- Multimolecular self-organization of acetylene and arylamines into 1-aryl-3-ethyl-4-vinylpyrroles in the KOBut/DMSO system
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A new superbase-driven self-organization of four molecules of acetylene with one molecule of arylamine to 1-aryl-3ethyl-4-vinylpyrroles in the KOBut/DMSO system has been discovered. The process includes four acts of nucleophilic addition to acetylene followed by intramolecular cyclization of intermediate N,N-bis(1,3-dienyl)-N-arylamine.
- Ivanova, Elena V.,Schmidt, Elena Yu.,Semenova, Nadezhda V.,Trofimov, Boris A.,Ushakov, Igor A.
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Read Online
- Ultrasound-Promoted One-Pot Synthesis of Mono- or Bis-Substituted Organylselanyl Pyrroles
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A simple method for the direct mono- and bis-organylselenylation of N-substituted pyrroles through a multicomponent reaction promoted by ultrasonic radiation was described. These sonochemical promoted reactions were performed between different primary amines, 2,5-hexanedione and dialkyl, diheteroaryl, or diaryl diselenides, using catalytic amounts of copper iodide. Depending on the amount of copper iodide and diorganyl diselenide used in the reactions, mono- or bis-organylselenylation products were efficiently synthesized in high yields.
- Peglow, Thiago J.,Da Costa, Gabriel P.,Duarte, Luis Fernando B.,Silva, Márcio S.,Barcellos, Thiago,Perin, Gelson,Alves, Diego
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Read Online
- A convenient approach for the synthesis of substituted pyrroles by using phosphoric acid as a catalyst and their photophysical properties
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Twenty-three new pyrrole compounds aside from six knowns, including the synthetically challenging tetra- and penta-substituted pyrroles from the corresponding 1,4-dicarbonyl through Paal-Knorr synthesis in the presence of 5% phosphoric acid as the catalyst. Our method is noteworthy for cheap catalyst, uncomplicated experimental setup under air atmosphere, scalability, and excellent yields. The fluorescence of some selected pyrroles was investigated in dilute solution, and we found that all novel pyrroles emit strong blue fluorescences with considerable Stokes shifts.
- Ai, Liankun,Ibrahim, Yusuf Ajibola,Li, Baolin,Li, Jiahui
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- Magnetic solid sulfonic acid-enabled direct catalytic production of biomass-derived N-substituted pyrroles
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Five-membered nitrogen heterocyclic pyrroles have extremely high physiological activity and are widely used in medicine, agriculture, materials chemistry, industry, and supramolecular chemistry. Developing a mild and eco-friendly way to synthesize functionalized pyrroles from biologically derived materials is desirable. In this study, biomass-derived 2,5-dimethylfuran can react with a series of aromatic amines to synthesize 2,5-dimethyl-N-arylpyrroles through acid-enabled ring-opening and Paal-Knorr condensation in one pot. Among the tested acid catalytic materials, a new magnetic biocarbon-based sulfonic acid solid catalyst (WK-SO3H) showed excellent catalytic performance in the synthesis of N-substituted pyrroles (up to ca. 90% yield) and was easy to separate and recover by an external magnetic field. The ring-opening of furan proved to be the rate-determining step of the above one-pot multi-step conversion process, and 2,5-hexanedione is a key intermediate for the cascade reaction, while the addition of water could significantly enhance the above-mentioned ring-opening reaction. Furthermore, multiple characterization methods (e.g., FT-IR, TGA, XRD, NH3-TPD, and XPS) confirmed that WK-SO3H has good stability in the aqueous reaction system.
- Li, Hu,Liu, Yixuan,Wang, Keping,Wu, Mei,Yang, Ying
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p. 5312 - 5320
(2022/04/07)
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- Crystalline salicylic acid as an efficient catalyst for ultrafast Paal–Knorr pyrrole synthesis under microwave induction
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Abstract: In this study, the viability of a wide range of crystalline aromatic and aliphatic carboxylic acids as organocatalysts has been investigated for solvent-free Paal–Knorr pyrrole synthesis under microwave activation. Among these potential catalysts, crystalline salicylic acid proved to be a remarkable catalyst because its efficiency remained high even under low microwave power irradiation or a shorter reaction time for the model reaction. The outstanding catalytic activity of salicylic acid allowed the Paal–Knorr cyclocondensation with a turnover frequency up to 1472?h?1 which is unique in the context of a metal-free homogeneous catalysis. The attractive feature of this organocatalyst is its assistance in ultrafast pyrrole synthesis with no risk of metal contamination. Graphic abstract: [Figure not available: see fulltext.] Synopsis: A green and expeditious protocol for the synthesis of 2,5-dimethylpyrroles via combination of salicylic acid as catalyst (in its solid state) and microwaves has been introduced.
- Aghapoor, Kioumars,Mohsenzadeh, Farshid,Darabi, Hossein Reza,Sayahi, Hani
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- Facile fabrication of porous magnetic covalent organic frameworks as robust platform for multicomponent reaction
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The design of cheap yet efficient nanoporous magnetic catalysts for the environmentally benign process's widespread application is an extremely attractive, challenging chemical research field. A novel porous magnetic covalent organic framework was prepared by the condensation reaction of melamine and terephthaladehyde on the surface of 3,4-dihydroxybenzaldehyde coated magnetic Fe3O4 nanoparticles COF@Fe3O4 under hydrothermal conditions for the first time. The high surface area magnetic COF could exhibit superior catalytic activity for sustainable synthesis of trisubstituted and tetrasubstituted imidazoles and pyrroles in good to excellent yields in PEG as solvent under environmentally friendly, ambient conditions and making the overall process economical, efficient, and green. The retrievable catalyst in PEG is general and applicable to a broad substrate scope and functional group compatibility. The structure and morphology of the COF@Fe3O4 were characterized by FTIR, XRD, EDX, and SEM spectroscopy. The COF@Fe3O4 magnetic catalyst was recovered by an external magnet and used for several cycles without significant catalytic activity loss.
