Ueber Amidoxime und Azoxime

Tiemann, Ferd.; Kruger, Paul E.

doi:10.1002/cber.18840170230

Cited by 123 publications

(65 citation statements)

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“…The reaction presumably proceeds via 5-cyanopentanonitrile oxide 18 and the dioxathiazolone 37, which on heating affords the isocyanate with expulsion of SO 2 . The early literature suggests that 3,5-aryl-1,2,4-oxadiazoles are more stable than the corresponding furazans, [18][19][20] Mass spectrometry studies have shown that electron impact-induced fragmentation of 38 also proceeds via Path A. 29 It was anticipated that by using the FVP technique which had successfully been applied to diphenylfuroxan 6 and diphenylfurazan 5, it might prove possible to isolate the putative benzonitrile oxide intermediate 7 formed on fragmentation of the 1,2,4-oxadiazole analogue 38a.…”

Section: Methodsmentioning

confidence: 99%

“…17 3,5-Diaryl-1,2,4-oxadiazoles have long been known for their thermal stability. For example, 3,5-diphenyl-1,2,4-oxadiazole can be distilled at 296 ºC; 18 however, as found for the isomeric furazan 5, on prolonged heating, partial decomposition leads to phenyl isocyanate and benzonitrile. 19,20 We now report the results of an investigation into the fragmentation of a range of furazans and of 3,5-diphenyl-1,2,4-oxadiazole using both solution phase and flash vacuum pyrolysis (FVP) techniques.…”

Section: Introductionmentioning

confidence: 99%

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Thermal fragmentation of 1,2,5- and 1,2,4-oxadiazoles

Mitchell¹,

Paton²

2010

Arkivoc

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Thermolysis of 3,4-diphenyl-1,2,5-oxadiazole (diphenylfurazan) in tetradec-1-ene at 245 ºC afforded 5-dodecyl-3-phenyl-2-isoxazoline resulting from cycloaddition of benzonitrile oxide to the alkene. Similarly, the tetramethylene and decamethylene furazans 13 and 15 in 4-methoxybenzonitrile at 240 ºC fragmented to ω-cyanoalkanonitrile oxides, which were trapped as their 1,2,4-oxadiazole cycloadducts 17 and 19, respectively. The flash vacuum pyrolysis (FVP, 550-650 ºC) technique was used to investigate the process in more detail using a range of mono and bicyclic furazans. In all cases the 1,2,5-oxadiazole ring cleaved cleanly at O(1)−N(2) and C(3)−C(4) to nitrile and nitrile oxide fragments. The nitrile oxides were trapped in high yield (81-100%) as their isoxazoline cycloadducts by reaction with hex-1-ene. The tetramethylene furazan 13 was converted into 4-cyanobutyl isocyanate by FVP and reaction of the condensate with sulfur dioxide. 3,5-Diphenyl-1,2,4-oxadiazole showed greater thermal stability under similar conditions (FVP, 600 ºC), but at higher temperatures (700-800 ºC) phenyl isocyanate was formed and trapped as its methyl urethane derivative. Attempts to trap the putative benzonitrile oxide intermediate were unsuccessful.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermal fragmentation of 1,2,5- and 1,2,4-oxadiazoles

Mitchell¹,

Paton²

2010

Arkivoc

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“…4 Metronidazole (6) and benznidazole (7) are two antiprotozoal drugs acting through the generation of intracellular radical species which can damage both parasites' DNA and other cellular machinery. 5 The antibacterial fluoroquinolone ciprofloxacin (8) acts through the damage of bacterial DNA. 6 Raltegravir (9) is an HIV-1 integrase inhibitor, useful for the treatment of HIV infections.…”

Section: Nitrogen Heterocycles and Drug Discoverymentioning

confidence: 99%

“…7 by two atoms of carbon, two atoms of nitrogen and one atom of oxygen. They were firstly discovered in 1884 by Tiemann and Krüger, 8 then named furo [ab]diazoles. Oxadiazoles can be isosterically compared with furan, 9 but the replacement of two methine groups (−CH=) by two sp 2 nitrogen (−N=) reduces their aromaticity so that some of their isomers are electronically comparable to conjugated diene systems.…”

Section: Nitrogen Heterocycles and Drug Discoverymentioning

confidence: 99%

“…1,2,4-Oxadiazole rings, for example, are stable even in the presence of concentrated sulfuric acid. 8 Another relevant aspect of oxadiazoles is their capability of acting as a hydrogen bond acceptor, due to the nonligand electron pairs from the heteroatoms present in their structures. 16 In drug discovery and development, oxadiazole rings are commonly employed as bioisosteric replacement for carbonyl-containing groups such as esters, amides, carbamates and hydroxamic esters.…”

Section: Nitrogen Heterocycles and Drug Discoverymentioning

confidence: 99%

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1,2,4- and 1,3,4-Oxadiazoles as Scaffolds in the Development of Antiparasitic Agents

Pitasse-Santos¹,

Sueth-Santiago²,

Lima³

2017

J. Braz. Chem. Soc.

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In this review, we present the potential use of the heterocyclic oxadiazole rings in the design and synthesis of new drugs to treat parasitic infections. We intend to compare herein all the four isomeric forms of oxadiazole rings as well as discuss the differences and similarities between them. In addition, we discuss aspects on their reactivity that justify the great importance of both 1,2,4-and 1,3,4-oxadiazoles isomers when compared with their other two isomers. Although some oxadiazole isomers satisfy Hückel's rule, there are differences concerning their aromaticity, which have a great impact on the possible interactions of the oxadiazole ring with biological receptors. The set of works selected from the literature and discussed herein points out the oxadiazole core as an important and versatile scaffold in the development of new chemical entities potentially useful as antiparasitic drugs.

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