- 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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- A simple and efficient mechanochemical route for the synthesis of 2-aryl benzothiazoles and substituted benzimidazoles
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An efficient and versatile mechanochemical route to 2-aryl benzothiazoles and both 2-substituted and 1,2-disubstituted benzimidazole derivatives has been developed via a simple mortar-pestle grinding method. The mechanochemical agitation was found to be sufficient for smooth condensation between a variety of aromatic aldehydes and o-aminothiophenol/o-phenylenediamine followed by cyclization leading to the formation of the corresponding 1,3-benzazoles. The salient features of this new protocol are catalyst-free reaction, cleaner reaction profiles, absence of a work-up step, high yields, and short reaction times.
- Banerjee, Mainak,Chatterjee, Amrita,Kumar, Vikash,Bhutia, Zigmee T.,Khandare, Dipratn G.,Majik, Mahesh S.,Roy, Biswajit Gopal
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p. 39606 - 39611
(2014/11/07)
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- γ-Maghemite-silica nanocomposite: A green catalyst for diverse aromatic N-heterocycles
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γ-Maghemite-silica nanocomposite has been applied as a green catalyst to synthesize variety of aromatic N-heterocycles under solvent free conditions. Characterization was done by modern analytical tools (UV, IR, AAS, DSC, EDXRF, powdered XRD, EPR, Mo?ssbauer and TEM). Mild reaction conditions and recyclability have made the present protocol both environmentally and economically viable.
- Ghosh, Pranab,Mandal, Amitava,Subba, Raju
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p. 146 - 152
(2013/09/02)
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- Simple and mild protocol for synthesis of 1,2- Disubstitued benzimidazoles using SBA-15-supported poly(4-styrenesulfonyl-(Perfluorobutylsulfonyl)Imide) catalyst
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A simple method for the synthesis of several 1,2-disubstituted benzimidazoles catalyzed by strongly acidic SBA-15-supported poly(4-styrenesulfonyl-(perfluorobutylsulfonyl) imide) is described. The protocol furnished the products in moderate yield and good selectivity in the condensation of o-phenylenediamine with structurally diverse aldehydes under mild conditions. Taylor & Francis Group, LLC.
- Ma, Zhong-Hua,Lin, Sheng,Nie, Jin
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experimental part
p. 506 - 515
(2011/12/04)
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- Acetic acid-promoted condensation of o-phenylenediamine with aldehydes into 2-aryl-1-(arylmethyl)-1H-benzimidazoles under microwave irradiation
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An efficient and simple procedure was developed for the green synthesis of various 2-aryl-1-(arylmethyl)-1 H-benzimidazoles in high yields by acetic acid-promoted condensation of o-phenylenediamine with aldehydes in air under microwave irradiation and transition metal catalyst-free conditions. 2010 Copyright (CC) SCS.
- Azarifar, Davood,Pirhayati, Mojgan,Maleki, Behrooz,Sanginabadi, Mehrangiz,Yami, Razieh Nejat
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experimental part
p. 1181 - 1189
(2010/11/24)
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- The convenient synthesis of benzimidazole derivatives catalyzed by I 2 in aqueous media
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In the presence of catalytic amount of iodine, in THF-H2O, the condensation of aldehydes with 1,2-phenylenediamine gave the benzimidazole derivatives under mild conditions in good yields. The method can be used for the synthesis of 2-substituted benzimidazoles or 1,2-disubstituted benzimidazoles.
- Sun, Peipei,Hu, Zhixin
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p. 773 - 775
(2007/10/03)
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- Application of sulfamic acid as an eco-friendly catalyst in an expedient synthesis of benzimidazoles
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Sulfamic acid, an eco-friendly and zwitterionic solid, proved to be a very efficient catalyst for the reaction of ortho-phenylenediamine with aryl aldehydes in ethanol at room temperature to furnish both 1-arylmethyl-2-aryl- and 2-arylbenzimidazoles in very good to excellent overall yields.
- Chakrabarty, Manas,Karmakar, Sulakshana,Mukherji, Ajanta,Arima, Shiho,Harigaya, Yoshihiro
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p. 967 - 974
(2007/10/03)
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