- Eco-friendly syntheses of 2-substituted benzoxazoles and 2-substituted benzothiazoles from 2-aminophenols, 2-aminothiophenols and DMF derivatives in the presence of imidazolium chloride
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A simple, economical and metal-free approach to the synthesis of 2-substituted benzoxazoles and 2-substituted benzothiazoles from 2-aminophenols, 2-aminothiophenols and DMF derivatives, only using imidazolium chloride (50% mmol) as promoter without any other additive, was reported. Various 2-substituted benzoxazoles and 2-substituted benzothiazoles were thus prepared in moderate to excellent yields.
- Tian, Qingqiang,Luo, Wen,Gan, Zongjie,Li, Dan,Dai, Zeshu,Wang, Huajun,Wang, Xuetong,Yuan, Jianyong
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supporting information
(2019/01/21)
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- Synthesis method of 2-substituted benzoxazole, 2-substituted benzothiazole and derivatives thereof
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The invention provides a synthesis method of 2-substituted benzoxazole, 2-substituted benzothiazole and derivatives thereof. In the method, through ortho-aminophenol/2-aminothiophenol cyclization catalyzed by imidazole hydrochloride, synthesis of functionalized 2-substituted benzoxazole and 2-substituted benzothiazole is realized; the method is simple, economical and high in practicality. No othercatalysts or additives are used, the synthesis method ensures good functional group tolerance and excellent yield and purity, the reaction time is short, no harsh reaction conditions are needed, andthe method is suitable for industrial production.
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Paragraph 0040; 0052-0053
(2019/02/10)
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- Metal free montmorillonite KSF clay catalyzed practical synthesis of benzoxazoles and benzothiazoles under aerobic conditions
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An efficient method for the synthesis of benzoxazoles and benzothiazoles via montmorillonite KSF clay catalyzed condensation reaction between 2-aminophenols or 2-aminothiophenols and β-diketones is reported. The efficiency of the reaction reflects from the wide substrate scope with electronic differentiation on aryls. The reaction is metal free and proceeds without the exclusion of air or moisture, and further the catalyst can be recycled up to 3–5 catalytic cycles.
- Kummari, Vijaya Babu,Chiranjeevi, Kalavakuntla,Suman Kumar, Alleni,Kumar, Rathod Aravind,Yadav, Jhillu Singh
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supporting information
p. 3335 - 3342
(2019/11/11)
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- Sodium dichloroiodate promoted C-C bond cleavage: An efficient synthesis of 1,3-Benzazoles via condensation of o -amino/mercaptan/hydroxyanilines with β -diketones
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An efficient aqueous sodium dichloroiodate (NaICl 2) mediated protocol is developed for the synthesis of benzofused azoles by the cyclization of 2-amino anilines/thiophenols/phenols with β-diketone compounds. The reactions gave moderate to good yield of the corresponding 2-substituted benzimidazoles/benzothiazoles/benzoxazoles under mild conditions. This tandem process involved a C-C bond cleavage and C-N bond formation. Graphical Abstract?: SYNOPSIS A facile and single protocol for the synthesis of three versatile 1,3-benzazoles viz 2-substituted 1H-benzimidazoles, benzoxazoles and benzothiazoles from readily available starting materials, 1,3-diketones and corresponding o-amino anilines/thiophenols/phenols, by aqueous sodium dichloroiodate (NaICl 2) mediated C—C bond cleavage has been developed. The reaction provides a rapid access to these 1, 3-benzazoles in good yields, thus speeding up the drug discovery process.[Figure not available: see fulltext.].
- Bhagat, Saket B,Ghodse, Shrikant M,Telvekar, Vikas N
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- Multicatalytic Beckmann rearrangement of 2-hydroxylarylketone oxime: Switchable synthesis of benzo[d]oxazoles and N-(2-hydroxylaryl)amides
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A switchable synthesis route is developed for benzo[d]oxazole derivatives and (2-hydroxylaryl)benzamide from 2-hydroxylbenzeneketoxime using organomolecules (BOP-Cl, and CNC) and Lewis acid cocatalyzed Beckmann rearrangement (BR) reaction. Further, this reaction is switched using different organocatalysts.
