- 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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- Oxidation of N-benzylidene-2-hydroxyaniline by dioxygen catalysed by a dicobalt complex
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The oxidation of N-benzylidene-2-hydroxyaniline and its related derivatives by O2 catalysed by [Co2L(μ-OH)] {H3L = 2,6-bis[(2-hydroxyphenyl)iminomethyl]-4-methylphenol} in DMF at 363 K was investigated. The oxidation products were the corresponding 2-substituted benzoxazoles. However, a side reaction leading to 2-aminophenoxazine-3-one via hydrolysis of the starting compound with water produced in the oxidation, followed by the oxidation of aminophenol, was established. If a dehydrating agent such as anhydrous Na2SO4 or 4 A molecular sieves was present in the reaction mixture the isolated product yields were above 87%. The fact that the reaction rate of the oxidation process in the presence of a radical scavenger was similar to that without suggests that it was a non-radical process. The initial oxidation rates depended linearly on the concentration of catalyst. The rates also depended linearly on the concentration of the organic substrate N-benzylidene-2-hydroxyaniline and O2 pressure when these variables were small ([substrate] 2 pressure 2 pressure the rate showed saturation behavior. These kinetic data could be satisfactorily accounted for by a mechanism with initial co-ordination of substrate to [Co2L(μ-OH)], followed by the co-ordination of O2 to the catalyst, then the rate limiting step of oxidation of substrate. The formation of the adduct between N-benzylidene-2-hydroxyaniline and catalyst at 298 K was characterized by UV-Vis spectroscopy. The variation of the initial rates among the organic substrates could be explained by stereoelectronic effects. Moreover, the influence of acetic acid which slowed the initial rate of oxidation and weak base (2,6-di-tert-butylpyridine) which had little effect on the rate could also be satisfactorily accounted for based on the acid-base properties of the proposed reaction intermediates.
- Chang, Shian Yuh,Cheng, Yee Hsing,Uang, Bing-Jium,Cheng, Cheu Pyeng
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- Mechanistic exploration of the palladium-catalyzed process for the synthesis of benzoxazoles and benzothiazoles
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A convenient one-pot palladium-catalyzed cascade process for the preparation of both benzoxazoles and benzothiazoles has been developed. While these reactions proceed to give similar compounds the mechanisms governing the processes are different as are the experimental conditions employed.
- Bochatay, Valentin N.,Boissarie, Patrick J.,Murphy, John A.,Suckling, Colin J.,Lang, Stuart
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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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- Iron-catalyzed 2-arylbenzoxazole formation from o-nitrophenols and benzylic alcohols
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The iron-catalyzed 2-arylbenzoxazole formation from o-nitrophenols and benzylic alcohols using hydrogen transfer is described. Various 2-arylbenzoxazoles were selectively obtained in good to excellent yields. The reaction tolerated a wide range of functionalities. The alcohol oxidation, nitro reduction, condensation, and dehydrogenation were realized in a cascade without external reducing reagent and oxidant.
- Wu, Mingyue,Hu, Xiong,Liu, Juan,Liao, Yunfeng,Deng, Guo-Jun
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- Gold nanoparticles supported on titanium dioxide: An efficient catalyst for highly selective synthesis of benzoxazoles and benzimidazoles
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A highly efficient and selective reaction for the synthesis of 2-substituted benzoxazoles and benzimidazoles catalyzed by Au/TiO2 has been developed via two hydrogen-transfer processes. This reaction has a good tolerance to air and water, a wide substrate scope, and represents a new avenue for practical C-N and C-O bond formation. More importantly, no additional additives, oxidants and reductants are required for the reaction and the catalyst can be recovered and reused readily. This journal is the Partner Organisations 2014.
- Tang, Lin,Guo, Xuefeng,Yang, Yu,Zha, Zhenggen,Wang, Zhiyong
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- Mechanistic evidence for a ring-opening pathway in the Pd-catalyzed direct arylation of benzoxazoles
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The direct Pd-catalyzed arylation of 5-substituted benzoxazoles, used as a mechanistic model for 1,3-azoles, was investigated experimentally and computationally. The results of the primary deuterium kinetic isotope effect, Hammett studies, and H/D exchange were shown to be inconsistent with the rate-limiting electrophilic or concerted palladation. A mechanism, proposed on the basis of kinetic and computational studies, includes generation of isocyanophenolate as the key step. The DFT calculations suggest that the overall catalytic cycle is facile and is largely controlled by the C-H acidity of the substrate. Copyright
- Sanchez, Rafael S.,Zhuravlev, Fedor A.
