- One-pot, three-component approach to the synthesis of 3,4,5-trisubstituted pyrazoles
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An operationally simple and high yielding protocol for the synthesis of polyfunctional pyrazoles has been developed through one-pot, three-component coupling of aldehydes, 1,3-dicarbonyls, and diazo compounds as well as tosyl hydrazones. The reaction proceeds through a tandem Knoevenagel condensation, 1,3-dipolar cycloaddition, and transition metal-free oxidative aromatization reaction sequence utilizing molecular oxygen as a green oxidant. The scope of the reaction was studied by varying the aldehyde, 1,3-dicarbonyl, and diazo component individually.
- Kamal, Ahmed,Sastry, K. N. Visweswara,Chandrasekhar,Mani, Geeta Sai,Adiyala, Praveen Reddy,Nanubolu, Jagadeesh Babu,Singarapu, Kiran Kumar,Maurya, Ram Awatar
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- Hydrotalcite reconstructed by in situ rehydration as a highly active solid base catalyst and its application in aldol condensations
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Reconstructed hydrotalcite is a highly active heterogeneous base catalyst for a wide variety of reactions. Herein, we report a procedure to effectively prepare the reconstructed hydrotalcite. Mg-Al mixed oxide, which originates from hydrotalcite, is added directly to the aqueous-phase reaction system of the aldol condensation without the protection of an inert gas. Under the reaction conditions, the reconstructed hydrotalcite is in-situ generated, and is used as a catalyst for then aldol condensation as soon as it forms, resulting in the elimination of the deactivation of reconstructed hydrotalcite. The experimental results showed that the in-situ reconstructed hydrotalcite had higher catalytic activity and water tolerance. The work provides a simple and effective method for reconstructed hydrotalcite.
- Xu, Chunli,Gao, Yuan,Liu, Xihong,Xin, Ruirui,Wang, Zhen
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- Encapsulating mesoporous metal nanoparticles: Towards a highly active and stable nanoreactor for oxidative coupling reactions in water
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We design and prepare a highly active and stable nanoreactor via encapsulating various mesoporous metal nanoparticles with an amphiphilic hollow shell, which presents excellent performance in oxidative coupling reactions in water for efficient production of α,β-unsaturated ketones.
- Zou, Houbing,Dai, Jinyu,Wang, Runwei
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- Persulfate-mediated synthesis of polyfunctionalized benzenes in water: Via the benzannulation of alkynes and α,β-unsaturated compounds
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A persulfate-promoted metal-free route in water toward the synthesis of unprecedented polyfunctionalized benzenes is reported. In our approach, the targeted products are delivered in high to moderate yields from phenylacetylenes and α,β-unsaturated compounds via the benzannulation reaction. This method has a good scope and gives access to functionalized benzene rings that offer a wealth of opportunities for further functionalization.
- De Souza, Gabriela F. P.,Salles, Airton G.
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- A mechanistic investigation of Biginelli reaction under base catalysis
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The mechanism of the three component base mediated Biginelli dihydropyrimidines synthesis was investigated using Accurate Mass TOF LC-MS-ESI and Tandem TOF LC-MS-ESI. We suggest hemiaminal as a possible intermediate leading to the formation of Biginelli product. Under our current experimental conditions we did not observe any bis-ureide as reported by ji et al.
- Kamal Raj,Rao, H. Surya Prakash,Manjunatha, Sulur G.,Sridharan,Nambiar, Sudhir,Keshwan, Jaikumar,Rappai, Jayan,Bhagat, Sagar,Shwetha,Hegde, Dinesh,Santhosh
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- Synthesis and crystal structure of 4,7-diaryl-5-oxo-4H-benzo[b]pyran derivatives
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A green and convenient approach to the synthesis of a series of 4,7-diaryl-5-oxo-4H-benzo[b]pyran derivatives from appropriate aromatic aldehydes and 5-aryl-1,3-cyclohexanedione with malononitrile in the presence of dilute HCl as catalyst (30 mmol/L) is described. This method provides several advantages such as environmental friendliness, low cost, high yields, and simple work up procedure. The structures of all compounds were characterized by infrared (IR), mass spectrometry (MS), 1H NMR, and elemental analysis. The crystal structure of trans/cis-2-amino-3-cyano-7-(4'-methoxo- phenyl)-4-phenyl-5-oxo-4H-benzo[b]pyran, g, was determined by single crystal X-ray diffraction analysis. The crystal of compound g belongs to monoclinic with space group P 21/c, a = 8.477(3) nm, b = 18.948(6) nm, c = 24.915(7) nm, α = 90.00°, β = 107.388(11)°, γ= 90.00°, Z = 8, V = 3.819(2) nm3, R1 = 0.0754, wR2 = 0.2042.
- Cui, Bin,Chen, Li-Zhuang,Hu, Xiao-Lei,Wang, Ming,Han, Guang-Fan
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- Effects of dendritic interface on enantioselective catalysis by polymer-bound prolines
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Dendritic effects have been observed in the past for a number of metal-based catalysts, but only rarely for organocatalysts, and particularly chiral organocatalysts. In the current study, l-proline was immobilized as an ester or amide on polyether dendritic spacers attached to polystyrene. The ester-including catalysts showed a remarkable positive dendritic effect on yield, but even more so on enantioselectivity, in the aldol reaction of acetone with aromatic aldehydes. The positive dendritic effect of the aforementioned catalytic systems on the yield, diastereo- and enantioselectivity of a three-component Mannich reaction was of an even greater magnitude. A series of experiments marked the possibility of catalysis by homogenous l-proline, detached from the resin during the reaction, highly unlikely. Model comparative studies with catalysts equipped with linear or only partially dendritic spacers emphasized the superiority of the fully dendritic spacer architecture.
- Kehat, Tzofit,Goren, Kerem,Portnoy, Moshe
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- Green synthesis and crystal structure of 4,7-diaryl-2-oxo(thio)-1,2,3,4,5, 6,7,8-octahydroquinazoline-5-one derivatives
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A green and convenient approach to the synthesis of novel 4,7-diaryl-2-oxo(thio)-1,2,3,4,5,6,7,8-octahydroquinazoline-5-one derivatives from appropriate aromatic aldehydes and 5-aryl-1,3-cyclohexanedione with urea or thiourea in the presence of dilute HCl as catalyst in water is described. This method provides several advantages such as environmental friendliness, low cost, high yields, and simple workup procedure. The structures of all compounds were characterized by elemental analysis, IR, MS, and 1H NMR. The crystal and molecular structure of 4-(4′-chlorophenyl)-7-(4′-methoxyphenyl)- 1,2,3,4,5,6,7,8-octahydroquinazoline-2,5-dione 5m have been determined by single crystal X-ray diffraction analysis. The crystal of compound 5m belongs to monoclinic with space group P-21/c, a = 1.4353 (4) nm, b = 1.4011 (4) nm, c = 0.9248 (3) nm, α = 90.00°, β = 101.242 (6)°, γ = 90.00°, Z = 4, V = 1.8241 (9) nm3, R1 = 0.0448, and wR2 = 0.1022.
- Han, Guang-Fan,Cui, Bin,Chen, Li-Zhuang,Wang, Rui-Hua,Jin, Yan
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- Fe-catalyzed dithiane radical induced C?S bond activation?addition to α, β-unsaturated ketones
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An efficient and clean strategy to construct organosulfur compounds has been developed via a Fe-catalyzed dithiane C?S bond activation/addition process with α, β-unsaturated ketones. This C?S activation protocol exhibits excellent reactivities, and up to 92% yield of the corresponding thioether-thioester derivatives could be obtained under the mild conditions, allowing the ready preparation of a number of synthetically valuable S-linked conjugates. (Figure presented.).
- Min, Deng,Yuan, Xinyu,Liu, Teng,Liu, Jian,Tang, Shouchu
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- A nano-fibrillated mesoporous carbon as an effective support for palladium nanoparticles in the aerobic oxidation of alcohols "on pure water"
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A novel nano-fibrillated mesoporous carbon (IFMC) was successfully prepared via carbonization of the ionic liquid 1-methyl-3-phenethyl-1H-imidazolium hydrogen sulfate (1) in the presence of SBA-15. The material was shown to be an efficient and unique support for the palladium nanoparticle (PdNP) catalyst Pd@IFMC (2) in aerobic oxidation of heterocyclic, benzylic, and heteroatom containing alcohols on pure water at temperatures as low as 40 °C for the first time and giving almost consistent activities and selectivities within more than six reaction runs. The catalyst has also been employed as an effective catalyst for the selective oxidation of aliphatic and allylic alcohols at 70-80 °C. The materials were characterized by X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption analysis, transmission electron microscopy (TEM), and electron tomography (ET). Our compelling XPS and ET studies showed that higher activity of 2 compared to Pd@CMK-3 and Pd/C in the aerobic oxidation of alcohols on water might be due to the presence of nitrogen functionalities inside the carbon structure and also the fibrous nature of our materials. The presence of a nitrogen heteroatom in the carboneous framework might also be responsible for the relatively uniform and nearly atomic-scale distribution of PdNPs throughout the mesoporous structure and the inhibition of Pd agglomeration during the reaction, resulting in high durability, high stability, and recycling characteristics of 2. This effect was clearly confirmed by comparing the TEM images of the recovered 2 and Pd@CMK-3. Copyright
- Karimi, Babak,Behzadnia, Hesam,Bostina, Mihnea,Vali, Hojatollah
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- Modular Pincer-type Pyridylidene Amide Ruthenium(II) Complexes for Efficient Transfer Hydrogenation Catalysis
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A set of bench-stable ruthenium complexes with new N,N,N-tridentate coordinating pincer-type pyridyl-bis(pyridylideneamide) ligands was synthesized in excellent yields, with the pyridylidene amide in meta or in para position (m-PYA and p-PYA, respectively). While complex [Ru(p-PYA)(MeCN)3]2+ is catalytically silent in transfer hydrogenation, its meta isomer [Ru(m-PYA)(MeCN)3]2+ shows considerable activity with turnover frequencies at 50% conversion TOF50 = 100 h-1. Spectroscopic, electrochemical, and crystallographic analyses suggest considerably stronger donor properties of the zwitterionic m-PYA ligand compared to the partially π-acidic p-PYA analogue, imparted by valence isomerization. Further catalyst optimization was achieved by exchanging the ancillary MeCN ligands with imines (4-picoline), amines (ethylenediamine), and phosphines (PPh3, dppm, dppe). The most active catalyst was comprised of the m-PYA pincer ligand and PPh3, complex [Ru(m-PYA)(PPh3)(MeCN)2]2+, which reached a TOF50 of 430 h-1 under aerobic conditions and up to 4000 h-1 in the absence of oxygen. The presence of oxygen reversibly deactivates the catalytically active species, which compromises activity, but not longevity of the catalyst. Ligand exchange kinetic studies by NMR spectroscopy indicate that the strong trans effect of the phosphine is critical for high catalyst activity. Diaryl, aryl-alkyl, and dialkyl ketones were hydrogenated with high conversion, and α,β-unsaturated ketones produced selectively the saturated ketone as the only product due to exclusive C=C bond hydrogenation, a distinctly different selectivity from most other transfer hydrogenation catalysts.
