- TEMPO-mediated aerobic oxidative synthesis of 2-aryl benzoxazoles via ring-opening of benzoxazoles with benzylamines
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A simple and efficient TEMPO-mediated system for aerobic oxidative synthesis of 2-aryl benzoxazoles from readily available benzoxazoles and primary benzylic and hetero benzylic amines is presented in one pot. The reaction proceeds through the ring-opening of benzoxazoles and is followed by oxidative condensation with benzylamines. These metal-free, straightforward reactions worked well with a wide range of substrates, yielding moderate to good yields under mild conditions using air as an external green oxidant.
- Rao, Mugada Sugunakara,Hussain, Sahid
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p. 2684 - 2694
(2021/07/26)
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- Syntheses, characterization, and catalytic potential of novel vanadium and molybdenum Schiff base complexes for the preparation of benzimidazoles, benzoxazoles, and benzothiazoles under thermal and ultrasonic conditions
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A new ONO-tridentate Schiff base ligand (H2L) derived from 3-methoxysalicylaldehyde and nicotinic hydrazide was synthesized and characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR, UV–Vis, and powder XRD studies. Then, oxovanadium(V) and dioxomolybdenum(VI) Schiff base complexes, VOL and MoO2L, were also prepared and characterized by different techniques. Moreover, the catalytic activities of both complexes were investigated for the synthesis of benzimidazoles, benzoxazoles, and benzothiazoles under reflux conditions as well as through ultrasonic irradiation. The results revealed several advantages of this procedure, including high product yields, short reaction times, facile work-up procedure, simplicity in operation, eco-friendly reaction conditions, and green aspects by avoiding toxic catalysts and solvents. Graphic abstract: [Figure not available: see fulltext.]
- Kargar, Hadi,Kargar, Khadijeh,Fallah-Mehrjardi, Mehdi,Munawar, Khurram Shahzad
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p. 593 - 605
(2021/06/21)
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- Dowex 50W: A green mild reusable catalyst for the synthesis of 2-aryl benzoxazole derivatives in aqueous medium
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In this work simple efficient, one pot and environmentally friendly method was developed for the synthesis of 2-Aryl-1H-benzoxazole derivatives at 80oC using ortho-aminophenol and various aldehydes. It has been found that Dowex 50W is an effective catalyst to prepare moderate to high yield of a variety of benzoxazole derivatives through a clean and simple process. Aqueous medium, green methodology, rapid reaction, reusability of heterogeneous catalyst are the great advantages of this protocol.
- Datta, Arup
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p. 341 - 347
(2021/05/19)
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- Heterogeneous palladium (II)-complexed dendronized polymer: A rare palladium catalyst for the one-pot synthesis of 2-arylbenzoxazoles
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The palladium complex of dendronized amine polymer (EG–Gn–Pd, n = 0, 1 and 2) having ethylene glycol-initiated polyepichlorohydrin as core was synthesized on a Merrifield resin support and was well characterized. Generally, palladium catalysts are known for carbon–carbon coupling reactions. Here, a developed catalyst was found to be good for benzoxazole synthesis. Higher generation dendronized polymer (EG–G2–Pd) was found to be better catalyst over lower generation dendronized polymers. Moreover, dendronized polymers were found to be a better catalyst over dendrigraft polymers. The catalyst reusability was checked and good yield was obtained for five cycles.
- George, Smitha,Sreekumar, Krishnapillai
-
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- Sulfur/DABCO Promoted Reductive Coupling/Annulation Cascade Reaction between o -Hydroxy/Amino Nitrobenzenes and Benzaldehydes
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Sulfur/DABCO was found to be an efficient reagent in promoting- the reductive coupling/annulation of o -nitrophenols or o -nitroanilines with benzaldehydes. This method represents a simple, straightforward, and green approach to the construction of benz-oxazoles and benzimidazoles.
- Dang, Minh-Huy Dinh,Nguyen, Linh Ho Thuy,Tran, Phuong Hoang
-
supporting information
p. 1687 - 1694
(2020/05/25)
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- Phosphine-phosphonium ylides as ligands in palladium-catalysed C2-H arylation of benzoxazoles
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As balanced electron-rich P,C-chelating ligands, phosphine-phosphonium-ylides are considered for their ability to in situ promote palladium-catalysed direct C(sp2)–H arylation. Using methyl phosphonium salts of 2,2'-bis(diphenylphosphino)-1,1'-binaphtyl (“methyl-BINAPIUM”) as ylide precursors under optimized reaction conditions, arylation of benzoxazole was found to proceed in moderate to high yield to give functional 2-aryl benzoxazoles. A strong anion effect of the non-salt free ylide was evidenced (TfO? > I? > PF6? ≈ salt-free). This first example of phosphonium ylides as ligands in catalytic C–H activation extends the prospect of their general implementation in homogeneous transition metal catalysis.
- Yao, Zhenyu,Lin, Xing,Chauvin, Remi,Wang, Lianhui,Gras, Emmanuel,Cui, Xiuling
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p. 3250 - 3254
(2020/05/25)
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- Efficient Cu-catalyzed intramolecular: O -arylation for synthesis of benzoxazoles in water
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An efficient method was developed for synthesis of benzoxazoles by Cu-catalyzed intramolecular O-arylation of o-halobenzanilides in water. This strategy provides several advantages, such as high yields, water as a green solvent and functional groups tolerance.