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- Tin(II) chloride-mediated synthesis of 2-substituted benzoxazoles
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2-Aminophenols react with an array of carboxylic acids in dioxane at 180° in the presence of tin(II) chloride to afford the corresponding 2-substituted benzoxazoles in good yields. The reaction is applicable to a wide range of alkyl, alkenyl, aryl carboxylic acids.
- Cho, Chan Sik,Kim, Dong Tak,Zhang, Jiao Qiang,Ho, Son-Lam,Kim, Tae-Jeong,Shim, Sang Chul
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- Cyanide as a powerful catalyst for facile preparation of 2-substituted benzoxazoles via aerobic oxidation
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A cyanide-catalyzed synthesis of 2-substituted benzoxazoles from Schiff bases via aerobic oxidation has been developed. The products from various Schiff bases were obtained in high yields in an open flask under ambient conditions without other external oxidants. We have also developed a simple one-step protocol for the synthesis of benzoxazoles from aminophenol and the corresponding aldehydes in the presence of cyanide without isolation of imine intermediates. Copyright
- Cho, Yeon Ho,Lee, Chun-Young,Ha, Deok-Chan,Cheon, Cheol-Hong
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- Synthesis of 2-Arylbenzoxazoles via the Palladium-Catalyzed Carbonylation and Condensation of Aromatic Halides and o-Aminophenols
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A new synthetic method is reported in which 2-arylbenzoxazoles can be prepared by palladium-catalyzed condensation of aryl halides with o-aminophenols followed by dehydrative cyclization.This method is tolerant of a wide variety of functional groups on either aromatic ring and gives good to excellent yields of products.An aliphatic vicinal amino alcohol gave a bis-acylated product as well as a chlorine-containing product with only a small amount of the desired 2-aryloxazole being formed.Methyl iodide and benzyl bromide gave only alkylated products.
- Perry, Robert J.,Wilson, B. David,Miller, Richard J.
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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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- 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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- 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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- Biomimetic oxidative coupling of benzylamines and 2-aminophenols: Synthesis of benzoxazoles
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Aerobic oxidation: In a biomimetic approach, a mixture of redox catalysts forms couples that effect the aerobic oxidation of a mixture of benzylamine and 2-aminophenol derivatives to give the corresponding benzoxazoles (see scheme). This biomimetic oxidation proceeds smoothly under mild conditions and the protocol can also be used for preparing benzimidazoles and benzothiazoles. Copyright
- Endo, Yoshinori,B?ckvall, Jan-E.
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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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- 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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- The palladium-catalyzed tandem decarboxylation, carbon-carbon triple bond oxidation and decarbonylative arylation of the benzoxazole C-H bond
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A palladium-catalyzed arylation of benzoxazole has been developed. This protocol involves the tandem decarboxylation and oxidation of a carbon-carbon triple bond followed by decarbonylative arylation of the benzoxazole C-H bond.
- Liu, Dongfang,Liu, Bin,Cheng, Jiang
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- A domino copper-catalyzed C-N and C-O cross-coupling for the conversion of primary amides into benzoxazoles
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Benzoxazoles can be efficiently prepared in a single step and in good yield from primary amides and o-dihalobenzenes using Cu catalysis. Starting from substituted o-bromochlorobenzenes this unusual domino reaction allows the regioselective formation of benzoxazoles.
- Altenhoff, Gereon,Glorius, Frank
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- Nano CuO-catalyzed C-H functionalization of 1,3-azoles with bromoarenes and bromoalkenes
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Copper oxide catalyzed direct C-H arylation and alkenylation of aromatic heterocycles using aryl and alkenyl bromides have been developed and have been applied to the C-H functionalization of a variety of 1,3-azoles like benzoxazole, benzothiazole, 1-methylbenzimidazole, and 1-methylimidazole, with moderate to excellent yields. The best performance has been achieved in the presence of PPh3 when average size of CuO nanoparticles is 6.5 nm. This catalyst can be recovered and reused without significant decrease in its catalytic activity.
