- A new homogeneous polymer support based on syndiotactic polystyrene and its application in palladium-catalyzed Suzuki-Miyaura cross-coupling reactions
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Soluble syndiotactic polystyrene-supported triphenylphosphine (sPS-TPP) was synthesized by reacting borylated syndiotactic polystyrene with (4-bromophenyl)diphenylphosphine. A palladium catalyst, supported on sPS-TPP, effectively catalyzed Suzuki-Miyaura coupling reactions of aryl halides under homogeneous conditions. The polymer-supported palladium complex was recovered quantitatively by adding an equal volume of poor solvent to the polymer, and coupling products could be easily isolated by evaporating the solvents. The recovered polymer complex was reused several times without significant loss of activity. The Royal Society of Chemistry 2009.
- Shin, Jihoon,Bertoia, Julie,Czerwinski, Kenneth R.,Bae, Chulsung
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- Facile Suzuki-Miyaura cross coupling using ferrocene tethered N-heterocyclic carbene-Pd complex anchored on cellulose
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A novel ferrocene tethered N-heterocyclic carbene-Pd complex anchored on cellulose has been prepared by multi-step synthesis. The complex proved to be robust and efficient heterogeneous catalyst for synthesis of biaryls in Suzuki-Miyaura cross coupling reaction.
- Kale, Dolly,Rashinkar, Gajanan,Kumbhar, Arjun,Salunkhe, Rajashri
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- Improved aqueous Cannizzaro reaction in presence of cyclodextrin
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An aqueous hydroxypropyl-β-cyclodextrin solution has been used to increase the conversion of 4-biphenylcarboxaldehyde into the corresponding alcoholic and carboxylic substrates, by means of a Cannizzaro reaction. The observed enhancement has been ascribed to a partial solubilization of 4-biphenylcarboxaldehyde. In addition, as the main part of the organic substrates still remains insoluble, synthesized products are easily recovered by filtration. As a consequence, the basic cyclodextrin solution might also be reused for a new synthetic cycle, without significant loss of conversion. Aqueous solid-liquid biphasic reaction in presence of cyclodextrins thus seems to be a promising tool in the green chemistry field.
- Canipelle,Landy,Fourmentin
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- Development of p-phenylbenzyl as a new protecting group: Protection and deprotection of alcohols
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p-Phenylbenzyl is developed as a new 'PMB' like protecting group. p-Phenylbenzyl (PPB) ethers were prepared from alcohols with PPBBr-NaH or p-phenylbenzyl trichloroacetimidate-TfOH and subjected to oxidative deprotection using DDQ or DDQ (10 mol%)-3 equiv. Mn(OAc)3.
- Sharma,Rakesh
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- Target alcohol/phenol release by cyclative cleavage using glycine as a safety catch linker.
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The utility of glycine as a safety catch linker for the immobilization of alcohols and phenols to the solid-support is demonstrated by performing a variety of synthetic transformations.
- Raghavan, Sadagopan,Rajender
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- Heterobimetallic Carbene Complexes Bearing Cyclometalated IrIII/RhIII and Mixed NHC∧ Py/PPh3 Coordinated PdII Centers: Structures and Tandem Catalysis
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Heterobimetallic complexes bearing NHC donor ligands are gaining immense popularity in organometallic chemistry and tandem catalysis. It is known that the NHC reacts with PdII in the presence of pyridine to yield PEPPSI type complexes and the NHC ligands having ortho-C?H proton easily orthometalate to IrIII or RhIII centers. Combining these two methodologies in a stepwise fashion, we present here a series of heterobimetallic IrIII?PdII and RhIII?PdII complexes from a dicarbene donor ligand featuring cyclometalated IrIII or RhIII and mixed (Formula presented.) /PPh3 coordinated PdII centers. All the heterobimetallic complexes have been structurally characterized by X-ray crystallographic analysis. The heterobimetallic complexes featuring mixed (Formula presented.) coordinated PdII centers show better activity in tandem Suzuki-Miyaura/transfer hydrogenation reactions compared to both, the heterobimetallic complexes possessing PEPPSI type PdIIcenters, and the equimolar mixture of their mononuclear PdII and RhIII or IrIII counterparts. The heterobimetallic complex featuring cyclometalated IrIII and mixed (Formula presented.) coordinated PdII center shows excellent selectivity for 4-biphenylmethanol (isolated yield: 92 %) in tandem catalysis.
- Majumder, Adhir,Nath Saha, Tarak,Majumder, Niladri,Naskar, Rajat,Pal, Kuntal,Maity, Ramananda
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- Assessment of the reusability of Pd complexes supported on fluorous silica gel as catalysts for Suzuki couplings
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A thorough investigation of different perfluoro-tagged Pd complexes supported on fluorous silica gel (FSG) as catalysts for Suzuki reactions is presented. The rates of reaction upon recycling of the supported complexes were measured in order to determine the reusability of the catalysts. Perfluoro-tagged and untagged complexes adsorbed on FSG and unmodified silica gel were also compared. While with dimethoxyethane (DME) as a solvent the catalytic activity decreased upon reuse, significant activity was retained with recycled catalysts for reactions in water. With catalyst loadings of 0.001 mol-%, TONs as high as 526000 were obtained. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Tzschucke, Carl Christoph,Andrushko, Vasyl,Bannwarth, Willi
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- Isolation of a metastable geometrical isomer of a hexacoordinated dihydrophosphate: Elucidation of its enhanced reactivity in umpolung of a hydrogen atom of water
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Two of five conceivable geometrical isomers of a hexacoordinated dihydrophosphate bearing two sets of a bidentate ligand were investigated. X-ray crystallographic analysis of both of isomers, 1a-TPP and 1b-TEA, revealed their octahedral geometries of C2 and C1 symmetry, respectively, which were consistent with the NMR spectra. The isomer 1b-TEA underwent both hydride reduction of an aldehyde and proton exchange with water at room temperature in DMSO without any additive. A one-pot reaction of both of the reactions of 1b-TEA with D2O and an aldehyde or a ketone under the above conditions proceeded successfully to give the deuterated alcohol. Thus, umpolung of a hydrogen atom of water with 1b-TEA was achieved under much milder conditions than those used in the reaction with another isomer, 1a-TEA. Quantitative isomerization of 1b-TEA to 1a-TEA occurred in methanol at room temperature. Calculations on the five conceivable geometrical isomers of the anionic part of the dihydrophosphate revealed their relative stability, which reasonably explained the isomerization, and the larger negative charge at the atoms located at the trans positions of the oxygen atoms. The smaller coupling constants of the P-H and P-C bonds located at the rear of an oxygen atom in the NMR spectra resulted in the smaller s character of these bonds. The differences in both hydride-donation and proton-exchange reactivities between 1a-TEA and 1b-TEA could be explained by the differences in the atomic charge of the hydrogen atom and the stability difference of the initially formed phosphorane intermediates, respectively.
- Miyake, Hideaki,Kano, Naokazu,Kawashima, Takayuki
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- Novel Transformations of Zaragozic Acid A Derivatives with Cesium Fluoride
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C4-Hydroxy protected zaragozic acid A derivatives, upon treatment with CsF in DMF, underwent novel transformations to give tricyclic compounds. The process was initiated by intramolecular C3 proton abstraction by the C7 alkoxide anion to form the enolate ion, which can cyclie by two different pathways.
- Girotra, Narindar N.,Ponpipom, Mitree M.
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- Four-Coordinated Manganese(II) Disilyl Complexes for the Hydrosilylation of Aldehydes and Ketones with 1,1,3,3-Tetramethyldisiloxane
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The coordinatively unsaturated manganase(II) bis(supersilyl) complex Mn[Si(SiMe3)3]2(THF)2 (2) was synthesized in one step via the reaction of MnBr2 with two equivalents of KSi(SiMe3)3 in THF. Complex 2 acts as an effective precatalyst for the catalytic hydrosilylation of aldehydes and ketones with 1,1,3,3-tetramethyldisiloxane (TMDS). The catalytic efficiency can be improved by combining 2 and adamantyl isocyanide (CNAd). The stoichiometric reaction of 2 and two equivalents of CNAd led to the isolation of Mn[Si(SiMe3)3]2(CNAd)2 (3) in high yield. Complex 3 shows superior catalytic performance than 2 in the hydrosilylation of relatively unreactive ketones.
