- Iron(III) Chloride Mediated para-Selective C-H Functionalization: Access to C5-Chloro and C5,C7-Dichloro/Dianisyl Substituted 2-Arylbenzoxazoles
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Iron(III) chloride mediated para-selective C?H chlorination and subsequent annulation of 2-amidophenol to synthesize C5- and C5, C7-chlorinated benzoxazoles was developed. Further, the oxidative cross-dehydrogenative coupling of amidophenol with anisole b
- Sahoo, Kanchanbala,Panda, Niranjan
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p. 1023 - 1030
(2022/02/03)
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- Stable Pd(0) Complexes with Ferrocene Bisphosphanes Bearing Phosphatrioxaadamantyl Substituents Efficiently Catalyze Selective C-H Arylation of Benzoxazoles by Aryl Chlorides
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Versatile applications and unique performance of 1,1’-bis(diphenylphosphanyl)ferrocene (dppf) in coordination chemistry and catalysis prompted the search for its analogs. This contribution describes the synthesis of the first donor-unsymmetric dppf congeners bearing bulky and rigid 1,3,5,7-tetramethyl-2,4,6-trioxa-8-phosphaadamantyl (CgP) donor groups, viz. Ph2PfcPCg (1) and Ph2PfcCH2PCg (2; fc=ferrocene-1,1’-diyl). Bis-phosphanes 1 and 2 were converted into air-stable Pd(0) complexes, [Pd(ma)(L^L)] (L^L=1 and 2; ma=maleic anhydride). Together with [Pd(ma)(dppf)], these complexes were applied as catalysts in Pd-catalyzed C?H arylation of benzoxazoles with aryl chlorides in n-butanol as an environmentally benign solvent. Among all catalysts tested in this study, complex [Pd(ma)(2)] performed the best, providing a high-yield and selective synthesis of 2-arylbenzoxazoles from a range of the generally less reactive chloroarenes at low catalyst loading (typically 1 mol.%). Under similar conditions, the structurally related heterocycles (e. g., 1-methylbenzimidazole and benzothiazole) did not react.
- Horky, Filip,Císa?ová, Ivana,?těpni?ka, Petr
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p. 4848 - 4856
(2021/10/12)
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- Straightforward synthesis of benzoxazoles and benzothiazoles via photocatalytic radical cyclization of 2-substituted anilines with aldehydes
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Eosin Y-catalyzed one-pot coupling and cyclization of o-substituted anilines with aldehydes to form benzoxazoles and benzothiazoles under mild condition has been developed. The reaction scope was broadly tolerant of various 2-substituted anilines and aldehydes. The desired products were obtained in high yields with the use of eosin Y as a photocatalyst under a substantial refinement of reaction conditions in comparison with previous literature. Based on the experimental results observed, a plausible mechanism involving a radical process has been proposed.
- Le, Hao Anh Nguyen,Nguyen, Long Hoang,Nguyen, Quynh Nhu Ba,Nguyen, Hai Truong,Nguyen, Khang Quoc,Tran, Phuong Hoang
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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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- Phosphonium acidic ionic liquid: An efficient and recyclable homogeneous catalyst for the synthesis of 2-Arylbenzoxazoles, 2-Arylbenzimidazoles, and 2-Arylbenzothiazoles
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A highly efficient and green strategy for the synthesis of 2-Arylbenzoxazoles, 2-Arylbenzimidazoles, and 2-Arylbenzothiazoles catalyzed by phosphonium acidic ionic liquid has been developed via the condensation of o-Aminophenol, o-phenylenediamines, and o-Aminothiophenol, respectively, with aldehydes. The reaction has a good yield, the broad substrate scope, and mild condition. Triphenyl(butyl-3-sulphonyl)phosphonium toluenesulfonate catalyst was easily obtained from cheap and available starting materials through a one-pot synthesis. Its structure was identified by 1H NMR, 13C NMR, 31P NMR, and FT-IR techniques. Other properties including thermal stability and acidity were determined by TGA and Hammett acidity function method. Interestingly, the catalyst can maintain its constantly outstanding performance till the fourth recovery.
