- Photocyclization of o-Nitrophenyl Alkyl Ethers
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o-Nitrophenyl alkyl ethers 1a, 1b, and 1c undergo photocyclization to give benzoxazoles 2a, 2b, and 2c, respectively.
- Oguchi, Shoshichi,Torizuka, Hiroshi
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Read Online
- The dilemma between acid and base catalysis in the synthesis of benzimidazole from: O -phenylenediamine and carbon dioxide
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The tandem synthesis of benzimidazole and other azoles can be achived by the N-formylation of ortho-substituted anilines followed by a cyclization reaction. However, CO2-based N-formylations with hydrosilane reducing agents are base catalyzed whereas the cyclization reaction is acid catalyzed. The mismatch in catalytic conditions means that only one of the steps can be catalyzed in a single pot reaction. While the N-formylation reaction is frequently the target of catalyst development, the cyclization reaction requires comparably much harsher reaction conditions. Identification of these difficulties lead us to the development of a one-pot, two-step synthesis of benzimidazole under mild reaction conditions employing acid catalysts.
- Hulla, Martin,Nussbaum, Simon,Bonnin, Alexy R.,Dyson, Paul J.
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Read Online
- A substituent- And temperature-controllable NHC-derived zwitterionic catalyst enables CO2upgrading for high-efficiency construction of formamides and benzimidazoles
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Chemocatalytic upgrading of the greenhouse gas CO2 to valuable chemicals and biofuels has attracted broad attention in recent years. Among the reported approaches, N-formylation of CO2 with an amine is of great significance due to its versatility in the construction of N-containing linear and cyclic skeletons. Herein, a stable N-heterocyclic carbene-carboxyl adduct (NHC-CO2) was facilely prepared and could be used as a recyclable zwitterionic catalyst for efficient CO2 reductive upgrading via either N-formylation or further coupling with cyclization under mild conditions (25 °C, 1 atm CO2) using hydrosilane as a hydrogen source. More than 30 different alkyl and aromatic amines could be transformed into the corresponding formamides or benzimidazoles with remarkable yields (74%-98%). The electronic effect of the introduced substituent on NHC-CO2 was found to evidently affect the thermostability and nucleophilicity of the zwitterionic catalyst, which is directly correlated with its catalytic activity. Moreover, NHC-CO2 could supply CO2 by in situ decarboxylation at a specific temperature that is dependent on the introduced substituent type. Experimental and computational studies showed that the carboxyl species on NHC-CO2 was not only a nucleophilic center, but also a C1 source which rapidly captures or substitutes ambient CO2 during hydrosilylation. In addition, a simple and green conceptual process was designed for the product purification and catalyst recycling, with a good feasibility for small-scale production.
- Li, Hu,Li, Zhengyi,Wu, Hongguo,Yang, Song,Yu, Zhaozhuo,Zhang, Lilong,Zhu, Kaixun
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supporting information
p. 5759 - 5765
(2021/08/23)
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- Synthesis of isocyanides by reacting primary amines with difluorocarbene
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A general, convenient, and friendly route for preparing a versatile building block of isocyanides from primary amines is developed. Difluorocarbene, generated in situ from decarboxylation of chlorodifluoroacetate, reacts efficiently with primary amines to produce isocyanides. Various primary amines are well tolerated, including aryl, heteroaryl, benzyl, and alkyl amines, as well as amine residues in amino acids and peptides. Late-stage functionalization of biologically active amines is demonstrated, showing its practical capacity in drug design and peptide modification.
- Si, Yi-Xin,Zhu, Peng-Fei,Zhang, Song-Lin
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supporting information
p. 9086 - 9090
(2020/11/30)
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- Endogenous X-C=O species enable catalyst-free formylation prerequisite for CO2reductive upgrading
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CO2, the main component of greenhouse gas, is currently developed as a promising surrogate of carbon feedstock. Among various conversion routes, CO2undergoing catalytic reduction can furnish hydrogen/energy carriers and value-added chemicals, while specific metal-containing catalysts or organocatalysts are often prerequisite for smooth proceeding of the involved reaction processes. In this work, both formic acid and N-containing benzoheterocyclic compounds (including various benzimidazoles, benzothiazole, and benzoxazole) along with silanols could be synthesized with high yields (>90%) from catalyst-free reductive upgrading of CO2under mild conditions (50 °C). The endogenous X-CO species, derived from the N-methyl-substituted amide-based solvent [Me2N-C(O)-R], especially PolarClean, and O-formyl group [O-C(O)-H] of in situ formed silyl formate, were found to play a prominent promotional role in the activation of the used hydrosilane for reductive CO2insertion, as demonstrated by density functional theory (DFT) calculations and isotopic labeling experiments. Moreover, reaction mechanisms and condition-based sensitivity assessment were also delineated.