- Azizi, Najmedin,Heidarzadeh, Fatemeh,Farzaneh, Fezeh
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- Amidosulfonic acid supported on graphitic carbon nitride: novel and straightforward catalyst for Paal–Knorr pyrrole reaction under mild conditions
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A novel heterogeneous acidic catalyst was prepared by in situ immobilization of amidosulfonic acid (NH2SO3H) on graphitic carbon nitride (g-C3N4) under hydrothermal conditions. The textural morphology of NH2SO3H/g-C3N4 nanocomposite was characterized via powder X-ray diffraction, FT-IR, TGA, EDX, and scanning electron microscopy. The spatial arrangement of the amidosulfonic acid on the surface of g-C3N4 leads to the construction of a unique solid acid structure, resulting in a substantial enhancement of catalytic activity toward a high efficient preparation of pyrroles by Paal–Knorr reaction. The reactions undergo completion readily with good to excellent yields, with simple purification in an environmentally friendly manner. The NH2SO3H/g-C3N4 nanocomposite can be readily recycled, and no noteworthy reduction in the catalytic activity detected after four runs. Graphic abstract: [Figure not available: see fulltext.]
- Azhdari, Asieh,Azizi, Najmedin,Sanaeishoar, Haleh,Tahanpesar, Elham
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p. 625 - 634
(2021/05/12)
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- An expeditious and highly efficient synthesis of substituted pyrroles using a low melting deep eutectic mixture
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An expeditious green method for the synthesis of diverse valued substituted pyrroles through a Paal-Knorr condensation reaction, using a variety of amines and 2,5-hexanedione/2,5-dimethoxytetrahydrofuran in the presence of a low melting mixture ofN,N’-dimethylurea andL-(+)-tartaric acid (which acts as a dual catalyst/solvent system), has fruitfully been revealed. Herein, we have disclosed the applicability of this simple yet effective strategy for the generation of mono- and dipyrroles in good to excellent yields. Moreover,C3-symmetric tripyrrolo-truxene derivatives have also been assembled by means of cyclotrimerization, Paal-Knorr and Clauson-Kaas reactions as crucial steps. Interestingly, the melting mixture was recovered and reused with only a gradual decrease in the catalytic activity (over four cycles) without any significant drop in the yield of the product. This particular methodology is simple, rapid, environmental friendly, and high yielding for the generation of a variety of pyrroles. To the best of our knowledge, the present work reveals the fastest greener method reported up to this date for the construction of substituted pyrroles by utilizing the Paal-Knorr synthetic protocol, achieving impressive yields under operationally simple reaction conditions without involving any precarious/dangerous catalysts or unsafe volatile organic solvents.
- Alvi, Shakeel,Ali, Rashid
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p. 9732 - 9745
(2021/12/01)
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- Hexafluoroisopropanol as solvent and promotor in the Paal-Knorr synthesis of N-substituted diaryl pyrroles
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An additive-free synthesis of challenging N-substituted aryl pyrroles from the often poorly soluble corresponding 1,4-diketones by means of the Paal-Knorr pyrrole synthesis is reported, which makes use of the unique properties of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as a solvent and reaction promotor. Our procedure offers simple execution and purification as well as easy scale-up and can be applied in the Paal-Knorr synthesis of a large number of structurally diverse pyrroles including the synthetically challenging tetra- and penta-substituted pyrroles in moderate to excellent yields. HFIP can also be used as solvent in the Paal-Knorr synthesis of furans and thiophenes; however, the solvent effect is more pronounced in synthesis of pyrroles.
- Schirmacher, Robert H.E.,R?sch, Daniel,Thomas, Franziska
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- Synthesis of Fe3O4@L-proline@SO3H as a novel and reusable acidic magnetic nanocatalyst and its application for the synthesis of N-substituted pyrroles at room temperature under ultrasonic irradiation and without solvent
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N-Substituted pyrroles have been prepared in high isolated yields (65–90%) by the reaction of hexane-2,5-dione with amines or diamines in the presence of Fe3O4@L-proline@SO3H at ambient temperature under ultrasonic irradiation and without solvent. The experimental procedure involves simple operations, and the products are readily separated by external magnet. The same reaction of hexane-2,5-dione with amines containing electron-acceptor substituents, such as 4-nitroaniline, resulted in fair yields of pyrrole derivatives.
- Behbahani, Farahnaz K.,Shokri, Fatemeh
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- A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for Efficiently Synthesizing the High Value-Added 3-Methylindole by Aniline and Biomass-Derived Glycerin
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Abstract: An excellent catalyst with a large number of weak acid centers and highly dispersed copper nanoparticles embedded in mesoporous SBA-15 carrier was successfully constructed for the purpose of efficient conversion of aniline with biomass-derived glycerin to the high value-added 3-methylindole, in which the catalyst of Cu/SBA-15 was modified with Al2O3, La2O3 and CoO in sequence. The modified carrier and the copper-based catalysts were studied by scanning electron microscopy and energy-dispersive X-ray (SEM–EDX) spectroscopy, nitrogen physical adsorption, ammonia temperature programmed desorption (NH3-TPD), hydrogen temperature programmed reduction (H2-TPR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG–DTA) and inductively coupled plasma (ICP) emission spectroscopy. The research found that the Cu/CoO/La2O3/Al2O3/SBA-15 catalyst exhibited a very good catalytic performance with 3-methylindole yield up to 73.3% and selectivity reaching 86.4%. Besides, only a 3.9% yield decreased after the catalyst was circulated seven times. The characterizations revealed that Al2O3 could enhance the polarity of the carrier, thereby the interaction between the active component and the composite carrier was strengthened and the dispersion of copper was increased significantly. Adding La2O3 to Cu/SBA-15-Al2O3 could weaken the acidity and inhibit the formation of carbon deposits. CoO promoter could increase the number of weak acid centers, which was conducive to a good dispersion of active component and the high selectivity of 3-methylindole. Furthermore, the reaction pathway of gas-phase synthesis of 3-methylindole from glycerin and aniline on Cu/CoO/La2O3/Al2O3/SBA-15 was explored. Graphic Abstract: [Figure not available: see fulltext.]
