- Novel carbazole-based multifunctional materials with a hybridized local and charge-transfer excited state acting as deep-blue emitters and phosphorescent hosts for highly efficient organic light-emitting diodes
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In this work, two carbazole- and benzo[d]oxazole-based novel multifunctional materials with a hybridized local and charge-transfer (HLCT) characteristic, namely,OCIandOCT, which could act as deep-blue fluorophors and phosphorescent hosts, were first desig
- Gao, Zhixiang,Huang, Jinhai,Jin, Xin,Miao, Yanqin,Su, Jianhua,Tian, He,Wang, Hua,Yin, Mengna,Zhao, Zhenhong,Zhou, Haitao
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- Dowex 50W: A green mild reusable catalyst for the synthesis of 2-aryl benzoxazole derivatives in aqueous medium
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In this work simple efficient, one pot and environmentally friendly method was developed for the synthesis of 2-Aryl-1H-benzoxazole derivatives at 80oC using ortho-aminophenol and various aldehydes. It has been found that Dowex 50W is an effective catalyst to prepare moderate to high yield of a variety of benzoxazole derivatives through a clean and simple process. Aqueous medium, green methodology, rapid reaction, reusability of heterogeneous catalyst are the great advantages of this protocol.
- Datta, Arup
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p. 341 - 347
(2021/05/19)
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- Organic electrophosphorescent host material and application thereof in organic electroluminescent device
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The invention relates to the technical field of organic electroluminescent devices, in particular to an organic electroluminescent material and application thereof in an organic electroluminescent device. The organic electroluminescent material has good p
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Paragraph 0042-0045
(2021/05/12)
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- Carbazole-based organic electroluminescent material and application thereof in devices
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The invention relates to the technical field of organic electroluminescent devices, in particular to a carbazole-based organic electroluminescent material and application thereof in an organic electroluminescent device. The organic electroluminescent mate
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Paragraph 0049-0052
(2021/05/29)
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- Delivering 2-Aryl Benzoxazoles through Metal-Free and Redox-Neutral De-CF3Process
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An unexpected cleavage of the Csp3-CF3 bond of CF3-hydrobenzoxazoles has been disclosed, affording a range of 2-aryl benzoxazoles under metal-free and redox-neutral conditions. This transformation has demonstrated broad substrate scope and good compatibility of functional groups. 2-Aryl benzothiazole and 2-aryl benzoimidazole could be smoothly assembled in the same manner. On the basis of preliminary mechanistic studies, base initiated and aromatization driven β-carbon elimination was considered to be the key step for the formation of 2. This reaction offers an alternative, facile, and sustainable route to access important 2-aryl benzoxazole motifs.
- Qiao, Xinxin,Zhao, Yong-De,Rao, Mingru,Bu, Zhan-Wei,Zhang, Guangwu,Xiong, Heng-Ying
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p. 13548 - 13558
(2021/10/01)
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- TEMPO-mediated aerobic oxidative synthesis of 2-aryl benzoxazoles via ring-opening of benzoxazoles with benzylamines
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A simple and efficient TEMPO-mediated system for aerobic oxidative synthesis of 2-aryl benzoxazoles from readily available benzoxazoles and primary benzylic and hetero benzylic amines is presented in one pot. The reaction proceeds through the ring-opening of benzoxazoles and is followed by oxidative condensation with benzylamines. These metal-free, straightforward reactions worked well with a wide range of substrates, yielding moderate to good yields under mild conditions using air as an external green oxidant.
- Rao, Mugada Sugunakara,Hussain, Sahid
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p. 2684 - 2694
(2021/07/26)
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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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- Heterocyclic reaction inducted by Br?nsted–Lewis dual acidic Hf-MOF under microwave irradiation
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Use of green chemistry and alternative strategies has been explored to prepare diverse organic derivatives. The combination between heterogeneous catalyst, environmentally benign reaction and high-yielding methods is gaining momentum. Herein, a defective 6-connected Hf-MOF, named Hf-BTC, was efficiently synthesized and characterized for the heterogeneous catalysis under microwave irradiation. The MOF features including structural defect, porosity, acidity, and stability was analyzed by powder X-ray diffraction, N2 sorption isotherms, acid-base titration, and thermal gravimetric analysis. In the catalytic studies, the Br?nsted-Lewis dual acidic Hf-BTC was efficiently applied for the synthesis of the heterocyclic compounds via the microwave-assisted cycloaddition and condensation reactions. The reactions proceeded smoothly in the presence of the Hf-MOF with a broad scope of substrates provided the expected products in high to excellent yields (up to 99 %) for few minutes and the catalyst could be easily recycle over many consecutive reactions without loss of its reactivity and structure.