- Saito, Kyoka,Ito, Tatsuyoshi,Arata, Shogo,Sunada, Yusuke
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p. 1152 - 1156
(2020/12/18)
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- Visible Light Induced Reduction and Pinacol Coupling of Aldehydes and Ketones Catalyzed by Core/Shell Quantum Dots
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We present an efficient and versatile visible light-driven methodology to transform aryl aldehydes and ketones chemoselectively either to alcohols or to pinacol products with CdSe/CdS core/shell quantum dots as photocatalysts. Thiophenols were used as proton and hydrogen atom donors and as hole traps for the excited quantum dots (QDs) in these reactions. The two products can be switched from one to the other simply by changing the amount of thiophenol in the reaction system. The core/shell QD catalysts are highly efficient with a turn over number (TON) larger than 4 × 104 and 4 × 105 for the reduction to alcohol and pinacol formation, respectively, and are very stable so that they can be recycled for at least 10 times in the reactions without significant loss of catalytic activity. The additional advantages of this method include good functional group tolerance, mild reaction conditions, the allowance of selectively reducing aldehydes in the presence of ketones, and easiness for large scale reactions. Reaction mechanisms were studied by quenching experiments and a radical capture experiment, and the reasons for the switchover of the reaction pathways upon the change of reaction conditions are provided.
- Xi, Zi-Wei,Yang, Lei,Wang, Dan-Yan,Feng, Chuan-Wei,Qin, Yufeng,Shen, Yong-Miao,Pu, Chaodan,Peng, Xiaogang
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p. 2474 - 2488
(2021/02/05)
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- Base promotedgem-difluoroolefination of alkyl triflones
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A new synthesis ofgem-difluoroalkenes from readily available alkyl triflones and difluorocarbene precursors such as TMSCF2Br has been reported. The reaction, regardless of electronic effect, givesgem-difluoroalkenes in good to excellent yields. The mechanism may involve deprotonation of triflones, nucleophilic addition, and the elimination of SO2CF3
- Yang, Ren-Yin,Wang, Hui,Xu, Bo
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supporting information
p. 4831 - 4834
(2021/05/25)
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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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- Pd(OAc)2-biuret: A highly efficient, low cost and phosphine-free catalyst system for biaryl synthesis under aerobic conditions at room temperature
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A highly efficient, less expensive and phosphine-free protocol for the Suzuki-Miyaura cross-coupling reactions of aryl halides and aryl boronic acids in iPrOH-H2O solvent under aerobic conditions has been developed. The results demonstrate that the biuret played a crucial role and making this protocol highly efficient. The Pd(OAc)2-biuret system exhibited superb catalytic activity towards the Suzuki-Miyaura cross-coupling reaction of a wide range of aryl halides with aryl boronic acids at room temperature, giving high yields even under very low catalytic loading. This system offers an attractive alternative to the existing protocols since the reaction proceeds in green solvent at room temperature with working simplicity, shorter reaction time, cost-effectiveness and provides the desired products in high yields. The effect of solvent, base as well as catalyst loading on the cross-coupling reaction of aryl halide with arylboronic acid is also described.
- Saikia, Bishwajit
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- New Bidentate N-Sulfonyl-Substituted Aromatic Amines as Chelate Ligand Backbones: Pd Catalyst Generation in C-C Coupling via in Situ and Precatalyst Modes
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A series of six new, bidentate ligands based on N-(2-(R-sulfonamido)benzyl)R-sulfonamide have been isolated as dianionic or monoanionic chelators via condensation of 2-(aminomethyl)aniline with sulfonyl chloride reagents; R = methyl (1 and 1′), tolyl (2 and 2′), 2,4,6-Trimethylphenyl (3), or 2,4,6-Triisopropylphenyl (4). Complexes of ligands 2-4 reacted at room temperature with palladium(ii) acetate in the presence of various monodentate N-donor co-ligands to form complexes Pd2(2dmap), Pd2′(OAc.py), Pd3(2acn), Pd3(2py), Pd4(2acn), and Pd4(2py), which were structurally confirmed by three X-ray crystal analyses. Results of catalysis studies in water showed high turnover frequencies and yields of up to 98 % within 10 min and at 0.2 mol-% palladium catalyst loading. Relative to ligand-free catalysis in the presence of only Pd(OAc)2, the ligand-supported palladium species clearly possess positive catalytic advantage. Furthermore, Suzuki coupling efficiencies by 1: 1 'Pd(OAc)2 + ligand' yielded notably better outcomes than for the 1: 2 'Pd(OAc)2 + ligand' in situ catalyst generation, which reveals that coordinative saturation is undesirable. The size of the complementing monodentate co-ligand was observed to influence the catalytic efficiency such that bulkier co-ligands consistently yielded improved turnover frequency values, which leads to the conclusion that steric repulsion between the synthesised ligands and the bulkier co-ligands aided the generation of vacant coordination sites for the more active complexes. Moderate Heck coupling activity was recorded for the complexes and better activities appear to correlate with moderate bulkiness of ligand 3.
- Oloyede, Hammed Olawale,Akong Akong, Raymond,Woods, Joseph Anthony Orighomisan,G?rls, Helmar,Plass, Winfried,Eseola, Abiodun Omokehinde
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p. 101 - 110
(2020/07/28)
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- A Bifunctional Copper Catalyst Enables Ester Reduction with H2: Expanding the Reactivity Space of Nucleophilic Copper Hydrides
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Employing a bifunctional catalyst based on a copper(I)/NHC complex and a guanidine organocatalyst, catalytic ester reductions to alcohols with H2 as terminal reducing agent are facilitated. The approach taken here enables the simultaneous activation of esters through hydrogen bonding and formation of nucleophilic copper(I) hydrides from H2, resulting in a catalytic hydride transfer to esters. The reduction step is further facilitated by a proton shuttle mediated by the guanidinium subunit. This bifunctional approach to ester reductions for the first time shifts the reactivity of generally considered "soft"copper(I) hydrides to previously unreactive "hard"ester electrophiles and paves the way for a replacement of stoichiometric reducing agents by a catalyst and H2.
- Kaicharla, Trinadh,Ngoc, Trung Tran,Teichert, Johannes F.,Tzaras, Dimitrios-Ioannis,Zimmermann, Birte M.
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supporting information
p. 16865 - 16873
(2021/10/20)
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- (1-Selenocyanatoethyl)benzene: A Selenocyanation Reagent for Site-Selective Selenocyanation of Inert Alkyl C(sp3)-H Bonds
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A new, simple, yet easily accessible, (1-selenocyanatoethyl)benzene has been designed and applied as a SeCN group transfer reagent for selenocyanation of aliphatic C(sp3)-H bonds for the first time. This protocol is featured with mild reaction conditions and wide substrate scope. Control experiments reveal that a radical-group transfer mechanism might be involved.
- Yu, Fei,Li, Chuang,Wang, Chuangye,Zhang, Hongwei,Cao, Zhong-Yan
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supporting information
p. 7156 - 7160
(2021/09/18)
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- Synthesis of tetranuclear complex of Pd(II) with thiosemicarbazone ligands derived from 2-quinolone and its catalytic evaluation in Suzuki–Miyaura-type coupling reactions and alkoxylation of chloroquinolines
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A tetranuclear palladium(II) complex [(Pd(H-6MOQtsc-Ph))4] was obtained from the reaction between 6-methyl-2-oxo-1,2-dihydroquinoline-3-carboxaldehyde-4(N)-phenylthiosemicarbazone [H2-6MOQtsc-Ph] and K2[PdCl4]. The ligand and the Pd(II) complex were characterized by Fourier transform infrared spectroscopy (FT-IR), UV–visible and 1H NMR spectroscopy. X-ray diffraction studies confirmed the tetrameric nature of the complex with the coordination of ligand through quinolone carbonyl, azomethine nitrogen and thiolate sulfur atoms, and the fourth site is occupied by 2-quinolone nitrogen atom of the adjacent ligand. The synthesized complex was tested as catalyst in Suzuki–Miyaura coupling reaction between various chloroquinoline derivatives with phenylboronic acid. The reactions afforded unexpected C-alkoxylated (C-O coupling) products instead of more expected C-arylated (C-C coupling) products in the respective alcoholic mediums. However, the reactions with traditional aryl halides probed with very good yield of the corresponding C-C coupling products.