- Sun, Pinghui,Lin, Shuyi,Guo, Huimei,Su, Jianhui,Shi, Lei
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p. 463 - 477
(2020/07/16)
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- Preparation method of biomass-based 2, 5-dimethyl-N-substituted pyrrole derivative
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The invention discloses a preparation method of a biomass-based 2, 5-dimethyl-N-substituted pyrrole derivative. The method comprises the following steps: adding 2, 5-dimethylfuran, an amine compound, a catalyst, distilled water and 2mL of solvent into a reaction kettle, and heating the reaction kettle in an oil bath pan; and obtaining the 2, 5-dimethyl-N-substituted pyrrole derivative after the temperature is 110-170 DEG C, the use amount of distilled water is 0-250 [mu] L, the use amount of the catalyst is 5-10 wt%, and the reaction time is 1-3 h. The method overcomes the defects of high cost and difficulty in separation and recovery of the existing catalyst or catalyst system.
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Paragraph 0023-0048
(2021/07/14)
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- One-pot synthesis of cyclohexylamine and: N -aryl pyrroles via hydrogenation of nitroarenes over the Pd0.5Ru0.5-PVP catalyst
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The direct synthesis of cyclohexylamine via the hydrogenation of nitrobenzene over monometallic (Pd, Ru or Rh) and bimetallic (PdxRu1-x) catalysts was studied. The Pd0.5Ru0.5-PVP catalyst was the most effective catalyst for this reaction. The catalyst can be reused and applied for the synthesis of N-aryl pyrroles and quinoxalines from nitrobenzenes.
- Chaudhari, Chandan,Sato, Katsutoshi,Ikeda, Yasuyuki,Terada, Kenji,Abe, Naoya,Nagaoka, Katsutoshi
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supporting information
p. 9743 - 9746
(2021/06/15)
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- Naturally occurring organic acids for organocatalytic synthesis of pyrroles via Paal–Knorr reaction
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Abstract: In this study, common naturally occurring organic acids, namely oxalic, malonic, succinic, tartaric and citric acid (as safe, inexpensive, and biodegradable organocatalysts), have been employed for Paal–Knorr pyrrole synthesis. The organocatalyzed reaction proved to be effective in ethanol at 60?°C. However, the reaction rate is mainly dominated by the nature and position of functional groups on the aromatic ring of substrate. This metal-free procedure tolerates a series of functional groups and should be considered as an asset to the pharmaceutical industry since no metal contamination could take place during the synthesis of pyrrole scaffolds. Graphic abstract: [Figure not available: see fulltext.].
- Mohsenzadeh, Farshid,Darabi, Hossein Reza,Alivand, Mahsa,Aghapoor, Kioumars,Balavar, Yadollah
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p. 5255 - 5262
(2020/09/09)
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- Fe3O4@SiO2-PTMS-Guanidine-SA nanoparticles as an effective and reusable catalyst for the synthesis of N-substituted pyrroles
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Fe3O4@SiO2-PTMS-Guanidine-SA nanoparticles used as an effective catalyst for the synthesis of N-substituted pyrroles. Pyrroles were synthesized from the reaction between primary amine derivatives and 2,5-hexanedione with high to excellent yields under mild reaction conditions. After completion of the reaction, Fe3O4@SiO2-PTMS-Guanidine-SA magnetic nanoparticles could be recovered easily from the reaction mixture by an external magnet and reused. This catalyst was characterized by FT-IR spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis and vibrating-sample magnetometry techniques.
- Rostami, Hedieh,Shiri, Lotfi
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p. 1329 - 1335
(2020/01/28)
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- Synthesis, structure and in vitro anti-trypanosomal activity of non-toxic arylpyrrole-based chalcone derivatives
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With an intention of identifying chalcone derivatives exhibiting anti-protozoal activity, a cohort of relatively unexplored arylpyrrole-based chalcone derivatives were synthesized in moderate to good yields. The resultant compounds were evaluated in vitro for their potential activity against a cultured Trypanosoma brucei brucei 427 strain. Several compounds displayed mostly modest in vitro anti-trypanosomal activity with compounds 10e and 10h emerging as active candidates with IC50 values of 4.09 and 5.11 μM, respectively. More importantly, a concomitant assessment of their activity against a human cervix adenocarcinoma (HeLa) cell line revealed that these compounds are non-toxic.
- Hoppe, Heinrich C.,Isaacs, Michelle,Khanye, Setshaba D.,Kruger, Cuan,Oderinlo, Ogunyemi O.,Smith, Vincent J.,Veale, Clinton G. L.,Zulu, Ayanda I.
