, Digdem Erdener,Uyar, Zafer,Koyuncu, Ismail,Haciolu, Nurcihan
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- Asymmetric transfer hydrogenation of ketones catalyzed by rhenium complexes with chiral ferrocenylphosphane ligands
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We have prepared a series of new rhenium complexes containing chiral ferrocenyldiphosphane ligands of the Josiphos family, starting from commercially available rhenium sources. These new ReV oxido and nitrido complexes, several of which have been characterized by X-ray crystallography, are air- and moisture-stable and are active catalysts in the asymmetric transfer hydrogenation of ketones using 2-propanol as the hydrogen source in the presence of substoichiometric amounts of triethylamine (TEA). The reaction proceeds cleanly with good to excellent yields (50-99 %) but with moderate enantioselectivity (up to 58 % ee). A mechanism not involving hydridic species is proposed.
- Mejia, Esteban,Aardoom, Raphael,Togni, Antonio
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- Highly Active and Selective Manganese C=O Bond Hydrogenation Catalysts: The Importance of the Multidentate Ligand, the Ancillary Ligands, and the Oxidation State
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The replacement of expensive noble metals by earth-abundant transition metals is a central topic in catalysis. Herein, we introduce a highly active and selective homogeneous manganese-based C=O bond hydrogenation catalyst. Our catalyst has a broad substrate scope, it is able to hydrogenate aryl–alkyl, diaryl, dialkyl, and cycloalkyl ketones as well as aldehydes. A very good functional group tolerance including the quantitative and selective hydrogenation of a ketone in the presence of a non-shielded olefin is observed. In Mn hydrogenation catalysis, the combination of the multidentate ligand, the oxidation state of the metal, and the choice of the right ancillary ligand is crucial for high activity. This observation emphasizes an advantage and the importance of homogeneous catalysts in 3d-metal catalysis. For coordination compounds, fine-tuning of a complex coordination environment is easily accomplished in comparison to enzyme and/or heterogeneous catalysts.
- Kallmeier, Fabian,Irrgang, Torsten,Dietel, Thomas,Kempe, Rhett
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- Ruthenium complex based on [N,N,O] tridentate -2-ferrocenyl-2-thiazoline ligand for catalytic transfer hydrogenation
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A method for the synthesis of a new phosphine-free [N,N,O]-tridentate Schiff base ligand L1 using the 2-Ferrocenyl-2-thiazoline as scaffold was developed. The 1,2-disubstituted ferrocene-based ligand was assembled using as key strategy the directed ortho-metalation (DoM) in 2-ferrocenyl-2-thiazoline. L1 was successfully obtained in 83% of overall yield after two-step synthesis. The coordination ability of L1 towards Ru(II) was evidenced and the resulting complex was characterized by IR, UV-vis and EPR. Its catalytic performance was tested in transfer hydrogenation of a variety of substrates giving moderate to excellent conversions.
- Badillo-Gómez,Sánchez-Rodríguez,Toscano,Gouygou,Ortega-Alfaro,López-Cortés
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- Chiral Imidazo[1,5- a]pyridine-Oxazolines: A Versatile Family of NHC Ligands for the Highly Enantioselective Hydrosilylation of Ketones
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Herein we report the synthesis and application of a versatile class of N-heterocyclic carbene ligands based on an imidazo[1,5-a]pyridine-3-ylidine backbone that is fused to a chiral oxazoline auxiliary. The key step in the synthesis of these ligands involves the installation of the oxazoline functionality via a microwave-assisted condensation of a cyano-azolium salt with a wide variety of 2-amino alcohols. The resulting chiral bidentate NHC-oxazoline ligands form stable complexes with rhodium(I) that are efficient catalysts for the enantioselective hydrosilylation of structurally diverse ketones. The corresponding secondary alcohols are isolated in good yields (typically >90%) with good to excellent enantioselectivities (80-93% ee). The reported hydrosilylation occurs at ambient temperatures (40 °C), with excellent functional group tolerability. Even ketones bearing heterocyclic substituents (e.g., pyridine or thiophene) or complex organic architectures are hydrosilylated efficiently, which is discussed further in this report.
- Chinna Ayya Swamy,Varenikov, Andrii,Ruiter, Graham De
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- A ruthenium-grafted triazine functionalized mesoporous polymer: A highly efficient and multifunctional catalyst for transfer hydrogenation and the Suzuki-Miyaura cross-coupling reactions
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A new ruthenium-grafted mesoporous organic polymer Ru-MPTAT-1 has been synthesized via simple and facile in situ radical polymerization of 2,4,6-triallyloxy-1,3,5-triazine (TAT) in aqueous medium in the presence of an anionic surfactant (sodium dodecyl sulfate) as a template, followed by grafting of Ru(ii) onto its surface. Ru-MPTAT-1 has been characterized by elemental analysis, powder XRD, HRTEM, FT-IR, UV-vis DRS, TG-DTA, FESEM and XPS characterization tools. The Ru-MPTAT-1 material showed very good catalytic activity in the Suzuki-Miyaura cross-coupling reaction for aryl halides and transfer hydrogenation reaction for a series of carbonyl compounds. The catalyst is easily recoverable from the reaction mixture and can be reused several times without appreciable loss of catalytic activity in the above reactions. Highly dispersed and strongly bound Ru(ii) sites at the mesoporous polymer surface could be responsible for the observed high activity of the Ru-MPTAT-1 catalyst in these reactions.
- Salam, Noor,Kundu, Sudipta K.,Roy, Anupam Singha,Mondal, Paramita,Ghosh, Kajari,Bhaumik, Asim,Islam
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- Neutral Dinuclear Copper(I)-NHC Complexes: Synthesis and Application in the Hydrosilylation of Ketones
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The synthesis of a class of highly stable neutral dinuclear Cu(I)-NHC complexes using 1,2,4-triazole as a bridging ligand is described. Various NHCs were used to generate a library of [Cu(μ-trz)(NHC)]2 complexes. Interestingly, [Cu(μ-trz)(IPr)]2 was found to be highly active in the hydrosilylation of ketones, without the need for an external base or any other additive. A wide range of aryl and alkyl ketones, as well as sterically hindered ketones, was successfully reduced to alcohols using the lowest catalyst loading reported to date.
- Trose, Michael,Lazreg, Fa?ma,Chang, Tao,Nahra, Fady,Cordes, David B.,Slawin, Alexandra M. Z.,Cazin, Catherine S. J.
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- Reduction of ketones with silanes catalysed by a cyclopentadienyl- functionalised N-heterocyclic iron complex
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The well-defined piano-stool iron(II) complex (Cp-NHC)Fe(CO)I bearing a bidentate cyclopentadienyl-functionalised N-heterocyclic carbene ligand is shown to catalyse the reduction of ketones under mild conditions (1-2 h at room temperature) when combined with catalytic amounts of potassium tert-butoxide, and using Ph2SiH2 and the inexpensive and less reactive polymethylhydrosiloxane as reducing agents. The stoichiometric reaction of (Cp-NHC)Fe(CO)I with potassium tert-butoxide generates an iron-hydroxo complex, which seems to be the active species in the reduction of ketones.
- Lopes, Rita,Cardoso, Joao M.S.,Postigo, Lorena,Royo, Beatriz
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- Synthesis of aminoethanethiol trityl ether ligands for ruthenium-catalysed asymmetric transfer hydrogenation
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A series of chiral aminoethanethiol ethers was synthesised by the regioselective and stereospecific ring opening of the (R)- trityl(thiiranylmethyl)ether and examined in the hydrogen transfer reduction of different aromatic ketones. High conversions (>99%
- Harfouche, Joyce,Herault, Damien,Tommasino, M. Lorraine,Pellet-Rostaing, Stephane,Lemaire, Marc
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- Constructing reactive Fe and Co complexes from isolated picolyl-functionalized N-heterocyclic carbenes
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We report the isolation of free picolyl-functionalized N-heterocyclic carbenes (NHCs), which serve as versatile precursors to access low coordinate iron and cobalt complexes. The reactivities of these new iron and cobalt complexes towards catalytic hydrosilylation of ketones have also been explored. For example, low loadings (0.05-1 mol%) of a four-coordinate iron complex bearing two deprotonated picolyl-NHC ligands can effect the fast catalytic reduction of ketones using the inexpensive industrial byproduct polymethylhydrosiloxane (PMHS) as the reductant at ambient temperature.