- Gao, Hui,Li, Minxin,Mao, Zewei,Rao, Gaoxiong,Tang, Yanling
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p. 14317 - 14321
(2020/04/23)
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- Acid-promoted cleavage of the C–C double bond of N-(2-Hydroxylphenyl)enaminones for the synthesis of benzoxazoles
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An acid-mediated selective cleavage of C–C double bond of N-(2-hydroxylphenyl)enaminones with formation a new C–O bond for the synthesis of 2-substituted benzoxazoles has been developed. This protocol proceeds under transition metal- and oxidant-free conditions with broad functional group tolerance. The oxidative cleavage of C–C double bond of N-(2-hydroxylphenyl)enaminone is also realized using NCS or NFSI as oxidants with release of 2,2-dihalogen-acetophenone fragments.
- Ge, Bailu,Peng, Yanling,Liu, Jing,Wen, Si,Peng, Cheng,Cheng, Guolin
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- Nickel catalysed construction of benzazoles: Via hydrogen atom transfer reactions
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Herein we report a homogeneous, phosphine free, inexpensive nickel catalyst that forms a wide variety of benzazoles from alcohol and diamines by a reaction sequence of alcohol oxidation, imine formation, ring cyclization and dehydrogenative aromatization. A reversible azo/hydrazo couple, that is part of the ligand architecture steers both the alcohol oxidation and dehydrogenation of the annulated amine under fairly mild reaction conditions. Interestingly, both the alcohol oxidation and amine dehydrogenation steps are directly mediated by hydrogen atom transfer (HAT), which is greatly facilitated by the reduced ligand backbone. The kH/kD for the amine dehydrogenation step, measured at 60 °C is 5.9, fully consistent with HAT as the rate determining factor during this step. This is a unique scenario where two consecutive oxidation steps towards benzazole formation undergo HAT, which has been substantiated via kinetic studies, KIE determination and intermediate isolation. This journal is
- Adhikari, Debashis,Bains, Amreen K.,Dey, Dhananjay,Kundu, Abhishek,Yadav, Sudha
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p. 6495 - 6500
(2020/11/13)
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- Synthesis and X-ray crystal structures of three new nickel(II) complexes of benzoylhydrazones: Catalytic applications in the synthesis of 2-arylbenzoxazoles
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Three new complexes of nickel(II), having general formula [Ni(L1)(PPh3)] (1), [Ni(L1)(4-picoline)] (2), and [Ni(L2)(4-picoline)] (3) were synthesized by the reaction of Ni(OAc)2·4H2O with corresponding benzolyhydrazine-derived Schiff base ligands i.e. [4-(diethylamino)-2-hydroxybenzylidene]-benzohydrazonic acid (H2L1) or [2-(hydroxynaphthalen-1-yl)methylene]-benzohydrazonic acid (H2L2) and PPh3/4-picoline as co-ligand in 1:1:1 ratio in methanol. All the three complexes were air-stable, isolated as reddish brown solids and characterized by Elemental analysis, FT-IR, 1H, 13C{1H}, 31P{1H} NMR spectroscopy and mass spectrometry. The structures of all three complexes were determined by single crystal X-ray diffraction studies which revealed the distorted square planar geometry of the complexes. In these complexes, three coordination sites were occupied by ONO pincer type Schiff base ligand and the fourth site was blocked by phosphorus (P) or nitrogen (N) atom of the co-ligand. The catalytic potential of all three complexes was explored in the synthesis of a series of 2-arylbenzoxazoles from aldehydes and 2-aminophenol, using low catalyst loading (0.5 mol%). Complex 1 was found to be the best catalyst among three complexes, for the synthesis of a series of 2-aryl benzoxazoles. The ease of synthesis, air-stability and robustness of the catalyst, and good TONs are some of the key characteristics of the described catalytic system.
- Layek, Samaresh,Agrahari, Bhumika,Kumar, Akash,Dege, Necmi,Pathak, Devendra D.
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- In-vitro Anti-cancer assay and apoptotic cell pathway of newly synthesized benzoxazole-N-heterocyclic hybrids as potent tyrosine kinase inhibitors
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A series of benzoxazole-N-heterocyclic hybrids have been synthesized by a one-pot strategy. Molecular docking study revealed that such compounds have the ability to inhibit enzyme protein tyrosine kinase. The findings of this work have been the successful synthesis of benzoxazole scaffolds, featuring hybrids of benzoxazole with quinoline and quinoxaline respectively. The molecular docking studies have showed these compounds to be inhibitors of tyrosine kinase enzyme which triggers growth of cancer cells. The cytotoxicity study of compounds 4a-f showed better potency against breast cancer cell lines MCF-7 and MDA-MB-231 in contrast to oral and lung cancer cell lines KB and A549. The tyrosine kinase activity was measured using Universal Tyrosine Kinase Assay kit using horseradish peroxide (HRP)-conjugated anti-phosphotyrosine kinase solution as a substrate. The compounds 4c exhibited maximum inhibition in the activity of enzyme tyrosine kinase with IC50 value 0.10 ± 0.16 μM, than other compounds which were studied and thus proved to be inhibitors of enzyme tyrosine kinase. The selective index of all four compounds was found out to be greater than two, indicating the non-toxic behaviour, i.e. good anti-cancer activity. Further, fluorescence microscopic study helped to characterize the mode of cell death, which was found to be late apoptosis as indicated by the orange fluorescence. The SAR analysis has also been carried out.
