- Experimental and Mechanistic Understanding of Aldehyde Hydrogenation Using Au25 Nanoclusters with Lewis Acids: Unique Sites for Catalytic Reactions
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The catalytic activity of Au25(SR)18 nanoclusters (R = C2H4Ph) for the aldehyde hydrogenation reaction in the presence of a base, e.g., ammonia or pyridine, and transition-metal ions Mz+, such as Cu+, Cu2+, Ni2+ and Co2+, as a Lewis acid is studied. The addition of a Lewis acid is found to significantly promote the catalytic activity of Au25(SR)18/CeO2 in the hydrogenation of benzaldehyde and a number of its derivatives. Matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry in conjunction with UV-vis spectroscopy confirm the generation of new species, Au25-n(SR)18-n (n = 1-4), in the presence of a Lewis acid. The pathways for the speciation of Au24(SR)17 from its parent Au25(SR)18 nanocluster as well as its structure are investigated via the density functional theory (DFT) method. The adsorption of Mz+ onto a thiolate ligand -SR- of Au25(SR)18, followed by a stepwise detachment of -SR- and a gold atom bonded to -SR- (thus an Au-SR unit) is found to be the most likely mechanism for the Au24(SR)17 generation. This in turn exposes the Au13-core of Au24(SR)17 to reactants, providing an active site for the catalytic hydrogenation. DFT calculations indicate that Mz+ is also capable of adsorbing onto the Au13-core surface, producing a possible active metal site of a different kind to catalyze the aldehyde hydrogenation reaction. This study suggests, for the first time, that species with an open metal site like adducts [nanoparticle-M](z-1)+ or fragments Au25-n(SR)18-n function as the catalysts rather than the intact Au25(SR)18.
- Li, Gao,Abroshan, Hadi,Chen, Yuxiang,Jin, Rongchao,Kim, Hyung J.
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- Hydrogenation of Esters by Manganese Catalysts
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The hydrogenation of esters catalyzed by a manganese complex of phosphine-aminopyridine ligand was developed. Using this protocol, a variety of (hetero)aromatic and aliphatic carboxylates including biomass-derived esters and lactones were hydrogenated to primary alcohols with 63–98% yields. The manganese catalyst was found to be active for the hydrogenation of methyl benzoate, providing benzyl alcohol with turnover numbers (TON) as high as 45,000. Investigation of catalyst intermediates indicated that the amido manganese complex was the active catalyst species for the reaction. (Figure presented.).
- Li, Fu,Li, Xiao-Gen,Xiao, Li-Jun,Xie, Jian-Hua,Xu, Yue,Zhou, Qi-Lin
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- New inha inhibitors based on expanded triclosan and di-triclosan analogues to develop a new treatment for tuberculosis
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The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) has reinforced the need for the development of new anti-TB drugs. The first line drug isoniazid inhibits InhA. This is a prodrug requiring activation by the enzyme KatG. Mutations in KatG have largely contributed to clinical isoniazid resistance. We aimed to design new ‘direct’ InhA inhibitors that obviate the need for activation by KatG, circumventing pre-existing resistance. In silico molecular modelling was used as part of a rational structure-based drug-design approach involving inspection of protein crystal structures of InhA:inhibitor complexes, including the broad spectrum antibiotic triclosan (TCS). One crystal structure exhibited the unusual presence of two triclosan molecules within the Mycobacterium tuberculosis InhA binding site. This became the basis of a strategy for the synthesis of novel inhibitors. A series of new, flexible ligands were designed and synthesised, expanding on the triclosan structure. Low Minimum Inhibitory Concentrations (MICs) were obtained for benzylphenyl compounds (12, 43 and 44) and di-triclosan derivative (39), against Mycobacterium bovis BCG although these may also be inhibiting other enzymes. The ether linked di-triclosan derivative (38) displayed excellent in vitro isolated enzyme inhibition results comparable with triclosan, but at a higher MIC (125 μg mL?1 ). These compounds offer good opportunities as leads for further optimisation.
- Chetty, Sarentha,Armstrong, Tom,Sharma Kharkwal, Shalu,Drewe, William C.,De Matteis, Cristina I.,Evangelopoulos, Dimitrios,Bhakta, Sanjib,Thomas, Neil R.
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- Hydroboration Reaction and Mechanism of Carboxylic Acids using NaNH2(BH3)2, a Hydroboration Reagent with Reducing Capability between NaBH4and LiAlH4
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Hydroboration reactions of carboxylic acids using sodium aminodiboranate (NaNH2[BH3]2, NaADBH) to form primary alcohols were systematically investigated, and the reduction mechanism was elucidated experimentally and computationally. The transfer of hydride ions from B atoms to C atoms, the key step in the mechanism, was theoretically illustrated and supported by experimental results. The intermediates of NH2B2H5, PhCH= CHCOOBH2NH2BH3-, PhCH= CHCH2OBO, and the byproducts of BH4-, NH2BH2, and NH2BH3- were identified and characterized by 11B and 1H NMR. The reducing capacity of NaADBH was found between that of NaBH4 and LiAlH4. We have thus found that NaADBH is a promising reducing agent for hydroboration because of its stability and easy handling. These reactions exhibit excellent yields and good selectivity, therefore providing alternative synthetic approaches for the conversion of carboxylic acids to primary alcohols with a wide range of functional group tolerance.
