- Metal-Free [2+2+1] annulation of alkynes, nitriles and nitrogen atoms from iminoiodanes for synthesis of highly substituted imidazoles
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Boron trifluoride nitrile complexes promote oxidative [2+2+1] annulations of alkynes, nitriles and N-atoms from iminoiodanes to give the corresponding 2,4-disubstituted and 2,4,5-trisubstituted N-tosylimidazoles in moderate to good yields with high regios
- Saito, Akio,Kambara, Yui,Yagyu, Takuma,Noguchi, Keiichi,Yoshimura, Akira,Zhdankin, Viktor V.
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- A novel synthetic method of 2,4-disubstituted oxazoles using carboxylic acid-derived Bu2Sn[OC(O)R]2
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A novel synthetic method for the preparation of 2,4-disubstituted oxazoles was developed, entailing the reaction of dibutyltin diacylates Bu2Sn[OC(O)R]2 with 1-substituted acetylenes and TMSN3 to afford a range of 2,4-disu
- Yoneyama, Hiroki,Oka, Naoki,Usami, Yoshihide,Harusawa, Shinya
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supporting information
(2020/05/21)
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- Hypervalent iodane mediated reactions of: N -acetyl enamines for the synthesis of oxazoles and imidazoles
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A hypervalent iodane reagent used for the intramolecular cyclization of N-acetyl enamines and intermolecular cyclocondensation of enamines and nitriles was investigated. The reaction was performed under mild conditions and gave oxazoles and imidazoles, respectively, in moderate to excellent yields. This transformation exhibits good reactivity, selectivity and functional group tolerance. The selectivity of the intra- or intermolecular reaction is dependent on the structure of N-acetyl enamines.
- Xu, Kang,Yang, Ruiqi,Yang, Shuang,Jiang, Cheng,Ding, Zhenhua
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p. 8977 - 8981
(2019/10/28)
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- PdII-Catalyzed Regio- and Enantioselective Oxidative C?H/C?H Cross-Coupling Reaction between Ferrocenes and Azoles
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Asymmetric C?H bond functionalization reaction is one of the most efficient and straightforward methods for the synthesis of optically active molecules. Herein we disclose an asymmetric C?H/C?H cross-coupling reaction of ferrocenes with azoles such as oxazoles and thiazoles. Palladium(II)/monoprotected amino acid (MPAA) catalytic system which exhibits excellent reactivity and regioselectivity for oxazoles and thiazoles. This method offers a powerful strategy for constructing planar chiral ferrocenes. Mechanistic studies suggest that the C?H bond cleavage of azoles is likely proceeding through a SEAr process and may not be a turnover limiting step.
- Cai, Zhong-Jian,Liu, Chen-Xu,Gu, Qing,Zheng, Chao,You, Shu-Li
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supporting information
p. 2149 - 2153
(2019/01/24)
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- Lewis acid-mediated defluorinative [3+2] cycloaddition/aromatization cascade of 2,2-difluoroethanol systems with nitriles
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The properties of C?F bonds, including high thermal and chemical stability, make derivatization of organic fluorine-containing compounds by the activation of the C?F bond and subsequent functionalization quite challenging. We herein report a Lewis acid-mediated defluorinative cycloaddition/aromatization cascade of 2,2-difluoroethanols with nitriles as a novel synthetic method for the preparation of 2,4,5-trisubstituted oxazoles. This reaction, which involves cleavage of two C?F bonds and the consecutive formation of C?O and C?N bonds in a one-pot fashion, features a broad substrate scope and moderate to high reaction yields. Mechanistic studies revealed that the reaction is initiated by the Lewis acid-mediated ring closure of the 2,2-difluoroethanol to produce the fluoroepoxide intermediate. (Figure presented.).
- Hsieh, Min-Tsang,Lee, Kuo-Hsiung,Kuo, Sheng-Chu,Lin, Hui-Chang
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p. 1605 - 1610
(2018/03/05)
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- Development of Imino-λ3-iodanes with Improved Reactivity for Metal-Free [2+2+1] Cycloaddition-Type Reactions
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Aiming at the enhancement of electrophilicity of imino-λ3-iodanes, we have developed (tosylimino)pentafluorophenyl-λ3-iodane, which shows superior reactivity compared to the commonly used (tosylimino)phenyl-λ3-iodane in the [2+2+1]-type synthesis of imidazoles. (Figure presented.).
