- Sodium dichloroiodate promoted C-C bond cleavage: An efficient synthesis of 1,3-Benzazoles via condensation of o -amino/mercaptan/hydroxyanilines with β -diketones
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An efficient aqueous sodium dichloroiodate (NaICl 2) mediated protocol is developed for the synthesis of benzofused azoles by the cyclization of 2-amino anilines/thiophenols/phenols with β-diketone compounds. The reactions gave moderate to good yield of the corresponding 2-substituted benzimidazoles/benzothiazoles/benzoxazoles under mild conditions. This tandem process involved a C-C bond cleavage and C-N bond formation. Graphical Abstract?: SYNOPSIS A facile and single protocol for the synthesis of three versatile 1,3-benzazoles viz 2-substituted 1H-benzimidazoles, benzoxazoles and benzothiazoles from readily available starting materials, 1,3-diketones and corresponding o-amino anilines/thiophenols/phenols, by aqueous sodium dichloroiodate (NaICl 2) mediated C—C bond cleavage has been developed. The reaction provides a rapid access to these 1, 3-benzazoles in good yields, thus speeding up the drug discovery process.[Figure not available: see fulltext.].
- Bhagat, Saket B,Ghodse, Shrikant M,Telvekar, Vikas N
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- Cu-Pd/γ-Al2O3 catalyzed the coupling of multi-step reactions: Direct synthesis of benzimidazole derivatives
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The coupling of multi-step reactions catalyzed by a heterogeneous catalyst is an important path to accomplish some unconventional chemical transformations. Since the starting materials generated from previous steps were adsorbed on the catalyst, the activation energy of following steps was largely decreased, and thus the reaction conditions were more mild and environmental friendly. Catalyzed by a multifunctional Cu-Pd/γ-Al2O3 catalyst, the transfer hydrogenation and successive cyclization coupling reaction from o-nitroaniline and alcohol to afford benzimidazole derivatives in high yield was realized. The catalyst could be reused several times without loss of activity. The synergies of reforming hydrogenation of Cu-Pd bimetal and support acidity of γ-Al2O3 were responsible for this catalytic transformation.
- Feng, Feng,Ye, Jia,Cheng, Zheng,Xu, Xiaoliang,Zhang, Qunfeng,Ma, Lei,Lu, Chunshan,Li, Xiaonian
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p. 72750 - 72755
(2016/08/09)
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- Method for preparing benzimidazole compound through supported bimetallic catalyst at room temperature
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The invention belongs to the technical field of photochemistry organic synthesis, and particularly relates to a method for preparing a benzimidazole compound through a supported bimetallic catalyst at room temperature .The preparation method of the benzimidazole compound comprises the steps that o-phenylenediamine and reactant alcohol are used as initial reactants, a photocatalyst is used as a supported bimetallic nanoparticles, in an organic solvent and under the stirring condition and irradiation of ultraviolet light or visible light or sunlight, the o-phenylenediamine and the reactant alcohol are directly subjected to photocatalysis through light source irradiation to be converted into benzimidazole and a derivative thereof .According to the method, reaction conditions are mild, high-temperature reaction conditions are not needed, the reaction speed at room temperature is high, and the selectivity of the target product benzimidazole is 95% or above .
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Paragraph 0090
(2017/07/21)
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- Convenient synthesis of benzothiazoles and benzimidazoles through bronsted acid catalyzed cyclization of 2-amino thiophenols/anilines with β-diketones
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Bronsted acid catalyzed cyclization reactions of 2-amino thiophenols/anilines with β-diketones under oxidant-, metal-, and radiation-free conditions are described. Various 2-substituted benzothiazoles/benzimidazoles are obtained in satisfactory to excellent yields. Different groups such as methyl, chloro, nitro, and methoxy linked on benzene rings were tolerated under the optimized reaction conditions.
- Mayo, Muhammad Shareef,Yu, Xiaoqiang,Zhou, Xiaoyu,Feng, Xiujuan,Yamamoto, Yoshinori,Bao, Ming
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supporting information
p. 764 - 767
(2014/03/21)
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- A rapid access to novel and known benzimidazole derivatives using silica chloride as a reusable catalyst
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A new application of silica chloride as an easily available and reusable solid acid catalyst for the synthesis of benzimidazole and its derivatives through the condensation of o-phenylenediamines and orthoesters under thermal and solvent-free conditions is described. This novel and eco-friendly method is very cheap and has many advantages including excellent yields, short reaction time, and simple work-up procedure. Copyright
- Karami, Bahador,Ghashghaee, Vahideh,Khodabakhshi, Saeed
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experimental part
p. 959 - 964
(2012/05/31)
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- Tungstate sulfuric acid: Preparation, characterization, and application in catalytic synthesis of novel benzimidazoles
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Tungstate sulfuric acid (TSA) was prepared, characterized, and applied for direct synthesis of novel and known benzimidazoles through a condensation reaction of o-phenylenediamines with orthoesters under solvent-free conditions. TSA was characterized by powdered X-ray diffraction (XRD), X-ray fluorescence (XRF), and FTIR spectroscopy. This novel and eco-friendly method is very cheap and has many advantages such as excellent yields, recyclable and eco-friendly catalyst, and simple work-up procedure.