- Liang, Qiuming,Liu, Nina Jiabao,Song, Datong
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- Iridium-catalyzed efficient reduction of ketones in water with formic acid as a hydride donor at low catalyst loading
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A highly efficient and chemoselective transfer hydrogenation of ketones in water has been successfully achieved with our newly developed catalyst. Simple ketones, as well as α- or β-functionalized ketones, are readily reduced. Formic acid is used as a traceless hydride source. At very low catalyst loading (S/C = 10:000 in most cases; S/C = 50:000 or 100:000 in some cases), the iridium catalyst is impressively efficient at reducing ketones in good to excellent yields. The TOF value can be as high as up to 26:000 mol mol-1 h-1. A variety of functional groups are well tolerated, for example, heteroaryl, aryloxy, alkyloxy, halogen, cyano, nitro, ester, especially acidic methylene, phenol and carboxylic acid groups.
- Liu, Ji-Tian,Yang, Shiyi,Tang, Weiping,Yang, Zhanhui,Xu, Jiaxi
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- Hydrogenation of Carbonyl Derivatives Catalysed by Manganese Complexes Bearing Bidentate Pyridinyl-Phosphine Ligands
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Manganese(I) catalysts incorporating readily available bidentate 2-aminopyridinyl-phosphine ligands achieve a high efficiency in the hydrogenation of carbonyl compounds, significantly better than parent ones based on more elaborated and expensive tridentate 2,6-(diaminopyridinyl)-diphosphine ligands. The reaction proceeds with low catalyst loading (0.5 mol%) under mild conditions (50 °C) with yields up to 96%. (Figure presented.).
- Wei, Duo,Bruneau-Voisine, Antoine,Chauvin, Téo,Dorcet, Vincent,Roisnel, Thierry,Valyaev, Dmitry A.,Lugan, No?l,Sortais, Jean-Baptiste
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- The remarkable solvent effect on Zn(OAc)2-Catalyzed Hydrosilylation of ketones
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The combination of Zn(OAc)2 and N,N-dimethylformamide was found to effectively hydrosilylate various ketones at room temperature. Furthermore, our protocol allows the chemoselective reduction of a formyl group in the presence of a ketone group.
- Ozasa, Hiroki,Kondo, Kazuhiro,Aoyama, Toyohiko
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- Commutative reduction of aromatic ketones to arylmethylenes/alcohols by hypophosphites catalyzed by Pd/C under biphasic conditions
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An efficient method is reported to reduce aromatic ketones selectively into arylmethylenes or alcohols with hypophosphites and Pd/C, depending on the selected conditions. This study could represent a promising alternative to the classical uses of standard hydrides or molecular hydrogen involved in reduction and deoxygenation procedures.
- Guyon, Carole,Baron, Marc,Lemaire, Marc,Popowycz, Florence,Métay, Estelle
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- Ruthenium phenylindenyl complex as an efficient transfer hydrogenation catalyst
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An efficient and green protocol for the transfer hydrogenation of carbonyl and imine compounds is presented. The transformations are catalysed by the inexpensive and easily synthesised complex [RuCl(PPh3)(3- phenylindenyl)]. Its catalytic activity was compared to that of the most commonly encountered ruthenium complexes in transfer hydrogenation reactions involving several protypical substrates. Copyright
- Manzini, Simone,Blanco, Cesar A. Urbina,Nolan, Steven P.
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- Hydrogenation of ketones with a manganese PN3P pincer pre-catalyst
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A catalytic hydrogenation of carbonyl derivatives with a manganese pre-catalyst has been developed. The key feature is the use of an air stable cationic manganese pre-catalyst bearing a tridendate ligand with a 2,6-(diaminopyridinyl)diphosphine scaffold. Under 50?bar of H2, at 130?°C, various ketones were reduced to the corresponding alcohols with moderate to good yield.
- Bruneau-Voisine, Antoine,Wang, Ding,Roisnel, Thierry,Darcel, Christophe,Sortais, Jean-Baptiste
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- Efficient transfer hydrogenation of carbonyl compounds catalyzed by selenophenolato hydrido iron(II) complexes
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Selenophenolato hydrido iron(II) complexes 1–3 cis-[(H)(SeAr)Fe(PMe3)4] (Ar = C6H5 (1), p-MeOC6H4 (2) and o-MeC6H4 (3)) could catalyze transfer hydrogenation of aldehydes and ketones. Among the three complexes, catalyst 1 exhibited the highest catalytic activity. The catalytic reactions took place under very mild conditions, using isopropanol as solvent and hydrogen source, tBuONa as base under 60–80 °C. This catalytic system has good tolerance for many functional groups, such as halides, C[dbnd]C double bonds, nitro groups and cyano groups at the phenyl ring of the substrates.
- Wang, Yangyang,Du, Zhengyin,Zheng, Tingting,Sun, Hongjian,Li, Xiaoyan
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- Heterogenized Wilkinson-type catalyst for transfer hydrogenation of carbonyl compounds
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Wilkinson's catalyst [RhCl(PPh3)3] was heterogenized on common silica by the use of a grafting/anchoring technique. The immobilized catalyst showed high activity and selectivity in transfer hydrogenation reactions of a range of carbonyl compounds in 2-propanol. Reactions carried out in 2-propanol at reflux afforded the corresponding alcohols in high yields in short reaction times. The heterogeneous feature of the catalyst allows for easy recovery and efficient reuse in the same reaction up to 5 times without any detectible loss of catalytic activity. Wilkinson's catalyst [RhCl(PPh 3)3] has been immobilized on silica through a monodentate phosphane ligand and used in the transfer hydrogenation of alkyl and aryl carbonyl compounds. The use of 2-propanol as both hydrogen donor and solvent allows for high yields of the corresponding alcohols under mild reaction conditions. The recyclability of this heterogenized Rh catalyst is also demonstrated.
- Bogar, Krisztian,Krumlinde, Patrik,Bacsik, Zoltan,Hedin, Niklas,Baeckvall, Jan-E.
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- Hydrosilylation of ketones: From metal-organic frameworks to simple base catalysts
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A convenient base-catalyzed hydrosilylation of aromatic ketones using inexpensive bases, such as 1M sodium hydroxide in methanol or sodium/potassium tert-butoxide, has been developed. Mild reaction conditions (room temperature, 1 h) successfully promote the hydrosilylation of a variety of ketones.
- Addis, Daniele,Zhou, Shaolin,Das, Shoubhik,Junge, Kathrin,Kosslick, Hendrik,Harloff, Joerg,Lund, Henrik,Schulz, Axel,Beller, Matthias
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- Core-shell structured mesoporous silica: A new immobilized strategy for rhodium catalyzed asymmetric transfer hydrogenation
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A core-shell structured heterogeneous rhodium catalyst exhibited excellent catalytic activity and enantioselectivity in asymmetric transfer hydrogenation of aromatic ketones in aqueous medium, which could be recovered easily and used repetitively twelve times without affecting obviously its enantioselectivity.
- Zhang, Huaisheng,Jin, Ronghua,Yao, Hui,Tang, Shuang,Zhuang, Jinglan,Liu, Guohua,Li, Hexing
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- Cyclometalated iridium complexes for transfer hydrogenation of carbonyl groups in water
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Cyclometalated iridium complexes are shown to be excellent catalysts for transfer hydrogenation of carbonyl compounds in water using formate as a hydrogen source. A wide range of ketones and aldehydes have been reduced at 0.05% catalyst loading with no need for any organic solvents. Solution pH is found to play a critical role, with acidic conditions needed for fast transfer hydrogenation.
- Wei, Yawen,Xue, Dong,Lei, Qian,Wang, Chao,Xiao, Jianliang
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- A simple and efficient catalytic method for the reduction of ketones
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A range of ketones was efficiently reduced in the presence of catalytic amounts of lithium isopropoxide in 2-propanol under microwave heating, with alcohol products being formed in yields up to 99%.