- Nguyen, Linh Ho Thuy,Nguyen, Trang Thi Thu,Dang, Minh-Huy Dinh,Tran, Phuong Hoang,Doan, Tan Le Hoang
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- Iron(0)-Catalyzed Transfer Hydrogenative Condensation of Nitroarenes with Alcohols: A Straightforward Approach to Benzoxazoles, Benzothiazoles, and Benzimidazoles
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The iron-catalyzed hydrogen transfer strategy has been applied to the redox condensation of o-hydroxynitrobenzene with alcohol, leading to the formation of benzoxazole derivatives. A wide range of 2-substituted benzoxazoles were synthesized in good to excellent yields without the addition of an external redox agent. A series of control experiments provided a plausible mechanism. Furthermore, the reaction system was successfully extended to the synthesis of benzothiazoles and benzimidazoles.
- Putta, Ramachandra Reddy,Chun, Simin,Choi, Seung Hyun,Lee, Seok Beom,Oh, Dong-Chan,Hong, Suckchang
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p. 15396 - 15405
(2020/12/02)
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- Synthesis and X-ray crystal structures of three new nickel(II) complexes of benzoylhydrazones: Catalytic applications in the synthesis of 2-arylbenzoxazoles
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Three new complexes of nickel(II), having general formula [Ni(L1)(PPh3)] (1), [Ni(L1)(4-picoline)] (2), and [Ni(L2)(4-picoline)] (3) were synthesized by the reaction of Ni(OAc)2·4H2O with corresponding benzolyhydrazine-derived Schiff base ligands i.e. [4-(diethylamino)-2-hydroxybenzylidene]-benzohydrazonic acid (H2L1) or [2-(hydroxynaphthalen-1-yl)methylene]-benzohydrazonic acid (H2L2) and PPh3/4-picoline as co-ligand in 1:1:1 ratio in methanol. All the three complexes were air-stable, isolated as reddish brown solids and characterized by Elemental analysis, FT-IR, 1H, 13C{1H}, 31P{1H} NMR spectroscopy and mass spectrometry. The structures of all three complexes were determined by single crystal X-ray diffraction studies which revealed the distorted square planar geometry of the complexes. In these complexes, three coordination sites were occupied by ONO pincer type Schiff base ligand and the fourth site was blocked by phosphorus (P) or nitrogen (N) atom of the co-ligand. The catalytic potential of all three complexes was explored in the synthesis of a series of 2-arylbenzoxazoles from aldehydes and 2-aminophenol, using low catalyst loading (0.5 mol%). Complex 1 was found to be the best catalyst among three complexes, for the synthesis of a series of 2-aryl benzoxazoles. The ease of synthesis, air-stability and robustness of the catalyst, and good TONs are some of the key characteristics of the described catalytic system.
- Layek, Samaresh,Agrahari, Bhumika,Kumar, Akash,Dege, Necmi,Pathak, Devendra D.
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- In-vitro Anti-cancer assay and apoptotic cell pathway of newly synthesized benzoxazole-N-heterocyclic hybrids as potent tyrosine kinase inhibitors
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A series of benzoxazole-N-heterocyclic hybrids have been synthesized by a one-pot strategy. Molecular docking study revealed that such compounds have the ability to inhibit enzyme protein tyrosine kinase. The findings of this work have been the successful synthesis of benzoxazole scaffolds, featuring hybrids of benzoxazole with quinoline and quinoxaline respectively. The molecular docking studies have showed these compounds to be inhibitors of tyrosine kinase enzyme which triggers growth of cancer cells. The cytotoxicity study of compounds 4a-f showed better potency against breast cancer cell lines MCF-7 and MDA-MB-231 in contrast to oral and lung cancer cell lines KB and A549. The tyrosine kinase activity was measured using Universal Tyrosine Kinase Assay kit using horseradish peroxide (HRP)-conjugated anti-phosphotyrosine kinase solution as a substrate. The compounds 4c exhibited maximum inhibition in the activity of enzyme tyrosine kinase with IC50 value 0.10 ± 0.16 μM, than other compounds which were studied and thus proved to be inhibitors of enzyme tyrosine kinase. The selective index of all four compounds was found out to be greater than two, indicating the non-toxic behaviour, i.e. good anti-cancer activity. Further, fluorescence microscopic study helped to characterize the mode of cell death, which was found to be late apoptosis as indicated by the orange fluorescence. The SAR analysis has also been carried out.
- Desai, Sulaksha,Desai, Vidya,Shingade, Sunil
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supporting information
(2019/11/13)
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- Sulfur-Promoted Synthesis of Benzoxazoles from 2-Aminophenols and Aldehydes
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Elemental sulfur (S8) was found to be an excellent stoichiometric oxidant to promote oxidative condensation of 2-aminophenols with a wide range of aldehydes, including aliphatic aldehyde such as cyclohexanecarboxaldehyde. The reactions were catalyzed by sodium sulfide in the presence of DMSO as an additive. The benzoxazole products were obtained in satisfactory yields. The reaction conditions could be applied to larger syntheses (10–50 mmol).
