- Nickel Nanoparticles Supported on CMK-3 with Enhanced Catalytic Performance for Hydrogenation of Carbonyl Compounds
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Ordered mesoporous carbon materials are becoming increasingly important in catalysis applications due to their advantageous stability and surface properties. In this paper, we report a replication of the synthesis of mesoporous carbon CMK-3 using SBA-15 as a silica template. Ni/CMK-3 was prepared by incorporating Ni particles formed inside the pores of CMK-3 by impregnation of nickel nitrate and subsequent hydrogen reduction. The prepared Ni/CMK-3 has a large surface area and a very small nickel nanoparticle size (1 nm) with the aim of achieving high performance in catalytic hydrogenation reactions. Moreover, we demonstrate that CMK-3 has a higher stability than that of SBA-15 during the hydrogenation reactions of acetophenone derivatives.
- Kim, Daeho,Kang, Hyuntae,Park, Hyesu,Park, Sungkyun,Park, Ji Chan,Park, Kang Hyun
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- Optical resolution of 1-arylethanols with a condensed aromatic ring by lipase from Pseudomonas aeruginosa.
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Enantioselective syntheses of both enantiomers of 1-arylethanols with a condensed aromatic ring have been done through acetylation of the racemic alcohols with vinyl acetate in the presence of a lipase from Pseudomonas aeruginosa (Toyobo, LIP). The lipase LIP showed high enantioselectivity and reactivity for the title compounds, reacted acetates, and remaining alcohols were obtained with high optical purity.
- Kato,Katayama,Fujii,Kimoto
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- Dendronized poly(Ru-BINAP) complexes: Highly effective and easily recyclable catalysts for asymmetric hydrogenation
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A new kind of dendronized polymeric chiral BINAP ligands has been synthesized and applied to the Ru-catalyzed asymmetric hydrogenation of simple aryl ketones and 2-arylacrylic acids. These dendronized poly(Ru-BINAP) catalysts exhibited high catalytic activity and enantioselectivity, very similar to those obtained with the corresponding parent Ru(BINAP) and the Ru(BINAP)-cored dendrimers. It was found that the pendant dendrons had a major impact on the solubility and the catalytic properties of the polymeric ligands. These polymeric catalysts could be easily recovered from the reaction solution by using solvent precipitation, and the reused catalyst showed no loss of activity or enantioselectivity.
- Deng, Guo-Jun,Yi, Bing,Huang, Yi-Yong,Tang, Wei-Jun,He, Yan-Mei,Fan, Qing-Hua
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- Ferrocene-based aminophosphine ligands in the Ru(II)-catalysed asymmetric hydrogenation of ketones: assessment of the relative importance of planar versus carbon-centred chirality
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Several ferrocene-based aminophosphine ligands have been prepared and shown to be effective in the Ru(II)-catalysed asymmetric hydrogenation of ketones. The enantioselectivity is mainly determined by the carbon-centred chirality of the ligands but the planar chirality is also important such that (RC,SFc)- or (SC,RFc)- are the matched chiralities.
- Chen, Weiping,Mbafor, William,Roberts, Stanley M.,Whittall, John
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- Lipase-catalysed Enantioselective Synthesis of Naphthyl Trifluoromethyl Carbinols and Their Corresponding Non-Fluorinated Counterparts
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Enantioselective synthesis of both enantiomers of β- and α-naphthyl trifluoromethyl carbinols (R)-1a, (S)-1a, (R)-2a, (S)-2a has been achieved through acylation of the corresponding racemic alcohols (RS)-1a and (RS)-2a with vinyl acetate in the presence of lipase PS.The effect of fluorine atoms on the extent and enantioselectivity of the process has been tested by carrying out the same biocatalytic transformation on their non-fluorinated counterparts (RS)-1b and (RS)-2b.The order of reactivity follows the trend (RS)-1b > (RS)-2b ca. (RS)-1a > (RS)-2a.Effect of thehydrophobicity of the solvent in the resolution of (RS)-1a is also presented.
- Gaspar, Jordi,Guerrero, Angel
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- Synthesis and enantiomeric resolution of medetomidine
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Medetomidine {4-[l-(2,3-dimethylphenyl)ethyl]-3H-imidazole], 5} is a selective α2-adrenoceptor agonist used in veterinary medicine for its analgesic and sedative properties. It is also an alternative and environmentally acceptable anti-fouling biocide which impedes the settlement of barnacles at nanomolar concentrations and replaces toxic antifouling coatings based on heavy metals. Several syntheses of medetomidine have been reported. The first method for the preparation of 5 and of other related 4-benzylimidazoles was described in a patent starting from 2,3-dimethylbromobenzene as shown in Scheme 1; unfortunately the yields were not reported.
- Fakhraian,Toulabi,Choobdari,Peyrovi,Ghanbary, H. Hadj
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- Atropisomeric α-methyl substituted analogues of 4-(dimethylamino)pyridine: Synthesis and evaluation as acyl transfer catalysts
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The regioselectivity of α-metalation-methylation of N-BF3 adducts of 4-(dimethylamino)pyridines as a function of β-substitution is examined in attempts to prepare configurationally stable atropisomeric derivatives (I and II) having an α-methyl substituent and a β-biaryl stereogenic axis. The activity of some of these derivatives as catalysts for acyl transfer is examined and the kinetic resolution of 1-(1-naphthyl)ethanol catalysed by α-methyl chiral DMAP (-)-24 is reported. A rationale for the reduced stereoselectivity of this catalyst relative to its non-α-substituted analogue (-)-1 is also proposed.
- Spivey,Maddaford,Leese,Redgrave
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- Design of boron bis-oxazolinate (B-BOXate) complexes: A new class of stable organometallic catalysts
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A new class of remarkably stable B-BOXate complexes has been synthesised, isolated and employed as chiral catalysts for asymmetric reduction of variously substituted prochiral ketones.
- Bandini,Cozzi,Monari,Perciaccante,Selva,Umani-Ronchi
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- Design of novel polymer-supported chiral catalyst for asymmetric transfer hydrogenation in water
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New polymer-supported chiral sulfonamides containing sulfonated pendant group have been synthesized. Chiral catalyst prepared from the new polymer-support is more effective for asymmetric transfer hydrogenation of aromatic ketones in water compared to tha
- Arakawa, Yukihiro,Haraguchi, Naoki,Itsuno, Shinichi
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- Synthesis of Ru-coordinating helical polymer and its utilization as a catalyst for asymmetric hydrogen-transfer reaction
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An L-threonine-based helical poly(N-propargylamide)-Ru complex was synthesized, and used as a catalyst for hydrogen-transfer reaction of ketones. The enantiomeric excess (ee) values of the formed alcohols ranged from 12 to 36%. On the other hand, an Ru complex with a low-molecular-weight model ligand gave an alcohol with ee as low as 1.8%. Copyright
- Sanda, Fumio,Araki, Hitoshi,Masuda, Toshio
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- Preparation of Enantiomerically Pure (S)-(?)-1-(1′-naphthyl)-ethanol by the Fungus Alternaria alternata
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(S)-(?)-1-(1′-napthyl)-ethanol (S-NE) is an important intermediate for the preparation of mevinic acid analogs, which is used for the treatment of hyperlipidemia. The objectives of the study were to isolate a microorganism that could effectively reduce 1-acetonaphthone (1-ACN) to S-NE, to determine the influence that the physicochemical parameters would have on the reduction by the isolated microorganism, and to attempt large-scale studies with the microorganism. Over the years fungi have been considered a promising biocatalyst and it has been presumed that many fungal species have not been isolated and therefore the current study focused on possible isolation of these microorganisms. A total of 72 fungal isolates were screened for their ability to reduce 1-ACN to its corresponding alcohol. The isolate, EBK-62, identified as Alternaria alternata, was found to be the most successful at reducing the ketone to the corresponding alcohol in the submerged culture. The reaction conditions were systematically optimized for the reducing agent A. alternata EBK-62, which showed high stereospecificity and good conversion for the reduction. The preparative scale study was carried out in a 2?L bioreactor and a total of 4.9?g of S-NE in optically pure form (>99% enantiomeric excess) was produced in 48?h. Chirality 28:669–673, 2016.
- Zilbeyaz, Kani,Kurbanoglu, Esabi Basaran,Kilic, Hamdullah
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- One-pot synthesis of (R)-1-(1-naphthyl)ethanol by stereoinversion using Candida parapsilosis
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(R)-1-(1-Naphthyl)ethanol is an essential chiral substrate for the synthesis of nonactin and dihydro-[1H]-quinoline-2-one derivatives. Stereoinversion of (S)-1-(1-naphthyl)ethanol to (R)-1-(1-naphthyl)ethanol by whole cell biocatalysis, using Candida parapsilosis, is reported here. Candida parapsilosis possesses a requisite redox system for the stereoinversion of secondary alcohol. The reaction conditions (temperature, time, pH, organic solvent, etc.) significantly influenced the stereoinversion process. Optimum conditions were found to be the reaction temperature of 30 C, a cellmass concentration of 200 mg/mL, pH 7 (phosphate buffer, 50 mM), a shaking speed of 200 rpm, and a 12 h reaction time. Under these optimum conditions, (R)-1-(1-naphthyl)ethanol was obtained in 100% eeR and 88% yield.