- Zhang, Wu,Tian, Yujie,Zhao, Na,Wang, Yuanyuan,Li, Jia,Wang, Zhenghua
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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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- 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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- 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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- A simple and efficient one step synthesis of benzoxazoles and benzimidazoles from carboxylic acids
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Benzoxazoles or benzimidazoles can be rapidly and efficiently synthesized from a variety of carboxylic acids with 2-aminophenols or 1,2-phenylenediamines in one simple step, respectively. The use of commercially available PS-PPh3 resin combined with microwave heating delivered a variety of benzoxazoles and benzimidazoles in high yields and purities.
- Wang, Ying,Sarris, Kathy,Sauer, Daryl R.,Djuric, Stevan W.
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- Visible Light-Induced Copper-Catalyzed C—H Arylation of Benzoxazoles?
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A general method for visible light-induced copper-catalyzed arylation of sp2 C—H bonds of azoles has been developed. The method employs aryl halide as the coupling partner, lithium alkoxide as base. A variety of azoles including benzooxazole and benzothiazole can be arylated. Furthermore, electron-poor heterocycles such as thiophene possessing one electron-withdrawing group can also be arylated.
- Ma, Xiaodong,Zhang, Guozhu
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- 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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- Cu-Catalyzed Synthesis of Benzoxazole with Phenol and Cyclic Oxime
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A Cu-catalyzed straightforward synthesis of benzoxazoles from free phenols and cyclic oxime esters is reported. The mild reaction conditions tolerate various electron-withdrawing and electron-donating functional groups on both substrates, affording benzoxazoles in moderate to good yields. With this protocol, large-scale syntheses of Ezutromid and Flunoxaprofe in one or two steps are demonstrated. A catalytic mechanism, which includes Cu-catalyzed amination via inner-sphere electron transfer and consequent annulation, is proposed.
- Wang, Zheng-Hai,Wang, Dong-Hui
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p. 782 - 785
(2022/01/20)
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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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- 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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- Pd/Cu-Catalyzed C-H/C-H Cross Coupling of (Hetero)Arenes with Azoles through Arylsulfonium Intermediates
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A highly efficient method for the selective formal C-H/C-H cross-coupling of azoles and (hetero)arenes was established through arylsulfonium intermediates under transition-metal catalysis, which produced a variety of 2-(hetero)aryl azoles in good to excellent yields. Advantages of the reaction included mildness, a good functional group tolerance, a wide range of substrates, a high regio- and chemoselectivity, one-pot procedures, and the late-stage functionalization of complex molecules without the use of oxidants, offering a promising strategy for the transition-metal-catalyzed C-H arylation of azoles.
- Lin, Zeng-Hui,Tian, Ze-Yu,Zhang, Cheng-Pan
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supporting information
p. 4400 - 4405
(2021/06/27)
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- Liebeskind-Srogl-type cross-coupling reaction of azole-2-thiones with triarylbismuthines: Synthesis of 2-arylazoles
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Liebeskind-Srogl-type C(HetAr)–C(Ar) bond formation using trivalent organobismuth compounds as a new class of arylating reagents is described. The reaction of benzazole-2-thiones with triarylbismuthines in the presence of 10 mol% Pd(dba)2 and 2.0 equiv. Cu(OAc)2 at 80 °C affords 2-arylbenzothiazoles, benzoxazoles, and N-methyl benzimidazole in moderate-to-high yield. The reaction is sensitive to the electronic nature of triarylbismuthines: compounds bearing an electron-withdrawing group on the phenyl ring showed higher reactivity than those having an electron-donating group.
- Murata, Yuki,Terazoe, Aki,Kiba, Misato,Kitamura, Yuki,Matsumura, Mio,Yasuike, Shuji
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supporting information
(2020/07/03)
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- Oxidative NHC catalysis for base-free synthesis of benzoxazinones and benzoazoles by thermal activated NHCs precursor ionic liquid catalyst using air as oxidant
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A reusable thermal activated NHC precursor ionic liquid catalyst ([BMIm]2[WO4]) has been prepared and developed for the synthesis of nitrogen-containing heterocycles such as benzoxazinones and benzoazoles through imines activation. [BMIm]2[WO4] exhibited the good activity for the base-free condensation and oxidative NHC catalysis tandem under air atmosphere. The catalyst can be recovered and reused for at least five runs in gram scale synthesis without any decrease in catalytic activity. Furthermore, the control experiments demonstrated that the reaction involved formation of aromatic aldimines, NHC-catalyzed oxidative formation of imidoyl azoliums and intramolecular cyclization to generate the product.