- Nandhini, Sundar,Dharani, Sivadasan,Elamathi, Chennakrishnan,Dallemer, Frederic,Prabhakaran, Rathinasabapathi
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- Amino-Induced 2D Cu-Based Metal–Organic Framework as an Efficient Heterogeneous Catalyst for Aerobic Oxidation of Olefins
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With the assistance of hydrogen bonds of the o-amino group, we have successfully tuned a coordination structure from a metal–organic polyhedron (MOP) to a two-dimensional (2D) metal–organic framework (MOF). The amino group forms hydrogen bonds with the two vicinal carboxylic groups, and induces the ligand to coordinate with copper ions to form the 2D structure. The obtained 2D Cu-based MOF (Cu-AIA) has been applied as an efficient heterogeneous catalyst in the aerobic epoxidation of olefins by using air as oxygen source. Without the aggregation problem of active sites in MOPs, Cu-AIA possesses much higher reactivity than MOP-1. Furthermore, the amino group of the framework has been used as a modifiable site through post-synthetic metalation (PSMet) to prepare a 2D MOF-supported Pd single-site heterogeneous catalyst, which shows excellent catalytic performance for the Suzuki reaction. It indicates that Cu-AIA can also work as a good 2D MOF carrier for the derivation of other heterogeneous catalysts.
- Bao, Shixiong,Cai, Mengke,Ding, Shujiang,Li, Guangqin,Tang, Jia,Tao, Jinzhang,Wang, Xiaoxia,Xie, Guanqun
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supporting information
(2020/03/13)
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- Palladium-decorated o-phenylenediamine-functionalized Fe3O4/SiO2 magnetic nanoparticles: A promising solid-state catalytic system used for Suzuki–Miyaura coupling reactions
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Palladium-supported o-phenylenediamine-functionalized Fe3O4 magnetic nanoparticles are presented. A convenient synthetic route for the nanocatalyst and also its application in Suzuki–Miyaura coupling of various aryl halides with phenylboronic acids are described. A high reaction yield (98%) was been obtained in a short reaction time (10 min) through use of this highly efficient nanocatalyst. From a mechanistic aspect, firstly, effective electronic interactions between heteroatoms such as oxygen and Pd(II) provide a suitable condition for covalent bonding by the ingredients in the Suzuki–Miyaura coupling reaction. Secondly, Pd(II) is converted to Pd(0) by use of sodium borohydride in the presence of triphenylphosphine in basic conditions, and then it plays a main role in the catalytic process. However, the most distinguished properties of this catalytic system are the ease of catalyst separation and great reusability. The palladium-supported o-phenylenediamine-functionalized Fe3O4 nanoparticles can be easily recovered by use of an external magnet and can reused at least ten times with no significant decline in catalytic activity. This novel system was structurally characterized by various analytical methods, and the results obtained are well interpreted in the context.
- Maleki, Ali,Taheri-Ledari, Reza,Ghalavand, Reza,Firouzi-Haji, Razieh
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- Synthesis and structure activity relationships of cyanopyridone based anti-tuberculosis agents
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Mycobacterium tuberculosis, the causative agent of tuberculosis, relies on thymidylate kinase (MtbTMPK) for the synthesis of thymidine triphosphates and thus also DNA synthesis. Therefore, this enzyme constitutes a potential Achilles heel of the pathogen. Based on a previously reported MtbTMPK 6-aryl-substituted pyridone inhibitor and guided by two co-crystal structures of MtbTMPK with pyridone- and thymine-based inhibitors, we report the synthesis of a series of aryl-shifted cyanopyridone analogues. These compounds generally lacked significant MtbTMPK inhibitory potency, but some analogues did exhibit promising antitubercular activity. Analogue 11i demonstrated a 10-fold increased antitubercular activity (MIC H37Rv, 1.2 μM) compared to literature compound 5. Many analogues with whole-cell antimycobacterial activity were devoid of significant cytotoxicity.
- Boshoff, Helena I. M.,Caljon, Guy,Forbes, He Eun,Hulpia, Fabian,Jian, Yanlin,Munier-Lehmann, Héle?ne,Risseeuw, Martijn D. P.,Van Calenbergh, Serge
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- Boosting multiple photo-assisted and temperature controlled reactions with a single redox-switchable catalyst: Solvents as internal substrates and reducing agent
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An alternative and economically viable process for the synthesis of β-aryl enals, enones and the aryl amines has been developed by partial oxidation of ethanol, isopropanol and N, N-dimethyl formamide (DMF). The formation of β-aryl enals, enones and the aryl amines was catalyzed by a mixed metal oxides layer of cobalt and chromium supported on halloysite nanotubes, designated as CoCr2O4-HNT. The C[sbnd]C and C[sbnd]N bond formation reactions were found to be influenced by temperature and the nature of base. The condensation of aldehyde with in situ generated acetaldehyde by ethanol oxidation forming β-aryl enals occurred selectively at 120 °C. The partial oxidation of isopropanol to acetone and its condensation with aldehydes forming β-aryl enones occurred at room temperature. Increase in temperature caused the liberation of hydrogen gas from isopropanol and allowed the reversible reduction of aldehydes to alcohols. Increase in temperature in isopropanol and increase in base concentration in ethanol causes the selective reduction of aldehydes to alcohols. Besides being active for the Claisen-Schmidt type of reactions and the aryl halides amination process, the synthesized catalyst was also found to be highly active for the photocatalytic oxidation of benzyl alcohols in absence of any external oxidizing agent. The positive holes (h+) generated at the Co(II) site as evident from EPR analysis was considered to be responsible for high photocatalytic activity of the material reducing the recombination rate of holes and electrons (e?). Density Functional Theory calculations were performed to understand the mechanism of ethanol oxidation to acetaldehyde.
- Bania, Kusum K.,Baruah, Manash J.,Bhattacharyya, Pradip K.,Das, Biraj,Karunakar, Galla V.,Roy, Subhasish,Saikia, Lakshi,Saikia, Pinku,Sharma, Mukesh
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p. 104 - 121
(2020/06/01)
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- Nickel-Catalyzed Asymmetric Reductive Arylbenzylation of Unactivated Alkenes
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Herein, we report a nickel-catalyzed asymmetric two-component reductive dicarbofunctionalization of aryl iodide-tethered unactivated alkenes using benzyl chlorides as the challenging coupling partner. This arylbenzylation reaction enables the efficient synthesis of diverse benzene-fused cyclic compounds bearing a quaternary stereocenter with a high tolerance of sensitive functionalities in highly enantioselective manner. The preliminary mechanistic investigations suggest a radical chain reaction mechanism.
- Jin, Youxiang,Yang, Haobo,Wang, Chuan
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supporting information
p. 2724 - 2729
(2020/04/02)
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- Palladium-Catalyzed Selective Reduction of Carbonyl Compounds
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Two new examples of structurally characterized β-diketiminate analogues i.e., conjugated bis-guanidinate (CBG) supported palladium(II) complexes, [LPdX]2; [L= {(ArHN)(ArN)–C=N–C=(NAr)(NHAr)}; Ar = 2,6-Et2-C6H3], X = Cl (1), Br (2) have been reported. The synthesis of complexes 1–2 was achieved by two methods. Method A involves deprotonation of LH by nBuLi followed by the treatment of LLi (insitu formed) with PdCl2 in THF, which afforded compound 1 in good yield (75 %). In Method B, the reaction between free LH and PdX2 (X = Cl or Br) in THF allowed the formation of complexes 1 (Yield 73 %) and 2 (Yield 52 %), respectively. Moreover, these complexes were characterized thoroughly by several spectroscopic techniques (1H, 13C NMR, UV/Vis, FT-IR, and HRMS), including single-crystal X-ray structural and elemental analyses. In addition, we tested the catalytic activity of these complexes 1–2 for the hydroboration of carbonyl compounds with pinacolborane (HBpin). We observed that compound 1 exhibits superior catalytic activity when compared to 2. Compound 1 efficiently catalyzes various aldehydes and ketones under solvent-free conditions. Furthermore, both inter- and intramolecular chemoselectivity hydroboration of aldehydes over other functionalities have been established.