- Amrutkar, Suyog Madhav,Banoth, Linga,Banerjee, Uttam Chand
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- Synthesis and chiroptical properties of organometallic complexes of helicenic N-heterocyclic carbenes
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Novel [4, 6]helicenes (4a,b) bearing a fused imidazolium unit have been prepared from [4, 6]helicene-2,3-di-n-propyl-amines 3a,b. The in situ formation of N-heterocyclic carbene (NHC) derivatives followed by their complexation to iridium(I) or rhodium(I) gave access to complexes 1a, 1′a, and 1b, containing mono-coordinated helicene-NHC, chloro and COD (COD = 1,5-cyclooctadiene) ligands. Ir and Rh complexes 1a and 1′a were characterized by X-ray crystallography. HPLC and NMR analyses showed that Ir(I) complex 1b existed as a mixture of two diastereomeric complexes corresponding to enantiomeric pairs M-(?)/P-(+)-1b1 and M-(?)/P-(+)-1b2 which differ by the position of COD through space. The chiroptical properties (electronic circular dichroism and optical rotation) of the four stereoisomers were measured. These complexes were also tested as catalysts in a transfer hydrogenation reaction.
- Hafedh, Nesrine,Favereau, Ludovic,Caytan, Elsa,Roisnel, Thierry,Jean, Marion,Vanthuyne, Nicolas,Aloui, Faouzi,Crassous, Jeanne
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- A Simple Method for enriching the Enantiomeric Purity of a Functional Molecule already Rich in One Enantiomer
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1-Naphth-1-ylethanol 1 of 92percent enantiomeric excess (e.e.) can be raised to 99.6percent e.e. in an overall yield of 78percent by attaching it to oxalyl chloride, separating the lk diester from the ul by crystallisation, and hydrolysing the diester; the method is potentially general for functional molecules that can easily be attached to and then taken off a bifunctional reagent.
- Fleming, Ian,Ghosh, Sunil K.
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- Synthesis of thiolato bridged dimeric rhodium(III) triphenylphosphine complex via C–S bond cleavage: X-ray structure, DFT computation and catalytic evaluation towards transfer hydrogenation of ketones
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Herein, we have synthesized a new dimeric rhodium(III) triphenylphospine complex, [Rh2(PPh3)2(L)2Cl2] (1) via sp3(C)–S bond cleavage of a thioether containing ligand, 1-(((2-(ethylthio)phenyl)diazenyl)methyl)naphthalen-2-ol (L-CH2CH3). The complex was thoroughly characterized by using various spectroscopic techniques. Dimeric structure with distorted octahedral geometry of each of the rhodium center is confirmed by single crystal X-ray diffraction method. Catalytic efficiency of the complex towards transfer hydrogenation of ketones is studied in i-PrOH. Electronic structure and UV–vis spectrum of the complex are interpreted by DFT and TDDFT computations.
- Roy, Puspendu,Naskar, Rahul,Manna, Chandan Kumar,Mondal, Tapan Kumar
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- Reducing ability of supramolecular C60 dianion toward C=O, C=C and N-N bonds
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Different from C60 dianion which readily reacts with electrophiles, supramolecular C60 dianion (2) generated from γ-cyclodextrin-bicapped C60 (1) and NaBH4 (or diborate) in DMSO-H2O (9:1, v/v) is able to reduce N-N+, C=C-EWG and C=O bonds to provide the respective dihydro derivatives; 1-mediated reduction of acetophenone with NaBH4 in the presence of (Me 2N)2CH2 and EtONa gives turn over frequency (TOF)/h of 400. The Royal Society of Chemistry 2005.
- Takekuma, Shin-Ichi,Takekuma, Hideko,Yoshida, Zen-Ichi
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- Synthesis and α-adrenergic activities of 2- and 4-substituted imidazoline and imidazole analogues
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Seven analogues of medetomidine and naphazoline were synthesized and evaluated for their α1 (aorta) and α2 (platelet) activities. The analogues were composed of 2- and 4-substituted imidazoles and imidazolines attached through a methylene bridge to either the 1- or 2-naphthalene ring system. In general the 1-naphthalene analogues were the most potent inhibitors of epinephrine-induced platelet aggregation. Of considerable interest was the fact that the 1-naphthalene analogues (2, 5-7) were partial agonists while the 2-naphthalene analogues (3, 8, 9) were antagonists in an α1-adrenergic system (aorta). Thus, appropriately substituted naphthalene analogues of medetomidine and naphthazoline provide a spectrum of α1- agonist, α1-antagonist, and α2-antagonist activity.
- Amemiya,Hong,Venkataraman,Patil,Shams,Romstedt,Feller,Hsu,Miller
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- Chiral Recognition and Molecular Interaction in Cellulose Derivatives
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Nineteen 1,3-bis(aryl)propane derivatives and six model compounds with a single chromophore were used to explore the chiral discrimination ability of cellulose derivatives, in particular cellulose triphenylcarbamate (CTC), in connection with the mode of interaction of these probe molecules with adsorbents.The interaction was evaluated by conformational analysis of the probe molecules and circular dichroism.The 1,3-bis(aryl)propanes with 9-anthryl moieties possessed a highly limited conformation owing to the bulky substituent and hardly changed their shape on CTCas evidenced by CD spectra; thus, they may be regarded as "rigid" substrates.However, these "rigid" substrates were resolved quite effectively.On the other hand, those with 2-naphthyl moieties possessed a number of stable conformations and could change their shape in diastereomeric complexes on CTC; thus, they may be assumed as "soft" substrates, against which the chiral discrimination was inefficient.The present study revealed that the optical resolution may be interpreted at least partly in terms of the "rigid" and "soft" concept.
- Itoh, Kenji,Ikeda, Tomiki,Tazuke, Shigeo,Shibata, Tohru
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- Ligand-Assisted Rate Acceleration in Transacylation by a Yttrium - Salen Complex. Demonstration of a Conceptually New Strategy for Metal-Catalyzed Kinetic Resolution of Alcohols
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(matrix presented) Yttrium-salen complexes effect transacylation between enolesters and chiral secondary alcohols, resulting in varying degrees of kinetic resolution. Even though the enantioselectivity remains modest (kfast/kslow up to 4.81), these results represent the first demonstration of a conceptually new metal-catalyzed acyl transfer process that results in kinetic resolution. On the basis of the solid-state structure of the catalyst, a novel associative mechanistic pathway is proposed for the reaction.
- Lin, Mei-Huey,RajanBabu
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- Synthesis of a rhodium(III) triphenylphosphine complex via C–S bond cleavage of an azo-thioether ligand: X-ray structure, electrochemistry and catalysis towards transfer hydrogenation of ketones
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A new rhodium(III) triphenylphosphine complex having the general formula [Rh(PPh3)2(L)Cl] (1) was synthesized by C–S bond cleavage of an ONS donor azo-thioether ligand (L-CH2Ph). The complex was thoroughly characterized by various spectroscopic techniques. Its single crystal X-ray structure exhibits an octahedral geometry around the rhodium(III) center. A cyclic voltammogram of the complex exhibits ligand based quasi-irreversible oxidative and reductive responses. The electronic structure, redox properties and electronic excitations in the complex were interpreted by DFT and TDDFT calculations. The complex effectively catalyzed the transfer hydrogenation reaction of ketones with high yields in i-PrOH in the presence of a base.
- Roy, Puspendu,Manna, Chandan Kumar,Naskar, Rahul,Mondal, Tapan Kumar
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- "Achiral" benzophenone ligand for highly enantioselective Ru catalysts in ketone hydrogenation
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The chirality of an "achiral" benzophenone-based complex can be controlled. The benzophenone-based complex thus controlled affords high enantioselectivity in the catalytic asymmetric ketone hydrogenation (up to 99% ee, >99% yield).
- Mikami, Koichi,Wakabayashi, Kazuki,Aikawa, Kohsuke
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- A cyclochiral conformational motif constructed using a robust hydrogen-bonding network
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A novel conformational motif constructed with a robust intramolecular hydrogen-bonding (H-bonding) network was discovered. A pyrrolidine derivative possessing four identical amide substituents at C(2) and C(5) formed a strong intramolecular H-bonding network consisting of all the amide groups. This conformation yielded a cyclochiral structure with a handedness that depended on the directionality of the H-bonding network. The most stable compound was isolated and applied to the acylative kinetic resolution of secondary alcohol. The handedness of the H-bonding network was biased by the presence of chiral substituents, and the preferred direction could be switched under an external stimulus. A structural analysis using NMR, X-ray crystallography, and theoretical calculation techniques indicated that the conformation of the substituents was highly ordered and depended on the directionality of the H-bonding network.