- Desai, Sulaksha,Desai, Vidya,Shingade, Sunil
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supporting information
(2019/11/13)
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- Hemoglobin: A New Biocatalyst for the Synthesis of 2-substituted Benzoxazoles via Oxidative Cyclization
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Efficient and mild synthesis of a series of 2-substituted benzoxazoles via oxidative cyclization catalyzed by hemoglobins reported here for the first time. Satisfactory yields (84 %–97 %) and mild reaction conditions make this method highly viable for practical applications.
- Li, Fengxi,Li, Zhengqiang,Tang, Xuyong,Cao, Xinyu,Wang, Chunyu,Li, Jialin,Wang, Lei
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p. 1192 - 1195
(2019/02/07)
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- A 2 - substituted benzoxazole derivative of the preparation method
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The invention discloses a 2 - substituted benzoxazole derivative of the preparation method, its reaction as follows: . The present invention can be 2 - substituted pyrrole derivatives, acetophenone derivatives can be obtained and at the same time 2, 2 - dihalo acetophenone derivatives; and through the C (sp2 ) - C (sp2 ) At the same time selectively fracture of the aromatization. The method of the invention the resulting raw materials are easy, high yield, mild reaction conditions, the reaction time is short, wide substrate range, reaction specificity is strong, easy post treatment and green environmental protection.
- -
-
Paragraph 0066-0069
(2019/07/04)
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- Deep eutectic solvent-catalyzed arylation of benzoxazoles with aromatic aldehydes
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A novel and efficient methodology for the arylation of benzoxazoles with aromatic aldehydes catalyzed by deep eutectic solvent has been developed. The reaction smoothly proceeded with a wide range of substrates to give the desired products in high yields within short reaction time. Deep eutectic solvents are easily recovered and reused without significant loss of catalytic activity.
- Tran, Phuong Hoang,Thi Hang, Anh-Hung
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p. 11127 - 11133
(2018/03/26)
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- Oxidative NHC Catalysis for the Generation of Imidoyl Azoliums: Synthesis of Benzoxazoles
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N-Heterocyclic carbene (NHC)-catalyzed intramolecular cyclization of aldimines generated from 2-amino phenols and aromatic aldehydes leading to the synthesis of 2-arylbenzoxazoles under mild conditions is presented. The reaction proceeds via the generation of the aza-Breslow intermediates from imines and NHC, which under oxidative conditions form the key imidoyl azoliums and a subsequent intramolecular cyclization furnishes the product. The reaction tolerates a broad range of functional groups, and the products are formed in generally good yields.
- Patra, Atanu,James, Anjima,Das, Tamal Kanti,Biju, Akkattu T.
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p. 14820 - 14826
(2019/01/03)
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- Synthesis and characterization of a novel oxo-bridged binuclear iron(iii) complex: Its catalytic application in the synthesis of benzoxazoles using benzyl alcohol in water
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In the present work, the synthesis and characterization of a novel binuclear oxo-bridged iron(iii) complex, (FeLAPIP)2O, where LAPIP is the deprotonated form of a tetradentateo-aminophenol-iminopyridine ligand, is described. The iron complex was characterized using different techniques including X-ray crystallography, infrared spectroscopy, UV-Vis, magnetic susceptibility and cyclic voltammetry. The X-ray structure analysis revealed that in the structure of the (FeLAPIP)2O complex, each iron(iii) is coordinated in a distorted square pyramidal arrangement by an oxo group, three amine nitrogens and one oxygen atom of the o-aminophenolate ligand. The variable-temperature magnetic measurement exhibits strong antiferromagnetic coupling between two iron(iii) centers. Cyclic voltammetry measurements showed two kinds of quasireversible events, suggesting the formation of a phenoxyl radical species in the region of the anodic peaks and a metal-centered redox (FeIII/FeII) process at low potential. The catalytic activity of this Fe-complex was evaluated in coupling of 2-aminophenol and benzyl alcohols for the one-pot synthesis of benzoxazoles. The catalyst system showed high catalytic activity in this transformation and benzoxazole derivatives were obtained in good to excellent yields. tert-Butyl hydroperoxide was used as an oxidant and 1.2 mol% of catalyst was needed to accomplish the reaction in water as the green solvent.
- Safaei, Elham,Alaji, Zahra,Panahi, Farhad,Wojtczak, Andrzej,Jagli?i?, Janez Zvonko
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supporting information
p. 7230 - 7236
(2018/05/07)
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- Phosphonium acidic ionic liquid: An efficient and recyclable homogeneous catalyst for the synthesis of 2-Arylbenzoxazoles, 2-Arylbenzimidazoles, and 2-Arylbenzothiazoles
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A highly efficient and green strategy for the synthesis of 2-Arylbenzoxazoles, 2-Arylbenzimidazoles, and 2-Arylbenzothiazoles catalyzed by phosphonium acidic ionic liquid has been developed via the condensation of o-Aminophenol, o-phenylenediamines, and o-Aminothiophenol, respectively, with aldehydes. The reaction has a good yield, the broad substrate scope, and mild condition. Triphenyl(butyl-3-sulphonyl)phosphonium toluenesulfonate catalyst was easily obtained from cheap and available starting materials through a one-pot synthesis. Its structure was identified by 1H NMR, 13C NMR, 31P NMR, and FT-IR techniques. Other properties including thermal stability and acidity were determined by TGA and Hammett acidity function method. Interestingly, the catalyst can maintain its constantly outstanding performance till the fourth recovery.