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supporting information
(2020/04/10)
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- Method for preparing N-aryl pyrrole compound
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The present invention relates to a method for preparing an N-aryl pyrrole compound. Furan containing different substituents, aromatic amine containing different substituents and a solid Lewis acid catalyst are mixed and placed in a closed reactor, and an N-aryl pyrrole compound with different substituents is prepared under certain catalytic conditions. The reaction temperature of the catalytic reaction condition is 140-210 DEG C. The solid Lewis acid catalyst is prepared by a sol-gel method, Hf is used as a core metal element, and a mesoporous molecular sieve SBA-15 is used as a carrier. According to the method, the catalyst is simple to prepare, low in cost, high in reaction activity, good in water resistance and structural stability and high in catalytic reaction yield; meanwhile, the Lewis acid type catalyst does not generate acid protons, the corrosion of the catalyst to equipment at high temperature is avoided, the post-reaction treatment is convenient, and the catalyst is renewable and environment-friendly.
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Paragraph 0062-0064
(2020/09/09)
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- Superbase-promoted multi-molecular acetylene/arylamine self-organization to 1-arylpyrroles
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A new superbase-promoted reaction of acetylene involves self-organization of its three molecules with one molecule of arylamine in KOH/DMSO system to afford 1-aryl-2,5- dimethylpyrroles in up to 63% yields. The key step of this reaction cascade is assumed to be the nucleophilic addition of acetylene to the C = N bond of the intermediate aldimine (aza-Favorsky reaction).
- Schmidt, Elena Yu.,Semenova, Nadezhda V.,Ivanova, Elena V.,Bidusenko, Ivan A.,Trofimov, Boris A.
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p. 109 - 111
(2020/02/29)
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- Cascade Synthesis of Pyrroles from Nitroarenes with Benign Reductants Using a Heterogeneous Cobalt Catalyst
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A bifunctional 3d-metal catalyst for the cascade synthesis of diverse pyrroles from nitroarenes is presented. The optimal catalytic system Co/NGr-C@SiO2-L is obtained by pyrolysis of a cobalt-impregnated composite followed by subsequent selective leaching. In the presence of this material, (transfer) hydrogenation of easily available nitroarenes and subsequent Paal–Knorr/Clauson-Kass condensation provides >40 pyrroles in good to high yields using dihydrogen, formic acid, or a CO/H2O mixture (WGSR conditions) as reductant. In addition to the favorable step economy, this straightforward domino process does not require any solvents or external co-catalysts. The general synthetic utility of this methodology was demonstrated on a variety of functionalized substrates including the preparation of biologically active and pharmaceutically relevant compounds, for example, (+)-Isamoltane.
- Ryabchuk, Pavel,Leischner, Thomas,Kreyenschulte, Carsten,Spannenberg, Anke,Junge, Kathrin,Beller, Matthias
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supporting information
p. 18679 - 18685
(2020/09/02)
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- Synthesis of Pyrrole Derivatives Promoted by Fe(ClO4)3/SiO2 as an Environmentally Friendly Catalyst
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N-Substituted pyrroles have been prepared in high isolated yields (702-99%) by the reaction of hexane-2,5-dione with amines or diamines in the presence of Fe(ClO4)3/SiO2 at ambient temperature under solvent-free conditions. The experimental procedure involves simple operations, and the products are readily separated by short column chromatography. The same reaction of hexane-2,5-dione with amines containing electron-acceptor substituents, such as 4-nitroaniline, resulted in fair yields of pyrrole derivatives.
- Arabpourian,Behbahani
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p. 682 - 685
(2019/07/19)
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- A mild and efficient method for the synthesis of pyrroles using MIL-53(Al) as a catalyst under solvent-free sonication
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A highly efficient method for the synthesis of pyrroles using MIL-53(Al) as a catalyst has been developed under solvent-free sonication. This reaction has a broad substrate scope and high yields were obtained within a short reaction time. Remarkably, no additional additives and volatile organic solvent are required for this method and the MIL-53(Al) could be recovered and reused several times without significant drop-off in catalytic activity.
- Nguyen, Hai Truong,Thuy Nguyen, Linh Ho,Le Hoang Doan, Tan,Tran, Phuong Hoang
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p. 9093 - 9098
(2019/03/28)
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- ANDROGEN RECEPTOR ANTAGONISTS
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Compounds that inhibit the androgen receptor, pharmaceutical compositions comprising one or more of the compounds, as well as methods of treating cancer using such compounds are described.
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Paragraph 0330-0332
(2019/08/26)
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- Pyridine-Stabilized Rhodium Nanoparticles in Ionic Liquids as Selective Hydrogenation and Transfer Hydrogenation Catalysts
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Rhodium nanoparticles (RhNPs) stabilized with pyridine-based ligands in the ionic liquid [BMIM][BF4] (RhNPs-I to III) were synthesized from the organometallic precursor [Rh(μ-OMe)COD]2 under dihydrogen pressure. The pyridine-stabilized RhNPs showed smaller size compared to the ligand free RhNPs-V and presented higher activity and selectivity in the hydrogenation of acetophenone to 1-phenylethanol. In the case of pyridine-capped RhNPs-I, the system was reused for several runs without loss of activity and selectivity. Nitrobenzene was reduced to aniline with dihydrogen in the presence of RhNPs-I with moderate activity. When the hydrogen source was formic acid-Et3N azeotrope (transfer hydrogenation) the reaction was completed within minutes with high selectivity. Under transfer hydrogenation conditions, it was possible to apply the catalytic system RhNPs-I in multistep processes for the generation of substituted arylic amines through the reductive N-alkylation of nitrobenzene and benzaldehyde; and the synthesis of substituted pyrroles through the nitroarene reduction/Paal-Knorr condensation.
- Serrano-Maldonado, Alejandro,Martin, Erika,Guerrero-Ríos, Itzel
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- Grinding solvent-free paal-knorr pyrrole synthesis on smectites as recyclable and green catalysts
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An environmentally benign method for the synthesis of N-substituted pyrroles from one-pot solvent-free condensation reaction of 2,5-hexanedione with various primary amines (Paal-Knorr pyrrole synthesis) on smectite clays as green and reusable heterogeneous Lewis acid catalysts is presented. The use of nontoxic, inexpensive, easily available and reusable catalysts under solvent-free conditions make this protocol practical, environmentally friendly and economically attractive.