- Wang, Jin,Ju, Ming-Yue,Wang, Xinghua,Ma, Yan-Na,Wei, Donghui,Chen, Xuenian
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p. 5305 - 5316
(2021/04/12)
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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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- Mono- and Di-Mesoionic Carbene-Boranes: Synthesis, Structures and Utility as Reducing Agents
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Mesoionic carbenes (MIC) of the 1,2,3-triazol-5-ylidene type are currently popular ligands in organometallic chemistry. Their use in main group chemistry has been rather limited. In this contribution we present mono- and di-MIC-boranes with MICs based on triazolylidenes. The synthesis involves in-situ deprotonation of the corresponding triazolium salts and their reaction with boranes to form the desired compounds. Whereas this reaction route worked well for all triazolium salts derived from the 1,4-regioisomer of the triazoles, for the methlyene-bridged bi-triazolium salt derived from a 1,5-substiuted triazole, we observed the unexpected decomposition of the bi-triazolium and the formation of a triazole-borane with a new N?B bond. All compounds were characterized via multinuclear NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction. Furthermore, the MIC-boranes were used as reducing agents for the reduction of the C=O of aldehydes to the corresponding alcohols.
- Stein, Felix,Kirsch, Marius,Beerhues, Julia,Albold, Uta,Sarkar, Biprajit
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supporting information
p. 2417 - 2424
(2021/06/17)
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- Mild oxidation of benzyl alcohols to benzyl aldehydes or ketones catalyzed by visible light
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Induced by visible light, mild oxidation condition to prepare benzyl aldehydes or ketones have been developed by using bromotrichloromethane as photochemical oxidant. This method avoids high temperature, pressure and peroxidation with only visible light as the green driving force.
- Cheng, Dongping,Li, Xiaonian,Ren, Shujian,Xu, Xiaoliang
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supporting information
(2021/07/02)
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- Uranyl(VI) Triflate as Catalyst for the Meerwein-Ponndorf-Verley Reaction
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Catalytic transformation of oxygenated compounds is challenging in f-element chemistry due to the high oxophilicity of the f-block metals. We report here the first Meerwein-Ponndorf-Verley (MPV) reduction of carbonyl substrates with uranium-based catalysts, in particular from a series of uranyl(VI) compounds where [UO2(OTf)2] (1) displays the greatest efficiency (OTf = trifluoromethanesulfonate). [UO2(OTf)2] reduces a series of aromatic and aliphatic aldehydes and ketones into their corresponding alcohols with moderate to excellent yields, using iPrOH as a solvent and a reductant. The reaction proceeds under mild conditions (80 °C) with an optimized catalytic charge of 2.3 mol % and KOiPr as a cocatalyst. The reduction of aldehydes (1-10 h) is faster than that of ketones (>15 h). NMR investigations clearly evidence the formation of hemiacetal intermediates with aldehydes, while they are not formed with ketones.
- Kobylarski, Marie,Monsigny, Louis,Thuéry, Pierre,Berthet, Jean-Claude,Cantat, Thibault
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supporting information
p. 16140 - 16148
(2021/11/01)
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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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- Sodium Aminodiboranate, a New Reagent for Chemoselective Reduction of Aldehydes and Ketones to Alcohols
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Sodium aminodiboranate (NaNH 2(BH 3) 2, NaADBH) is a new member of the old borane family, which exhibits superior performance in chemoselective reduction. Experimental results show that NaADBH can rapidly reduce aldehydes and ketones to the corresponding alcohols in high efficiency and selectivity under mild conditions. There are little steric and electronic effects on this reduction.
- Wang, Jin,Guo, Yu,Li, Shouhu,Chen, Xuenian
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supporting information
p. 1104 - 1108
(2021/05/25)
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- Redox-active ligand based Mn(i)-catalyst for hydrosilylative ester reduction
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Herein a Mn(i) catalyst bearing a redox-active phenalenyl (PLY) based ligand is reported for the efficient hydrosilylation of esters to alcohols using the inexpensive silane source polymethylhydrosiloxane (PMHS) under mild conditions. Mechanistic investigations suggest a strong ligand-metal cooperation where a ligand-based single electron transfer (SET) process initiates the reaction through Si-H bond activation.
- Chakraborty, Soumi,Das, Arpan,Mandal, Swadhin K.
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supporting information
p. 12671 - 12674
(2021/12/04)
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- Reduction over Condensation of Carbonyl Compounds through a Transient Hemiaminal Intermediate Using Hydrazine
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Reduction of carbonyl moieties to the corresponding alcohol using simply hydrazine hydrate has been considerably unfeasible until now due to the well-known condensation reaction. However, herein, we report that using an excess of 20-fold equivalents, the reduction proceeds in excellent yields. 1H NMR study of the reaction and density functional theory (DFT) calculations indicate that the final fate of the hemiaminal intermediate is crucial to obtain the alcohol or the hydrazone.