- Sarkar, Nabin,Mahato, Mamata,Nembenna, Sharanappa
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p. 2295 - 2301
(2020/05/18)
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- Metal-Free Direct Deoxygenative Borylation of Aldehydes and Ketones
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Direct conversion of aldehydes and ketones into alkylboronic esters via deoxygenative borylation represents an unknown yet highly desirable transformation. Herein, we present a one-step and metal-free method for carbonyl deoxy-borylation under mild conditions. A wide range of aromatic aldehydes and ketones are tolerated and successfully converted into the corresponding benzylboronates. By the same deoxygenation manifold with aliphatic aldehydes and ketones, we also enable a concise synthesis of 1,1,2-tris(boronates), a family of compounds that currently lack efficient synthetic methods. Given its simplicity and versatility, we expect that this novel borylation approach could show great promise in organoboron synthesis and inspire more carbonyl deoxygenative transformations in both academic and industrial settings.
- Huang, Chia-Yu,Li, Chao-Jun,Li, Jianbin,Qiu, Zihang,Wang, Haining
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supporting information
p. 13011 - 13020
(2020/09/01)
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- Palladium-catalyzed external-CO-free reductive carbonylation of aryl sulfonates
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Pd-catalyzed reductive carbonylation of aryl sulfonates using N-formylsaccharin as a carbon monoxide (CO) surrogate was developed. This external-CO-free carbonylation provides a safe and practical access to aldehydes from phenol derivatives. The reaction has a broad substrate scope, rendering it an attractive method for synthesizing aldehydes.
- Konishi, Hideyuki,Kumon, Minoru,Yamaguchi, Miyuki,Manabe, Kei
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- Synthesis of Enaminone-Pd(II) Complexes and Their Application in Catalysing Aqueous Suzuki-Miyaura Cross Coupling Reaction
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A series of Pd(II)-enaminone complexes, termed Pd(eao)2, have been synthesized and characterized. The investigation on the catalytic activities of these new Pd(II)-reagents has proved that the Pd(eao)2-1 possesses excellent catalytic activity for the Suzuki- Miyaura cross coupling reactions of aryl bromides/chlorides with aryl/vinyl boronic acids in the environmentally benign media of aqueous PEG400 at low loading (5 mol‰). The superiority of this Pd(II)-reagent to those commercial Pd(II) and Pd(0) catalysts in catalyzing the reactions has been confirmed by parallel experiments. What's more, Pd(eao)2-2 has been found as a practical catalyst for the homo-coupling reactions of aryl boronic acids.
- Fu, Leiqing,Cao, Xiaoji,Wan, Jie-Ping,Liu, Yunyun
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p. 254 - 258
(2020/01/25)
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- Synthesis and characterization of a supported Pd complex on volcanic pumice laminates textured by cellulose for facilitating Suzuki-Miyaura cross-coupling reactions
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Herein, a novel high-performance heterogeneous catalytic system made of volcanic pumice magnetic particles (VPMP), cellulose (CLS) natural polymeric texture, and palladium nanoparticles (Pd NPs) is presented. The introduced VPMP@CLS-Pd composite has been designed based on the principles of green chemistry, and suitably applied in the Suzuki-Miyaura cross-coupling reactions, as an efficient heterogeneous catalytic system. Concisely, the inherent magnetic property of VPMP (30 emu g-1) provides a great possibility for separation of the catalyst particles from the reaction mixture with great ease. In addition, high heterogeneity and high structural stability are obtained by this composition resulting in remarkable recyclability (ten times successive use). As the main catalytic sites, palladium nanoparticles (Pd NPs) are finely distributed onto the VPMP@CLS structure. To catalyze the Suzuki-Miyaura cross-coupling reactions producing biphenyl pharmaceutical derivatives, the present Pd NPs were reduced from chemical state Pd2+ to Pd0. In this regard, a plausible mechanism is submitted in the context as well. As the main result of the performed analytical methods (including FT-IR, EDX, VSM, TGA, FESEM, TEM, BTE, and XPS), it is shown that the spherical-shaped nanoscale Pd particles have been well distributed onto the surfaces of the porous laminate-shaped VPMP. However, the novel designed VPMP@CLS-Pd catalyst is used for facilitating the synthetic reactions of biphenyls, and high reaction yields (~98percent) are obtained in a short reaction time (10 min) by using a small amount of catalytic system (0.01 g), under mild conditions (room temperature).
- Soltani, Siavash Salek,Taheri-Ledari, Reza,Farnia, S. Morteza F.,Maleki, Ali,Foroumadi, Alireza
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p. 23359 - 23371
(2020/07/03)
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- N-donor-stabilized Pd(II) species supported by sulphonamide-azo ligands: Ligand architecture, solvent co-ligands, C–C coupling
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In this report, a series of synthetically affordable phosphine-free ligands (L1 – L4) of the form RSO2–NH–Ph–N[dbnd]N–Ph–NH–SO2R were prepared and examined as organic ligands for stabilizing palladium active centers; R = methyl, tolyl or triiso-propylphenyl. Palladium complexes, which were obtained in varying coordination environments as well as with varying complementary co-ligands (water, acetonitrile or pyridine), have been subjected to Suzuki and Heck coupling experiments in order to study molecular level ligand effects on preferred catalyst settings. The appreciable coupling activities for Suzuki and Heck coupling with functional group tolerance were recorded for palladium species generated from the chelate ligands. Results show that, despite the tridentate chelation characteristics of these azo-benzene ligands, the introduction of bulky units at the sulfonyl groups enabled generation of active palladium species with high turnover frequencies; e.g. 5040 h?1 (84% yield) within 5 min at 0.2 mol % loading of Pd.L2.py in only water as solvent. A correlation between catalytic efficiencies and the bulkiness of the coordinated co-ligand was obtained. However, while Suzuki coupling activity increased with increase in co-ligand sizes of the preformed complexes (i.e. water acetonitrile pyridine), the pyridyl co-ligand turned out to be very unfavourable for Heck coupling where the acetonitrile-complemented complexes possessed the higher activities. Therefore, it could be concluded that the best catalyst setting for Suzuki coupling may not be the best for Heck reaction.
- Oloyede, Hammed Olawale,Orighomisan Woods, Joseph Anthony,G?rls, Helmar,Plass, Winfried,Eseola, Abiodun Omokehinde
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- Single monodentate N-donor ligands versus multi-ligand analogues in Pd(II)-catalysed C–C coupling at reduced temperatures
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Deployment of reduced operational temperatures is industrially beneficial and use of the highly efficient, phosphine-based precatalysts is limited by their high costs and inaccessible preparation procedures. In order to study of the influence of coordination environments on catalyst reactivities at reduced temperatures, design of palladium(II) complexes bearing single monodentate N-donor ligands was considered necessary. Consequently, dichloridopalladium(II) complexes of 2-(thiophen-2-yl)-1H-imidazole ligands (1–8), 2,4,5-triphenyloxazole (9) and 2-(1H-imidazol-2-yl)pyridine (10) have been prepared, structurally characterized and studied as N-stabilized precatalysts. Ligand donor strengths were spectroscopically estimated by protonation-deprotonation equilibria. The palladium(II) complexes were obtained in three coordination environments; (i) the mono-ligand complexes bearing trans-solvent co-ligands (PdL.acn and PdL.dmf), (ii) the chlorido-bridged dimers μ-(PdL)2 and (iii) the trans-bis-ligand PdL2 complexes. Considering ambient temperature operations, the catalysis outcomes obtained for the monodentate mono-ligand coordination designs represent an improvement in terms of temperature and reaction time relative to previously reported N-stabilized palladium precatalysts. The mono-ligand pre-catalysts efficiently generate living active palladium species from 40 °C while a trans-bis-ligand phosphine-based pre-catalyst analogue PdI2(PPh3)2 displayed no yield under the same temperature conditions. Trans-bis-ligand coordination is observed to utterly hinders catalyst efficiencies at the studied temperatures and preformed mono-ligand complexes of mono-dentate N-donors provided positive ligand effects while in situ catalyst generation failed. Therefore, the use of multiple ligand equivalents should be discouraged.