- Melle, Philipp,Manoharan, Yanisha,Albrecht, Martin
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- Novel basic ionic liquid based on alkylammonium as efficient catalyst for Knoevenagel reaction
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The typical Knoevenagel condensation was carried out smoothly in the presence of a basic ionic liquid of N,N,N′,N′-tetramethyl-N′- hexyl-ethylenediammonium tetrafluoroborate ([TMHEDA]BF4), and 99% of yield was obtained using ethyl cyanoacetate and benzaldehyde as substrates at 60 °C for 1 h. Four reuses of the ionic liquid without dramatic decrease in catalytic activity for Knoevenagel condensation demonstrated the good stability and operability of the ionic liquid. Moreover, the typical nucleophilic addition reactions were also accomplished by the same ionic liquid to check its feasibility. The dual function of the basic ionic liquid both as solvent and catalyst, combined with simple product separation and recycling, is expected to contribute to the development of a green and environmentally friendly strategy. Copyright Taylor & Francis Group, LLC.
- Zhou, Shuai,Liu, Lu,Wang, Bo,Ma, Mingguo,Xu, Feng,Sun, Runcang
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- Efficient C-C cross-coupling reactions by (isatin)-Schiff base functionalized magnetic nanoparticle-supported Cu(II) acetate as a magnetically recoverable catalyst
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Copper catalysts were simply fabricated through surface modification of superparamagnetic iron nanoparticles with indoline-2,3-dione(isatin)-Schiff-base and interaction with Cu from low-cost commercially available starting materials. Catalysts were characterized using atomic absorption spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, UV/Vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. These catalysts showed high efficiency for phosphine-free Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions with good diversity and generality. The catalysts could be easily recovered and reused several times without a significant loss in their catalytic activity and stability.
- Miri, Seyedeh Simin,Khoobi, Mehdi,Ashouri, Fatemeh,Jafarpour, Farnaz,Rashidi Ranjbar, Parviz,Shafiee, Abbas
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- Encapsulation of N,N',N''-tricyclohexylguanidine in hydrophobic zeolite Y: Synthesis and catalytic activity
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N,N',N''-Tricyclohexylguanidine was encapsulated in hydrophobic zeolite Y by reacting N,N'-dicyclohexylcarbodiimide with cyclohexylamine within the supercage. The encapsulated guanidine catalyzes the addition reaction of acetone to benzaldehyde forming 4-phenyl-4-hydroxybutan-2-one as the principal product, as opposed to the homogeneous system which produces 4-phenyl-3-buten-2-one via condensation reaction.
- Sercheli, Ricardo,Ferreira, Alfredo L. B.,Guerreiro, Mario C.,Vargas, Rogerio M.,Sheldon, Roger A.,Schuchardt, Ulf
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- Ligand-free palladium-catalyzed tandem pathways for the synthesis of 4,4-diarylbutanones and 4,4-diaryl-3-butenones under microwave conditions
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Two efficient Pd-catalyzed tandem pathways for the synthesis of 4,4-diaryl-2-butanones and 4,4-diaryl-3-buten-2-ones were elaborated. The first step in both procedures was the Heck coupling of methyl vinyl ketone (MVK) and various aryl iodides leading to 4-aryl-3-buten-2-one with the yield of up to 92% in 1?hr. The second step performed with the same catalyst and a new portion of aryl iodide in the presence K2CO3 as a base produced 4,4-diaryl-3-buten-2-ones in high yield. Reaction selectivity changed completely to saturated 4,4-diaryl-2-butanones, reductive Heck products, when a tertiary amine was used instead of K2CO3. Due to the application of microwave irradiation (MW), the desired products were obtained in high yield in a short time (4?hr), using 0.5?mol% of the Pd (OAc)2 catalyst without additional ligands.
- Wirwis, Anna,Trzeciak, Anna M.
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- Synthesis of 1-hydrocarbon substituted cyclopropyl silyl ketones
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The synthesis of cyclopropyl silyl ketones possessing a hydrocarbon group at 1-position of three-membered ring was investigated. The reaction of sulfoxonium ylide with α,β-unsaturated acylsilanes derived from α,β-unsaturated aldehydes did not afford the desired acylsilane derivatives. Instead, the corresponding silyl enol ethers were yielded exclusively. On the other hand, the Corey-Chaykovsky cyclopropanation of α-substituted α,β-unsaturated aldehydes proceeded well to give 1-substituted cyclopropyl aldehydes. The silyl substitution of formyl proton in the obtained aldehydes via umpolung of carbonyl group afforded the target acylsilanes.
- Honda, Mitsunori,Sasaki, Sho,Nishimoto, Tsuyoshi,Koshiro, Hiromoto,Kunimoto, Ko-Ki,Segi, Masahito
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- PQQ-dependent Dehydrogenase Enables One-pot Bi-enzymatic Enantio-convergent Biocatalytic Amination of Racemic sec-Allylic Alcohols
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The asymmetric amination of secondary racemic allylic alcohols bears several challenges like the reactivity of the bi-functional substrate/product as well as of the α,β-unsaturated ketone intermediate in an oxidation-reductive amination sequence. Heading for a biocatalytic amination cascade with a minimal number of enzymes, an oxidation step was implemented relying on a single PQQ-dependent dehydrogenase with low enantioselectivity. This enzyme allowed the oxidation of both enantiomers at the expense of iron(III) as oxidant. The stereoselective amination of the α,β-unsaturated ketone intermediate was achieved with transaminases using 1-phenylethylamine as formal reducing agent as well as nitrogen source. Choosing an appropriate transaminase, either the (R)- or (S)-enantiomer was obtained in optically pure form (>98 % ee). The enantio-convergent amination of the racemic allylic alcohols to one single allylic amine enantiomer was achieved in one pot in a sequential cascade.
- Gandomkar, Somayyeh,Rocha, Raquel,Sorgenfrei, Frieda A.,Montero, Lía Martínez,Fuchs, Michael,Kroutil, Wolfgang
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- Chromium trioxide supported onto copper sulfate as an efficient oxidizing agent for oxidation of alcohols under solvent free conditions
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Alcohols are rapidly oxidized to carbonyl compounds using CrO3 supported onto CuSO4 under solvent free conditions. Over-oxidation of aldehydes to carboxylic acids and damage to carbon-carbon double bond is not observed by this method.
- Kiasat, Ali Reza,Kazemi, Foad,Nourbakhsh, Kazem
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- Copper(I)-Catalyzed [4 + 1] Cycloaddition of Silyl Dienol Ethers with Sodium Bromodifluoroacetate: Access to β,β-Difluorocyclopentanone Derivatives
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Silyl dienol ethers readily underwent copper(I)-catalyzed [4 + 1] cycloaddition with sodium bromodifluoroacetate to afford 4,4-difluorocyclopent-1-en-1-yl silyl ethers. On the basis of high-resolution mass spectroscopy analysis, annulation presumably proceeded via a copper(I) difluorocarbene complex, which represents an unprecedented example of [4 + 1] cycloadditions promoted by a transition metal difluorocarbene complex.
- Fuchibe, Kohei,Aono, Tatsuya,Hu, Ji,Ichikawa, Junji
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- Application of high pressure, induced by water freezing, to the direct asymmetric aldol reaction
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High pressure, induced by water freezing, has been successfully applied to the direct catalytic asymmetric aldol reaction, in which higher yield and better enantioselectivity can be realized than in the reaction at room temperature under 0.1MPa.
- Hayashi, Yujiro,Tsuboi, Wataru,Shoji, Mitsuru,Suzuki, Noriyuki
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- Aldol-Type Reaction by Propen-2-yl Acetate with NCS/SnCl2/ROH
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The addition of N-chlorosuccinimide (NCS) to a solution of propen-2-yl acetate, aldehydes, SnCl2, and benzyl alcohol in CH2Cl2 or CH3CN caused an aldol-type reaction to produce 4-substituted 4-benzyloxybutan-2-ones in high yields.Use of methanol instead of benzyl alcohol produced not only 4-methoxybutan-2-one but also 3-buten-2-one by dehydromethoxylation.