- Nguyen, Le Anh,Dang, Thai Duy,Ngo, Quoc Anh,Nguyen, Thanh Binh
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supporting information
p. 3818 - 3821
(2020/06/10)
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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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- Efficient Cu-catalyzed intramolecular: O -arylation for synthesis of benzoxazoles in water
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An efficient method was developed for synthesis of benzoxazoles by Cu-catalyzed intramolecular O-arylation of o-halobenzanilides in water. This strategy provides several advantages, such as high yields, water as a green solvent and functional groups tolerance.
- Gao, Hui,Li, Minxin,Mao, Zewei,Rao, Gaoxiong,Tang, Yanling
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p. 14317 - 14321
(2020/04/23)
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- Diamine monomer containing benzoxazole and carbazole structures, and preparation method and application thereof
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The invention discloses a diamine monomer containing benzoxazole and carbazole structures, and a preparation method and an application thereof. Starting from dihalogenated carbazole, active hydrogen in monomer carbazole is grafted with a structural unit c
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Paragraph 0063-0067
(2020/06/02)
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- Acid-promoted cleavage of the C–C double bond of N-(2-Hydroxylphenyl)enaminones for the synthesis of benzoxazoles
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An acid-mediated selective cleavage of C–C double bond of N-(2-hydroxylphenyl)enaminones with formation a new C–O bond for the synthesis of 2-substituted benzoxazoles has been developed. This protocol proceeds under transition metal- and oxidant-free conditions with broad functional group tolerance. The oxidative cleavage of C–C double bond of N-(2-hydroxylphenyl)enaminone is also realized using NCS or NFSI as oxidants with release of 2,2-dihalogen-acetophenone fragments.
- Ge, Bailu,Peng, Yanling,Liu, Jing,Wen, Si,Peng, Cheng,Cheng, Guolin
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- Sulfur/DABCO Promoted Reductive Coupling/Annulation Cascade Reaction between o -Hydroxy/Amino Nitrobenzenes and Benzaldehydes
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Sulfur/DABCO was found to be an efficient reagent in promoting- the reductive coupling/annulation of o -nitrophenols or o -nitroanilines with benzaldehydes. This method represents a simple, straightforward, and green approach to the construction of benz-oxazoles and benzimidazoles.
- Dang, Minh-Huy Dinh,Nguyen, Linh Ho Thuy,Tran, Phuong Hoang
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supporting information
p. 1687 - 1694
(2020/05/25)
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- 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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- Method for synthesizing benzoxazole through microwave radiation of benzamide compound in water phase
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The invention discloses a method for synthesizing benzoxazole through microwave radiation of a benzamide compound in a water phase. The benzamide compound is added into the water phase under the microwave condition to be subjected to a cyclization reaction for generating the benzoxazole under the alkali condition, and the method for preparing the benzoxazole is environmentally friendly, easy and convenient to operate, safe, low in cost and efficient. Compared with the prior art, the method can be applied to a large number of functional groups, the yield is high, the number of by-products is small, and the method is easy to operate, safe, low in cost and environmentally friendly. (Please see the specifications for the formula).
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Paragraph 0051
(2019/03/08)
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- Method used for rapid preparation of benzo-heterocycle compound with physical grinding under solvent-free room temperature conditions
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The invention discloses a method used for rapid preparation of benzo-heterocycle compound with physical grinding under solvent-free room temperature conditions. According to the method, glacial aceticacid is taken as a catalyst; at solvent-free room temperature conditions, physical grinding is adopted, reaction of 2-substituted arylamines (2-mercapto arylamine, 2-aminophenol, and o-phenylenediamine) and aromatic aldehydes is carried out using physical grinding. The method is friendly to the environment, is simple in operation, is safe, is low in cost, and is high in efficiency. Compared withthe prior art, the advantages are that: the method is suitable for a large amount of functional groups, yield is high, less by-product is generated, operation is simple, the method is safe, cost is low, and the method is friendly to the environment.
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Paragraph 0062; 0073
(2019/01/21)
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- Preparation method of 2-benzooxazole compound
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The invention relates to a preparation method of a 2-phenylbenzoxazole compound. The structural formula of the prepared 2-phenylbenzoxazole compound is shown in Figure 1, wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are a hydrogen atom, an alkyl group, an alkoxy group, halogen and trifluoromethyl. The preparation method is as follows: a phenolic compound, a diketone compound, alkali and a solvent are blended under room temperature to 200 DEG C for 1 to 24 hours; after reaction is complete, quenching is carried out, organic solvent extraction, concentration and purification are carried out, so that the 2-phenylbenzoxazole compound is obtained, and the yield is 37 to 78 percent. The preparation method has the characteristics of easy material obtainment, mild reaction condition, short reaction time, simplicity in operation and the like.