- Nguyen, Quang The,Thi Hang, Anh-Hung,Ho Nguyen, Thuy-Linh,Nguyen Chau, Duy-Khiem,Tran, Phuong Hoang
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p. 11834 - 11842
(2018/04/05)
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- Deep eutectic solvent-catalyzed arylation of benzoxazoles with aromatic aldehydes
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A novel and efficient methodology for the arylation of benzoxazoles with aromatic aldehydes catalyzed by deep eutectic solvent has been developed. The reaction smoothly proceeded with a wide range of substrates to give the desired products in high yields within short reaction time. Deep eutectic solvents are easily recovered and reused without significant loss of catalytic activity.
- Tran, Phuong Hoang,Thi Hang, Anh-Hung
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p. 11127 - 11133
(2018/03/26)
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- A new superacid hafnium-based metal-organic framework as a highly active heterogeneous catalyst for the synthesis of benzoxazoles under solvent-free conditions
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A new crystalline porous superacid material was prepared by sulfation of a Hf-MOF constructed from a 6-connected Hf node and 1,3,5-benzenetricarboxylate. The new superacid MOF with the presence of sulfate groups coordinated to a Hf-oxo cluster as superacid sites was found to be an effective heterogeneous catalyst for solvent-free heterocyclization for benzoxazole synthesis.
- Nguyen, Linh H.T.,Nguyen, The T.,Nguyen, Ha L.,Doan, Tan L.H.,Tran, Phuong Hoang
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p. 4346 - 4350
(2017/10/13)
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- p-Toluenesulfonic acid-catalyzed metal-free formal [4?+?1] heteroannulation via N[sbnd]H/O[sbnd]H/S[sbnd]H functionalization: One-pot access to 2-aryl/hetaryl/alkyl benzazole derivatives
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A concise and direct one-pot [4?+?1] synthetic strategy for the construction of 2-substituted benzazoles such as benzoxazoles and benzothiazoles has been disclosed in high yields (80–98%) by cascade coupling reaction of 2-amino(thio)phenols with β-oxodithioesters. The current approach enables N[sbnd]H/O[sbnd]H/S[sbnd]H functionalization in one-pot under solventless condition leading to diverse benzazoles without use of any external metal. A wide range of 2-amino(thio)phenols and β-oxodithioesters are compatible toward this transformation with excellent functional group tolerance. Furthermore, we preempt the wider implications of this novel strategy by demonstrating its compatibility toward versatile diversification of DNA Topoisomerase-II inhibitors.
- Srivastava, Abhijeet,Shukla, Gaurav,Singh, Maya Shankar
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p. 879 - 887
(2017/01/25)
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- Copper-catalyzed synthesis of benzoxazoles: Via tandem cyclization of 2-halophenols with amidines
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This work reports a simple, efficient and alternative synthetic route for the preparation of benzoxazoles via tandem cyclization of 2-halophenols with amidines. The developed methodology is free from ligands and uses inexpensive and easily available CuCl as a catalyst. This protocol avoids the use of any oxidant or inorganic acids. Various benzoxazole derivatives were synthesized in good to excellent yields. To the best of our knowledge, this is the first time that the synthesis of benzoxazoles from 2-halophenols with both aromatic and aliphatic amidines is reported. Owing to the simplicity of this protocol, the preparation of benzoxazoles could be achieved at a gram scale level.
- Tiwari, Abhishek R.,Bhanage, Bhalchandra M.
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p. 7920 - 7926
(2016/08/30)
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- An iron and copper system catalyzed C-H arylation of azoles with arylboronic acids
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An efficient, environmentally friendly, and economical new method for arylation reactions of azoles with arylboronic acids via copper-iron-catalyzed C-H and C-B bond activation has been developed. The protocol tolerates a series of functional groups, such as methoxy, nitro, cyano, chloro, and trifluoromethyl groups.
- Hu, Wei-Ye,Wang, Pei-Pei,Zhang, Song-Lin
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supporting information
p. 42 - 48
(2015/02/02)
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- Construction of Benzimidazoles and Benzoxazoles through the Molybdenum-Mediated Carbonylation of Aryl Halides
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The facile and efficient one-pot construction of benzimidazoles and benzoxazoles through the Mo(CO)6-mediated carbonylation of aryl halides was examined. In the process, Mo(CO)6 acted as a convenient and safe solid source of carbon monoxide. A wide range of substrates were tolerated to provide the corresponding products in fair to good yields without the need of gaseous CO or palladium catalysts. The facile and efficient one-pot construction of benzimidazoles and benzoxazoles is described. The reaction proceeds through Mo(CO)6-mediated carbonylation of aryl halides, in which Mo(CO)6 acts as a convenient and safe solid source of carbon monoxide.