- Dai, Wenshuai,Li, Hu,Saravanamurugan, Shunmugavel,Wu, Hongguo,Yang, Song
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p. 5822 - 5832
(2020/10/21)
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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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supporting information
p. 1299 - 1303
(2020/08/05)
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- Organophosphine-free copper-catalyzed isothiocyanation of amines with sodium bromodifluoroacetate and sulfur
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A copper-catalyzed isothiocyanation of amines with sodium bromodifluoroacetate and sulfur in the absence of organophosphine has been established. This approach represents a simple and efficient one-pot synthesis of isothiocyanates, and features excellent functional group tolerance and the use of a cheap, safe and odorless sulfur source. Moreover, this process could directly provide isothiocyanate analogous bioactive molecules, thiocarbonyl-containing pesticides and facile construction of benzoxazole and benzimidazole frames.
- Feng, Wei,Zhang, Xing-Guo
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supporting information
p. 1144 - 1147
(2019/01/28)
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- Visible Light-Promoted Beckmann Rearrangements: Separating Sequential Photochemical and Thermal Phenomena in a Continuous Flow Reactor
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The Beckmann rearrangement of oximes to amides typically requires strong acids or highly reactive, hazardous electrophiles and/or elevated temperatures to proceed. A very attractive alternative is the in situ generation of Vilsmeier–Haack reagents, by means of photoredox catalysis, as promoters for the thermal Beckmann rearrangement. Investigation of the reaction parameters for this light-induced method using a one-pot strategy has shown that the reaction is limited by the different temperatures required for each of the two sequential steps. Using a continuous flow reactor, the photochemical and thermal processes have been separated by integrating a flow photoreactor unit at low temperature for the electrophile generation with a second reactor unit, at high temperature, where the rearrangement takes place. This strategy has enabled excellent conversions and yields for a diverse set of oximes, minimizing the formation of side products obtained with the original one-pot method.
- Chen, Yuesu,Cantillo, David,Kappe, C. Oliver
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supporting information
p. 2163 - 2171
(2019/03/14)
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- Catalytic synthesis of benzimidazoles and organic carbamates using a polymer supported zinc catalyst through CO2 fixation
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Utilization of carbon dioxide in chemical fixation for synthesis of fine chemicals like benzimidazoles, organic carbamates, etc. is in high demand in recent years as carbon dioxide is a cost effective, sustainable, and green renewable C1 source. In this article we present the design and synthesis of an organically modified polystyrene bound heterogeneous [PS-Zn(ii)-SALTETA] catalyst. The catalyst has been characterized thoroughly by Fourier transform infrared spectroscopy, atomic absorption spectroscopy, thermo gravimetric analysis, PXRD, SEM and EDAX studies. The catalyst was used for cyclization of o-phenylenediamines through insertion of carbon dioxide in order to produce benzimidazoles in the presence of dimethylamine borane (DMAB). The developed catalytic procedure is sustainable, economical and efficient owing to the utilization of ethanol/water as a biodegradable and environment friendly solvent system. Besides benzimidazole production the catalyst was also very active for manufacture of organic carbamates from anilines and n-butyl bromide under atmospheric CO2 pressure under solvent free conditions at room temperature and the catalytic protocol showed outstanding functional group tolerance. Moreover the catalyst is highly recyclable and reusable.
- Biswas, Imdadul Haque,Biswas, Surajit,Islam, Md Sarikul,Riyajuddin, Sk,Sarkar, Priyanka,Ghosh, Kaushik,Islam, Sk Manirul
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p. 14643 - 14652
(2019/09/30)
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- Cobalt-catalyzed synthesis of N-containing heterocycles: Via cyclization of ortho -substituted anilines with CO2/H2
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The CO2-involved synthesis of chemicals is of great significance from the green and sustainable chemistry viewpoint. Herein, we report a non-noble metal catalytic system composed of CoF2, CsF and P(CH2CH2PPh2)3 (denoted as PP3) for the synthesis of N-containing heterocycles from ortho-substituted anilines and CO2/H2. Mechanism investigation indicates that [Co(PP3)H(CO2)]+ is a catalytically active intermediate under working conditions; and CsF plays important roles in activating ortho-substituted anilines via hydrogen bond interactions, thus promoting the formation of the final products. This catalytic system is highly efficient, and allows a wide scope of ortho-substituted anilines, together with excellent functional group tolerance, affording various N-containing heterocycles in good to excellent yields.
