Efficient one-pot preparation of 5-substituted-2-amino-1,3,4-oxadiazoles using resin-bound reagents

A robust one-pot solution-phase synthesis of 2-amino-1,3,4-oxadiazoles directly from acylhydrazines and isothiocyanates is described. Commercially-available polymer-supported reagents help facilitate both cyclization and purification. This convenient method benefits from its broad applicability, ease and safety of reagent handling, simple product isolation, and the ability to perform multiple reactions in parallel fashion without need for purification. The details and scope of this reaction strategy are presented herein.     

2-取代-5-吡唑基-1，3，4-恶二唑类化合物的合成及生物活性

以5-吡唑甲酰肼和取代羧酸为起始物,运用"一锅煮"法合成了一系列2-取代-5-吡唑基-1,3,4-二唑.此外,还合成了1-苯酰基-2-吡唑酰基肼.初步生物活性测定结果表明,部分化合物有较好的杀菌和除草活性.     

Synthesis of 2-amino-1,3,4-oxadiazoles from isoselenocyanates via cyclodeselenization

An efficient one-pot method to access 2-amino-1,3,4-oxadiazoles from isoselenocyanates and hydrazides or dihydrazides was developed via cyclodeselenization. Without any harsh reagents, various 2-amino-1,3,4-oxadiazoles were obtained in considerably high yields (82%-97%) and purities (>99%) directly with simple crystallization in ethanol. And the formed precipitated Se powder during the reaction could be recycled for preparation of isoselenocyanates efficiently. A plausible mechanism is proposed for the formation of the target products.     

2-芳基-5-苄氧苯基-1,3,4-噁二唑类化合物的合成

由苄氧基苯甲酰肼与各种芳酰氯反应制得N-取代苯甲酰基-4-苄氧苯酰肼(2),2在三氯氧磷存在下发生脱水闭环反应,合成了一系列2-芳基-5-苄氧苯基-1,3,4-噁二唑类化合物,其结构经1H NMR,IR,MS和元素分析表征。     

2-对氯苯氧基-5-芳基-1,3,4-噁二唑的合成

对氯苯氧乙酸乙酯与水合肼反应制得对甲基苯氧乙酰肼（2）;以碳酸钠作缚酸剂,2与卤代苯甲酰氯反应合成了N、N＇-二酰基肼（3）;在POCl3作用下,3脱水环化得2-对氯苯氧基-5-芳基-1,3,4-噁二唑,其结构经1^H NMR,IR,MS和元素分析表征,并对其裂解途径进行了探讨。     

Synthesis of 2-amino-5-(5R-1,2,4-oxadiazolyl-3)-1,3,4-oxadiazoles

The interaction of 2-amino-1,3,4-oxadiazole-5-carboxamidoxime with nitriles in the presence of ZnCl₂ and HCl or with trichloroacetic anhydride affords 2-amino-5-(5R-1,2,4-oxadiazolyl-3)-1,3,4-oxadiazoles. Their reactions with N-nucleophiles have been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2100–2103, December, 1993.     

2-芳氧基-5-苯基-1,3,4-恶二唑类化合物的合成

通过芳氧基负离子在2-甲磺酰基-5-1,3,4-恶二唑上的亲核取代反应制得2-芳氧基-5-苯基-1,3,4-恶二唑.所有化合物的结构经元素分析,IR, ^1H NMR和MS确证.这些化合物表现出一定的抑制枯草芽孢杆菌繁殖的活性.     

Efficient phosphonium-mediated synthesis of 2-amino-1,3,4-oxadiazoles

We present an efficient, room temperature procedure for the preparation of 2-amino-1,3,4-oxadiazoles. Oxadiazol-2-ones can be activated for SNAr substitution using phosphonium reagents (e.g., BOP). This approach provides convenient access to N,N-disubstituted 2-amino-1,3,4-oxadiazoles, which are difficult to prepare using existing synthetic strategies.     

Synthesis of 5-Trimethylsilylethynyl-1,3,4-oxadiazoles

5-Trimethylsilylethynyl-2-R-1,3,4-oxadiazoles were synthesized for the first time by intramolecular cyclocondensation of unsymmetrical N-acyl-N'-(3-trimethylsilyl-2-propynoyl)hydrazines by the action of phosphoryl chloride.     

