- Palladium Nanoparticles in Polymers: Catalyst for Alkene Hydrogenation, Carbon-Carbon Cross-Coupling Reactions, and Aerobic Alcohol Oxidation
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A new recyclable palladium catalyst was synthesized by a simple procedure from readily available reagents, which is composed of palladium nanoparticles dispersed in an organic polymer. This catalyst is robust, and highly active in many organic transformations including alkene and alkyne hydrogenation, carbon-carbon cross-coupling reactions, and aerobic alcohol oxidation.
- Park, Cheon Min,Kwon, Min Serk,Park, Jaiwook
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- Continuous-Flow microreactor Chemistry under High-Temperature/pressure
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High-temperature organic synthesis can be performed under continuous-flow conditions in a stainless steel microtubular flow reactor capable of achieving temperatures of 350 °C and 200 bar. Under these extreme experimental environments transformations normally performed in a high-boiling solvent at reflux temperature - or under sealed-vessel microwave conditions - can be readily converted to a flow regime by using lower boiling solvents in or near their supercritical state. Wiley-VCH Verlag GmbH & Co, KGaA.
- Razzaq, Tahseen,Glasnov, Toma N.,Kappe, C. Oliver
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- Highly regioselective rhodium-catalysed hydroformylation of unsaturated Esters: The first practical method for quaternary selective carbonylation
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Highly regioselective hydroformylation of unsaturated esters can be achieved when a highly reactive, ligand-modified, rhodium catalyst is employed near ambient temperatures (15-50°C) and pressures over 30 bar. The use of 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phosphaadamantane shows distinct advantages over other commonly applied phosphanes in terms of reaction rate, and regio- and chemoselectivity. Hydroformylation of a range 1,1-di- and 1,1,2-trisubstituted unsaturated esters yields quaternary aldehydes that are forbidden products according to Keulemans Rule. The aldehydes can be reductively aminated with molecular hydrogen to give β-amino acid esters in high yield. The overall green chemical process involves converting terminal alkynes into unusual β-amino acid esters with only water generated as an essential byproduct. This catalytic system has also been applied to the hydroformylation of simple 1,2-disubstitued unsaturated esters, which have been hydroformylated with excellent α-selectivity and good chemo-selectivity for the first time.
- Clarke, Matthew L.,Roff, Geoffrey J.
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- Practical access to the polymer incarcerated platinum (PI Pt) catalyst and its application to hydrogenation
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Polymer incarcerated platinum catalysts (PI Pt) were conveniently prepared from PtCl2(COD) or H2PtCl6·6H 2O and styrene copolymers via reduction of the Pt sources with triethylamine, coacervation, and cross-linking. The Pt catalysts have been successfully applied to catalytic hydrogenation including saturation of heterocyclic compounds. The Royal Society of Chemistry 2006.
- Miyazaki, Yoji,Hagio, Hiroyuki,Kobayashi, Sh
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- Highly efficient esterification of carboxylic acids with alcohols by montmorillonite enwrapped titanium as a heterogeneous acid catalyst
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Montmorillonite-enwrapped titanium catalyst was found to efficiently promote the esterification of carboxylic acids with alcohols. In comparison to other catalysts reported to date, this heterogeneous catalyst offers a remarkably simple workup procedure, and is reusable without any appreciable loss in its activity and selectivity.
- Kawabata, Tomonori,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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- Acylations and Alkylations of an Ester Enolate in High Yield at Room Temperature on Polystyrene Supports
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Polymer-bound esters of 3-phenylpropanoic acid are converted to enolates at room temperature and acylated and alkylated in 73-87percent isolated yields with little or no self-condensation of ester.
- Chang, Young H.,Ford, Warren T.
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- Hydroesterification of Olefins Catalyzed by Pd(OAc)2 Immobilized on Montmorillonite
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Palladium acetate immobilized on montmorillonite is an efficient catalyst for the hydroesterification of olefins with carbon monoxide and methanol, in the presence of triphenylphosphine and an acid promoter, affording branched chain esters.The reaction is regiospecific for aryl olefins as well as for vinyl benzoate and regioselective for aliphatic olefins.
- Lee, Chul Woo,Alper, Howard
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- Asymmetric hydroesterification of styrene using catalysts with planar-chiral ferrocene oxazoline ligands
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Chiral P,N-ferrocene ligands, 1-diphenylphosphino-1′-[(S)-4-isopropyl-2.5-oxazolinyl]-2′-(S p)-(trimethylsilyl)-ferrocene and its diastereomer, and 1-diphenylphosphino-1′-[(S)-4-isopropyl-2.5-oxazolinyl]-2′(S p)-(diphenylphosphino)-ferrocene and its diastereomer were used in the palladium-catalyzed asymmetric hydroesterification of styrene. The role of these ligands, which contain central, axial, and planar chirality, on the stereochemical outcome was investigated. A significant effect of using CuCl2 as a co-catalyst on the reaction was observed. Excellent regioselectivity (b/n >99:1) with low ee (28%) was obtained in the presence of CuCl2; moderate enantioselectivity (64% ee) but low regioselectivity (b/n, 40/60) was obtained in the absence of CuCl2.
- Wang, Lailai,Kwok, Wai Him,Chan, Albert S. C.,Tu, Tao,Hou, Xuelong,Dai, Lixin
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- Highly active and selective palladium catalyst for hydroesterification of styrene and vinyl acetate promoted by polymeric sulfonic acids
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Highly efficient, selective and recyclable palladium catalyst systems for hydroesterification of styrene and vinyl acetate were realized by using 1,2-bis(di-tert-butylphosphinomethyl)benzene as ligand and polymeric sulfonic acids of limited SO3H loadings as promoter. The Royal Society of Chemistry 2005.
- Ooka, Hirohito,Inone, Tsutomu,Itsuno, Shinichi,Tanaka, Masato
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- Tris(2,4,6-trimethoxyphenyl)phosphine: Base catalyst in the transformation of α,β-unsaturated aldehydes to saturated carboxylic-acid derivatives
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We have focused on the basicity of Tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP) in organic synthesis. To extend the utility of TTMPP, we examined the reaction of α,β-unsaturated aldehydes with trimethylsilyl cyanide in the presence of TTMPP. Furthermore, to clarify the basic character of TTMPP, we measured 31P NMR of TTMPP and related compounds. First, the reaction of cinnamaldehydes with trimethylsilyl cyanide in the presence of a catalytic amount of TTMPP afforded the corresponding saturated carboxylic acids after hydrolysis with 1M HCl. Treatment of the reaction mixture with alcohols or amines instead of 1M HCl gave the corresponding saturated esters and amides, respectively. As a result of studies of the reaction mechanism, it was revealed that the reaction proceeded via silylcyanation of α,β-unsaturated aldehydes with trimethylsilyl cyanide to produce trimethylsilyl ethers of cyanohydrin and subsequent isomerization that formed α-trimethylsiloxy vinyl cyanides, which were hydrolyzed to give saturated carboxylic acids. Copyright Taylor & Francis Group, LLC.
- Hayashi, Masahiko,Kawabata, Hirotoshi,Yoshimoto, Kazuya,Tanaka, Takanori
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- Trimethylphosphine-Promoted Alcoholysis of α,β-Unsaturated Imides and α,β-Unsaturated Esters
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α,β-Unsaturated imides and α,β-unsaturated esters were found to undergo alcoholysis in the presence of trimethylphosphine. The reaction is initiated by nucleophilic addition of trimethylphosphine to the double bond of the α,β-unsaturated carbonyl compound. Saturated imides also undergo the alcoholysis in the presence of the corresponding α,β-unsaturated imide.
- Sato, Haruka,Hosokawa, Seijiro
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- A High Mobility Reactor Unit for R&D Continuous Flow Transfer Hydrogenations
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A suitcase sized mobile reactor unit (MRU) weighing in at less than 10 kg was designed for laboratory scale transfer hydrogenations in continuous flow. Simple cyclohexene and a cosolvent in combination with a palladium-on-charcoal packed bed reactor provided a setup with isolation of nearly all products without the need for further purification. Several functional groups including olefins, triple bonds, nitro-groups, carbonyls, and so forth were effectively reduced with retention times as low as 2 min. Additionally, standard protection groups such as Cbz, benzyl, and allyl ether or esters were removed in high yields. To prove the flexibility of the setup an example of the Mizoroki-Heck reaction was also performed on the MRU. Finally, two scale-up transfer hydrogenation experiments were performed affording isolation of the desired target compounds in 0.5 and 0.8 mol scales with less than 4 h of continuous operation on the MRU.
- Jensen, Rasmus K.,Thykier, Nikolaj,Enevoldsen, Martin V.,Lindhardt, Anders T.
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- Highly efficient and chemoselective transfer hydrogenation of nitroarenes at room temperature over magnetically separable Fe-Ni bimetallic nanoparticles
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A highly chemoselective catalytic transfer hydrogenation (CTH) of nitroarenes to corresponding amino derivatives is achieved with Fe-Ni bimetallic nanoparticles (Fe-Ni NP's) as the catalyst and NaBH4 at room temperature. Their catalytic efficiency is ascribed to the presence of Ni sites on the bimetallic surface that not only hinder the surface corrosion of the iron sites but also facilitate efficient electron flow from the catalyst surface to the adsorbed nitro compounds. This facet is corroborated with reusability studies as well as surface characterization of the catalyst before and after its repetitive usage. Thus, these nanoparticles efficiently catalyze the reduction of functionalized nitroarenes to corresponding amines without use of corrosive agents like base or other additives under ambient conditions and are easily separated by a laboratory magnet in an eco-friendly manner.
- Petkar, Dhananjay R.,Kadu, Brijesh S.,Chikate, Rajeev C.