- Ke, Zhengang,Yu, Bo,Wang, Huan,Xiang, Junfeng,Han, Juanjuan,Wu, Yunyan,Liu, Zhenghui,Yang, Peng,Liu, Zhimin
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supporting information
p. 1695 - 1701
(2019/04/10)
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- Cu-Catalyzed Direct C-P Bond Formation through Dehydrogenative Cross-Coupling Reactions between Azoles and Dialkyl Phosphites
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A direct dehydrogenative cross-coupling of azoles [C(sp2)-H] with dialkyl phosphites [P(O)-H] to access 2-phosphonated azoles using Cu(I)/Cu(II) as catalyst and K2S2O8/di-tert-butylperoxide as oxidant has been achieved. A remarkable advantage over reported procedures includes that oxazoles, imidazoles, benz(ox/othi/imid)azoles, and indole are found to react under optimized reaction conditions to provide corresponding adducts in high yields. The mechanistic insight of cross-coupling was obtained by deuterium kinetic isotope effect studies.
- Hore, Soumyadip,Srivastava, Abhijeet,Singh, Ravi P.
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p. 6868 - 6878
(2019/06/14)
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- Flow hydrodediazoniation of aromatic heterocycles
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Continuous flow processing was applied for the rapid replacement of an aromatic amino group with a hydride. The approach was applied to a range of aromatic heterocycles, confirming the wide scope and substituent-tolerance of the processes. Flow equipment was utilized and the process optimised to overcome the problematically-unstable intermediates that have restricted yields in previous studies relying on batch procedures. Various common organic solvents were investigated as potential hydride sources. The approach has allowed key structures, such as amino-pyrazoles and aminopyridines, to be deaminated in good yield using a purely organic-soluble system.
- R?der, Liesa,Nicholls, Alexander J.,Baxendale, Ian R.
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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 0013
(2019/03/08)
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- Oxalic/malonic acids as carbon building blocks for benzazole, quinazoline and quinazolinone synthesis
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An oxidant, base and metal free methodology has been developed for the synthesis of various 2-substituted and non-substituted benzazoles, quinazolines and quinazolinones using oxalic/malonic acids as an in situ carbon source. This methodology is applicable for a wide range of substituted o-phenylenediamine, o-aminothiophenol, o-aminophenol and o-aminobenzamide containing various functional groups and provides good to excellent yields of the corresponding product. Furthermore an easy workup procedure, high yield and easy isolation of products are key features of this methodology. The developed protocol is also applicable for the gram scale synthesis of benzimidazoles.
- Sharma, Saurabh,Bhattacherjee, Dhananjay,Das, Pralay
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supporting information
p. 1337 - 1342
(2018/03/06)
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- Lewis Base Promoted Reduction of CO2 with BH3NH3 into Boryl Formates: CO2 as a Carbon Source in Organic Synthesis Under Mild Conditions
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Lewis base promoted selective reduction of CO2 into boryl formates by using BH3NH3 as a reductant under mild conditions has been reported. The boryl formates, generated in situ, were shown to be reactive and versatile sources of formyl compounds to create new C–N, C–O, and C–C bonds. The reactivity of the boryl formates to yield formic acid, formamides, formates, secondary alcohols, and benzoheterocyclic rings was investigated.
- Zhang, Bo,Du, Gaixia,Hang, Wei,Wang, Sheng,Xi, Chanjuan
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supporting information
p. 1739 - 1743
(2018/04/24)
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- Ru@PsIL-Catalyzed Synthesis of N-Formamides and Benzimidazole by using Carbon Dioxide and Dimethylamine Borane
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This work reports the synthesis and characterization of ruthenium nanoparticles (Ru NPs) supported on polymeric ionic liquids (PILs). This catalyst shows high catalytic activity towards the N-formylation of amines and synthesis of benzimidazoles from 1,2-diamines and carbon dioxide (CO2) by reductive dehydrogenation of dimethylamine borane. This methodology shows excellent functional group tolerance with broad substrate scope towards the synthesis of N-formamides and benzimidazoles. Interestingly, this protocol also provides the tandem reduction of 2-nitroamines and CO2 to synthesize benzimidazoles. It was proposed that the ionic liquid phase of the polymer plays pivotal roles such as assisting the stabilization of nanoparticles electrostatically, providing an ionic environment, and controlling the easy access of the substrates/reagents to the active sites. The developed methodology utilizes CO2 as a C1 source and water/ethanol as a green solvent system. Additionally, the catalyst was found to be recyclable in nature and shows five consecutive recycling runs without significant loss in its activity.