- Baba, Takafumi,Takahashi, Shunsuke,Kambara, Yui,Yoshimura, Akira,Nemykin, Victor N.,Zhdankin, Viktor V.,Saito, Akio
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supporting information
p. 3860 - 3864
(2017/10/09)
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- Iodine(III)-Catalyzed Formal [2 + 2 + 1] Cycloaddition Reaction for Metal-Free Construction of Oxazoles
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The iodine(III) catalyst, in situ generated from iodoarene as a precatalyst with m-CPBA and Tf2NH, promoted the metal-free [2 + 2 + 1] cycloaddition-type reactions of alkynes, nitriles, and oxygen atoms for the regioselective formations of 2,4-disubstituted and 2,4,5-trisubstituted oxazole. A first example of iodine catalysis for multicomponent reactions is represented.
- Yagyu, Takuma,Takemoto, Yusuke,Yoshimura, Akira,Zhdankin, Viktor V.,Saito, Akio
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supporting information
p. 2506 - 2509
(2017/05/24)
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- Metal-free syntheses of oxazoles and their analogues based on λ3-iodane-mediated cycloisomerization/functionalization reactions or [2+2+1] cycloaddition type reactions
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As a metal-free construction of oxazoles and furans concomitant with the introduction of oxygen functional groups or fluorine atoms into the side chains, we have developed λ3-iodane-mediated cycloisomerization/functionalization reactions of propargyl compounds. In these reactions, aryl- λ3-iodane ArI(X)Y works not only as a donor of heteroatomic functional groups but also as an activator of carbon-carbon triple bonds. Therefore, this methodology is not required any transition metal catalysts, which are frequently used in previous methods. Furthermore, this methodology can be extended to λ3-iodane-mediated [2+2+1] cycloaddition type reactions of alkynes, nitriles and heteroatoms for metal-free formation of oxazoles and imidazoles.
- Saito, Akio
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- Synthesis of 2,4- and 2,4,5-substituted oxazoles via a silver triflate mediated cyclization
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2,4- and 2,4,5-substituted oxazoles were prepared from a broad range of bromo-ketones and amides in high yield and purity.
- Bailey, Jessica L.,Sudini, Ravinder R.
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p. 3674 - 3677
(2014/06/23)
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- Copper-catalyzed direct synthesis of iodoenamides from ketoximes
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Iodide in copper's pathway: A new, efficient, and practical copper-catalyzed synthesis of Z-iodoenamides from readily available ketoximes has been developed (see scheme). The reaction was believed to proceed through a single-electron-transfer pathway. The corresponding Z-iodoenamides have been applied to the synthesis of substituted oxazoles, dienes, β-phenoxyl enamides, eneynes, β-acylenamides, and pyrroles (DCE=1,2-dichloroethane). Copyright
- Liang, Hao,Ren, Zhi-Hui,Wang, Yao-Yu,Guan, Zheng-Hui
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p. 9789 - 9794
(2013/08/23)
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- Metal-free [2 + 2 + 1] annulation of alkynes, nitriles, and oxygen atoms: Iodine(III)-mediated synthesis of highly substituted oxazoles
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The metal-free [2 + 2 + 1] annulation of alkynes, nitriles, and O-atoms for the regioselective assembly of 2,4-disubstituted and 2,4,5-trisubstituted oxazole compounds has been achieved by the use of PhIO with TfOH or Tf 2NH. The present reaction could be applied to a facile synthesis of an anti-inflammatory drug.