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Paragraph 0014
(2019/12/25)
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- Pd/Cu bimetallic co-catalyzed direct 2-arylation of benzoxazole with aryl chloride
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An efficient Palladium/Copper bimetallic co-catalyzed direct 2-arylation of benzoxazoles with aryl chlorides is presented. The Pd(OAc)2/CuI/NiXantphos-based catalyst enables the installation of various aryl and heteroaryl groups in good to excellent yields (75–99%). Preliminary mechanism investigation indicates that Pd/Nixantphos complex activates C-Cl bond of aryl chlorides via oxidative addition, and Cu/Nixantphos complex chelates with nitrogen atom to lower the pKa of the 2-H in benzoxazoles.
- Zheng, Ling-Li,Yin, Bo,Tian, Xing-Chuan,Yuan, Ming-Yong,Li, Xiao-Huan,Gao, Feng
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supporting information
(2019/11/13)
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- Transition-Metal-Free Alkylation/Arylation of Benzoxazole via Tf2O-Activated-Amide
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A transition-metal-free approach to the alkylation/arylation of benzoxazole was developed by employing Tf2O-activated-amide as the alkylating/arylating reagent. The mild reaction conditions, and particularly insensitivity to air and water, further enhance the synthetic potential in pharmaceutical synthesis. (Figure presented.).
- Niu, Zhi-Jie,Li, Lian-Hua,Liu, Xue-Yuan,Liang, Yong-Min
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supporting information
p. 5217 - 5222
(2019/11/13)
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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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- A 2 - substituted benzoxazole derivative of the preparation method
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The invention discloses a 2 - substituted benzoxazole derivative of the preparation method, its reaction as follows: . The present invention can be 2 - substituted pyrrole derivatives, acetophenone derivatives can be obtained and at the same time 2, 2 - dihalo acetophenone derivatives; and through the C (sp2 ) - C (sp2 ) At the same time selectively fracture of the aromatization. The method of the invention the resulting raw materials are easy, high yield, mild reaction conditions, the reaction time is short, wide substrate range, reaction specificity is strong, easy post treatment and green environmental protection.
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Paragraph 0062-0065
(2019/07/04)
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- Cesium Fluoride and Copper-Catalyzed One-Pot Synthesis of Benzoxazoles via a Site-Selective Amide C?N Bond Cleavage
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We report herein a two-step one-pot strategy for the synthesis of benzoxazoles from amides by using cesium fluoride/copper as catalysts. This approach involves the in situ generation of acyl fluorides from the corresponding amides, and the acyl fluorides undergo transamidation and cyclization to give benzoxazoles in good yields. In this work, the amide C?N bonds are activated by CsF to form the acyl fluoride intermediates, which further react with o-bromoanilines to efficiently yield benzoxazoles. Notably, this methodology demonstrates a broad substrate scope, as primary/secondary benzamides are well tolerated, and this process might facilitate the development of one-pot transformations of amides. (Figure presented.).
- Luo, Zhongfeng,Wu, Hongxiang,Li, Yue,Chen, Yuwen,Nie, Jingyi,Lu, Siqi,Zhu, Yulin,Zeng, Zhuo
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supporting information
p. 4117 - 4125
(2019/08/01)
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- Continuous flow/waste-minimized synthesis of benzoxazoles catalysed by heterogeneous manganese systems
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Herein, we present our results on the development of a waste minimized protocol for the synthesis of 2-arylbenzoxazoles in continuous flow. Manganese-based heterogeneous catalysts were used in combination with cyclopentylmethyl ether as an environmentally friendly and safe reaction medium. The use of oxygen promotes the oxidative process ensuring at the same time a complete regeneration of the catalyst adopting a flow configuration which does not include the use of an additional mechanical pump. These features allowed for a faster synthesis compared to batch procedures with minimal metal leaching.
- Ferlin, Francesco,Van Der Hulst, Mitchell K.,Santoro, Stefano,Lanari, Daniela,Vaccaro, Luigi
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supporting information
p. 5298 - 5305
(2019/10/11)
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- Zr and Hf-metal-organic frameworks: Efficient and recyclable heterogeneous catalysts for the synthesis of 2-arylbenzoxazole via ring open pathway acylation reaction
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Zirconium- and hafnium-based metal–organic frameworks which constructed by 12-coordinated clusters and 6-coodinated clusters were shown to be highly effective heterogeneous catalysts for the ring opening acylation of benzoxazole to 2-arylbenzoxazole under solvent free conditions. Owning the wide opening spaces structures and inherent formate sites, MOFs based on 6-connected Zr6/Hf6 node were able to identify a significantly enhanced yield in Br?nsted acid catalyzed reactions under conventional heating and microwave irradiation. In addition, the detailed mechanism of active sites of the ring opening acylation reaction was confirmed by employing of density functional theory (DFT) calculations.