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- Porous organic polymer-supported palladium catalyst for hydroesterification of olefins
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Hydroesterification of olefins with alcohols and CO is an attractive approach to synthesize value-added carboxylic esters. The current manufactures are mainly based on the use of homogeneous catalytic systems, and developing a heterogeneous process enabling cost-effective catalyst separation is of potential interest, particularly for higher olefins. In this contribution, we reported a robust porous organic polymer-supported palladium catalyst that exhibited excellent hydroesterification performance approaching that of the homogeneous counterpart. In addition, the catalyst shows remarkable adaptability for a broad range of substrates (both olefins and alcohols) and recyclability. The catalysts are thoroughly characterized by a spectrum of characterization techniques including N2 sorption, SEM, TEM, HAADF-STEM coupled with elemental mapping, FTIR with CO probe, XPS, and solid-state 31P NMR. Based on these, the good catalytic performance can be attributed to the high surface area, highly dispersed active metal species, and the strong coordination bonds between palladium center and the exposed phosphorous ligands in Porous organic polymer (POPs) frame. The ICP-OES and hot filtration test further indicate that the reaction truly proceeds in a heterogeneous manner, thus exhibiting great potential for industrial applications.
- Chen, Meng,Chen, Miaomiao,Chen, Xingkun,Ding, Yunjie,Huang, Chuanqi,Lin, Ronghe,Mou, Xiaoling,Tan, Yuan,Wang, Saisai,Yang, Wenshao,Zhao, Ziang
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- Microwave-accelerated O-alkylation of carboxylic acids with O-alkylisoureas
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(equation presented) Microwave-assisted O-alkylations of several carboxylic acids have been performed with three different O-alkylisoureas. All reactions are significantly faster compared to conventionally heated reactions, while retaining high chemoselec
- Crosignani, Stefano,White, Peter D.,Linclau, Bruno
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- Green semi-hydrogenation of alkynes by Pd@borate monolith catalysts under continuous flow
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Palladium nanoparticles were immobilized onto an unconventional polymeric borate macroporous monolith and the resulting mesoreactor (i.d. 3 mm, length 25 mm) used in liquid-phase catalytic semi-hydrogenation reaction of substituted alkynes under continuous flow. The catalytic system showed excellent efficiency, both in terms of activity and selectivity, and long-term stability under mild reaction conditions (methanol, room temperature, 1.5 bar H2 max), with no need of additives. Particularly, the leaf alcohol cis-3-hexen-1-ol was for the first time obtained with selectivity comparable to that of the industrial batch process. The performance of the catalyst is discussed and compared with those of the analogous batch and industrial processes.
- Liguori, Francesca,Barbaro, Pierluigi
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- Reductive deamination of α-amino carbonyl compounds by means of samarium iodide
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Reaction of α-amino carbonyl compounds with SmI2 in THF-HMPA in the presence of a proton source afforded the deamination products, where the fragmentation occurred between the nitrogen and the carbon α to the carbonyl group.
- Honda, Toshio,Ishikawa, Fumihiro
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- Ambulation of Incipient Proton during Gas-Phase Dissociation of Protonated Alkyl Dihydrocinnamates
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Upon activation in the gas phase, protonated alkyl dihydrocinnamates undergo an alcohol loss. However, the mechanism followed is not a simple removal of an alkanol molecule after a protonation on the alkoxy group. The mass spectrum of the m/z 166 ion for deuteron-charged methyl dihydrocinnamate showed two peaks of 1:5 intensity ratio at m/z 133 and 134 to confirm that the incipient proton is mobile. The proton initially attached to the carbonyl group migrates to the ring and randomizes before a subsequent transfer of one of the ring protons to the alkoxy group for the concomitant alcohol elimination. Moreover, protonated methyl dihydrocinnamate undergoes more than one H/D exchange. The spectra recorded from m/z 167 and 168 ions obtained for di- and tri-deuterio isotopologues showed peak pairs at m/z 134, 135 and 135, 136, at 1:2 and 1:1 intensity ratios, respectively, confirming the benzenium ion intermediate achieves complete randomization before the proton transfer. Additionally, protonated higher esters of alkyl dihydrocinnamates undergo a cleavage of the O-CH2 bond to form an ion/neutral complex, which, upon activation, dissociates generating a carbenium ion and dihydrocinnamic acid, or rearranges to generate protonated dihydrocinnamic acid and an alkene by a nonspecific proton transfer.
- Xu, Sihang,Zhang, Yong,Errabelli, Ramu,Attygalle, Athula B.
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- Hydrogenation of Ketones and Esters Catalyzed by Pd/C?SiO2
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Hydrogenation of unsaturated ketones and esters with molecular hydrogen on the 5%Pd/C?SiO2 heterogeneous catalyst has been studied. The reaction direction and yield are determined by the starting compounds structure. Hydrogenation of unsaturated ketones containing phenyl group at the double carbon–carbon atom is accompanied by the reduction of the ketone group into the alcohol one. Hydrogenation of unsaturated esters is accompanied by transesterification.
- Akchurin,Baibulatov,Dokichev
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- Highly regioselective palladium-catalyzed methoxycarbonylation of styrene using chiral ferrocene- and biphosphole-based ligands
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The methoxycarbonylation of styrene has been studied using Pd(OAc)2/L/acid catalytic systems with L being chiral ferrocene- and biphosphole-based ligands. Good activities are obtained in mild conditions. Chemoselectivities and regioselectivitie
- Diab, Lisa,Gouygou, Maryse,Manoury, Eric,Kalck, Philippe,Urrutigo?ty, Martine
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- Highly efficient solvent-free catalytic hydrogenation of solid alkenes and nitro-aromatics using Pd nanoparticles entrapped in aluminum oxy-hydroxide
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Solid alkenes and aromatic nitro compounds are readily hydrogenated to the corresponding alkanes without further reduction of other functional group and amino compounds in nearly quantitative yields in the presence of Pd nanoparticles entrapped in aluminum oxy-hydroxide under the solvent-free condition.
- Chang, Fei,Kim, Hakwon,Lee, Byeongno,Park, Sungho,Park, Jaiwook
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- A fluorous super br?nsted acid catalyst: Application to fluorous catalysis without fluorous solvents
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The preparation of a fluorous super Br?nsted acid catalyst, 4-(1H,1H-perfluorotetradecanoxy)-2,3,5,6-tetrafluorophenylbis (trifluoromethanesulfonyl)methane (3d), is described. The fluorous catalyst 3d can be recycled by using liquid/solid phase separation without fluorous solvents. A perfluorocarbon solvent is not essential for fluorous biphasic catalysis.
- Ishihara, Kazuaki,Hasegawa, Aiko,Yamamoto, Hisashi
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- Palladium nanoparticles supported on magnetic carbon-coated cobalt nanobeads: Highly active and recyclable catalysts for alkene hydrogenation
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Palladium nanoparticles are deposited on the surface of highly magnetic carbon-coated cobalt nanoparticles. In contrast to the established synthesis of Pd nanoparticles via reduction of Pd(II) precursors, the microwave decomposition of a Pd(0) source leads to a more efficient Pd deposition, resulting in a material with considerably higher activity in the hydrogenation of alkenes. Systematic variation of the Pd loading on the carbon-coated cobalt nanoparticle surface reveals a distinct trend to higher activities with decreased loading of Pd. The activity of the catalyst is further improved by the addition of 10 vol% Et2O to iso-propanol that is found to be the solvent of choice. With respect to activity (turnover frequencies up to 11 095 h-1), handling, recyclability through magnetic decantation, and leaching of Pd (≤6 ppm/cycle), this novel magnetic hybrid material compares favorably to conventional Pd/C or Pd@CNT catalysts.
- Kainz, Quirin M.,Linhardt, Roland,Grass, Robert N.,Vile, Gianvito,Perez-Ramirez, Javier,Stark, Wendelin J.,Reiser, Oliver
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- Palladium nanoparticles supported onto ionic carbon nanotubes as robust recyclable catalysts in an ionic liquid
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Palladium nanoparticles have been deposited onto imidazolium bromide-functionalized ionic MWCNTs through hydrogen reduction of Na 2PdCl4 in water without aid of surfactants under extremely mild conditions, and combined with an ionic liquid to create a new recyclable ionic liquid-based catalytic system allowing up to 50 times recycling. The Royal Society of Chemistry.
- Chun, Yu Sung,Shin, Ju Yeon,Song, Choong Eui,Lee, Sang-Gi
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- Synthesis and computer-aided analysis of the role of linker for novel ligands of the 5-HT6 serotonin receptor among substituted 1,3,5-triazinylpiperazines
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A series of 2-amino-4-(4-methylpiperazin-1-yl)-1,3,5-triazines was designed based on previously published 2-amino-4-benzyl-(4-methylpiperazin-1-yl)-1,3,5-triazines in order to evaluate the role of a linker between the triazine moiety and an aromatic substituent for the human serotonin 5-HT6 receptor affinity. As new linkers two carbon atoms (ethyl or ethenyl) or an oxyalkyl chain (methoxy, 2-ethoxy, 2-propoxy) were introduced. Affinities of the compounds for the 5-HT6R as the main target, and for the 5-HT1AR, 5-HT7R and D2R as competitive ones, were determined in the radioligand binding assays. Docking to the 5-HT6R homology model was performed to support SAR analysis. Results showed that the branching of the methoxyl linker increased affinity for the human 5-HT6R whereas an unsaturated bond within the linker dramatically reduced desirable activity. Both experimental and theoretical studies confirmed the previously postulated beneficial role of the aromatic size for interaction with the 5-HT6R. Thus, the largest naphthyl moiety yielded the highest activity. In particular, 4-(4-methylpiperazin-1-yl)-6-(1-(naphthalen-1-yloxy)ethyl)-1,3,5-triazin-2-amine (24), the most potent 5-HT6R agent found (Ki = 23 nM), can be a new lead structure for further search and development.