- Mishiro, Kenji,Furuta, Takumi,Sasamori, Takahiro,Hayashi, Kazuhiro,Tokitoh, Norihiro,Futaki, Shiroh,Kawabata, Takeo
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- Applications of imino-pyridine Ni(II) complexes as catalysts in the transfer hydrogenation of ketones
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Five imino-pyridine Ni(II) complexes: [{Ni(L1)Cl2}2] Ni1; [{Ni(L2)Cl2}2] Ni2; [{Ni(L3)Cl2}2] Ni3; [{Ni(L4)Cl2}2] Ni4 and [Ni(L5)2Cl2] Ni5 derived from ligands 2,6-diisopropyl-N-[(pyridin-2-yl) methylene] aniline (L1); 2,6-diisopropyl-N-[(pyridin-2-yl) ethylidene]aniline (L2); 2,6-dimethyl-N-[(pyridin-2-yl) methylene] aniline (L3); 2,6-dimethyl-N-[(pyridin-2-yl) ethylidene] aniline (L4) and N-[(pyridin-2-yl) methylene] aniline (L5) were evaluated as catalysts in the transfer hydrogenation of ketones. The Ni(II) complexes demonstrated moderate catalytic activities giving a turnover number (TON) of up to 126 at catalyst loading of 0.5 mol%. The structure of the complexes and nature of ketone substrate influenced the catalytic activities of the complexes. Deactivation studies using mercury and sub-stoichiometric poisoning experiments pointed to the presence of both Ni(0) nanoparticles and Ni(II) homogeneous as the active species.
- Tsaulwayo, Nokwanda,Kumah, Robert.T.,Ojwach, Stephen.O.
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- Conformationally flexible biphenylphosphane ligands for Ru-catalyzed enantioselective hydrogenation
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Stereomutation of a BIPHEP/RuCl2/diamine complex (shown schematically) is possible because of the conformational flexibilty of BIPHEP ligands. The result is an asymmetric activation in the Ru-catalyzed hydrogenation of carbonyl compounds to optically active alcohols. Whereas a racemic BINAP/RuCl2 complex with a chiral diamine activator gives a 1:1 mixture of two diastereomers, unequal amounts of the diastereomers can be produced from a BIPHEP/RuCl2 complex and a chiral diamine. Ar = 3,5-dimethylphenyl, BINAP = 2,2'-bis(diphenylphosphanyl)-1,1'-binaphthyl, BIPHEP = 2,2'- bis(diarylphosphanyl)biphenyl.
- Mikami, Koichi,Korenaga, Toshinobu,Terada, Masahiro,Ohkuma, Takeshi,Pham, Trang,Noyori, Ryoji
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- Functional-group attachment and interconversion at a chiral [3]ferrocenophane framework
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Mannich condensation of 1,1′-diacetylferrocene with dimethylamine followed by catalytic hydrogenation gives the chiral α-dimethylamino[3] ferrocenophane. Both enantiomers are available by resolution. Directed ortho-lithiation/iodination yields the ]ortho-iodo-α-dimethylamino[3] ferrocenophane derivative, whose treatment with acetic anhydride and copper(I) oxide yielded the mono- and diacetoxy-functionalized derivatives. The ortho-phosphorylated α-dimethylamino systems (-PPh2, -PCy 2) underwent exchange of the directing NMe2 group with NH2 by means of an ammonolysis reaction of the corresponding α-chloride derivatives, which in turn were obtained by treatment of the α-dimethylamino compounds with methylchloroformate. Starting from α-dimethylamino[3]ferrocenophane, the sequence of directed ortho-lithiation (t-BuLi), treatment with p-tosyl azide/sodium pyrophosphate (to yield the ortho-azido[3]ferrocenophane derivative) followed by catalytic hydrogenation gave the ortho-amino and α-dimethylamino[3]ferrocenophane derivatives. The potential use of some of the chelate ferrocenophane ligands in Ru-catalyzed asymmetric hydrogenations was investigated. Seven of the newly synthesized compounds were characterized by X-ray diffraction. Georg Thieme Verlag Stuttgart.
- Nilewski, Christian,Neumann, Markus,Tebben, Ludger,Froehlich, Roland,Kehr, Gerald,Erker, Gerhard
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- Achiral benzophenone ligand-rhodium complex with chiral diamine activator for high enantiocontrol in asymmetric transfer hydrogenation
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The chirality of an achiral benzophenone-based rhodium complex can be controlled by chiral diamines to afford significantly high enantioselectivity in the catalytic asymmetric transfer hydrogenation of ketones (up to 99% ee, 99% yield). The Royal Society
- Mikami, Koichi,Wakabayashi, Kazuki,Yusa, Yukinori,Aikawa, Kohsuke
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- Synthesis and characterization of a ruthenium complex with bis(diphenylphosphino)propane and thioether containing ONS donor ligand: Application in transfer hydrogenation of ketones
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The synthesis and characterization of a mixed ligand Ru(II) complex, [Ru(dppp)(L)Cl] (1) (where, dppp?=?bis(diphenylphosphino) propane) is reported. The distorted octahedral geometry of the complex is confirmed by X-ray diffraction method. Cyclic voltammogram in CH3CN exhibits Ru(II)/Ru(III) quasireversible oxidation couple along with reversible azo-bond reductions peaks with reference to Ag/AgCl electrode. The efficiency of the complex towards the transfer hydrogenation of ketones in i-PrOH is examined and an excellent catalytic conversion (90–98%) is observed. The electronic structure and redox properties are well corroborated with the DFT calculations.
- Biswas, Sujan,Sarkar, Deblina,Roy, Puspendu,Mondal, Tapan Kumar
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- New Rh(III) complexes of 5-methyl-5-(pyridyl)-2,4-imidazolidenedione: Synthesis, X-ray structure, electrochemical study and catalytic behaviour for hydrogenation of ketones
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We describe the reaction of anion [RhCl6]3? with a series of hydantoin ligands (HL1, HL2 and HL3?=?5-methyl-5-(2-, 3- and 4-pyridyl)-2,4-imidazolidenedione, respectively). Based on spectroscopic, cyclic voltammetric, elemental and MS
- Sabounchei, Seyyed Javad,Sayadi, Mohsen,Hashemi, Mojdeh Sadat,Hashemi, Ali,Nematollahi, Davood,Salahifar, Eslam,Gable, Robert W.
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- Asymmetric hydrogenation of aromatic ketones using polymeric catalyst prepared from polymer-supported 1,2-diamine
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tert-Butyloxycarbonyl (Boc) protected chiral 1,2-diamine monomers 3 were copolymerized with achiral vinyl monomers such as styrene, methacrylates, acrylates, methacrylamide, and acrylamide to give crosslinked polymers P2 containing chiral 1,2-diamine moie
- Itsuno, Shinichi,Chiba, Masahiro,Takahashi, Miyuki,Arakawa, Yukihiro,Haraguchi, Naoki
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- Enantioselective cyanation of benzylic C-H bonds via copper-catalyzed radical relay
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Direct methods for stereoselective functionalization of sp-hybridized carbon-hydrogen [C(sp3)-H] bonds in complex organic molecules could facilitate much more efficient preparation of therapeutics and agrochemicals. Here, we report a copper-catalyzed radical relay pathway for enantioselective conversion of benzylic C-H bonds into benzylic nitriles. Hydrogen-atom abstraction affords an achiral benzylic radical that undergoes asymmetric C(sp3)-CN bond formation upon reaction with a chiral copper catalyst. The reactions proceed efficiently at room temperature with the benzylic substrate as limiting reagent, exhibit broad substrate scope with high enantioselectivity (typically 90 to 99% enantiomeric excess), and afford products that are key precursors to important bioactive molecules. Mechanistic studies provide evidence for diffusible organic radicals and highlight the difference between these reactions and C-H oxidations mediated by enzymes and other catalysts that operate via radical rebound pathways.
- Zhang, Wen,Wang, Fei,McCann, Scott D.,Wang, Dinghai,Chen, Pinhong,Stahl, Shannon S.,Liu, Guosheng
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- Axial chirality in biaryl N,N-dialkylaminopyridine derivatives bearing an internal carboxy group
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Axial chirality in N,N-dimethylaminopyridines as well as N,N-dipropylaminopyridines bearing an internal carboxy group were evaluated based on their racemization barriers and circular dichroism spectra. The half-life of racemization of N,N-dipropylaminopyridine derivative 2 was estimated to be 19.7 days at 20°C. Its enantiomers isolated as optically active forms showed positive-negative and negative-positive Cotton effects for (+)-2 and (?)-2, respectively, from 310 to 210 nm. Furthermore, (?)-2 was applied as a chiral nucleophilic catalyst and exhibited asymmetric induction in acylative kinetic resolution of 1-(1-naphthyl)ethane-1-ol.
- Nishino, Reiko,Hamada, Shohei,Elboray, Elghareeb E.,Ueda, Yoshihiro,Kawabata, Takeo,Furuta, Takumi
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- Osmium-hydride-carbonyl complex with thioether containing Schiff base ligand: Synthesis, crystal structure, electrochemistry and catalytic transfer hydrogenation
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A new osmium(II) carbonyl complex, [Os(H)(CO)(PPh3)2(L)] (1) with thioether containg NNS donor ligand (where L = 2-(ethylthio)-N-((pyridine-2-yl)methylene))benzenamine) is synthesized and characterized by various spectroscopic techniques. The distorted octahedral environment around osmium in the complex is confirmed by single crystal X-ray structure. Cyclic voltammogram in acetonitrile exhibits Os(II)/Os(III) oxidation and ligand based reduction. The complex effectively catalyzed the transfer hydrogenation reaction of ketones in high yields in i-PrOH. The electronic structure and redox properties are interpreted by DFT studies.