- Vilches-Herrera, Marcelo,Gallardo-Fuentes, Sebastián,Aravena-Opitz, Mauricio,Yá?ez-Sánchez, Mauricio,Jiao, Haijun,Holz, Jens,B?rner, Armin,Lühr, Susan
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p. 9213 - 9218
(2020/08/14)
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- A Hammett Study of Clostridium acetobutylicum Alcohol Dehydrogenase (CaADH): An Enzyme with Remarkable Substrate Promiscuity and Utility for Organic Synthesis
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Described is a physical organic study of the reduction of three sets of carbonyl compounds by the NADPH-dependent enzyme Clostridium acetobutylicum alcohol dehydrogenase (CaADH). Previous studies in our group have shown this enzyme to display broad substrate promiscuity, yet remarkable stereochemical fidelity, in the reduction of carbonyl compounds, including α-, β- and γ-keto esters (d -stereochemistry), as well as α,α-difluorinated-β-keto phosphonate esters (l -stereochemistry). To better mechanistically characterize this promising dehydrogenase enzyme, we report here the results of a Hammett linear free-energy relationship (LFER) study across three distinct classes of carbonyl substrates; namely aryl aldehydes, aryl β-keto esters and aryl trifluoromethyl ketones. Rates are measured by monitoring the decrease in NADPH fluorescence at 460 nm with time across a range of substrate concentrations for each member of each carbonyl compound class. The resulting v 0 versus [S] data are subjected to least-squares hyperbolic fitting to the Michaelis-Menton equation. Hammett plots of log(V max) versus σ X yield the following Hammett parameters: (i) for p -substituted aldehydes, ρ = 0.99 ± 0.10, ρ = 0.40 ± 0.09; two domains observed, (ii) for p -substituted β-keto esters ρ = 1.02 ± 0.31, and (iii) for p -substituted aryl trifluoromethyl ketones ρ = -0.97 ± 0.12. The positive sign of ρ indicated for the first two compound classes suggests that the hydride transfer from the nicotinamide cofactor is at least partially rate-limiting, whereas the negative sign of ρ for the aryl trifluoromethyl ketone class suggests that dehydration of the ketone hydrate may be rate-limiting for this compound class. Consistent with this notion, examination of the 13 C NMR spectra for the set of p -substituted aryl trifluo romethyl ketones in 2percent aqueous DMSO reveals significant formation of the hydrate (gem -diol) for this compound family, with compounds bearing the more electron-withdrawing groups showing greater degrees of hydration. This work also presents the first examples of the CaADH-mediated reduction of aryl trifluoromethyl ketones, and chiral HPLC analysis indicates that the parent compound α,α,α-trifluoroacetophenone is enzymatically reduced in 99percent ee and 95percent yield, providing the (S)-stereoisomer, suggesting yet another compound class for which this enzyme displays high enantioselectivity.
- Berkowitz, David B.,Kudalkar, Gaurav P.,Lee, Joshua D.,Tiwari, Virendra K.
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supporting information
p. 237 - 247
(2020/02/18)
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- Chemoselective Oxidation of p-Methoxybenzyl Ethers by an Electronically Tuned Nitroxyl Radical Catalyst
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The oxidation of p-methoxy benzyl (PMB) ethers was achieved using nitroxyl radical catalyst 1, which contains electron-withdrawing ester groups adjacent to the nitroxyl group. The oxidative deprotection of the PMB moieties on the hydroxy groups was observed upon treatment of 1 with 1 equiv of the co-oxidant phenyl iodonium bis(trifluoroacetate) (PIFA). The corresponding carbonyl compounds were obtained by treating the PMB-protected alcohols with 1 and an excess of PIFA.
- Hamada, Shohei,Sugimoto, Koichi,Elboray, Elghareeb E.,Kawabata, Takeo,Furuta, Takumi
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supporting information
p. 5486 - 5490
(2020/07/24)
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- Cerium(IV) Carboxylate Photocatalyst for Catalytic Radical Formation from Carboxylic Acids: Decarboxylative Oxygenation of Aliphatic Carboxylic Acids and Lactonization of Aromatic Carboxylic Acids
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We found that in situ generated cerium(IV) carboxylate generated by mixing the precursor Ce(OtBu)4 with the corresponding carboxylic acids served as efficient photocatalysts for the direct formation of carboxyl radicals from carboxylic acids under blue light-emitting diodes (blue LEDs) irradiation and air, resulting in catalytic decarboxylative oxygenation of aliphatic carboxylic acids to give C-O bond-forming products such as aldehydes and ketones. Control experiments revealed that hexanuclear Ce(IV) carboxylate clusters initially formed in the reaction mixture and the ligand-to-metal charge transfer nature of the Ce(IV) carboxylate clusters was responsible for the high catalytic performance to transform the carboxylate ligands to the carboxyl radical. In addition, the Ce(IV) carboxylate cluster catalyzed direct lactonization of 2-isopropylbenzoic acid to produce the corresponding peroxy lactone and ?3-lactone via intramolecular 1,5-hydrogen atom transfer (1,5-HAT).
- Hirosawa, Keishi,Mashima, Kazushi,Satoh, Tetsuya,Shinohara, Koichi,Shirase, Satoru,Tamaki, Sota,Tsurugi, Hayato
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supporting information
(2020/03/25)
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- Manganese-catalysed transfer hydrogenation of esters
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Manganese catalysed ester reduction using ethanol as a hydrogen transfer agent in place of dihydrogen is reported. High yields can be achieved for a range of substrates using 1 mol% of a Mn(i) catalyst, with an alkoxide promoter. The catalyst is derived from a tridentate P,N,N ligand.
- Oates, Conor L.,Widegren, Magnus B.,Clarke, Matthew L.
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supporting information
p. 8635 - 8638
(2020/08/21)
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- Continuous-Flow Amide and Ester Reductions Using Neat Borane Dimethylsulfide Complex
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Reductions of amides and esters are of critical importance in synthetic chemistry, and there are numerous protocols for executing these transformations employing traditional batch conditions. Notably, strategies based on flow chemistry, especially for amide reductions, are much less explored. Herein, a simple process was developed in which neat borane dimethylsulfide complex (BH3?DMS) was used to reduce various esters and amides under continuous-flow conditions. Taking advantage of the solvent-free nature of the commercially available borane reagent, high substrate concentrations were realized, allowing outstanding productivity and a significant reduction in E-factors. In addition, with carefully optimized short residence times, the corresponding alcohols and amines were obtained in high selectivity and high yields. The synthetic utility of the inexpensive and easily implemented flow protocol was further corroborated by multigram-scale syntheses of pharmaceutically relevant products. Owing to its beneficial features, including low solvent and reducing agent consumption, high selectivity, simplicity, and inherent scalability, the present process demonstrates fewer environmental concerns than most typical batch reductions using metal hydrides as reducing agents.