- ?a?ewska, Dorota,Kurczab, Rafa?,Wi?cek, Ma?gorzata,Sata?a, Grzegorz,Kie?-Kononowicz, Katarzyna,Handzlik, Jadwiga
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- Lewis Acids as Highly Efficient Catalysts for the Decarboxylative Esterification of Carboxylic Acids with Dialkyl Dicarbonates
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Mild Lewis acids such as Mg(ClO4)2 show a new level of catalytic activity for the decarboxylative esterification of carboxylic acids with commercially available dialkyl dicarbonates. In the presence of as little as one mol % Mg(ClO4)2 catalyst, carboxylic acids can thus easily and near quantitatively be protected at room temperature, e.g., as methyl, benzyl, or t-butyl esters. Only volatile by-products are released so that the purification of the products is particularly easy. Many sensitive functionalities are tolerated, including even phenol esters, or free hydroxy and BOC groups.
- Goossen,Doehring
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- Tandem oxidation of allylic and benzylic alcohols to esters catalyzed by N-heterocyclic carbenes
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(Chemical Equation Presented) N-Heterocyclic carbenes catalyze the oxidation of allylic, propargylic, and benzylic alcohols to esters with manganese(IV) oxide in excellent yields. A variety of ester derivatives can be synthesized, including protected carboxylates. This one-pot tandem oxidation represents the first organocatalytic oxidation of alcohols to esters. Saturated esters can also be accessed from aldehydes using this method. Through the utilization of a chiral catalyst, the acyl-heteroazolium intermediate becomes a chiral acylating agent, which can desymmetrize meso-1,2-diols.
- Maki, Brooks E.,Chan, Audrey,Phillips, Eric M.,Scheidt, Karl A.
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- Being two is better than one - Catalytic reductions with dendrimer encapsulated copper - And copper-cobalt-subnanoparticles
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Copper and copper-cobalt subnanoparticles have been synthesized using 4-carbomethoxypyrrolidone terminated PAMAM-dendrimers as templates. The metal particles were applied in catalytic reduction reactions. While Cu subnanoparticles were only capable of reducing conjugated double bonds, enhancing the Cu particles with Co led to a surprising increase in catalytic activity, reducing also isolated carbon double and triple bonds.
- Ficker, Mario,Petersen, Johannes F.,Gschneidtner, Tina,Rasmussen, Ann-Louise,Purdy, Trevor,Hansen, Jon S.,Hansen, Thomas H.,Husted, S?ren,Moth Poulsen, Kasper,Olsson, Eva,Christensen, J?rn B.
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- Conversion of α-haloaldehydes into acylating agents by an internal redox reaction catalyzed by nucleophilic carbenes
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Reactivity umpolung allows us to consider nontraditional bond disconnections. We report herein that treatment of an α-haloaldehyde with a nucleophile in the presence of catalytic amounts of nucleophilic carbenes results in an internal redox reaction giving rise to a dehalogenated acylating agent as an intermediate by a new reaction manifold. A brief illustration of the scope of this reaction is presented along with evidence supporting the direct intervention of the carbene in the acylation step. Copyright
- Reynolds, Nathan T.,De Alaniz, Javier Read,Rovis, Tomislav
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- Pd-catalysed methoxycarbonylation of vinylarenes using chiral monodentate phosphetanes and phospholane as ligands. Effect of substrate substituents on enantioselectivity
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Palladium complexes bearing phospholane 1 and phosphetane 2-4 ligands have been synthesised to be used as catalyst precursors in the asymmetric methoxycarbonylation of vinyl arenes. Single crystals of the complex [PdCl 2(2)2] II were obtained from a toluene solution and analysed by X-ray crystallography. Using these complexes, excellent regioselectivity (up to 99%) to the branched esters was obtained. Phosphetane ligands provide higher enantioselectivity than the phospholane under the same reaction conditions and an important influence of the substrate was observed. Enantioselectivity up to 50% was obtained using 4-methoxystyrene. The Royal Society of Chemistry.
- Munoz, Bianca K.,Godard, Cyril,Marinetti, Angela,Ruiz, Aurora,Benet-Buchholz, Jordi,Claver, Carmen
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- Solvolysis of formylphenyl esters by a bifunctional peptide catalyst
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An artificial hydrolytic system using a formylphenyl ester and a bifunctional peptide catalyst was developed. Controlling the spatial positions of the two functional groups, the amino group of proline and the imidazole of histidine in the peptide, was important for the reaction efficiency of hydrolysis. The application of this system to kinetic resolution was shown to be plausible.
- Akagawa, Kengo,Kudo, Kazuaki
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- Aerobic oxidative esterification of primary alcohols over Pd-Au bimetallic catalysts supported on mesoporous silica nanoparticles
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We have prepared a series of mesoporous silica nanoparticle (MSN) supported Pd-Au bimetallic catalysts using a newly developed sequential impregnation method. These catalysts were fully characterized by various techniques including nitrogen sorption, powder X-ray diffraction, inductively coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy (TEM) and high angle annular dark-field scanning transmission electron microscopy (HADDF-STEM). By using this synthetic approach, we observed metal nanoparticles (NP) with diameters of 1–2 nm homogeneously supported on the MSN. The catalytic performance of these MSN supported metal NPs was tested by aerobic oxidative esterification in a tandem reaction where primary alcohols are oxidized to their corresponding aldehydes and to esters in a subsequent reaction. We determined that Pd NPs are very efficient in the first step of oxidation; however, stagnant in the subsequent oxidation. On the contrary, Au NPs show slow reactivity in converting alcohols to aldehydes, but extraordinarily efficient in the oxidation of aldehydes to esters. By fine tuning the metal ratio, the bimetallic catalyst exhibits better reactivity and selectivity toward a variety of primary alcohols than the corresponding monometallic catalysts. In addition, we also found that the bimetallic Pd-Au@MSN catalysts can be recycled three times without a significant loss in activity.
- Tsai, Chih-Hsiang,Xu, Mengze,Kunal, Pranaw,Trewyn, Brian G.
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- Silicon Carbide Supported Palladium-Iridium Bimetallic Catalysts for Efficient Selective Hydrogenation of Cinnamaldehyde
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Selective hydrogenation of α,β-unsaturated carbonyls into saturated carbonyls is important to obtain remunerative products. However, it is still a challenge to achieve high activity and selectivity under mild conditions. Herein, Pd, Ir and bimetallic Pd-Ir nanoparticles were uniformly deposited with high dispersity on the surface of SiC by a facile impregnation method, respectively. The as-prepared Pd/SiC catalysts efficiently hydrogenate cinnamaldehyde to hydrocinnamaldehyde at room temperature and atmospheric pressure, and the activity of Pd/SiC is observed further enhanced by adding Ir component (conversion of 100%). In addition, the dependence of Pd-Ir catalyst activity on Pd/Ir molar ratio confirms a synergistic effect between Ir and Pd, which originates from the electron transfer between Pd and Ir.
- Guo, Xiang-Yun,Jin, Guoqiang,Li, Penghui,Tong, Xili,Wang, Yingyong,Wang, Yunwei
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- Platinum nanoparticles supported on ionic liquid-modified magnetic nanoparticles: Selective hydrogenation catalysts
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A method for supporting platinum nanoparticles on magnetite nanoparticles is described. The method requires modification of the surface of the magnetic nanoparticles with ionic liquid groups. Before modification, the magnetic nanoparticles are not stable and easily aggregate and, after modification, the magnetite nanoparticles become highly stable and soluble in polar or non-polar organic solvents depending on the alkyl group of the linked ionic liquids. The supporting of platinum nanoparticles on the modified magnetic nanoparticles was achieved by adsorbing platinum salts (K2PtCl4) on the surface of the magnetite nanoparticles via ion exchange with the linked ionic liquid groups and then reducing them by hydrazine. The supported platinum nanoparticles were applied in the catalytic hydrogenation of alkynes in which cis-alkenes were selectively produced, and in the hydrogenation of α,β-unsaturated aldehydes where the allyl alcohols were obtained as the exclusive products. The new catalyst can be easily separated from the reaction mixtures by applying an external magnetic field and recycled.
- Abu-Reziq, Raed,Wang, Dashan,Post, Michael,Alper, Howard
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- Palladium-catalyzed reaction of some triphenylbismuth(V) sulfonates and phenolates with methyl acrylate
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Triphenylbismuth(V) derivatives Ph3BiX2 [X = OC 6H2(NO2)3-2,4,6, OC 6H2(NO2-4)Br2-2,6, OTs, OSO 2C6H4OH-4] react with methyl acrylate and PdCl2 (1:3:0.04 molar ratio) in acetonitrile at 20°C to form the cross-coupling products, methyl cinnamate (0.26-0.51 mol mol-1 starting bismuth compound) and methyl hydrocinnamate (0-0.17 mol mol -1); diphenyl, the homocoupling product (0-0.13 mol mol -1); and benzene (0.02-0.15 mol mol-1). The reaction of Ph3Bi(OSO2C6H4OH-4)2 is characterized by the selective formation of methyl cinnamate, but the reagent activity is low. Ph3Bi(OTs)2 exhibits the highest activity among the derivatives studied, but the reaction selectivity is low. The mechanisms of the palladium-catalyzed formation of homo-and cross-coupling products are proposed. Nauka/Interperiodica 2006.
- Gushchin,Malysheva,Kosov,Sharutin
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- Hydrogenation and Deuteration with the System Zn-NiCl2 in Aqueous Medium: Stirring and Ultrasonic Improvement Procedures
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The system Zn-NiCl2-H2O is used for conjugate reduction of methyl cinnamate under stirring and ultrasonic irradiation.It appears that in both cases the three steps metallic nickel formation on the zinc surface, hydrogen gas formation by nickel-assisted zinc reduction of water, and catalytic olefin reduction with molecular hydrogen on the nickel-activated zinc surface constitute the main reaction pathways.Deuteration of the substrate is achieved by substitution of deuterium oxide for water, and better results are observed in the stirred reaction.Scanning electronmicrographs of the catalyst show that ultrasonic irradiation has cleaned the surface of the particles.