- Masuyama, Yoshiro,Kobayashi, Yumiko,Yanagi, Ryota,Kurusu, Yasuhiko
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- Chiral 2,6-lutidinyl-biscarbene complexes of palladium
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Chiral complexes of palladium, 1, with the new tridentate "pincer" ligand 2,6-lutidinyl-biscarbene (C∧N∧C), have been prepared; in the solid state they exhibit helical C2 symmetrical structures which are persistent in solution at least up to 80°C; the chiral nature of 1 has been established by NMR methods using Pirkle's acid as a chiral discriminating agent; racemic mixtures of 1 are highly active catalysts in Heck coupling reactions.
- Tulloch,Danopoulos,Tizzard,Coles,Hursthouse,Hay-Motherwell,Motherwell
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- Direct vinylation of 2-substituted N-(benzylidene)glycinonitriles under basic conditions
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-Vinyl substituted nitriles 5 - 7 were prepared via addition of carbanions generated from nitriles 1, to acetylene (2) and its derivatives 3 and 4. Subsequent cleavage of nitriles 6 and 7 afforded α,β-unsaturated ketones 8 and 9. Copyright (C) 1996 Elsevier Science Ltd.
- Jonczyk, Andrzej,Pakulski, Zbigniew
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- Silica-immobilized piperazine: A sustainable organocatalyst for aldol and Knoevenagel reactions
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Silica-supported piperazine was found to be an efficient catalyst for aldol reactions of aromatic aldehydes and ketones with straightforward product isolation and catalyst reuse. Furthermore, the catalyst is active in Knoevenagel-type reactions to afford coumarin derivatives, using 2-methyltetrahydrofuran (2-MeTHF) as a novel bio-based solvent.
- Shanmuganathan, Saravanakumar,Greiner, Lasse,De María, Pablo Domínguez
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- A molecular electron density theory study to understand the interplay of theory and experiment in nitrone-enone cycloaddition
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Abstract: [3 + 2] cycloaddition (32CA) reaction of C,N-diaryl nitrone with benzylidene acetone has been studied to analyse the mechanism, selectivity and polar character of this nitrone-enone cycloaddition. Topological analysis of the electron localization function (ELF) shows the absence of pseudoradical and carbenoid centre in the nitrone, which allows its classification as a zwitter-ionic (zw) type three atom component (TAC) and hence participation in zw- type cycloadditions is associated with high activation energy barriers. This 32CA reaction follows a one-step mechanism with asynchronous TSs. Endo/meta product is obtained as the major cycloadduct experimentally, which can be rationalized from its calculated lowest activation energy among the four possible reaction pathways. Global electron density transfer (GEDT) at the TSs predict the non-polar character of this 32CA reaction. Topological analysis of the ELF and QTAIM parameters was performed at the TSs. Finally, non-covalent interaction (NCI) gradient isosurfaces are computed to obtain a visualization of non-covalent interactions at the interatomic bonding regions. Graphic Abstract: The experimental and theoretical aspects of [3+2] cycloaddition reactions of C,N-diaryl nitronewith benzylidene acetone is described. The reaction is meta/endo selective and follows onestep mechanism with non-covalent interactions. The C-C and C-O bonds are generated throughcoupling of pseudoradical centers.[Figure not available: see fulltext.]
- Acharjee, Nivedita,Banerji, Avijit
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- Carbenoid-mediated elimination of sulfides and selenides. A mild and efficient method for introducing α,β-double bonds to electron-withdrawing substituents
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Cycloalkanes bearing both an electron-withdrawing group and an arylsulfenyl or arylselenenyl function in β-position are shown to react with 2 equiv. of a carbenoid species to generate the corresponding Michael acceptor. The reaction occurs under very mild conditions and affords the products in good to excellent yields. The process constitutes a useful alternative to the oxidation/syn-elimination sequence.
- Gautier, Arnaud,Garipova, Goulnara,Deléens, Reynald,Piettre, Serge R.
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- Catalysis of Metal(II) Acetate-2,2'-Bipyridine Complexes in the Aldol Condensations
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The rate of the condensation of benzaldehyde with excess acetophenone catalyzed by Co(II) acetate-2,2'-bipyridine complex was obtained by GLC analysis.The rate increased in proportion as the amount of the complex catalyst. 2,2'-Bipyridine ligand in the Co(II) complex enhanced the catalytic activity remarkably, though the ligand itself had no activity.When the molar ratio of Co(II) : bpy was 1 : 1 or 1 : 2, the highest activity was observed.The activation energy of the complex (1 : 1) catalyzed reaction was calculated as 13.7 kcal/mol.The catalysis of the complex behaved like a base catalyst.Briefly, the relation of the complex catalyzed aldol condensations with the enzymatic reaction of Class II aldolase is also described.
- Irie, Kazuo,Watanabe, Ken-ichi
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- Palladium containing periodic mesoporous organosilica with imidazolium framework (Pd@PMO-IL): An efficient and recyclable catalyst for the aerobic oxidation of alcohols
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The application of a novel palladium containing ionic liquid based periodic mesoporous organosilica (Pd@PMO-IL) catalyst in the aerobic oxidation of primary and secondary alcohols under molecular oxygen and air atmospheres is investigated. It was found that the catalyst is quite effective for the selective oxidation of several activated and non-activated alcoholic substrates. The catalyst system could be successfully recovered and reused several times without any significant decrease in activity and selectivity. Moreover, the hot filtration test, atomic absorption spectroscopy (AA) and kinetic study with and without selective catalyst poisons showed that the catalyst works in a heterogeneous pathway without any palladium leaching in reaction solution. Furthermore, nitrogen-sorption experiment and transmission electron microscopy (TEM) image proved the superior stability of high-ordered PMO-IL mesostructure during reaction process. TEM image also confirmed the presence of well-distributed Pd-nanoparticles in the uniform mesochannels of the material. These observations can be attributed to the ionic liquid nature of PMO-IL mesostructure which facilitates the reaction through production, chemical immobilization and stabilization of active palladium nanoparticles, as well as preventing Pd-agglomeration during overall process.
- Karimi, Babak,Elhamifar, Dawood,Clark, James H.,Hunt, Andrew J.
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- Asymmetric aldol reaction in a continuous-flow reactor catalyzed by a highly reusable heterogeneous peptide
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A solid-supported peptide-catalyzed continuous-flow (CF) process was developed for asymmetric aldol reactions. The catalyst was readily synthesized and immobilized by solid-phase peptide synthesis (SPPS) on a swellable polymer support in one single step. Ignoring the peptide cleavage from the resin means no work-up, no purification, and no product loss. After thorough optimization of the reaction conditions, synthetically useful β-hydroxyketone products were obtained in high yields and stereoselectivities. It was found that the heterogeneous catalytic reaction is diffusion-controlled under the present conditions; thus, elevation of the pressure is necessary to maximize conversion of the flow process. Besides being simple and efficient, the described method is also rapid and promisingly productive, with short residence times on the catalyst bed. The immobilized peptidic catalyst is highly recyclable, while further advantageous features are the ease of product isolation and the possibility of facile scale-up, furnishing sustainable catalytic methodology.
- Oetvoes, Sandor B.,Mandity, Istvan M.,Fueloep, Ferenc
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- Improved activity of palladium nanoparticles using a sulfur-containing metal-organic framework as an efficient catalyst for selective aerobic oxidation in water
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A simple and efficient nanostructured catalyst system was developed, comprising Pd nanoparticles stabilized by thiophene groups in a metal-organic framework (MOF). Pd species were deposited into the DUT-67(Zr) structure and reduced to nanoparticles that could be stabilized by the synergistic effect of thiophene groups and confinement in the MOF pores. Increasing the interaction time for palladium entry into the MOF cavities led to more effective incorporation into the metal-organic framework, which produced a more efficient catalytic system. Reduction was performed using NaBH4 or N2H4. The catalysts were characterized by N2 adsorption-desorption analysis, infrared spectroscopy, powder X-ray diffraction, scanning electronic microscopy, and transmission electron microscopy. Selective aerobic oxidation of alcohols in neat water under an O2 atmosphere was achieved with 0.5%Pd/DUT-67(Zr) containing Pd nanoparticles created using NaBH4. Furthermore, the catalyst could be easily separated from the reaction mixture by simple filtration and reused at least ten times without any significant loss in catalytic efficiency under the investigated conditions.
- Abedi, Sedigheh,Morsali, Ali
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- Zeolites with isolated-framework and oligomeric-extraframework hafnium species characterized with pair distribution function analysis
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Zeolites containing framework heteroatoms (e.g., Ti, Sn, and Hf) with open coordination sites behave as solid-state Lewis acids and exhibit remarkable catalytic properties unachievable with bulk oxides. However, direct evidence confirming the incorporation of such heteroatom species into the zeolite framework is difficult to obtain because of the limited number of analytical methods capable of discerning framework incorporation from extraframework species. In this work, the structural environments of hafnium (Hf) framework and extraframework species added post-synthetically into ?BEA zeolites were analyzed using coupled pair distribution function (PDF) and diffuse reflectance (DR) UV-vis measurements. PDF analysis enabled the visualization and identification of framework and extraframework HfOx species, both of which were undetectable by traditional X-ray and neutron diffraction methods. Reactivity data from the aldol condensation of benzaldehyde and acetone confirmed that framework Hf species are responsible for catalytic activity.
- Iida, Takayuki,Ohara, Koji,Román-Leshkov, Yuriy,Wakihara, Toru
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- Development of a new palladium catalyst supported on phenolic resin
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A phenolic resin-supported palladium catalyst, in which hydroxyl groups contribute to the stabilization of palladium nanoparticles, was developed. The catalyst could be used repeatedly, and thus has a large turn over number (TON). When a composite of polyethylene terephthalate and phenolic resin was employed as a support, the catalyst was easily deformed on demand.
- Nishiwaki, Nagatoshi,Hamada, Sayaka,Watanabe, Tomoe,Hirao, Shotaro,Sawayama, Jun,Asahara, Haruyasu,Saigo, Kazuhiko,Kamata, Toru,Funabashi, Masahiko
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- Acid-Base Pairs in Lewis Acidic Zeolites Promote Direct Aldol Reactions by Soft Enolization
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Hf-, Sn-, and Zr-Beta zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions.