- ?tv?s, Sándor B.,Kappe, C. Oliver
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p. 1800 - 1807
(2020/02/27)
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- A is by aromatic carboxylic acid non-catalytic reaction of alcohol compound (by machine translation)
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The present invention discloses a non-catalytic reaction of the aromatic carboxylic acid preparation of alcohol compound. In an inert gas atmosphere, after dehydration and deoxidation treatment of the reaction bottle [...] borane and carboxylic acid stirring and mixing, reaction 6 - 12 hours to obtain borate, further hydrolyzed into alcohol; said carboxylic acid is benzoic acid, 4 - bromobenzoic acid, 4 - fluoro benzoic acid, 1 - naphthoic acid, 2 - methoxybenzene formic acid and the like. The invention for the first time in the absence of catalyst under the conditions of high-efficiently using carboxylic acid with borane generating borohydrite reaction, carbonyl compound with borane generating borohydrite reaction preparation borate, further hydrolysis alcohol, provides new programme. (by machine translation)
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Paragraph 0025
(2019/04/17)
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- Storing redox equivalent in the phenalenyl backbone towards catalytic multi-electron reduction
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Storing and transferring electrons for multi-electron reduction processes are considered to be the key steps in various important chemical and biological transformations. In this work, we accomplished multi-electron reduction of a carboxylic acid via a hydrosilylation pathway where a redox-active phenalenyl backbone in Co(PLY-O,O)2(THF)2, stores electrons and plays a preponderant role in the entire process. This reduction proceeds by single electron transfer (SET) from the mono-reduced ligand backbone leading to the cleavage of the Si-H bond. Several important intermediates along the catalytic reduction reaction have been isolated and well characterized to prove that the redox equivalent is stored in the form of a C-H bond in the PLY backbone via a ligand dearomatization process. The ligand's extensive participation in storing a hydride equivalent has been conclusively elucidated via a deuterium labelling experiment. This is a rare example where the ligand orchestrates the multielectron reduction process leaving only the metal to maintain the conformational requirements and fine tunes the electronics of the catalyst.
- Bhunia, Mrinal,Sahoo, Sumeet Ranjan,Shaw, Bikash Kumar,Vaidya, Shefali,Pariyar, Anand,Vijaykumar, Gonela,Adhikari, Debashis,Mandal, Swadhin K.
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p. 7433 - 7441
(2019/08/15)
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- Method for preparing alcoholic compound from anilino lithium compound as catalyst
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The invention relates to an application of an anilino lithium compound, in particular to a method for preparing an alcoholic compound from the anilino lithium compound as a catalyst. The catalyst, borane and carboxylic acid are stirred and mixed uniformly, subjected to a reaction and exposed to air to terminate the reaction, a reacted liquid is subjected to reduced-pressure treatment for solvent removal, silica gel and methanol are added, and the alcoholic compound is obtained by hydrolysis. The anilino lithium compound can perform high-activity catalysis on the reaction between carboxylic acid and borane at room temperature, dose of the catalyst is only 0.8mol% of the mole ratio of carboxylic acid, compared with the conventional catalysis system, the commercial reagent anilino lithium compound is used, reaction conditions are mild, and yield of borate with different substituents under limit conditions can reach 90% or higher.
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- Based on n-butyl aromatic carboxylic acid preparation of alcohol compound
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The present invention relates to n-butyl application, in particular to based on n-butyl aromatic carboxylic acid preparation of alcohol compound, the catalyst sequentially, borane and carboxylic acid uniformly stirred and mixed, exposed to the air after the reaction terminated in the reaction, the reaction solution under reduced pressure to remove the solvent, then adding silica gel methanol hydrolyzed to obtain the alcohol compound. The invention discloses a butyl lithium can be high activity under the room temperature condition of catalytic carboxylic acid and borane borohydride reaction, the catalyst levels are only the molar amount of carboxylic acid 0.5 μM %, compared with the prior catalytic system, using the commercial reagent is BuLi, mild reaction conditions, in under a limited condition of different substituents of the yield of the ester can reach 90% or more.
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- Facile reduction of carboxylic acids to primary alcohols under catalyst-free and solvent-free conditions
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We report the development of a facile protocol for the deoxygenative hydroboration of aliphatic and aryl carboxylic acids to afford corresponding primary alcohols under solvent-free and catalyst-free conditions. The reaction proceeds under ambient temperature exhibits good tolerance towards various functional groups and generates quantitative yields. The plausible mechanism involves the formation of Lewis acid-base adducts as well as the liberation of hydrogen gas.
- Harinath, Adimulam,Bhattacharjee, Jayeeta,Panda, Tarun K.
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p. 1386 - 1389
(2019/02/05)
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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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- The reductive deaminative conversion of nitriles to alcohols using: Para -formaldehyde in aqueous solution
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We report herein, for the first time, the application of para-formaldehyde (pFA) to the reductive deamination of both aliphatic and aromatic nitriles in aqueous solution under transfer hydrogenation conditions. A broad range of primary alcohols have been synthesized selectively with very good to excellent yields under the optimized conditions. The study disclosed that the air-stable, inexpensive and commercially available catalyst [Ru(p-cymene)Cl2]2 acts as the catalyst precursor in this reaction, converting to other more active catalytic species in the presence of pFA, resulting in its degradation to CO2 and H2. Nitriles are also showed to play a dual role in this transformation, both as a substrate and as a ligand, where the dimeric catalyst structures convert to monomeric ones upon the coordination of nitrile molecules.
- Tavakoli, Ghazal,Prechtl, Martin H. G.