- Guan, Jiali,Liu, Wei,Liu, Yuchen,Song, Zhibin,Tao, Duan-Jian,Yan, Jieying,Yuan, Jian-Jun,Zhou, Youkang
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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; 0103
(2019/01/21)
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- Iodine Promoted One-Pot Synthesis of 2-Aryl Benzoxazoles from Amidoximes via Oxidative Cyclization and Ring Contraction
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A molecular I2-promoted one-pot synthesis of 2-aryl benzoxazoles has been developed by using amidoximes rather than the limited 2-aminophenols or 2-haloamides as substrates. The amidoxime substrates provided unique and efficient strategies for converting readily available aniline and benzaldehyde precursors into valuable chemicals. This transformation proceeded smoothly under transition-metal-free conditions through a sequential oxidative cyclization and ring contraction, and provided a potential route for introducing certain groups at any site of the scaffold.
- Zhang, Yong,Ji, Min
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supporting information
p. 7506 - 7510
(2019/11/28)
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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 0042-0045
(2019/07/04)
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- Synthesis of benzoxazoles via the copper-catalyzed hydroamination of alkynones with 2-aminophenols
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We describe herein the synthetic method to benzoxazole derivatives via the copper-catalyzed hydroamination of alkynones with 2-aminophenols. The method produced a wide variety of functionalized benzoxazole derivatives in good yields. Preliminary mechanistic experiments revealed that the reaction would proceed through the copper-catalyzed hydroamination of alkynones and the sequential intramolecular cyclization of β-iminoketones/elimination of acetophenone promoted by the copper catalyst.
- Oshimoto, Kohei,Tsuji, Hiroaki,Kawatsura, Motoi
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p. 4225 - 4229
(2019/05/10)
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- Sulfur-Catalyzed Oxidative Coupling of Dibenzyl Disulfides with Amines: Access to Thioamides and Aza Heterocycles
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In the presence of catalytic amounts of elemental sulfur, dibenzyl disulfide/DMSO was found to be an excellent thiobenzoylating agent of amines to provide a wide range of thioamides. The reaction becomes autocatalytic when anilines substituted by an o-cyclizable group were used as nucleophile, leading to the corresponding 2-aryl aza heterocycles. (Figure presented.).
- Nguyen, Thanh Binh,Nguyen, Le Phuong Anh,Nguyen, Thi Thu Tram
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supporting information
p. 1787 - 1791
(2019/02/26)
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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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p. 3055 - 3062
(2018/08/01)
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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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- 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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- Environmental benign synthesis of novel double layered nano catalyst and their catalytic activity in synthesis of 2-substituted benzoxazoles
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Synthesis of Cu-Al hydrotalcite by co precipitation method is being described. Synthesized nano catalyst has been characterized by powder X-ray diffraction, scanning electron microscopy, FT-IR and thermogravimetric analyses which confirm hydrotalcite-like structure. Effect of molar concentration, catalyst loading, reaction time and catalytic activity have been investigated in the synthesis of benzoxazoles under solvent free conditions using 2-amino phenol and benzoyl chloride. The influence of the hydrotalcite and their different amounts on reactivity was studied. Catalyst can be recycle and used for further reaction without losing its activity.
- Gupta, Ruchi,Sahu, Pramod K.,Sahu, Praveen K.,Srivastava,Agarwal
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p. 119 - 123
(2017/01/25)
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- Base-Free Selective O-Arylation and Sequential [3,3]-Rearrangement of Amidoximes with Diaryliodonium Salts: Synthesis of 2-Substituted Benzoxazoles
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A variety of functionalized 2-substituted benzoxazoles can be prepared in good yields from amidoximes and diaryliodonium salts by selective O-arylation and sequential [3,3]-rearrangement under metal-free conditions. O-arylation of amidoximes was promoted by 3 ? molecule sieves in the absence of a base and a sequential TFA-mediated [3,3]-rearrangement was used to synthesize 2-substituted benzoxazoles. Both of the O-aryl products and rearrangement products were compatible with a broad range of sensitive functional groups such as ester, aldehyde, nitro, vinyl, amine, and amide groups in addition to halides. A bidentate N-ligand with double benzoxazoles was prepared at gram-scale in two steps. (Figure presented.).
