- 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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- 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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- 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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- 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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- Synthesis, radiolabeling and evaluation of novel amine guanidine derivatives as potential positron emission tomography tracers for the ion channel of the N-methyl-d-aspartate receptor
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The N-Methyl-d-Aspartate receptor (NMDAR) is involved in many neurological and psychiatric disorders including Alzheimer's disease and schizophrenia. The aim of this study was to develop a positron emission tomography (PET) ligand to assess the bio-availa
- Klein, Pieter J.,Chomet, Marion,Metaxas, Athanasios,Christiaans, Johannes A.M.,Kooijman, Esther,Schuit, Robert C.,Lammertsma, Adriaan A.,Van Berckel, Bart N.M.,Windhorst, Albert D.
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p. 143 - 160
(2016/05/09)
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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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- Design and development of pyrrole carbaldehyde: An effective pharmacophore for enoyl-ACP reductase
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Enoyl-ACP reductase is the key enzyme involved in FAS-II synthesis of mycolic acid in bacterial cell wall and is a promising target for discovering new chemical entity. The designed pharmacophores are the possible better tools to combat mutation in enoyl-ACP enzyme, which leads to a decrease in volume of triclosan binding site. Compound 3a showed H-bonding interactions similar to that of triclosan with enoyl-ACP enzyme and with a better docking score (C score 8.81), while the compound 3f showed additional interaction with MET98.H amino acid residue. The 3D-QSAR computations also support the docking study to develop novel pyrrole-based derivatives. Graphical abstract: Molecular docking 3D-QSAR studies and synthesis of active analogs of pyrrole carbaldehyde as better receptor fit pharmacophore for enoyl-ACP reductase along with in vitro antitubercular activity. (Figure Presented).
- Joshi, Shrinivas D.,Kumar, Devendra,More, Uttam A.,Yang, Kap Seung,Aminabhavi, Tejraj M.
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p. 672 - 689
(2016/03/08)
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- Synthesis of two distinct pyrrole moiety-containing arenes from nitroanilines using Paal-Knorr followed by an indium-mediated reaction
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Synthesis of arenes substituted with two differently substituted-pyrrole moieties was investigated. A Paal-Knorr condensation reaction of nitroanilines with 1,4-diketone to nitrophenyl-1H-pyrroles followed by an indium-mediated reduction-triggered coupling reaction with another kind of 1,4-diketone resulted in two distinct pyrrole-containing arenes, variously substituted 1-((1H-pyrrol-1-yl)phenyl)-1H-pyrroles, in reasonable yield.
- Kim, Byeong Hyo,Bae, Seolhee,Go, Ahra,Lee, Hyunseung,Gong, Cheoloh,Lee, Byung Min
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p. 265 - 276
(2015/12/30)
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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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- Paal-Knorr pyrrole synthesis using recyclable amberlite IR 120 acidic resin: A green approach
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Amberlite IR 120 acidic resin, a polymer matrix, has been demonstrated as a catalyst for Paal-Knorr condensation of 2,5-hexadione with primary amines under solvent-free conditions. This is an efficient, mild, and green methodology for N-substituted pyrrole derivatives. Copyright Taylor & Francis Group, LLC.
- Devi, Aarti,Shallu,Sharma,Singh, Jasvinder
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experimental part
p. 1480 - 1488
(2012/05/05)
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- Silica-supported bismuth(III) chloride as a new recyclable heterogeneous catalyst for the Paal-Knorr pyrrole synthesis
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Silica-supported bismuth(III) chloride (BiCl3/SiO2) acts as as a highly efficient heterogeneous Lewis acid catalyst for the Paal-Knorr pyrrole synthesis in hexane at room temperature. The catalyst exhibited remarkable reusable activity and higher catalytic performance than homogeneous BiCl3. A plausible mechanism for the catalytic action of BiCl3/SiO2 has been introduced.
- Aghapoor, Kioumars,Ebadi-Nia, Leila,Mohsenzadeh, Farshid,Mohebi Morad, Mina,Balavar, Yadollah,Darabi, Hossein Reza
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experimental part
p. 25 - 30
(2012/05/20)
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