- Lewis, Jennifer D.,Van De Vyver, Stijn,Romn-Leshkov, Yuriy
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- The Claisen-Schmidt reaction carried out in microfluidic chips
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The Claisen-Schmidt reaction of benzaldehyde in a microfluidic chip has been found to be more efficient than that in a round-bottom flask with vigorous stirring. Slug flow was formed when the organic and aqueous phases were introduced through the microchannel with a width of 300 μm, which provides faster mass transfer than laminar flow. Georg Thieme Verlag Stuttgart.
- Mu, Jin-Xia,Yin, Xue-Feng,Wang, Yan-Guang
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- Novel and efficient one pot condensation reactions between ketones and aromatic alcohols in the presence of CrO3 producing α,β-unsaturated carbonyl compounds
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We report a new, effective and simple method for preparing α,β-unsaturated carbonyl compounds by reacting ketones and aromatic alcohols at 56 °C in the presence of CrO3 (CrO3 acts as an oxidant and also a catalyst) for around 10 h. The condensation reactions occurred effectively among a wide combination of ketones and alcohols. The procedure is simple and the yields can be high up to 98%. And a probable mechanism is proposed.
- Li, Yanan,Chen, Daoyong
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- Fe3O4?l-Proline/Pd nanocomposite for one-pot tandem catalytic synthesis of (±)-warfarin from benzyl alcohol: Synergistic action of organocatalyst and transition metal catalyst
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One-pot synthesis of (±)-warfarin, an anticoagulant, has been achieved from benzyl alcohol in a 'green way' by using a multicomponent catalyst. For the purpose, l-proline capped Fe3O4 nanoparticles (Fe3O4?l-proline NPs) were synthesized and metallic palladium was loaded on its surface (Fe3O4?l-proline/Pd NCs). The morphology, particle size and shape were studied by using FESEM and TEM analysis. The Pd present on the surface was responsible for oxidation of benzyl alcohol and its derivatives to the corresponding aldehyde in situ. This in turn, condensed with acetone to form the aldol condensation product, benzylideneacetone, at 70 °C due to the presence of the l-proline organocatalyst on the surface of Fe3O4 NPs. Later, 4-hydroxycoumarin was introduced to condense with in situ generated benzylideneacetone by a Michael addition to form the target product (±)-warfarin. It was established that benzyl alcohol can be converted into the final product, (±)-warfarin, with an overall 35% yield within 5 days in a single-pot process. This process requires a rise in temperature in stages to a maximum of 100 °C and 1 atm pressure of dioxygen gas. An important aspect of the developed process is the avoidance of loss of costly Pd by leaching and catalyst recovery by the use of a magnetic field. The use of a solvent like PEG-400 makes the process green in a true sense. The interaction of l-proline with Fe3O4 NPs and the presence of Pd on the surface were confirmed by the FTIR and XRD patterns, respectively. The present study hereby suggests a combined 3-step mechanism for the production of the target product warfarin. Pilot-scale one-pot production of (±)-warfarin was carried out and a flow diagram with various unit processes is presented.
- Tomer, Sanjiv O.,Soni, Hemant P.
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- Alanine-supported protic ionic liquids as efficient catalysts for aldol condensation reactions
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A series of novel protic ionic liquids were immobilized on alanine, a cheap readily available amino acid. These short aliphatic chain ionic liquids have a low cost of preparation, a low toxicity, and need simple synthesis/purification processes. Their catalytic activity was tested for citral-acetone and benzaldehyde-acetone condensations, two reactions with an interest for pharmacological as well as flavor and fragrance industry. Good results were obtained in terms of conversion and selectivity; moreover, the catalysts can be recycled and reused for several consecutive cycles without significant loss of activity.
- Cota, Iuliana,Medina, Francesc,Gonzalez-Olmos, Rafael,Iglesias, Miguel
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- Ionic liquid catalysed synthesis of β-hydroxy ketones
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Different acidic ionic liquids (ILs; namely, 1-methylimidazolium tetrafluoroborate, 1-methylimidazolium trifluoroacetate, N-methyl-2-pyrrolidone hydrogen sulfate, N,N,N-trioctyl-n-butanesulfonic acid ammonium hydrogen sulfate, 1-methyl-3-(3-sulfobutyl)imidazolium hydrogen sulfate) and basic ILs (namely, 1,1,3,3-tetramethylguanidinium lactate and choline hydroxide) were tested as catalysts for the aldol reaction. The choline hydroxide catalysed reaction gave high yield (94.3%) and selectivity of the 4-hydroxy-4-phenylbutan- 2-one after a short reaction time (15min) at 0°C. This article demonstrates the potential of choline hydroxide, which is a derivative of choline and a naturally occurring water-soluble essential nutrient, as a highly active and selective green catalyst.
- Karmee, Sanjib Kumar,Hanefeld, Ulf
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- Efficient solid-base catalysts for aldol reaction by optimizing the density and type of organoamine groups on nanoporous silica
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A highly efficient solid-base catalyst for aldol condensation reaction was synthesized by grafting site-isolated secondary amines onto the channel walls of mesoporous silica, MCM-41, in a polar-protic solvent. These site-isolated organoamines pair up with the neighboring residual surface silanol (weak acid) groups to form optimized acid and base groups, which cooperatively catalyze the aldol condensation reaction with high TON (turn over number) and selectivity (alcohol products over alkene products). The organoamine samples grafted in a polar-protic solvent, isopropanol, showed higher catalytic efficiency toward aldol reaction than those grafted in a non-polar solvent, toluene, because the former gave a sample with less dense loading of grafted organoamines (or more silanols present in it). To elucidate the role of surface silanols as acidic sites and their ability to activate the substrates in aldol condensation, control experiment with diethylamine as a homogeneous catalyst in the presence of MCM-41, silica microspheres, methyl-capped MCM-41 or methyl-capped catalyst was carried out. MCM-41 resulted in significant enhancement of catalytic activity compared to the corresponding reactions conducted in the absence of MCM-41, or in the presence of methyl-capped catalysts or silica spheres. By testing materials with different grafted organoamine groups as catalysts, we also found that secondary amine functionalized sample produced the best acid and base pairs and most efficient catalytic activity in aldol reaction. This was followed by primary amines, while the tertiary amine functionalized samples showed negligible catalytic property.
- Xie, Youwei,Sharma, Krishna K.,Anan, Abhishek,Wang, Gang,Biradar, Ankush V.,Asefa, Tewodros
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- Oxidation of fluoroalkyl alcohols using sodium hypochlorite pentahydrate [1]
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Fluoroalkyl alcohols are effectivity oxidized to the corresponding fluoroalkyl carbonyl compounds by reaction with sodium hypochlorite pentahydrate in acetonitrile in the presence of acid and nitroxyl radical catalysts. Although the reaction proceeded slower under a nitroxyl radical catalyst- free condition, the desired carbonyl compounds were obtained in high yields. For the reaction with fluoroalkyl allylic alcohols, the corresponding α,β-epoxyketone hydrates were obtained in high yields.
- Kirihara, Masayuki,Suzuki, Katsuya,Nakakura, Kana,Saito, Katsuya,Nakamura, Riho,Tujimoto, Kazuki,Sakamoto, Yugo,Kikkawa, You,Shimazu, Hideo,Kimura, Yoshikazu
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- Polysubstituted Indole Synthesis via Palladium/Norbornene Cooperative Catalysis of Oxime Esters
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Polysubstituted indoles are prevalent in pharmaceuticals, agrochemicals, and organic materials. Presented herein is the fact that polyfunctionalized indoles can be efficiently constructed from easily accessible oxime esters and aryl iodides, involving a palladium/norbornene synergistic synthesis. The reaction is enabled by a unique class of electrophiles in palladium/norbornene cooperative catalysis, which are oxime esters derived from simple ketone. The broad substrate scope and high functional group tolerance could make this method attractive for the synthesis of polysubstituted indoles.
- Huang, Liangbin,Jiang, Huanfeng,Lin, Haojiang,Liu, Jiechun
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supporting information
(2022/01/20)
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- Inhibition of Autophagy by a Small Molecule through Covalent Modification of the LC3 Protein
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The autophagic ubiquitin-like protein LC3 functions through interactions with LC3-interaction regions (LIRs) of other autophagy proteins, including autophagy receptors, which stands out as a promising protein–protein interaction (PPI) target for the intervention of autophagy. Post-translational modifications like acetylation of Lys49 on the LIR-interacting surface could disrupt the interaction, offering an opportunity to design covalent small molecules interfering with the interface. Through screening covalent compounds, we discovered a small molecule modulator of LC3A/B that covalently modifies LC3A/B protein at Lys49. Activity-based protein profiling (ABPP) based evaluations reveal that a derivative molecule DC-LC3in-D5 exhibits a potent covalent reactivity and selectivity to LC3A/B in HeLa cells. DC-LC3in-D5 compromises LC3B lipidation in vitro and in HeLa cells, leading to deficiency in the formation of autophagic structures and autophagic substrate degradation. DC-LC3in-D5 could serve as a powerful tool for autophagy research as well as for therapeutic interventions.