- Eseola, Abiodun Omokehinde,G?rls, Helmar,Orighomisan Woods, Joseph Anthony,Plass, Winfried
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- Pd-catalyzed atom-efficient cross-coupling of triarylbismuth reagents with protecting group-free iodophenylmethanols: Synthesis of biarylmethanols
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An atom-efficient procedure for the synthesis of functionalized biarylmethanols via the Pd-catalyzed cross-coupling reactions of differently functionalized iodophenylmethanols and triarylbismuth reagents is described. This protecting group-free direct couplings of 2-, 3- or 4-iodophenylmethanols with triarylbismuth reagents afforded biarylmethanols in good to high yields.
- Meka, Suresh,Rao, Maddali L. N.
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supporting information
(2020/02/11)
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- Preparation method of P-substituted benzyl alcohol
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The invention relates to the technical field of fine chemical synthesis. The invention also discloses a preparation method of p-substituted benzyl alcohol. The preparation method comprises the following steps: taking a p-substituted benzyl halide as a raw material; adding a hydrolysis agent into a water solvent; simultaneous dropwise adding an aqueous alkali, carrying out hydrolysis reaction whilean ester is generated, so that the generation of impurities is effectively controlled, and the use amount of the hydrolysis agent is reduced; and specifically, first, adding the hydrolysis agent intowater, stirring for dissolving, adding a compound shown as a formula I, dropwise adding the aqueous alkali, carrying out heat preservation reaction, cooling a reaction solution to a refining temperature after hydrolysis is completed, adding a certain amount of a refining solvent, stirring for dissolving organic matters, standing for layering, evaporating excessive part of water from a lower waterlayer while the lower water layer is hot, and applying an obtained product to the next hydrolysis reaction; cooling and crystallizing an organic layer, filtering and drying to obtain a p-substitutedbenzyl alcohol finished product. The hydrolysis agent is introduced, so that the generation of impurities is reduced, the product yield and quality are improved, no organic solvent is added in the reaction process, the safety risk is reduced, the environmental pollution is reduced, the operation is simple, and the conditions are mild.
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Paragraph 0043-0048
(2020/08/09)
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- Operando Spectroscopic and Kinetic Characterization of Aerobic Allylic C-H Acetoxylation Catalyzed by Pd(OAc)2/4,5-Diazafluoren-9-one
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Allylic C-H acetoxylations are among the most widely studied palladium(II)-catalyzed C-H oxidation reactions. While the principal reaction steps are well established, key features of the catalytic mechanisms are poorly characterized, including the identity of the turnover-limiting step and the catalyst resting state. Here, we report a mechanistic study of aerobic allylic acetoxylation of allylbenzene with a catalyst system composed of Pd(OAc)2 and 4,5-diazafluoren-9-one (DAF). The DAF ligand is unique in its ability to support aerobic catalytic turnover, even in the absence of benzoquinone or other co-catalysts. Herein, we describe operando spectroscopic analysis of the catalytic reaction using X-ray absorption and NMR spectroscopic methods that allow direct observation of the formation and decay of a palladium(I) species during the reaction. Kinetic studies reveal the presence of two distinct kinetic phases: (1) a burst phase, involving rapid formation of the allylic acetoxylation product and formation of the dimeric PdI complex [PdI(DAF)(OAc)]2, followed by (2) a post-burst phase that coincides with evolution of the catalyst resting state from the PdI dimer into a π-allyl-PdII species. The data provide unprecedented insights into the role of ancillary ligands in supporting catalytic turnover with O2 as the stoichiometric oxidant and establish an important foundation for the development of improved catalysts for allylic oxidation reactions.
- Jaworski, Jonathan N.,Kozack, Caitlin V.,Tereniak, Stephen J.,Knapp, Spring Melody M.,Landis, Clark R.,Miller, Jeffrey T.,Stahl, Shannon S.
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supporting information
p. 10462 - 10474
(2019/07/09)
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- Homogeneous Hydrogenation with a Cobalt/Tetraphosphine Catalyst: A Superior Hydride Donor for Polar Double Bonds and N-Heteroarenes
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The development of catalysts based on earth abundant metals in place of noble metals is becoming a central topic of catalysis. We herein report a cobalt/tetraphosphine complex-catalyzed homogeneous hydrogenation of polar unsaturated compounds using an air- and moisture-stable and scalable precatalyst. By activation with potassium hydroxide, this cobalt system shows both high efficiency (up to 24 000 TON and 12 000 h-1 TOF) and excellent chemoselectivities with various aldehydes, ketones, imines, and even N-heteroarenes. The preference for 1,2-reduction over 1,4-reduction makes this method an efficient way to prepare allylic alcohols and amines. Meanwhile, efficient hydrogenation of the challenging N-heteroarenes is also furnished with excellent functional group tolerance. Mechanistic studies and control experiments demonstrated that a CoIH complex functions as a strong hydride donor in the catalytic cycle. Each cobalt intermediate on the catalytic cycle was characterized, and a plausible outer-sphere mechanism was proposed. Noteworthy, external inorganic base plays multiple roles in this reaction and functions in almost every step of the catalytic cycle.
- Duan, Ya-Nan,Du, Xiaoyong,Cui, Zhikai,Zeng, Yiqun,Liu, Yufeng,Yang, Tilong,Wen, Jialin,Zhang, Xumu
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supporting information
p. 20424 - 20433
(2019/12/27)
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- Deoxygenative cross-electrophile coupling of benzyl chloroformates with aryl iodides
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This work describes Ni-catalyzed cross-electrophile coupling of benzyl chloroformate derivatives with aryl iodides that generates a wide range of diaryl methane products. The mild reaction conditions merit the C-O bond radical fragmentation of benzyl chloroformates via halide abstraction or a single electron reduction by a Ni catalyst. This work offers a new substrate type for cross-electrophile couplings.
- Pan, Yingying,Gong, Yuxin,Song, Yanhong,Tong, Weiqi,Gong, Hegui
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supporting information
p. 4230 - 4233
(2019/05/06)
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- A Practical and Stereoselective In Situ NHC-Cobalt Catalytic System for Hydrogenation of Ketones and Aldehydes
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Homogeneous catalytic hydrogenation of carbonyl groups is a synthetically useful and widely applied organic transformation. Sustainable chemistry goals require replacing conventional noble transition metal catalysts for hydrogenation by earth-abundant base metals. Herein, we report how a practical in situ catalytic system generated by easily available pincer NHC precursors, CoCl2, and a base enabled efficient and high-yielding hydrogenation of a broad range of ketones and aldehydes (over 50 examples and a maximum turnover number [TON] of 2,610). This is the first example of NHC-Co-catalyzed hydrogenation of C=O bonds using flexible pincer NHC ligands consisting of a N-H substructure. Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized by fine-tuning of the steric bulk of pincer NHC ligands. Additionally, a bis(NHCs)-Co complex was successfully isolated and fully characterized, and it exhibits excellent catalytic activity that equals that of the in-situ-formed catalytic system. Catalytic hydrogenation is a powerful tool for the reduction of organic compounds in both fine and bulk chemical industries. To improve sustainability, more ecofriendly, inexpensive, and earth-abundant base metals should be employed to replace the precious metals that currently dominate the development of hydrogenation catalysts. However, the majority of the base-metal catalysts that have been reported involve expensive, complex, and often air- and moisture-sensitive phosphine ligands, impeding their widespread application. From a mixture of the stable CoCl2, imidazole salts, and a base, our newly developed catalytic system that formed easily in situ enables efficient and stereoselective hydrogenation of C=O bonds. We anticipate that this easily accessible catalytic system will create opportunities for the design of practical base-metal hydrogenation catalysts. A practical in situ catalytic system generated by a mixture of easily available pincer NHC precursors, CoCl2, and a base enabled highly efficient hydrogenation of a broad range of ketones and aldehydes (over 50 examples and up to a turnover number [TON] of 2,610). Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized in high selectivities. Moreover, the preparation of a well-defined bis(NHCs)-Co complex via this pincer NHC ligand consisting of a N-H substructure was successful, and it exhibits equally excellent catalytic activity for the hydrogenation of C=O bonds.