- Kebede, Eshetu,Tadikonda, Ramu,Nakka, Mangarao,Inkollu, Bhargavi,Vidavalur, Siddaiah
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supporting information
p. 5929 - 5933
(2015/09/22)
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- Base-promoted formal arylation of benzo[d]oxazoles with acyl chloride
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A base-promoted formal arylation of benzo[d]oxazoles with acyl chloride was achieved in moderate to good yields. This reaction was triggered by the N-acylation of oxazole to form an iminium intermediate. Then, the addition of H2O to the iminium formed the hemiacetal intermediate. After the sequential ring-opening, extrusion of CO, the ring closure, the dehydration delivered the formal arylation product. In comparison with the transition-metal-catalyzed methodology, it represents an alternative arylation method leading to 2-arylbenzooxazole.
- Wang, Lei,Ren, Xinyi,Yu, Jintao,Jiang, Yan,Cheng, Jiang
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p. 12076 - 12081
(2014/01/06)
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- Iodine-mediated arylation of benzoxazoles with aldehydes
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A simple and efficient methodology for the arylation of benzoxazoles with aldehydes using iodine as the mediator has been developed. The reaction proceeded smoothly with a range of substrates to give the corresponding arylated products in moderate to good yields.
- Teo, Yew Chin,Riduan, Siti Nurhanna,Zhang, Yugen
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supporting information
p. 2365 - 2368
(2013/09/12)
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- Direct arylation of benzoxazole C-H bonds with iodobenzene diacetates
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A Pd (OAc)2-catalyzed direct arylation of benzoxazole C-H bonds has been achieved with iodobenzene diacetates as the arylation reagent in moderate to good yields. The procedure tolerates a series of functional groups, such as methoxy, nitro, cyano, chloro, and bromo groups.
- Yu, Peng,Zhang, Guangyou,Chen, Fan,Cheng, Jiang
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supporting information; experimental part
p. 4588 - 4590
(2012/09/22)
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- A highly efficient palladium-catalyzed desulfitative arylation of azoles with sodium arylsulfinates
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A highly efficient palladium-catalyzed direct desulfitative arylation of azoles at C2-position has been developed using sodium arylsulfinates as aryl sources. Azoles including benzoxazoles, benzothiazoles, oxazoles, thiazoles, and 1,3,4-oxadiazoles reacted with sodium arylsulfinates smoothly to generate the corresponding products in good to excellent yields, and various substitution patterns were tolerated toward the reaction.
- Wang, Min,Li, Dengke,Zhou, Wei,Wang, Lei
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experimental part
p. 1926 - 1930
(2012/03/26)
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- Palladium-catalyzed desulfitative arylation of azoles with arylsulfonyl hydrazides
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Palladium-catalyzed desulfitative and denitrogenative arylation of azoles with arylsulfonyl hydrazides has been achieved. A broad scope of azoles and arylsulfonyl hydrazides has been used to produce arylated azoles in high yields.
- Yu, Xinzhang,Li, Xingwei,Wan, Boshun
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p. 7479 - 7482
(2012/10/29)
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- Direct oxidative C-H arylation of benzoxazoles with arylsulfonyl hydrazides promoted by palladium complexes
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This study describes a direct oxidative C-2 arylation of benzoxazoles using arylsulfonyl hydrazides as the aryl sources. A simple catalyst system [Pd(OAc)2 and Ph3P] allows the reactions to proceed smoothly under oxidative reaction conditions. Other heteroarenes such as caffeine and benzothiazole are also applicable substrates. Notably, this catalytic system tolerates halogen substituents which provides a useful complement to the current cross-coupling reactions which use aryl halides.