- Nguyen, Quang The,Thi Hang, Anh-Hung,Ho Nguyen, Thuy-Linh,Nguyen Chau, Duy-Khiem,Tran, Phuong Hoang
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p. 11834 - 11842
(2018/04/05)
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- Palladium(II) Immobilized Onto the Glucose Functionalized Magnetic Nanoparticle as a New and Efficient Catalyst for the One-pot Synthesis of Benzoxazoles
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Palladium(II) have been immobilized into the nano magnetic Fe3O4 which was functionalized with glucose in order to achieve a one-pot synthesis of 2-substituted benzoxazole derivatives with high yields in the diverse range of organic solvents. The nano catalyst is highly dispersive in polar solvents and can be easily recovered and reused for 6 runs without significant loss of its activity. Finally, the catalyst was fully characterized by FT-IR, TGA, CHN, SEM, EDX and atomic absorption spectroscopy.
- Moghaddam, Firouz Matloubi,Saberi, Vahid,Kalhor, Sepideh,Veisi, Nazila
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- OMS-2/H2O2/Dimethyl Carbonate: An Environmentally-Friendly Heterogeneous Catalytic System for the Oxidative Synthesis of Benzoxazoles at Room Temperature
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A manganese octahedral molecular sieve (OMS-2) was found to be an efficient and recyclable heterogeneous catalyst for the oxidative synthesis of benzoxazoles in the gram-scale from phenolic imines at room temperature. H2O2 and biobased reagent dimethyl carbonate (DMC) were successfully employed as the environmentally friendly oxidant and solvent, respectively, in an OMS-2-catalysted redox reaction for the first time. Benzoxazoles could also be obtained from N-substituted 2-aminophenols via Cu(OH)x/OMS-2-catalyzed sequential oxidative transformation at elevated temperatures.
- Meng, Xu,Wang, Yuanguang,Chen, Baohua,Chen, Gexin,Jing, Zhenqiang,Zhao, Peiqing
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supporting information
p. 2018 - 2024
(2017/12/26)
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- Method for preparing benzoxazole compound by heterogeneous catalytic oxidation
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The invention discloses a method for preparing a benzoxazole compound by heterogeneous catalytic oxidation. The method comprises the following steps: mixing phenolic Schiff base, an OMS-2 type manganese oxide octahedral molecular sieve, an oxidant and carbonic esters and reacting to obtain the benzoxazole compound, wherein structures of the phenolic Schiff base and the benzoxazole compound are respectively shown as formulas I and II: the formula I is shown in the description and the formula II is shown in the description, wherein R can be selected from hydrogen, alkyl, alkoxyl, hydroxyl, an ester group, a carboxylic group or halogen; R can be selected from alkyl, aryl and alkenyl. According to the method disclosed by the invention, a green catalytic reaction system which is composed of a heterogeneous catalyst OMS-2 type manganese oxide molecular sieve, a green oxidant H2O2 and a green medium carbonate and has a long service life and is cheap is adopted, so that an acid-alkali additive can be avoided; the catalyst has high activity and a long service life; the method disclosed by the invention is simple to operate and has moderate reaction conditions; new three wastes are not generated and the method is clean and environmentally friendly; the solvent treatment cost can be reduced and the conversion rate of reactants and the yield of a target product are improved, so that the method can be more adaptive to industrial application to the greater extent.
- -
-
Paragraph 0033; 0034
(2017/10/28)
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- Environmental benign synthesis of novel double layered nano catalyst and their catalytic activity in synthesis of 2-substituted benzoxazoles
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Synthesis of Cu-Al hydrotalcite by co precipitation method is being described. Synthesized nano catalyst has been characterized by powder X-ray diffraction, scanning electron microscopy, FT-IR and thermogravimetric analyses which confirm hydrotalcite-like structure. Effect of molar concentration, catalyst loading, reaction time and catalytic activity have been investigated in the synthesis of benzoxazoles under solvent free conditions using 2-amino phenol and benzoyl chloride. The influence of the hydrotalcite and their different amounts on reactivity was studied. Catalyst can be recycle and used for further reaction without losing its activity.
- Gupta, Ruchi,Sahu, Pramod K.,Sahu, Praveen K.,Srivastava,Agarwal
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p. 119 - 123
(2017/01/25)
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- Catalyst-free microwave-promoted one pot synthesis of 2-aryl benzoxazoles using MnO2 nanoparticles as a convenient oxidant under mild condition
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Abstract: An efficient and facile protocol for one pot synthesis of a series of 2-aryl benzoxazoles through coupling of o-aminophenol with aromatic aldehydes under microwave irradiation in the presence of MnO2 nanoparticles as oxidant reagent was demonstrated. The MnO2 nanoparticles were prepared via a solid-state chemical reaction technique. The structure of oxidant was assigned by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The target molecules were obtained in good to high yields, high purity and short reaction times. The pure products were identified and characterized by physical and spectral data such as; melting point, IR, 1H NMR and 13C NMR. Graphical Abstract: An efficient and facil protocol for one pot synthesis of a series of 2-aryl benzoxazoles through coupling of o-aminophenol with aromatic aldehydes under microwave irradiation in the precense of MnO2 nanoparticles as oxidant reagent was demonstrated.