- Zhong, Rui,Wei, Zeyuan,Zhang, Wei,Liu, Shun,Liu, Qiang
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supporting information
p. 1552 - 1566
(2019/06/14)
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- Pyrazole compounds as well as preparation method and application thereof
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The invention provides pyrazole compounds with neuraminidase (NA) inhibitory activity as well as a preparation method and application thereof in pharmacy, and specifically relates to a compound shownin a formula (I), and pharmaceutically acceptable salt, an isomer and a prodrug thereof, and the definition of various groups is as described in the description. The invention further relates to pharmaceutic preparations and pharmaceutical compositions of the compounds and application of the pharmaceutic preparations and the pharmaceutical compositions in treatment of diseases caused by influenzavirus infection. The pyrazole compounds provided by the invention have good inhibitory effects on H1N1 influenza A virus infected cells.
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Paragraph 0079; 0081; 0082; 0083; 0084
(2019/10/01)
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- Importance of monodentate mono-ligand designs in developing N-stabilized Pd catalysts for efficient ambient temperature C[sbnd]C coupling: Donor strengths and steric features
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Unfriendly temperature profiles and costs of carbon coupling catalysis, which pose challenge to both synthetic organic chemists as well as industrial applicability, motivated our design of new monodentate N-donors as support ligands for the purpose of constructing ambient temperature precatalysts that are molecularly close to the hypothetical active forms. Therefore, a series of sterically varied monodentate N-donor imidazoles (1–7) and oxazoles (8–9) have been synthesized and their N-donor strengths, which were estimated as pKas, are systematically varied from 0.9 to 8.5 by substituent variations. Eleven target mono-ligand complexes (1-PdCl2MeCN – 9-PdCl2MeCN, 6-PdCl2PhCN and 7-PdCl2PhCN) and six trans-bis-ligand complexes (12-PdCl2, 22-PdCl2, 32-PdCl2, 62-PdCl2, 12-Pd(OAc)2 and 22-Pd(OAc)2) were isolated and catalytically studied along with PdI2(PPh3)2. Results of coupling reactions, which were conducted both via in situ ‘Pd(II) salt + ligand’ approach and by use of the precatalysts, show that the mono-ligand precatalyst designs (1-PdCl2MeCN – 9-PdCl2MeCN, 6-PdCl2PhCN and 7-PdCl2PhCN) represent a true catalyst improvement initiative among the phosphine-free catalyst community; i.e. yields approaching 100% (TOF ≈ 2000) at 0.2 mol % catalyst loading, 45 °C and within 15 min. On the other hand, the complexes with trans-bis-ligand coordination were inactive at ambient temperatures. Therefore, it was concluded that coordinative saturation, which results from implementing two or more ligand equivalents or use of polydentate ligands on palladium, should be strongly discouraged. Such saturation necessitates the undesirable and avoidable high temperature necessities, long reflux durations and needlessly high catalyst loadings. Correlation between catalyst activity and donor strengths or steric properties were analysed leading to important conclusions. The catalyst design also supported coupling of activated aryl chlorides from 60 °C while Heck coupling activities were observed only at the early minutes of reactions.
- Eseola, Abiodun Omokehinde,G?rls, Helmar,Plass, Winfried
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- Tetranuclear Palladacycles of 3-Acetyl-7-methoxy-2 H-chromen-2-one Derived Schiff Bases: Efficient Catalysts for Suzuki-Miyaura Coupling in an Aqueous Medium
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Tetranuclear organopalladium(II) complexes 1-3 and mononuclear complex 4 have been synthesized by the complexation of 3-acetyl-7-methoxy-2H-chromen-2-one derived Schiff bases with potassium tetrachloropalladate K2[PdCl4]. Structural confirmation for the complexes (1-3) has been achieved by single-crystal X-ray diffraction analysis. The ligands are found to bind with the palladium ion through its azomethine nitrogen, thiolate sulfur, and C4 carbon atom of the coumarin moiety subsequent to C-H activation. The monomeric nature of complex 4 was confirmed from its mass spectroscopic data. In complex 4, coordination occurred via the lactone oxygen, azomethine nitrogen, and thiolate sulfur atoms. Computational study has been used to determine the optimized molecular structures of the complexes. An explanation on the energies of their highest occupied and lowest unoccupied molecular orbital levels and their electronic spectra has also been provided on the basis of the theoretical calculations. A systematic study of the application of these complexes as catalysts in Suzuki-Miyaura coupling (SMC) has been done with different aryl halides and phenyl boronic acid in an aqueous medium. Optimization of the reaction indicated that complex 2 exhibits greater efficiency than other complexes. An appreciable yield of the coupled products was observed with the minimum use of catalyst (μmol), and the C-C coupling has been confirmed by GC/GC-MS. An interesting result of our catalyst is the coupling of four different chloroquinolines with phenyl boronic acid to afford the coupled products in good yields.
- Dharani, Sivadasan,Kalaiarasi, Giriraj,Sindhuja, Dharmalingam,Lynch, Vincent M.,Shankar, Ramasamy,Karvembu, Ramasamy,Prabhakaran, Rathinasabapathi
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p. 8045 - 8055
(2019/06/07)
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- A Direct Approach to Decoration of Bioactive Compounds via C-H Amination Reaction
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The development of new methods to achieve the direct synthesis of bioactive organic molecules is always an important topic in organic synthesis. We hereby demonstrate that N-methoxyamide is an excellent amino source in the iridium-catalyzed intermolecular C-H amination reaction. The linkage of two bioactive organic molecules can be well achieved with this new protocol. More than 20 examples of decorated bioactive compounds were reported, which can facilitate the discovery of new bioactive molecules.
- Ju, Guodong,Yuan, Chunchen,Wang, Dongjie,Zhang, Jingyu,Zhao, Yingsheng
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supporting information
p. 9852 - 9855
(2019/12/24)
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- Homo- and Heterobimetallic Complexes Bearing NHC Ligands: Applications in α-Arylation of Amide, Suzuki–Miyaura Coupling Reactions, and Tandem Catalysis
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A heterobimetallic IrIII/PdII complex from a dicarbene donor ligand featuring cyclometalated IrIII and PEPPSI type PdII is presented along with a homodinuclear PEPPSI type PdII complex starting from the same bis-imidazolium salt. All the PdII complexes are active precatalyst in both α-arylation and Suzuki–Miyaura coupling reactions. The heterobimetallic IrIII/PdII complex shows much higher yields in tandem C–C coupling/transfer hydrogenation reactions compared to the equimolar mixture of their mononuclear PdII and IrIII counterparts.
- Majumder, Adhir,Naskar, Rajat,Roy, Pallabi,Maity, Ramananda
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p. 1810 - 1815
(2019/03/17)
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- Controlled Reduction of Carboxamides to Alcohols or Amines by Zinc Hydrides
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New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH-ZnI2 system delivers alcohols and NaH-ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2)∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H?Zn?Cl)2 is the key species for the production of amines.