- Marvi, Omid,Nahzomi, Hossein Taherpour
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p. 139 - 147
(2018/04/23)
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- Bio-based material as medium, mild and reusable catalyst for paal–knorr pyrrole synthesis with and without ultrasonic irradiation
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Background: Pyrrole moiety is found in naturally occurring compounds such as chlorophyll, haem, and vitamin B12 and present in a number of drugs for example atorvastatin, ketorolac, elopiprazole, tolmetin and sunitinib. Various methods have been used for the synthesis of pyrrole derivatives; however, still there is a need for environmentally benign and economic protocol. Method: We have reported a simple, mild and speedy synthesis of N-substituted 2,5-dimethyl pyrrole derivatives in ‘’GAAS’’ as medium and catalyst at room temperature and under ultrasound irradiation. Results: This protocol was employed for the synthesis of various 2,5-dimethyl-N-substituted pyrrole-derivatives using both aliphatic as well as aromatic amines in short time (2 to 10 minutes)with excellent yield (84-95%) at room temperature and under ultrasonic irradiation. The catalytic system “GAAS’’ was regenerated and reused five times effectively without major loss of activity. Conclusion: In conclusion, we have developed an eco-friendly, simple, faster, reusable, mild, and efficient protocol for the synthesis of N-substituted pyrrole derivatives. This bio-based protocol is cost-effective and greener methodology for the synthesis of biologically active N-substituted pyrrole derivatives.
- Sharma, Abha,Kalyani, Illa Siva,Fatima, Anam
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supporting information
p. 226 - 232
(2018/03/09)
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- Novel and highly efficient preparation of pyrroles using supported ionic liquid ILCF3SO3@SiO2 as a heterogeneous catalyst
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Abstract: A supported ionic liquid ILCF3SO3@SiO2 was synthesized and used as a highly efficient catalyst in the Paal–Knorr reaction for the preparation of pyrroles. The heterogeneous catalyst could be easily recovered and recycled for five times without noticeable loss of catalytic activity. Also a possible reaction mechanism is provided.
- Liu, Yang,Hu, Yu Lin
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p. 1033 - 1040
(2018/05/22)
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- Microwave-induced calcium(II) chloride-catalyzed Paal–Knorr pyrrole synthesis: a safe, expeditious, and sustainable protocol
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Abstract: Among various alkali (Na, K) and alkaline-earth (Ca, Mg, Sr, Ba) chlorides, calcium(II) chloride was found to be a cost-effective Lewis acid catalyst for solvent-free synthesis of pyrroles from primary aromatic and aliphatic amines under open-vessel focused microwave irradiation. The salient features of this environmentally benign method are high to quantitative conversion, short reaction time, safe and clean reaction profile, possibility of scale-up to multigram quantities, and use of a low-cost, widely available, nontoxic catalyst.
- Aghapoor, Kioumars,Mohsenzadeh, Farshid,Darabi, Hossein Reza,Rastgar, Saeed
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p. 4063 - 4072
(2018/06/19)
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- A New Green and Efficient Br?nsted: Lewis Acidic DES for Pyrrole Synthesis
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Abstract: Deep eutectic solvents (DESs) are fluids composed of different Lewis or Br?nsted acids and bases, generally acknowledged as new analogues to ionic liquids (ILs), because of their similar characteristics, but with more advantages related to preparation cost, environmental impact etc. Their preparation involve the simple mixing of two components generally with moderate heating that are inexpensive, non-toxic, biodegradable and the resulting mixture is capable to overcome the drawbacks of conventional organic solvents and ILs. Chemical reactions with these materials are significantly less hazardous and they can act as catalysts as well as reaction media. Here, three new DESs based on ZrOCl2·8H2O in combination with urea, ethylene glycol and glycerol are introduced. Physicochemical properties like phase behaviour, Freezing point, density, viscosity, thermal stability and miscibility properties in common solvents are determined. In addition, a new method for the determination of acidity of DESs having both Br?nsted and Lewis sites is also introduced in this work. A convenient synthesis of pyrrole through Paal–Knorr reaction is reported using a variety of amines which are used to establish the importance of this catalyst in organic reactions. The products are analysed by GC–MS, 1H NMR and 13C NMR. By comparing the three DESs, DES 1 (formed from ZrOCl2·8H2O with urea) has the lowest density, viscosity, highest acidity and thermal stability. It was shown to be an excellent green catalyst for Paal–Knorr reaction. Reusability of the catalyst was also achieved up to 4 runs, without significant loss in its catalytic activity. Graphical Abstract: [Figure not available: see fulltext.]
- Shaibuna,Theresa, Letcy V.,Sreekumar
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p. 2359 - 2372
(2018/06/20)
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- New nano-Fe3O4-supported Lewis acidic ionic liquid as a highly effective and recyclable catalyst for the preparation of benzoxanthenes and pyrroles under solvent-free sonication
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A novel magnetic nanomaterial-immobilized Lewis acidic ionic liquid was successfully synthesized by the covalent embedding of 3-(3-(trimethoxysilyl)propyl)-1H-imidazol-3-ium chlorozincate (ii) ionic liquid to the surface of Fe3O4 nanoparticles. The material was then characterized by FT-IR, SEM, TEM, TGA, ICP-OES, Raman, and EDS. Its performance as a new-generation Lewis acidic catalyst was also examined on the ultrasound-mediated synthesis of benzoxanthenes and pyrroles. Upon completion, the catalyst was simply recovered by an external magnet for multiple reuses without significant lessening of catalytic performance.
