- 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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- Anti-bacterial, catalytic and docking behaviours of novel di/trimeric imidazolium salts
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Flexible di/trimeric substituted imidazolium salts are prepared under conventional/solvent free silica supported approaches. Solid supported approaches are superior than the conventional method like environment friendly, higher yield, shorter reaction time and easy workup procedure. We have studied the catalytic activities of our synthesized di/trimeric imidazolium salts for one-pot preparation of benzoxazole derivatives under conventional/Muffle furnace conditions. We have monitored the efficiency of recycled flexible di/trimeric imidazolium salts up to fourth cycles showed excellent responses. We have studied the MIC and MBC of our di/trimeric imidazolium salts against Gram positive/negative microorganisms under micro dilution method. Nitro substituted imidazolium salts showed excellent screening responses than the unsubstituted compounds. Computer assisted docking analysis is carried out for all our synthesized compounds. The host-guest interaction via hydrogen bonding between standard and our drug molecules against various human Gram positive and negative pathogens are compared. From the docking analysis, our drug molecules showed effective interaction against test pathogens.
- Ganapathi, Pandurangan,Ganesan, Kilivelu
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p. 452 - 464
(2017/03/24)
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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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- 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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- 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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- Sonicated assisted synthesis of benzimidazoles, benzoxazoles and benzothiazoles in aqueous media
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Ammonium nickel sulphate [(NH4)2SO4.NiSO4.6H2O] was found as a new catalyst to synthesis 2-aryl benzimidazole, 2-aryl benzothiazole and 2-aryl benzoxazole in aqueous media under sonication irradiation. The procedure is an eco-friendly, efficient and provides simple workup and good yield.
- Pardeshi, Sandeep D.,Sonar, Jayant P.,Pawar, Shivaji S.,Dekhane, Deepak,Gupta, Sunil,Zine, Ashok M.,Thore, Shivaji N.
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p. 2335 - 2340
(2014/07/22)
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- Poly (ethylene glycol)-bound sulphonic acid as a novel catalyst for synthesis of benzoxazoles
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ABSTRACT Ahighly efficient, simple and rapid method for the preparation of various 2-aminobenzoxazoles and other benzoxazole derivatives using a catalytic amount of poly (ethylene glycol)-bound sulphonic acid (PEG-SO3H) is described. PEG-SO3H is found to be economical and reusable catalyst with low catalytic loading. The percentage yield was found to be satisfactory, experimental set-up and purification of final products is facile and easy. GRAPHICAL ABSTRACT.
- Chikhale, Rupesh V.,Pant, Amit M.,Menghani, Sunil S.,Wadibhasme, Pankaj G.,Khedekar, Pramod B.
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p. 254 - 262
(2013/12/04)
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- Synthesis and in vitro antibacterial and antifungal activities of benzoxazole derivatives
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The in vitro antibacterial and antifungal activities of twenty-nine (29) benzoxazole derivatives were tested against fifteen Gram-positive and sixteen Gram-negative strains. Out of the twenty-nine compounds, eighteen compounds 3-5, 7-9, 11-13, 15-25 showed a broad range of activity against tested Gram-positive microorganisms, whereas rest of the compounds 6, 10, 14 and 26-31 were found to be completely inactive against all the tested strains of Gram-positive bacteria. Five compounds 8, 11-13, and 15 showed activities against Gram-negative strains whereas the rest were devoid of any activity. Twenty-one (21) out of twenty-nine (29) compounds possessed antifungal activity. The structures of the synthetic compounds were confirmed by IR, EIMS and 1HNMR spectral data.
- Khan, Khalid Mohammed,Karim, Aneela,Ambreen, Nida,Amyn, Afroz,Saied, Sumayya,Ahmed, Aqeel,Perveen, Shahnaz
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p. 894 - 900
(2013/07/26)
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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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- Iron-catalyzed intramolecular O-arylation: Synthesis of 2-aryl benzoxazoles
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(Chemical Equation Presented) A practical iron-catalyzed intramolecular O-arylation reaction and its application in the synthesis of benzoxazole derivatives, starting from the readily available 2-haloanilines, is presented. The key cyclization step involves the use of a combination of the cheap and environmentally friendly FeCl3 and 2,2,6,6-tetramethyl-3,5 heptanedione (TMHD) as the catalyst system.
- Bonnamour, Julien,Bolm, Carsten
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supporting information; experimental part
p. 2665 - 2667
(2009/05/27)
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- Alum (KAl(SO4)2·12H2O)-catalyzed, eco-friendly, and efficient one-pot synthesis of 2-arylbenzothiazoles and 2-arylbenzoxazole in aqueous medium
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Alum (KAl(SO4)212H2O) performs as a novel catalyst for the synthesis of 2-arylbenzothiazoles and 2-arylbenzoxazole from o-aminothiophenol and o-aminophenol with various substituted aldehydes in good to excellent isolated yields (8595%) using water as a solvent at ambient temperature. Several solvents were examined for this reaction; however, in terms of reaction yield and time, water was found to be the optimum solvent. The remarkable advantages offered by this method are an inexpensive and easily available catalyst, a simple procedure, mild conditions, much faster (6090 min) reactions, and good to excellent yields of products.
- Pawar, Shivaji S.,Dekhane, Deepak V.,Shingare, Murlidhar S.,Thore, Shivaji N.
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experimental part
p. 905 - 909
(2009/04/11)
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- Parallel synthesis of a library of benzoxazoles and benzothiazoles using ligand-accelerated copper-catalyzed cyclizations of ortho-halobenzanilides
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A general method for the formation of benzoxazoles via a copper-catalyzed cyclization of ortho-haloanilides is reported. This approach complements the more commonly used strategies for benzoxazole formation which require 2-aminophenols as substrates. The reaction involves an intramolecular C-O cross-coupling of the ortho-haloanilides and is believed to proceed via an oxidative insertion/reductive elimination pathway through a Cu(I)/Cu(III) manifold. The reaction is also applicable to the formation of benzothiazoles. A variety of ligands including 1,10-phenanthroline and N,N′- dimethylethylenediamine were shown to provide ligand acceleration/stabilization in the reaction. Optimal conditions for cyclization used a catalyst combination of CuI and 1,10-phenanthroline (10 mol %). The method was amenable to a parallel-synthesis approach, as demonstrated by the synthesis of a library of benzoxazoles and benzothiazoles substituted at various positions in the ring. Most examples utilized the cyclization of ortho-bromoanilides, but orthoiodoanilides and ortho-chloroanilides also undergo a reaction under these conditions. The rate of reaction of the ortho-haloanilides follows the order I > Br > Cl, consistent with oxidative addition being the rate-determining step.
- Evindar, Ghotas,Batey, Robert A.
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p. 1802 - 1808
(2007/10/03)
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