- Chen, Kaixian,Chen, Zhifeng,Dang, Yongjun,Ding, Hong,Fan, Shijie,Hu, Junchi,Jiang, Hualiang,Li, Lianchun,Li, Quanfu,Lin, Tingting,Lu, Junyan,Luo, Cheng,Otomo, Chinatsu,Otomo, Takanori,Tan, Minjia,Tao, Hongru,Wan, Wei,Wen, Yi,Xie, Yuli,Xu, Pan,Yao, Zhiyi,Yue, Liyan,Zhang, Bidong,Zhang, Naixia,Zhang, Yuanyuan,Zhou, Bing,Zhu, Mingrui
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supporting information
p. 26105 - 26114
(2021/11/09)
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- Highly tunable selectivity to benzaldehyde over Pd/ZrO2 catalysts in Oppenauer oxidation of benzyl alcohol using acetone as H-acceptor
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The development of novel bifunctional catalysts with high selectivity is the key to achieving the goals of sustainable chemical synthesis. Here, we report the synthesis of mesoporous zirconia and transition metal-doped zirconia by inverse micelle approach. Also, meso-zirconia supported Pd nanocatalysts via the deposition-precipitation method. Highly crystalline Pd/ZrO2 nanoparticles were formed, as evidenced in the pXRD and TEM analyses. The acid-base quantification was investigated using TPD-NH3 and TPD-CO2. Interestingly, the integration of the intrinsic chemical properties of the multi-component catalyst is significant in tailoring the catalytic activities. Interactions between the adsorbates and the moderate acid-base pair sites rather than a single dominating acid or base site mediate the higher selectivity for the aldehyde product. The 100 % chemoselectivity to benzaldehyde is ascribed to the strong synergy between Pd-Zr, which generated the moderate acid-base property. The Pd/ZrO2 is reusable, with selectivity retained after ten cycles.
- Akinnawo, Christianah Aarinola,Maheso, Dimakatso Jeannett,Bingwa, Ndzondelelo,Meijboom, Reinout
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- Clean protocol for deoxygenation of epoxides to alkenes: Via catalytic hydrogenation using gold
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The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is
- Fiorio, Jhonatan L.,Rossi, Liane M.
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p. 312 - 318
(2021/01/29)
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- Overcoming Kinetic and Thermodynamic Challenges of Classic Cope Rearrangements
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Systematic evaluation of 1,5-dienes bearing 3,3-electron-withdrawing groups and 4-methylation results in the discovery of a Cope rearrangement for Meldrum's acid-containing substrates that have unexpectedly favorable kinetic and thermodynamic profiles. The protocol is quite general due to a concise and convergent synthesis from abundant starting materials. Furthermore, products with an embedded Meldrum's acid moiety are prepared, which, in turn, can yield complex amides under neutral conditions. We have now expanded the scope of the reductive Cope rearrangement, which, via chemoselective reduction, can promote thermodynamically unfavorable [3,3] sigmatropic rearrangements of 3,3-dicyano-1,5-dienes to form reduced Cope rearrangement products. The Cope rearrangement is found to be stereospecific and can yield enantioenriched building blocks when chiral, nonracemic 1,3-disubstituted allylic electrophiles are utilized. We expand further the use of Cope rearrangements for the synthesis of highly valuable building blocks for complex- and drug-like molecular synthesis.
- Fereyduni, Ehsan,Lahtigui, Ouidad,Sanders, Jacob N.,Tomiczek, Breanna M.,Mannchen, Michael D.,Yu, Roland A.,Houk,Grenning, Alexander J.
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p. 2632 - 2643
(2021/02/05)
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- Iodine/water-mediated deprotective oxidation of allylic ethers to access α,β-unsaturated ketones and aldehydes
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The first iodine/water-mediated deprotective oxidation of allylic ethers to access α,β-unsaturated ketones and aldehydes was achieved. The reaction tolerates a wide range of functionalities. Furthermore, this protocol was found to be applicable to the oxidative transformation of allylic acetates. The proposed mechanism involves an oxygen transfer from solvent water to the carbonyl products.
- Chen, Weifeng,Jiang, Kezhi,Xue, Yuntian,Yan, Yaolong,Yang, Lei
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p. 14720 - 14724
(2020/04/27)
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- Selective Cross-Dehydrogenative C(sp3)-H Arylation with Arenes
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Selective C(sp3)-C(sp2) bond construction is of central interest in chemical synthesis. Despite the success of classic cross-coupling reactions, the cross-dehydrogenative coupling between inert C(sp3)-H and C(sp2)-H bonds represents an attractive alternative toward new C(sp3)-C(sp2) bonds. Herein, we establish a selective inter-and intramolecular C(sp3)-H arylation of alcohols with nondirected arenes that thereby provides a general pathway to access a wide range of β-arylated alcohols, including tetrahydronaphthalen-2-ols and benzopyran-3-ols, with high to excellent chemo-and regioselectivity.
- Hao, Hong-Yan,Mao, Yang-Jie,Xu, Zhen-Yuan,Lou, Shao-Jie,Xu, Dan-Qian
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supporting information
p. 2396 - 2402
(2020/03/13)
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- Iron(ii)-folded single-chain nanoparticles: a metalloenzyme mimicking sustainable catalyst for highly enantioselective sulfa-Michael addition in water
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Metalloenzyme is a source of inspiration for chemists who attempt to create versatile synthetic catalysts for aqueous catalysis. Herein, we impart metalloenzyme-like characteristics to a chiral FeII-oxazoline complex by incorporating an Fe(ii) ion into a chiral oxazoline-containing discrete self-folded polymer, to realize highly enantioselective sulfa-Michael addition (SMA) in water. Intrachain FeII-oxazoline complexation together with hydrophobic interactions triggers the self-folding of the oxazoline-containing single polymeric chain in water. The formed FeII-folded single-chain polymeric nanoparticles (SCPNs) significantly accelerate the aqueous asymmetric SMA reaction via a self-folded hydrophobic compartment around the catalytic sites, reminiscent of metalloenzymatic catalysis. In addition, they can be facilely recovered for reuse by simple thermo-controlled separation due to their thermo-responsive properties. Such metallo-folded SCPNs combine the benefits of transition metal- and bio-catalyst, and avoid the tedious procedures of separation, which is a benefit for energy-saving and industrial applications.
- Li, Chaoping,Li, Shiye,Tan, Rong,Wang, Jiajun,Wang, Weiying,Yin, Donghong
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supporting information
p. 4645 - 4655
(2020/08/10)
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- β-Carbolines: synthesis of harmane, harmine alkaloids and their structural analogs by thermolysis of 4-aryl-3-azidopyridines and investigation of their optical properties
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[Figure not available: see fulltext.] Interest in β-carbolines is caused by the biological activity of these compounds and the use of their fluorescent properties in the study of their interaction with DNA and other biological targets, as well as with drug delivery vehicles. A new general method for the synthesis of harmane, harmine, and their structural analogs by thermolysis of substituted 4-aryl-3-azidopyridines was developed, and their optical properties were studied.
- Shuvalov, Vladislav Yu.,Elisheva, Valeriya А.,Belousova, Anastasiya S.,Arshinov, Evgenii V.,Glyzdinskaya, Larisa V.,Vorontsova, Marina А.,Chernenko, Sergei А.,Fisyuk, Aleksander S.,Sagitullina, Galina P.
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- Synthesis and biological evaluations of monocarbonyl curcumin inspired pyrazole analogues as potential anti-colon cancer agent
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Purpose: The monocarbonyl analogs of curcumin (MCACs) have been widely studied for their promising antitumor activity. Pyrazole is a five-membered aromatic heterocyclic system with various bioactivities incorporated frequently in drugs. However, few of MCACs inspired pyrazole analogues were investigated. To search for more potent cytotoxic agents based on MCACs, a series of new 1,5-diaryl/heteroaryl-1,4-pentadien-3-ones inspired pyrazole moiety was synthesized and evaluated on their anti-colon cancer activities. Methods: Fifteen new compounds were synthesized and characterized by spectral datum, and then they were tested preliminarily by MTT assay for their cytotoxic activities against a panel of four human cancer cell lines, namely, gastric (SGC-7901), liver (HepG2), lung (A549), and colon (SW620) cancer cells. Compound 7h exhibited excellent selectivity and outstanding anti-proliferation activity against SW620 cells among these 15 compounds. Further, the mechanisms were investigated by transwell migration and invasion assay, clonogenic assay, cell apoptosis analysis, cell cycle analysis, Western blot analysis. Results: The IC50 value of 7h against SW620 cells was 12 nM, being more potent than curcumin (IC50 = 9.36 μM), adriamysin (IC50 = 3.28 μM) and oxaliplatin (IC50 = 13.33 μM). Further assays showed that 7h inhibited SW620 cell migration, invasion and colony formation obviously, which was due to its ability to induce cell cycle arrest in the G2/M and S phases and apoptosis. Western blot assay revealed that 7h decreased the protein expression of ATM gene, which may primarily contribute to its anticancer activity against SW620 cells. Conclusion: A new MCACs 7h was synthesized and found to exhibit excellent anti-proliferation activity against SW620 cells. Further studies indicated that 7h exerted its anticancer activity against SW620 cells probably via decreasing the ATM protein expression. The present study suggested that 7h was a promising candidate as an anti-colon cancer drug for future development.
- Hong, Xing,Hu, Xiamin,Min, Zhenli,Ye, Min,Yu, Zhijun,Yuan, Qiong,Zhu, Yue
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p. 2517 - 2534
(2020/07/04)
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- Design, synthesis and biological evaluation of novel diaryl pyrazole derivatives as anticancer agents
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Cancer is one of the major causes of mortality all around the world. Globally, nearly 1 in 6 deaths is due to cancer. Researchers are trying to synthesize new anticancer agents. Previous studies demonstrated that some pyrazole derivatives could be considered as potential anticancer agents. Herein, ten novel derivatives of 1,5-diarylpyrazole were synthesized in four step reactions and cytotoxic activity was investigated by MTT cell viability assay. All of the compounds were characterized by1H NMR and13C NMR and their purity was confirmed by elemental analysis. The cytotoxicity was determined against three cancerous cell lines (HT-29, U87MG and MDA-MB 468) and AGO1522 as a normal cell line. Compound 5a showed the best cytotoxic activity on cancerous cell lines in comparison to paclitaxel. Annexin V/ PI staining assay also showed that compounds 5a and 5i would lead to significant apoptosis induction in MDA-MB 486 cell line.