- Nguyen, Linh Ho Thuy,Nguyen, Trang Thi Thu,Tran, Phuong Hoang,Kawazoe, Yoshiyuki,Le, Hung Minh,Doan, Tan Le Hoang
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supporting information
p. 110 - 117
(2019/05/08)
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- Magnetic Nanoparticle Decorated N-Heterocyclic Carbene–Nickel Complex with Pendant Ferrocenyl Group for C–H Arylation of Benzoxazole
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Abstract: Magnetic nanoparticle decorated N-heterocyclic carbene–nickel complex with pendant ferrocenyl group has been prepared by multi-step procedure. The formation of complex was confirmed on the basis of analytical techniques such as Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and X-ray photoelectron spectroscopy (XPS) as well as by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) analysis. The complex proved to be an efficient heterogeneous catalyst for C–H arylation of benzoxazole with aryl boronic acids. The recycling studies revealed that complex could be reused for six times without significant decrease in catalytic activity. Graphical Abstract: [Figure not available: see fulltext.].
- Naikwade, Altafhusen,Jagadale, Megha,Kale, Dolly,Gajare, Shivanand,Rashinkar, Gajanan
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p. 3178 - 3192
(2018/08/25)
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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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- Oxidative NHC Catalysis for the Generation of Imidoyl Azoliums: Synthesis of Benzoxazoles
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N-Heterocyclic carbene (NHC)-catalyzed intramolecular cyclization of aldimines generated from 2-amino phenols and aromatic aldehydes leading to the synthesis of 2-arylbenzoxazoles under mild conditions is presented. The reaction proceeds via the generation of the aza-Breslow intermediates from imines and NHC, which under oxidative conditions form the key imidoyl azoliums and a subsequent intramolecular cyclization furnishes the product. The reaction tolerates a broad range of functional groups, and the products are formed in generally good yields.
- Patra, Atanu,James, Anjima,Das, Tamal Kanti,Biju, Akkattu T.
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p. 14820 - 14826
(2019/01/03)
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- A benzoxazole for the arylation method (by machine translation)
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The invention relates to a benzoxazole for the arylation method, comprises the following steps: under the protection of the inert gas, the benzoxazole, aryl/heteroaryl tosylates, catalyst nitrogen heterocyclic carbene - palladium complex, alkaline material, reaction solvent, in the 80 - 150 °C reaction 12 - 24 H of the reaction liquid obtained, then processing reaction liquid to obtain product, to obtain 2 - aryl benzoxazole. The invention discloses a benzoxazole for the arylation method development of novel catalytic system, catalyst stability, is easy to obtain, can make the stable, low price of the aryl/heteroaryl tosylates participate in the reaction, reaction operation is simple, low cost, product yield and purity and the like, has good value for research and industrial application produces the scenery. (by machine translation)
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Paragraph 0058
(2018/11/03)
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- Iron-Catalyzed Sulfur-Promoted Decyanative Redox Condensation of o-Nitrophenols and Arylacetonitriles: An Unprecedented Route to 2-Arylbenzoxazoles
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Elemental sulfur in the presence of a catalytic amount of FeCl2·4H2O was found to be highly efficient for the promotion of decyanative redox condensation reactions of o-nitrophenols with arylacetonitriles, to give a wide range of 2-arylbenzoxazoles. The utility of elemental sulfur was highlighted by its role as cyanide scavenger and external reducing agent.
- Nguyen, Thanh Binh,Lung, Jerome Cheung
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supporting information
p. 5815 - 5818
(2018/11/24)
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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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- Unexpected Decarboxylation-Triggered o-Hydroxyl-Controlled Redox Condensation of Phenylglycines with 2-Nitrophenols in Aqueous Media
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A decarboxylation-triggered and o-hydroxyl-controlled hydrogen-transfer strategy for the one-pot synthesis of benzoxazoles from readily available amino acids and 2-nitrophenols is reported. On the basis of this autoredox reaction, the C?N bond can be efficiently constructed to afford the desired products in moderate to good yields under transition-metal-free conditions in aqueous media. (Figure presented.).
- Tang, Lin,Yang, Zhen,Sun, Tian,Zhang, Di,Ma, Xiantao,Rao, Weihao,Zhou, Yuqiang
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supporting information
p. 3055 - 3062
(2018/08/01)
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- One-pot formic acid dehydrogenation and synthesis of benzene-fused heterocycles over reusable AgPd/WO2.72 nanocatalyst
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Using nanoparticles (NPs) to catalyze multiple chemical reactions in one-pot and to achieve high-yield syntheses of functional molecules/materials is an important direction in NP chemistry, catalysis and applications. In this article, we report a nanocomposite of AgPd NPs anchored on WO2.72 nanorods (NRs) (denoted as AgPd/WO2.72) as a general catalyst for formic acid dehydrogenation and transfer hydrogenation from Ar-NO2 to Ar-NH2 that further reacts with aldehydes to form benzene-fused heterocyclic compounds. The AgPd/WO2.72 catalysis is Ag/Pd dependent and Ag48Pd52 is the most active composition for the multiple chemical reactions. The high activity of AgPd/WO2.72 arises from strong interfacial interaction between AgPd and WO2.72, resulting in AgPd lattice expansion and electron polarization from AgPd to WO2.72. The syntheses proceed in one-pot reactions among formic acid, 2-nitrophenol (or 2-nitroaniline, or 2-nitrothiophenol) and aldehydes in dioxane/water (2/1 v/v) at 80-90 °C, leading to one-pot syntheses of benzoxazoles, benzimidazoles and benzothiazoles that are key ring structures present in functional compounds for pharmaceutical, optical and polymer applications.
