- 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 0060; 0062; 0063
(2017/08/25)
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- Utility of Nitrogen Extrusion of Azido Complexes for the Synthesis of Nitriles, Benzoxazoles, and Benzisoxazoles
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The utility of the nitrogen extrusion reaction of azido complexes, generated in situ from the corresponding aldehydes or ketones with TMSN3 in the presence of ZrCl4 or TfOH, has been described. These azido complexes could undergo three different pathways, depending on the substrates. First, azido methanolate complexes or imine diazonium ions could lead to benzisoxazole products via an intramolecular nucleophilic substitution. Second, imine diazonium ions could also undergo either the elimination of proton to provide nitrile products in good to excellent yields or an aryl migration, followed by an intramolecular nucleophilic addition, to give benzoxazole products in good yields.
- Nimnual, Phongprapan,Tummatorn, Jumreang,Thongsornkleeb, Charnsak,Ruchirawat, Somsak
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p. 8657 - 8667
(2015/09/15)
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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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- 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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- Novel synthesis of benzoxazoles from o-nitrophenols and amines
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o-Nitrophenols and o-nitroaniline were reacted with amines at 210-215°C to produce the corresponding benzoxazoles and benzimidazoles, respectively, in moderate yields. The reactions between o-nitrophenols containing a CO2Me or OMe group on their benzene rings and N,N-diethylaniline were examined to investigate the effects of the position and electronic character of these substituents on the formation of the oxazole ring.
- Nishioka, Hiromi,Ohmori, Yukiko,Iba, Yumiko,Tsuda, Eri,Harayama, Takashi
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p. 193 - 198
(2007/10/03)
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