Cycloadditions of nitrile oxides to amidoximes. A general synthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides.
The cycloadditions of nitrile oxides to amidoximes afford 1,2,4-oxadiazole-4-oxides, 1,2,4-oxadiazoles, nitroso carbonyl intermediates and amidoximes.
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A new method to synthesize 1,2,4-oxadiazoles by using DMTMM as condensing agent
2023, Tetrahedron LettersSynthesis and biological evaluations of novel isoxazoles and furoxan derivative as anti-inflammatory agents
2020, Bioorganic ChemistryCitation Excerpt :The furoxan 14 is obtained via stirring of 9 in toluene in the presence of TEA. A suggested mechanism due to the behavior of similar hydroxyimoyl chlorides and discussed in many reports [18,19] In a basic condition the hydroxyimoyl lose 1 mol of HCl and form the nitriloxide which added to another molecule to 9 and cyclized to form the intermediate 13 which lose another mole of HCl to get the furoxan 14 as illustrated in Scheme 2. Different isoxazoles 15a–c were prepared by the addition of the key intermediate 9 to different active methylene as acetylacetone, malononitrile or ethyl acetoacetate in alcoholic sodium ethoxide to yield 15a, 15b and 15c respectively (Scheme 3).
Substituent effect study on the experimental <sup>13</sup>C NMR chemical shifts of 3-(substituted phenyl)-3a,4,8,8a-tetrahydro-1,3-dioxepino[5,6-d] [1,2] isoxazoles
2019, Journal of Molecular StructureCitation Excerpt :Generally, isoxazole skeletons are formed by the reaction of nitrile oxides with C–C unsaturated bonds. Nitrile oxides can dimerize easily, to either 1,4,2,5-dioxadiazines or furoxans in the absence of dipolarophiles [22]. Beginning with aldoximes, chlorination and dehydrochlorination processes are carried out in a dry medium for preparation of nitrile oxide [23].
A reaction-based approach for fluorescence sensing of fluoride through cyclization of an O-acyl pyrene amidoxime derivative
2018, Sensors and Actuators, B: ChemicalCitation Excerpt :Consequently, all spectral data confirm the chemical structure of APA. 1,2,4-Oxadiazoles can be obtained by reacting O-acylated amidoximes with bases such as NaOEt or NaH at room temperature or pyridine with heating [34–38], cycloadditions of nitrile oxides to amidoximes [39–42], in solution phase and on solid support [43]. Most of these methods require harsh conditions and give poor yields.