- Electrochemical Synthesis of Benzimidazoles via Dehydrogenative Cyclization of Amidines
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The development of efficient and sustainable methodologies for the synthesis of N-heterocycles is a constant focus of organic synthesis. Herein an electrochemical method is reported for the synthesis of benzimidazoles through dehydrogenative cyclization of easily available N-aryl amidines. The reactions were conducted under simple constant current conditions in an undivided cell without need for catalysts, chemical oxidants, or additives, and produced H2 as the only theoretical byproduct.
- Zhao, Huai-Bo,Zhuang, Jin-Liang,Xu, Hai-Chao
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p. 1692 - 1695
(2021/03/01)
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- Photoinduced Heterogeneous C?H Arylation by a Reusable Hybrid Copper Catalyst
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Heterogeneous copper catalysis enabled photoinduced C?H arylations under exceedingly mild conditions at room temperature. The versatile hybrid copper catalyst provided step-economical access to arylated heteroarenes, terpenes and alkaloid natural products with various aryl halides. The hybrid copper catalyst could be reused without significant loss of catalytic efficacy. Detailed studies in terms of TEM, HRTEM and XPS analysis of the hybrid copper catalyst, among others, supported its outstanding stability and reusability.
- Choi, Isaac,Müller, Valentin,Lole, Gaurav,K?hler, Robert,Karius, Volker,Vi?l, Wolfgang,Jooss, Christian,Ackermann, Lutz
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supporting information
p. 3509 - 3514
(2020/03/03)
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- Pyrazole-3-carboxylates assisted N-heterocyclic carbene palladium complexes: synthesis, characterization, and catalytic activities towards arylation of azoles with arylsulfonyl hydrazides
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Four mononuclear and dinuclear pyrazole-3-carboxylates assisted NHC–Pd complexes have been synthesized and characterized. Notably, the bridge-cleavage reactions of [Pd(μ-Cl)(Cl)(NHC)]2 with 1H-pyrazole-3-carboxylic acid afforded dinuclear complexes [(NHC)Pd(μ-1H-pyrazolato-3-carboxylate)]2, in which the 1H-pyrazolato-3-carboxylate was employed as a N^N^O dianionic chelating and bridging ligand. To further explore the structural features and catalytic properties of the complexes, 1-methyl-1H-pyrazole-3-carboxylic acid was introduced into the coordination with [Pd(μ-Cl)(Cl)(NHC)]2 and the corresponding mononuclear complexes (NHC)PdCl(1-methyl-1H-pyrazole-3-carboxylate) were obtained. The catalytic properties of the complexes in desulfitative arylation of azoles with arylsulfonyl hydrazides were initially investigated.
- Yang, Jin
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- Palladium-catalyzed direct C2-arylation of azoles with aromatic triazenes
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A highly efficient palladium-catalyzed arylation of azoles at the C2-position using 1-aryltriazenes as aryl reagents was developed. Azoles including oxazoles, thiazoles, imidazoles, 1,3,4-oxadiazoles, and oxazolines could react with 1-aryltriazenes smoothly to generate the corresponding products in good to excellent yields, and various substitution patterns were tolerated toward the reaction.