- Saptal, Vitthal B.,Sasaki, Takehiko,Bhanage, Bhalchandra M.
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p. 2593 - 2600
(2018/04/30)
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- Nanoporous TiO2 containing an ionic liquid bridge as an efficient and reusable catalyst for the synthesis of: N, N ′-diarylformamidines, benzoxazoles, benzothiazoles and benzimidazoles
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In this work, a green and efficient procedure is reported for the preparation of N,N'-diarylformamidines, benzoxazoles, benzothiazoles, and benzimidazoles using nanoporous TiO2 containing an ionic liquid bridge. This reagent is prepared via the modification of nanoporous TiO2 with bis-3-(trimethoxysilylpropyl)-ammonium hydrogen sulfate (TiO2-[bip]-NH2+ HSO4-). The procedure gave the products in excellent yields in very short reaction times under solvent-free conditions. The reusability of the catalyst is the other important feature of the reported method.
- Mazloumi,Shirini,Goli-Jolodar,Seddighi
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p. 5742 - 5752
(2018/04/23)
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- Atmospheric CO2 promoted synthesis of N-containing heterocycles over B(C6F5)3 catalyst
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B(C6F5)3 combined with atmospheric CO2 was found to be highly effective for the cyclization of ortho-substituted aniline derivatives with N,N-dimethylformamide (DMF), and a series of N-containing heterocycles including benzothiazoles, benzimidazoles, quinazolinone and benzoxazole were obtained in good to excellent yields.
- Gao, Xiang,Yu, Bo,Mei, Qingqing,Yang, Zhenzhen,Zhao, Yanfei,Zhang, Hongye,Hao, Leiduan,Liu, Zhimin
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p. 8282 - 8287
(2016/10/11)
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- Biomass-derived γ-valerolactone as an efficient solvent and catalyst for the transformation of CO2 to formamides
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Efficient conversion of carbon dioxide (CO2) into valuable chemicals is a very attractive topic. Herein, we conducted the first work on the utilization of biomass-derived γ-valerolactone (GVL) as the solvent and catalyst for transformation of CO2 with various primary and secondary amines in the presence of phenylsilane (PhSiH3), and the corresponding desired formamides were produced with high yields without any additional catalyst. Systematic studies indicated that the lactone structure of GVL played a key role in the formation of the active silyl formates and the activation of N-H bonds in amines, thus leading to the excellent performance of GVL for the catalytic reactions.
- Song, Jinliang,Zhou, Baowen,Liu, Huizhen,Xie, Chao,Meng, Qinglei,Zhang, Zhanrong,Han, Buxing
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supporting information
p. 3956 - 3961
(2016/07/21)
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- Ag@TiO2 nanocomposite; Synthesis, characterization and its application as a novel and recyclable catalyst for the one-pot synthesis of benzoxazole derivatives in aqueous media
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In the present study, we use a Ag@TiO2 nanocomposite for the efficient synthesis of benzoxazole derivatives via the one-pot condensation of 2-aminophenol and several aromatic aldehydes or orthoesters or carboxylic acids or amides or acyl chlorides in water at room temperature. In all situations the preferred products were synthesized with excellent yields. The short reaction times, high yields, safety and mild conditions, simplicity, non-toxicity and easy workup are the main merits of this protocol.
- Maleki, Behrooz,Baghayeri, Mehdi,Vahdat, Seyed Mohammad,Mohammadzadeh, Abbas,Akhoondi, Somaieh
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p. 46545 - 46551
(2015/06/16)
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- N-Substituted Formamides as C1-Sources for the Synthesis of Benzimidazole and Benzothiazole Derivatives by Using Zinc Catalysts
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An efficient and convenient one-pot protocol has been developed for the synthesis of a variety of benzimidazole, benzoxazole, and benzothiazole derivatives. This novel approach uses various o-phenylenediamines and N-substituted formamides (C1 sources) in a zinc-catalyzed cyclization in the presence of poly(methylhydrosiloxane) to afford the corresponding derivatives as sole products in moderate to excellent yields.
- Nale, Deepak B.,Bhanage, Bhalchandra M.
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p. 2835 - 2842
(2015/12/18)
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- Method For Preparing Nitrogen Compounds
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The present invention relates to a method for preparing nitrogen compounds using carbon dioxide, and to the use of the method in the production of vitamins, pharmaceutical products, adhesives, acrylic fibres, synthetic leathers, pesticides, herbicides, antifungal agents and fertilisers. The invention also relates to a method for producing vitamins, pharmaceutical products, adhesives, acrylic fibres, synthetic leathers, pesticides, herbicides, antifungal agents and fertilisers, which includes a step of preparing nitrogen compounds using the method of the invention. The invention further relates to a method for preparing labelled nitrogen compounds using carbon dioxide and to the uses thereof.