- Karami, Bahador,Khodabakhshi, Saeed,Haghighijou, Zahra
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p. 684 - 690
(2013/07/26)
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- 1,3-Dibromo-5,5-dimethylhydantoin as an efficient homogeneous catalyst for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines
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A simple and highly efficient method for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines is described. Condensation of orthoesters with o-substituted anilines or 2-amino-3-hydroxypyridine was performed in the presence of catalytic amounts of commercially available, inexpensive, and moisture-stable 1,3-dibromo-5,5-dimethylhydantoin under solvent-free conditions. The corresponding heterocycles were obtained in good to excellent yields. The main advantages of the present procedure are mild reaction conditions, short reaction times, high yields of products, easy work-up, and absence of solvent. Graphical abstract: [Figure not available: see fulltext.]
- Hojati, Seyedeh Fatemeh,Maleki, Behrooz,Beykzadeh, Zahra
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experimental part
p. 87 - 91
(2011/09/19)
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- Ag-TiO2/clay composite photocatalyst for the oxidation-cyclization of 1,2-diamine compounds with propylene glycol or alcohols
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Silver-loaded TiO2 (Ag-TiO2) and acidic clay (K10 montmorillonite) composite photocatalyst has been successfully applied for the light-induced conversion of o-phenylenediamine (OPD) and its derivatives to substituted benzimidazoles with various alcohols in acetonitrile using UV-A and solar light. The influence of the various photocatalysts, solvents, and substituents on the yield and selectivity of the products has been investigated. The mechanism of photocatalysis is proposed. Loading silver on TiO2 enhances product yield and selectivity both in UV and solar light. In the presence of primary alcohols, 2-aminothiophenol forms only disulfide and hence Ag-TiO2/ clay can be used as a green catalyst for the synthesis of disulfides.
- Selvam, Kaliyamoorthy,Annadhasan, Mari,Velmurugan, Rengasamy,Swaminathan, Meenakshisundaram
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experimental part
p. 831 - 837
(2010/09/06)
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- Water-mediated synthesis of 2-substituted benzimidazoles by boric acid and glycerol
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A very simple, mild, and highly efficient green catalyst has been developed for the synthesis of 2-substituted benzimidazoles by treatment of substituted ortho-phenylenediamines and aldehydes in water at 80C in the presence of boric acid (5 mol-%) and glycerol (0.05 mL). This methodology has been standardized on 55 substrates, and nine new compounds have been synthesized.
- Mukhopadhyay, Chhanda,Tapaswi, Pradip Kumar,Butcher, Ray J.
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experimental part
p. 140 - 144
(2009/08/15)
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- A highly effective sulfamic acid/methanol catalytic system for the synthesis of benzimidazole derivatives at room temperature
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Sulfamic acid/methanol was found to be an efficient catalytic system for the synthesis of benzimidazole compounds through the condensation of o-phenylenediamine with orthoester in high yields at room temperature.
- Zhang, Zhan-Hui,Li, Tong-Shuang,Li, Jian-Jiong
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- Synthesis of 2-substituted benzimidazoles by iodine-mediated condensation of orthoesters with 1,2-phenylenediamines
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(Chemical Equation Presented) Iodine was found to be an efficient catalyst for the synthesis of 2-substituted benzimidazoles by the condensation of orthoesters and 1,2-phenylenediamines in good to excellent yields under mild reaction conditions.
- Zhang, Zhan-Hui,Li, Jian-Jiong,Gao, Yuan-Zhe,Liu, Yu-Heng
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p. 1509 - 1512
(2008/09/18)
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- Mild and efficient synthesis of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines catalyzed by Bi(III) salts under solvent-free conditions
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A series of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines was efficiently synthesized from the reactions of o-aminophenols, o-aminothiophenol, o-phenylenediamines, and 2-amino-3- hydroxypyridine with orthoesters in the presence of catalytic amounts of Bi(III) salts, such as Bi(TFA)3, Bi(OTf)3, and BiOClO4 ? xH2O under solvent-free conditions. The remarkable features of this new protocol are high conversion, very short reaction times, cleaner reaction profiles under solvent-free conditions, straightforward procedure, and use of relatively non-toxic catalysts. Springer-Verlag 2007.
- Mohammadpoor-Baltork, Iraj,Khosropour, Ahmad R.,Hojati, Seyedeh F.
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p. 663 - 667
(2008/02/07)
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- An efficient procedure for the synthesis of benzimidazole derivatives using Yb(OTf)3 as catalyst under solvent-free conditions
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o-Diaminobenzene derivatives react smoothly with ortho-esters in the presence of 0.5 mol% of Yb(OTf)3 under solvent-free conditions to afford the corresponding benzimidazole derivatives in good to excellent yields. In addition, Yb(OTf)3 can be easily recovered almost quantitatively from the aqueous layer after the reaction was completed, and it could be reused with no loss of activity.
- Wang, Limin,Sheng, Jia,Tian, He,Qian, Changtao
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p. 4265 - 4272
(2007/10/03)
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- Ammonium sulphate-magnesium selective reduction of N-2-nitrophenylimidates: Synthesis of 2-substituted benzimidazoles
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Various N-2-nitrophenylimidates were selectively reduced by (NH4)2SO4-Mg to the non-isolated N-2-aminophenylimidates which cyclise to the corresponding 2-substituted benzimidazoles.
- Harizi, Abdallah,Zantour, Hedi
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p. 387 - 392
(2007/10/03)
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