- Ekstroem, Jesper,Wettergren, Jenny,Adolfsson, Hans
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- LITHIUM ALUMINIUM HYDRIDE ON SILICA GEL - SELECTIVE REDUCTION OF KETONES AND CARBOXY ESTERS IN THE PRESENCE OF NITRO AND CYANO GROUPS
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Cyano and nitro groups were found not to be reduced by lithium aluminium hydride on silica gel and with the use of this reagent ketones and carboxy esters bearing cyano and nitro groups were successfully converted into the corresponding cyano and nitro alcohols.
- Kamitori, Yasuhiro,Hojo, Masaru,Masuda, Ryoichi,Inoue, Tatsuro,Izumi, Tatsuo
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- Asymmetric transfer hydrogenation of ketones promoted by manganese(I) pre-catalysts supported by bidentate aminophosphines
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A series of commercially available chiral amino-phosphines, in combination with Mn(CO)5Br, has been evaluated for the asymmetric reduction of ketones, using isopropanol as hydrogen source. With the most selective ligand, the corresponding manga
- Azouzi, Karim,Bruneau-Voisine, Antoine,Vendier, Laure,Sortais, Jean-Baptiste,Bastin, Stéphanie
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- Transfer hydrogenation of aldehydes and ketones catalyzed using an aminophosphinite POCNHpincer complex of Ni(ii)
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The aminophosphinite pincer complex (POCNH)NiBr was found to effectively catalyze the transfer hydrogenation of aldehydes and ketones with 2-propanol and KOtBu as a base, presenting a rare example of bifunctional nickel transfer hydrogenation catalysts. The transfer hydrogenation of aldehydes and ketones was found to be selective, tolerating a wide range of other functional groups, including those prone to reduction, such as esters, amides, alkenes, pyridines, and nitriles. The reactions were suggested to proceedviathe metal-ligand cooperative mechanism with an intermediacy of an amido (POCN)NiIIspecies.
- ?ztop?u, ?zgür,Hayrapetyan, Davit,Khalimon, Andrey Y.,Lyssenko, Konstantin A.,Segizbayev, Medet,Shakhman, Dinmukhamed
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- Synthesis, structural characterization and catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes bearing N,N,O pincer type benzoylhydrazone ligands
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The convenient synthesis of four new octahedral ruthenium(II) carbonyl benzoylhydrazone complexes of the general molecular formula [Ru(L)Cl(CO)(PPh3)] (where HL = substituted 2-acetylpyridine benzoylhydrazones; the H represents the dissociable
- Suganthy, Pandimuni Kalpaga,Prabhu, Rupesh Narayana,Sridevi, Venugopal Shanmugham
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- Manganese catalyzed asymmetric transfer hydrogenation of ketones
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The asymmetric transfer hydrogenation (ATH) of a wide range of ketones catalyzed by manganese complex as well as chiral PxNy-type ligand under mild conditions was investigated. Using 2-propanol as hydrogen source, various ketones could be enantioselectively hydrogenated by combining cheap, readily available [MnBr(CO)5] with chiral, 22-membered macrocyclic ligand (R,R,R',R')-CyP2N4 (L5) with 2 mol% of catalyst loading, affording highly valuable chiral alcohols with up to 95% ee.
- Zhang, Guang-Ya,Ruan, Sun-Hong,Li, Yan-Yun,Gao, Jing-Xing
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- Copper-catalyzed asymmetric hydrosilylation of ketones using air and moisture stable precatalyst Cu(OAc)2·H2O
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Air and moisture stable copper(II) salts can be used to catalyze the hydrosilylation of aromatic ketones. The combination of catalytic amounts of copper(II) acetate or copper(II) acetate monohydrate (Cu(OAc) 2·H2O) and BINAP in the p
- Lee, Dong-Won,Yun, Jaesook
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- Synthesis, structural characterization, electrochemistry and catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes containing tridentate benzoylhydrazone ligands
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Convenient synthesis of eight new octahedral ruthenium(II) carbonyl benzoylhydrazone complexes having the general molecular formula [Ru(L)(CO)(EPh3)2] (where E = P or As; H2L = benzoylhydrazone ligand, the two H's representing the two dissociable protons) has been described. The substituted benzoylhydrazone ligands behave as a dianionic tridentate O, N and O donors (L) and coordinates to ruthenium via the phenolate oxygen, the azomethine nitrogen and the deprotonated amide oxygen. The compositions of the complexes have been established by elemental analysis and spectral methods (FT-IR, 1H NMR, 13C NMR, UV-vis). The crystal structure of one of the complexes, [Ru(L2)(CO)(PPh3) 2] (2), has been solved by single crystal X-ray crystallography and it indicates the presence of a distorted octahedral geometry in these complexes. All the complexes exhibit metal-to-ligand charge transfer (MLCT) transitions in the visible region and display one quasi-reversible reduction and two irreversible oxidations. Further, the catalytic efficiency of the complexes has been investigated in the case of transfer hydrogenation of ketones to the corresponding secondary alcohols. The influence of base, reaction temperature and catalyst loading in transfer hydrogenation reaction was also evaluated. The complexes were found to be efficient catalysts with conversion up to 99.5% in presence of iso-propanol/KOH.
- Prabhu, Rupesh Narayana,Ramesh, Rengan
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- Chemoselective reduction of aldehydes and ketones by potassium diisobutyl-t-butoxy aluminum hydride (PDBBA)
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t-Butoxy derivatives of DIBALH [lithium diisobutyl-t-butoxyaluminum hydride (LDBBA), sodium diisobutyl-t-butoxyaluminum hydride (SDBBA), and potassium diisobutyl-t-butoxyaluminum hydride (PDBBA)] were examined as chemoselective reducing agents of carbonyl compounds. Among them, PDBBA was found to be the most efficient for the reduction of aldehydes and ketones to the corresponding alcohols in the presence of ester, amide, and nitrile substituents at ambient temperature. In addition, the optimal conditions gave higher chemoselectivity for aldehydes in the presence of ketones.
- Kim, Joo Yeon,Shin, Won Kyu,Jaladi, Ashok Kumar,An, Duk Keun
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- Nickel(II)-dipyridylphosphine-catalyzed enantioselective hydrosilylation of ketones in air
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Out of thin air: Catalytic amounts of nickel(II) salt and non-racemic dipyridylphosphine ligand, as well as the stoichiometric hydride source PhSiH3, formed an effective catalyst system for the Ni II-catalyzed asymmetric hydrosilylat
- Wu, Fei-Fei,Zhou, Ji-Ning,Fang, Qiang,Hu, Yi-Hu,Li, Shijun,Zhang, Xi-Chang,Wu, Jing,Chan, Albert S. C.
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- Cyclopentadienyliron dicarbonyl dimer: A simple tool for the hydrosilylation of aldehydes and ketones under air
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The readily available iron complex [CpFe(CO)2]2 (1) exhibits good catalytic activity in the hydrosilylation of aldehydes and ketones in the presence of diethoxymethylsilane. The procedure described is air-tolerant and applicable to a wide range of substrates.
- Jung, Thais Cordeiro,Argouarch, Gilles,Van De Weghe, Pierre
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- Efficient Transfer Hydrogenation of Ketones Catalyzed by a Phosphine-Free Cobalt-NHC Complex
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A simple phosphine-free cobalt-NHC pincer complex has been synthesized and utilized for the transfer hydrogenation of ketones with 2-propanol as hydrogen donor. A broad range of ketones varying from aromatic, aliphatic and heterocyclic were effectively reduced to their corresponding alcohols in moderate to excellent yields with good tolerance of functional groups.
- Ibrahim, Jessica Juweriah,Reddy, C. Bal,Fang, Xiaolong,Yang, Yong
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- FUNGAL HYDROXYLATION OF ETHYL BENZENE AND DERIVATIVES
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The fungus Mortierella isabellina converts ethyl benzene and a number of para-substituted derivatives to the corresponding optically active 1-phenylethanols with enantiomeric excesses between 5 and 40percent.Hydrogen removal from the substrate preceeds product formation and is stereochemically independent of it.
- Holland, Herbert L.,Carter, Ian M.,Chenchaiah, P. Chinna,Khan, Shaheer H.,Munoz, Benito,et al.