- Petrier, Christian,Luche, Jean-Louis,Lavaitte, Stephane,Morat, Claude
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- Diversion of the Arbuzov reaction: Alkylation of C-Cl instead of phosphonic ester formation on the fullerene cage
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We report an "inversed" Arbuzov reaction of the fullerene derivatives C60Ar5Cl with trialkyl phosphites P(OR)3 producing alkylated fullerene derivatives C60Ar5R (R = Me, Et, iPr, nBu) with almost quantitative yields. This reaction provides a convenient synthetic route for the preparation of a large variety of functionalized fullerene derivatives with tailored properties, e.g. water-soluble compounds demonstrating promising antiviral activities against HCMV, HSV1, HIV and several influenza virus strains.
- Kraevaya, Ol'Ga A.,Peregudov, Alexander S.,Troyanov, Sergey I.,Godovikov, Ivan,Fedorova, Natalya E.,Klimova, Regina R.,Sergeeva, Vasilina A.,Kameneva, Larisa V.,Ershova, Elizaveta S.,Martynenko, Vyacheslav M.,Claes, Sandra,Kushch, Alla A.,Kostyuk, Svetlana V.,Schols, Dominique,Shestakov, Alexander F.,Troshin, Pavel A.
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- NHC-catalysed aerobic aldehyde-esterifications with alcohols: No additives or cocatalysts required
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A highly efficient, broad scope, additive-free mild protocol for the oxidative carbene-catalysed esterification of aldehydes (including the related aqueous oxidation to acids) has been developed.
- Delany, Eoghan G.,Fagan, Claire-Louise,Gundala, Sivaji,Mari, Alessandra,Broja, Thomas,Zeitler, Kirsten,Connon, Stephen J.
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- Hydroesterification of Vinylarenes Catalyzed by Palladium Complexes of Dialkylmonoaryl- and Monoalkyldiarylphosphines
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Hydroesterification of vinylarenes using a mixture of PdCl2 and monodentate phosphorus ligands as a catalyst was studied. As ligands, menthyldiphenylphosphine (MDPP), neomenthyldiphenylphosphine (NMDPP), and dicyclohexyl(phenyl)phosphine (Cy2PPh) were effective to obtain branched esters with high regioselectivity under the moderate reaction conditions without additives such as acids. Not only electronic effects but also steric effects of the cycloalkyl groups were revealed to be significant in order to achieve high catalytic activity. When (S)-2-dicyclopentylphosphino-2′-methoxy-1,1′-binaphthyl was used for the asymmetric hydroesterification of 2-methoxy-6-vinylnaphthalene, (S)-naproxen methyl ester was obtained with 53% ee.
- Kawashima, Yasutoyo,Okano, Kentaro,Nozaki, Kyoko,Hiyama, Tamejiro
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- Catalytic Hydrogenation of Olefins and Acetylenes over C60Pdn
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Organopalladium polymers of buckminsterfullerene, C60Pdn, catalyze hydrogenation of olefins and acetylenes at room temperature under a hydrogen atmosphere.The catalytic activity is mainly dependent on the ratio of C60 to Pd in the polymers.Partial hydrogenation of acetylenes is achieved by adding benzylamine as the cocatalyst.
- Nagashima, Hideo,Nakaoka, Akihito,Tajima, Syuji,Saito, Yahachi,Itoh, Kenji
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- A simple and straightforward approach toward selective C=C bond reduction by hydrazine
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A simple and straightforward method for reducing the C=C double bond with hydrazine is described. A number of representative C=C bonds in various steric and electronic environments were examined. Substituted alkenes can be selectively reduced in EtOH in the presence of hydrazine to give the corresponding products in up to 100% yields.
- Chen, Hao,Wang, Jianmin,Hong, Xuechuan,Zhou, Hai-Bing,Dong, Chune
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- Chemoselectivity of tetrabutylammonium borohydride towards bifunctional esters
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Chemoselective reduction of functional groups in the presence of esters is observed with tetrabutylammonium borohydride in chloro solvents.
- Narasimhan,Swarnalakshmi,Balakumar,Velmathi
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- Mild and catalytic transesterification reaction using K2HPO 4 for the synthesis of methyl esters
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K2HPO4 is an efficient catalyst for the transesterification reaction to produce methyl esters. Various functional groups are compatible under the mild reaction conditions. Georg Thieme Verlag Stuttgart New York.
- Shinada, Tetsuro,Hamada, Makoto,Miyoshi, Kota,Higashino, Masato,Umezawa, Taiki,Ohfune, Yasufumi
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- Systematic study of the asymmetric methoxycarbonylation of styrene catalyzed by palladium systems containing chiral ferrocenyl diphosphine ligands
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We present the first systematic study of the Pd-catalyzed asymmetric methoxycarbonylation of styrene in the presence of chiral ferrocenyl phosphine ligands. The reaction conditions were optimized, and a screening of different catalyst precursors was performed. A number of 1,1′-bis(phosphino) ferrocenes of the Mandyphos, Josiphos, Walphos, and Taniaphos types were tested in combination with [PdCl2(NCPh)2], in the presence of TsOH as the acid source. These systems afforded high enantioselectivities, although the regioselectivity of the reaction was found to be in favor of the (undesired) linear ester. The catalytic system made with the Josiphos ligand 1 gave rise to an enantiomeric excess (ee) of 86%.
- Godard, Cyril,Ruiz, Aurora,Claver, Carmen
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- Remarkable effect of bimetallic nanocluster catalysts for aerobic oxidation of alcohols: Combining metals changes the activities and the reaction pathways to aldehydes/carboxylic acids or esters
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Selective oxidation of alcohols catalyzed by novel carbon-stabilized polymer-incarcerated bimetallic nanocluster catalysts using molecular oxygen has been developed. The reactivity and the selectivity were strongly dependent on the combination of metals and solvent systems; aldehydes and ketones were obtained by the gold/platinum catalyst in benzotrifluoride, and esters were formed by the gold/palladium catalyst in methanol. To the best of our knowledge, this is the first example that the reaction pathway has been changed dramatically in gold catalysis by combining with a second metal. The differences in the activity and the selectivity are considered to be derived from the difference in the structure of the bimetallic clusters.
- Kaizuka, Kosuke,Miyamura, Hiroyuki,Kobayashi, Shu
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- PtII-catalyzed hydrophenylation of α-olefins: Variation of linear/branched products as a function of ligand donor ability
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The PtII complexes [(xbpy)Pt(Ph)(THF)]+ (xbpy = 4,4′-X2-2,2′-bipyridyl; x = OMe (1a), tBu (1b), H (1c), Br (1d), CO2Et (1e) and NO2 (1f)] catalyze the formation of n-propylbenzene and cumene from benzene and propene. The catalysts are selective for branched products, and the cumene/n-propylbenzene ratio decreases with increasing donor ability of the xbpy ligand. DFT(D) calculations predict more favorable activation barriers for 1,2-insertion into the Pt-Ph bond to give branched products. The calculations indicate that 1,2-insertion of propene should be faster than 2,1-insertion for all Pt(II) catalysts studied, but they also indicate that cumene/n-propylbenzene selectivity is under Curtin-Hammett control.
- McKeown, Bradley A.,Prince, Bruce M.,Ramiro, Zoraida,Gunnoe, T. Brent,Cundari, Thomas R.
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- Chemoselective reduction of α,β-unsaturated carbonyl compounds in the presence of CuPd alloy nanoparticles decorated on mesoporous graphitic carbon nitride as highly efficient catalyst
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Herein, we reported reductions of acid, amide, ester and ketone groups with selectivity (>99%) by the catalytic transfer hydrogenation of with CuPd alloy nanoparticles (NPs) decorated on mesoporous graphitic carbon nitride (Cu50Pd50/mpg-C3N4) catalyst under mild conditions in a water/methanol mixture. CuPd alloy NPs were synthesized by the co-reduction of palladium (II) acetylacetonate and copper(II) acetylacetonate in oleylamine (OAm) solution by the reduction of morpholine-borane solution and then assembled on mpg-C3N4 via liquid phase self‐assembly method. The α, β-unsaturated carbonyl compounds were obtained from the condensation reaction of the benzaldehyde derivatives with acetone derivatives. Cu50Pd50/mpg-C3N4 nanocatalyst was characterized by TEM, XRD, XPS, BET and ICP‐MS. Cu50Pd50/mpg-C3N4 nanocatalyst is highly active catalyst for the reduction of various organic groups and converted to high yield and 99% selectivity. The superior Cu50Pd50/mpg-C3N4 nanocatalyst is highly efficient and reusable catalyst which is reuse after 5 cycle with 98% conversion.
- Bayrak, Cetin,Menzek, Abdullah,Sevim, Melike
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- Enantioselective Flow Synthesis of Rolipram Enabled by a Telescoped Asymmetric Conjugate Addition-Oxidative Aldehyde Esterification Sequence Using in Situ-Generated Persulfuric Acid as Oxidant
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A novel approach is reported for the enantioselective flow synthesis of rolipram comprising a telescoped asymmetric conjugate addition-oxidative aldehyde esterification sequence followed by trichlorosilane-mediated nitro group reduction and concomitant la
- Nagy, Bence S.,Llanes, Patricia,Pericas, Miquel A.,Kappe, C. Oliver,?tv?s, Sándor B.