- Naeimi, Hossein,Rouzegar, Zahra,Rahmatinejad, Soraya
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p. 4745 - 4758
(2017/07/22)
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- Sonocatalyzed facile synthesis of 2-aryl benzoxazoles using MnO2 nanoparticles as oxidant agent under mild conditions
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Nano MnO2 was found to be an efficient oxidant agent for the synthesis of 2-substituted benzoxazoles through one-pot reaction of o-aminophenol and different aromatic aldehydes in acetonitrile under ultrasonic irradiation. This method was performed under mild conditions with high yields, inexpensive and readily available oxidant agent, facile and easy experimental procedure, simple purification of final products, and short reaction times. The prepared nano MnO2 has been characterized by FTIR, XRD, and SEM techniques. The pure products were identified and characterized by physical and spectroscopic data such as; melting point, IR, 1H NMR, and 13C NMR.
- Naeimi, Hossein,Rouzegar, Zahra,Rahmatinejad, Soraya
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supporting information
p. 2087 - 2095
(2017/10/26)
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- Magnetic Co-doped NiFe2O4 Nanocomposite: A Heterogeneous and Recyclable Catalyst for the One-Pot Synthesis of Benzimidazoles, Benzoxazoles and Benzothiazoles under Solvent-Free Conditions
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A simple and efficient procedure for the synthesis of benzimidazoles, benzoxazoles, and benzothiazoles via the condensation of o-phenylenediamine, o-aminophenol, and o-aminothiophenol with various benzaldehydes by using magnetic Co-doped NiFe2O4 nanoparticles has been developed. This nanocatalyst has advantages such as excellent product yields, solvent-free conditions, and very short reaction times. After any experiment, the magnetic nanocatalyst could be easily separated with the aid of an external magnet and reused at least four times without any loss of its catalytic performance.
- Karimian, Azam,Mohammadzadeh Kakhki, Roya,Kargar Beidokhti, Hamideh
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p. 1316 - 1325
(2017/11/22)
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- One-pot green synthesis of benzoxazole derivatives through molecular sieve-catalyzed oxidative cyclization reaction
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An one-pot approach to benzoxazole ring from 2-aminophenol and aldehydes utilizing molecular sieve as the catalyst have been developed. The new oxidative cyclization reaction excluded the usage of hazardous chemical reagents, transition-metal catalysts, chemical oxidants, or strong acids, and, therefore, reduced the production of toxic chemical waste. This offers an environmentally friendly pathway for the synthesis of various benzoxazole derivatives.
- Chang, Weichieh,Sun, Yukai,Huang, Yungtzung
-
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- Sustainable Synthesis of 2-Arylbenzoxazoles over a cobalt-based nanocomposite catalyst
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A new cobalt-based heterogeneous catalyst was prepared by adsorbing in situ produced nitrogen-ligated cobalt(II) acetate complexes on commercially available SiO2 and subsequent pyrolysis at 800 °C for 2 h under N2 atmosphere. By applying this catalyst under the O2 balloon, the aerobic oxidation of phenolic imines proceeded smoothly and gave various 2-arylbenzoxazoles in good yields. Meanwhile, on the basis of the experimental results, a plausible reaction pathway was described to elucidate the reaction mechanism.
- He, Jian,Lin, Fu,Yang, Xufang,Wang, Di,Tan, Xiaohua,Zhang, Shujun
-
supporting information
p. 1093 - 1096
(2017/01/16)
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- Microwave Assisted Synthesis of Two-Substituted Benzoxazoles in the Presence of Potassium Cyanide under Mild Conditions
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Various two-substituted benzoxazoles were prepared using microwave-assisted reaction of 2-aminophenol with aromatic aldehydes in the presence of one equivalent of potassium cyanide as an equimolecular catalyst. Aldehydes having either electron-donating or withdrawing groups afforded the target products. The important features of this method were high yields, short reaction times and easy work up. The structure of synthesized products was characterized by nuclear magnetic resonance (NMR) and infrared (IR).
- Naeimi, Hossein,Rahmatinejad, Soraya
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p. 471 - 476
(2015/11/02)
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- Graphene oxide as a heterogeneous reagent promoted synthesis of 2-substituted 1,3-benzazoles in water
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An efficient chemical method for the synthesis of benzimidazoles, benzothiazoles, and benzoxazoles has been developed through the condensation of various aldehydes with o-phenylenediamine, o-aminothiophenol, and o-aminophenol using graphene oxide (GO) as an oxidant in water. These benzazoles are also prepared through a one-pot oxidation/condensation tandem process by reacting alcohols with 2-amino-(thio)phenol/aniline in the presence of GO in poly(ethylene glycol) as a safe media. Moreover, this carbonaceous material could be readily separated using a simple filtration.
- Khalili, Dariush,Banazadeh, Ali Reza
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p. 1693 - 1706
(2016/01/26)
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- Ligand-promoted, copper nanoparticles catalyzed one-pot synthesis of substituted benzoxazoles from 2-bromoanilines and acyl chlorides
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A facile, highly efficient, and practical one-pot synthetic strategy for benzoxazoles was developed by using copper nanoparticles as a catalyst with o-bromoanilines and acyl chlorides as starting materials. With the promotion of 1,10-phenanthroline ligand, the copper nanoparticles catalyst showed highly catalytic activity under mild conditions. This methodology is tolerant of a wide variety of functional groups and gives good to excellent yields in most examples. Furthermore, the solid catalyst could be recovered and reused conveniently several times with satisfactory yields.