- Shi, Wei-Min,Li, Xiao-Hua,Liang, Cui,Mo, Dong-Liang
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p. 4129 - 4135
(2017/12/15)
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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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- Oxidative Synthesis of Benzimidazoles, Quinoxalines, and Benzoxazoles from Primary Amines by ortho-Quinone Catalysis
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The bioinspired ortho-quinone catalysts have been applied to heterocycles synthesis. Without any metal cocatalysts, a sole ortho-quinone catalyst enables the oxidative synthesis of benzimidazoles, quinoxalines and benzoxazoles from primary amines in high yields under mild conditions with oxygen as the terminal oxidant.
- Zhang, Ruipu,Qin, Yan,Zhang, Long,Luo, Sanzhong
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supporting information
p. 5629 - 5632
(2017/10/25)
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- A 2 - substituted benzoxazole compound of preparation method (by machine translation)
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The invention discloses a method for preparing a 2-substituted benzoxazole compound, and belongs to the technical field of synthesis of benzoxazole compounds. According to the technical scheme, the method is characterized by comprising the steps that an aldehyde compound R1CHO and an ortho-aminophenol compound (please see the specification for the formula) are dissolved in solvent xylene or methylbenzene, and pre-reacting is conducted for one hour when the solvent is heated to be at the temperature of 120 DEG C; then the temperature is lowered to be an indoor temperature, catalyst copper acetylacetonate is added, and negative pressure suction is carried out in the oxygen atmosphere for reacting till TLC monitors that the reacting is complete; filtering is performed, and water and ethyl acetate are added in filter liquor to be extracted; an organic phase is dried through anhydrous sodium sulfate, column chromatography purification is carried out after the solvent is removed by steaming, and accordingly the 2-substituted benzoxazole compound (please see the specification for the formula) is obtained. According to the method, the aldehyde compound and the ortho-aminophenol compound are used as reacting raw materials, the copper acetylacetonate is used as a catalyst, oxygen is used as an oxidizing agent, no extra additives are needed, and a series of 2-substituted benzoxazole compounds are synthesized; operation is simple and practicable, the raw materials are cheap and easy to get, reaction efficiency is high and repeatability is good.
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Paragraph 0043; 0044
(2018/01/05)
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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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- 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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- An efficient magnetic copper ferrite nanoparticle: For one pot synthesis of 2-substituted benzoxazole via redox reactions
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A new, green and sustainable approach for the synthesis of 2-substituted benzoxazole by using a one pot redox cascade condensation reaction of benzyl amine and 2-nitro phenol, catalysed by Cu Ferrite NPs is reported. Cu Ferrite NPs are magnetically separable, air stable and can be recycled up to fifth cycle without a significant loss in catalytic activity. The catalyst is characterised by FEG-SEM, TEM, EDAX and XRD.
- Sarode, Sachin A.,Bhojane, Jeevan M.,Nagarkar, Jayashree M.
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supporting information
p. 206 - 210
(2015/02/02)
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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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- Copper-catalyzed synthesis of 2-arylbenzoxazoles from o-aminophenol derivatives with arylmethyl chlorides
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A facile and efficient synthesis of 2-arylbenzoxazoles via copper-catalyzed tandem condensation/oxidative reaction of o-aminophenol derivatives with arylmethyl chlorides was developed. Note that this reaction utilized arylmethyl chlorides as a new type of simple and cheap acyl sources and KNO3 as a readily available and low-cost benign oxidant.
- Zhang, Guodong,Wang, Peng,Yang, Fan,Wu, Yangjie
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supporting information
p. 57 - 63
(2015/02/02)
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- Synthesis of 2-substituted pyrimidines and benzoxazoles via a visible-light-driven organocatalytic aerobic oxidation: Enhancement of the reaction rate and selectivity by a base
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An efficient visible-light-driven photocatalytic oxidation of various 2-substituted dihydropyrimidines and phenolic imines has been achieved using an organic photocatalyst eosin Y bis(tetrabutyl ammonium salt) (TBA-eosin Y) and inexpensive oxidant molecular oxygen. With the aid of a base, significantly enhanced photoinduced electron transfer from substrates dihydropyrimidines or phenolic imines to the excited state of TBA-eosin Y has enabled the aerobic oxidation to yield 2-(methylthio)pyrimidines or 2-arylbenzoxazoles selectively. This journal is the Partner Organisations 2014.