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supporting information
(2022/02/05)
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- Esterification or Thioesterification of Carboxylic Acids with Alcohols or Thiols Using Amphipathic Monolith-SO3H Resin
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We have developed a method for the esterification of carboxylic acids with alcohols using amphipathic, monolithic-resin bearing sulfonic acid moieties as cation exchange functions (monolith-SO3H). Monolith-SO3H efficiently catalyzed the esterification of aromatic and aliphatic carboxylic acids with various primary and secondary alcohols (1.55.0 equiv) in toluene at 6080 °C without the need to remove water generated during the reaction. The amphipathic property of monolith-SO3H facilitates dehydration due to its capacity for water absorption. This reaction was also applicable to thioesterification, wherein the corresponding thioesters were obtained in excellent yield using only 2.0 equiv of thiol in toluene, although heating at 120 °C was required. Moreover, monolith-SO3H was separable from the reaction mixtures by simple filtration and reused for at least five runs without decreasing the catalytic activity.
- Ichihara, Shuta,Ishida, Moeka,Ito, Ryo,Kato, Ayumu,Monguchi, Yasunari,Nakamura, Shinji,Park, Kwihwan,Sajiki, Hironao,Takada, Hitoshi,Wakayama, Fumika,Yamada, Tsuyoshi,Yamada, Yutaro
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p. 2702 - 2710
(2022/01/19)
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- GPR52 Antagonist Reduces Huntingtin Levels and Ameliorates Huntington's Disease-Related Phenotypes
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GPR52 is an orphan G protein-coupled receptor (GPCR) that has been recently implicated as a potential drug target of Huntington's disease (HD), an incurable monogenic neurodegenerative disorder. In this research, we found that striatal knockdown of GPR52 reduces mHTT levels in adult HdhQ140 mice, validating GPR52 as an HD target. In addition, we discovered a highly potent and specific GPR52 antagonist Comp-43 with an IC50 value of 0.63 μM by a structure-activity relationship (SAR) study. Further studies showed that Comp-43 reduces mHTT levels by targeting GPR52 and promotes survival of mouse primary striatal neurons. Moreover, in vivo study showed that Comp-43 not only reduces mHTT levels but also rescues HD-related phenotypes in HdhQ140 mice. Taken together, our study confirms that inhibition of GPR52 is a promising strategy for HD therapy, and the GPR52 antagonist Comp-43 might serve as a lead compound for further investigation.
- Wang, Congcong,Zhang, Yu-Fang,Guo, Shimeng,Zhao, Quan,Zeng, Yanping,Xie, Zhicheng,Xie, Xin,Lu, Boxun,Hu, Youhong
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p. 941 - 957
(2020/11/30)
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- PCl3-mediated transesterification and aminolysis of tert-butyl esters via acid chloride formation
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A PCl3-mediated conversion of tert-butyl esters into esters and amides in one-pot under air is developed. This novel protocol is highlighted by the synthesis of skeletons of bioactive molecules and gram-scale reactions. Mechanistic studies revealed that this transformation involves the formation of an acid chloride in situ, which is followed by reactions with alcohols or amines to afford the desired products.
- Wu, Xiaofang,Zhou, Lei,Li, Fangshao,Xiao, Jing
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p. 491 - 497
(2021/01/20)
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- Oxidative esterification of alcohols by a single-side organically decorated Anderson-type chrome-based catalyst
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The direct esterification of alcohols with non-noble metal-based catalytic systems faces great challenges. Here, we report a new chrome-based catalyst stabilized by a single pentaerythritol decorated Anderson-type polyoxometalate, [N(C4H9)4]3[CrMo6O18(OH)3C{(OCH2)3CH2OH}], which can realize the efficient transformation from alcohols to esters by H2O2oxidation in good yields and high selectivity without extra organic ligands. A variety of alcohols with different functionalities including some natural products and pharmaceutical intermediates are tolerated in this system. The chrome-based catalyst can be recycled several times and still keep the original configuration and catalytic activity. We also propose a reasonable catalytic mechanism and prove the potential for industrial applications.
- Wang, Jingjing,Jiang, Feng,Tao, Chaofu,Yu, Han,Ruhlmann, Laurent,Wei, Yongge
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supporting information
p. 2652 - 2657
(2021/04/21)
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- Direct Deamination of Primary Amines via Isodiazene Intermediates
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We report here a reaction that selectively deaminates primary amines and anilines under mild conditions and with remarkable functional group tolerance including a range of pharmaceutical compounds, amino acids, amino sugars, and natural products. An anomeric amide reagent is uniquely capable of facilitating the reaction through the intermediacy of an unprecedented monosubstituted isodiazene intermediate. In addition to dramatically simplifying deamination compared to existing protocols, our approach enables strategic applications of iminium and amine-directed chemistries as traceless methods. Mechanistic and computational studies support the intermedicacy of a primary isodiazene which exhibits an unexpected divergence from previously studied secondary isodiazenes, leading to cage-escaping, free radical species that engage in a chain, hydrogen-atom transfer process involving aliphatic and diazenyl radical intermediates.
- Berger, Kathleen J.,Driscoll, Julia L.,Yuan, Mingbin,Dherange, Balu D.,Gutierrez, Osvaldo,Levin, Mark D.
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supporting information
p. 17366 - 17373
(2021/11/04)
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- Structural elucidation of chiral (imino)pyridine/phosphine palladium(II) complexes and their applications as catalysts in methoxycarbonylation of styrene
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Treatment of ligands (S)-1-phenyl-N-(1-(pyridin-2-yl)ethylidene)ethanamine (L1), (R)-1-phenyl-N-(1-(pyridin-2-yl)ethylidene)ethanamine (L2), (S)-1-phenyl-N-((pyridin-2-yl)methylene)ethanamine (L3), (R)-1-phenyl-N-((pyridin-2-yl)methylene)ethanamine (L4), (S)-N-(2-(diphenylphosphino)benzylidene)-1-phenylethanamine (L5), and (R)-N-(2-(diphenylphosphino)benzylidene)-1-phenylethanamine (L6) with [Pd(COD)Cl2] afforded the respective palladium complexes [Pd(L1)Cl2] (1), [Pd(L2)Cl2] (2), [Pd(L3)Cl2] (3), [Pd(L4)Cl2] (4), [Pd(L5)Cl2] (5) and [Pd(L6)Cl2] (6) in high yields. Solid-state structures of the complexes established N^N and N^P bidentate coordination mode of the ligands to give distorted square planar geometries. Complexes 1–6 displayed moderate catalytic activities in the methoxycarbonylation of styrene, to give predominantly branched esters of up to 95%. NMR spectroscopy studies pointed to possible decomposition of the active species, via ligand dissociation.
- Akiri, Saphan O.,Ngcobo, Nondumiso L.,Ogweno, Aloice O.,Ojwach, Stephen O.
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- Sterically hindered (pyridyl)benzamidine palladium(II) complexes: Syntheses, structural studies, and applications as catalysts in the methoxycarbonylation of olefins
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Reactions of ligands (E)-N′-(2,6-diisopropylphenyl)-N-(4-methylpyridin-2-yl)benzimidamide (L1), (E)-N′-(2,6-diisopropylphenyl)-N-(6-methylpyridin-2-yl)benzimidamide (L2), (E)-N′-(2,6-dimethylphenyl)-N-(6-methylpyridin-2-yl)benzimidamide (L3), (E)-N′-(2,6-dimethylphenyl)-N-(4-methylpyridin-2-yl)benzimidamide (L4), and (E)-N-(6-methylpyridin-2-yl)-N′-phenylbenzimidamide (L5) with [Pd(NCMe)2Cl2] furnished the corresponding palladium(II) precatalysts (Pd1–Pd5), in good yields. Molecular structures of Pd2 and Pd3 revealed that the ligands coordinate in a N^N bidentate mode to afford square planar compounds. Activation of the palladium(II) complexes with para-tolyl sulfonic acid (PTSA) afforded active catalysts in the methoxycarbonylation of a number of alkene. The resultant catalytic activities were controlled by the both the complex structure and alkene substrate. While aliphatic substrates favored the formation of linear esters (>70%), styrene substrate resulted in the formation of predominantly branched esters of up to 91%.
- Akiri, Saphan O.,Ojwach, Stephen O.
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- N-Heterocyclic Carbene/Carboxylic Acid Co-Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading
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We report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N-heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α- and β-substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N-Mes-/N-2,4,6-trichlorophenyl 1,2,4-triazolium salt, and benzoic acid as co-catalyst, was developed. A whole series of α/β-substituted aliphatic aldehydes/enals hitherto not amenable to NHC-catalyzed esterification could be reacted at typical catalyst loadings of 0.02–1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid-induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.
- Berkessel, Albrecht,Biswas, Animesh,Harnying, Wacharee,Sudkaow, Panyapon
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supporting information
p. 19631 - 19636
(2021/08/09)
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- Sustainable System for Hydrogenation Exploiting Energy Derived from Solar Light
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Herein described is a sustainable system for hydrogenation that uses solar light as the ultimate source of energy. The system consists of two steps. Solar energy is captured and chemically stored in the first step; exposure of a solution of azaxanthone in ethanol to solar light causes an energy storing dimerization of the ketone to produce a sterically strained 1,2-diol. In the second step, the chemical energy stored in the vicinal diol is released and used for hydrogenation; the diol offers hydrogen onto alkenes and splits back to azaxanthone, which is easily recovered and reused repeatedly for capturing solar energy.