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- Direct Asymmetric Hydrogenation and Dynamic Kinetic Resolution of Aryl Ketones Catalyzed by an Iridium-NHC Exhibiting High Enantio- and Diastereoselectivity
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A chiral iridium carbene-oxazoline catalyst is reported that is able to directly and efficiently hydrogenate a wide variety of ketones in excellent yields and good enantioselectivity (up to 93 % ee). Moreover, when using racemic α-substituted ketones, excellent diastereoselectivities were obtained (dr 99:1) by dynamic kinetic resolution of the in situ formed enolate. Overall, the herein described hydrogenation occurs under ambient conditions using low hydrogen pressures, providing a direct and atom efficient method towards chiral secondary alcohols.
- Ayya Swamy P, Chinna,Varenikov, Andrii,de Ruiter, Graham
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- Reduction of carbonyl compounds via hydrosilylation catalyzed by well-defined PNP-Mn(I) hydride complexes
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Reduction reactions of unsaturated compounds are fundamental transformations in synthetic chemistry. In this context, the reduction of polarized double bonds such as carbonyl or C=C motifs can be achieved by hydrogenation reactions. We describe here a highly chemoselective Mn(I)-based PNP pincer catalyst for the hydrosilylation of aldehydes and ketones employing polymethylhydrosiloxane (PMHS) as inexpensive hydrogen donor. Graphic abstract: [Figure not available: see fulltext.]
- Weber, Stefan,Iebed, Dina,Glatz, Mathias,Kirchner, Karl
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- TBAF-catalyzed hydrosilylation for the reduction of aromatic nitriles
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The selective catalytic hydrosilylation of functional groups is becoming an interesting tool for organic synthesis. In the present study, fluoride-catalyzed hydrosilylations of aromatic nitriles have been examined in detail. Using catalytic amounts of inexpensive tetra-n-butylammonium fluoride (TBAF) various aromatic nitriles are reduced in good yields under mild conditions.
- Bornschein, Christoph,Werkmeister, Svenja,Junge, Kathrin,Beller, Matthias
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- N-heterocyclic carbene complexes of nickel as efficient catalysts for hydrosilylation of carbonyl derivatives
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Well-defined nickel(II) complexes bearing bidentate tetramethylcyclopentadienyl-functionalised N-heterocyclic carbene ligands (Cp*- NHCMe)NiX (X=Cl, O-t-Bu) have been prepared and applied as efficient catalysts for the hydrosilylation of carbonyl groups. The nickel-alkoxide (Cp*- NHCMe)NiACHTUNGTRENUNG(O-t-Bu) complex displayed remarkable catalytic activity in the reduction of aldehydes, affording quantitative conversion to the corresponding alcohols in 5 min at 25 °C. Mechanistic studies, based on stoichiometric reactions, revealed that the transient nickel hydride (Cp*-NHCMe)NiH complex is the active species in the hydrosilylation of carbonyls.
- Postigo, Lorena,Royo, Beatriz
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- New efficient organocatalytic oxidation of benzylic compounds by molecular oxygen under mild conditions
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Efficient aerobic oxidation of benzylic compounds has been achieved under no irradiation using a new organocatalytic system in the presence of acridine yellow and N-hydroxyphthalimide with assistance of a catalytic amount of molecular bromine. Various substrates, especially alkylaromatics, were effectively oxygenated to the corresponding carbonyl compounds with molecular oxygen as oxidant under mild conditions. For instance, indan was oxidized with 92% conversion and 79% selectivity for 1-indanone under 0.3 MPa of O2 at 75°C.
- Tong, Xinli,Xu, Jie,Miao, Hong,Gao, Jin
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- Asymmetric ketone hydroboration catalyzed by alkali metal complexes derived from BINOL ligands
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The ability of alkali metal complexes featuring functionalized BINOL-derived ligands to catalyze ketone hydroboration reactions was explored. The reduced products were formed in excellent yields and with variable enantioselectivities dependent upon the nature of the ligand and the alkali metal cation.
- Carden, Jamie L.,Melen, Rebecca L.,Newman, Paul D.,Ruddy, Adam J.,Willcox, Darren
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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.
- Tadiello, Laura,Gandini, Tommaso,Stadler, Bernhard M.,Tin, Sergey,Jiao, Haijun,de Vries, Johannes G.,Pignataro, Luca,Gennari, Cesare
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p. 235 - 246
(2022/01/03)
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- Cobalt-catalyzed asymmetric hydrogenation of ketones: A remarkable additive effect on enantioselectivity
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A chiral cobalt pincer complex, when combined with an achiral electron-rich mono-phosphine ligand, catalyzes efficient asymmetric hydrogenation of a wide range of aryl ketones, affording chiral alcohols with high yields and moderate to excellent enantioselectivities (29 examples, up to 93% ee). Notably, the achiral mono-phosphine ligand shows a remarkable effect on the enantioselectivity of the reaction.
- Du, Tian,Wang, Biwen,Wang, Chao,Xiao, Jianliang,Tang, Weijun
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supporting information
p. 1241 - 1244
(2020/10/02)
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- Highly Active Cooperative Lewis Acid—Ammonium Salt Catalyst for the Enantioselective Hydroboration of Ketones
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Enantiopure secondary alcohols are fundamental high-value synthetic building blocks. One of the most attractive ways to get access to this compound class is the catalytic hydroboration. We describe a new concept for this reaction type that allowed for exceptional catalytic turnover numbers (up to 15 400), which were increased by around 1.5–3 orders of magnitude compared to the most active catalysts previously reported. In our concept an aprotic ammonium halide moiety cooperates with an oxophilic Lewis acid within the same catalyst molecule. Control experiments reveal that both catalytic centers are essential for the observed activity. Kinetic, spectroscopic and computational studies show that the hydride transfer is rate limiting and proceeds via a concerted mechanism, in which hydride at Boron is continuously displaced by iodide, reminiscent to an SN2 reaction. The catalyst, which is accessible in high yields in few steps, was found to be stable during catalysis, readily recyclable and could be reused 10 times still efficiently working.
- Titze, Marvin,Heitk?mper, Juliane,Junge, Thorsten,K?stner, Johannes,Peters, René
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supporting information
p. 5544 - 5553
(2021/02/05)
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- Photochemical C-H Activation Enables Nickel-Catalyzed Olefin Dicarbofunctionalization
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Alkenes, ethers, and alcohols account for a significant percentage of bulk reagents available to the chemistry community. The petrochemical, pharmaceutical, and agrochemical industries each consume gigagrams of these materials as fuels and solvents each year. However, the utilization of such materials as building blocks for the construction of complex small molecules is limited by the necessity of prefunctionalization to achieve chemoselective reactivity. Herein, we report the implementation of efficient, sustainable, diaryl ketone hydrogen-atom transfer (HAT) catalysis to activate native C-H bonds for multicomponent dicarbofunctionalization of alkenes. The ability to forge new carbon-carbon bonds between reagents typically viewed as commodity solvents provides a new, more atom-economic outlook for organic synthesis. Through detailed experimental and computational investigation, the critical effect of hydrogen bonding on the reactivity of this transformation was uncovered.
- Campbell, Mark W.,Yuan, Mingbin,Polites, Viktor C.,Gutierrez, Osvaldo,Molander, Gary A.
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supporting information
p. 3901 - 3910
(2021/04/06)
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- Ruthenium-p-cymene Complex Side-Wall Covalently Bonded to Carbon Nanotubes as Efficient Hybrid Transfer Hydrogenation Catalyst
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A half-sandwich ruthenium-p-cymene organometallic complex has been immobilized at Single Walled Carbon Nanotubes (SWNT) sidewalls through a stepwise covalent chemistry protocol. The introduction of amino groups by means of diazonium-chemistry protocols leads the grafting at the outer walls of the nanotubes. This hybrid material is active in the transfer hydrogenation of ketones to yield alcohols, using as hydrogen source 2-propanol. SWNT?NH2?Ru presents a broad scope, performing the reaction under aerobic conditions and can be recycled over 9 consecutive reaction runs without losing activity or leaching ruthenium out. Comparison of the activity with related homogeneous catalysts reveals an improved performance due to the covalent bond between the metal and the material, achieving turnover frequencies as high as 192774 h?1.