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p. 6092 - 6101
(2019/11/11)
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- Interconverting Lanthanum Hydride and Borohydride Catalysts for C=O Reduction and C?O Bond Cleavage
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The high catalytic reactivity of homoleptic tris(alkyl) lanthanum La{C(SiHMe2)3}3 is highlighted by C?O bond cleavage in the hydroboration of esters and epoxides at room temperature. The catalytic hydroboration tolerates functionality typically susceptible to insertion, reduction, or cleavage reactions. Turnover numbers (TON) up to 10 000 are observed for aliphatic esters. Lanthanum hydrides, generated by reactions with pinacolborane, are competent for reduction of ketones but are inert toward esters. Instead, catalytic reduction of esters requires activation of the lanthanum hydride by pinacolborane.
- Patnaik, Smita,Sadow, Aaron D.
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supporting information
p. 2505 - 2509
(2019/02/01)
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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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- Synthesis and aggregation properties of boron-dipyrromethene dyes conjugated with guanine units
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Two boron-dipyrromethene dyes bearing a conjugated guanine unit (G-BODIPYs) 1 and 2 were synthesized and fully characterized. The self-assembly properties of these dyes were investigated by X-ray crystallography, 1H NMR and UV-vis spectroscopy. As revealed by X-ray crystal structure studies, G-BODIPY 1 self-assembled into ribbon-like structures due to the intermolecular hydrogen bonding and π-π stacking interaction. Concentration-dependent 1H NMR experiments confirmed the formation of hydrogen bonds of the guanine units in solution for both dye 1 and 2. In the presence of K+, the characteristic signals for the formation of cyclic G-quadruplex structures were observed in the 1H NMR study. Aggregation of G-BODIPY dyes was further monitored by UV-vis absorption spectroscopy by varying the solvent polarity and temperature. H-type aggregates of dye 1, which was characterized by a new hypsochromically shifted absorption band with λmax = 461 nm, was obtained. In the presence of K+, the enhancement of stability was observed for the H-aggregates of dye 1.
- Li, Fen,Zhang, Yongjie,Zhou, Lina,Zhang, Xin,Chen, Zhijian
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p. 944 - 952
(2018/07/21)
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- SNS-Ligands for Ru-Catalyzed Homogeneous Hydrogenation and Dehydrogenation Reactions
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A detailed study of literature-known and novel S-containing pincer-type ligands for ruthenium-catalyzed homogeneous hydrogenation and dehydrogenation reactions was carried out. The scope and limitations of these catalysts were carefully investigated, and it was shown that simple bench-stable SNS-Ru complexes can be used to facilitate the hydrogenation of a variety of different substrates at a maximum H2 pressure of 20 bar under operationally simple, easy to scale up, glovebox-free conditions by using starting materials and reagents that do not require any special purification prior to use. It was also shown that such complexes can be used to catalyze the dehydrogenative coupling of alcohols and amines to get amides as well as for the dehydrogenative dimerization of alcohols to esters.
- Sch?rgenhumer, Johannes,Zimmermann, Axel,Waser, Mario
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supporting information
p. 862 - 870
(2018/06/18)
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- Visible light-induced heterogeneous Meerwein-Ponndorf-Verley-type reduction of an aldehyde group over an organically modified titanium dioxide photocatalyst
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An organically modified titanium dioxide photocatalyst prepared by a simple impregnation method chemoselectively and almost quantitatively converted benzaldehydes having other reducible functional groups to the corresponding benzyl alcohols under visible
- Fukui, Makoto,Tanaka, Atsuhiro,Hashimoto, Keiji,Kominami, Hiroshi
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supporting information
p. 4215 - 4218
(2017/04/21)
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- Mechanistic Investigation of Bis(imino)pyridine Manganese Catalyzed Carbonyl and Carboxylate Hydrosilylation
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We recently reported a bis(imino)pyridine (or pyridine diimine, PDI) manganese precatalyst, (Ph2PPrPDI)Mn (1), that is active for the hydrosilylation of ketones and dihydrosilylation of esters. In this contribution, we reveal an expanded scope for 1-mediated hydrosilylation and propose two different mechanisms through which catalysis is achieved. Aldehyde hydrosilylation turnover frequencies (TOFs) of up to 4900 min-1 have been realized, the highest reported for first row metal-catalyzed carbonyl hydrosilylation. Additionally, 1 has been shown to mediate formate dihydrosilylation with leading TOFs of up to 330 min-1. Under stoichiometric and catalytic conditions, addition of PhSiH3 to (Ph2PPrPDI)Mn was found to result in partial conversion to a new diamagnetic hydride compound. Independent preparation of (Ph2PPrPDI)MnH (2) was achieved upon adding NaEt3BH to (Ph2PPrPDI)MnCl2 and single-crystal X-ray diffraction analysis revealed this complex to possess a capped trigonal bipyramidal solid-state geometry. When 2,2,2-trifluoroacetophenone was added to 1, radical transfer yielded (Ph2PPrPDI·)Mn(OC·(Ph)(CF3)) (3), which undergoes intermolecular C-C bond formation to produce the respective Mn(II) dimer, [(μ-O,Npy-4-OC(CF3)(Ph)-4-H-Ph2PPrPDI)Mn]2 (4). Upon finding 3 to be inefficient and 4 to be inactive, kinetic trials were conducted to elucidate the mechanisms of 1- and 2-mediated hydrosilylation. Varying the concentration of 1, substrate, and PhSiH3 revealed a first order dependence on each reagent. Furthermore, a kinetic isotope effect (KIE) of 2.2 ± 0.1 was observed for 1-catalyzed hydrosilylation of diisopropyl ketone, while a KIE of 4.2 ± 0.6 was determined using 2, suggesting 1 and 2 operate through different mechanisms. Although kinetic trials reveal 1 to be the more active precatalyst for carbonyl hydrosilylation, a concurrent 2-mediated pathway is more efficient for carboxylate hydrosilylation. Considering these observations, 1-catalyzed hydrosilylation is believed to proceed through a modified Ojima mechanism, while 2-mediated hydrosilylation occurs via insertion.