- Biswas, Sujan,Roy, Puspendu,Jana, Subrata,Mondal, Tapan Kumar
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- Catechol-type ligand containing new modular design dioxaborinane compounds: Use in the transfer hydrogenation of various ketones
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A novel class of tricoordinate dioxaborinane compounds, which have the general formula [B1(L1–5)] and [B2(L1–5)], were designed and synthesized by the corresponding catechol-type ligands (L1–L5) at ambient temperature. All the new compounds were fully characterized by NMR (1H, 13C, and 11B), FT-IR, UV–vis, LC-MS spectroscopy, and melting point analysis and microanalysis. The dioxaborinane [B1(L1–5)] and [B2(L1–5)] compounds were investigated as catalyst for the transfer hydrogenation of various ketones under suitable conditions. Particularly, it was proved that the ferrocene-based dioxaborinane [B1(L1–5)] molecules can afford an efficient catalytic conversion compared to corresponding 3,5-bis(trifluoromethyl)phenyl-based [B2(L1–5)] dioxaborinanes in transfer hydrogenation catalytic studies.
- Kilic, Ahmet,Kaya, ?brahim Halil,Ozaslan, Ismail,Aydemir, Murat,Durap, Feyyaz
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- An efficient phosphorous-containing oxazoline ligand derived from cis-2-amino-3,3-dimethyl-1-indanol: Application to the rhodium-catalyzed enantioselective hydrosilylation of ketones
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Enantiopure 2-[2-(diphenylphosphino)phenyl]oxazoline, derived from a non-natural amino alcohol, cis-2-amino-3,3-dimethyl-1-indanol, was found to be an efficient ligand for the rhodium-catalyzed enantioselective hydrosilylation of ketones.
- Sudo, Atsushi,Yoshida, Hiroaki,Saigo, Kazuhiko
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- cis-2-Amino-1-acenaphthenol: Practical Resolution and Application to the Catalytic Enantioselective Reduction of Ketones
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The chiral amino alcohol, cis-2-amino-1-acenaphthenol, was resolved via its (R)-2-phenylpropionic acid salt.This amino alcohol was used as the precursor of a chiral oxazaborolidine, which was an efficient chiral catalyst in the asymmetric reduction of pro
- Sudo, Atsushi,Matsumoto, Masaru,Hashimoto, Yukihiko,Saigo, Kazuhiko
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- Visible-Light-Driven Catalytic Deracemization of Secondary Alcohols
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Deracemization of racemic chiral compounds is an attractive approach in asymmetric synthesis, but its development has been hindered by energetic and kinetic challenges. Here we describe a catalytic deracemization method for secondary benzylic alcohols which are important synthetic intermediates and end products for many industries. Driven by visible light only, this method is based on sequential photochemical dehydrogenation followed by enantioselective thermal hydrogenation. The combination of a heterogeneous dehydrogenation photocatalyst and a chiral molecular hydrogenation catalyst is essential to ensure two distinct pathways for the forward and reverse reactions. These reactions convert a large number of racemic aryl alkyl alcohols into their enantiomerically enriched forms in good yields and enantioselectivities.
- Hu, Xile,Zhang, Zhikun
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supporting information
p. 22833 - 22838
(2021/09/09)
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- PQXdpap: Helical Poly(quinoxaline-2,3-diyl)s Bearing 4-(Dipropylamino)pyridin-3-yl Pendants as Chirality-Switchable Nucleophilic Catalysts for the Kinetic Resolution of Secondary Alcohols
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Helically chiral poly(quinoxaline-2,3-diyl)s bearing 4-(dipropylamino)pyridin-3-yl pendants at the 5-position of the quinoxaline ring (PQXdpap) exhibited high catalytic activities and moderate to high selectivities (up to s = 87) in the acylative kinetic resolution of secondary alcohols. The solvent-dependent helical chirality switching of PQXdpap between pure toluene and a 1:1 mixture of toluene and 1,1,2-trichloroethane enabled the preparation of either compound of a pair of enantiomerically pure alcohols (>99% ee) from a single catalyst.
- Murakami, Ryo,Suginome, Michinori,Yamamoto, Takeshi
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supporting information
p. 8711 - 8716
(2021/11/24)
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- Effectiveness and Mechanism of the Ene(amido) Group in Activating Iron for the Catalytic Asymmetric Transfer Hydrogenation of Ketones
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I-interacting ligands of the diphosphino amido-ene(amido) type are effective in activating iron to resemble the properties of precious metals in the catalytic asymmetric transfer hydrogenation of ketones. To further verify the effectiveness of the ene(amido) group, we synthesized four amine(imine) diphosphine iron precatalyst complexes with substituents at α and β positions relative to imino groups (1-3) or with enlarged chelate ring sizes (5,5,6-membered rings) (4). In comparison with the parent trans-(R,R)-[Fe(CO)(Cl)(PPh2CH2CHaNCHPhCHPhNHCH2CH2PPh2)]BF4 (I), the introduction of a methyl group in 1 and 2 reduced the catalytic activity but led to undiminished enantioselectivity as reaction proceeded. In comparison to the iron complexes 1-3 with a 5,5,5-coordination geometry, the complex 4 derived from the new (R,R)-P-NH-NH2 tridentate ligand showed high reactivity comparable to that of I but was unfortunately not enantioselective. The catalytic reactivity of 1, 2, and 4 illustrates the effectiveness of the ene(amido) group. An electronic structure study on the important catalytic intermediate amido-ene(amido) complex 1b proved that iron was activated by an additional I-back-donation-interaction ligand to participate in the traditional metal-ligand bifunctional pathway in the asymmetric transfer hydrogenation reactions.
- Xue, Qingquan,Wu, Rongliang,Wang, Di,Zhu, Meifang,Zuo, Weiwei
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supporting information
p. 134 - 147
(2021/02/05)
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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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supporting information
p. 1415 - 1418
(2020/11/20)
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- Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
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A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often-used ruthenium half-sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.
- Oestreich, Martin,Seliger, Jan
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p. 247 - 251
(2020/10/29)
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- Enantioselective direct, base-free hydrogenation of ketones by a manganese amido complex of a homochiral, unsymmetrical P-N-P′ ligand
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The use of manganese in homogeneous hydrogenation catalysis has been a recent focus in the pursuit of more environmentally benign base metal catalysts. It has great promise with its unique reactivity when coupled with metal-ligand cooperation of aminophosphine pincer ligands. Here, a manganese precatalyst Mn(P-N-P′)(CO)2, where P-N-P′ is the amido form of the ligand (S,S)-PPh2CHPhCHPhNHCH2CH2PiPr2, has been synthesized and used for base-free ketone hydrogenation. This catalyst shows exceptionally high enantioselectivity and good activity, with tolerance for base-sensitive substrates. NMR structural analysis of intermediates formed by the reaction of the amido complex with hydrogen under pressure identified a reactive hydride with an NOE contact with the syn amine proton. Computational analysis of the catalytic cycle reveals that the heterolytic splitting of dihydrogen across the MnN bond in the amido complex has a low barrier while the hydride transfer to the ketone is the turnover-limiting step. The pro-S transition state is found to be usually much lower in energy than the pro-R transition state depending on the ketone structure, consistent with the high (S) enantiomeric excess in the alcohol products. The energy to reach the transition state is higher for the distortion of the in-coming ketone than that of the hydride complex. In a one-to-one comparison with the similar iron catalyst FeH2(CO)(P-NH-P′), the manganese catalyst is found to have higher enantioselectivity, often over 95% ee, while the iron catalyst has higher activity and productivity. An explanation of these differences is provided on the basis of the more deformable iron hydride complex due to the smaller hydride ligands.
- Seo, Chris S. G.,Tsui, Brian T. H.,Gradiski, Matthew V.,Smith, Samantha A. M.,Morris, Robert H.
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p. 3153 - 3163
(2021/05/25)
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- Nickel-Mediated Enantiospecific Silylation via Benzylic C-OMe Bond Cleavage
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Benzylic stereocenters are found in bioactive and drug molecules, as enantiopure benzylic alcohols have been used to build such a stereogenic center, but are limited to the construction of a C-C bond. Silylation of alkyl alcohols has the potential to build bioactive molecules and building blocks; however, the development of such a process is challenging and unknown. Herein, we describe an unprecedented AgF-assisted nickel catalysis in the enantiospecific silylation of benzylic ethers.
- Balakrishnan, Venkadesh,Murugesan, Vetrivelan,Chindan, Bincy,Rasappan, Ramesh
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supporting information
p. 1333 - 1338
(2021/02/20)
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- Tridentate nitrogen phosphine ligand containing arylamine NH as well as preparation method and application thereof
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The invention discloses a tridentate nitrogen phosphine ligand containing arylamine NH as well as a preparation method and application thereof, and belongs to the technical field of organic synthesis. The tridentate nitrogen phosphine ligand disclosed by the invention is the first case of tridentate nitrogen phosphine ligand containing not only a quinoline amine structure but also chiral ferrocene at present, a noble metal complex of the type of ligand shows good selectivity and extremely high catalytic activity in an asymmetric hydrogenation reaction, meanwhile, a cheap metal complex of the ligand can also show good selectivity and catalytic activity in the asymmetric hydrogenation reaction, and is very easy to modify in the aspects of electronic effect and space structure, so that the ligand has huge potential application value. A catalyst formed by the ligand and a transition metal complex can be used for catalyzing various reactions, can be used for synthesizing various drugs, and has important industrial application value.