- Blanco, Matías,Cembellín, Sara,Agnoli, Stefano,Alemán, José
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p. 5156 - 5165
(2021/11/05)
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- Reaction of Diisobutylaluminum Borohydride, a Binary Hydride, with Selected Organic Compounds Containing Representative Functional Groups
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The binary hydride, diisobutylaluminum borohydride [(iBu)2AlBH4], synthesized from diisobutylaluminum hydride (DIBAL) and borane dimethyl sulfide (BMS) has shown great potential in reducing a variety of organic functional groups. This unique binary hydride, (iBu)2AlBH4, is readily synthesized, versatile, and simple to use. Aldehydes, ketones, esters, and epoxides are reduced very fast to the corresponding alcohols in essentially quantitative yields. This binary hydride can reduce tertiary amides rapidly to the corresponding amines at 25 °C in an efficient manner. Furthermore, nitriles are converted into the corresponding amines in essentially quantitative yields. These reactions occur under ambient conditions and are completed in an hour or less. The reduction products are isolated through a simple acid-base extraction and without the use of column chromatography. Further investigation showed that (iBu)2AlBH4 has the potential to be a selective hydride donor as shown through a series of competitive reactions. Similarities and differences between (iBu)2AlBH4, DIBAL, and BMS are discussed.
- Amberchan, Gabriella,Snelling, Rachel A.,Moya, Enrique,Landi, Madison,Lutz, Kyle,Gatihi, Roxanne,Singaram, Bakthan
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supporting information
p. 6207 - 6227
(2021/05/06)
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- Ambient-pressure highly active hydrogenation of ketones and aldehydes catalyzed by a metal-ligand bifunctional iridium catalyst under base-free conditions in water
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A green, efficient, and high active catalytic system for the hydrogenation of ketones and aldehydes to produce corresponding alcohols under atmospheric-pressure H2 gas and ambient temperature conditions was developed by a water-soluble metal–ligand bifunctional catalyst [Cp*Ir(2,2′-bpyO)(OH)][Na] in water without addition of a base. The catalyst exhibited high activity for the hydrogenation of ketones and aldehydes. Furthermore, it was worth noting that many readily reducible or labile functional groups in the same molecule, such as cyan, nitro, and ester groups, remained unchanged. Interestingly, the unsaturated aldehydes can be also selectively hydrogenated to give corresponding unsaturated alcohols with remaining C=C bond in good yields. In addition, this reaction could be extended to gram levels and has a large potential of wide application in future industrial.
- Wang, Rongzhou,Yue, Yuancheng,Qi, Jipeng,Liu, Shiyuan,Song, Ao,Zhuo, Shuping,Xing, Ling-Bao
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- Method for synthesizing secondary alcohol in water phase
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The invention discloses a method for synthesizing secondary alcohol in a water phase. The method comprises the following steps: taking ketone as a raw material, selecting water as a solvent, and carrying out catalytic hydrogenation reaction on the ketone in the presence of a water-soluble catalyst to obtain the secondary alcohol, wherein the catalyst is a metal iridium complex [Cp * Ir (2, 2'-bpyO)(OH)][Na]. Water is used as the solvent, so that the use of an organic solvent is avoided, and the method is more environment-friendly; the reaction is carried out at relatively low temperature and normal pressure, and the reaction conditions are mild; alkali is not needed in the reaction, so that generation of byproducts is avoided; and the conversion rate of the raw materials is high, and the yield of the obtained product is high. The method not only has academic research value, but also has a certain industrialization prospect.
- -
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Paragraph 0035-0036
(2021/07/14)
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- Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
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We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
- Topf, Christoph,Vielhaber, Thomas
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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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- Structure-Activity Relationship Studies Reveal New Astemizole Analogues Active against Plasmodium falciparum in Vitro
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In the context of drug repositioning and expanding the existing structure-activity relationship around astemizole (AST), a new series of analogues were designed, synthesized, and evaluated for their antiplasmodium activity. Among 46 analogues tested, compounds 21, 30, and 33 displayed high activities against asexual blood stage parasites (PfNF54 IC50 = 0.025-0.043 μM), whereas amide compound 46 additionally showed activity against late-stage gametocytes (stage IV/V; PfLG IC50 = 0.6 ± 0.1 μM) and 860-fold higher selectivity over hERG (46, SI = 43) compared to AST. Several analogues displaying high solubility (Sol > 100 μM) and low cytoxicity in the Chinese hamster ovary (SI > 148) cell line have also been identified.
- Birkholtz, Lyn-Marie,Chibale, Kelly,Coertzen, Dina,Ferger, Richard,Kumar, Malkeet,Mambwe, Dickson,Njoroge, Mathew,Reader, Janette,Taylor, Dale,Van Der Watt, Mari?tte
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supporting information
p. 1333 - 1341
(2021/08/24)
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- Deep eutectic solvents as H2-sources for Ru(II)-catalyzed transfer hydrogenation of carbonyl compounds under mild conditions
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The employment of easily affordable ruthenium(II)-complexes as pre-catalysts in the transfer hydrogenation of carbonyl compounds in deep eutectic media is described for the first time. The eutectic mixture tetrabutylammonium bromide/formic acid = 1/1 (TBABr/HCOOH = 1/1) acts both as reaction medium and hydrogen source. The addition of a base is required for the process to occur. An extensive optimization of the reaction conditions has been carried out, in terms of catalyst loading, type of complexes, H2-donors, reaction temperature and time. The combination of the dimeric complex [RuCl(p-cymene)-μ-Cl]2 (0.01–0.05 eq.) and the ligand dppf (1,1′-ferrocenediyl-bis(diphenylphosphine)ferrocene) in 1/1 molar ratio has proven to be a suitable catalytic system for the reduction of several and diverse aldehydes and ketones to their corresponding alcohols under mild conditions (40–60 °C) in air, showing from moderate to excellent tolerability towards different functional groups (halogen, cyano, nitro, phenol). The reduction of imine compounds to their corresponding amine derivatives was also studied. In addition, the comparison between the results obtained in TBABr/HCOOH and in organic solvents suggests a non-innocent effect of the DES medium during the process.
- Cavallo, Marzia,Arnodo, Davide,Mannu, Alberto,Blangetti, Marco,Prandi, Cristina,Baratta, Walter,Baldino, Salvatore
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supporting information
(2021/02/22)
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- Synthesis and catalytic activity of N-heterocyclic silylene (NHSi) iron (II) hydride for hydrosilylation of aldehydes and ketones
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A novel silylene supported iron hydride [Si, C]FeH (PMe3)3 (1) was synthesized by C (sp3)-H bond activation with zero-valent iron complex Fe (PMe3)4. Complex 1 was fully characterized by spectroscopic methods and single crystal X-ray diffraction analysis. To the best of our knowledge, 1 is the first example of silylene-based hydrido chelate iron complex produced through activation of the C (sp3)?H bond. It was found that complex 1 exhibited excellent catalytic activity for hydrosilylation of aldehydes and ketones. The catalytic system showed good tolerance and catalytic activity for the substrates with different functional groups on the benzene ring. It is worth mentioning that, the experimental results showed that both ketones and aldehydes could be reduced in good to excellent yields under the same catalytic conditions. Based on the experiments and literature reports, a possible catalytic mechanism was proposed.
- Du, Xinyu,Qi, Xinghao,Li, Kai,Li, Xiaoyan,Sun, Hongjian,Fuhr, Olaf,Fenske, Dieter
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- Hydrosilylation of Carbonyl Compounds Catalyzed by a Nickel Complex Bearing a PBP Ligand
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The efficient catalytic hydrosilylation of ketones and aldehydes has been investigated using a nickel pincer hydride complex supported by a diphosphino-boryl ligand (PBP). It was found that the presence of the boryl group within the skeleton of the ligand has a beneficial effect on the catalytic activities observed for ketones compared to related pincer systems. The analysis of the reaction mechanism allows for the synthesis and characterization of a nickel alkoxide derivative by insertion of the carbonyl moiety into the Ni?H bond. Combined experimental and theoretical analysis (DFT) support a reaction mechanism that involves the initial formation of an alkoxide complex followed by reaction with the silane to release the corresponding silyl ether and regenerate the catalyst.