- Liu, Can,Wang, Zhiming,Wang, Lei,Li, Pinhua,Zhang, Yicheng
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p. 9209 - 9216
(2019/11/05)
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- Microwave assisted synthesis and potent antimicrobial activity of some novel 1,3-dialkyl-2-arylbenzimidazolium salts
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Background: Benzimidazolium salts include biologically active benzimidazole ring. Some benzimidazolium salts and their metal complexes, containing different groups, showed remarkable antibacterial, antifungal and antitumor effects. Most of these studies are generally related with the 2-unsubstituted derivatives of benzimidazolium salts which named as N-heterocyclic carbenes (NHCs). To enhance the efficacy of the benzimidazoles in the biological systems, it is very important to overcome the insolubility problem. For this reason and previously indicated structural importance of the benzimidazolium salts, 1,3-dialkyl halide salts of the 2-arylbenzimidazoles, are of focus in this work. To the best of our knowledge, this is the first report that describes the microwave assisted synthesis and antimicrobial activity of 2-arylsubstituted benzimidazolium salts. Methods: A series of novel 1,3-dialkyl-2-arylbenzimidazolium salts (8-28) were synthesized via the N-alkylation of 1-methyl-2-arylbenzimidazole derivatives (1-7) with alkyl halides under microwave conditions by using small amount of DMF. The results were also compared with conventional heating under reflux. Structures of the products were confirmed by using 1H-NMR, 13C-NMR, FTIR spectroscopic techniques. All of the synthesized compounds were screened for their in vitro antimicrobial activities using microbroth tube dilution and disc diffusion methods. Results: Considering the reactions repeated by classical heating, it was determined that the reaction times were decreased from 3-6 hours to 5-35 minutes under microwave. Additionally, yields have increased from 4-71 % to 64-96 % ranges. Considering the whole antimicrobial activity studies, MIC values of newly synthesized benzimidazolium salts 8-28 (1.95->1500 μg/ml) are remarkably smaller than parent benzimidazoles 1-7 (62.5->1500 μg/ml) on the studied microorganisms. Conclusion: The microwave method is advantageous regarding the usage of mild conditions and small amounts of solvent, easy purification and achieving high yields in short times. The antimicrobial activity studies demonstrate that newly synthesized salts (8-28) are effective mostly on grampositives and eukaryotic microorganisms. Compounds 16, 18, 19, 24, 25 and 27 were found to be the most effective inhibitors of growth in both gram-positive bacteria and eukaryotes. Thus, the synthesized compounds in this study may aid the treatment of fungal and bacterial diseases. The results of this study are of great significance in the areas of synthetic organic chemistry, microbiology, pharmaceutical chemistry and chemical catalysis.
- Eren, Bilge,Yilmaz, ?zge,?etin, Gül?in,Darcan, Cihan
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p. 621 - 633
(2018/06/06)
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- Nickel-Catalyzed Heteroarenes Cross Coupling via Tandem C-H/C-O Activation
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Inert aryl methyl ethers as coupling components via C-O activation have been established with a Ni catalyst for C-H activation of heteroarene. The key to simultaneous C-H/C-O bond activation is the use of sterically demanding o-tolylMgBr. The protocol is effective for a wide scope of substrates including naphthyl methyl ethers, anisoles, and a variety of other heteroarene derivatives. Detailed mechanistic studies indicated that the C-O cleavage is assisted via synergistic effect of nickel and Grignard reagent in this C-H/C-O reaction, which is supported by DFT calculation. At this stage, single-electron transfer can be ruled out as a main operative process for this tandem strategy.
- Wang, Ting-Hsuan,Ambre, Ram,Wang, Qing,Lee, Wei-Chih,Wang, Pen-Cheng,Liu, Yuhua,Zhao, Lili,Ong, Tiow-Gan
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p. 11368 - 11376
(2018/11/23)
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- Ring-expanded N-heterocyclic carbenes as ligands in iron-catalysed cross-coupling reactions of arylmagnesium reagents and aryl chlorides
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The structure-activity relationship of expanded-ring N-heterocyclic carbenes (NHCs) in the iron-catalysed Kumada aryl-aryl coupling reaction was explored. This was achieved by comparing the catalytic performance of Fe-NHC catalysts generated in situ containing NHCs that differ in steric bulk. In particular, the influences of ring sizes (5-8) and N-aryl substituents were explored in terms of spectroscopic and structural features, which affect their %Vbur values. The three best performing ligands were found on a diagonal of a 5 × 4 structural matrix revealing an optimal steric bulk and significant influences of subtle steric variations on the catalytic activities.
- Teng, Qiaoqiao,Wu, Wenqin,Duong, Hung A.,Huynh, Han Vinh
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supporting information
p. 6044 - 6047
(2018/06/18)
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- Catalytic Oxidative Coupling of Primary Amines under Air: A Flexible Route to Benzimidazole Derivatives
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Benzimidazoles are of fundamental importance in chemistry and biology, and the development of efficient, environmentally benign methods for their preparation remains a key challenge for organic chemists. In a biomimetic approach inspired by copper amine oxidases, we disclose herein the scope and factors influencing the success of the cooperative action of CuBr2 as electron-transfer mediator and a topaquinone-like substrate-selective catalyst in the oxidative cyclocondensation of primary amines with o-aminoanilines. This one-pot atom-economic multistep process, which works under green conditions with ambient air as the terminal oxidant, low loadings of catalyst, and equimolar amounts of commercially available amine substrates, is particularly suitable for the preparation of 1,2-disubstituted benzimidazoles. Furthermore, it allows the functionalization of nonactivated primary aliphatic amines, which are known to be challenging substrates for non-enzymatic catalytic aerobic systems.