- Li, Zhen,Fang, Chengtao,Zheng, Yannan,Qiu, Guanyinsheng,Li, Xiaofang,Zhou, Hongwei
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p. 3934 - 3937
(2018/10/02)
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- A benzoxazole derivative synthesis method
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A synthetic method of benzoxazole derivative belongs to the technical field of organic chemistry synthesis. Raw material of a variety of o-hydroxyphenyl ketimines, an oxidant of iodobenzene diacetate and an additive of alkali are subjected to a simple process comprising one-step oxidation rearrangement, concentration and purification in a solvent at room temperature to obtain a product. This method has the characteristics of certain universality, mild reaction conditions, low production equipment requirement, simple technology, easily obtained raw materials, short reaction time and higher efficiency. Benzoxazole derivative products with high yield and good quality can be prepared by adopting the method of the invention; the method can be widely used in industrial production of benzoxazole derivatives; the products prepared by the method of the invention can be widely used as fluorescent whitening agents, dyeing agents, preservatives, rubber vulcanization accelerators and organic electroluminescent materials, as well as antistatic agent for the plastic films; therefore, the invention has good market application prospects.
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Paragraph 0052; 0054; 0055
(2017/08/25)
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- Acid Catalyzed Direct-Amidation-Dehydrocyclization of 2-Hydroxy-acetophenones to Benzoxazoles by a One-Pot Sustainable Synthesis
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A series of 2-methyl-benzoxazoles have been synthesized starting from 2-hydroxy-acetophenones via a one-pot three steps reaction. Hydroxylamonium salt has been used as amidation agent. The reaction occurs with different anions, but the best results is achieved with hydroxylamonium hydrchloride. Despite the number of consecutive stages, the reaction is highly selective. Mild reaction conditions and various solvents can be used, but trifluoroacetic acid is the preferred. Almost, complete recovery of the trifluoroacetic acid can be achieved by vacuum distillation. The role of trifluoroacetic acid, as well as, of the hydroxylamonium salt suggests a cooperative effect leading to high selective formation of 2-methyl-benzoxazoles. Graphical Abstract: One-pot TFA catalyzed synthesis of benzoxazoles starting from 2-hydroxyacetophenones. (Chemical Equation Presented).
- Rancan, Elia,Aric, Fabio,Quartarone, Giuseppe,Ronchin, Lucio,Vavasori, Andrea
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p. 939 - 946
(2015/08/06)
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- One-pot synthesis of benzoxazoles via the metal-free ortho-C-H functionalization of phenols with nitroalkanes
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PPA-activated nitroalkanes are employed in the design of a one-pot cascade transformation involving metal-free and oxidant-free direct ortho-C-H functionalization, followed by Beckman rearrangement and intramolecular cyclocondensation to produce benzoxazoles and benzobisoxazoles directly from easily available phenols.
- Aksenov, Nicolai A.,Aksenov, Alexander V.,Nadein, Oleg N.,Aksenov, Dmitrii A.,Smirnov, Alexander N.,Rubin, Michael
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p. 71620 - 71626
(2015/09/08)
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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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- Hypervalent iodine-mediated synthesis of benzoxazoles and benzimidazoles via an oxidative rearrangement
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A Beckmann-type rearrangement of o-hydroxy and o-aminoaryl N-H ketimines has been developed to prepare benzoxazoles and N-Ts benzimidazoles, respectively. The ketimine derivatives were easily prepared by condensation of ammonia with the corresponding ketones and (diacetoxyiodo)benzene was found to act as an efficient oxidant to trigger the [1,2]-aryl migration towards the formation of the desired heterocycles. Depending on the substitution pattern, the results revealed another mechanistic pathway through which benzisoxazoles or 1H-indazoles could be formed. The Beckmann-type rearrangement strategy was applied to the synthesis of benzimidazole-containing biorelevant targets such as chlormidazole and clemizole.
- Zhang, Xiaohui,Huang, Ruofeng,Marrot, Jér?me,Coeffard, Vincent,Xiong, Yan
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p. 700 - 708
(2015/02/02)
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- Synthesis of benzoxazoles from 2-aminophenols and β-diketones using a combined catalyst of br?nsted acid and copper iodide
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Cyclization reactions of 2-aminophenols with β-diketones catalyzed by a combination of Br?nsted acid and CuI are presented. Various 2-substituted benzoxazoles were obtained through these reactions. Different substituents such as methyl, chloro, bromo, nitro, and methoxy on 2-aminophenol are tolerated under the optimized reaction conditions.
- Mayo, Muhammad Shareef,Yu, Xiaoqiang,Zhou, Xiaoyu,Feng, Xiujuan,Yamamoto, Yoshinori,Bao, Ming
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p. 6310 - 6314
(2014/07/21)
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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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- 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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- 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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- 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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- A divergent and selective synthesis of isomeric benzoxazoles from a single N-Cl imine
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A divergent and regioselective synthesis of either 3-substituted benzisoxazoles or 2-substituted benzoxazoles from readily accessible ortho-hydroxyaryl N-H ketimines is described. The reaction proceeds in two distinct pathways through a common N-Cl imine intermediate: (a) N-O bond formation to form benzisoxazole under anhydrous conditions and (b) NaOCl mediated Beckmann-type rearrangement to form benzoxazole, respectively. The reaction path also depends on the electronic nature of the aromatic ring, with the electron-rich aromatic rings favoring the rearrangement and the electron-deficient rings favoring the N-O bond formation. A Beckmann-type rearrangement mechanism via net [1,2]-aryl migration for the formation of 2-substituted benzoxazole is proposed.