- Antonio Fernández, José,Manuel García, Juan,Ríos, Pablo,Rodríguez, Amor
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supporting information
p. 2993 - 2998
(2021/07/10)
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- Pincerlike molybdenum complex and preparation method thereof, catalytic composition and application thereof, and alcohol preparation method
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The invention discloses a clamp-type molybdenum complex, a preparation method, a corresponding catalyst composition and application. The method comprises the steps: obtaining 9 molybdenum complexes with different structures through coordination reaction of 2-(substituent ethyl)-(5, 6, 7, 8-tetrahydroquinolyl) amine and a corresponding carbonyl molybdenum metal precursor; and catalyzing a ketone compound transfer hydrogenation reaction through a molybdenum complex to generate 40 alcohol compounds. The preparation method of the molybdenum complex is simple, high in yield and good in stability. For a transfer hydrogenation reaction of ketone, the molybdenum-based catalytic system has high catalytic activity and small molybdenum loading capacity, is used for production of aromatic and aliphatic alcohols, and has the advantages of simple method, small environmental pollution and high yield.
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Paragraph 0125-0130
(2021/08/11)
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- Benzimidazole fragment containing Mn-complex catalyzed hydrosilylation of ketones and nitriles
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The synthesis of a new bidentate (NN)–Mn(I) complex is reported and its catalytic activity towards the reduction of ketones and nitriles is studied. On comparing the reactivity of various other Mn(I) complexes supported by benzimidazole ligand, it was observed that the Mn(I) complexes bearing 6-methylpyridine and benzimidazole fragments exhibited the highest catalytic activity towards monohydrosilylation of ketones and dihydrosilylation of nitriles. Using this protocol, a wide range of ketones were selectively reduced to the corresponding silyl ethers. In case of unsaturated ketones, the chemoselective reduction of carbonyl group over olefinic bonds was observed. Additionally, selective dihydrosilylation of several nitriles were also achieved using this complex. Mechanistic investigations with radical scavengers suggested the involvement of radical species during the catalytic reaction. Stoichiometric reaction of the Mn(I) complex with phenylsilane revealed the formation of a new Mn(I) complex.
- Ganguli, Kasturi,Mandal, Adarsha,Sarkar, Bidisha,Kundu, Sabuj
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supporting information
(2020/08/13)
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- Transfer Hydrogenation of Ketones and Imines with Methanol under Base-Free Conditions Catalyzed by an Anionic Metal-Ligand Bifunctional Iridium Catalyst
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An anionic iridium complex [Cp*Ir(2,2′-bpyO)(OH)][Na] was found to be a general and highly efficient catalyst for transfer hydrogenation of ketones and imines with methanol under base-free conditions. Readily reducible or labile substituents, such as nitro, cyano, and ester groups, were tolerated under present reaction conditions. Notably, this study exhibits the unique potential of anionic metal-ligand bifunctional iridium catalysts for transfer hydrogenation with methanol as a hydrogen source.
- Han, Xingyou,Li, Feng,Liu, Peng,Wang, Rongzhou,Xu, Jing
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p. 2242 - 2249
(2020/03/13)
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- Hydrogenation reaction method
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The invention relates to a hydrogenation reaction method, and belongs to the technical field of organic synthesis. The hydrogenation reaction method provided by the invention comprises the following steps: carrying out a hydrogen transfer reaction on a hydrogen acceptor compound, pinacol borane and a catalyst in a solvent in the presence of proton hydrogen, so that the hydrogen acceptor compound is subjected to a hydrogenation reaction; the catalyst is one or more than two of a palladium catalyst, an iridium catalyst and a rhodium catalyst; the hydrogen acceptor compound comprises one or morethan two functional groups of carbon-carbon double bonds, carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogentriple bonds and epoxy. The method is mild in reaction condition, easy to operate, high in yield, short in reaction time, wide in substrate application range, suitable for carbon-carbon double bonds,carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogen triple bonds and epoxy functional groups, good in selectivity and high in reaction specificity.
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Paragraph 0034; 0317-0320
(2020/05/14)
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- Efficient Transfer Hydrogenation of Ketones using Methanol as Liquid Organic Hydrogen Carrier
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Herein, we demonstrate an efficient protocol for transfer hydrogenation of ketones using methanol as practical and useful liquid organic hydrogen carrier (LOHC) under Ir(III) catalysis. Various ketones, including electron-rich/electron-poor aromatic ketones, heteroaromatic and aliphatic ketones, have been efficiently reduced into their corresponding alcohols. Chemoselective reduction of ketones was established in the presence of various other reducible functional groups under mild conditions.
- Garg, Nidhi,Paira, Soumen,Sundararaju, Basker
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p. 3472 - 3476
(2020/05/29)
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- Potassium Fluoride-Catalyzed Hydroboration of Aldehydes and Ketones: Facile Reduction to Primary and Secondary Alcohols
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A catalytic hydroboration of various ketones and aldehydes can be achieved in the presence of inexpensive and commercially available inorganic salts containing fluoride anion. As a result, the reduction of carbonyl moieties to the corresponding primary and secondary alcohols can be achieved at room temperature under mild conditions.
- Kuciński, Krzysztof,Hreczycho, Grzegorz
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p. 552 - 555
(2020/02/04)
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- Palladium-Catalyzed Selective Reduction of Carbonyl Compounds
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Two new examples of structurally characterized β-diketiminate analogues i.e., conjugated bis-guanidinate (CBG) supported palladium(II) complexes, [LPdX]2; [L= {(ArHN)(ArN)–C=N–C=(NAr)(NHAr)}; Ar = 2,6-Et2-C6H3], X = Cl (1), Br (2) have been reported. The synthesis of complexes 1–2 was achieved by two methods. Method A involves deprotonation of LH by nBuLi followed by the treatment of LLi (insitu formed) with PdCl2 in THF, which afforded compound 1 in good yield (75 %). In Method B, the reaction between free LH and PdX2 (X = Cl or Br) in THF allowed the formation of complexes 1 (Yield 73 %) and 2 (Yield 52 %), respectively. Moreover, these complexes were characterized thoroughly by several spectroscopic techniques (1H, 13C NMR, UV/Vis, FT-IR, and HRMS), including single-crystal X-ray structural and elemental analyses. In addition, we tested the catalytic activity of these complexes 1–2 for the hydroboration of carbonyl compounds with pinacolborane (HBpin). We observed that compound 1 exhibits superior catalytic activity when compared to 2. Compound 1 efficiently catalyzes various aldehydes and ketones under solvent-free conditions. Furthermore, both inter- and intramolecular chemoselectivity hydroboration of aldehydes over other functionalities have been established.
- Sarkar, Nabin,Mahato, Mamata,Nembenna, Sharanappa
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p. 2295 - 2301
(2020/05/18)
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- A State-of-the-Art Heterogeneous Catalyst for Efficient and General Nitrile Hydrogenation
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Cobalt-doped hybrid materials consisting of metal oxides and carbon derived from chitin were prepared, characterized and tested for industrially relevant nitrile hydrogenations. The optimal catalyst supported onto MgO showed, after pyrolysis at 700 °C, magnesium oxide nanocubes decorated with carbon-enveloped Co nanoparticles. This special structure allows for the selective hydrogenation of diverse and demanding nitriles to the corresponding primary amines under mild conditions (e.g. 70 °C, 20 bar H2). The advantage of this novel catalytic material is showcased for industrially important substrates, including adipodinitrile, picolinonitrile, and fatty acid nitriles. Notably, the developed system outperformed all other tested commercial catalysts, for example, Raney Nickel and even noble-metal-based systems in these transformations.
- Formenti, Dario,Mocci, Rita,Atia, Hanan,Dastgir, Sarim,Anwar, Muhammad,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
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supporting information
p. 15589 - 15595
(2020/10/02)
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- Zinc Hydride-Catalyzed Hydrofuntionalization of Ketones
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Three new dimeric bis-guanidinate zinc(II) alkyl, halide, and hydride complexes [LZnEt]2 (1), [LZnI]2 (2) and [LZnH]2 (3) were prepared. Compound 3 was successfully employed for the hydrosilylation and hydroboration of a vast number of ketones. The catalytic performance of 3 in the hydroboration of acetophenone exhibits a turnover frequency, reaching up to 5800 h-1, outperforming that of reported zinc hydride catalysts. Notably, both intra- and intermolecular chemoselective hydrosilylation and hydroboration reactions have been investigated.