- Wang, Lin,Ma, Zhi-Gang,Wei, Xiao-Jing,Meng, Qing-Yuan,Yang, Deng-Tao,Du, Shao-Fu,Chen, Zi-Fei,Wu, Li-Zhu,Liu, Qiang
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supporting information
p. 3752 - 3757
(2014/08/05)
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- C-H arylation of azaheterocycles: A direct ligand-free and Cu-catalyzed approach using diaryliodonium salts
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An efficient and high yielding Cu-catalyzed direct C-H arylation of azaheterocycles including oxadiazoles, thiadiazoles, benzoxazoles and benzothiazoles has been achieved by employing easily accessible diaryliodonium salts. the Partner Organisations 2014.
- Kumar, Dalip,Pilania, Meenakshi,Arun,Pooniya, Savita
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supporting information
p. 6340 - 6344
(2014/08/18)
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- Synthesis of 2-arylbenzoxazoles through oxidation of C-H bonds adjacent to oxygen atoms
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A practical and simple synthesis of benzoxazoles from easily available substrates was developed. The protocol is triggered by an iron-catalyzed tandem oxidative process from simple ether derivatives. A practical and simple synthesis of benzoxazoles from easily available substrates is developed. The protocol is triggered by an iron-catalyzed tandem oxidative process from simple ether derivatives. Copyright
- Gu, Lijun,Wang, Wei,Xiong, Yong,Huang, Xiangzhong,Li, Ganpeng
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p. 319 - 322
(2014/01/23)
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- Synthesis of 2-Arylbenzoxazoles through Oxidation of C-H Bonds Adjacent to Oxygen Atoms
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A practical and simple synthesis of benzoxazoles from easily available substrates was developed. The protocol is triggered by an iron-catalyzed tandem oxidative process from simple ether derivatives.
- Gu, Lijun,Wang, Wei,Xiong, Yong,Huang, Xiangzhong,Li, Ganpeng
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p. 319 - 322
(2015/10/05)
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- Application of nano SnO2 as a green and recyclable catalyst for the synthesis of 2-aryl or alkylbenzoxazole derivatives under ambient temperature
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Application of nano SnO2 as an efficient and benign catalyst has been explored for the synthesis of 2-aryl or alkylbenzoxazole derivatives via condensation reaction of aldehyde with 2-aminophenol. The reactions proceed under heterogeneous and mild conditions in ethanol at room temperature to provide 2-aryl or alkylbenzoxazoles in high yields.
- Vahdat, Seyed Mohammad,Raz, Shima Ghafouri,Baghery, Saeed
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p. 579 - 585
(2014/07/07)
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- Cyanide as a powerful catalyst for facile synthesis of benzofused heteroaromatic compounds via aerobic oxidation
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Highly efficient synthesis of benzofused heteroaromatic compounds via aerobic oxidation catalyzed by cyanide anion has been developed. The Schiff bases derived from 2-aminophenol and aldehydes provided the corresponding benzoxazoles in high yields in the presence of a catalytic amount of cyanide in an open flask under ambient conditions without the use of any external metal co-oxidants and bases. Furthermore, we have developed a catalytic sequential one-step protocol for the synthesis of benzoxazoles by adding a catalytic amount of NaCN to Schiff bases generated in situ from 2-aminophenol and aldehydes without the isolation of imine intermediates. This one-pot protocol was further extended to the synthesis of benzothiazoles from 2-aminothiophenol and aldehydes. A variety of aldehydes could be applied to this sequential one-pot protocol and the desired benzofused azole products were obtained in high yields.
- Cho, Yeon-Ho,Lee, Chun-Young,Cheon, Cheol-Hong
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p. 6565 - 6573
(2013/07/26)
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- Iron-catalyzed arylation of benzoazoles with aromatic aldehydes using oxygen as oxidant
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An iron-catalyzed arylation of azoles with aromatic aldehydes using oxygen as oxidant has been discovered. The reaction proceeded well for a range of different substrates under oxidative conditions. The Royal Society of Chemistry.
- Liu, Saiwen,Chen, Ru,Guo, Xiangyu,Yang, Huiqiong,Deng, Guojun,Li, Chao-Jun
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supporting information
p. 1577 - 1580
(2013/02/22)
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- Palladium-catalyzed direct arylation of benzoxazoles with unactivated simple arenes
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Using CuBr2 as an additive, the Pd-catalyzed intermolecular C-H-C-H cross-coupling between benzoxazoles and unactivated simple arenes has been developed. This protocol provides a straightforward approach for the biological activity of 2-arylbenzoxazole derivatives.
- Wu, Ge,Zhou, Jun,Zhang, Min,Hu, Peng,Su, Weiping
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supporting information
p. 8964 - 8966
(2012/11/14)
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