- Ong, Derek Yiren,Yen, Zhihao,Yoshii, Asami,Revillo Imbernon, Julia,Takita, Ryo,Chiba, Shunsuke
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supporting information
p. 4992 - 4997
(2019/03/13)
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- Synthesis of Aryl Trimethylstannane via BF3·OEt2-Mediated Cross-Coupling of Hexaalkyl Distannane Reagent with Aryl Triazene at Room Temperature
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BF3·OEt2-mediated cross-coupling of (SnMe3)2 with aryl triazene offers a new strategy for the synthesis of aryl stannane. A variety of synthetically useful aryl trimethylstannanes were produced in moderate to good yields with this metal-free approach. One-pot sequential Stille cross-coupling with different aryl bromides provides a short entry to both symmetrical and unsymmetrical biaryl compounds.
- Mao, Shuai,Chen, Zhengkai,Wang, Lu,Khadka, Daulat Bikram,Xin, Minhang,Li, Pengfei,Zhang, San-Qi
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p. 463 - 471
(2019/01/10)
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- Enhancement of Suzuki–Miyaura coupling reaction by photocatalytic palladium nanoparticles anchored to TiO2 under visible light irradiation
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Plasmonic property and catalytic performance of Pd anchored to TiO2 for Suzuki?Miyaura coupling (SMC) reactions are reported. Different from previous reports, this semiconductor with band gap ≥3 eV can afford C–C bond formation for SMC. Nano Pd/TiO2 was successfully synthesized through a photodeposition method under sunlight. The size of Pd nanoparticles onto the surface of TiO2 led to enhancement of localized surface plasmon resonance. This visible-light-harvesting heterogeneous photocatalyst sufficiently promoted substrates toward coupling reaction products at ambient temperature in aqueous media. Photo-generated electron-hole pairs under visible light irradiation, are the key components of activation of the substrates.
- Koohgard, Mehdi,Hosseini-Sarvari, Mona
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- Hydrogenation of Carbonyl Derivatives Catalysed by Manganese Complexes Bearing Bidentate Pyridinyl-Phosphine Ligands
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Manganese(I) catalysts incorporating readily available bidentate 2-aminopyridinyl-phosphine ligands achieve a high efficiency in the hydrogenation of carbonyl compounds, significantly better than parent ones based on more elaborated and expensive tridentate 2,6-(diaminopyridinyl)-diphosphine ligands. The reaction proceeds with low catalyst loading (0.5 mol%) under mild conditions (50 °C) with yields up to 96%. (Figure presented.).
- Wei, Duo,Bruneau-Voisine, Antoine,Chauvin, Téo,Dorcet, Vincent,Roisnel, Thierry,Valyaev, Dmitry A.,Lugan, No?l,Sortais, Jean-Baptiste
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supporting information
p. 676 - 681
(2017/12/26)
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- Triazole-Functionalized Silica Supported Palladium(II) Complex: A Novel and Highly Active Heterogeneous Nano-catalyst for C–C Coupling Reactions in Aqueous Media
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Abstract: Two novel triazole-modified silica supports A and B were successfully prepared via “click” reaction of azide-functionalized SiO2 with propargyl alcohol (A) and propargyl amine (B), in which the click-triazole as an important functional entity, in addition to a molecular linker, provides capabilities of metal coordination as an excellent chelator. Treatment of the resulting click-supports with Pd(OAc)2 afforded the click-catalysts A and B, which were well characterized and evaluated in Suzuki–Miyaura coupling in terms of activity and recyclability in H2O/EtOH solvent. The catalyst A showed more reasonable results and so, was applied as a highly efficient and recyclable catalyst in the coupling reactions of various aryl halides with phenylboronic acid under phosphine-free and low Pd loading conditions. Graphical Abstract: Two novel nano pd-catalysts were successfully prepared by immobilization of Pd(OAc)2 onto the silica supports containing the nitrogen-rich triazole chelators and were investigated in Suzuki–Miyaura coupling in aqueous solvent.
- Hajipour, Abdol Reza,Mohammadsaleh, Fatemeh
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p. 1035 - 1046
(2018/02/14)
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- Synthesis and palladium(II) metal chemistry of thiazoline/imidazoline derived ligands: An efficient catalyst for cross-coupling reactions of arylboronic acids with acid chlorides and aryl halides
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The synthesis, reactivity, spectroscopic characterization and catalytic activities of a series of Pd(II) complexes bearing the chelating ligands 2-(4,5-dihydrothiazol-2-yl)aniline (2) and 2-(4,5-dihydro-1H-imidazol-2-yl)aniline (3) are reported. The reactions of 2 with [Pd(COD)Cl2] in 1:1 and 1:2 (ligand into metal and metal into ligand) molar ratios afforded the mononuclear complexes, PdCl2{κ2?N,S ? 2?(4,5-dihydrothiazol-2-yl)aniline} (4), Pd{κ2?N,N’?2?(4,5-dihydrothiazol-2-yl)aniline}2 (5) and Pd{κ12?N,N’?κ22?N,S ? 2?(4,5-dihydrothiazol-2-yl)aniline}2 (6), respectively, in good yields. The neutral mononuclear palladium complexes PdCl2{κ2?N,N’?(4,5-dihydro-1H-imidazol-2-yl)aniline} (7) and Pd{κ2?N,N’?2?(4,5-dihydro-1H-imidazol-2-yl)aniline}2 (8) were synthesized using [Pd(COD)Cl2] with appropriate molar ratios. The palladium complexes 4–8 were evaluated for their catalytic activities in base assisted cross coupling reactions between acid chlorides and aryl halide with boronic acids. The complex 4 was found to be an efficient catalyst for producing unsymmetrical ketones (TOF = 19.8 min?1) while complex 7 was effective for making biaryls (TOF = 19.8 min?1).
- Sudharsan, Murugesan,Suresh
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p. 598 - 608
(2018/09/18)
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- Preparation method for Biphenyl-4-methanol monomer and Biphenyl-4-methanol monomer using the same method
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The present invention relates to a method for producing biphenyl-4-methanol based monomers, and more specifically, to a method for producing biphenyl-4-methanol based monomers which can be used as a high luminance film material. In particular, biphenyl-4-methanol (PC-423) is reacted with ethylene oxide or propylene oxide, and then reacted with acryl chloride, to synthesize biphenyl-4-methanol based monomers (PC-324-n) having high refractive index and low viscosity.(S100) Preparing biphenyl-4-methanol (PC-423)(S200) Synthesizing a second monomer (PC-423-n)(S300) Synthesizing a third monomer (PC-324-n)COPYRIGHT KIPO 2018
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Paragraph 0054; 0055-0057
(2019/01/06)
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- Photoredox-Catalyzed Decarboxylative Oxidation of Arylacetic Acids
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A photoredox-catalyzed decarboxylative oxidation of arylacetic acids, which are privileged scaffolds in pharmaceuticals, is reported herein. The established method is operationally simple and a variety of substrates are applicable, providing rapid access to dehomologated bioisosteres of common pharmaceuticals.
- Sakakibara, Yota,Cooper, Phillippa,Murakami, Kei,Itami, Kenichiro
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supporting information
p. 2410 - 2413
(2018/06/04)
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- Ru-Photoredox-Catalyzed Decarboxylative Oxygenation of Aliphatic Carboxylic Acids through N-(acyloxy)phthalimide
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Decarboxylative aminoxylation of aliphatic carboxylic acid derivatives with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) in the presence of ruthenium photoredox catalysis is reported. The key transformation entails a highly efficient photoredox catalytic cycle using Hantzsch ester as a reductant. The ensuing alkoxyamine can be readily converted to the corresponding alcohol in one pot, representing an alternative approach to access aliphatic alcohols under photoredox conditions.
- Zheng, Chao,Wang, Yuting,Xu, Yangrui,Chen, Zhen,Chen, Guangying,Liang, Steven H.