- Chen, Cheng-Yi,Andreani, Teresa,Li, Hongmei
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supporting information; experimental part
p. 6300 - 6303
(2012/01/05)
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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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- Simple and efficient one-pot synthesis of 2-substituted benzoxazole and benzothiazole
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2-Substituted benzoxazole and benzothiazole were synthesized from condensation of aldehyde and 2-aminophenol or 2-aminothiophenol via a one-pot process using diethyl bromo phoshonate and tert-butyl hypochlorite.
- Patil, Sachin S.,Bobade, Vivek D.
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experimental part
p. 206 - 212
(2010/03/30)
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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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- Regioselective syntheses of 2- and 4-formylpyrido[2,1-b]benzoxazoles
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o-Acetaminophenols (2) reacted with Vilsmeier reagent under Meth-Cohn conditions to yield 2-formylpy-rido[2,l-6]benzoxazoles (5) unexpectedly besides the known compounds 2-(benzoxazol-2′-yl)-3-dimethylaminoacroleins (4). Refluxing 4 in acetic anhydride gave 4-formylpyrido[2,l-6]benzoxazoles (6), an isomer of 5. Both 5a and 6a were structurally characterized by X-ray crystallography. A mechanism for the formation of 5 involving sequential chlorination, dimerization, intramolecular elimination of HC1 to form the oxazole ring, formylation twice, and regioselective intramolecular nucleophilic cyclization to construct the pyridone ring is proposed.
- Li, Ke-Lai,Du, Zong-Bo,Guo, Can-Cheng,Chen, Qing-Yun
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supporting information; experimental part
p. 3286 - 3292
(2009/09/08)
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- Efficient synthesis of 2-substituted benzoxazoles via Beckmann rearrangement of 2-hydroxyaryl ketoximes using diethyl chlorophosphate
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An efficient method for synthesis of 2-substituted benzoxazoles has been developed using diethyl chlorophosphate. 2-Hydroxyaryl ketoximes are efficiently converted to benzoxazoles by heating in the presence of diethyl chlorophosphate via Beckmann rearrangement of ketoxime in excellent yields. This method avoids the use of strong acids, harsh conditions, and long reaction times. Georg Thieme Verlag Stuttgart.
- Sardarian,Shahsavari-Fard
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experimental part
p. 1391 - 1393
(2009/04/06)
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- Mild and efficient synthesis of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines catalyzed by Bi(III) salts under solvent-free conditions
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A series of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines was efficiently synthesized from the reactions of o-aminophenols, o-aminothiophenol, o-phenylenediamines, and 2-amino-3- hydroxypyridine with orthoesters in the presence of catalytic amounts of Bi(III) salts, such as Bi(TFA)3, Bi(OTf)3, and BiOClO4 ? xH2O under solvent-free conditions. The remarkable features of this new protocol are high conversion, very short reaction times, cleaner reaction profiles under solvent-free conditions, straightforward procedure, and use of relatively non-toxic catalysts. Springer-Verlag 2007.
- Mohammadpoor-Baltork, Iraj,Khosropour, Ahmad R.,Hojati, Seyedeh F.
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p. 663 - 667
(2008/02/07)
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- Carbon-carbon bond cleavage of diynes through the hydroamination with transition metal catalysts
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The C-C bond cleavage of terminal and internal diynes takes place readily in the presence of catalytic amounts of Ru3(CO)12 or Pd(NO3)2 and of 2-aminophenol, giving the corresponding benzoxazoles and ketones in good to high yields. There are two different modes of the bond cleavage: (a) an alkyne C-C triple bond is cleaved, and (b) the C-C single bond between the two alkyne groups is cleaved. Copyright
- Shimada, Tomohiro,Yamamoto, Yoshinori
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p. 6646 - 6647
(2007/10/03)
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- Use of zeolite catalysts for efficient synthesis of benzoxazoles via Beckmann rearrangement
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Substituted benzoxazoles have been synthesized in very good yields starting from o-acylphenol oximes via Beckmann rearrangement using zeolite catalysis.
- Bhawal,Mayabhate,Likhite,Deshmukh
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p. 3315 - 3321
(2007/10/03)
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