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Paragraph 0095-0102; 0105-0109
(2021/06/26)
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- Ferrocene derivative metal organic complex as well as preparation method and application thereof
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The invention relates to the technical field of organic synthesis, in particular to a ferrocene derivative metal organic complex and a preparation method and application thereof. The ferrocene derivative metal organic complex disclosed by the invention is shown I, contains a pincerlike ligand in the structure, and therefore has high stability and long service life. , The ferrocene derivative type metal organic complex has high catalytic activity, and only 0.001 μM % - 0.01 μM % is used, so that the chiral compound can be efficiently and rapidly prepared. The ferrocene derivative metal organic complex central metal is ruthenium, the economic cost is low, and the method has the prospect of industrial popularization.
- -
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Paragraph 0147-0157
(2021/12/07)
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- Catalytic Aldehyde and Alcohol Arylation Reactions Facilitated by a 1,5-Diaza-3,7-diphosphacyclooctane Ligand
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We report a catalytic method to access secondary alcohols by the coupling of aryl iodides. Either aldehydes or alcohols can be used as reaction partners, making the transformation reductive or redox-neutral, respectively. The reaction is mediated by a Ni catalyst and a 1,5-diaza-3,7-diphosphacyclooctane. This P2N2ligand, which has previously been unrecognized in cross-coupling and related reactions, was found to avoid deleterious aryl halide reduction pathways that dominate with more traditional phosphines and NHCs. An interrupted carbonyl-Heck type mechanism is proposed to be operative, with a key 1,2-insertion step forging the new C-C bond and forming a nickel alkoxide that may be turned over by an alcohol reductant. The same catalyst was also found to enable synthesis of ketone products from either aldehydes or alcohols, demonstrating control over the oxidation state of both the starting materials and products.
- Isbrandt, Eric S.,Nasim, Amrah,Newman, Stephen G.,Zhao, Karen
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supporting information
p. 14646 - 14656
(2021/09/18)
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- Pd-catalyzed allylative dearomatisation using Grignard reagents
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Pd-catalyzed allylative dearomatisation of naphthyl halides is shown to be feasible by employing Grignard reagents. The high reactivity of the nucleophile allows for fast reactions and low catalyst loading, while a plethora of successfully substituted compounds illustrate the broad scope. Five membered heteroaromatic compounds are also demonstrated to be reactive under similar conditions.
- Boldrini, Cosimo,Harutyunyan, Syuzanna R.
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supporting information
p. 11807 - 11810
(2021/11/30)
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- Fe-Catalyzed Anaerobic Mukaiyama-Type Hydration of Alkenes using Nitroarenes
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Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama-type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe-catalyzed anaerobic Markovnikov-selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov-selectivity. The method features large functional group tolerance and is also applicable for late-stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
- Bhunia, Anup,Bergander, Klaus,Daniliuc, Constantin Gabriel,Studer, Armido
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supporting information
p. 8313 - 8320
(2021/03/08)
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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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- 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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- Selective C-alkylation Between Alcohols Catalyzed by N-Heterocyclic Carbene Molybdenum
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The first implementation of a molybdenum complex with an easily accessible bis-N-heterocyclic carbene ligand to catalyze β-alkylation of secondary alcohols via borrowing-hydrogen (BH) strategy using alcohols as alkylating agents is reported. Remarkably high activity, excellent selectivity, and broad substrate scope compatibility with advantages of catalyst usage low to 0.5 mol%, a catalytic amount of NaOH as the base, and H2O as the by-product are demonstrated in this green and step-economical protocol. Mechanistic studies indicate a plausible outer-sphere mechanism in which the alcohol dehydrogenation is the rate-determining step.
- Liu, Jiahao,Li, Weikang,Li, Yinwu,Liu, Yan,Ke, Zhuofeng
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supporting information
p. 3124 - 3128
(2021/09/20)
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- Synthesis and structural elucidation of (pyridyl)imine Fe(II) complexes and their applications as catalysts in transfer hydrogenation of ketones
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Reactions of (pyridyl)imine ligands: 2,6-diisopropyl-N-[(pyridine-2-yl)methylene]aniline (L1), 2,6-diisopropyl-N-[(pyridine-2-yl)ethylidene]aniline (L2), 2,6-dimethyl-N-[(pyridine-2-yl)methylene]aniline (L3), 2,6-dimethyl-N-[(pyridine-2-yl)ethylidene]aniline (L4) and N-[(pyridine-2-yl)methylene]aniline (L5) with FeCl2 salt afforded the corresponding paramagnetic Fe(II) complexes [Fe(L1)2Cl][FeCl4] (Fe1), [Fe(L2)2Cl][FeCl4] (Fe2), [Fe(L3)2Cl][FeCl4] (Fe3), [Fe(L4)2Cl][FeCl4], (Fe4), [Fe(L5)2Cl2] (Fe5) in good yields. On the other hand, reactions of L1 with FeCl2 in the presence of NaPF6 afforded complex [Fe(L1)2Cl][PF6] (Fe6) in moderate yields. Molecular structures of complexes Fe1 and Fe2 reveal the formation of cationic species containing two N^N bidentate ligands and one chlorido co-ligand to give five-coordinate geometry with [FeCl4]? as counter-anion. On the other hand, complex Fe5, is an octahedral neutral species containing two bidentate L5 and two chlorido ligands. All the complexes (Fe1–Fe6) formed active catalysts in the transfer hydrogenation of ketones affording average yields of about 85%. The ligand architecture, reaction conditions and nature of substrate influenced the catalytic activities of the complexes. Mercury and subs-stoichiometric poisoning tests pointed to the existence of both Fe(0) nanoparticles and homogeneous Fe(II) species as the active intermediates.
- Tsaulwayo, Nokwanda,Kumah, Robert T.,Ojwach, Stephen O.
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- Achiral and chiral NNN-pincer nickel complexes with oxazolinyl backbones: application in transfer hydrogenation of ketones
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We describe the synthesis of new NNN-oxazolinyl-pincer nickel complexes and their application in the transfer hydrogenation of ketones. Achiral NNN-ligands, R′2-oxazolinyl-2-C6H4-NH-C(O)CH2NEt2[(
- Jagtap, Rahul A.,Ankade, Shidheshwar B.,Gonnade, Rajesh G.,Punji, Benudhar
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p. 11927 - 11936
(2021/07/17)
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- The catalytic activity of new iridium(I) N-heterocyclic carbene complexes for hydrogen transfer reaction of ketones
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In this paper, the reaction of [Ir(COD)Cl]2 with in situ prepared Ag–N-heterocyclic carbene (NHC) complexes yields a series of [IrCl(COD)(NHC)] complexes. All compounds were fully characterized by 1H NMR, 13C NMR, and FT–IR spectroscopy. The manuscript focused on the preparation of new Ir–NHC complexes, characterization and catalytic behavior. A series of hydrogenation transfer reactions were performed to reveal the effects of the Ir–NHC complexes. The new Ir–NHC complexes of benzimidazole-2-ylidene are effective catalysts for the transfer of hydrogenation of different ketones, using i-PrOH as the source of hydrogen in the presence of KOH. The reactions were conducted at a substrate/catalyst/base (S/C/base) molar ratio of 1:0.001:2. Although all of the complexes are active catalysts for the transfer hydrogenation of ketones, moderate yields were obtained with acetylnaphthalene and conversion was not observed with very substituted ketones such as 2′,3′,4′,5′,6′-pentamethylacetophenone. It was observed that for transfer hydrogenation reactions Ir–NHC catalysts were more active, compared to Ru–NHC catalyzed studies performed by our team. Graphic abstract: [Figure not available: see fulltext.].
- Karaca, Emine ?zge
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p. 287 - 293
(2021/02/09)
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- Asymmetric Catalytic Meerwein-Ponndorf-Verley Reduction of Ketones with Aluminum(III)-VANOL Catalysts
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We report herein an efficient aluminum-catalyzed asymmetric MPV reduction of ketones with broad substrate scope and excellent yields and enantiomeric inductions. A variety of aromatic (both electron-poor and electron-rich) and aliphatic ketones were converted to chiral alcohols in good yields with high enantioselectivities (26 examples, 70-98percent yield and 82-99percent ee). This method operates under mild conditions (-10 °C) and low catalyst loading (1-5 mol percent). Furthermore, this process is catalyzed by the earth-abundant main-group element aluminum and employs 2-propanol as the hydride source.