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supporting information
p. 4824 - 4827
(2018/08/24)
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- Method for synthesizing 4-hydroxymethyl-biphenyl
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The invention discloses a method for synthesizing 4-hydroxymethyl-biphenyl, belonging to the field of organic synthesis. The method comprises the steps of enabling biphenyl, which is taken as a raw material, to react with NXS to generate 4-halogenated biphenyl; then, enabling the generated 4-halogenated biphenyl to react with magnesium metal in presence of chlorinated n-butane so as to generate aGrignard reagent; then, enabling the generated Grignard reagent to react with XCH2OR, and carrying out acidic hydrolysis to obtain the 4-hydroxymethyl-biphenyl. The method has the advantages of beingeasy in obtaining of raw material, low in cost and mild in conditions, thus having a process amplification prospect.
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Paragraph 0020; 0021; 0024; 0025
(2018/03/28)
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- 4 - Biphenyl methanol synthesis method
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The invention discloses a 4-biphenyl methanol synthetic method. The method comprises the steps that 1, biphenyl, paraformaldehyde, phosphoric acid, concentrated hydrochloric acid and a catalyst are mixed and heated to 100-120 DEG C, and are subjected to a reaction in a closed system for 2-48 h, cooled and layered into a water layer and an organic layer; 2, the water layer obtained in the step 1 is removed, water is added into the organic layer, heating reflux is performed for 8-48 h, cooling and filtering are performed, and a crude product is obtained; 3, an organic solvent is used for achieving recrystallization on the crude product obtained in the step 2, and 4-biphenyl methanol is obtained. The 4-biphenyl methanol synthetic method has the advantages of being capable of obtaining raw materials easily, low in cost, suitable for industrial production and the like.
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Paragraph 0050; 0051
(2018/04/03)
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- N-heterocyclic carbene-Pd(II) complex based on theophylline supported on Fe3O4@SiO2 nanoparticles: Highly active, durable and magnetically separable catalyst for green Suzuki-Miyaura and Sonogashira-Hagihara coupling reactions
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In this paper, a novel heterogeneous palladium catalyst was synthesized by anchoring N-heterocyclic carbene-Pd(II) complex based on theophylline on magnetic Fe3O4@SiO2 nanoparticles. The synthesized magnetic composite was characterized by fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA), vibration sample magnetometry (VSM), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), N2 adsorption-desorption isotherm analysis (BET), UV–vis spectroscopy and elemental analysis. Also, loading content of palladium on the catalyst was measured by inductive coupled plasma (ICP) analysis. The synthesized catalyst was used successfully for the Suzuki cross-coupling reactions of various aryl halides (I, Br, Cl) with phenylboronic acids. This reaction was best performed in water as a green solvent in the presence of just 0.37–0.5 mol% of the catalyst at 60 °C. Also, we have reported this recyclable catalytic system as a stable phosphine-free Pd catalyst for the Sonogashira cross-coupling of aryl halides (I, Br, Cl) with terminal aromatic and aliphatic alkynes under solvent-free conditions. All coupling reactions proceeded with good to excellent yields. The catalyst showed good stability and was recovered and reused for eight reaction cycles without a significant loss in its catalytic activity. Also, the leaching of the catalyst has been examined by a hot filtration test and ICP-AES analysis.
- Esmaeilpour, Mohsen,Sardarian, Ali Reza,Firouzabadi, Habib
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- Selective C-H halogenation over hydroxylation by non-heme iron(iv)-oxo
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Non-heme iron based halogenase enzymes promote selective halogenation of the sp3-C-H bond through iron(iv)-oxo-halide active species. During halogenation, competitive hydroxylation can be prevented completely in enzymatic systems. However, synthetic iron(iv)-oxo-halide intermediates often result in a mixture of halogenation and hydroxylation products. In this report, we have developed a new synthetic strategy by employing non-heme iron based complexes for selective sp3-C-H halogenation by overriding hydroxylation. A room temperature stable, iron(iv)-oxo complex, [Fe(2PyN2Q)(O)]2+ was directed for hydrogen atom abstraction (HAA) from aliphatic substrates and the iron(ii)-halide [FeII(2PyN2Q)(X)]+ (X, halogen) was exploited in conjunction to deliver the halogen atom to the ensuing carbon centered radical. Despite iron(iv)-oxo being an effective promoter of hydroxylation of aliphatic substrates, the perfect interplay of HAA and halogen atom transfer in this work leads to the halogenation product selectively by diverting the hydroxylation pathway. Experimental studies outline the mechanistic details of the iron(iv)-oxo mediated halogenation reactions. A kinetic isotope study between PhCH3 and C6D5CD3 showed a value of 13.5 that supports the initial HAA step as the RDS during halogenation. Successful implementation of this new strategy led to the establishment of a functional mimic of non-heme halogenase enzymes with an excellent selectivity for halogenation over hydroxylation. Detailed theoretical studies based on density functional methods reveal how the small difference in the ligand design leads to a large difference in the electronic structure of the [Fe(2PyN2Q)(O)]2+ species. Both experimental and computational studies suggest that the halide rebound process of the cage escaped radical with iron(iii)-halide is energetically favorable compared to iron(iii)-hydroxide and it brings in selective formation of halogenation products over hydroxylation.
- Rana, Sujoy,Biswas, Jyoti Prasad,Sen, Asmita,Clémancey, Martin,Blondin, Geneviève,Latour, Jean-Marc,Rajaraman, Gopalan,Maiti, Debabrata
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p. 7843 - 7858
(2018/10/31)
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- Mild, Redox-Neutral Formylation of Aryl Chlorides through the Photocatalytic Generation of Chlorine Radicals
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We report a redox-neutral formylation of aryl chlorides that proceeds through selective 2-functionalization of 1,3-dioxolane through nickel and photoredox catalysis. This scalable benchtop approach provides a distinct advantage over traditional reductive carbonylation in that no carbon monoxide, pressurized gas, or stoichiometric reductant is employed. The mild conditions give unprecedented scope from abundant and complex aryl chloride starting materials.
- Nielsen, Matthew K.,Shields, Benjamin J.,Liu, Junyi,Williams, Michael J.,Zacuto, Michael J.,Doyle, Abigail G.
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supporting information
p. 7191 - 7194
(2017/06/13)
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- Niobium(v)-catalyzed defluorinative triallylation of α,α,α-trifluorotoluene derivatives by triple C-F bond activation
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The catalytic defluorinative triallylation of α,α,α-trifluorotoluene derivatives via C-F bond activation has been achieved by the use of the NbCl5 catalyst and allyltrimethylsilane as a nucleophile. Several control experiments have suggested the importance of the conjugation between the fluorine atoms and the carbocation center in this reaction.
- Saito, Kodai,Umi, Taishi,Yamada, Takayuki,Suga, Takuya,Akiyama, Takahiko
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supporting information
p. 1767 - 1770
(2017/03/09)
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- Zinc-Mediated Efficient and Selective Reduction of Carbonyl Compounds
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We herein describe for the first time that an optimized combination of Zn and NH4Cl can be used for the selective reduction of aldehydes and ketones to the corresponding alcohols. The aldehyde and keto groups are selectively reduced in the presence of azide, cyano, epoxy, ester, and carbon–carbon double-bond functional groups. A broad functional-group compatibility, chemoselective reduction of aldehydes in the presence of ketones, and selective reduction of isatins at the C3 carbonyl group are the highlights of the present method.
- Mandal, Tirtha,Jana, Snehasish,Dash, Jyotirmayee
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p. 4972 - 4983
(2017/09/13)
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- Transfer Hydrogenation of Carbonyl Derivatives Catalyzed by an Inexpensive Phosphine-Free Manganese Precatalyst
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A very simple and inexpensive catalytic system based on abundant manganese as transition metal and on an inexpensive phosphine-free bidendate ligand, 2-(aminomethyl)pyridine, has been developed for the reduction of a large variety of carbonyl derivatives with 2-propanol as hydrogen donor. Remarkably, the reaction proceeds at room temperature with low catalyst loading (down to 0.1 mol %) and exhibits a good tolerance toward functional groups. High TON (2000) and TOF (3600 h-1) were obtained.
- Bruneau-Voisine, Antoine,Wang, Ding,Dorcet, Vincent,Roisnel, Thierry,Darcel, Christophe,Sortais, Jean-Baptiste
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supporting information
p. 3656 - 3659
(2017/07/15)
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