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Paragraph 0.192; 0193
(2015/06/03)
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- Facile synthesis of benzimidazole, benzoxazole, and benzothiazole derivatives catalyzed by sulfonated rice husk ash (RHA-SO3H) as an efficient solid acid catalyst
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A mild, simple, and efficient solvent-free method, with sulfonated rice husk ash as solid acid catalyst, has been developed for preparation of benzimidazole, benzoxazole, and benzothiazole derivatives. The products are obtained in good to high yields after very short reaction times, and the catalyst can be reused five times without loss of its catalytic activity.
- Shirini, Farhad,Mamaghani, Manouchehr,Seddighi, Mohadeseh
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p. 5611 - 5619
(2015/07/08)
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- A novel ionic liquid based on imidazolium cation as an efficient and reusable catalyst for the one-pot synthesis of benzoxazoles, benzthiazoles, benzimidazoles and 2-arylsubstituted benzimidazoles
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A novel dicationic ionic liquid based on imidazolium cation is designed, synthesized and successfully used as catalyst for the one-pot synthesis of benzoxazoles, benzthiazoles, benzimidazoles and 2-arylsubstituted benzimidazoles. The remarkable feature of this new catalyst is its ethyleneoxy bridge which participates in dissolving organic compound in ionic liquid. The application of this ionic liquid is studied in a new one-pot method for synthesis of heterocyclic compounds under solvent-free conditions. Simple and convenient procedure, high conversion, reusability of catalyst, easy purification and shorter reaction time are the advantageous features of this method.
- Hasanpour, Maede,Eshghi, Hossein,Bakavoli, Mehdi,Mirzaeia, Mahdi
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p. 412 - 419
(2015/05/27)
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- Benzimidazoles and benzoxazoles via the nucleophilic addition of anilines to nitroalkanes
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PPA-induced umpolung triggers efficient nucleophilic addition of unactivated anilines to nitroalkanes to produce N-hydroxyimidamides. The latter undergo sequential acid-promoted cyclocondensation with ortho-OH or ortho-NHR moieties to afford benzoxazoles
- Aksenov, Alexander V.,Smirnov, Alexander N.,Aksenov, Nicolai A.,Bijieva, Asiyat S.,Aksenova, Inna V.,Rubin, Michael
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p. 4289 - 4295
(2015/04/14)
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- Chitosan: An efficient recyclable catalyst for transamidation of carboxamides with amines under neat conditions
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A novel chitosan-catalyzed transamidation of carboxamides with amines under solvent-free conditions is described. A series of amide derivatives as well as more challenging aryl and alkyl amines with long-chain alkyl substituents could be selectively converted into the corresponding transamidation products, which are frequently found in biologically active compounds and pharmaceuticals. Under similar reaction conditions benzo[d]heterocycles were also obtained via a one-pot synthesis through transamidation and subsequent dehydration. Recyclability of chitosan was demonstrated, with quantitative yields of products obtained without any loss of catalytic activity. the Partner Organisations 2014.
- Nageswara Rao, Sadu,Chandra Mohan, Darapaneni,Adimurthy, Subbarayappa
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supporting information
p. 4122 - 4126
(2014/10/15)
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- Palladium-catalyzed synthesis of benzoxazoles by the cleavage reaction of carbon-carbon triple bonds with o-aminophenol
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A novel and mild procedure for efficient synthesis of benzoxazoles by the cleavage reaction of carbon-carbon triple bonds with o-aminophenol in the presence of a catalytic amount of palladium chloride has been successfully developed, which provides rapid and efficient access to benzoxazoles. the Partner Organisations 2014.
- Xie, Hou-Zhi,Gao, Qi,Liang, Ying,Wang, Heng-Shan,Pan, Ying-Ming
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supporting information
p. 2132 - 2135
(2014/04/17)
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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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- A ball-milling strategy for the synthesis of benzothiazole, benzimidazole and benzoxazole derivatives under solvent-free conditions
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A convenient solvent-free method for the synthesis of benzothiazole, benzimidazole, and benzoxazole derivatives has been developed using recyclable ZnO-NPs via a ball-milling strategy. The method affords environmentally friendly reaction conditions that score high on the ecoscale with the low E-factor. The process is also highly efficient even on a multi-gram scale and provides easy product isolation.