- Ishida, Naoki,Kamae, Yoshiki,Ishizu, Keigo,Kamino, Yuka,Naruse, Hiroshi,Murakami, Masahiro
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supporting information
p. 2217 - 2220
(2021/02/16)
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- Metal-free reduction of unsaturated carbonyls, quinones, and pyridinium salts with tetrahydroxydiboron/water
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A series of unsaturated carbonyls, quinones, and pyridinium salts have been effectively reduced to the corresponding saturated carbonyls, dihydroxybenzenes, and hydropyridines in moderate to high yields with tetrahydroxydiboron/water as a mild, convenient, and metal-free reduction system. Deuterium-labeling experiments have revealed this protocol to be an exclusive transfer hydrogenation process from water. This journal is
- Li, Tiejun,Peng, Henian,Tang, Wenjun,Tian, Duanshuai,Xu, Guangqing,Yang, He
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p. 4327 - 4337
(2021/05/31)
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- Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
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We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
- Topf, Christoph,Vielhaber, Thomas
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- Chemoselective Electrosynthesis Using Rapid Alternating Polarity
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Challenges in the selective manipulation of functional groups (chemoselectivity) in organic synthesis have historically been overcome either by using reagents/catalysts that tunably interact with a substrate or through modification to shield undesired sites of reactivity (protecting groups). Although electrochemistry offers precise redox control to achieve unique chemoselectivity, this approach often becomes challenging in the presence of multiple redox-active functionalities. Historically, electrosynthesis has been performed almost solely by using direct current (DC). In contrast, applying alternating current (AC) has been known to change reaction outcomes considerably on an analytical scale but has rarely been strategically exploited for use in complex preparative organic synthesis. Here we show how a square waveform employed to deliver electric current - rapid alternating polarity (rAP) - enables control over reaction outcomes in the chemoselective reduction of carbonyl compounds, one of the most widely used reaction manifolds. The reactivity observed cannot be recapitulated using DC electrolysis or chemical reagents. The synthetic value brought by this new method for controlling chemoselectivity is vividly demonstrated in the context of classical reactivity problems such as chiral auxiliary removal and cutting-edge medicinal chemistry topics such as the synthesis of PROTACs.
- Baran, Phil S.,Carlson, Ethan,Edwards, Jacob T.,Hayashi, Kyohei,Kawamata, Yu,Saito, Masato,Shaji, Shobin,Simmons, Bryan J.,Waldmann, Dirk,Zapf, Christoph W.
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supporting information
p. 16580 - 16588
(2021/10/20)
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- Palladium-catalyzed dehydrogenative C-H cyclization for isoindolinone synthesis
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In this paper Pd-catalyzed intramolecular dehydrogenative C(sp3)-H amidation for the synthesis of isoindolinones is described. This method features the use of a Pd/C catalyst and the addition of a stoichiometric amount of oxidant is not necessary. A mechanistic study suggested the possible formation of H2gas during the reaction.
- Abe, Masahiro,Inamoto, Kiyofumi,Kimachi, Tetsutaro,Tanaka, Saki,Ueta, Kaho
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p. 26988 - 26991
(2021/08/17)
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- Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
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A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
- Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
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supporting information
p. 18591 - 18598
(2021/06/28)
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- Reduction of Electron-Deficient Alkenes Enabled by a Photoinduced Hydrogen Atom Transfer
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Direct hydrogen atom transfer from a photoredox-generated Hantzsch ester radical cation to electron-deficient alkenes has enabled the development of an efficient formal hydrogenation under mild, operationally simple conditions. The HAT-driven mechanism is supported by experimental and computational studies. The reaction is applied to a variety of cinnamate derivatives and related structures, irrespective of the presence of electron-donating or electron-withdrawing substituents in the aromatic ring and with good functional group compatibility. (Figure presented.).
- Larionova, Natalia A.,Ondozabal, Jun Miyatake,Cambeiro, Xacobe C.
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supporting information
p. 558 - 564
(2020/12/07)
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- Heterogeneous Isomerization for Stereoselective Alkyne Hydrogenation to trans-Alkene Mediated by Frustrated Hydrogen Atoms
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Stereoselective production of alkenes from the alkyne hydrogenation plays a crucial role in the chemical industry. However, for heterogeneous metal catalysts, the olefins in cis-configuration are usually dominant in the products due to the most important and common Horiuti-Polanyi mechanism involved over the metal surface. In this work, through combined theoretical and experimental investigations, we demonstrate a novel isomerization mechanism mediated by the frustrated hydrogen atoms via the H2 dissociation at the defect on solid surface, which can lead to the switch in selectivity from the cis-configuration to trans-configuration without overhydrogenation. The defective Rh2S3 with exposing facet of (110) exhibits outstanding performance as a heterogeneous metal catalyst for stereoselective production of trans-olefins. With the frustrated hydrogen atoms at spatially separated high-valence Rh sites, the isolated hydrogen mediated cis-to-trans isomerization of olefins can be effectively conducted and the overhydrogenation can be completely inhibited. Furthermore, the bifunctional Rh-S/Pd nanosheets have been synthesized through the surface modification of Pd nanosheets with rhodium and sulfide. With the selective semihydrogenation of alkynes into cis-olefins catalyzed by the small surface PdSx ensembles, the bifunctional Rh-S/Pd nanosheets exhibit excellent activity and stereoselectivity in the one-pot alkyne hydrogenation into trans-olefin, which surpasses the most reported homogeneous and heterogeneous catalysts.
- Zhang, Weijie,Qin, Ruixuan,Fu, Gang,Zheng, Nanfeng
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supporting information
p. 15882 - 15890
(2021/10/02)
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- Photo-induced thiolate catalytic activation of inert Caryl-hetero bonds for radical borylation
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Substantial effort is currently being devoted to obtaining photoredox catalysts with high redox power. Yet, it remains challenging to apply the currently established methods to the activation of bonds with high bond dissociation energy and to substrates with high reduction potentials. Herein, we introduce a novel photocatalytic strategy for the activation of inert substituted arenes for aryl borylation by using thiolate as a catalyst. This catalytic system exhibits strong reducing ability and engages non-activated Caryl–F, Caryl–X, Caryl–O, Caryl–N, and Caryl–S bonds in productive radical borylation reactions, thus expanding the available aryl radical precursor scope. Despite its high reducing power, the method has a broad substrate scope and good functional-group tolerance. Spectroscopic investigations and control experiments suggest the formation of a charge-transfer complex as the key step to activate the substrates.
- K?nig, Burkhard,Wang, Hua,Wang, Shun
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supporting information
p. 1653 - 1665
(2021/06/17)
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- Electrochemical Synthesis of 2-Bromoethyl and 2-Iodoethyl Ketones from Cyclopropanols
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A simple electrochemical protocol for the preparation of 2-bromoethyl- and 2-iodoethyl ketones from cyclopropanols and magnesium halides has been developed. The reaction proceeded with exclusive regioselectivity and without epimerization of the α-stereocenter in the products. We also showed that the synthesized diastereomerically pure 2-bromoethyl ketones undergo smooth copper and nickel-catalyzed alkylation, alkenylation, and arylations reactions.
- Barysevich, Maryia V.,Aniskevich, Yauhen M.,Hurski, Alaksiej L.
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p. 1934 - 1938
(2021/10/19)
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- Anhydrous Hydrogen Iodide-Mediated Reductive Indolization of in Situ-Generated Cyclopropyl Hydrazones
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Fischer-type indolization of N-aryl-C-cyclopropyl hydrazones generated in situ followed by chemoselective reduction using tert-butyl iodide as an anhydrous HI generator was developed. This protocol provides indoles bearing carboxylic acid derivative units. A series of control experiments indicated the HI-mediated formation and reduction of spirocyclopropyl indolenines. Anhydrous HI functions as a Br?nsted acid as well as a reducing agent, facilitating the successful conversion of unstable reaction intermediates and iodinated mixtures in equilibrium.
- Fujioka, Hiroki,Takeda, Norihiko,Ueda, Masafumi,Yasui, Motohiro
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supporting information
(2021/12/17)
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- Unsaturated ketone compound as well as preparation method and application thereof
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The present invention relates to a novel GPR52 antagonist. Specifically, the invention relates to an unsaturated ketone compound, a pharmaceutically acceptable salt, a stereoisomer or a prodrug molecule thereof, and a method for preparing a pharmaceutical composition thereof. The invention further relates to the use of the GPR52 antagonist as an orphan G protein coupled receptor GPR52 antagonist,and further relates to the use of the GPR52 antagonist in the preparation of drugs for preventing and treating Huntington's disease.
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Paragraph 0070-0073
(2020/10/30)
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- Iron-catalysed 1,2-aryl migration of tertiary azides
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1,2-Aryl migration of α,α-diaryl tertiary azides was achieved by using the catalytic system of FeCl2/N-heterocyclic carbene (NHC) SIPr·HCl. The reaction generated aniline products in good yields after one-pot reduction of the migration-resultant imines.
- Wei, Kaijie,Yang, Tonghao,Chen, Qing,Liang, Siyu,Yu, Wei
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supporting information
p. 11685 - 11688
(2020/10/19)
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- Palladium-Catalyzed Alkoxycarbonylation of sec-Benzylic Ethers
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Herein, we report the palladium-catalyzed synthesis of 3-arylpropionate esters starting from secondary benzylic ethers. With this investigation it could be shown that ethers are suitable starting materials in addition to the established carbonylation reactions of olefins, alcohols, or aryl halides.
- Beller, Matthias,Jackstell, Ralf,Maes, Bert U. W.,Schneider, Carolin
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supporting information
(2020/02/25)
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- Method for preparing organic carboxylic ester through combined catalysis of aryl bidentate phosphine ligand
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The invention discloses a method for preparing organic carboxylic ester by combined catalysis of an aryl bidentate phosphine ligand. The method comprises the following steps: under the action of a palladium compound/aryl bidentate phosphine ligand/acidic additive combined catalyst, carrying out a hydrogen esterification reaction on terminal olefin, carbon monoxide and alcohol so as to generate theorganic carboxylic ester with one more carbon than olefin. According to the invention, by adoption of the palladium compound/aryl bidentate phosphine ligand/acidic additive combined catalyst, good catalytic activity and selectivity for the hydrogen esterification reaction of the olefin are achieved, and olefin carbonylation to synthesize organic carboxylic ester can be efficiently catalyzed. Thearyl bidentate phosphine ligand has a rigid skeleton structure of a rigid ligand and the flexibility of a flexible ligand, so the aryl bidentate phosphine ligand has proper flexibility due to the characteristic that the aryl bidentate phosphine ligand is soft and rigid, and a most favorable coordination mode and a stable active structure in space are favorably formed. In addition, the aryl bidentate phosphine ligand has the advantages of high stability, simple and convenient synthesis method and the like; and a novel industrial technology is provided for production of organic carboxylate compounds.