- Yu, Chao,Guo, Xuefeng,Shen, Bo,Xi, Zheng,Li, Qing,Yin, Zhouyang,Liu, Hu,Muzzio, Michelle,Shen, Mengqi,Li, Junrui,Seto, Christopher T.,Sun, Shouheng
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p. 23766 - 23772
(2018/12/10)
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- Synthesis of benzoxazoles via an iron-catalyzed domino C-N/C-O cross-coupling reaction
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An eco-friendly and efficient method has been developed for the synthesis of 2-arylbenzoxazoles via a domino iron-catalyzed C-N/C-O cross-coupling reaction. Some of the issues typically encountered during the synthesis of 2-arylbenzoxazoles in the presence of palladium and copper catalysts, including poor substrate scope and long reaction times have been addressed using this newly developed iron-catalyzed method.
- Yang, Bo,Hu, Weiye,Zhang, Songlin
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p. 2267 - 2270
(2018/02/06)
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- Method for preparing benzoxazole compound by heterogeneous catalytic oxidation
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The invention discloses a method for preparing a benzoxazole compound by heterogeneous catalytic oxidation. The method comprises the following steps: mixing phenolic Schiff base, an OMS-2 type manganese oxide octahedral molecular sieve, an oxidant and carbonic esters and reacting to obtain the benzoxazole compound, wherein structures of the phenolic Schiff base and the benzoxazole compound are respectively shown as formulas I and II: the formula I is shown in the description and the formula II is shown in the description, wherein R can be selected from hydrogen, alkyl, alkoxyl, hydroxyl, an ester group, a carboxylic group or halogen; R can be selected from alkyl, aryl and alkenyl. According to the method disclosed by the invention, a green catalytic reaction system which is composed of a heterogeneous catalyst OMS-2 type manganese oxide molecular sieve, a green oxidant H2O2 and a green medium carbonate and has a long service life and is cheap is adopted, so that an acid-alkali additive can be avoided; the catalyst has high activity and a long service life; the method disclosed by the invention is simple to operate and has moderate reaction conditions; new three wastes are not generated and the method is clean and environmentally friendly; the solvent treatment cost can be reduced and the conversion rate of reactants and the yield of a target product are improved, so that the method can be more adaptive to industrial application to the greater extent.
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Paragraph 0031; 0032
(2017/10/28)
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- OMS-2/H2O2/Dimethyl Carbonate: An Environmentally-Friendly Heterogeneous Catalytic System for the Oxidative Synthesis of Benzoxazoles at Room Temperature
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A manganese octahedral molecular sieve (OMS-2) was found to be an efficient and recyclable heterogeneous catalyst for the oxidative synthesis of benzoxazoles in the gram-scale from phenolic imines at room temperature. H2O2 and biobased reagent dimethyl carbonate (DMC) were successfully employed as the environmentally friendly oxidant and solvent, respectively, in an OMS-2-catalysted redox reaction for the first time. Benzoxazoles could also be obtained from N-substituted 2-aminophenols via Cu(OH)x/OMS-2-catalyzed sequential oxidative transformation at elevated temperatures.
- Meng, Xu,Wang, Yuanguang,Chen, Baohua,Chen, Gexin,Jing, Zhenqiang,Zhao, Peiqing
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p. 2018 - 2024
(2017/12/26)
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- Containing heteroaryl chelating nitrogen heterocyclic cabeen arrowhead compound and its preparation method
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The invention belongs to the field of organic compound synthesis and discloses a chelate-type N-heterocyclic carbene palladium compound containing heteroaromatic groups, and a synthetic and immobilization method thereof. The general formula of the compound is represented as follows. In the invention, with a polyfunctional compound amino alcohol as an initial raw material, a cyclization reaction and a condensation reaction are carried out to prepare an imidazole derivative of which an N-substituent group contains hydroxyl groups. The derivative then is subjected to an ionization reaction with a hetero-aromatic hydrocarbon halogenate to obtain a hetero-aromatic and hydroxyl groups di-substituted imidazolium salt. The imidazolium salt is further subjected to a metallization reaction to obtain an NHC-N chelate-type palladium compound. The compound has the activity of a homogeneous-phase N-heterocyclic carbene palladium catalyst, is simple in synthetic method, is high in yield, is easy to separate and is recyclable in catalysis of a C-H activating reaction, is greatly reduced in use cost and has a good application prospect in the field of catalysis.