- Nguyen, Khac Minh Huy,Largeron, Martine
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supporting information
p. 1025 - 1032
(2016/03/01)
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- Synthesis of 2-substituted benzimidazoles and benzothiazoles using Ag2CO3/Celite as an efficient solid catalyst
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An efficient and simple approach for the synthesis of 2-substituted benzimidazoles and benzothiazoles through a coupling of 1,2-phenylenediamines and 2-aminothiophenols with variety of aryl aldehydes in ethanol at 70 °C using Ag2CO3/Celite as solid catalyst is described. The procedure features short reaction time, excellent yields and simple workup.
- Soleimani, Ebrahim,Khodaei, Mohammad Mehdi,Yazdani, Hossein,Saei, Parisa,Zavar Reza, Javad
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p. 1281 - 1285
(2015/06/02)
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- Nanoparticle mediated organic synthesis (NAMO-synthesis): CuI-NP catalyzed ligand free amidation of aryl halides
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The first CuI-nanoparticle catalyzed ligand free synthesis of N-aryl amides from aryl halides and arylamides/cyclic amides has been developed. This methodology is further extended for the synthesis of nitrogen heterocycles such as benzimidazole, and quinazolinone via intermolecular amidation reaction followed by cyclization. TEM images of the CuI-NP catalyst showed spherical, well-dispersed particles which provide large surface area for reactivity and have good recyclability. This journal is
- Kumar, Atul,Bishnoi, Ajay Kumar
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p. 41631 - 41635
(2014/12/10)
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- Nanoparticle mediated organic synthesis (NAMO-synthesis): CuI-NP catalyzed ligand free amidation of aryl halides
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The first CuI-nanoparticle catalyzed ligand free synthesis of N-aryl amides from aryl halides and arylamides/cyclic amides has been developed. This methodology is further extended for the synthesis of nitrogen heterocycles such as benzimidazole, and quinazolinone via intermolecular amidation reaction followed by cyclization. TEM images of the CuI-NP catalyst showed spherical, well-dispersed particles which provide large surface area for reactivity and have good recyclability. This journal is
- Kumar, Atul,Bishnoi, Ajay Kumar
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p. 41631 - 41635
(2015/05/20)
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- Gold nanoparticles supported on titanium dioxide: An efficient catalyst for highly selective synthesis of benzoxazoles and benzimidazoles
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A highly efficient and selective reaction for the synthesis of 2-substituted benzoxazoles and benzimidazoles catalyzed by Au/TiO2 has been developed via two hydrogen-transfer processes. This reaction has a good tolerance to air and water, a wide substrate scope, and represents a new avenue for practical C-N and C-O bond formation. More importantly, no additional additives, oxidants and reductants are required for the reaction and the catalyst can be recovered and reused readily. This journal is the Partner Organisations 2014.
- Tang, Lin,Guo, Xuefeng,Yang, Yu,Zha, Zhenggen,Wang, Zhiyong
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supporting information
p. 6145 - 6148
(2014/06/09)
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- N -heterocyclic carbene-palladium(II)-1-methylimidazole complex-catalyzed direct C-H bond arylation of (Benz)imidazoles with aryl chlorides
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(Benz)imidazoles can be efficiently functionalized by (hetero)aryl chlorides via direct C-H bond arylation in the presence of a well-defined NHC-Pd(II)-Im complex. Under the optimal conditions, various activated, unactivated, and deactivated (hetero)aryl chlorides were successfully applied as the arylating reagents to achieve the 2-(hetero)aryl (benz)imidazoles in acceptable to high yields, giving a facile and alternative methodology for the direct C-H bond arylation of (benz)imidazoles.