- Sharma, Hemant,Singh, Narinder,Jang, Doo Ok
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p. 4922 - 4930
(2015/01/08)
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- A green and efficient protocol for the synthesis of quinoxaline, benzoxazole and benzimidazole derivatives using heteropolyanion-based ionic liquids: As a recyclable solid catalyst
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In this paper, we introduce two nonconventional ionic liquid compounds which are composed of propane sulfonate functionalized organic cations and heteropolyanions as green solid acid catalysts for the highly efficient and green synthesis of 2,3-disubstitutedquinoxaline derivatives. These ionic liquids are in the solid state at room temperature and the synthesis is carried out via the one-pot condensation reaction of various o-phenylenediamine with 1,2-diketone derivatives. Benzoxazole and benzimidazole derivatives were also synthesized by these novel catalysts via the one-pot condensation from reaction orthoester with o-aminophenol (synthesis of benzoxazole derivatives) and ophenylenediamine (synthesis of benzimidazole derivatives). All experiments successfully resulted in the desired products. The described novel synthesis method has several advantages of safety, mild condition, high yields, short reaction times, simplicity and easy workup compared to the traditional method of synthesis.
- Vahdat, Seyed Mohammad,Baghery, Saeed
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p. 618 - 627
(2013/09/12)
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- Tungstate sulfuric acid as an efficient catalyst for the synthesis of benzoxazoles and benzothiazoles under solvent-free conditions
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Tungstate sulfuric acid (TSA) has been found to be an efficient and reusable catalyst for the synthesis of benzoxazole and benzothiazole derivatives via reactions of orthoesters with o-aminophenols or o-aminothiophenols in high yields.
- Farahi, Mahnaz,Karami, Bahador,Azari, Masume
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p. 1029 - 1034
(2013/11/06)
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- Synthesis of 2-aminobenzoxazoles and 3-aminobenzoxazines via palladium-catalyzed aerobic oxidation of o -aminophenols with isocyanides
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A Pd-catalyzed aerobic oxidation of o-aminophenols and isocyanides for the synthesis of 2-aminobenzoxazoles and 3-aminobenzoxazines has been achieved in an air atmosphere. The procedure constructs 2-aminobenzoxazoles and 3-aminobenzoxazines with moderate to excellent yields and a broad substrate scope. Apart from experimental simplicity, this methodology has the advantages of mild reaction conditions and easily accessible starting materials. Furthermore, the utility of this method has also been successfully applied to the synthesis of other types of useful nitrogen heterocycles.
- Liu, Bifu,Yin, Meizhou,Gao, Hanling,Wu, Wanqing,Jiang, Huanfeng
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p. 3009 - 3020
(2013/06/26)
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- An efficient synthesis of 2-substituted benzoxazoles using cerium(III) chloride/sodium iodide as catalyst
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An efficient and environmentally benign method for the synthesis of 2-substituted benzoxazoles is reported. The condensation of 2-aminophenol with an aldehyde gave an imine intermediate, which was cyclized and dehydrogenated to 2-substituted benzoxazole with good yield in the presence of CeCl 3 /NaI as catalyst. The one-pot synthesis was carried out in toluene at 100 ° C using O 2 as the oxidant.
- Zhu, Xun,Wei, Yunyang
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p. 211 - 214
(2013/01/16)
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- Compounds for Use in the Detection of Neurodegenerative Diseases
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Provided are the use of the disclosed compounds as imaging agents and methods for in vivo imaging and detection of pathological characteristics unique to synuclein diseases, such as Parkinson's disease.
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- Selective formation of formamidines or 7-aminomethylbenzoxazoles from unprecedented couplings between benzoxazoles and amines
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A method for the selective synthesis of amidines by ring-opening amination or of 7-aminomethylbenzoxazoles via a novel three-component-coupling reaction (arene, dichloromethane and amine) from benzoxazoles and amines was developed. Amidines could be further converted into 2-aminobenzoxazoles in high yield. Copyright
- Yu, Dingyi,Lee, Szehui,Sum, Yin Ngai,Zhang, Yugen
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supporting information; scheme or table
p. 1672 - 1678
(2012/07/30)
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- Palladium-catalyzed direct phosphonation of azoles with dialkyl phosphites
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The first Pd-catalyzed direct phosphonation of azoles with dialkyl phosphites has been achieved without addition of base or acid. This method involves the oxidative cleavage of C-H and P(O)-H bonds and represents an atom-efficiency alternative to the classical phosphonation of Ar-X. A Pd II/PdIV mechanism has been studied and proposed.