- Nourmahammadi, Jalal,Moghadam, Ebrahim Saeedian,Shahsavari, Zahra,Amini, Mohsen
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p. 216 - 223
(2020/02/29)
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- A bioinspired microreactor with interfacial regulation for maximizing selectivity in a catalytic reaction
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We report a bioinspired emulsion microreactor composed of an electrical double layer to mimic the functions of cell membranes. This "artificial cell"can modulate the phase-oriented transport of reagents at the oil-liquid interface via the electrical double layer, affording a powerful tool to optimize the selectivity in a catalytic reaction. This journal is
- Han, Chenhui,Li, Xin-Hao,Waclawik, Eric R.,Xu, Haolan,Xu, Jingsan
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p. 8059 - 8062
(2020/09/09)
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- Photoredox β-thiol-α-carbonylation of enones accompanied by unexpected Csp2-C(CO) bond cleavage
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An olefinic difunctionalization method of enones was presented hereviaaerobic visible-light catalysis. A novel reactivity was showcased in conjunction with the selective Csp2-C(CO) bond activation of enones, which provided a convenient method for the preparation of various β-thiolated-α-functionalized compounds. Moreover, the preliminary investigation of the mechanism indicated that a β-peroxysulfide intermediate was formed under the promotion of visible light under an oxygen atmosphere, which finally induced the unexpected C-C bond cleavage.
- Du, Ding,Feng, Jie,Ma, Rui,Zhang, Beichen,Zhang, Kuili
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supporting information
p. 7549 - 7553
(2020/10/13)
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- Bioinspired CNP Iron(II) Pincers Relevant to [Fe]-Hydrogenase (Hmd): Effect of Dicarbonyl versus Monocarbonyl Motifs in H2 Activation and Transfer Hydrogenation
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A set of bioinspired carbamoyl CNP pincer complexes are reported that are relevant to [Fe]-hydrogenase (Hmd). The dicarbonyl species [(CNHNNHPR2)Fe(CO)2I] [R = Ph, 1; R = iPr, 2] undergoes ligand deprotonation, resulting in the dearomatized complexes of formulas [(CNHNN=PR2)Fe(CO)2] (5 and 6). The crystal structure and 1H{31P} NMR spectroscopy of the iodide-bound dearomatized species [Na(18-crown-6)][(CNHNN=PPh2)Fe(CO)2I] (7) showed that the deprotonated moiety was the phosphoramine N(H) linkage. Separately, the monocarbonyl complexes [(CNHNNHPR2)Fe(CO)(MeCN)2](BF4) (8 and 9) synthesized, as well as deprotonated and dearomatized in similar fashion. Reactivity studies revealed that the parent dicarbonyl complexes require more forceful conditions for H2 activation, compared with the monocarbonyl complexes. The ligand backbone was not found to participate in H2 activation and H2 → hydride transfer to an organic substrate was not observed in either case. Density functional theory calculations revealed that the higher reactivity of the monocarbonyl complex in H2 splitting could be attributed to its higher affinity for H2. This behavior is attributed to two key points related to the requisite dI(Fe) → σ*(H2) back-bonding interaction in a conventional M-H2 Kubas interaction: (i) generally, the weaker πdonor capacity of the dicarbonyls, and (ii) specifically, the detrimental effect of a strongly πacidic CO ligand (versus weakly πacidic MeCN ligand) trans to the H2 activation site. The higher reactivity of the monocarbonyl complex is also evidenced by the catalytic transfer hydrogenation by monocarbonyl 8, whereas dicarbonyl 1 was ineffective. Overall, the results suggest that Nature uses the dicarbonyl motif in [Fe]-hydrogenase to diminish the interaction between the Fe center and dihydrogen, thereby preventing premature H2 activation prior to substrate (H4MPT+) binding and any resulting nonspecific hydride transfer reactivity.
- Chai, Wenrui,Henkelman, Graeme A.,Kerns, Spencer A.,Rose, Michael J.,Xie, Zhu-Lin
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supporting information
(2020/02/22)
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- PdBr2-Catalyzed Acetal Formation of Carbonyl Compounds Using Diazophenanthrenequinone: Utility of 9,10-Phenanthrenedioxyacetal
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We developed a new acetalization method of ketones and aldehydes under non-acidic conditions using diazophenanthrenequinone and PdBr2. The formed acetals that have a phenanthrene skeleton withstand under mild acidic conditions. Removal of acetals was successfully proceeded under strong acidic or oxidation conditions using aqueous ceric ammonium nitrate (CAN) to afford corresponding ketones and aldehydes.
- Kitamura, Mitsuru,Fujimura, Ryo,Nishimura, Tomoaki,Takahashi, Shuhei,Shimooka, Hirokazu,Okauchi, Tatsuo
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supporting information
p. 5319 - 5322
(2020/06/10)
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- The construction of novel and efficient hafnium catalysts using naturally existing tannic acid for Meerwein-Ponndorf-Verley reduction
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The conversion of carbonyl compounds into alcohols or their derivatives via the catalytic transfer hydrogenation (CTH) process known as Meerwein-Ponndorf-Verley reduction is an important reaction in the reaction chain involved in biomass transformation. The rational design of efficient catalysts using natural and renewable materials is critical for decreasing the catalyst cost and for the sustainable supply of raw materials during catalyst preparation. In this study, a novel hafnium-based catalyst was constructed using naturally existing tannic acid as the ligand. The prepared hafnium-tannic acid (Hf-TA) catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry (TG). Hf-TA was applied in the conversion of furfuraldehyde (FD) to furfuryl alcohol (FA) using isopropanol (2-PrOH) as both the reaction solvent and the hydrogen source. Both preparation conditions and the effects of the reaction parameters on the performance of the catalyst were studied. Under the relatively mild reaction conditions of 70 °C and 3 h, FD (1 mmol) could be converted into FA with a high yield of 99.0%. In addition, the Hf-TA catalyst could be reused at least ten times without a notable decrease in activity and selectivity, indicating its excellent stability. It was proved that Hf-TA could also catalyze the conversion of various carbonyl compounds with different structures. The high efficiency, natural occurrence of tannic acid, and facile preparation process make Hf-TA a potential catalyst for applications in the biomass conversion field.
- Deng, Lijuan,Hao, Jianxiu,He, Runxia,Li, Na,Liu, Quansheng,Wang, Xiaolu,Zhao, Hongye,Zhi, Keduan,Zhou, Huacong
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p. 6944 - 6952
(2020/03/03)
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- RhIII-Catalyzed Synthesis of Highly Substituted 2-Pyridones using Fluorinated Diazomalonate
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A RhIII-catalyzed strategy was developed for the rapid construction of highly substituted 2-pyridone scaffolds using α,β-unsaturated oximes and fluorinated diazomalonate. The reaction proceeds through direct, site-selective alkylation based on migratory insertion and subsequent cyclocondensation. A wide substrate scope with different functional groups was explored. The requirement of fluorinated diazomalonate was explored for this transformation. The developed methodology was further extended with the synthesis of the bioactive compound.
- Das, Debapratim,Sahoo, Gopal,Biswas, Aniruddha,Samanta, Rajarshi
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p. 360 - 364
(2020/01/25)
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- Heck Reactions of Acrolein or Enones and Aryl Bromides – Synthesis of 3-Aryl Propenals or Propenones and Consecutive Application in Multicomponent Pyrazole Syntheses
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3-(Hetero)aryl propenals or propenones are efficiently prepared by a Heck reaction of (hetero)aryl bromides and acrolein or vinyl ketones using Beller's CataCXium Ptb ligand under Jeffery's and Fu's conditions. The formation of these three-carbon building blocks is embedded into consecutive three- and pseudo-four-component syntheses of 3-(hetero)aryl and 3,5-diarylpyrazoles with a broad substitution pattern in moderate to excellent yield.
- Stephan, Marvin,Panther, Jesco,Wilbert, Fabio,Ozog, Pauline,Müller, Thomas J. J.
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supporting information
p. 2086 - 2092
(2020/03/23)
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- Copper(I)- and Mesoionic-Hydroxyamide-Catalyzed Chemoselective Aerobic Oxidation of Primary Benzylic Alcohols
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A new aerobic oxidation system consisting of Cu(I)I, 2,2'-bipyridine, N -methyl imidazole, and a mesoionic hydroxyamide was developed, with which selective oxidation of a broad range of benzylic alcohols was achieved.
- Matsukawa, Yuta,Hirashita, Tsunehisa
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p. 315 - 318
(2019/02/12)
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- Use of a switchable-hydrophilicity solvent as both a solvent and a catalyst in aldol condensation
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A switchable-hydrophilicity solvent, N,N-dimethylcyclohexylamine, was used as a recyclable catalyst and solvent for aldol condensation, giving >97% pure product in 94% isolated yield without the need for purification or additional solvents. CO2-triggered separation produced yields greater than conventional workup and allowed facile recycling of the amine.
- Poole, Hailey,Gauthier, Jeremy,Vanderveen, Jesse R.,Jessop, Philip G.,Lee, Roland
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supporting information
p. 6263 - 6267
(2019/12/03)
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- Method for synthesizing 4-phenyl-3-butenone
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The invention relates to a method for synthesizing 4-phenyl-3-butenone, and belongs to the technical field of preparation of organic compounds. A p-tert-butylcalixarene potassium (sodium) salt servesas a catalyst, raw materials, including benzaldehyde and acetone, are synthesized into the 4-phenyl-3-butenone, and the p-tert-butylcalixarene potassium (sodium) salt can be reused for multiple times.According to the method, the p-tert-butylcalixarene potassium (sodium) salt is formed by a reaction among p-tert-butylcalix[6]arene or p-tert-butylcalix[4]arene, NaOH and KOH, the consumption of thep-tert-butylcalixarene potassium (sodium) salt accounts for 0.01-5% of the amount of substance of the acetone, the amount-of-substance ratio of the benzaldehyde to the acetone ranges from 1:1 to 1:3,the reaction temperature is 20-56 DEG C, and the reaction time is 0.2-2 hours. The reaction process does not require solvents, thereby being a green chemical process. After reaction, the product is easily separated from the catalyst. The method has the advantages of mild reaction condition, simple process, high yield, environmental friendliness and low cost, thereby being suitable for industrial production.