Efficient one-pot synthesis of substituted 2-amino-1,3,4-oxadiazoles

A convenient one-pot method for the preparation of substituted 2-amino-1,3,4-oxadiazoles has been developed. The method is a significant improvement over previously reported syntheses. Reaction of carboxylic acids with thiosemicarbazides afforded the corresponding oxadiazoles in moderate to good yields. In general, the products precipitated from the reaction mixture, and were collected by filtration. In most of the cases, no chromatographic separations were required. To explore the scope and limitations of this reaction, various aliphatic, aromatic, and heteroaromatic carboxylic acids were reacted with different substituted thiosemicarbazides. The influence of R¹ and R² substituents on the reaction yield and additional results demonstrating the versatility of this method are presented.     

2-苯基-5-芳基-1,3,4-噁二唑的合成与表征

苯甲酸乙酯与水合肼反应制得苯甲酰肼(1),1再分别与芳酰氯反应制得N、N′-二酰基肼(3a～3i),3a～3i在POCl3作用下脱水环化生成2-苯基-5-芳基-1,3,4-噁二唑(4a～4i)。其结构经元素分析,IR,^1H NMR和MS表征,并对其裂解途径进行了探讨。     

2-对硝基苯基-5-芳基-1,3,4-噁二唑的合成与表征

以自制的N,N′-二酰基肼在POCl3作用下脱水环化,合成了8个2-对硝基苯基-5-芳基-1,3,4-噁二唑类化合物。其结构经^1H NMR,IR,MS和元素分析表征,并对其裂解途径进行了探讨。     

Conversion of 2-amino-5-R-phenyl-1,3,4-oxadiazoles into 3-R-phenyl-5-alkoxy-1,2,4-triazoles

2-Amino-5-R-phenyl-1,3,4-oxadiazoles have been shown to isomerize in alcoholic potassium hydroxide solution to 3-R-phenyl-5-alkoxy-1,2,4-triazoles. The dissociative ionization of 3-R-phenyl-5-alkoxy-1,2,4-triazoles and 3-R-phenyl-1,2,4-triazolin-5-ones has been examined. The mass spectra of the oxadiazoles have been compared with those of the triazoles.Translated from Khimiya Geterotslklicheskikh Soedinenii, No. 11, pp. 1553–1556, November, 1986.     

Reaction of 2-amino-5-aryl-1,3,4-oxadiazoles with compounds with activated double bonds

The reaction of 2-amino-5-aryl-1,3,4-oxadiazoles with unsaturated acids and their chlorides was studied. It was shown by IR spectroscopy and mass spectrometry that acylation with acrylic, methacrylic, and cinnamic acid chlorides takes place at the nitrogen atom of the exocyclic amino group. Depending on the solvent, two reaction pathways are realized with unsaturated acids: acylation of the starting 2-amino-5-aryl-1,3,4-oxadiazole occurs in bromobenzene, while nucleophilic addition to the unsaturated acid molecule is realized in DMF in the presence of potassium hydroxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 825–829, June, 1990.     

Synthesis and Spectral-Luminescent Properties of 2-Aryl-5-butyl-1,3,4-oxadiazoles

Russian Journal of General Chemistry - 2-Aryl-5-butyl-1,3,4-oxadiazoles have been obtained in 59–85% yield via refluxing of equimolar amounts of a benzoic acid hydrazide with trimethyl...     

Synthesis and spectral properties of 2-methyl-5-aryl-1,3,4-oxadiazoles

By heterocyclization of 1-acyl-2-aroylhydrazines under the influence of strong dehydrating substances, a series of 2-methyl-5-aryl-1,3,4-oxadiazoles has been synthesized and their UV, IR, and PMR spectra have been investigated. Through analysis of data on the influence of substituents on the position of the maximum in the electronic absorption spectrum, together with calculated data, it has been shown that the long-wave band of 2-methyl-5-phenyl-1,3,4-oxadiazole is due to an S₀–S₁ transition of the –^* type and that it is a charge transfer band for transfer from the phenyl radical to the oxadiazole ring; the 1,3,4-oxadiazole ring as a substituent has an electron-acceptor character.Institute of Single Crystals, National Academy of Sciences of the Ukraine, Khar'kov 310001. Khar'kov State University, Khar'kov 310077. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 816–821, June, 1997.     

2-取代氨基-5-吡唑基-1,3,4-噁二唑的合成及生物活性

取代氨基吡唑基噁二唑;2-取代氨基-5-吡唑基-1;3;4-噁二唑的合成及生物活性