- Guan, Yong,Mohammadlou, Aliakbar,Staples, Richard,Sullivan, Ryan P.,Wulff, William D.,Yin, Xiaopeng,Zheng, Li
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p. 7188 - 7194
(2020/07/21)
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- RETRACTED ARTICLE: The Manganese(I)-Catalyzed Asymmetric Transfer Hydrogenation of Ketones: Disclosing the Macrocylic Privilege
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The bis(carbonyl) manganese(I) complex [Mn(CO)2(1)]Br (2) with a chiral (NH)2P2 macrocyclic ligand (1) catalyzes the asymmetric transfer hydrogenation of polar double bonds with 2-propanol as the hydrogen source. Ketones (43 substrates) are reduced to alcohols in high yields (up to >99 %) and with excellent enantioselectivities (90–99 % ee). A stereochemical model based on attractive CH–π interactions is proposed.
- Passera, Alessandro,Mezzetti, Antonio
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supporting information
p. 187 - 191
(2019/12/11)
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- C1-Symmetric PNP Ligands for Manganese-Catalyzed Enantioselective Hydrogenation of Ketones: Reaction Scope and Enantioinduction Model
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A family of ferrocene-based chiral PNP ligands is reported. These tridentate ligands were successfully applied in Mn-catalyzed asymmetric hydrogenation of ketones, giving high enantioselectivities (92%~99% ee for aryl alkyl ketones) as well as high efficiencies (TON up to 2000). In addition, dialkyl ketones could also be hydrogenated smoothly. Manganese intermediates that might be involved in the catalytic cycle were analyzed. DFT calculation was carried out to help understand the chiral induction model. The Mn/PNP catalyst could discriminate two groups with different steric properties by deformation of the phosphine moiety in the flexible 5-membered ring.
- Zeng, Liyao,Yang, Huaxin,Zhao, Menglong,Wen, Jialin,Tucker, James H. R.,Zhang, Xumu
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p. 13794 - 13799
(2020/11/30)
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- An iron variant of the Noyori hydrogenation catalyst for the asymmetric transfer hydrogenation of ketones
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We report the design of a new iron catalyst for the asymmetric transfer hydrogenation of ketones. This type of iron catalyst combines the structural characteristics of the Noyori hydrogenation catalyst (an axially chiral 2,2′-bis(phosphino)-1,1′-binaphthyl fragment and the metal-ligand bifunctional motif) and an ene(amido) group that can activate the iron center. After activation by 8 equivalents of potassiumtert-butoxide, (SA,RP,SS)-7aand (SA,RP,SS)-7bare active but nonenantioselective catalysts for the transfer hydrogenation of acetophenone and α,β-unsaturated aldehydes at room temperature in isopropanol. A maximum turnover number of 14480 was observed for (SA,RP,SS)-7ain the reduction of acetophenone. The right combination of the stereochemistry of the axially chiral 2,2′-bis(phosphino)-1,1′-binaphthyl group and the carbon-centered chiral amine-imine moiety in (SA,RP,RR)-7b′afforded an enantioselective catalyst for the preparation of chiral alcohols with moderate to good yields and a broad functional group tolerance.
- Huo, Shangfei,Wang, Qingwei,Zuo, Weiwei
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supporting information
p. 7959 - 7967
(2020/06/26)
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- Preparation method of R-1-(naphthalene-1-yl) ethanol
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The invention relates to a preparation method of R-1-(naphthalene-1-yl) ethanol. The preparation method comprises the following step: carrying out asymmetric hydrogenation reaction on 1-naphthyl ethylketone under the catalysis of a catalyst; and the catalyst has structural characteristics as shown in the following formula (I). The R-1-(naphthalene-1-yl) ethanol product prepared through the preparation method is higher in chiral purity; meanwhile, the high conversion rate is guaranteed, the reaction can be carried out under the lower pressure condition, large-scale production and application are facilitated, the adopted catalyst can be recycled, heavy metal pollution is avoided, and the cost is reduced.
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Paragraph 0072-0126
(2020/09/09)
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- New chiral stationary phases for liquid chromatography based on small molecules: Development, enantioresolution evaluation and chiral recognition mechanisms
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Recently, we reported the development of new chiral stationary phases (CSPs) for liquid chromatography (LC) based on chiral derivatives of xanthones (CDXs). Based on the most promising CDX selectors, 12 new CSPs were successfully prepared starting from suitable functionalized small molecules including xanthone and benzophenone derivatives. The chiral selectors comprising one, two, three, or four chiral moieties were covalently bonded to a chromatographic support and further packed into LC stainless-steel columns (150?×?2.1?mm I.D.). The enantioselective performance of the new CSPs was evaluated by LC using different classes of chiral compounds. Specificity for enantioseparation of some CDXs was observed in the evaluation of the new CSPs. Besides, assessment of chiral recognition mechanisms was performed by computational studies using molecular docking approach, which are in accordance with the chromatographic parameters. X-Ray analysis was used to establish a chiral selector 3D structure.
- Phyo, Ye' Zaw,Teixeira, Joana,Tiritan, Maria Elizabeth,Cravo, Sara,Palmeira, Andreia,Gales, Luís,Silva, Artur M.S.,Pinto, Madalena M.M.,Kijjoa, Anake,Fernandes, Carla
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-
- Synthesis of cis-1,2-diol-type chiral ligands and their dioxaborinane derivatives: Application for the asymmetric transfer hydrogenation of various ketones and biological evaluation
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Two cis-1,2-diol-type chiral ligands (T1 and T2) and their tri-coordinated chiral dioxaborinane (T(1–2)B(1–2)) and four-coordinated chiral dioxaborinane adducts with 4-tert-butyl pyridine sustained by N → B dati
- Kilic, Ahmet,Balci, Tu?ba Ersayan,Arslan, Nevin,Aydemir, Murat,Durap, Feyyaz,Okumu?, Veysi,Tekin, Recep
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- Method for 1,1-aryl boronizing of terminal olefin through metal catalysis
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The invention discloses a method for 1,1-aryl boronizing of terminal olefin through metal catalysis. Under the action of a metal nickel catalyst NiA, a ligand and alkali, the terminal olefin, an arylhalide ArX and bis(pinacolato) diboron are dissolved in an organic solvent and react, and column chromatography separation purification is performed to obtain the 1,1-aryl boron compound with the structure abovementioned. According to the method, the 1,1-aryl boron compound with the structure can be efficiently synthesized, excellent regioselectivity and enantioselectivity are achieved, the product contains a boron group, and the method can be applied to conversion of boron to generate various benzyl alcohol compounds.
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Paragraph 0053-0055
(2020/08/09)
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- Enantioselective Hydroboration of Ketones Catalyzed by Rare-Earth Metal Complexes Containing Trost Ligands
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Four chiral dinuclear rare-earth metal complexes [REL1]2 (RE = Y(1), Eu(2), Nd(3), La (4)) stabilized by Trost proligand H3L1 (H3L1 = (S,S)-2,6-bis[2-(hydroxydiphenylmethyl)pyrrolidin-1-ylmethyl]-4-methylphenol) were first prepared, and all were characterized by X-ray diffraction. Complex 4 was employed as the catalyst for enantioselective hydroboration reaction of substituted ketones, and the corresponding secondary alcohols with excellent yields and high ee values were obtained using reductant HBpin. The same result was also achieved using the combination of lanthanium amides La[N(SiMe3)2]3 with Trost proligand H3L1 in a 1:1 molar ratio. The experimental findings and DFT calculation revealed the possible mechanism of the enantioselective hydroboration reaction and defined the origin of the enantioselectivity in the current system.
- Lu, Chengrong,Sun, Yuli,Xue, Mingqiang,Zhao, Bei
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p. 10504 - 10513
(2020/09/23)
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- Iridium-Catalyzed Enantioselective Transfer Hydrogenation of Ketones Controlled by Alcohol Hydrogen-Bonding and sp3-C?H Noncovalent Interactions
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Iridium-catalyzed enantioselective transfer hydrogenation of ketones with formic acid was developed using a prolinol-phosphine chiral ligand. Cooperative action of the iridium atom and the ligand through alcohol-alkoxide interconversion is crucial to facilitate the transfer hydrogenation. Various ketones including alkyl aryl ketones, ketoesters, and an aryl heteroaryl ketone were competent substrates. An attractive feature of this catalysis is efficient discrimination between the alkyl and aryl substituents of the ketones, promoting hydrogenation with the identical sense of enantioselection regardless of steric demand of the alkyl substituent and thus resulting in a rare case of highly enantioselective transfer hydrogenation of tert-alkyl aryl ketones. Quantum chemical calculations revealed that the sp3-C?H/π interaction between an sp3-C?H bond of the prolinol-phosphine ligand and the aryl substituent of the ketone is crucial for the enantioselection in combination with O?H???O/sp3-C?H???O two-point hydrogen-bonding between the chiral ligand and carbonyl group. (Figure presented.).