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Paragraph 0058-0059; 0061
(2017/10/06)
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- Iron-catalyzed 2 - benzenes and wicked zuozuo apperception for the synthesis of the new method
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The invention discloses a new synthesis method of iron-catalyzed 2-aryl benzoxazoles, which is prepared by directly performing C-N coupling and C-O coupling on benzamide and o-bromoiodobenzene serving as raw materials at a certain temperature in the presence an iron salt, a ligand and an alkali. According to the invention, a biological metal iron is introduced in synthesis of medical skeletons 2-aryl benzoxazoles, thus use of high-toxicity metals like palladium is avoided, and the application range of the method is expanded to substrates containing different substituent groups. The invention also successfully develops a catalyzing system which can have a catalysis effect on C-N and C-O coupling at the same time, and can greatly improve the safety of 2-aryl benzoxazoles in the synthesis process.
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Paragraph 0019-0020; 0027-0028
(2018/01/11)
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- A new face of phenalenyl-based radicals in the transition metal-free C-H arylation of heteroarenes at room temperature: Trapping the radical initiator: Via C-C σ-bond formation
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The radical-mediated transition metal-free approach for the direct C-H bond functionalization of arenes is considered as a cost effective alternative to transition metal-based catalysis. An organic ligand-based radical plays a key role by generating an aryl radical which undergoes a subsequent functionalization process. The design principle of the present study takes advantage of a relatively stable odd alternant hydrocarbon-based phenalenyl (PLY) radical. In this study, the first transition metal-free catalyzed direct C-H arylation of a variety of heteroarenes such as azoles, furan, thiophene and pyridine at room temperature has been reported using a phenalenyl-based radical without employing any photoactivation step. This protocol has been successfully applied to the gram scale synthesis of core moieties of bioactive molecules. The phenalenyl-based radical initiator has been characterized crystallographically by trapping it via the formation of a C-C σ-bond between the phenalenyl radical and solvent-based radical species.
- Ahmed, Jasimuddin,Sreejyothi,Vijaykumar, Gonela,Jose, Anex,Raj, Manthan,Mandal, Swadhin K.
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p. 7798 - 7806
(2017/10/30)
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- AgPd Nanoparticles Deposited on WO2.72 Nanorods as an Efficient Catalyst for One-Pot Conversion of Nitrophenol/Nitroacetophenone into Benzoxazole/Quinazoline
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We report a seed-mediated growth of 2.3 nm AgPd nanoparticles (NPs) in the presence of 40 × 5 nm WO2.72 nanorods (NRs) for the synthesis of AgPd/WO2.72 composites. The strong interactions between AgPd NPs and WO2.72 NRs make the composites, especially the Ag48Pd52/WO2.72, catalytically active for dehydrogenation of formic acid (TOF = 1718 h-1 and Ea = 31 kJ/mol) and one-pot reactions of formic acid, 2-nitrophenol, and aldehydes into benzoxazoles in near quantitative yields under mild conditions. The catalysis can also be extended to the one-pot reactions of ammonium formate, 2-nitroacetophenone, and aldehyde for high yield syntheses of quinazolines. Our studies demonstrate a new catalyst design to achieve a green chemistry approach to one-pot reactions for the syntheses of benzoxazoles and quinazolines.
- Yu, Chao,Guo, Xuefeng,Xi, Zheng,Muzzio, Michelle,Yin, Zhouyang,Shen, Bo,Li, Junrui,Seto, Christopher T.,Sun, Shouheng
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supporting information
p. 5712 - 5715
(2017/05/04)
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- Atom economic palladium catalyzed novel approach for arylation of benzothiazole and benzoxazole with triarylbismuth reagents via C[sbnd]H activation
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We have developed a novel method for the direct C[sbnd]H functionalization of benzothiazole and benzoxazole using triarylbismuth reagents. The arylation proceeds using the homogeneous catalytic system PdCl2, Cu(OAc)2 and PPh3 ligand. Triarylbismuthines, which act as threefold arylating reagents, have low toxicity, are green and ecofriendly. These methodologies are particularly useful to prepare arylated benzothiazoles and benzoxazoles.