- Mukhopadhyay, Tufan K.,Rock, Christopher L.,Hong, Mannkyu,Ashley, Daniel C.,Groy, Thomas L.,Baik, Mu-Hyun,Trovitch, Ryan J.
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p. 4901 - 4915
(2017/04/11)
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- Hydroxyl Radicals via Collision-Induced Dissociation of Trimethylammonium Benzyl Alcohols
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The hydroxyl radical is a well known reactive oxygen species important for interstellar, atmospheric, and combustion chemistry in addition to multiple biochemical processes. Although there are many methods to generate the hydroxyl radical, most of these are inorganic based, with only a few originating from organic precursor molecules. Reported herein is the observation that trimethylammonium benzyl alcohols and their corresponding deuterated isotopologues act as a good source of hydroxyl and deuteroxyl radicals in the gas-phase under collision-induced dissociation (CID) conditions. Attempts to replicate this chemistry in the condensed phase are described.
- Moore, Peter W.,Hooker, Jordan P.,Zavras, Athanasios,Khairallah, George N.,Krenske, Elizabeth H.,Bernhardt, Paul V.,Quach, Gina,Moore, Evan G.,O'Hair, Richard A. J.,Williams, Craig M.
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p. 397 - 406
(2017/04/07)
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- Organoborane-Catalyzed Hydrogenation of Unactivated Aldehydes with a Hantzsch Ester as a Synthetic NAD(P)H Analogue
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We have developed a method for the hydrogenation of unactivated aldehydes, using a Hantzsch ester as a NAD(P)H analogue in the presence of an electron-deficient triarylborane as a Lewis acid catalyst. Thus, tris[3,5-bis(trifluoromethyl)phenyl]borane efficiently catalyzes the hydrogenation of aliphatic aldehydes with a Hantzsch ester in 1,4-dioxane at 100 °C to give the corresponding aliphatic primary alcohols in up to 97% yield. Aromatic aldehydes also undergo the hydrogenation, even at 25 °C, to furnish the corresponding aromatic primary alcohols in up to 100% yield.
- Hamasaka, Go,Tsuji, Hiroaki,Uozumi, Yasuhiro
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supporting information
p. 2037 - 2041
(2015/09/01)
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- General transfer hydrogenation by activating ammonia-borane over cobalt nanoparticles
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Cobalt nanoparticles containing both Co2+ and Co0 species supported on carbon nitride can function as heterogeneous nanocatalysts for a general transfer hydrogenation reaction in aqueous ammonia-borane solution at room temperature. The conversions of nitroarenes, olefins, imines, aldehydes, ketones and cyanobenzene are high with superior selectivity under mild conditions. This noble-metal-free catalyst is also cheap and reusable.
- Zhao, Tian-Jian,Zhang, Ya-Nan,Wang, Kai-Xue,Su, Juan,Wei, Xiao,Li, Xin-Hao
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p. 102736 - 102740
(2015/12/11)
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- Photo-induced Metal-Catalyst-Free Aromatic Finkelstein Reaction
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The facile iodination of aromatic compounds under mild conditions is a great challenge for both organic and medicinal chemistry. Particularly, the synthesis of functionalized aryl iodides by light has long been considered impossible due to their photo-lability, which actually makes aryl iodides popular starting materials in many photo-substitution reactions. Herein, a photo-induced halogen exchange in aryl or vinyl halides has been discovered for the first time. A broad scope of aryl iodides can be prepared in high yields at room temperature under exceptionally mild conditions without any metal or photo-redox catalysts. The presence of a catalytic amount of elemental iodine could promote the reaction significantly.
- Li, Lu,Liu, Wenbo,Zeng, Huiying,Mu, Xiaoyue,Cosa, Gonzalo,Mi, Zetian,Li, Chao-Jun
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supporting information
p. 8328 - 8331
(2015/07/15)
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- A General, Practical Triethylborane-Catalyzed Reduction of Carbonyl Functions to Alcohols
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A combination of the abundant and low-cost triethylborane and sodium alkoxide generates a highly efficient catalyst for reduction of esters, as well as ketones and aldehydes, to alcohols using an inexpensive hydrosilane under mild conditions. The catalyst system exhibits excellent chemoselectivity and a high level of functional group tolerance. Mechanistic studies revealed a resting state of sodium triethylalkoxylborate that is the product of the reaction of BEt3 with sodium alkoxide. This borate species reacts with hydrosilane to form NaBEt3H, which rapidly reduces esters.
- Peng, Dongjie,Zhang, Mintao,Huang, Zheng
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supporting information
p. 14737 - 14741
(2015/10/19)
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- A strain induced change of mechanism from a [2 + 2 + 2] to a [2 + 1 + 2 + 1] cycloaddition reaction
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While investigating the [2 + 2 + 2] cycloaddition as a tool to build up strained oligophenyl systems with a diyne-ethylene glycol macrocyle, a surprising change of mechanism was observed. Instead of the expected [2 + 2 + 2] para-terphenyl, the ortho-terphenyl product explained by a formal [2 + 1 + 2 + 1] cycloaddition was formed. An η4-coordinated metal-cyclobutadiene is proposed as the key structure in the catalytic cycle, which is formed to release the induced strain. The optical properties of the ortho-terphenyl products have been measured as well as the coordination ability of Na+ and K+.
