Cycloadditions of nitrile oxides to amidoximes. A general synthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides.

Quadrelli, Paolo; Invernizzi, Anna Gamba; Falzoni, Mario; Caramella, Pierluigi

doi:10.1016/s0040-4020(96)01088-5

Cited by 42 publications

(26 citation statements)

References 15 publications

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“…The more sterically hindered phenylacetylene 2g afforded isoxazole 4g in only 33% yield and appreciable amounts of furoxan 16 and oxadiazole 17 were obtained (Scheme 4) [19]. Oxadiazoles have been previously observed in the dimerization of nitrile oxides and are suggested to be the product of a disproportionation reaction between the initially formed oxadiazole-oxide and excess nitrile oxide [26]. To eliminate any possible role of the acetylene or its intermediates in the formation of oxadiazole 17, the reaction of hydroximinoyl chloride 1 with triethylamine was carried out in the absence of acetylene 2 g. In this case a nearly 1:1 ratio of furoxan 1 6 a n d oxadiazole 17 was obtained, which eliminates the possibility of the acetylene playing a role in the formation of 17 and supports the previously reported disproportionation reaction.…”

Section: Introductionmentioning

confidence: 99%

Reaction of benzohydroximinoyl chlorides and β‐(trifluoromethyl)‐acetylenic esters: Synthesis of regioisomeric (trifluoromethyl)‐isoxazolecarboxylate esters and oxime addition products

Hamper¹,

Leschinsky²

2003

Journal of Heterocyclic Chem

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The triethylamine induced reaction of benzohydroximinoyl chlorides, precursors of nitrile oxides, with β-trifluoromethylacetylenic esters gives rise to three products: 5-trifluoromethyl-4-isoxozolecarboxylate esters, regioisomeric 4-trifluoromethyl-5-isoxazolecarboxylate esters and an unexpected oxime 1,4-addition adduct. Product distribution is rationalized in terms of two competing reaction modes, either 1,4 addition of the oxime anion to the acetylenic ester or formation of the nitrile oxide followed by 1,3-dipolar cycloaddition. Anionic 1,4-addition of the oximinoyl chloride to the acetylenic ester is preferred at low temperatures, while nitrile oxide formation followed by cycloaddition is preferred at temperatures above 0 °C. Regioisomeric products from addition of nitrile oxides to various perfluoroalkylacetylenes are compared and assigned by 13 C NMR.

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Section: Introductionmentioning

confidence: 99%

Reaction of benzohydroximinoyl chlorides and β‐(trifluoromethyl)‐acetylenic esters: Synthesis of regioisomeric (trifluoromethyl)‐isoxazolecarboxylate esters and oxime addition products

Hamper¹,

Leschinsky²

2003

Journal of Heterocyclic Chem

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“…Scheme 8 -Reactional scheme proposed by Kaboudin and Malekzadeh (2011) Another synthetic approach to obtain the oxadiazole ring is the 1,3-dipolar cycloaddition of nitrile oxides to nitriles (RAJAGOPALAN, 1969;QUADRELLI et al, 1997). This is an advantageous way due to the easy synthetic access to the raw materials by its commercial availability, but the low reactivity of triple bond of the nitrile becomes the reaction less favorable.…”

Section: Thfmentioning

confidence: 99%

1,2,4-oxadiazole: A Brief Review from the Literature About the Synthesis and Pharmacological Applications

Rosa¹,

Morcelli²,

Lobo³

2015

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Este trabalho contempla uma breve revisão da literatura, empregando os periódicos das bases de dados Scielo, Sciencedirect e ACS, sobre os métodos mais utilizados para síntese do anel 1,2,4-oxadiazólico, destacando suas vantagens e desvantagens. Foi realizada também uma pesquisa sobre as principais funções deste grupamento, sua ação no tratamento de doenças, os testes realizados para a confirmação das ações farmacológicas e os resultados obtidos.Palavras-chave: oxadiazolas; síntese; farmacologia. ABSTRACT:This work includes a brief literature review, using the periodicals of the Scielo, Sciencedirect and ACS databases, about the most used methods for the synthesis of 1,2,4-oxadiazole ring, highlighting their advantages and disadvantages. It was also done a search in the literature about the main functions of this group, its action in the treatment of diseases, the tests made for the confirmation of the pharmacological actions and the results obtained.

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“…More recently, timeresolved infrared spectroscopic measurements reveal evidence for the first direct observation of an acyl nitroso compound in solution [65]. Other reactions that generate acyl nitroso [66][67][68][69][70][71]. These processes should each be considered as a potential mechanisms of NO or HNO delivery.…”

Section: Acyl Nitroso Compounds As Hno Donorsmentioning

confidence: 99%

N-Hydroxyurea and Acyl Nitroso Compounds as Nitroxyl (HNO) and Nitric Oxide (NO) Donors

Sb¹

2005

CTMC

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Hydroxyurea has emerged as a new therapy for sickle cell disease but a complete mechanistic description of its beneficial actions does not exist. Patients taking hydroxyurea show evidence for the in vivo conversion of hydroxyurea to nitric oxide (NO), which also has drawn interest as a sickle cell disease treatment. While the chemical oxidation of hydroxyurea produces NO or NO-related products, NO formation from the reactions of hydroxyurea and hemoglobin do not occur fast enough to account for the observed increases in patients taking hydroxyurea. Both horseradish peroxidase and catalase catalyze the rapid formation of nitric oxide and nitroxyl (HNO) from hydroxyurea. In these reactions, hydroxyurea is converted to an acyl nitroso species that hydrolyzes to form HNO. The ferric heme protein then oxidizes HNO to NO that combines with the heme iron to form a ferrous-NO complex that may act as an NO donor. In general, acyl nitroso compounds, regardless of the method of their preparation, hydrolyze to form HNO and the corresponding carboxylic acid derivative. Similarly, the incubation of blood and hydroxyurea with urease rapidly form NO-related species suggesting the initial urease-mediated hydrolysis of hydroxyurea to hydroxylamine, which then reacts quickly with hemoglobin to form these products. These studies present two NO releasing mechanisms from hydroxyurea that are kinetically competent with clinical observations.

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Cycloadditions of nitrile oxides to amidoximes. A general synthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides.

Cited by 42 publications

References 15 publications

Reaction of benzohydroximinoyl chlorides and β‐(trifluoromethyl)‐acetylenic esters: Synthesis of regioisomeric (trifluoromethyl)‐isoxazolecarboxylate esters and oxime addition products

Reaction of benzohydroximinoyl chlorides and β‐(trifluoromethyl)‐acetylenic esters: Synthesis of regioisomeric (trifluoromethyl)‐isoxazolecarboxylate esters and oxime addition products

1,2,4-oxadiazole: A Brief Review from the Literature About the Synthesis and Pharmacological Applications

N-Hydroxyurea and Acyl Nitroso Compounds as Nitroxyl (HNO) and Nitric Oxide (NO) Donors

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