- Hou, Chaodong,Ren, Yunlai,Lang, Rui,Hu, Xiaoxue,Xia, Chungu,Li, Fuwei
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supporting information; experimental part
p. 5181 - 5183
(2012/06/01)
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- A method for the reductive scission of heterocyclic thioethers
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A mild, chemoselective, and generally high-yielding method for the reductive scission of heterocyclic thioethers is described. Suitable heterocycles have a thioether substituent at the 2-position relative to a ring heteroatom. The convenient and straightforward method is demonstrated with reactants which are not compatible with the standard Raney nickel conditions such as sulfides, sulfones, and thiophenes. In addition, benzyl esters, benzyl amides, and benzyl carbamates are tolerated by the reductive reaction conditions.
- Graham, Thomas H.,Liu, Wensheng,Shen, Dong-Ming
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supporting information; experimental part
p. 6232 - 6235
(2012/01/03)
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- Rhodium-catalyzed phenylthiolation reaction of heteroaromatic compounds using α-(phenylthio)isobutyrophenone
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In the presence of catalytic amounts of RhH(PPh3)4 and 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-benzothiazoles, 1,3-benzoxazoles, and benzothiophene reacted with α-(phenylthio) isobutyrophenone giving 2-phenylthio derivatives. Reactive monocyclic heteroaromatics, 1-methyl-1,2,3,4-tetrazole and 2-cyanothiophene were also converted into the 5-phenylthio derivatives. The use of an appropriate phenylthio transfer reagent is crucial for the efficient catalyzed conversion of heteroaromatic C-H bonds into C-S bonds.
- Arisawa, Mieko,Toriyama, Fumihiko,Yamaguchi, Masahiko
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supporting information; experimental part
p. 2344 - 2347
(2011/05/16)
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- 1,3-Dibromo-5,5-dimethylhydantoin as an efficient homogeneous catalyst for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines
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A simple and highly efficient method for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines is described. Condensation of orthoesters with o-substituted anilines or 2-amino-3-hydroxypyridine was performed in the presence of catalytic amounts of commercially available, inexpensive, and moisture-stable 1,3-dibromo-5,5-dimethylhydantoin under solvent-free conditions. The corresponding heterocycles were obtained in good to excellent yields. The main advantages of the present procedure are mild reaction conditions, short reaction times, high yields of products, easy work-up, and absence of solvent. Graphical abstract: [Figure not available: see fulltext.]
- Hojati, Seyedeh Fatemeh,Maleki, Behrooz,Beykzadeh, Zahra
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experimental part
p. 87 - 91
(2011/09/19)
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- Expeditious and efficient synthesis of benzoxazoles, benzothiazoles, benzimidazoles catalyzed by Ga(OTf)3 under solvent-free conditions
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A new and efficient method for the synthesis of benzoxazoles, benzothiazoles, benzimidazoles from reactions of o-substituted aminoaromatics with orthoesters in the presence of catalytic amounts of Ga(OTf)3 under solvent-free conditions is presented. The remarkable features of this new protocol are high conversion, very short reaction times, cleaner reaction profiles under solvent-free conditions, straight forward procedure, and use of relatively non-toxic catalysts.
- Liu, Juyan,Liu, Qian,Xu, Wei,Wang, Weilu
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experimental part
p. 1739 - 1744
(2012/02/14)
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- Microwave-assisted efficient one-step synthesis of amides from ketones and benzoxazoles from (2-hydroxyaryl) ketones with acetohydroxamic acid using sulfuric acid as the catalyst
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Efficient one-step method for the synthesis of amides directly from ketones and benzoxazoles from (2-hydroxyaryl) ketones by the reaction of acetohydroxamic acid using sulfuric acid as catalyst was described.
- Madabhushi, Sridhar,Chinthala, Narsaiah,Vangipuram, Venkata Sairam,Godala, Kondal Reddy,Jillella, Raveendra,Mallu, Kishore Kumar Reddy,Beeram, China Ramanaiah
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experimental part
p. 6103 - 6107
(2011/11/30)
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- An efficient synthesis of benzoxazoles using silica-supported tin exchanged silicotungstic acid catalyst
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An efficient method for the preparation of benzoxazoles by reacting aminophenols with orthoesters in the presence of silica-supported tin exchanged silicotungstic acid catalyst under mild conditions with high yield and selectivity is demonstrated. The catalysts were characterized by FT-IR and pyridine adsorbed FT-IR. The catalyst exhibited consistent activity upon recycling and is highly active compared to other catalysts. The role of Lewis acidity of the catalysts and plausible reaction mechanism is presented.