- Tran-Van, Anne-Florence,Goetz, Silas,Neuburger, Markus,Wegner, Hermann A.
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supporting information
p. 2410 - 2413
(2014/05/20)
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- Support-free palladium-NHC catalyst for highly recyclable heterogeneous suzuki-miyaura coupling in neat water
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Among the various new challenges of chemical processes in water, research on stable, highly active, and recyclable catalysts is a prosperous field. We present here a palladium-NHC catalyst that was synthesized with good yields through a series of simple synthetic steps. This organometallic species was used as a heterogeneous catalyst in low loadings for Suzuki-Miyaura coupling in neat water, under mild conditions. Reaction conditions were optimized for a simple, green, and support-free procedure, without using any phase transfer agent. The catalyst shows excellent reactivity in short times toward different substrates and a very good recyclability.
- Charbonneau, Mathieu,Addoumieh, George,Oguadinma, Paul,Schmitzer, Andreea R.
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supporting information
p. 6544 - 6549
(2015/02/19)
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- Benzimidazolium-based synthetic chloride and calcium transporters in bacterial membranes
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Herein, we present the first example of a benzimidazolium-based artificial transmembrane chloride transporter and a synthetic calcium ionophore that can regulate intracellular calcium concentrations in bacteria.
- Elie, Claude-Rosny,Hébert, Audrey,Charbonneau, Mathieu,Haiun, Adam,Schmitzer, Andreea R.
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supporting information
p. 923 - 928
(2013/03/13)
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- Hydrogenation of quinaldine and benzylic aldehydes both separately and combined in a tandem hydrogenation-reductive alkylation of quinaldine by aldehydes with iridium benzoquinoline catalysts
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A series of cyclometalated benzoquinoline complexes of Ir(III) catalyze the hydrogenation of the heterocyclic ring of quinolines under mild conditions. Our best catalyst is active in a significantly wider range of solvents than our previous systems. In the presence of a suitable base, the Ir(III) species is also able to hydrogenate the C=O bonds of aldehydes. When quinolines and aldehydes are present together, the Ir(III) complex catalyzes a tandem reaction in which the quinoline is first hydrogenated to a tetrahydroquinoline that is subsequently reductively alkylated by the aldehyde. The reductive alkylation competes with the hydrogenation of the aldehyde to the alcohol, and therefore good yields of the alkylated tetrahydroquinoline require the presence of excess aldehyde.
- Manas, Michael G.,Graeupner, Jonathan,Allen, Laura J.,Dobereiner, Graham E.,Rippy, Kerry C.,Hazari, Nilay,Crabtree, Robert H.
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p. 4501 - 4506
(2013/09/23)
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- Sterically controlled iodination of arenes via iridium-catalyzed C-H borylation
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A mild method to prepare aryl and heteroaryl iodides by sequential C-H borylation and iodination is reported. The regioselectivity of this process is controlled by steric effects on the C-H borylation step and is complementary to existing methods to form aryl iodides. The iodination of boronic esters has potential for the synthesis of radiolabeled aryl iodides, as demonstrated by the concise synthesis of a potential tracer for SPECT imaging.
- Partridge, Benjamin M.,Hartwig, John F.
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supporting information
p. 140 - 143
(2013/03/28)
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- Synthesis and biological evaluation of optically active Ki16425
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An enantionselective synthesis of both enantiomers of Ki16425, which possesses selective LPA antagonistic activity, was achieved. The isoxazole core was constructed by a 1,3-dipolar cycloaddition of nitrile oxide with alkyne and condensation with the optically active α-phenethyl alcohol segment, which was prepared by an enantioselective reduction of arylmethylketone. Biological evaluation of both enantiomers of Ki16425 revealed that the (R)-isomer showed much higher antagonistic activity for LPA1 and LPA3 receptors.
- Sato, Takanao,Sugimoto, Kenji,Inoue, Asuka,Okudaira, Shinichi,Aoki, Junken,Tokuyama, Hidetoshi
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supporting information; experimental part
p. 4323 - 4326
(2012/09/22)
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- Reductive cleavage of amides to alcohols and amines catalyzed by well-defined bimetallic molybdenum complexes
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Triple bonds do it! The molybdenum-catalyzed Ci-N bond cleavage of organic amides with hydrosilanes to produce alcohols and amines has been investigated. This work complements previously established protocols that lead to the cleavage of the Ci-O bond. Modified triply bonded dimolybdenum(III) alkoxides have been found to be crucial for tuning the selectivity to Ci-N bond cleavage (see figure). Copyright
- Krackl, Sebastian,Someya, Chika I.,Enthaler, Stephan
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supporting information
p. 15267 - 15271
(2013/01/15)
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- Iron-catalyzed hydrosilylation of esters
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The first hydrosilylation of esters catalyzed by a well defined iron complex has been developed. Esters are converted to the corresponding alcohols at 100 °C, under solvent-free conditions and visible light activation. Copyright
- Bezier, David,Venkanna, Gopaladasu T.,Castro, Luis C. Misal,Zheng, Jianxia,Roisnel, Thierry,Sortais, Jean-Baptiste,Darcel, Christophe
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supporting information; experimental part
p. 1879 - 1884
(2012/09/22)
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- Uncovering new properties of imidazolium salts: Cl- transport and supramolecular regulation of their transmembrane activity
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We report the Cl- transport activity for three imidazolium-based transporters. We present significant findings regarding the use of α-cyclodextrin and cucurbit[7]uril macrocycles to form inclusion complexes with these salts and to inhibit their
- Elie, Claude-Rosny,Noujeim, Nadim,Pardin, Christophe,Schmitzer, Andreea R.