- Balsane, Kishor Eknath,Gund, Sitaram Haribhau,Nagarkar, Jayashree Milind
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- A mild, efficient and reusable solid phosphotungestic acid catalyst mediated synthesis of benzoxazole derivatives: A grinding approach
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Background: The development of efficient methodologies for the preparation of benzoxazole and its derivatives has gained a lot of importance in current research. There are many methods are reported for the synthesis of benzoxazoles includes condensation of 2-aminophenol with carboxylic acid. Traditional methods also have several side reactions, non renewable oxidative reagents and solvents which negatively affect the environmentally and eco-friendly nature of the reaction. We have developed PTA catalyzed synthesis of 2-arylbenzoxazole from 2-aminophenols with different aromatic aldehydes using a grinding strategy in excellent yield. Methods: The synthesis of benzoxazoles in high yields by using silica supported Rangappa S. Keri PTA/PTA as solid acid catalyst at room temperature using grinding method. Results: Aromatic aldehydes which have electron donating or electron withdrawing groups were also investigated and as expected it gives good to excellent yield of products, it can be seen that electron donating and electron withdrawing groups does not show any difference on their action yields. Conclusion: We have developed PTA catalyzed synthesis of 2-arylbenzoxazole from 2-aminophenols with different aromatic aldehydes using a grinding strategy in excellent yield. The use of this reusable catalyst under solvent-free conditions has made this protocol practical, environmentally friendly and economically attractive. The simple work-up procedure, the short reaction times the mild reaction conditions, the high yields of products and the non-toxicity of the catalyst are other advantages of the present method. This protocol approaches combines the advantages of both focused library synthesis and diversity oriented synthesis because of the simplification of reaction protocol that we have been developed.
- Patil, Mahadeo R.,Yelamaggad, Aditya,Keri, Rangappa S.
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p. 474 - 481
(2016/11/19)
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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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- Benzoxazole and benzimidazole compounds and preparation method thereof
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The invention discloses a preparation method of benzoxazole and benzimidazole compounds. A specific structural formula of the benzoxazole and benzimidazole compounds is described in the specification, wherein R1 is aryl, substituted aryl or alkyl; R2 is fluorine, chlorine, methoxyl or methyl; and X is oxygen, nitrogen or nitrogen methyl. The preparation method comprises the following steps: taking amino acid and o-nitrophenol (ortho-nitroaniline) compounds sold on the market as starting materials of reaction, and stirring and heating in a solvent under the catalytic action of an alkaline reagent, so that various substituted benzoxazole and benzimidazole compounds can be obtained with high yield. Reaction conditions are mild, no extra oxidizing agent, reducing agent, ligand or transition metal catalyst needs to be added. The preparation method has the advantages of low cost, simple operation and realization of mass production. Experimental results show that the yield of the obtained benzoxazole and benzimidazole compounds can reach 95%.
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Paragraph 0081; 0082; 0083
(2016/10/10)
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- S8-Mediated Cyclization of 2-Aminophenols/thiophenols with Arylmethyl Chloride: Approach to Benzoxazoles and Benzothiazoles
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A metal-free approach to benzazoles from arylmethyl chlorides and 2-mercaptan/2-hydroxyanilines using elemental sulfur as a traceless oxidizing agent has been developed. The reactions proceeded in good to excellent yields, exhibiting good functional groups tolerance and gram-scale ability. A key mechanistic investigation indicated that the key intermediate trisulfide 6, which was characterized by NMR, HRMS and crystal X-ray crystallography, was separated in the reaction prior to the formation of the product.
- Gan, Haifeng,Miao, Dazhuang,Pan, Qiang,Hu, Renhe,Li, Xiaotong,Han, Shiqing
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supporting information
p. 1770 - 1774
(2016/07/07)
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- Graphene oxide as a heterogeneous reagent promoted synthesis of 2-substituted 1,3-benzazoles in water
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An efficient chemical method for the synthesis of benzimidazoles, benzothiazoles, and benzoxazoles has been developed through the condensation of various aldehydes with o-phenylenediamine, o-aminothiophenol, and o-aminophenol using graphene oxide (GO) as an oxidant in water. These benzazoles are also prepared through a one-pot oxidation/condensation tandem process by reacting alcohols with 2-amino-(thio)phenol/aniline in the presence of GO in poly(ethylene glycol) as a safe media. Moreover, this carbonaceous material could be readily separated using a simple filtration.
- Khalili, Dariush,Banazadeh, Ali Reza
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p. 1693 - 1706
(2016/01/26)
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- Copper-catalyzed selective arylations of benzoxazoles with aryl iodides
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A copper-catalyzed direct ring-opening double N-arylation of benzoxazoles with aryl iodides has been developed. The present system exhibits high selectivity despite competition from C-arylation. The selectivity between ring-opening N-arylation and C-arylation was controlled by the choice of reaction vessel. The nitrile bound bis(triphenylphosphine)copper cyanide was identified as the active catalytic species for both reactions, and when combined with a nitrile-containing solvent, enhanced the reaction efficiency.
- Kim, Donghae,Yoo, Kwangho,Kim, Se Eun,Cho, Hee Jin,Lee, Junseong,Kim, Youngjo,Kim, Min
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p. 3670 - 3676
(2015/04/14)
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