- Transition-Metal-Free Transfer Hydrogenative Cascade Reaction of Nitroarenes with Amines/Alcohols: Redox-Economical Access to Benzimidazoles
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This report describes an efficient transition-metal-free process toward the transfer hydrogenative cascade reaction between nitroarenes and amines or alcohols. The developed redox-economical approach was realized using a combination of KOtBu and Et3SiH as reagents, which allows the synthesis of benzimidazole derivatives via σ-bond metathesis. The reaction conditions hold well over a wide range of substrates embedded with diverse functional groups to deliver the desired products in good to excellent yields. The mechanistic proposal has been depicted on the basis of a series of control experiments, mass spectroscopic evidence which is well supported by density functional theory (DFT) calculations with a feasible energy profile.
- Gujjarappa, Raghuram,Kabi, Arup K.,Malakar, Chandi C.,Musib, Dulal,Roy, Anupam,Sahoo, Abhishek,Singh, Virender,Vodnala, Nagaraju
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p. 14597 - 14607
(2021/11/12)
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- Synthesis, bioevaluation and docking studies of some 2-phenyl-1H-benzimidazole derivatives as anthelminthic agents against the nematode Teladorsagia circumcincta
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Gastrointestinal nematode infections are the main diseases in herds of small ruminants. Resistance to the main established drugs has become a worldwide problem. The purpose of this study is to obtain and evaluate the in vitro ovicidal and larvicidal activity of some 2-phenylbenzimidazole derivatives on susceptible and resistant strains of Teladorsagia circumcincta. Compounds were prepared by known procedures from substituted o-phenylenediamines and arylaldehydes or intermediate sodium 1-hydroxyphenylmethanesulfonate derivatives. Egg Hatch Test (EHT), Larval Mortality Test (LMT) and Larval Migration Inhibition Test (LMIT) were used in the initial screening of compounds at 50 μM concentration, and EC50 values were determined for the most potent compounds. Cytotoxicity evaluation of compounds was conducted on human Caco-2 and HepG2 cell lines to calculate their Selectivity Indexes (SI). At 50 μM concentration, nine out of twenty-four compounds displayed more than 98% ovicidal activity on a susceptible strain, and four of them showed more than 86% on one resistant strain. The most potent ovicidal benzimidazole (BZ) 3 showed EC50 = 6.30 μM, for the susceptible strain, while BZ 2 showed the lowest EC50 value of 14.5 μM for the resistant strain. Docking studies of most potent compounds in a modelled Teladorsagia tubulin indicated an inverted orientation for BZ 1 in the colchicine binding site, probably due to its fair interaction with glutamic acid at codon 198, which could justify its inactivity against the resistant strain of T. circumcincta.
- Escala, Nerea,Valderas-García, Elora,Bardón, María álvarez,Gómez de Agüero, Verónica Castilla,Escarcena, Ricardo,López-Pérez, José Luis,Rojo-Vázquez, Francisco A.,San Feliciano, Arturo,Bala?a-Fouce, Rafael,Martínez-Valladares, María,Olmo, Esther del
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- Graphene oxide-catalyzed CSp3–H activation of methylarenes in aqueous medium: A unified metal-free access to amides and benzimidazoles
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Graphene oxide (GO)-catalyzed selective synthesis of amides via CSp3–H activation of methylarenes and consequent C–N bond formation with anilines under aqueous medium has been described. Oxygen functionality allied with GO surface played a dual role both as acid catalyst and oxidizing agent to some extent. However, GO has a copious effect on the reaction, shown by a high TOF value with TBHP as co-oxidant. The decisive role of carboxylic acid functional groups on GO nanosheets in this metal-free strategy has been confirmed and was monitored by various analytic techniques viz. Fourier transform-infrared, UV–Vis, Raman and XPS. A plausible mechanism was proposed by control experiments and by the isolation of the intermediate. Over-oxidation of methylarenes was not detected, and high recyclability of the carbocatalyst with its heterogeneous behavior facilitated the isolation and purification of the desired products. We have further explored the utility of this process for the chemoselective synthesis of benzimidazoles.
- Dandia, Anshu,Mahawar, Dinesh Kumar,Sharma, Ruchi,Badgoti, Ranveer Singh,Rathore, Kuldeep S.,Parewa, Vijay
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- Synergic effect of copper-based metal-organic frameworks for highly efficient C-H activation of amidines
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A Cu-MOF-catalyzed C-H functionalization of substituted amidines was developed for the facile and efficient synthesis of benzimidazoles. More importantly, this transformation is compatible with various substrates derived from aryl nitriles without ortho substituents. Under reaction conditions devoid of O2 atmosphere or specific groups, 537-MOF has been revealed as a key parameter for expanding the reaction scope and increasing the yield up to 96%. Importantly, this strategy also provides numerous opportunities for further utilization of MOFs as catalysts for challenging organic reactions.
- Xu, Fen,Kang, Wei-Fen,Wang, Xiao-Ning,Kou, Hao-Dong,Jin, Zhen,Liu, Chun-Sen
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p. 51658 - 51662
(2017/11/16)
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- Efficient one-pot synthesis of 2-substituted benzimidazoles from triacyloxyborane intermediates
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An efficient one-pot synthesis of 2-substituted benzim?idazoles via triacyloxyborane intermediates is reported. The mild protocol is efficient and tolerant of acid-labile functional groups. Georg Thieme Verlag Stuttgart - New York.
- Cui, Wenge,Kargbo, Robert B.,Sajjadi-Hashemi, Zohreh,Ahmed, Feryan,Gauuan, Jolicia F.
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experimental part
p. 247 - 250
(2012/02/15)
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