- A mild method for the preparation of 1,3,4-oxadiazoles: Triflic anhydride promoted cyclization of diacylhydrazines
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Diacylhydrazines undergo cyclization upon treatment with triflic anhydride and pyridine to form the corresponding 1,3,4-oxadiazoles in yields ranging from 70-95%.
- Liras, Spiros,Allen, Martin P.,Segelstein, Barb E.
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Read Online
- TiCl4 mediated facile synthesis of 1,3,4-oxadiazoles and 1,3,4-thiadiazoles
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An efficient method for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles and 1,3,4-thiadiazoles has been developed. Various hydrazides or thionyl hydrazides readily react with DMA derivatives in the presence of TiCl4 as a catalyst to afford the desired products. This protocol provides a simple and economical procedure that affords the target products with good yields and wide substrate scope.
- Zhang, Lin,Yu, Yu,Tang, Qiang,Yuan, Jianyong,Ran, Dongzhi,Tian, Binghua,Pan, Tao,Gan, Zongjie
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p. 423 - 431
(2019/12/27)
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- Batch Versus Flow Lithiation–Substitution of 1,3,4-Oxadiazoles: Exploitation of Unstable Intermediates Using Flow Chemistry
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1,3,4-Oxadiazoles are a common motif in pharmaceutical chemistry, but few convenient methods for their modification exist. A fast, convenient, high yielding and general α-substitution of 1,3,4-oxadiazoles has been developed using a metalation-electrophilic trapping protocol both in batch and under continuous flow conditions in contradiction to previous reports which suggest that α-metalation of this ring system results in ring fragmentation. In batch, lithiation is accomplished at an industrially convenient temperature, ?30 °C, with subsequent trapping giving isolated yields of up to 91 %. Under continuous flow conditions, metalation is carried out at room temperature, and subsequent in flow electrophilic trapping gave up to quantitative isolated yields. Notably, lithiation in batch at room temperature results only in ring fragmentation and we propose that the superior mixing in flow allows interception and exploitation of an unstable intermediate before decomposition can occur.
- Wong, Jeff Y. F.,Tobin, John M.,Vilela, Filipe,Barker, Graeme
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supporting information
p. 12439 - 12445
(2019/09/06)
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- Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles by visible-light-mediated decarboxylation–cyclization of hydrazides and diketones
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A visible-light-induced synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from simple diketones and hydrazides with the assistant of the photocatalyst eosin Y catalyzed decarboxylation and cyclization under mild conditions has been discovered. The reaction tolerates a wide range of functional groups and gives a variety of valuable 1,3,4-oxadiazoles in moderate to good yields. Finally, a plausible reaction mechanism was proposed.
- Diao, Pinhui,Ge, Yanqin,zhang, Wenpei,Xu, Chen,Zhang, Nannan,Guo, Cheng
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supporting information
p. 767 - 770
(2018/02/07)
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- Iron(III)/TEMPO-Catalyzed Synthesis of 2,5-Disubstituted 1,3,4-Oxadiazoles by Oxidative Cyclization under Mild Conditions
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A simple and efficient cationic Fe(III)/TEMPO-catalyzed oxidative cyclization of aroyl hydrazones has been developed for the synthesis of 2,5-disubstituted 1,3,4-oxadiazole derivatives. The reaction offers a broad scope, good functional-group tolerance, and high yields under mild conditions in the presence of O 2.
- Zhang, Guofu,Yu, Yidong,Zhao, Yiyong,Xie, Xiaoqiang,Ding, Chengrong
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p. 1373 - 1377
(2017/06/27)
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- Alkyl aryl-substituted oxadiazole compound of three-component synthetic method (by machine translation)
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The invention relates to a kind of the following formula (III) alkyl aryl substituted oxadiazoles as shown in synthetic method of compound, said method comprising: in the organic solvent, the following formula (I) compounds, of formula (II) compound and amine source compound, the catalyst, alkali, additive and the presence of oxidation aid, for 80 - 100 °C lower reaction 6 - 10 hours, the reaction is finished after treatment, thereby obtaining states the type (III) compound, Wherein R1 For C1 - C6 Alkyl; R2 Is H, C1 - C6 Alkyl, C1 - C6 Alkoxy or halogen. The method by adopting specific three-component reaction system, and the particular oxidation agent, the addition of specific catalytic system integrated synergistic, thus can yield to obtain the target product, has good application prospect and value. (by machine translation)
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Paragraph 0033; 0034; 0047-0049; 0058; 0090
(2017/08/29)
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- Three-component synthesis method of oxadiazole compound
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The invention relates to a synthesis method of an oxadiazole compound shown in formula (III). The method comprises steps as follows: a compound shown in formula (1), a compound shown in formula (II) and an amine source compound react at 80-100 DEG C for 6-10 h in the presence of an organic solvent, a catalyst, base and an additive, after-treatment is performed after the reaction ends, and the compound shown in formula (III) is obtained, wherein R1 is C1-C6 alkyl groups, phenyl groups or phenyl groups substituted with substitute groups, substitute groups are C1-C6 alkyl groups, C1-C6 alkoxy groups or halogen, and R2 is H, C1-C6 alkyl groups, C1-C6 alkoxy groups or halogen. A specific three-component reaction system is adopted in the method, comprehensive synergism of a specific catalytic system is combined, so that a target product can be obtained at the high yield, and the method has good application prospect and value.