- Gu, Zheng-Song,Chen, Wen-Xin,Shao, Li-Xiong
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p. 5806 - 5811
(2014/07/08)
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- Nano CuO-catalyzed C-H functionalization of 1,3-azoles with bromoarenes and bromoalkenes
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Copper oxide catalyzed direct C-H arylation and alkenylation of aromatic heterocycles using aryl and alkenyl bromides have been developed and have been applied to the C-H functionalization of a variety of 1,3-azoles like benzoxazole, benzothiazole, 1-methylbenzimidazole, and 1-methylimidazole, with moderate to excellent yields. The best performance has been achieved in the presence of PPh3 when average size of CuO nanoparticles is 6.5 nm. This catalyst can be recovered and reused without significant decrease in its catalytic activity.
- Zhang, Wu,Tian, Yujie,Zhao, Na,Wang, Yuanyuan,Li, Jia,Wang, Zhenghua
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p. 6120 - 6126
(2015/03/30)
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- Copper and iron-assisted palladium-catalyzed direct arylation of azoles with arylboronic acids under ligand and base-free conditions
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The direct arylation of azoles with arylboronic acids is effectively promoted by PdCl2 in the presence of copper and iron salts under ligand and base-free conditions. This reaction can be applied to heterocycles such as benzothiazole, benzoxazole, 1-methylbenzimidazole and 4,5-dimethylthiazole with moderate to good yields.
- Wu, Xiang-Mei,Shen, Qiu-Xian
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p. 668 - 673
(2013/12/04)
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- Formation of C=N bonds by the release of H2: A new strategy for synthesis of imines and benzazoles
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A new strategy for synthesis of imines using the approach of release of H2 has been developed. This oxidant- and acceptor-free Pd/C catalysis protocol is further applied to synthesis of benzoxazoles, benzimidazoles, and benzothiazoles through a one-pot cascade reaction with notably high yields. The Royal Society of Chemistry 2013.
- Jin, Xukang,Liu, Yuxiao,Lu, Qiongqiong,Yang, Dejun,Sun, Jiangkai,Qin, Shuangshuang,Zhang, Jingwu,Shen, Jiaxuan,Chu, Changhu,Liu, Renhua
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supporting information
p. 3776 - 3780
(2014/03/21)
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- Discovery of a full-color-tunable fluorescent core framework through direct C-H (hetero)arylation of N-heterocycles
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All the colors of the rainbow! A full coverage of emission wavelengths in the visible region (405-616 nm) with large Stokes shifts in C3-Indo-Fluor may be straightforwardly and succinctly achieved by the palladium-catalyzed direct C-H arylation of indolizines at the C3 position of the pyrrole ring (see figure). The fluorophores have successfully marked A375 cells. Copyright
- Liu, Bo,Wang, Zhi,Wu, Ningjie,Li, Mingliang,You, Jingsong,Lan, Jingbo
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supporting information; experimental part
p. 1599 - 1603
(2012/03/10)
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- Ligand-free CuO nanospindle catalyzed arylation of heterocycle C-H bonds
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CuO nanospindles have been developed to efficiently catalyze the direct arylation of heterocycle C-H bonds with moderate to excellent yields. This reaction can be applied to heterocycles such as benzoxazole, benzothiazole, and 1-methylbenzimidazole in the presence of a more environmentally friendly inorganic base like K2CO3 under ligand-free catalytic conditions. In addition, the catalyst can be recycled and reused without any significant decrease in catalytic activity.