- Wang, Yong,Wu, Chaolong,Nie, Shoujie,Xu, Dingjian,Yu, Min,Yao, Xiaoquan
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supporting information
p. 6827 - 6832
(2015/11/27)
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- Trichloroisocyanuric Acid/Triphenylphosphine-Mediated Synthesis of Benzimidazoles, Benzoxazoles, and Benzothiazoles
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A new and efficient method for preparation of benzimidazoles, benzoxazoles, and benzothiazoles from reactions of different carboxylic acids with o-phenylenediamine, o-aminophenol, and o-aminothiophenol in the presence of triphenylphosphine/trichloroisocyanuric acid system is presented. The desired products have been characterised on the basis of spectral (infrared, NMR, mass spectrometry) data, and the mechanism of their formation is proposed. The remarkable advantages are the inexpensive and readily available reagent, simple procedure, mild conditions, and good-to-excellent yields.
- Rezazadeh, Soodabeh,Akhlaghinia, Batool,Razavi, Nasrin
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p. 145 - 155
(2015/05/05)
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- Palladium catalyzed Csp2-H activation for direct aryl hydroxylation: The unprecedented role of 1,4-dioxane as a source of hydroxyl radicals
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A novel strategy for direct aryl hydroxylation via Pd-catalysed Csp2-H activation through an unprecedented hydroxyl radical transfer from 1,4-dioxane, used as a solvent, is reported with bio relevant and sterically hindered heterocycles and various acyclic functionalities as versatile directing groups.
- Seth, Kapileswar,Nautiyal, Manesh,Purohit, Priyank,Parikh, Naisargee,Chakraborti, Asit K.
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p. 191 - 194
(2015/01/09)
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- Unexpectedly Simple Synthesis of Benzazoles by tBuONa-Catalyzed Direct Aerobic Oxidative Cyclocondensation of o-Thio/Hydroxy/Aminoanilines with Alcohols under Air
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tBuONa-catalyzed direct aerobic oxidative cyclocondensation reactions of readily available alcohols and o-thio/hydroxy/aminoanilines under air have been developed and provide an efficient, practical, and green method for the synthesis of benzazoles. Mechanistic studies revealed that o-substituted anilines promote the initial aerobic alcohol-oxidation step, which explains the high reactivity and success of this unexpectedly simple and practical cyclocondensation method. Simple and straight: tBuONa-catalyzed direct aerobic oxidative cyclocondensation reactions of readily available alcohols and o-thio/hydroxy/aminoanilines under air provide an efficient, practical, and green method for the synthesis of benzazole heterocycles (see scheme). Mechanistic studies revealed that o-substituted anilines promote the initial aerobic alcohol-oxidation step.
- Shi, Xinkang,Guo, Junmei,Liu, Jianping,Ye, Mingde,Xu, Qing
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supporting information
p. 9988 - 9993
(2015/07/07)
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- Ag@TiO2 nanocomposite; Synthesis, characterization and its application as a novel and recyclable catalyst for the one-pot synthesis of benzoxazole derivatives in aqueous media
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In the present study, we use a Ag@TiO2 nanocomposite for the efficient synthesis of benzoxazole derivatives via the one-pot condensation of 2-aminophenol and several aromatic aldehydes or orthoesters or carboxylic acids or amides or acyl chlorides in water at room temperature. In all situations the preferred products were synthesized with excellent yields. The short reaction times, high yields, safety and mild conditions, simplicity, non-toxicity and easy workup are the main merits of this protocol.
- Maleki, Behrooz,Baghayeri, Mehdi,Vahdat, Seyed Mohammad,Mohammadzadeh, Abbas,Akhoondi, Somaieh
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p. 46545 - 46551
(2015/06/16)
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- Ruthenium-catalyzed synthesis of benzoxazoles using acceptorless dehydrogenative coupling reaction of primary alcohols with 2-aminophenol under heterogeneous conditions
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An efficient ruthenium-catalyzed acceptorless dehydrogenative coupling reaction of primary alcohols with 2-aminophenol for one-pot synthesis of benzoxazoles is introduced. The phosphine-functionalized magnetic nanoparticles (PFMNPs; Fe3O4@SiO2@PPh2) as a magnetic recyclable phosphorus ligand in the presence of Ru2Cl 4(CO)6 was found to be an efficient heterogeneous catalytic system for promotion of the designed protocol. The reaction was carried out efficiently with a variety of substrates to give the corresponding products in moderate to good yields.
- Khalafi-Nezhad, Ali,Panahi, Farhad
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p. 1686 - 1692
(2014/06/24)
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- Synthesis of 2-arylbenzoxazoles through oxidation of C-H bonds adjacent to oxygen atoms
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A practical and simple synthesis of benzoxazoles from easily available substrates was developed. The protocol is triggered by an iron-catalyzed tandem oxidative process from simple ether derivatives. A practical and simple synthesis of benzoxazoles from easily available substrates is developed. The protocol is triggered by an iron-catalyzed tandem oxidative process from simple ether derivatives. Copyright
- Gu, Lijun,Wang, Wei,Xiong, Yong,Huang, Xiangzhong,Li, Ganpeng
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p. 319 - 322
(2014/01/23)
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- Synthesis of 2-Arylbenzoxazoles through Oxidation of C-H Bonds Adjacent to Oxygen Atoms
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A practical and simple synthesis of benzoxazoles from easily available substrates was developed. The protocol is triggered by an iron-catalyzed tandem oxidative process from simple ether derivatives.