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Paragraph 0051-0053
(2017/05/12)
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- A process for preparing 2, 5 - disubstituted - 1, 3, 4 - oxadiazoles (by machine translation)
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The invention provides a method for catalytic oxidative cyclization of formula (II) is shown in the 1, 3, 4 - oxadiazole method, said method comprising: in order to having a structure of formula (I) indicated by the formyl zong compound as a raw material, in order to air or oxygen atmosphere, in order to nitric acid the iron is catalyst, in order to 2, 2, 6, 6 - tetramethyl piperidine nitrogen oxides as initiator, under the action of the water absorbing agent, under the action of the water absorbing agent, in an organic solvent, for 25 - 60 °C lower reaction 3 - 12h, and the resulting reaction solution by the following formula (II) after treatment indicated by the 1, 3, 4 - oxadiazole compounds; the reaction of the invention speed, mild condition, easy operation, low cost, safe reaction, the whole process is friendly to the environment, pollution-free. (by machine translation)
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Paragraph 0031; 0032; 0033; 0034; 0035; 0096-0100
(2017/07/19)
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- Iodine-catalysed oxidative cyclisation of acylhydrazones to 2,5-substituted 1,3,4-oxadiazoles
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An environmentally benign synthesis of 2,5-disubstituted 1,3,4-oxadiazoles has been developed starting from N-aroylhydrazones and N-acetylhydrazones at room or ambient temperature using a catalytic quantity of iodine in the presence of an aqueous hydrogen peroxide oxidant.
- Majji, Ganesh,Rout, Saroj Kumar,Guin, Srimanta,Gogoi, Anupal,Patel, Bhisma K.
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p. 5357 - 5362
(2014/01/23)
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- Microwave-assisted one-step synthesis of 2,5-disubstituted-1,3,4- oxadiazoles using 1,4- bis(triphenylphosphonium)-2-butene peroxodisulfate
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A series of 1,3,4-oxadiazoles were efficiently synthesized from the cyclization-oxidation reaction of acyl hydrazones by using 1,4- bis(triphenylphosphonium)-2-butene peroxodisulfate as an oxidant in solvent-free medium under microwave irradiation.
- Gorjizadeh, Maryam,Afshari, Mozhgan,Nazari, Simin
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p. 1627 - 1630
(2014/05/06)
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- I2-mediated oxidative C-O bond formation for the synthesis of 1,3,4-oxadiazoles from aldehydes and hydrazides
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A practical and transition-metal-free oxidative cyclization of acylhydrazones into 1,3,4-oxadiazoles has been developed by employing stoichiometric molecular iodine in the presence of potassium carbonate. The conditions of this cyclization reaction also work well with crude acylhydrazone substrates obtained from the condensation of aldehydes and hydrazides. A series of symmetrical and asymmetrical 2,5-disubstituted (aryl, alkyl, and/or vinyl) 1,3,4-oxadiazoles can be conveniently generated in an efficient and scalable fashion.
- Yu, Wenquan,Huang, Gang,Zhang, Yueteng,Liu, Hongxu,Dong, Lihong,Yu, Xuejun,Li, Yujiang,Chang, Junbiao
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p. 10337 - 10343
(2013/11/06)
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- A mild, one-pot preparation of 1,3,4-oxadiazoles
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A mild and efficient one-pot protocol for the synthesis of 1,3,4-oxadiazoles from carboxylic acids and acylhydrazides was developed. Diacylhydrazide formation via HATU coupling followed by addition of Burgess reagent afforded the corresponding 1,3,4-oxadiazoles in 63-96% yields at room temperature. The reaction conditions are tolerant of a variety of functional groups, including esters, nitriles, alkynes, olefins, alkyl halides, phenols, carbamates and sulfonamides.