- Nguyen, Hai Truong,Thi Le, Ngoc-Phuong,Nguyen Chau, Duy-Khiem,Tran, Phuong Hoang
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p. 35681 - 35688
(2018/10/31)
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- A green and efficient method for the synthesis of pyrroles using a deep eutectic solvent ([CholineCl][ZnCl2]3) under solvent-free sonication
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An efficient deep eutectic solvent-based synthesis of pyrroles under ultrasound irradiation has been developed to provide a significant improvement of the yield up to 99% in a short reaction time. The synthesis of pyrroles is highly atom-economical, producing water as the sole byproduct. In addition, [CholineCl][ZnCl2]3 is easily synthesized from commercially available choline chloride and zinc chloride via a cost-effective and environmentally benign pathway. The obtained [CholineCl][ZnCl2]3 has been characterized by FT-IR, 1H-NMR, 13C-NMR, HRMS (ESI), Raman, and TGA. Five new pyrroles are synthesized by the current method. Moreover, [CholineCl][ZnCl2]3 could be reused up to four times without significant loss of catalytic activity.
- Truong Nguyen, Hai,Nguyen Chau, Duy-Khiem,Tran, Phuong Hoang
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p. 12481 - 12489
(2017/11/06)
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- Direct Synthesis of Pyrroles via Heterogeneous Catalytic Condensation of Anilines with Bioderived Furans
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Given the wide applications of pyrroles in agriculture, pharmaceuticals, and supramolecular and materials chemistry, a mild and eco-friendly route to produce functionalized pyrroles from bioderived feedstocks is highly desirable. Described herein is a mild and convenient synthesis of pyrroles via direct condensation of an equimolar amount of structurally diverse anilines with biobased furans catalyzed by a simple and efficient solid acid H form zeolite Y catalyst. The protocol tolerates a large variety of functional groups and offers a general and versatile method for scale-up synthesis of a variety of N-substituted pyrrole compounds. Most importantly, the bioactive pyrrole-derived drug pyrvinium, which has lately been confirmed as highly effective in curing colon cancer, can be obtained by this method.
- Tao, Lei,Wang, Zi-Jian,Yan, Tian-Hao,Liu, Yong-Mei,He, He-Yong,Cao, Yong
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p. 959 - 964
(2017/08/09)
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- One-pot synthesis of: N -substituted pyrroles from nitro compounds and 2,5-hexadione over a heterogeneous cobalt catalyst
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In this study, the one-pot heterocyclization of nitro compounds with 2,5-hexadione was studied for the synthesis of N-substituted pyrroles via a Paal-Knorr condensation process. The heterogeneous cobalt-nitrogen catalyst (Co-Nx/C-800-AT) was found to be active for this reaction with formic acid. Formic acid served as a hydrogen donor for the transfer hydrogenation, and also acted as an acid catalyst. More importantly, this method was tolerant of other functional groups, and hence various N-substituted pyrroles were produced with good to excellent yields. The Co-Nx/C-800-AT catalyst was highly stable, and could be reused several times without loss of its catalytic activity.
- Gong, Zheng,Lei, Yu,Zhou, Peng,Zhang, Zehui
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p. 10613 - 10618
(2017/10/05)
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- Silica tungstic acid and sulphated silica tungstic acid as highly efficient solid acid catalysts for the synthesis of pyrrole derivatives
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In the present study silica supported tungstic acid (STA) and sulphated silica tungstic acid (SSTA) were applied as efficient and cost-effective solid acid catalysts in the synthesis of N-substituted pyrrole derivatives via the Paal–Knorr reaction of 2,5-hexadione with aromatic and aliphatic amines at room temperature. The reaction completed in short time under mild conditions with high yield. The catalysts could be easily recovered upon reaction completion. Structures of all products were confirmed by elemental analysis, FT-IR, 1H and 13C NMR spectra.
- Moradgholi,Lari,Baratian
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p. 2924 - 2927
(2017/03/22)
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- L-Tryptophan-catalyzed Paal-Knorr pyrrole cyclocondensation: An efficient, clean and recyclable organocatalyst
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A simple, clean, and efficient solvent-free protocol is introduced for Paal-Knorr pyrrole synthesis catalyzed by l-tryptophan as a thermally resistant, natural primary amino acid. The products were obtained mostly in excellent yields through the reaction of hexane-2,5-dione with aromatic primary amines bearing a variety of substituents. The catalyst could be easily isolated from the reaction mixture and recycled at least six times without significant loss of activity. The procedure has an environmentally benign nature in agreement with the concepts of green chemistry.
- Aghapoor, Kioumars,Mohsenzadeh, Farshid,Darabi, Hossein Reza,Sayahi, Hani,Balavar, Yadollah
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p. 407 - 415
(2016/04/26)
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- Greener Paal-Knorr Pyrrole Synthesis by Mechanical Activation
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A straightforward and solventless synthesis of pyrroles was developed by using mechanochemical activation and a biosourced organic acid as the catalyst. Relative to traditional Paal-Knorr methodologies, various N-substituted pyrroles were obtained in very short reaction times. By reaction with unreactive diketones, desymmetrized aliphatic and aromatic compounds were also synthesized.