- Srivani,Venkateswar Rao,Sai Prasad,Lingaiah
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experimental part
p. 119 - 123
(2010/12/18)
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- Catalytic flash vacuum pyrolysis (CFVP): A new way to afford 7H-dibenzo[b,d]azepin-7-one
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Catalytic flash vacuum pyrolysis (cfvp) of 2-(1H-1,2,3-benzotriazol-1-yl)-phenylethanone (1) was performed over different mesoporous solids of the MCM-41 type: pure Si-MCM-41, Al-MCM-41 and Ti-MCM-41 with Si/metal ratio equal to 20 and 120. While in the absence of the catalyst (conventional fvp) the thermal reaction afforded 7H-dibenzo[b,d]azepin-7-one (5) as the main product between 400 and 500 °C, in the cfvp systems different products were obtained between 350 and 450 °C depending on the type of catalysts. Al-MCM-41 showed the best catalytic performance with azepinone selectivity of 87% at 450 °C. The mechanisms of formation of these different products as well as the effect of different solids are discussed. Mesoporous materials used in this study have been prepared by direct hydrothermal synthesis. Structural regularity was determined by XRD and highly ordered structures were obtained.
- Moyano, Elizabeth L.,Eimer, Griselda A.,Lucero, Paola L.,Chanquia, Corina M.,Herrero, Eduardo R.,Yranzo, Gloria I.
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scheme or table
p. 98 - 103
(2010/10/02)
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- Carbon dioxide as the C1 source for direct C-H functionalization of aromatic heterocycles
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(Equation Presented). A simple and straightforward method has been developed for the direct carboxylation of aromatic heterocylces such as oxazoles, thiazoles, and oxadiazoles using CO2 as the C1 source. The reactions require no metal catalyst and only Cs2CO3 as the base. A good functional group tolerance is achieved.
- Vechorkin, Oleg,Hirt, Nathalie,Hu, Xile
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supporting information; experimental part
p. 3567 - 3569
(2010/10/02)
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- Synthesis of benzimidazoles and benzoxazoles using palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate) as a novel catalyst
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Structurally well-defined palladium bis(2,2,6,6-tetramethyl-3,5- heptanedionate) complex is reported to be an efficient catalyst for the synthesis of benzimidazole and benzoxazole derivatives in good yields. A novel approach for one-pot synthesis of benzimidazoles via direct reductive amination and N-arylation followed by hydrogenation-cyclization methodology is also described. Copyright
- Bhor, Malhari D.,Bhanage, Bhalchandra M.
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experimental part
p. 1743 - 1749
(2010/07/04)
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- BIS(AMINOPHENOL) DERIVATIVE, PROCESS FOR PRODUCING SAME, POLYAMIDE RESIN, POSITIVE PHOTOSENSITIVE RESIN COMPOSITION, PROTECTIVE FILM, INTERLAYER DIELECTRIC FILM, SEMICONDUCTOR DEVICE, AND DISPLAY ELEMENT
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A bis(aminophenol) derivative having substituents at positions adjacent to two amino groups is provided. The bis(aminophenol) derivative is used as a raw material of a polyamide resin for a positive-tone photosensitive resin composition. A polyamide resin comprising bis(aminophenol) and a structure derived from a carboxylic acid is also provided, the bis(aminophenol) having substituents at positions adjacent to the two amino groups. A positive-tone photosensitive resin composition comprising a polybenzooxazole precursor resin, exhibiting high sensitivity and a high cyclization rate even when cured at a low temperature is provided. Also provided is a positive-tone photosensitive resin composition comprising a polyamide resin having an imide structure, an imide precursor structure, or an amide acid ester structure. The composition exhibits high sensitivity and produces a cured product having low water absorption even when cured at a low temperature.
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- Indium-mediated one-pot synthesis of benzoxazoles or oxazoles from 2-nitrophenols or 1-aryl-2-nitroethanones
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One-pot reduction-triggered heterocyclizations from 2-nitrophenols to benzoxazoles and from 1-aryl-2-nitroethanones to oxazoles were investigated. In the presence of indium/AcOH in benzene at reflux, 2-nitrophenols and R-C(OMe)3 (R=H, Me, Ph) produced excellent yields of corresponding benzoxazoles within an hour. Similarly, 1-aryl-2-nitroethanones and Ph-C(OMe)3 in the presence of indium/AcOH in acetonitrile transformed into the corresponding oxazoles with good yields.
- Lee, Jung June,Kim, Jihye,Jun, Young Moo,Lee, Byung Min,Kim, Byeong Hyo
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experimental part
p. 8821 - 8831
(2009/12/26)
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