- Li, Changkun,Dickson, Hamilton D.
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experimental part
p. 6435 - 6439
(2011/02/23)
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- Convenient preparation of unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles promoted by Dess-Martin reagent
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2,5-Disubstituted 1,3,4-oxadiazoles have been conveniently prepared by oxidative cyclization of N-acyl-N′-aryliden-hydrazines promoted by an excess of Dess-Martin periodinane under mild conditions (23 examples, up to 92% isolated yields).
- Dobrotǎ, Cristian,Paraschivescu, Codru?a C.,Dumitru, Ioana,Matache, Mihaela,Baciu, Ion,Ru?ǎ, Lavinia L.
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scheme or table
p. 1886 - 1888
(2009/07/05)
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- Silica sulfuric acid: An efficient and versatile acidic catalyst for the rapid and ecofriendly synthesis of 1,3,4-oxadiazoles at ambient temperature
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A rapid and green synthesis of 2,5-disubstituted 1,3,4-oxadiazoles is reported. The title compounds were prepared by the reaction of different acyl hydrazides and orthoesters in the presence of silica sulfuric acid under solvent-free conditions. In this new process, reactions were run at ambient temperature and completed in a short period of time with high yields. Copyright Taylor & Francis Group, LLC.
- Dabiri, Minoo,Salehi, Peyman,Baghbanzadeh, Mostafa,Zolfigol, Mohammad Ali,Bahramnejad, Mahboobeh
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p. 1201 - 1209
(2008/02/01)
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- The application of cross-linked poly[styrene(iodoso diacetate)] to the synthesis of 1,3,4-oxadiazoles
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The 2% cross-linked poly[styrene(iodosodiacetate)] has been synthesized, and has been applied effectively to the synthesis of 1,3,4-oxadiazole derivatives, and regenerated and reused for the same reaction.
- Huang, Xian,Zhu, Qing
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p. 300 - 301
(2007/10/03)
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- Hypervalent Iodine Oxidation of N-Acylhydrazones and N-Phenylsemicarbazone: An Efficient Method for the Synthesis of Derivatives of 1,3,4-Oxadiazoles and Δ3-1,3,4-Oxadiazolines
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The oxidation of ketone N-acylhydrazones 1 by phenyliodine(III) diacetate (PIDA) in alcohol gave 2-alkoxy-Δ3-1,3,4-oxadiazolines 4 in excellent yields, while the oxidative cyclization of aldehyde N-acylhydrazone 2 by PIDA in methanolic sodium acetate gave 2,5-disubstituted 1,3,4-oxadiazoles in good yields.The oxidation of acetone 4-phenylsemicarbazone afforded 2-(N-phenylimino)-Δ3-1,3,4-oxadiazoline in excellent yield.
- Yang, Rui-Yang,Dai, Li-Xin
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p. 3381 - 3383
(2007/10/02)
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- Electrooxidative Cyclization of N-Acylhydrazones of Aldehydes and Ketones to Δ3-1,3,4-Oxadiazolines and 1,3,4-Oxadiazoles
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The electrolytic oxidation of ketone N-acylhydrazones (1) in methanolic sodium acetate induced their intramolecular cyclization to the corresponding 2-methoxy-Δ3-1,3,4-oxadiazolines 3.The thermal stability of a given oxadiazoline and what products were formed by its thermal decomposition was found to depend on the natures of the substituents at C-2.Thus, 2-methoxy-2-phenyloxadiazolines preferentially yielded oxiranes 5, whereas 2-alkyl-2-methoxyoxadiazolines preferentially gave enol ethers 6. 2,2-Dimethoxyoxadiazolines decomposed to the parent ketones and many unidentified products.The electrolytic oxidation of aldehyde N-acylhydrazones 2 gave 2,5-disubstituted 1,3,4-oxadiazoles 4.The oxidative cyclization of the N-benzoylhydrazones of aliphatic aldehydes gave especially high yields of the corresponding heterocycles.
- Chiba, Toshiro,Okimoto, Mitsuhiro
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p. 1375 - 1379
(2007/10/02)
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