- Gu, Lijun,Wang, Wei,Xiong, Yong,Huang, Xiangzhong,Li, Ganpeng
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p. 319 - 322
(2015/10/05)
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- Synthesis of 2-substituted pyrimidines and benzoxazoles via a visible-light-driven organocatalytic aerobic oxidation: Enhancement of the reaction rate and selectivity by a base
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An efficient visible-light-driven photocatalytic oxidation of various 2-substituted dihydropyrimidines and phenolic imines has been achieved using an organic photocatalyst eosin Y bis(tetrabutyl ammonium salt) (TBA-eosin Y) and inexpensive oxidant molecular oxygen. With the aid of a base, significantly enhanced photoinduced electron transfer from substrates dihydropyrimidines or phenolic imines to the excited state of TBA-eosin Y has enabled the aerobic oxidation to yield 2-(methylthio)pyrimidines or 2-arylbenzoxazoles selectively. This journal is the Partner Organisations 2014.
- Wang, Lin,Ma, Zhi-Gang,Wei, Xiao-Jing,Meng, Qing-Yuan,Yang, Deng-Tao,Du, Shao-Fu,Chen, Zi-Fei,Wu, Li-Zhu,Liu, Qiang
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supporting information
p. 3752 - 3757
(2014/08/05)
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- Tri-lacunary polyoxometalates of Na8H[PW9O 34] as heterogeneous Lewis base catalysts for Knoevenagel condensation, cyanosilylation and the synthesis of benzoxazole derivatives
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We reported for the first time the development of tri-lacunary polyoxometalates (POMs) of Na8H[A-PW9O34] ·7H2O and Na8H[B-PW9O 34]·19H2O (Na-A-PW9 and Na-B-PW 9) as highly selective and efficient heterogeneous Lewis base catalysts for Knoevenagel condensation, cyanosilylation of various aldehydes and ketones and the synthesis of benzoxazole derivatives at 25 C under mild conditions. Since both Na-A-PW9 and Na-B-PW9 display no characteristic porosity, it is proposed that the catalytic reactions proceed not only on the surface and interface, but also in the bulk phase. The catalysts can be easily recovered and reused for at least six times without obvious decrease of catalytic activities and the structures of the catalysts remain unchanged after recycling. The easy preparation, high efficiency, reusability of the heterogeneous catalysts of Na-A-PW9 and Na-B-PW9 exhibit great potential for further application.
- Zhao, Shen,Chen, Yang,Song, Yu-Fei
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p. 140 - 146
(2014/03/21)
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- Application of nano SnO2 as a green and recyclable catalyst for the synthesis of 2-aryl or alkylbenzoxazole derivatives under ambient temperature
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Application of nano SnO2 as an efficient and benign catalyst has been explored for the synthesis of 2-aryl or alkylbenzoxazole derivatives via condensation reaction of aldehyde with 2-aminophenol. The reactions proceed under heterogeneous and mild conditions in ethanol at room temperature to provide 2-aryl or alkylbenzoxazoles in high yields.
- Vahdat, Seyed Mohammad,Raz, Shima Ghafouri,Baghery, Saeed
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p. 579 - 585
(2014/07/07)
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- Magnetic nanoparticles-supported tungstosilicic acid: As an efficient magnetically separable solid acid for the synthesis of benzoazoles in water
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The magnetic nanoparticles-supported tungstosilicic acid (TSAMNP) was found to be a highly efficient solid acid for the synthesis of benzoazoles in water. TSAMNP catalyst was achieved by the immobilization of tungstosilicic acid [H4(W12SiO40)] species on the silica core-shell magnetic nanoparticles (Fe3O4@SiO2). A variety of aldehydes were successfully condensed with 1,2-diaminobenzene, 2-aminophenol and 2-aminothiophenol in water as a green solvent to synthesize benzoazoles in good-to-excellent yields. TSAMNP catalyst was easily separated from the reaction mixture and reused several times without any loss of efficiency.
- Khalafi-Nezhad, Ali,Panahi, Farhad,Yousefi, Reza,Sarrafi, Sina,Gholamalipour, Yasaman
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p. 1311 - 1319
(2014/11/07)
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- One-pot synthesis of 2-substituted benzoxazoles promoted by copper acetate monohydrate
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An efficient synthesis of 2-substituted benzoxazoles via copper acetate monohydrate oxidative coupling of aldehydes with o-aminophenol is described. This synthetic strategy has some advantages as simple procedure, inexpensive and easily available catalyst, and facile isolation of the products in moderate to good yields.
- Chen, Guo-Feng,Shen, Hai-Dong,Zhang, Li-Yan,Li, Hong-Yang,Lan, Rui-Jia,Chen, Bao-Hua,Li, Ji-Tai,Hu, Qing-Hui
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p. 180 - 187
(2014/05/20)
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- Base-promoted formal arylation of benzo[d]oxazoles with acyl chloride
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A base-promoted formal arylation of benzo[d]oxazoles with acyl chloride was achieved in moderate to good yields. This reaction was triggered by the N-acylation of oxazole to form an iminium intermediate. Then, the addition of H2O to the iminium formed the hemiacetal intermediate. After the sequential ring-opening, extrusion of CO, the ring closure, the dehydration delivered the formal arylation product. In comparison with the transition-metal-catalyzed methodology, it represents an alternative arylation method leading to 2-arylbenzooxazole.