- Sahoo, Rajata Kumar,Mahato, Mamata,Jana, Achintya,Nembenna, Sharanappa
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p. 11200 - 11210
(2020/10/12)
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- An Enantioconvergent Benzylic Hydroxylation Using a Chiral Aryl Iodide in a Dual Activation Mode
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The application of a triazole-substituted chiral iodoarene in a direct enantioselective hydroxylation of alkyl arenes is reported. This method allows the rapid synthesis of chiral benzyl alcohols in high yields and stereocontrol, despite its nontemplated nature. In a cascade activation consisting of an initial irradiation-induced radical C-H-bromination and a consecutive enantioconvergent hydroxylation, the iodoarene catalyst has a dual role. It initiates the radical bromination in its oxidized state through an in-situ-formed bromoiodane and in the second, Cu-catalyzed step, it acts as a chiral ligand. This work demonstrates the ability of a chiral aryl iodide catalyst acting both as an oxidant and as a chiral ligand in a highly enantioselective C-H-activating transformation. Furthermore, this concept presents an enantioconvergent hydroxylation with high selectivity using a synthetic catalyst.
- Abazid, Ayham H.,Clamor, Nils,Nachtsheim, Boris J.
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p. 8042 - 8048
(2020/09/21)
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- SECONDARY ARYL ALCOHOL AND METHOD OF SYNTHESIZING THEREOF
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The present invention relates to secondary aryl alcohol and a method for synthesizing the same and, specifically, to synthesizing secondary aryl alcohol having high optical selectivity through a hydrosilylation reaction using ketone containing an aryl group. In the method for synthesizing secondary aryl alcohol according to an embodiment of the present invention, secondary aryl alcohol is synthesized by making ketone react with hydrosilane under a chiral boron Lewis acid catalyst.COPYRIGHT KIPO 2020
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Paragraph 0032; 0062-0069
(2020/05/13)
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- Observation of hyperpositive non-linear effect in catalytic asymmetric organozinc additions to aldehydes
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Asymmetric amplification is a phenomenon that is believed to play a key role in the emergence of homochirality in life. In asymmetric catalysis, theoretical and experimental models have been investigated to provide an understanding of how chiral amplification is possible, in particular based on non-linear effects. Interestingly, it has been proposed a quarter century ago that chiral catalysts, when not enantiopure might even be more enantioselective than their enantiopure counterparts. We show here that such hyperpositive non-linear effect in asymmetric catalysis is indeed possible. An in-depth study into the underlying mechanism was carried out, and the scheme we derive differs from the previous proposed models.
- Geiger, Yannick,Achard, Thierry,Maisse-Fran?ois, Aline,Bellemin-Laponnaz, Stéphane
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supporting information
p. 1250 - 1256
(2020/07/25)
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- Investigation into an Unexpected Impurity: A Practical Approach to Process Development for the Addition of Grignard Reagents to Aldehydes Using Continuous Flow Synthesis
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This work presents a case study of process development using continuous flow synthesis. In developing a process for manufacturing drug substances in batch reactors, we unexpectedly obtained a significant amount of a trimerized byproduct on addition of MeMgBr to an aldehyde. Consideration of a plausible generation mechanism for the byproduct indicated that it arose from a reaction between the starting material and the Mg salt of the target product. This led us to try applying continuous flow synthesis to the process to shorten the time during which the starting material coexists with the Mg salt of the target product. This led to drastic suppression of the byproduct under very mild conditions and the establishment of a more robust process than that for batch reactors.
- Hosoya, Masahiro,Kurose, Noriyuki,Nishijima, Shogo
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supporting information
(2020/03/13)
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- Asymmetric Magnesium-Catalyzed Hydroboration by Metal-Ligand Cooperative Catalysis
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Asymmetric catalysis with readily available, cheap, and non-toxic alkaline earth metal catalysts represents a sustainable alternative to conventional synthesis methodologies. In this context, we describe the development of a first MgII-catalyzed enantioselective hydroboration providing the products with excellent yields and enantioselectivities. NMR spectroscopy studies and DFT calculations provide insights into the reaction mechanism and the origin of the enantioselectivity which can be explained by a metal-ligand cooperative catalysis pathway involving a non-innocent ligand.
- Falconnet, Alban,Magre, Marc,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 17567 - 17571
(2019/11/13)
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- Towards practical earth abundant reduction catalysis: Design of improved catalysts for manganese catalysed hydrogenation
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Manganese catalysts derived from tridentate P,N,N ligands can be activated easily using weak bases for both ketone and ester hydrogenations. Kinetic studies indicate the ketone hydrogenations are 0th order in acetophenone, positive order in hydrogen and 1st order in the catalyst. This implies that the rate determining step of the reaction was the activation of hydrogen. New ligand systems with varying donor strength were studied and it was possible to make the hydrogen activation significantly more efficient; a catalyst displaying around a 3-fold increase in initial turn-over frequencies for the hydrogenation of acetophenone relative to the parent system was discovered as a result of these kinetic investigations. Ester hydrogenations and ketone transfer hydrogenation (isopropanol as reductant) are first order for both the substrate and catalysts. Kinetic studies also gained insight into catalyst stability and identified a working range in which the catalyst is stable throughout the catalytic reaction (and a larger working range where high yields can still be achieved). The new more active catalyst, combining an electron-rich phosphine with an electron-rich pyridine is capable of hydrogenating acetophenone using as little as 0.01 mol% catalyst at 65 °C. In all, protocols for reduction of 21 ketones and 15 esters are described.
- Widegren, Magnus B.,Clarke, Matthew L.
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p. 6047 - 6058
(2019/11/14)
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- Ni-Catalyzed Reductive Cyanation of Aryl Halides and Phenol Derivatives via Transnitrilation
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Herein, we report a Ni-catalyzed reductive coupling for the synthesis of benzonitriles from aryl (pseudo)halides and an electrophilic cyanating reagent, 2-methyl-2-phenyl malononitrile (MPMN). MPMN is a bench-stable, carbon-bound electrophilic CN reagent that does not release cyanide under the reaction conditions. A variety of medicinally relevant benzonitriles can be made in good yields. Addition of NaBr to the reaction mixture allows for the use of more challenging aryl electrophiles such as aryl chlorides, tosylates, and triflates. Mechanistic investigations suggest that NaBr plays a role in facilitating oxidative addition with these substrates.
- Mills, L. Reginald,Graham, Joshua M.,Patel, Purvish,Rousseaux, Sophie A. L.
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p. 19257 - 19262
(2019/12/02)
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- Method for synthesizing secondary alcohol
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The invention discloses a method for synthesizing secondary alcohol, which utilizes transition metal catalysis and uses isopropanol as a hydrogen source to synthesize the secondary alcohol. The reaction not only uses inexpensive and environmentally friendly isopropanol as the hydrogen source and a solvent, but also has the advantages of high yield, environmental protection, and the like, and therefore the reaction has broad development prospects.
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Paragraph 0080; 0081; 0082; 0083
(2019/03/15)
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- Silver-Catalyzed Hydrogenation of Ketones under Mild Conditions
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The silver-catalyzed hydrogenation of ketones using H2 as hydrogen source is reported. Silver nanoparticles are generated from simple silver (I) salts and operate at 25 °C under 20 bar of hydrogen pressure. Various aliphatic and aromatic ketones, including natural products were reduced into the corresponding alcohols in high yields. This silver catalyst allows for the selective hydrogenation of ketones in the presence of other functional groups. (Figure presented.).
- Wang, Shengdong,Huang, Haiyun,Tsareva, Svetlana,Bruneau, Christian,Fischmeister, Cédric
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supporting information
p. 786 - 790
(2019/01/04)
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- Borinic Acid Mediated Hydrosilylations: Reductions of Carbonyl Derivatives
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4-Fluoro-2-chlorophenylborinic acid acts as a precatalyst in the presence of phenylsilane for the facile reduction of ketones, aldehydes and imines. Notably, synergistic mediation of a tertiary amine was found essential to trigger silicon to boron hydride transfer to generate a key amine–diarylhydroborane Lewis complex.