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Paragraph 0047
(2020/05/29)
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- A general platinum-catalyzed alkoxycarbonylation of olefins
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Hydroxy- and alkoxycarbonylation reactions constitute important industrial processes in homogeneous catalysis. Nowadays, palladium complexes constitute state-of-the-art catalysts for these transformations. Herein, we report the first efficient platinum-catalysed alkoxycarbonylations of olefins including sterically hindered and functionalized ones. This atom-efficient catalytic transformation provides straightforward access to a variety of valuable esters in good to excellent yields and often with high selectivities. In kinetic experiments the activities of Pd- and Pt-based catalysts were compared. Even at low catalyst loading, Pt shows high catalytic activity.
- Beller, Matthias,Dühren, Ricarda,Franke, Robert,Ge, Yao,Huang, Weiheng,Jackstell, Ralf,Liu, Jiawang,Neumann, Helfried,Schneider, Carolin,Yang, Ji
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supporting information
p. 5235 - 5238
(2020/07/30)
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- Palladium catalyzed hydroesterification of substituted alkenes under microwave conditions
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While several catalyst systems have been utilized in the hydroesterification or methoxycarbonylation of alkenes or equivalent substrates, these reactions are conventionally performed in autoclave reactor systems under high CO pressure (20-70 bar) and thermal heating (70 - 110 oC). In this paper, the first methoxycarbonylation reactions performed in a microwave reactor fitted with a gas-Addition accessory system are reported on and compared to the same reactions performed under conventional heating in an autoclave reactor. Thus 1-octene, styrene, allylbenzene, o-and p-methoxyallylbenzene and β-methylstyrene were subjected to methoxycarbonylation over a palladium acetate-aluminum triflate catalyst system at 12 bar and 95 oC. Results obtained indicated the methoxycarbonylation of these alkenes to be much faster under microwave conditions when compared to conventional heating and improvements in conversion ranged between 3 and 5% for the more reactive substrates (1-octene and styrene) and 6 - 20% for the allylbenzenes and β-methylstyrene.
- Du Plessis, Maretha,Marais, Charlene,Bezuidenhoudt, Barend C. B.
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supporting information
p. 40 - 48
(2020/09/16)
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- Ni-catalyzed direct alcoholysis of N-acylpyrrole-type tertiary amides under mild conditions
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N-Acylpyrrole-type amides are a class of versatile building blocks in asymmetric synthesis. We report that by employing Ni(COD)2/2,2′-bipyridine (5 mol%) catalytic system, the direct, catalytic alcoholysis of N-acylpyrrole-type aromatic and aliphatic amides with both primary and secondary alcohols can be achieved efficiently under very mild conditions (rt, 1 h) even at gram scale. By increasing the catalyst loading to 10 mol%, prolonging reaction time (18 h), and/or elevating reaction temperature to 50 °C/80 °C, the reaction could be extended to both complex and hindered N-acylpyrroles as well as to N-acylpyrazoles, Nacylindoles, and to other (functionalized) primary and secondary alcohols. In all cases, only 1.5 equiv. of alcohol were used. The value of the method has been demonstrated by the racemization-free, catalytic alcoholysis of chiral amides yielded from other asymmetric methodologies.
- Chen, Hang,Chen, Dong-Huang,Huang, Pei-Qiang
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p. 370 - 376
(2020/03/03)
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- Hydrogenation reaction method
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The invention relates to a hydrogenation reaction method, and belongs to the technical field of organic synthesis. The hydrogenation reaction method provided by the invention comprises the following steps: carrying out a hydrogen transfer reaction on a hydrogen acceptor compound, pinacol borane and a catalyst in a solvent in the presence of proton hydrogen, so that the hydrogen acceptor compound is subjected to a hydrogenation reaction; the catalyst is one or more than two of a palladium catalyst, an iridium catalyst and a rhodium catalyst; the hydrogen acceptor compound comprises one or morethan two functional groups of carbon-carbon double bonds, carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogentriple bonds and epoxy. The method is mild in reaction condition, easy to operate, high in yield, short in reaction time, wide in substrate application range, suitable for carbon-carbon double bonds,carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogen triple bonds and epoxy functional groups, good in selectivity and high in reaction specificity.
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Paragraph 0034; 0113-0116
(2020/05/14)
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- Diboron-Mediated Rhodium-Catalysed Transfer Hydrogenation of Alkenes and Carbonyls
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A diboron-mediated rhodium-catalysed transfer hydrogenation system using water as the hydrogen donor is developed. In addition to a series of alkenes with good functional group tolerance, this rhodium-based catalytic system also effectively reduces aldehydes and ketones. A plausible mechanism involving the RhI-catalysed hydrogen generation and Rh0-catalysed hydrogenation is proposed for the reaction.
- Lin, Xiao,Wang, Yuhan,Hu, Yan,Zhu, Wanjiang,Dou, Xiaowei
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supporting information
p. 1046 - 1049
(2020/02/25)
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- Engineering Catalysts for Selective Ester Hydrogenation
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The development of efficient catalysts and processes for synthesizing functionalized (olefinic and/or chiral) primary alcohols and fluoral hemiacetals is currently needed. These are valuable building blocks for pharmaceuticals, agrochemicals, perfumes, and so forth. From an economic standpoint, bench-stable Takasago Int. Corp.'s Ru-PNP, more commonly known as Ru-MACHO, and Gusev's Ru-SNS complexes are arguably the most appealing molecular catalysts to access primary alcohols from esters and H2 (Waser, M. et al. Org. Proc. Res. Dev. 2018, 22, 862). This work introduces economically competitive Ru-SNP(O)z complexes (z = 0, 1), which combine key structural elements of both of these catalysts. In particular, the incorporation of SNP heteroatoms into the ligand skeleton was found to be crucial for the design of a more product-selective catalyst in the synthesis of fluoral hemiacetals under kinetically controlled conditions. Based on experimental observations and computational analysis, this paper further extends the current state-of-the-art understanding of the accelerative role of KO-t-C4H9 in ester hydrogenation. It attempts to explain why a maximum turnover is seen to occur starting at 25 mol % base, in contrast to only 10 mol % with ketones as substrates.
- Dub, Pavel A.,Batrice, Rami J.,Gordon, John C.,Scott, Brian L.,Minko, Yury,Schmidt, Jurgen G.,Williams, Robert F.
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p. 415 - 442
(2020/03/04)
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- Pentamethylphenyl (Ph*) and Related Derivatives as Useful Acyl Protecting Groups for Organic Synthesis: A Preliminary Study
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A study of acyl protecting groups derived from the Ph? motif is reported. While initial studies indicated that a variety of functional groups were not compatible with the Br 2-mediated cleavage conditions required to release the Ph? group, strategies involving the use of different reagents or a modification of Ph? itself (Ph*OH) were investigated to solve this problem.
- Cheong, Choon Boon,Frost, James R.,Donohoe, Timothy J.
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p. 1828 - 1832
(2020/10/06)
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- Trizaine-based dehydrative condensation reagents bearing carbon-substituents
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Herein, we report on the synthesis of alkyl-, aryl-, and alkynyl-substituted chlorotriazines and their ammonium salts, and demonstrate their utility in dehydrative condensation reactions. Although the electrophilicity of these reagents is mainly dependent on the hybridization of the carbon-substituents, it was found that bulky 2,6-dimethylphenyl group-substituted reagents resulted in the highest product yields because of a slight increase in reagent electrophilicity and/or steric hindrance favorable for desired dehydrative condensation reactions.
- Kitamura, Masanori,Komine, Sayaka,Kunishima, Munetaka,Yamada, Kohei
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- Mechanistic studies of nickel(II)-catalyzed direct alcoholysis of 8-aminoquinoline amides
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This paper describes the mechanistic aspects of nickel(II)-catalyzed direct alcoholysis of 8-aminoquinoline amides. Kinetic experiments suggested that the nickel(II) catalyst existed in an oligomeric form in the resting state, and the 8-aminoquinoline gen
- Morimoto, Hiroyuki,Akkad, Walaa,Deguchi, Toru,Ohshima, Takashi
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p. 471 - 485
(2020/01/31)
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- Linear-regioselective hydromethoxycarbonylation of styrene using Ru-clusters/CeO2 catalyst
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Hydroalkoxycarbonylation of olefins has been considered to be one of the most attractive methods to synthesize esters. Controlling the regioselectivities of linear esters (L) and branched esters (B) is a challenging project for researchers working in this reaction. Although most of the attention has been paid to control the regioselectivity through ligand design in homogeneous catalytic systems, study in the area is still limited. Herein, Ru-clusters/CeO2 is employed as a heterogeneous catalyst for the hydromethoxycarbonylation of styrene without any additives. After optimization of the reaction conditions, the conversion of styrene is > 99% with 83% and 12% regioselectivity of linear and branched ester, respectively. By using different supports (CeO2 (nanoparticle), CeO2-rod, and CeO2-cube), three catalysts including Ru-clusters/CeO2, Ru/CeO2-rod, and Ru/CeO2-cube are prepared and applied in the reaction. Structural characterizations demonstrate that the L/B ratio is related to the Ru size of supported Ru catalysts. Further Raman characterization and NH3-TPD demonstrate that the metal-support interaction and the concentration of oxygen vacancy of the catalyst have a great influence on the Ru size. The mechanism and kinetic analysis for this reaction are also investigated in this work.