- Saito, Akio,Taniguchi, Akihiro,Kambara, Yui,Hanzawa, Yuji
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supporting information
p. 2672 - 2675
(2013/07/19)
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- Synthesis of oxazoles from enamides via phenyliodine diacetate-mediated intramolecular oxidative cyclization
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A group of functionalized oxazoles were synthesized in moderate to good yields from enamides via phenyliodine diacetate (PIDA)-mediated intramolecular cyclization. The main advantageous features of the present method include its broad substrate scope and the heavy-metal-free characteristic of the oxidative carbon-oxygen bond formation process.
- Zheng, Yunhui,Li, Xuming,Ren, Chengfeng,Zhang-Negrerie, Daisy,Du, Yunfei,Zhao, Kang
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p. 10353 - 10361
(2013/01/15)
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- A novel and efficient one pot synthesis of 2,4-disubstituted thiazoles and oxazoles using phenyltrimethylammoniumtribromide in ionic liquid
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A novel and efficient one-pot procedure has been described for synthesis of 2,4-disubstituted thiazoles and oxazoles from substituted ketones using phenyltrimethylammoniumtribromide as in situ brominating agent followed by reaction with thioamide/thiourea and amides/ureas, respectively in [bmim][BF4] ionicliquid. The advantages of the procedure include avoiding the handling of lacrymetric compounds, hazardous and toxic organic solvents along with good to excellent yield of the products.
- Muthyala, Manoj Kumar,Kumar, Anil
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p. 959 - 964
(2012/10/29)
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- A domino copper-catalyzed C-N and C-O cross-coupling for the conversion of primary amides into oxazoles
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A variety of oxazoles can efficiently be prepared, in a single step and in good yield, from primary amides and 1,2-dihaloalkenes using copper-catalysis. This new method allows the regioselective formation of a range of substituted oxazoles. The required 1,2-dihaloalkenes can prepared by simple treatment of alkynes with elemental bromine or iodine. Georg Thieme Verlag Stuttgart.
- Schuh, Kerstin,Glorius, Frank
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p. 2297 - 2306
(2008/02/13)
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- Efficient synthesis of multi-substituted oxazoles under solvent-free microwave irradiation
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A new and efficient method for the synthesis of multi-substituted oxazoles from various carbonyl compounds has been developed using sequential treatment of carbonyl compounds with HDNIB and amides such as acetamide or benzamide under solvent-free microwave irradiation conditions.
- Lee, Jong Chan,Choi, Hyun Jung,Lee, Yong Chan
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p. 123 - 125
(2007/10/03)
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- Facile synthesis of oxazoles starting from ketones
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A new and efficient method for the preparation of 2,4- and 2,4,5-substituted oxazoles is described which is based upon the reaction of α-sulfonyloxy ketone intermediates with acetamide or benzamide.
- Lee, Jong Chan,Kim, Sehyun,Lee, Yong Chan
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p. 1611 - 1614
(2007/10/03)
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- Substituted oxazole benzenesulfonamides as potent human β3 adrenergic receptor agonists
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As a part of our investigation into the development of orally bioavailable β3 adrenergic receptor agonists, we have identified a series of substituted oxazole derivatives that are potent β3 agonists with excellent selectivity against other β receptors. Several of these compounds showed excellent oral bioavailability in dogs. One example, cyclopentylethyloxazole 5f is a potent β3 agonist (EC50 = 14 nM, 84% activation) with 340-fold and 160-fold selectivity over β1 and β2 receptors, respectively, and has 38% oral bioavailability in dogs. (C) 2000 Elsevier Science Ltd. All rights reserved.
- Ok,Reigle,Candelore,Cascieri,Colwell,Deng,Feeney,Forrest,Hom,MacIntyre,Strader,Tota,Wang,Wyvratt,Fisher,Weber
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p. 1531 - 1534
(2007/10/03)
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- High-temperature rearrangements of 2-acylisoxazol-5(2H)-ones and related oxazoles
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2-Acyl-3-arylisoxazol-5(2H)-ones give 2-alkyl(aryl)-4-aryloxazoles in good yields at 540°C under flash vacuum pyrolysis conditions, but at higher temperatures the expected oxazoles are accompanied by increasing amounts of isomeric 2,5-disubstituted oxazoles, as well as anilides and decomposition products of the 2,4-disubstituted oxazole. The rearrangement mechanisms have been studied by the use of 13C labelled substrates and p-substituted 3-arylisoxazolones. The 2,5-disubstituted oxazoles are considered to arise from 1H-azirines, and the anilides from the nitrone ketene isomer of the acylisoxazolone.
