Action de l'oxyde de benzonitrile sur les pyrazolines-2

Thermal transformation of arylamidoximes in the presence of phosphorus ylides. Unexpected formation of 3‐aryl‐5‐arylamino‐1,2,4‐oxadiazoles

“…An oxazirene intermediate of type 2 7 has also been suggested [19] to be formed during the known transformation of nitrile oxides to isocyanates, in addition to or instead of their dimerization [10] to the corresponding furoxans 3. Although the direct formation of 27 from the intermediate 2 4 seems also possible, the isolation of the furoxan 3 a is strong evidence for the prior formation of the corresponding nitrile oxide 2 6.…”

“…Concerning the latest steps of the mechanism for the formation of bis-aryloxadiazoles three possibilities were suggested: i) reaction [7] between arylnitrile and arylnitrile oxide originally formed from 2, ii) reaction [8] of nitrile oxide formed with starting amidoxime, iii) reaction [9] between the nitrile formed and the starting amidoxime. The last mechanism is supported by the fact that diarylfuroxans, always formed by further dimerization of nitrile oxides [10], has not been isolated in the reactions studied. In contrast arylnitriles were either isolated or identified in the reaction mixture.…”

Oximes of five-membered heterocyclic compounds with two heteroatoms. 1. Synthesis and structure (Review)

“…The transformation of 5-amino-4(3H)-pyrimidones 109 in the NaNO 2 /HCl system leads to the imidazole oximes 110 with yields of up to 97% [103]. In the literature there are also methods for the synthesis of the oximes of pyrazole [104][105][106][107], imidazole [104,105,108], and benzimidazole [109][110][111] derivatives by the reaction of the respective heterocycles with the halogen derivatives (or sulfates) of oximes or with nitrile oxides. For example, 5,5-dimethyl-4,5-dihydropyrazoles 111 and benzonitrile oxide give a mixture of the oximes 112 and the pyrazolooxadiazoles 113 [106].…”