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Paragraph 0007; 0010-0011
(2019/08/20)
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- Naphtho[2,3-: B] furan-4,9-dione synthesis via palladium-catalyzed reverse hydrogenolysis
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A reverse hydrogenolysis process has been developed for two-site coupling of 2-hydroxy-1,4-naphthoquinones with olefins to produce naphtha[2,3-b]furan-4,9-diones and hydrogen (H2). The reaction is catalyzed by commercially available Pd/C without oxidants and hydrogen acceptors, thereby providing an intrinsically waste-free approach for the synthesis of functionalized and potentially biologically relevant naphtha[2,3-b]furan-4,9-diones.
- Li, Jimei,Zhang, Jie,Li, Mingfei,Zhang, Chenyang,Yuan, Yongkun,Liu, Renhua
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supporting information
p. 2348 - 2351
(2019/02/27)
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- Application of Polyphosphoric Acid-Mediated Acyl Migration for Regiospecific Synthesis of Diverse 2-Acylpyrroles from Chalcones
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A metal-free approach for the synthesis of 2-acylpyrroles is reported in this paper. Synthesis of the target molecule started from chalcones and was carried out in two steps. Initial step involved the conversion of chalcones to corresponding 4-substituted-3-acylpyrroles by reaction with TosMIC. In the subsequent step, target molecules were obtained in modest to good yields by polyphosphoric acid-mediated acyl rearrangement of 3-acylpyrroles to their 2-acyl congeners. The crucial final step was amenable to diverse substitutions on pyrrole ring. Preliminary experiment for the determination of mechanism indicated the involvement of acylium ion.
- Kumar, Togiti Uday,Thigulla, Yadagiri,Rangan, Krishnan,Bhattacharya, Anupam
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supporting information
p. 1283 - 1290
(2019/03/07)
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- Proton-Coupled Electron Transfer: Transition-Metal-Free Selective Reduction of Chalcones and Alkynes Using Xanthate/Formic Acid
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Highly chemoselective reduction of α,β-unsaturated ketones to saturated ketones and stereoselective reduction of alkynes to (E)-alkenes has been developed under a transition-metal-free condition using a xanthate/formic acid mixture through proton-coupled electron transfer (PCET). Mechanistic experiments and DFT calculations support the possibility of a concerted proton electron-transfer (CPET) pathway. This Birch-type reduction demonstrates that a small nucleophilic organic molecule can be used as a single electron-transfer (SET) reducing agent with a proper proton source.
- Prasanna, Ramanathan,Guha, Somraj,Sekar, Govindasamy
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supporting information
p. 2650 - 2653
(2019/04/17)
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- Chiral Hydroxytetraphenylene-Catalyzed Asymmetric Conjugate Addition of Boronic Acids to Enones
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(S)-2,15-Br2-DHTP-catalyzed asymmetric conjugate addition of boronic acids to β-trifluoromethyl α,β-unsaturated ketones and enones was studied. The reaction afforded the corresponding Michael addition products in moderate to high yields with excellent enantioselectivities (up to 99:1 er). This catalytic system features mild reaction conditions, high efficiency, and tolerance to heteroarylboronic acids.
- Chai, Guo-Li,Sun, A-Qiang,Zhai, Dong,Wang, Juan,Deng, Wei-Qiao,Wong, Henry N.C.,Chang, Junbiao
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supporting information
p. 5040 - 5045
(2019/07/03)
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- Construction of Multiple-Substituted Chiral Cyclohexanes through Hydrogenative Desymmetrization of 2,2,5-Trisubstituted 1,3-Cyclohexanediones
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The construction of chiral multiple-substituted cyclohexanes motifs is a challenging topic in organic synthesis. By the combination of desymmetrization and remote stereocontrol, a ruthenium-catalyzed transfer hydrogenative desymmetrization of 2,2,5-trisubstituted 1,3-cyclohexanediones has been successfully developed for the construction of chiral multiple-substituted cyclohexanes with high enantioselectivity and diastereoselectivity. When an ester group was introduced to the two-position, a hydrogenative desymmetrization/transesterification cascade occurred, affording the bicyclic lactones bearing three stereocenters, including two discrete stereocenters and one quaternary stereogenic center, with high enantioselectivity. The products are the multiple-substituted chiral cyclohexanes bearing the hydroxyl and carbonyl functional groups, which provide a new opportunity for further precise elaboration.
- Yu, Chang-Bin,Song, Bo,Chen, Mu-Wang,Shen, Hong-Qiang,Zhou, Yong-Gui
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supporting information
p. 9401 - 9404
(2019/11/28)
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- Silver(i)-catalysed carboxylative cyclisation of primary propargylic amines in neat water using potassium bicarbonate as a carboxyl source: An environment-friendly synthesis of: Z -5-alkylidene-1,3-oxazolidin-2-ones
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Herein, we report a mild and environment-friendly synthesis of Z-5-alkylidene-2-oxazolidinones in neat water, using a low loading (2 mol%) of silver carbonate as a catalyst. Instead of pressurised gaseous carbon dioxide, potassium bicarbonate was used as the source of carboxyl. An interesting solvent effect and a C-N cleavage side reaction with a 6-endo-dig mechanism are also discussed.
- Qin, Jian-Feng,Wang, Bing,Lin, Guo-Qiang
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supporting information
p. 4656 - 4661
(2019/09/09)
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- Palladium-Catalyzed Synthesis of β,β-Diaryl α,β-Unsaturated Ketones
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We herein describe a versatile palladium-catalyzed synthesis of β,β-diaryl α,β-unsaturated ketones. A broad range of aryl halides react with β-arylbutanones to afford biologically useful, symmetrical and unsymmetrical ketones. The use of 4,5-diazafluoren-9-one and oxygen makes this one-pot reaction more applicable. A plausible mechanism involving palladium-catalyzed oxidative Heck-type cross-coupling is also proposed.
- Zheng, Yi-Lin,Xiao, Li,Xie, Qiong,Shao, Li-Ming
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p. 1455 - 1465
(2019/03/07)
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- Dehydrozingerone derivative and preparation method and application thereof
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The invention provides a dehydrozingerone derivative as shown in the description. R-R are each independently selected from hydrogen or halogen or a nitro group or an alkyl group or a substitutedalkoxy group or an alkoxy group or a hydroxyl group; the substituent in the substituted alkoxy group is selected from one or multiple of halogen, a nitro group and a hydroxyl group; R and R areeach independently selected from hydrogen or halogen or nitrogen-containing heterocycle; R is selected from an alkyl group or an alkoxy group or a substituted alkoxy group; the substituent in thesubstituted alkyl group is selected from one or multiple of halogen, a nitro group and a hydroxyl group; X is selected from a hetero atom or a hydroxylamine group. The dehydrozingerone derivative hasbroad-spectrum activity against plant pathogenic fungi and bacteria, and has certain nematicidal activity, and is a lead compound with the broad biological activity.
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Paragraph 0084-0087; 0088; 0099
(2019/11/20)
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- Mild Chemoenzymatic Oxidation of Allylic sec-Alcohols. Application to Biocatalytic Stereoselective Redox Isomerizations
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The design of catalytic oxidative methodologies in aqueous medium under mild reaction conditions and using molecular oxygen as final electron acceptor represents a suitable alternative to the traditional oxidative transformations. These methods are especially relevant if other functionalities that can be oxidized are present within the same molecule, as in the case of allylic alcohols. Herein we apply a simple chemoenzymatic system composed of the laccase from Trametes versicolor and 2,2,6,6-tetramethylpiperidinyloxy radical (TEMPO) to oxidize a series of racemic allylic sec-alcohols into the corresponding α,β-unsaturated ketones. Afterward, these compounds react with different commercially available ene-reductases to afford the corresponding saturated ketones. Remarkably, in the case of trisubstituted alkenes, the bioreduction reaction occurred with high stereoselectivity. Overall, a bienzymatic one-pot two-step sequential strategy has been described with respect to the synthesis of saturated ketones starting from racemic allylic alcohols, thus resembling the metal-catalyzed redox isomerizations of these derivatives that have been previously reported in the literature.
- Martínez-Montero, Lía,Gotor, Vicente,Gotor-Fernández, Vicente,Lavandera, Iván
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p. 2413 - 2419
(2018/03/13)
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- Thiol Treatment Creates Selective Palladium Catalysts for Semihydrogenation of Internal Alkynes
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Surface and interfacial engineering of heterogeneous metal catalysts is effective and critical for optimizing selective hydrogenation for fine chemicals. By using thiol-treated ultrathin Pd nanosheets as a model catalyst, we demonstrate the development of stable, efficient, and selective Pd catalysts for semihydrogenation of internal alkynes. In the hydrogenation of 1-phenyl-1-propyne, the thiol-treated Pd nanosheets exhibited excellent catalytic selectivity (>97%) toward the semihydrogenation product (1-phenyl-1-propene). The catalyst was highly stable and showed no obvious decay in either activity or selectivity for over ten cycles. Systematic studies demonstrated that a unique Pd-sulfide/thiolate interface created by the thiol treatment was crucial to the semihydrogenation. The high catalytic selectivity and activity benefited from the combined steric and electronic effects that inhibited the deeper hydrogenation of C=C bonds. More importantly, this thiol treatment strategy is applicable to creating highly active and selective practical catalysts from commercial Pd/C catalysts for semihydrogenation of internal alkynes. The development of next-generation catalytic materials requires a methodological shift from trial-and-error to mechanism-directed design. It is highly desirable to build model catalyst systems with simplified structures to ensure maximized utilization of both state-of-the-art characterization tools and computational chemistry methods. In this work, thiol-treated palladium nanosheets are adopted as a model catalyst for the selective semihydrogenation of internal alkynes. Unexpectedly, thiol treatment created highly selective palladium catalysts with high activity toward the semihydrogenation reaction. The ultrathin nature of the as-prepared catalysts allows for the application of a variety of surface science and computational methods to resolve the complexity of metal-organic interfaces and thus elucidate the underlying mechanism. Driven by atomic-level understanding, we have realized practical, lead-free catalysts for semihydrogenation. Thiol treatment is demonstrated as a highly effective strategy for promoting the catalytic selectivity of Pd nanocatalysts in the hydrogenation of internal alkynes to alkenes.