- Zhang, Wu,Zeng, Qinglong,Zhang, Xinming,Tian, Yujie,Yue, Yun,Guo, Yujun,Wang, Zhenghua
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experimental part
p. 4741 - 4745
(2011/07/08)
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- Aerobic oxidative coupling of amines by carbon nitride photocatalysis with visible light
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Coupling on sunshine: A simple and efficient synthesis of benzoxazoles, benzimidazoles, and benzothiazoles is realized through a one-pot preparation driven by a photocatalytic cascade reaction. Carbon nitride and visible light are employed to achieve this metal-free aerobic oxidation of amines to imines (see scheme; mpg-C3N4=mesoporous graphite carbon nitride). Copyright
- Su, Fangzheng,Mathew, Smitha C.,Moehlmann, Lennart,Antonietti, Markus,Wang, Xinchen,Blechert, Siegfried
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supporting information; scheme or table
p. 657 - 660
(2011/03/19)
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- Palladium-catalyzed desulfitative C-H arylation of heteroarenes with sodium sulfinates
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Desulfitative C-H arylation: Palladium-catalyzed desulfitative C-H arylation of heteroarenes with sodium sulfinates has been disclosed to construct aryl-heteroaryl bonds without the need for any extra ligands (see scheme). Copyright
- Liu, Bo,Guo, Qiang,Cheng, Yangyang,Lan, Jingbo,You, Jingsong
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supporting information; experimental part
p. 13415 - 13419
(2012/01/03)
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- An efficient arylation of benzoazoles with aryl bromides by a practical palladium-copper cocatalytic system
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A practical, efficient Pd(OAc)2/Cu(II)/PPh3 cocatalytic system has been developed. With only 1 mol% Pd(OAc)2, 20 mol% copper(II) salt, and 0.5 equiv of inexpensive PPh3 as ligand, the direct arylation of benzoazoles with aryl bromides could be performed smoothly in mild condition, affording the desired arylated benzoazoles in good yields (75-93%).
- Yan, Xue-Ming,Mao, Xue-Rong,Huang, Zhi-Zhen
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experimental part
p. 1371 - 1376
(2011/06/27)
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- A palladium/copper bimetallic catalytic system: Dramatic improvement for Suzuki-Miyaura-type direct C-H arylation of azoles with arylboronic acids
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Bimetallic catalytic system: Palladium/copper bimetallic-catalyzed Suzuki-Miyaura-type coupling has been disclosed for direct C-H arylation of azoles, instead of azole halides or pseudohalides, with arylboronic acids (see scheme).
- Liu, Bo,Qin, Xurong,Li, Kaizhi,Li, Xiyu,Guo, Qiang,Lan, Jingbo,You, Jingsong
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supporting information; experimental part
p. 11836 - 11839
(2011/01/12)
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- A Keggin heteropoly acid as an efficient catalyst for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles
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The Keggin heteropoly acid, silicotungstic acid, H4SiW12O40, has been demonstrated to be highly efficient for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles from N-methyl-1,2-phenylenediamine and (hetero)aryl aldehydes in ethyl acetate at room temperature. The catalyst works equally well for N-phenyl-1,2-phenylenediamine.
- Chakrabarty, Manas,Mukherji, Ajanta,Mukherjee, Ratna,Arima, Shiho,Harigaya, Yoshihiro
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p. 5239 - 5242
(2008/02/08)
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- Microwave-assisted one step high-throughput synthesis of benzimidazoles
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One-pot synthesis of benzimidazoles from diamines and carboxylic acids was developed under microwave irradiation condition, which provided a practical and efficient method for high-throughput synthesis of this important class of heterocyclic compounds.
- Lin, Shou-Yuan,Isome, Yuko,Stewart, Ethan,Liu, Ji-Feng,Yohannes, Daniel,Yu, Libing
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p. 2883 - 2886
(2007/10/03)
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- Smart cleavage reactions: The synthesis of benzimidazoles and benzothiazoles from polymer-bound esters
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The preparation of an array of benzimidazoles and benzothiazoles from polymer-bound esters is described. Polymer-bound esters were treated with 2-aminothiophenols or 1,2-phenylenediamines in the presence of a Lewis acid to afford the corresponding benzothiazole or benzimidazole cleavage products. The reaction of 2-aminophenols with the polymer-bound esters failed to give the desired benzoxazole products using this procedure.
- Matsushita, Hana,Lee, Sang-Hyeup,Joung, Meyoungju,Clapham, Bruce,Janda, Kim D.
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p. 313 - 316
(2007/10/03)
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- SYNTHESIS OF 2-ARYL-BENZIMIDAZOLES VIA CYCLIC N-DIAZONIUM IONS
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Condensation of 2-azido-aniline with aromatic aldehydes and protonation with tetrafluoroboric acid lead to phenylogous azidoiminium salts.Subsequent cyclisation to cyclic N-diazonium ions and N2-elimination give rise to the formation of 2-aryl-benzimidazo
- Kreher, Richard,Bergmann, Udo
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p. 1725 - 1728
(2007/10/02)
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