- An, Jinghua,Dunin-Borkowski, Rafal E.,Gocyla, Martin,Wang, Feng,Wang, Yehong,Zhang, Jian,Zhang, Zhixin
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p. 963 - 969
(2020/02/04)
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- Aldehyde as a Traceless Directing Group for Regioselective C-H Alkylation Catalyzed by Rhodium(III) in Air
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The aromatic aldehyde as a traceless directing group for the regionselective C-H alkylation catalyzed by rhodium(III) under aerobic atmospheric conditions has been developed. The process involves an aldehyde assisted direct addition of C-H bond to unsaturated electrophiles of acrylates or acrylic acids, and the subsequent decarbonylation. A trace amount of water is found to favor the reaction.
- Chen, Si-Qi,Fan, Juan,Li, Chao-Jun,Li, Xin-Ran,Liu, Zhong-Wen,Shi, Xian-Ying
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supporting information
p. 1259 - 1264
(2020/03/13)
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- Rh-Catalyzed Direct Carboxylation of Alkenyl C?H Bonds of Alkenylpyrazoles
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The Rh-catalyzed direct carboxylation of alkenyl C?H bonds was achieved by using pyrazole as a removable directing group. In the presence of 5 mol% RhCl3 ? 3H2O, 6 mol% P(Mes)3, and 2 equiv. of AlMe2(OMe), the alkenyl C?H bond of various alkenylpyrazoles was directly carboxylated in good yields under CO2 atmosphere. Furthermore, several useful transformations of the pyrazole moiety of the product were achieved to afford synthetically useful carboxylic acid derivatives in good yields.
- Saitou, Takanobu,Jin, Yushu,Isobe, Kotaro,Suga, Takuya,Takaya, Jun,Iwasawa, Nobuharu
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p. 1941 - 1944
(2020/06/10)
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- Benzannulation of isobenzopyryliums with electron-rich alkynes: A modular access to β-functionalized naphthalenes
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Described here is a modular strategy for the rapid synthesis of β-functionalized electron-rich naphthalenes, a family of valuable molecules lacking general access previously. Our approach employs an intermolecular benzannulation of in situ generated isobenzopyrylium ions with various electron-rich alkynes, which were not well utilized for this type of reaction before. These reactions not only feature a broad scope, complete regioselectivity, and mild conditions, but also exhibit unusual product divergence depending on the substrate substitution pattern. This divergence allows further expansion of the product diversity. Control experiments provided preliminary insights into the reaction mechanism.
- Qian, Hui,Sun, Jianwei,Wu, An,Zhao, Wanxiang
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p. 7957 - 7962
(2020/08/14)
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- Ruthenium-catalyzed hydrogenation of CO2as a route to methyl esters for use as biofuels or fine chemicals
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A novel robust diphosphine-ruthenium(ii) complex has been developed that can efficiently catalyze both the hydrogenation of CO2 to methanol and its in situ condensation with carboxylic acids to form methyl esters; a TON of up to 3260 is achievable for the CO2 to methanol step. Both aromatic and aliphatic carboxylic acids can be transformed to their corresponding methyl esters with high conversion and selectivity (17 aliphatic and 18 aromatic examples). On the basis of a series of experiments, a mechanism has been proposed to account for the various steps involved in the catalytic pathway. More importantly, this approach provides a promising route for using CO2 as a C1 source for the production of biofuels, fine chemicals and methanol.
- Li, Yong,Liu, Qingbin,Ma, Yanping,Solan, Gregory A.,Sun, Wen-Hua,Wang, Zheng,Zhang, Qiuyue,Zhao, Ziwei,Zhong, Yanxia
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p. 6766 - 6774
(2020/08/25)
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- C-C Bond Cleavage of Unactivated 2-Acylimidazoles
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2-Acylimidazoles are widely used as post-Transformable carboxylic acid equivalents in chemoselective and enantioselective reactions. Their transformations, however, require pretreatment with highly reactive, toxic methylating reagents to facilitate C-C bond cleavage. Here, we demonstrate that such pretreatment can be avoided and the C-C bond cleaved under neutral conditions without the use of additional reagents or catalysts. The scope of the reaction, including the use of products reported in the literature as substrates, and some mechanistic insights are described.
- Xin, Hai-Long,Pang, Bo,Choi, Jeesoo,Akkad, Walaa,Morimoto, Hiroyuki,Ohshima, Takashi
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supporting information
p. 11592 - 11606
(2020/10/23)
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- Hydrosilane-Promoted Facile Deprotection of tert-Butyl Groups in Esters, Ethers, Carbonates, and Carbamates
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Combination of PdCl2 with 1,1,3,3-tetramethyldisiloxane in the presence of activated carbon was found to be an effective catalyst system for the cleavage reaction of C?O bond of O?t-Bu moieties. The present catalytic reaction offers a practical method for the deprotection of tert-butyl esters, tert-butyl ethers, O-Boc, and N-Boc derivatives under mild conditions. The addition of activated carbon in the reaction mixture was proved to be crucial for not only sustaining the catalytic activity but also trapping the palladium species after the reaction. (Figure presented.).
- Ikeda, Takuya,Zhang, Zhenzhong,Motoyama, Yukihiro
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supporting information
p. 673 - 677
(2019/01/04)
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- Synthesis and anti-coronavirus activity of a series of 1-thia-4-azaspiro[4.5]decan-3-one derivatives
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A series of 1-thia-4-azaspiro[4.5]decan-3-ones bearing an amide group at C-4 and various substitutions at C-2 and C-8 were synthesized and evaluated against human coronavirus and influenza virus. Compounds 7m, 7n, 8k, 8l, 8m, 8n, and 8p were found to inhibit human coronavirus 229E replication. The most active compound was N-(2-methyl-8-tert-butyl-3-oxo-1-thia-4-azaspiro[4.5]decan-4-yl)-3-phenylpropanamide (8n), with an EC50 value of 5.5 μM, comparable to the known coronavirus inhibitor, (Z)-N-[3-[4-(4-bromophenyl)-4-hydroxypiperidin-1-yl]-3-oxo-1-phenylprop-1-en-2-yl]benzamide (K22). Compound 8n and structural analogs were devoid of anti-influenza virus activity, although their scaffold is shared with a previously discovered class of H3 hemagglutinin-specific influenza virus fusion inhibitors. These findings point to the 1-thia-4-azaspiro[4.5]decan-3-one scaffold as a versatile chemical structure with high relevance for antiviral drug development.
- Apayd?n, ?a?la Begüm,Cesur, Nesrin,Stevaert, Annelies,Naesens, Lieve,Cesur, Zafer
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- Iron catalysed selective reduction of esters to alcohols
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The reaction of (dppBIAN)FeCl2 with 3 equivalents of n-BuLi affords a catalytically active anionic Fe complex; the nature of the anionic complex was probed using EPR and IR experiments and is proposed to involve a dearomatized, radical, ligand scaffold. This complex is an active catalyst for the hydrosilylation of esters to afford alcohols; loadings as low as 1 mol% were employed.
- Tamang, Sem Raj,Cozzolino, Anthony F.,Findlater, Michael
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supporting information
p. 1834 - 1838
(2019/02/20)
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- Synthesis and discovery of 18β-glycyrrhetinic acid derivatives inhibiting cancer stem cell properties in ovarian cancer cells
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Despite advances in ovarian cancer treatment, the five-year overall survival rate is less than 30% with the presence of cancer stem cells (CSCs). To develop CSC-targeting therapy, a series of 18β-glycyrrhetinic acid (GA) derivatives containing cinnamamide moiety have been designed, synthesized, and screened for their antiproliferative activity in SKOV3 and OVCAR3 cells. Most of the compounds exhibited stronger antiproliferative activity than GA, and compound 7c was the most active one. Further biological studies showed that compound 7c could induce apoptosis and suppress migration. In addition, compound 7c could not only observably decrease the colony formation and sphere formation ability, but also significantly reduce the CD44+, CD133+, and ALDH+ subpopulation in SKOV3 and OVCAR3 cells. In conclusion, these results indicate that compound 7c is a promising anti-CSC agent for further anti-ovarian cancer studies.
- Li, Xiaojing,Liu, Yihua,Wang, Na,Liu, Yuyu,Wang, Shuai,Wang, Hongmin,Li, Aihua,Ren, Shaoda
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p. 27294 - 27304
(2019/09/12)
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- Synthesis and biological evaluation of celastrol derivatives as anti-ovarian cancer stem cell agents
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Ovarian cancer is associated with a high percentage of recurrence of tumors and resistance to chemotherapy. Cancer stem cells (CSCs) are responsible for cancer progression, tumor recurrence, metastasis, and chemoresistance. Thus, developing CSC-targeting therapy is an urgent need in cancer research and clinical application. In an attempt to achieve potent and selective anti-CSC agents, a series of celastrol derivatives with cinnamamide chains were synthesized and evaluated for their anti-ovarian cancer activities. Most of the compounds exhibited stronger antiproliferative activity than celastrol, and celastrol derivative 7g with a 3,4,5-trimethoxycinnamamide side chain was found to be the most potent antiproliferative agent against ovarian cancer cells with an IC50 value of 0.6 μM. Additionally, compound 7g significantly inhibited the colony formation ability and reduced the number of tumor spheres. Furthermore, compound 7g decreased the percentage of CD44+, CD133+ and ALDH+ cells. Thus, compound 7g is a promising anti-CSC agent and could serve as a candidate for the development of new anti-ovarian cancer drugs.
- Li, Xiaojing,Ding, Jie,Li, Ning,Liu, Wenxia,Ding,Zheng, Huijuan,Ning, Yanyan,Wang, Hongmin,Liu, Renmin,Ren, Shaoda
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p. 667 - 679
(2019/07/05)
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