- Zhao, Xiaojing,Zhou, Lingyun,Zhang, Wuyong,Hu, Chengyi,Dai, Lei,Ren, Liting,Wu, Binghui,Fu, Gang,Zheng, Nanfeng
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supporting information
p. 1080 - 1091
(2018/04/30)
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- Boehmite - An efficient and recyclable acid-base bifunctional catalyst for aldol condensation reaction
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In this work boehmite was used as an acid-base bifunctional catalyst for aldol condensation reactions of aromatic aldehydes and ketones. The catalyst was prepared by simple sol-gel method using Al(NO3)3 · 9H2O and NH4OH as precursors. The catalyst has been characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), UV-visible spectroscopy (DRS), BET surface area analyses. Boehmite is successfully applied as catalyst for the condensation reaction between 4-nitrobenzaldehyde and acetone as a model substrate giving α,β-unsaturated ketones without any side product. The scope of the reaction is extended for various substituted aldehydes. A probable mechanism has been suggested to explain the cooperative behavior of the acidic and basic sites. The catalyst is environmentally friendly and easily recovered from the reaction mixture. Also the catalyst is reusable up to 3 catalytic cycles.
- Reshma, P.C. Rajan,Vikneshvaran, Sekar,Velmathi, Sivan
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p. 4270 - 4275
(2018/01/11)
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- New selective cyclooxygenase-2 inhibitors from cyclocoumarol: Synthesis, characterization, biological evaluation and molecular modeling
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In this work, a serie of cyclocoumarol derivatives was designed, synthesized, characterized and studied for their potentialities as selective inhibitors of COX-2. All target compounds have been screened for their anti-inflammatory activity by the assay of PGE2 production. Among them, compound 5d exhibited the most potent inhibitory activity with a PGE2 inhibition compared to NS-398 (79% and 88% respectively) and showed non-inhibitory activity towards the COX-1 enzyme. Docking studies revealed the capacity of this compound to occupy the selective COX-2 cavity establishing additional hydrogen bonds between the oxygen of the methoxy group and the His90 and Arg513 of the binding site of the enzyme.
- Rayar, Anita Marie,Lagarde, Nathalie,Martin, Frederique,Blanchard, Florent,Liagre, Bertrand,Ferroud, Clotilde,Zagury, Jean-Fran?ois,Montes, Matthieu,Sylla-Iyarreta Veitía, Maité
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p. 577 - 587
(2018/02/10)
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- Evaluation of sulphonamide derivatives acting as inhibitors of human carbonic anhydrase isoforms I, II and Mycobacterium tuberculosis β-class enzyme Rv3273
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A series of novel sulphonamide derivatives was obtained from sulphanilamide which was N4-alkylated with ethyl bromoacetate followed by reaction with hydrazine hydrate. The hydrazide obtained was further reacted with various aromatic aldehydes. The novel sulphonamides were characterised by infrared, mass spectrometry, 1H- and 13C-NMR and purity was determined by high-performance liquid chromatography (HPLC). Human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA I and II and Mycobacterium tuberculosis β-CA encoded by the gene Rv3273 (mtCA 3) inhibition activity was investigated with the synthesised compounds which showed promising inhibition. The KIs were in the range of 54.6 nM–1.8 μM against hCA I, in the range of 32.1 nM–5.5 μM against hCA II and of 127 nM–2.12 μM against mtCA 3.
- Wani, Tanvi V.,Bua, Silvia,Khude, Pravin S.,Chowdhary, Abdul H.,Supuran, Claudiu T.,Toraskar, Mrunmayee P.
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p. 962 - 971
(2018/05/29)
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- Cascade Reaction by Chemo- and Biocatalytic Approaches to Obtain Chiral Hydroxy Ketones and anti 1,3-Diols
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A chemo- and biocatalytic cascade approach was applied for the stereoselective synthesis of hydroxy ketones and the corresponding 1,3-diols. A new class of tridentate N,N,O ligands was used with copper(II) complexes for the asymmetric β-borylation of α,β-unsaturated compounds. The complex containing ligand L5 emerged as the best performer, and it gave the organoborane derivatives with good ee values. The corresponding keto–alcohol compounds were then bioreduced by yeasts. The biotransformation set up with Rhodotorula rubra allowed (R)-keto–alcohols and (S,S)-diols to be obtained with up to 99 % ee and up to 99 % de in favor of the anti enantiomers.
- Gandolfi, Raffaella,Facchetti, Giorgio,Christodoulou, Michael S.,Fusè, Marco,Meneghetti, Fiorella,Rimoldi, Isabella
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p. 393 - 400
(2018/06/04)
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- Rh(III)-Catalyzed Enaminone-Directed Alkenyl C-H Activation for the Synthesis of Salicylaldehydes
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A Rh(III)-catalyzed enaminone-directed alkenyl C-H coupling with alkynes for the synthesis of salicylaldehyde derivatives is reported. This represents a unique example of benzene ring framework formation through a transition-metal-catalyzed, directed C-H activation strategy. The two incorporated reactive functionalities, aldehyde and hydroxy groups, provide convenient synthetic handles for further structural elaboration.
- Qi, Bing,Guo, Shan,Zhang, Wenjing,Yu, Xiaolong,Song, Chao,Zhu, Jin
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supporting information
p. 3996 - 3999
(2018/07/15)
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- Trans -Hydroboration vs. 1,2-reduction: Divergent reactivity of ynones and ynoates in Lewis-base-catalyzed reactions with pinacolborane
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Ynones and ynoates react with pinacolborane in a divergent manner in the presence of nucleophilic phosphine catalysts. Ynones are transformed to the corresponding propargyl alcohols in good yields with high regio- and chemoselectivity. Ynoates undergo highly regio- and stereoselective trans-hydroboration to produce E-vinylboronates. Impressive divergence in reactivity of ynones and ynoates can be traced back to the mechanistic aspects of 1,2-reduction and trans-hydroboration. A comparative analysis of the two pathways paints a complex picture in which different reaction rates control selectivity in these seemingly unrelated processes and explains how sufficiently acidic protons in the reaction mixtures can be used to steer the selectivity in different directions.
- Zi, You,Sch?mberg, Fritz,Seifert, Fabian,G?rls, Helmar,Vilotijevic, Ivan
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p. 6341 - 6349
(2018/09/10)
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- Diastereoselective synthesis of β-amino ketone and acid derivatives by palladium-catalyzed conjugate addition
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The first diastereoselective synthesis of β-amino ketone and β-amino acid derivatives by palladium-catalyzed conjugate addition of arylboronic acids to chiral β-enamino ketones and β-enamino esters is reported. The catalytic system employing (S)-4-(tert-butyl)oxazolidin-2-one as the chiral auxiliary in water under an air atmosphere provides β-amino ketone and β-amino acid derivatives in high yields with excellent diastereoselectivity.
- Zhi, Wubin,Li, Jingya,Zou, Dapeng,Wu, Yangjie,Wu, Yusheng
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supporting information
p. 2736 - 2740
(2018/06/25)
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- Two efficient pathways for the synthesis of aryl ketones catalyzed by phosphorus-free palladium catalysts
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Allylic alcohols, 1-buten-3-ol, 1-penten-3-ol and 1-octen-3-ol, reacted with aryl iodides (iodotoluene, 4-iodotoluene, 4-iodophenol and 4-iodanisole) under Heck reaction conditions to form corresponding saturated aryl ketones in one step. The same products were obtained in a two-step tandem reaction consisted of the Heck coupling of allylic alcohols with aryl iodides, followed by hydrogenation. Reactions were catalyzed by phosphorus-free palladium precursors modified with the menthol-substituted imidazolium chlorides. Formation of crystalline palladium nanoparticles, of the diameter up to 65 nm, in the reaction mixture was evidenced by TEM.
- Wirwis,Feder-Kubis,Trzeciak
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- Biomimetic Oxidative Deamination Catalysis via ortho-Naphthoquinone-Catalyzed Aerobic Oxidation Strategy
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An ortho-naphthoquinone-catalyzed oxidative deamination reaction has been developed where the molecular oxygen and water serve as the sole oxidant and nucleophile. The current aerobic deamination reaction proceeds via the ketimine formation between ortho-naphthoquinones and amines followed by the prototropic rearrangement and hydrolysis by water, representing a biomimetic oxidative deamination of amine species in the human body by the liver and kidneys. The compatibility of ortho-naphthoquinone organocatalysts with molecular oxygen and water opens up a new biomimetic catalyst system that can function as versatile deaminases for a variety of amine-containing molecules such as amino acids and DNA nuclear bases.
- Golime, Gangadhararao,Bogonda, Ganganna,Kim, Hun Young,Oh, Kyungsoo
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p. 4986 - 4990
(2018/05/14)
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