- Yuen, On Ying,So, Chau Ming,Wong, Wing Tak,Kwong, Fuk Yee
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supporting information
p. 2714 - 2718,5
(2012/12/12)
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- Direct oxidative C-H arylation of benzoxazoles with arylsulfonyl hydrazides promoted by palladium complexes
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This study describes a direct oxidative C-2 arylation of benzoxazoles using arylsulfonyl hydrazides as the aryl sources. A simple catalyst system [Pd(OAc)2 and Ph3P] allows the reactions to proceed smoothly under oxidative reaction conditions. Other heteroarenes such as caffeine and benzothiazole are also applicable substrates. Notably, this catalytic system tolerates halogen substituents which provides a useful complement to the current cross-coupling reactions which use aryl halides. Georg Thieme Verlag KG Stuttgart · New York.
- Yuen, On Ying,So, Chau Ming,Wong, Wing Tak,Kwong, Fuk Yee
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supporting information
p. 2714 - 2718
(2013/01/15)
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- Palladium-catalyzed desulfitative C-H arylation of azoles with sodium sulfinates
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A palladium-catalyzed desulfitative C-H arylation of azoles with sodium sulfinates using Cu(OAc)2·H2O as oxidant has been discovered. The reaction proceeded well for a range of different substrates under oxidative conditions. A series of aryl-substituted azoles have been synthesized in moderate to good yields.
- Chen, Ru,Liu, Saiwen,Liu, Xinhua,Yang, Luo,Deng, Guo-Jun
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supporting information; experimental part
p. 7675 - 7679
(2011/12/03)
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- Palladium-catalyzed desulfitative C-arylation of a benzo[d]oxazole C-H bond with arene sulfonyl chlorides
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A palladium-catalyzed direct desulfitative C-arylation of a benzo[d]oxazole C-H bond with arene sulfonyl chlorides is described. The procedure tolerates halo, cyano, nitro, trifluoromethyl, acetyl and acetylamino groups on the phenyl ring of sulfonyl chlorides, providing the arylation products in moderate to good yields. It represents a practical and attractive alternative for the synthesis of 2-aryl benzoxazoles.
- Zhang, Manli,Zhang, Shouhui,Liu, Miaochang,Cheng, Jiang
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supporting information; experimental part
p. 11522 - 11524
(2011/11/12)
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- Palladium-catalyzed direct arylations, alkenylations, and benzylations through C-H bond cleavages with sulfamates or phosphates as electrophiles
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(Figure Presented) catalytic system comprised of Pd(OAc)2 and bldentate ligand dppe enabled first direct arylatlons with moisture-stable aryl sulfamates as electrophlles, and proved applicable to unprecedented C-H bond functlonallzations with e
- Ackermann, Lutz,Barfuesser, Sebastian,Pospech, Jola
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supporting information; experimental part
p. 724 - 726
(2010/04/02)
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- An Efficient and practical synthesis of benzoxazoles from acyl chlorides and 2-aminophenols catalyzed by Lewis acid in(OTf)3 under solvent-free reaction conditions
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Benzoxazole derivatives have been prepared through the reaction of substituted 2-aminophenols and acyl chlorides in the presence of catalytic amount of In(OTf)3 under solvent-free reaction conditions in good to excellent yields. The method is simple, convenient, environmental-friendly, efficient and practical.
- Wang, Bo,Zhang, Yicheng,Li, Pinhua,Wang, Lei
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experimental part
p. 1697 - 1703
(2011/06/27)
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- Iodine (III)-mediated synthesis of some 2-aryl/ hetarylbenzoxazoles as antibacterial/antifungal agents
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Ten 2-aryl/hetarylbenzoxazoles (5a, 5b, and 6a-h) were synthesized via oxidative cyclization of Schiff bases (3a, 3b, and 4a-h) with 1.1 equivalent of iodobenzene diacetate (IBD) in methanol. All of these 2-aryl/hetarylbenzoxazoles (5a, 5b, and 6a-h) were tested in vitro for their antibacterial and antifungal activities against Bacillus subtilis, Bacillus stearothermophilus, Escherichia coli, and Pseudomonas putida. These compounds also were screened for their antifungal activity against Aspergillus flavus and Aspergillus niger. Biological activity of these compounds was compared with those of commercially available antibiotics, chloramphenicol and antifungal agent cycloheximide. Most of these compounds, 5a, 5b, 6a, 6b, 6d, 6e, 6g, 6h, were equipotent or more potent than these commercial drugs at concentration 100 μg/ml. Birkhaeuser Boston 2009.