- Chardon, Aurélien,Rouden, Jacques,Blanchet, Jér?me
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supporting information
p. 995 - 998
(2018/12/13)
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- Ligand Effect in Alkali-Metal-Catalyzed Transfer Hydrogenation of Ketones
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This work unveils the reactivity patterns, as well as ligand and additive effect on alkali-metal-base-catalyzed transfer hydrogenation of ketones. Crucially to this reactivity is the presence of a Lewis acid (alkali cation), as opposed to a simple base effect. With aryl ketones, the observed reactivity order is Na+>Li+>K+, whereas for aliphatic substrates it follows the expected Lewis acidity, Li+>Na+>K+. Importantly, the reactivity pattern can be drastically changed by adding ligands and additives. Kinetic, labelling, and competition experiments as well as DFT calculations suggested that the reaction proceeds through a concerted direct hydride-transfer mechanism, originally suggested by Woodward. The lithium cation was found to be intrinsically more active than heavier congeners, but in the case of aryl ketones a decrease in reaction rate was observed at ≈40 percent conversion with lithium cations. Noncovalent-interaction analysis revealed that this deceleration effect originated from specific noncovalent interactions between the aryl moiety of 1-phenylethanol and the carbonyl group of acetophenone, which stabilize the product in the coordination sphere of lithium and thus poison the catalyst. The ligand/additive effect is a complicated phenomenon that includes a combination of several factors, such as the decrease of activation energy by ligation (confirmed by distortion/interaction calculations of N,N,N’,N’-tetramethylethylenediamine, TMEDA) and the change in relative stabilization of reagents and substrates in the solution and the coordination sphere of the metal. Finally, we observed that lithium-base-catalyzed transfer hydrogenation can be further facilitated by the addition of an inexpensive and benign reagent, LiCl, which likely operates by re-initiating the reaction on a new lithium center.
- Alshakova, Iryna D.,Dudding, Travis,Foy, Hayden C.,Nikonov, Georgii I.
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supporting information
(2019/08/21)
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- Cooperative Mn(i)-complex catalyzed transfer hydrogenation of ketones and imines
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The synthesis and reactivity of Mn(i) complexes bearing bifunctional ligands comprising both the amine N-H and benzimidazole fragments are reported. Among the various ligands, the N-((1H-benzimidazol-2-yl)methyl)aniline ligand containing Mn(i) complex presented higher reactivity in the transfer hydrogenation (TH) of ketones in 2-propanol. Experimentally, it was established that both the benzimidazole and amine N-H proton played a vital role in the enhancement of the catalytic activity. Utilizing this system a wide range of aldehydes and ketones were reduced efficiently. Notably, the TH of several imines, as well as chemoselective reduction of unsaturated ketones, was achieved in the presence of this catalyst. DFT calculations were carried out to understand the plausible reaction mechanism which disclosed that the transfer hydrogenation reaction followed a concerted outer-sphere mechanism.
- Ganguli, Kasturi,Shee, Sujan,Panja, Dibyajyoti,Kundu, Sabuj
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p. 7358 - 7366
(2019/06/06)
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- Transfer Hydrogenation of Carbonyl Groups, Imines and N-Heterocycles Catalyzed by Simple, Bipyridine-Based MnI Complexes
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Utilization of hydroxy-substituted bipyridine ligands in transition metal catalysis mimicking [Fe]-hydrogenase has been shown to be a promising approach in developing new catalysts for hydrogenation. For example, MnI complexes with 6,6′-dihydroxy-2,2′-bipyridine ligand have been previously shown to be active catalysts for CO2 hydrogenation. In this work, simple bipyridine-based Mn catalysts were developed that act as active catalysts for transfer hydrogenation of ketones, aldehydes and imines. For the first time, Mn-catalyzed transfer hydrogenation of N-heterocycles was reported. The highest catalytic activity among complexes with variously substituted ligands was observed for the complex bearing two OH groups in bipyridine. Deuterium labeling experiments suggest a monohydride pathway.
- Dubey, Abhishek,Rahaman, S. M. Wahidur,Fayzullin, Robert R.,Khusnutdinova, Julia R.
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p. 3844 - 3852
(2019/04/08)
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- Synthesis and Catalytic Activity of Iron Hydride Ligated with Bidentate N-Heterocyclic Silylenes for Hydroboration of Carbonyl Compounds
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We report the synthesis of a novel bidentate N-heterocyclic silylene (NHSi) ligand, N-(LSi:)-N-methyl-2-pyridinamine (1) (L = PhC(NtBu)2), and the first bischelate disilylene iron hydride, [(Si,N)(Si,C)Fe(H)(PMe3)] (2), and monosilylene iron hydride, [(Si,C)Fe(H)(PMe3)3] (2′), through Csp2-H activation of the NHSi ligand. Compounds 1 and 2 were fully characterized by spectroscopic methods and single-crystal X-ray diffraction analysis. Density functional theory calculations indicated the multiple-bond character of the Fe-Si bonds and the π back-donation from Fe(II) to the Si(II) center. Moreover, the strong donor character of ligand 1 enables 2 to act as an efficient catalyst for the hydroboration reaction of carbonyl compounds at room temperature. Chemoselective hydroboration is attained under these conditions. This might be the first example of hydroboration of ketones and aldehydes catalyzed by a silylene hydrido iron complex. A catalytic mechanism was suggested and partially experimentally verified.
- Qi, Xinghao,Zheng, Tingting,Zhou, Junhao,Dong, Yanhong,Zuo, Xia,Li, Xiaoyan,Sun, Hongjian,Fuhr, Olaf,Fenske, Dieter
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p. 268 - 277
(2019/01/21)
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- Transfer hydrogenation of ketones catalyzed by nickel complexes bearing an NHC [CNN] pincer ligand
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Four NHC [CNN] pincer nickel (II) complexes, [iPrCNN (CH2)4-Ni-Br] (5a), [nBuCNN (CH2)4-Ni-Br] (5b), [iPrCNN (Me)2-Ni-Br] (6a) and [nBuCNN (Me)2-Ni-Br] (6b), bearing unsymmetrical [C (carbene)N (amino)N (amine)] ligands were synthesized by the reactions of [CNN] pincer ligand precursors 4 with Ni (DME)Cl2 in the presence of Et3N. Complexes 5a and 5b are new and were completely characterized. The transfer hydrogenation of ketones catalyzed by the four pincer nickel complexes were explored. Complexes 5a and 6a have better catalytic activity than 5b and 6b. With a combination of NaOtBu/iPrOH/80?°C and 2% catalyst loading of 5a, 77–98% yields of aromatic alcohols could be obtained.
- Wang, Zijing,Li, Xiaoyan,Xie, Shangqing,Zheng, Tingting,Sun, Hongjian
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- Substitution of Secondary Benzylic Phosphates with Diarylmethyl Anions
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Substitution of diethyl and diphenyl benzylic phosphates, Alk-CH(Ar1)OP(O)(OR)2 (R = Et, Ph; Alk = Me, Et, i-Pr; Ar1 = aryl), with the anions derived from Ar2CH2 (Ph2CH2,9H-xanthene and fluorene) and n-BuLi at –15 °C was studied. For phosphates with Me as an Alk, diethyl phosphates produced Me-CH(Ar1)CH(Ar2)2 (Ar1 = 4-halo-, 4-CN, 4-Me-, 2-Me, 2-Br-, 3-MeO-phenyl and 2-naphthyl). However, an unwanted substitution at the Et group competed with phosphates of Alk = Et- and i-Pr. Fortunately, the corresponding diphenyl phosphates cleanly underwent the desired substitution. Two enantioenriched phosphates, MeCH(Ph)OP(O)(OEt)2 and EtCH(Ph)OP(O)(OPh)2, proceeded with complete inversion of the stereochemistry.
- Shinohara, Riku,Kawashima, Hidehisa,Ogawa, Narihito,Kobayashi, Yuichi
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p. 2717 - 2725
(2019/04/04)
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