- Murayama, Hiroaki,Heike, Yoshito,Higashida, Kosuke,Shimizu, Yohei,Yodsin, Nuttapon,Wongnongwa, Yutthana,Jungsuttiwong, Siriporn,Mori, Seiji,Sawamura, Masaya
-
supporting information
p. 4655 - 4661
(2020/07/13)
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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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- Chiral amino-pyridine-phosphine tridentate ligand, manganese complex, and preparation method and application thereof
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The invention discloses a chiral amino-pyridine-phosphine tridentate ligand, a manganese complex, and a preparation method and application thereof. The chiral amino-pyridine-phosphine tridentate ligand is shown as a formula II, and the manganese complex of the chiral amino-pyridine-phosphine tridentate ligand can be used for efficiently catalyzing and hydrogenating ketone compounds to prepare chiral alcohol compounds in a high enantioselectivity mode. The chiral amino-pyridine-phosphine tridentate ligand and the manganese complex are simple in synthesis process, good in stability, high in catalytic activity and mild in reaction conditions.
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Paragraph 0597-0599; 0601
(2020/07/13)
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- Bottleable NiCl2(dppe) as a catalyst for the Markovnikov-selective hydroboration of styrenes with bis(pinacolato)diboron
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Although transition-metal-catalysed hydroboration reactions of alkenes have been extensively studied, only three examples using Ni complexes have been reported so far. In this study, we have examined hydroboration reactions of alkenes using Ni/phosphine complexes. The commercially available and bottleable complex NiCl2(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane) serves as a catalyst for the highly Markovnikov-selective hydroboration of styrene derivatives that affords the desired Markovnikov products in high yield.
- Hashimoto, Toru,Ishimaru, Toshiya,Shiota, Keisuke,Yamaguchi, Yoshitaka
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supporting information
p. 11701 - 11704
(2020/10/20)
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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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- N-Heterocyclic Carbene (NHC)-Stabilized Ru0 Nanoparticles: In Situ Generation of an Efficient Transfer Hydrogenation Catalyst
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Tethered and untethered ruthenium half-sandwich complexes were synthesized and characterized spectroscopically. X-ray crystallographic analysis of three untethered and two tethered Ru N-heterocyclic carbene (NHC) complexes were also carried out. These RuNHC complexes catalyze transfer hydrogenation of aromatic ketones in 2-propanol under reflux, optimally in the presence of (25 mol %) KOH. Under these conditions, the formation of 2–3 nm-sized Ru0 nanoparticles was detected by TEM measurements. A solid-state NMR investigation of the nanoparticles suggested that the NHC ligands were bound to the surface of the Ru nanoparticles (NPs). This base-promoted route to NHC-stabilized ruthenium nanoparticles directly from arene-tethered ruthenium–NHC complexes and from untethered ruthenium–NHC complexes is more convenient than previously known routes to NHC-stabilized Ru nanocatalysts. Similar catalytically active RuNPs were also generated from the reaction of a mixture of [RuCl2(p-cymene)]2 and the NHC precursor with KOH in isopropanol under reflux. The transfer hydrogenation catalyzed by these NHC-stabilized RuNPs possess a high turnover number. The catalytic efficiency was significantly reduced if nanoparticles were exposed to air or allowed to aggregate and precipitate by cooling the reaction mixtures during the reaction.
- Kathuria, Lakshay,Din Reshi, Noor U.,Samuelson, Ashoka G.
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supporting information
p. 7622 - 7630
(2020/05/29)
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- Group 6 Metal Carbonyl Complexes Supported by a Bidentate PN Ligand: Syntheses, Characterization, and Catalytic Hydrogenation Activity
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We report on the preparation of a series of phosphorus-nitrogen donor ligand complexes [M(CO)4(PN)], where M = Cr, Mo, W and PN is 2-(diphenylphosphino)ethylamine. The organometallic compounds were readily obtained upon reacting the respective metal hexacarbonyls with equimolar amounts of the pertinent ligand in the presence of tetraethylammonium bromide. The PN-ligated metal carbonyls were fully characterized by standard spectroscopic techniques and X-ray crystallography. The ability of the title compounds to function as homogeneous hydrogenation catalysts was probed in the reduction of acetophenone and benzaldehyde derivatives to yield the corresponding alcohols. The reaction setup was easily assembled by simply combining the components in the autoclave on the bench outside an inert-gas-operated glovebox system.
- Faust, Kirill,Topf, Christoph,Vielhaber, Thomas
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p. 4535 - 4543
(2020/12/23)
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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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- Aerobic Oxidative Cleavage and Esterification of C(OH)–C Bonds
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C(OH)–C bonds are widely distributed in naturally renewable biomass, such as carbohydrates, lignin, and their platform molecules. Selective cleavage and functionalization of C(OH)–C bonds is an attractive strategy in terms of producing value-added chemicals from biomass. However, effective transformation of alcohols into esters by activation of C(OH)–C bonds has not been achieved so far. Herein, for the first time, we report selective cleavage and esterification of C(OH)–C bonds, catalyzed by inexpensive copper salts, using environmentally benign oxygen as the oxidant, to afford methyl esters in excellent yields. A diverse range of phenylethanol derivatives that contain C(OH)–C bonds were effectively converted into methyl benzoates. Detailed analysis revealed that the high efficiency and selectivity resulted mainly from the fact that, in addition to the major esterification reaction, the side products (e.g., olefins and acids) were also transformed in situ into esters in the reaction system. C(OH)–C bonds are widely distributed in naturally renewable biomass. In the context of developing future biorefineries, selective cleavage and functionalization of C(OH)–C bonds are crucial and represent an attractive strategy in terms of producing value-added chemical compounds from biomass resources. In the current manuscript, we report, for the first time, an effective and selective method for the cleavage and esterification of C(OH)–C bonds of alcohols to produce esters, by using environmentally benign O2 as the terminal oxidant and inexpensive commercially available copper salts as catalysts. Furthermore, a detailed mechanistic study revealed that, in addition to the major esterification route, side products (e.g., olefins and acids), which are inevitably generated under oxidative and basic conditions, were also simultaneously converted into esters, thus significantly improving the final yields of target ester products. Native lignin represents the only naturally sustainable aromatic resource. Transformation of native lignin into valuable aromatics would make a great contribution to our planet. We report, for the first time, the effective transformation of alcohols into esters by esterification of C(OH)–C bonds, which offers a new way for the simultaneous degradation and functionalization of lignin. This reaction promotes new explorations for biomass valorization.
- Liu, Mingyang,Zhang, Zhanrong,Yan, Jiang,Liu, Shuaishuai,Liu, Huizhen,Liu, Zhaotie,Wang, Weitao,He, Zhenhong,Han, Buxing
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supporting information
p. 3288 - 3296
(2020/10/20)
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- Asymmetric Deoxygenative Cyanation of Benzyl Alcohols Enabled by Synergistic Photoredox and Copper Catalysis?
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Summary of main observation and conclusion. An enantioselective deoxygenative cyanation of benzyl alcohols was accomplished for the first time through the synergistic photoredox and copper catalysis. This reaction features the use of organic photosensitizer and low-cost 3d metal catalyst, simple and safe operations, and extremely mild conditions. A variety of chiral benzyl nitriles were produced in generally good yields and high level of enantiocontrols from readily available feedstocks (22 examples, up to 93% yield and 92% ee).
- Chen, Hong-Wei,Lu, Fu-Dong,Cheng, Ying,Jia, Yue,Lu, Liang-Qiu,Xiao, Wen-Jing
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supporting information
p. 1671 - 1675
(2020/11/03)
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- Lutidine-Based Chiral Pincer Manganese Catalysts for Enantioselective Hydrogenation of Ketones
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A series of MnI complexes containing lutidine-based chiral pincer ligands with modular and tunable structures has been developed. The complex shows unprecedentedly high activities (up to 9800 TON; TON=turnover number), broad substrate scope (81 examples), good functional-group tolerance, and excellent enantioselectivities (85–98 % ee) in the hydrogenation of various ketones. These aspects are rare in earth-abundant metal catalyzed hydrogenations. The utility of the protocol have been demonstrated in the asymmetric synthesis of a variety of key intermediates for chiral drugs. Preliminary mechanistic investigations indicate that an outer-sphere mode of substrate–catalyst interactions probably dominates the catalysis.
- Zhang, Linli,Tang, Yitian,Han, Zhaobin,Ding, Kuiling
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supporting information
p. 4973 - 4977
(2019/03/17)
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- Catalysts for the asymmetric transfer hydrogenation of various ketones from [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] and [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2
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The combination of [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] with [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2, in the presence of KOH/isoPrOH, has been found to generate catalysts that are capable of enantioselectively reducing alkyl, aryl ketones to the corresponding (R)-alcohols. Under optimized conditions, when the catalysts were applied to the asymmetric transfer hydrogenation, we obtained the secondary alcohol products in high conversions and enantioselectivities using only 0.5 mol% catalyst loading. In addition, [3-[(2S)-2-{[(chloro(?4-1,5-cyclooctadiene)rhodium)diphenyl phosphanyl] oxy}-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride], (6) complex is much more active than the other analogous complexes in the transfer hydrogenation. Catalyst 6 acts as excellent catalysts, giving the corresponding (R)-1-phenyl ethanol in 99% conversion in 30 min (TOF ≤ 396 h?1) and in high enantioselectivity (92% ee).