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supporting information; experimental part
p. 1788 - 1790
(2011/03/22)
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- General copper-catalyzed transformations of functional groups from arylboronic acids in water
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A simple and general copper-catalyzed method has been developed for transformations of various functional groups (i I, i N3, i SO2R, i OH, i NH2, and i NO 2) on aromatic rings from arylboronic acids in water under air. The protocol uses cheap and readily available inorganic salts (KI, NaN3, NaSO2R, NaOH, NaNO2) and aqueous ammonia as the functional-group sources, simple Cu2O/NH3 as the catalyst system, environmentally friendly water as the solvent, and oxygen in air as the oxidant. Importantly, the copper catalyst system in water was recyclable. This study should provide a useful strategy for interconversions of the functional groups on aromatic rings.
- Yang, Haijun,Li, Yong,Jiang, Min,Wang, Junmei,Fu, Hua
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experimental part
p. 5652 - 5660
(2011/06/23)
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- Nickel-catalyzed reductive cross-coupling of aryl halides with alkyl halides
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(Chemical Equation Presented) The direct reductive cross-coupling of alkyl halides with aryl halides is described. The transformation is efficient (equimolar amounts of the starting materials are used), generally high-yielding (all but one between 55 and 88% yield), highly functional-group-tolerant [OH, NHBoc, NHCbz, Bpin, C(O)Me, CO2Et, and CN are all tolerated], and easy to perform (uses only benchtop-stable reagents, tolerates small amounts of water and oxygen, changes color when complete, and uses filtration workup). The reaction appears to avoid the formation of intermediate organomanganese species, and a synergistic effect was found when a mixture of two ligands was employed.
- Everson, Daniel A.,Shrestha, Ruja,Weix, Daniel J.
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supporting information; experimental part
p. 920 - 921
(2010/03/31)
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- Highly efficient system for reduction of carboxylic acids and their derivatives to alcohols by HfCl4/KBH4
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HfCl4/KBH4 was found to be a facile, efficient, convenient, and chemoselective system for the reduction of carboxylic acids and their derivatives to the corresponding alcohols under mild conditions. HfCl4/NaBH4 was also utilized to reduce the same carboxylic acids and their derivatives, and it was found that the reducing ability of HfCl4/NaBH4 was similar to that of HfCl4/KBH4. The action of HfCl4/KBH4 on other types of substrates, such as benzyl chloride, peracid, epoxide, ketone, amide, imine, pyridine-N-oxide, and nitrile, was investigated, too. In addition, some competitive reductions of styrene oxide in the presence of carboxylic acid, carboxylic ester, nitrile, and amide were achieved. Copyright Taylor & Francis Group, LLC.
- Zhang, Jianghua,Gao, Xinqin,Zhang, Chengyi,Ma, Jianfei,Zhao, Defeng
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experimental part
p. 1640 - 1654
(2009/10/17)
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- Preparation of donor-acceptor substituted fluorostilbenes and crystal chemistry of fluorinated (E)-4-(4-halogeno-styryl)-benzonitriles
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The syntheses and crystal structures of a series of fluoro-substituted halogeno (Cl, Br, I)-cyano-stilbenes containing donor and acceptor groups (D-π-A) are reported. These molecules show a tendency to form antiparallel chain-like structures and herringbone packing, crystallising predominantly in a centric space group. However, second harmonic generation measurements bear evidence for orientational disorder leading to partial polar order below the ordinary X-ray structure determination limit. Some co-crystals are isostructural with their components. The non-fluoro as well as the halogeno-fluoro substituted components of co-crystals seem to impose their crystal structure on the complementary fluoro- or cyano-fluoro substituted components. Co-crystallization enhanced the deviation from centrosymmetry.
- Mariaca, Raúl,Labat, Ga?l,Behrnd, Norwid-Rasmus,Bonin, Michel,Helbling, Fabien,Eggli, Patrick,Couderc, Ga?tan,Neels, Antonia,Stoeckli-Evans, Helen,Hulliger, Jürg
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scheme or table
p. 175 - 196
(2009/07/25)
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- Synthesis of organometallic poly(dendrimer)s by macromonomer polymerization: effect of dendrimer size and structural rigidity on the polymerization efficiency
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Two series of first to third generation (G1-G3) oligoether dendrimers, one hearing a shorter spacer chain (C-O) and the other having a longer spacer branch (C-C-C-O) were prepared. Both series of compounds, containing two reactive C≡CH moieties on the dendrimer surface, were used as macromonomers and copolymerized with trans-[Pt(PEt3)2Cl2] to form organometallic poly(dendrimer)s by an outer-sphere-outer-sphere connection strategy. It was found that concentration of monomer used in the polymerization, the dendrimer generation, and, most strikingly, the length of the spacer were key factors that determined the polymerization efficiency. Hence, the structurally more rigid and compact C-O linked dendrimers formed poly(dendrimer)s with a higher degree of polymerization than the structurally less rigid and more bulky C-C-C-O dendrimers. This result was due to the higher tendency to form cyclic oligomers in the latter series of compounds. In addition, the differences in the polymerization efficiency among the three generations of dendrimers could be explained by the gradual decrease of reactive functional group density on the dendrimer surface.
- Cheung, Siu-Yin,Chow, Hak-Fun,Ngai, To,Wei, Xiaoling
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supporting information; experimental part
p. 2278 - 2288
(2009/10/23)
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- ANTIBACTERIAL AGENTS
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Antibacterial compounds of formula (I) are provided, as well as stereoisomers, pharmaceutically acceptable salts, esters, and prodrugs thereof; pharmaceutical compositions comprising such compounds; methods of treating bacterial infections by the administration of such compounds; and processes for the preparation of such compounds.
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Page/Page column 126
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