- Akelis, Liudvikas,Rousseau, Jolanta,Juskenas, Robertas,Dodonova, Jelena,Rousseau, Cyril,Menuel, Stphane,Prevost, Dominique,Tumkeviius, Sigitas,Monflier, Eric,Hapiot, Frdric
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- Ruthenium Metal–Organic Frameworks with Different Defect Types: Influence on Porosity, Sorption, and Catalytic Properties
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By employing the mixed-component, solid-solution approach, various functionalized ditopic isophthalate (ip) defect-generating linkers denoted 5-X-ipH2, where X=OH (1), H (2), NH2(3), Br (4), were introduced into the mixed-valent ruthenium analogue of [Cu3(btc)2]n(HKUST-1, btc=benzene-1,3,5-tricarboxylate) to yield Ru-DEMOFs (defect-engineered metal–organic frameworks) of the general empirical formula [Ru3(btc)2?x(5-X-ip)xYy]n. Framework incorporation of 5-X-ip was confirmed by powder XRD, FTIR spectroscopy, ultrahigh-vacuum IR spectroscopy, thermogravimetric analysis,1H NMR spectroscopy, N2sorption, and X-ray absorption near edge structure. Interestingly, Ru-DEMOF 1 c with 32 % framework incorporation of 5-OH-ip shows the highest BET surface area (≈1300 m2g?1, N2adsorption, 77 K) among all materials (including the parent framework [Ru3(btc)2Yy]n). The characterization data are consistent with two kinds of structural defects induced by framework incorporation of 5-X-ip: modified paddlewheel nodes featuring reduced ruthenium sites (Ruδ+, 02, CO, H2) and the catalytic properties of the materials (i.e., ethylene dimerization and the Paal–Knorr reaction).
- Zhang, Wenhua,Kauer, Max,Halbherr, Olesia,Epp, Konstantin,Guo, Penghu,Gonzalez, Miguel I.,Xiao, Dianne J.,Wiktor, Christian,LIabrés i Xamena, Francesc X.,W?ll, Christof,Wang, Yuemin,Muhler, Martin,Fischer, Roland A.
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p. 14297 - 14307
(2016/09/23)
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- Efficient synthesis of substituted pyrroles through Pd(OCOCF3)2-catalyzed reaction of 5-hexen-2-one with primary amines
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An efficient and facile Pd(OCOCF3)2-catalyzed one-pot cascade protocol has been developed for the synthesis of multiple substituted pyrroles in good to excellent yields. Unlike the reported method starting from the 2-alkenal-1,3-carbonyl compounds, the process utilizes the less reactive 5-hexen-2-one and the method has great potential as a complement to the current developed methods.
- Chen, Xi,Yang, Meng,Zhou, Min
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supporting information
p. 5215 - 5218
(2016/11/11)
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- Indium-Catalyzed Formal N-Arylation and N-Alkylation of Pyrroles with Amines
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Under indium Lewis acid catalysis, a nitrogen atom of N-unsubstituted pyrroles was replaced with a nitrogen atom of primary amines, thereby producing N-aryl- and N-alkylpyrroles. This system formally introducing such carbon frameworks to the pyrrole nitrogen atom shows unique selectivity: only the H?N(pyrrolyl) unit undergoes the N-arylation and N-alkylation even in the coexistence of a similar H?N(indolyl) part; and an aryl–halogen bond remains intact. These are clearly different from the typical method depending on the C?N(pyrrolyl) bond-forming reaction with organic halides as substrates. From a viewpoint of pyrrole N-protection–deprotection chemistry, worth noting is that a methyl group on the pyrrole nitrogen atom can be removed, albeit in a formal way. (Figure presented.).
- Yonekura, Kyohei,Oki, Kenji,Tsuchimoto, Teruhisa
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p. 2895 - 2902
(2016/09/16)
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- The application of iron (III) phosphate in the synthesis of N-substituted pyrroles
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A variety of N-substituted pyrroles have been prepared by reacting 2,5-hexadione with amines or diamines in the presence of iron (III) phosphate at room temperature under solvent-free conditions. The experiment protocol features simple operations, and the products are isolated in high yields (88-99%).
- Samadi, Marjan,Behbahani, Farahnaz K.
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p. 2881 - 2884
(2015/11/03)
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- Catalytic activity of the nanoporous MCM-41 surface for the Paal-Knorr pyrrole cyclocondensation
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The investigation of different oxide surfaces revealed that nanoporous silica (MCM-41) had the best catalytic activity for Paal-Knorr pyrrole synthesis. Despite the same composition, MCM-41 proved to be more effective than SiO2 itself, probably due to a significantly higher surface area of the SiO2 nanopores. The important features of this "clean" solvent-free protocol are the ease of recovery and the reuse of the catalyst for several cycles, operational simplicity, and easy product isolation and purification.
- Aghapoor, Kioumars,Amini, Mostafa M.,Jadidi, Khosrow,Mohsenzadeh, Farshid,Darabi, Hossein Reza
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p. 475 - 481
(2015/08/06)
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- Discovery and optimisation studies of antimalarial phenotypic hits
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There is an urgent need for the development of new antimalarial compounds. As a result of a phenotypic screen, several compounds with potent activity against the parasite Plasmodium falciparum were identified. Characterization of these compounds is discussed, along with approaches to optimise the physicochemical properties. The in vitro antimalarial activity of these compounds against P. falciparum K1 had EC50 values in the range of 0.09e29 mM, and generally good selectivity (typically >100-fold) compared to a mammalian cell line (L6). One example showed no significant activity against a rodent model of malaria, and more work is needed to optimise these compounds.
- Mital, Alka,Murugesan, Dinakaran,Kaiser, Marcel,Yeates, Clive,Gilbert, Ian H.