- Meri?, Nermin,Arslan, Nevin,Kayan, Cezmi,Rafikova, Khadichakhan,Zazybin, Alexey,Kerimkulova, Aygul,Aydemir, Murat
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p. 108 - 118
(2019/04/17)
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- Enantiopure Methyl- A nd Phenyllithium: Mixed (Carb-)Anionic Anisyl Fencholate-Aggregates
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Methyl- A nd phenyllithium aggregates with enantiopure anisyl fencholate units form after reaction of organolithium reagent with (+)-anisyl fenchol in hydrocarbon and some ethereal solvents. These carbanionic aggregates are characterized by X-ray crystal analyses and exhibit both 3:1 stoichiometry and distorted cubic Li4O3C1 cores, in which three lithium ions coordinate the carbanion (i.e., methylide or phenylide). These three lithium ions define a Lewis acidic surface (Li3), binding the carbanion and expanding with the steric demand of the carbanion (i.e., from Me: 2.62 ?2, over n-Bu: 2.65 ?2 (previous work) to Ph: 2.79 ?2). Methylation and phenylation reactions of various prochiral aldehydes employing these methyllithium and phenyllithium aggregates yield alcohols with up to 44% ee. To rationalize the formation of the mixed (carb-)anionic aggregates, aggregate formation energies, describing co-condensations of RLi (R = Me, Ph, n-Bu) and lithium fencholates, are computed for the 3:1 and 2:2 stoichiometries. These computed aggregate formation energies point to preferences for 3:1 over 2:2 aggregates, as it is also apparent from experimental aggregate formations, confirmed by X-ray crystal analyses. In close analogy to the X-ray crystal structures, the computed Li3 surfaces increase with increasing steric demand of the carbanions. The chiral, mixed (carb-)anionic RLi-fencholate aggregates hence adapt to different carbanion sized and arise not only with small (Me) or primary carbanions (n-Bu) but even with the larger secondary phenyl anion.
- Grote, Vanessa,Neud?rfl, J?rg-Martin,Goldfuss, Bernd
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supporting information
p. 771 - 779
(2019/02/19)
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- Chiral Frustrated Lewis Pairs Catalyzed Highly Enantioselective Hydrosilylations of Ketones
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A highly enantioselective Piers-type hydrosilylation of simple ketones was successfully realized using a chiral frustrated Lewis pair of tri-tert-butylphosphine and chiral diene-derived borane as catalyst. A wide range of optically active secondary alcohols were furnished in 80%—99% yields with 81%—97% ee's under mild reaction conditions.
- Liu, Xiaoqin,Wang, Qiaotian,Han, Caifang,Feng, Xiangqing,Du, Haifeng
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p. 663 - 666
(2019/05/21)
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- Asymmetric aerobic oxidation of secondary alcohols catalyzed by poly(: N-vinyl-2-pyrrolidone)-stabilized gold clusters modified with cyclodextrin derivatives
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Surface modification of poly(N-vinyl-2-pyrrolidone)-stabilized gold clusters (1.8 ± 0.6 nm) with aminated cyclodextrins induced aerobic oxidative kinetic resolution of racemic secondary alcohols (krel = 1.2).
- Hirano, Koto,Takano, Shinjiro,Tsukuda, Tatsuya
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supporting information
p. 15033 - 15036
(2020/01/03)
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- Enhanced activity and modified substrate-favoritism of Burkholderia cepacia lipase by the treatment with a pyridinium alkyl-PEG sulfate ionic liquid
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Three types of pyridinium salts, i.e., 1-ethylpyridin-1-ium cetyl-PEG10 sulfate (PYET), 1-butylpyridin-1-ium cetyl-PEG10 sulfate (PYBU), and 1-(3-methoxypropyl)pyridin-1-ium cetyl-PEG10 sulfate (PYMP), have been prepared and evaluated for their activation property of Burkholderia cepacia lipase by comparison to the control IL-coated enzymes, 1-butyl-2,3-dimethylimidazolium cetyl-PEG10 sulfate-coated lipase PS (IL1-PS). Among the tested pyridinium salt-coated lipases, the PYET-coated lipase PS (PYET-PS) exhibited the best results; the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, 1-(pyridin-4-yl)ethanol, or 4-phenylbut-3-en-2-ol proceeded faster than those of the IL1-PS-catalyzed reaction while maintaining an excellent enantioselectivity (E > 200). This improved efficiency was found to be dependent on the increased Kcat value.
- Kadotani, Shiho,Nokami, Toshiki,Itoh, Toshiyuki
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p. 441 - 447
(2019/01/04)
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- Chirality-Economy Catalysis: Asymmetric Transfer Hydrogenation of Ketones by Ru-Catalysts of Minimal Stereogenicity
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This manuscript describes the design and synthesis of Ru catalysts that feature only a single stereogenic element, yet this minimal chirality resource is demonstrated to be competent for effecting high levels of stereoinduction in the asymmetric transfer hydrogenation over a broad range of ketone substrates, including those that are not accommodated by known catalyst systems. The single stereogenic center of the (1-pyridine-2-yl)methanamine) is the only point-chirality in the catalysts, which simplifies this catalyst system relative to existing literature protocols.
- Chen, Fumin,He, Dongxu,Chen, Li,Chang, Xiaoyong,Wang, David Zhigang,Xu, Chen,Xing, Xiangyou
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p. 5562 - 5566
(2019/06/05)
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- Manganese complex and preparation method and application thereof
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The invention discloses a manganese complex taking (RC,SP)-N-5,6,7,8-tetrahydroquinoline-1-(2-diphenylphosphino)ferrocene ethyl amine as a ligand, a preparation method and application of the manganesecomplex in catalyst ketone compound asymmetric hydrogen transfer reduction preparing chiral alcohol. The manganese complex is a cheap metal chiral catalyst, the cost is low, the thermal stability isgood, and the preparation method of the manganese complex has the advantages of mild condition, short period, simple operation condition and the like. The catalyst is used for reducing the chiral alcohol for ketone hydrogen transfer, has higher catalytic activity, and a method for preparing the chiral alcohol is simple, less in environment pollution, and high in yield.
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Paragraph 0063-0066; 0069
(2020/01/03)
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- Copper(I)-Catalyzed Enantioconvergent Borylation of Racemic Benzyl Chlorides Enabled by Quadrant-by-Quadrant Structure Modification of Chiral Bisphosphine Ligands
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The first copper(I)-catalyzed enantioselective borylation of racemic benzyl chlorides has been realized by a quadrant-by-quadrant structure modulation of QuinoxP*-type bisphosphine ligands. This reaction converts racemic mixtures of secondary benzyl chlorides into the corresponding chiral benzylboronates with high enantioselectivity (up to 92 % ee). The results of mechanistic studies suggest the formation of a benzylic radical intermediate. The results of DFT calculations indicate that the optimal bisphosphine-copper(I) catalyst engages in noncovalent interactions that efficiently recognize the radical intermediate, and leads to high levels of enantioselectivity.
- Iwamoto, Hiroaki,Endo, Kohei,Ozawa, Yu,Watanabe, Yuta,Kubota, Koji,Imamoto, Tsuneo,Ito, Hajime
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supporting information
p. 11112 - 11117
(2019/07/17)
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- Chemical-enzyme method used for synthesis of cinacalcet
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The invention discloses a chemical-enzyme method used for synthesis of cinacalcet. The chemical-enzyme method cmprises following steps: under catalyst effect of lipase, racemic 1-(1-naphthyl)ethanol and a fatty acid vinyl ester are subjected to kinetic resolution in a solvent so as to obtain (S)-1-(1-naphthyl) ethanol; under the effect of a catalyst, (S)-1-(1-naphthyl) ethanol and 3-(3-(trifluoromethyl)phenyl)propylamine are subjected to Mitsunobu reaction so as to obtain cinacalcet. According to the chemical-enzyme method, racemic 1-(1-naphthyl)ethanol is taken as an initial raw material, biological enzyme resolution is adopted so as to obtain (S)-1-(1-naphthyl) ethanol, and (S)-1-(1-naphthyl) ethanol and 3-(3-(trifluoromethyl)phenyl)propylamine are subjected to Mitsunobu reaction so asto obtain cinacalcet. Compared with the prior art, the advantages are that: reaction steps are few; operation is simple; no high pressure container is used for hydrogenation reduction; no expensive reducing agent is used; reaction conditions are mild; safety is high; the yield and purity are high; and the purity is as high as 99% or higher.
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Paragraph 0065
(2019/01/22)
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- Iridium-catalyzed asymmetric hydrogenation method for the preparation of chiral alcohols
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The present invention provides one kind of iridium-catalyzed asymmetric hydrogenation method for the preparation of chiral alcohols, the method specifically is: in the glove box filled with nitrogen, the [Ir (COD) Cl]2 With a chiral P, N, N ligand soluble in methanol, stir at room temperature 1 hour, [...] catalyst. Adding substrate alkone and alkali additive, is placed on the high-pressure in the reactor, for a certain reaction under the pressure of the hydrogenation reaction. Slowly release hydrogen, silica gel to remove the solvent and separate the product after the alcohol. The invention states iridium catalyzed alkone asymmetric hydrogenation for the preparation of chiral reaction has mild condition, easy to operate, and the product of the enantioselectivity and the like.
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Paragraph 0095-0102; 0104
(2019/06/07)
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