- Kumar, Ravi,Nair, Reshmi R.,Dhiman, Saurabh Sudha,Sharma, Jitender,Prakash, Om
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p. 541 - 550
(2011/11/01)
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- Oxidative conversion of amines into benzoxazoles using hydrogen transfer catalysis
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Benzoxazoles are synthesised directly by oxidative condensation of primary and secondary amines with o-aminophenols under hydrogen transfer catalysis. The optimal system utilises 1 mol % of the Shvo catalyst, with dimethoxybenzoquinone as the hydrogen-acc
- Blacker, A. John,Farah, Mohamed M.,Marsden, Stephen P.,Saidi, Ourida,Williams, Jonathan M.J.
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experimental part
p. 6106 - 6109
(2009/12/26)
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- Synthesis of benzoxazoles catalyzed by MCM-41, a green and reusable catalyst
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Benzoxazoles can be rapidly and efficiently synthesized from acyl chloride with 2-aminophenols in one simple step, which provided a practical and efficient method for high-throughput synthesis of this important class of heterocyclic compounds. Copyright Taylor & Francis Group, LLC.
- Shoar, Rahim Hekmat,Heidary, Maryam,Farzaneh, Maryam,Malakouti, Reihaneh
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scheme or table
p. 1742 - 1751
(2009/10/06)
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- Heteropolyacid as a new, green and recyclable catalyst for the synthesis of 2-aryl benzoxazole under solvent-free conditions
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A simple, convenient and general method has been developed for the synthesis of 2-arylbenzoxazole via condensation of o-aminophenols and benzoyl chloride derivatives under solvent-free conditions in the presence of a catalytic amount of heteropolyacids in good yields.
- Heravi, Majid M.,Javanmardi, Najme,Oskooie, Hossein A.,Baghernejad, Bita,Heidari, Maryam,Bamoharram, Fatemeh F.
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experimental part
p. 589 - 593
(2010/06/13)
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- Synthesis of benzazoles by hydrogen-transfer catalysis
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Transition-metal-catalyzed hydrogen-transfer reactions have been used for the conversion of alcohols into benzimidazoles and aldehydes into benzoxazoles and benzothiazoles.
- Blacker, A. John,Farah, Mohamed M.,Hall, Michael I.,Marsden, Stephen P.,Saidi, Ourida,Williams, Jonathan M. J.
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supporting information; experimental part
p. 2039 - 2042
(2009/09/08)
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- Hypervalent iodine(III) mediated synthesis of 2-substituted benzoxazoles
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2-Substituted benzoxazoles (6a-j, 7a-e, 7j-l) have been synthesized via the oxidative intramolecular cyclization of Schiff's bases (4a-j, 5a-e, 5j-l) using iodobenzene diacetate (IBD) as an oxidant in dry methanol. A one-pot procedure for the synthesis of 6a-j, 7a-e and 7j-l starting from o-aminophenol/p-chloro-o- aminophenol and aldehydes has also been developed.
- Prakash, Om,Batra, Anita,Sharma, Vijay,Saini, Rajesh K.,Verma, Rajender S.
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p. 1031 - 1034
(2007/10/03)
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- Hypervalent iodine in synthesis 69: An efficient synthesis of 2-arylbenzoxazoles via the palladium-catalysed carbonylation and condensation of diaryliodonium salts and o-aminophenols
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An efficient synthetic method is reported in which 2-arylbenzoxazoles have been prepared in good to excellent yields under mild reaction conditions by the palladium-catalysed carbonylation of diaryliodonium salts with o-aminophenols followed by dehydrative cyclisation.
- Zhou,Chen
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p. 235 - 237
(2007/10/03)
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- Photolysis of 2-Nitrophenyl Benzyl Ethers in Neutral and Acidic Media
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2-Nitrophenyl benzyl ethers (1a-d) on irradiation afford N-benzoyl-2-aminophenols (4) as the major products.The other minor products are 2-nitrophenol (2), 4-benzyl-2-nitrophenol (3), 2-phenylbenzoxazoles (5) and 2-nitrophenyl benzoate (6).A plausible mechanism to account for the formation of various products is discussed.
- Jacob E. Dominic,Joshua, C. P.
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p. 808 - 810
(2007/10/02)
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