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supporting information
p. 530 - 538
(2015/10/12)
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- The Paal-Knorr reaction revisited. A catalyst and solvent-free synthesis of underivatized and N-substituted pyrroles
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A new, modified synthesis of pyrroles is described. The reaction of 2,5-hexandione with a variety of amines yielded the expected pyrrole analogues in excellent yields. The reactions were carried out under the ultimate green conditions excluding both catalyst and solvent applying simple stirring at room temperature. The variety of amines include aqueous ammonium hydroxide for the synthesis of pyrroles with a free NH group, and benzylamines, anilines and phenylene-diamines for the synthesis of several N-derivatized pyrroles. The reaction also occurs efficiently with a variety of 1,4-diketones, although the reaction rates and yields are lower for the diketones that do not possess terminal methyl group(s). This journal is
- Cho, Hyejin,Madden, Richard,Nisanci, Bilal,T?r?k, Bla
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p. 1088 - 1099
(2015/03/04)
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- Cyclodextrin-based PNN supramolecular assemblies: a new class of pincer-type ligands for aqueous organometallic catalysis
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Water-soluble cyclodextrins (CDs) bearing two nitrogen atoms as metal coordinating sites have been synthesized. An appropriate phosphane could be included within their cavity through the primary face to form self-assembled PNN supramolecular edifices. Once the PNN ligands were coordinated to platinum, the resulting complexes proved to be very effective as catalysts in a domino reaction, where a Pt-catalyzed reduction of nitrobenzene was followed by a Paal-Knorr pyrrole reaction. In the nitrobenzene reduction, the modified CDs acted both as first- and second-sphere ligands. Contrary to an acyclic glucopyranose-based NN ligand unable to interact with a phosphane ligand, the CD-based PNN ligands stabilized the catalytic species in water by supramolecular means. Interestingly, the product and the water-soluble Pt-catalyst could be recovered in two different phases once the reaction was complete.
- Menuel,Bertaut,Monflier,Hapiot
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p. 13504 - 13512
(2015/08/03)
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- Energy efficiency of heterogeneous catalytic microwave-assisted organic reactions
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The energy efficiency of microwave-assisted reactions was studied under heterogeneous catalytic conditions. Based on earlier publications the choice of catalyst was a semi-synthetic montmorillonite K-10. This material absorbs microwave energy effectively and is an excellent catalyst for microwave-assisted organic synthesis. The energy consumption of six different types of K-10 catalyzed reactions with multiple substrates and varied experimental parameters were determined under microwave irradiation and conventional heating. The parallel reactions were carried out under the same conditions to ensure the comparability of the data. While in the majority of the studied reactions, the microwave-assisted method appeared to be more energy efficient by various extents, in one case the conventional heating was found to be more efficient. The data, in agreement with a previous report, indicate that reactions should be studied on a case-by-case basis and that an automatic green label for microwave-assisted reactions is not warranted. This journal is the Partner Organisations 2014.
- Cho, Hyejin,Toeroek, Fanni,Toeroek, Bela
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p. 3623 - 3634
(2014/07/08)
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- Paal-knorr pyrrole synthesis in water
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Water was a suitable medium for Paal-Knorr pyrrole cyclocondensation. Hexa-2,5-dione was reacted with several aliphatic and aromatic primary amines, affording N-substituted 2,5-dimethyl pyrrole derivatives in good to excellent yields. An efficient, green method using water either as environmentally friendly solvent or catalyst was presented.
- Akbaslar, Dilek,Demirkol, Onur,Giray, Sultan
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supporting information
p. 1323 - 1332
(2014/04/17)
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- L-(+)-Tartaric acid and choline chloride based deep eutectic solvent: An efficient and reusable medium for synthesis of N-substituted pyrroles via Clauson-Kaas reaction
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l-(+)-Tartaric acid-choline chloride based deep eutectic solvent has been found to be an effective promoted medium for Clauson-Kaas reaction of aromatic amines and 2,5-dimethoxytetrahydrofuran. Structurally diverse N-substituted pyrroles were obtained in high to excellent yields under mild conditions. The deep eutectic solvent is inexpensive, non-toxic, reusable and biodegradable.
- Wang, Ping,Ma, Fei-Ping,Zhang, Zhan-Hui
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p. 259 - 262
(2014/11/07)
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- Sulfamic acid heterogenized on functionalized magnetic Fe3O4 nanoparticles with diaminoglyoxime as a green, efficient and reusable catalyst for one-pot synthesis of substituted pyrroles in aqueous phase
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Surface functionalization of magnetic nanoparticles is an elegant way to bridge the gap between heterogeneous and homogeneous catalysis. We have conveniently loaded sulfonic acid groups on amino-functionalized Fe3O4 nanoparticles affording sulfamic acid-functionalized magnetic Fe3O4 nanoparticles (MNPs/DAG-SO3H) as an active and stable magnetically separable acidic nanocatalyst, which was characterized using X-ray diffraction, Fourier transform infrared and energy-dispersive X-ray spectroscopies, scanning and transmission electron microscopies, vibrating sample magnetometry and elemental analysis. The catalytic activity of MNPs/DAG-SO3H was probed through one-pot synthesis of N-substituted pyrroles from γ-diketones and primary amines in aqueous phase at room temperature. The heterogeneous catalyst could be recovered easily by applying an external magnet device and reused many times without significant loss of its catalytic activity.
- Veisi, Hojat,Mohammadi, Pourya,Gholami, Javad
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p. 868 - 873
(2015/02/19)
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- Hexaalkylguanidinium salts as ionic liquids - Applications in titanium and aluminium alcoholate assisted synthesis
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The solubility of titanium and aluminium alcoholates and of titanium tetrakis(trimethylsilanolate) in several hexaalkylguanidinium-based room temperature ionic liquids was screened. The solvent/solute combinations which displayed the highest alcoholate solubility and stability were applied as Lewis-acidic catalytic media for several dehydrating cyclocondensations: lactamisation of ω-aminocarboxylic acids, direct amidation of carboxylic acids, synthesis of oxazolines from carboxylic acids and 2-aminoethanol, lactonisation of 6-hydroxyhexanoic acid, and Paal-Knorr synthesis of pyrroles.
- Arkhipova, Maria,Eichel, Svetlana,Maas, Gerhard
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p. 56506 - 56517
(2015/02/05)
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