- Wang, Lei,Ren, Xinyi,Yu, Jintao,Jiang, Yan,Cheng, Jiang
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p. 12076 - 12081
(2014/01/06)
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- Iron-catalyzed 2-arylbenzoxazole formation from o-nitrophenols and benzylic alcohols
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The iron-catalyzed 2-arylbenzoxazole formation from o-nitrophenols and benzylic alcohols using hydrogen transfer is described. Various 2-arylbenzoxazoles were selectively obtained in good to excellent yields. The reaction tolerated a wide range of functionalities. The alcohol oxidation, nitro reduction, condensation, and dehydrogenation were realized in a cascade without external reducing reagent and oxidant.
- Wu, Mingyue,Hu, Xiong,Liu, Juan,Liao, Yunfeng,Deng, Guo-Jun
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supporting information; experimental part
p. 2722 - 2725
(2012/07/28)
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- Palladium-catalyzed deamidative arylation of azoles with arylamides through a tandem decarbonylation-C-H functionalization
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A highly chemo-, regio-selective, and efficient palladium-catalyzed deamidative arylation of azoles with arylamides, as an aryl metal equivalent, has been developed. The reaction proceeds smoothly to generate the corresponding products in good yields via a tandem decarbonylation-C-H activation.
- Li, Chengliang,Li, Pinhua,Yang, Jin,Wang, Lei
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supporting information; experimental part
p. 4214 - 4216
(2012/05/04)
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- Microwave-assisted one-pot synthesis of benzothiazole and benzoxazole libraries as analgesic agents
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Microwave-assisted synthesis of benzothiazole and benzoxazole libraries via PIFA promoted cyclocondensation of 2-aminothiophenols/2-aminophenols with aldehydes under one-pot condition in good to excellent yields was achieved. Twenty compounds have been investigated for their analgesic activity and showed moderate to good activity. Indian Academy of Sciences.
- Praveen,Nandakumar,Dheenkumar,Muralidharan,Perumal
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experimental part
p. 609 - 624
(2012/08/28)
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- An efficient synthesis of 2-substituted benzoxazoles via RuCl 3·3H2O catalyzed tandem reactions in ionic liquid
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An efficient synthesis of 2-substituted benzoxazoles through RuCl 3·3H2O catalyzed, air oxidized tandem reactions of 2-aminophenols and aldehydes in [bmim]BF4 was developed. This synthetic strategy has such advantages as mild reaction conditions, cost-free oxidant, readily available starting materials, and recyclable catalyst and solvent. As an application, it was successfully used in the synthesis of the unreported 5-(benzoxazol-2-yl)-2′-deoxyuridines with potential biological activities. A novel and efficient synthesis of 2-substituted benzoxazoles through RuCl3 catalyzed, air oxidized tandem reactions of 2-aminophenols and aldehydes in [bmim]BF4 was developed.
- Fan, Xuesen,He, Yan,Wang, Yangyang,Zhang, Xinying,Wang, Jianji
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experimental part
p. 773 - 777
(2011/11/12)
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- An Efficient and practical synthesis of benzoxazoles from acyl chlorides and 2-aminophenols catalyzed by Lewis acid in(OTf)3 under solvent-free reaction conditions
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Benzoxazole derivatives have been prepared through the reaction of substituted 2-aminophenols and acyl chlorides in the presence of catalytic amount of In(OTf)3 under solvent-free reaction conditions in good to excellent yields. The method is simple, convenient, environmental-friendly, efficient and practical.
- Wang, Bo,Zhang, Yicheng,Li, Pinhua,Wang, Lei
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experimental part
p. 1697 - 1703
(2011/06/27)
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- An efficient procedure for the synthesis of benzoxazole and benzothiazole derivatives using a H2O2/SiO2-FeCl3 system
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A series of benzoxazole and benzothiazoles was readily prepared from the reaction of ortho-aminophenol/ortho-aminothiophenol and aldehydes using solid silica supported ferric chloride (SiO2-FeCl3) as catalyst followed by oxidation with H2O2 under ambient conditions. Some of advantages of this method are a simple and convenient procedure, easy purification, and shorter reaction times. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor & Francis Group, LLC.
- Mosslemin, Mohammad Hossein,Fazlinia, Abbas
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experimental part
p. 2165 - 2170
(2011/01/12)
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- One-pot synthesis of 2-substituted benzoxazoles directly from carboxylic acids
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Methanesulfonic acid has been found to be a highly effective catalyst for a convenient and one-pot synthesis of 2-substituted benzoxazoles by the reaction of 2-aminophenol with acid chlorides, generated in situ from carboxylic acids. Aryl, heteroaryl, and arylalkyl carboxylic acids provided excellent yields of the corresponding benzoxazoles. The reaction conditions were compatible with various substituents such as chloro, bromo, nitro, methoxy, cyclopentyloxy, phenoxy, thiophenoxy, and conjugated double bonds. Benzoxazole formation was found to be general with respect to substituted 2-aminophenols.
- Kumar, Dinesh,Rudrawar, Santosh,Chakraborti, Asit K.
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scheme or table
p. 881 - 887
(2009/04/11)
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- Oxidative cyclization of thiophenolic and phenolic Schiff's bases promoted by PCC: a new oxidant for 2-substituted benzothiazoles and benzoxazoles
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Pyridinium chlorochromate (PCC) supported on silica gel effects the oxidative cyclization of structurally diverse thiophenolic and phenolic Schiff's bases, thereby providing an efficient and convenient method for the synthesis of a library of 2-arylbenzot
- Praveen,Kumar, K. Hemanth,Muralidharan,Perumal
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p. 2369 - 2374
(2008/09/18)
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