- Clark, Adrian D.,Ha, Uyen T.,Prager, Rolf H.,Smith, Jason A.
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p. 1029 - 1033
(2007/10/03)
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- Convenient syntheses of 2-alkyl(Aryl)-4,5-diphenyloxazoles and 2-alkyl(Aryl)-4-phepyloxazoles
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The synthetic methods to prepare 2-alkyl(aryl)-4,5-diphenyloxazoles and 2-alkyl(aryl)-4-phenyloxazoles were improved on the basis of a mechanistic study of oxazole formation from α-hydroxy ketones (carboxylic esters of benzoin and phenacyl alcohols). By these methods, seven trisubstituted oxazoles and twelve disubstituted oxazoles of the title compounds were prepared.
- Pei, Weiwei,Li, Shaohui,Nie, Xiaoping,Li, Yiwei,Pei, Jian,Chen, Bingzi,Wu, Jie,Ye, Xiulin
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p. 1298 - 1304
(2007/10/03)
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- Chemistry of 5-oxodihydroisoxazoles. Part 18. Synthesis of oxazoles by the photolysis and pyrolysis of 2-acyl-5-oxo-2,5-dihydroisoxazoles
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N-Acylisoxazol-5-ones lose carbon dioxide under photochemical and thermal conditions affording iminocarbenes which undergo intramolecular cyclisation through the oxygen of the acyl group to give oxazoles. Under photochemical conditions those acylisoxazolones with electron withdrawing groups at C-4 usually give high yields of oxazoles, while those with electron donating groups at C-4 give only poor yields: the reverse is observed under thermal conditions.
- Prager, Rolf H.,Smith, Jason A.,Weber, Ben,Williams, Craig M.
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p. 2665 - 2672
(2007/10/03)
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- The synthesis of oxazoles by thermolysis or photolysis of 2-acylisoxazol-5-ones
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N-acylisoxazol-5-ones are converted into the corresponding 2-substituted oxazoles by photolysis at 300 or 254 nm, or by flash vacuum pyrolysis. The former procedure is favoured for isoxazolones with electron withdrawing groups at C-4, and pyrolysis for all others.
- Ang, Kiah H.,Prager, Rolf H.,Smith, Jason A.,Weber, Ben,Williams, Craig M.
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p. 675 - 678
(2007/10/02)
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- Substituted Oxazoles: Synthesis via Lithio Intermediates
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Reactions of 2-α-, 2-, 4-, and 5-lithiooxazoles are used to prepare various substituted derivatives.Previously unrecognized time dependence for the reaction of a 2-lithiooxazole with benzaldhyde is described, and a rationale for this behavior is offered.Competitive reactions occur when the readily available 2,5-diphenyloxazole is treated with n-butyllithium.Deprotonation of the ortho position of the 2-phenyl group and addition of n-butyl to the 2-position of the oxazole compete with the desired 4-lithiation.The use of sec-butyllithium/catalytic lithium tetramethylpiperidide allows preferential formation of 4-lithio-2,5-diphenyloxazole.This intermediate has been converted to the 4-bromo, -methyl, -hydroxybenzyl, -benzoyl, and -trialkylsilyl derivatives.Lithiation of 2,4-diphenyloxazole and subsequent trimethylsilylation occur readily at the 5-position.Deprotonation of 2-alkyloxazoles occurs at the α-carbon in preference to ring sites.Further reaction of an α-phenyl-2-oxazolemethanol methoxymethyl ether with base and acetyl chloride leads to an acyloin derivative.Chromic acid oxidation is used to prepare both 2- and 4-benzoyloxazoles.The formation of an 2-ethoxyoxazole from 2-oxazolone vis Meerwein salt chemistry is described.
- Whitney, Scott E.,Rickborn, Bruce
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p. 3058 - 3063
(2007/10/02)
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