3-Acetylamino-5-aryl-1.2,4-oxadiazoles

Little interest has been shown this year in the photochemistry of five-membered heteroaromatic compounds. A theoretical study of the photoisomerization of 2-cyanopyrrole to 3-cyanopyrrole has been described.The formation of 2-acetyl-aminoquinazolin-4-ones on irradiation of 3-acetylamino-5-aryl-1,2,4-oxadiazoles (45) in methanol is thought to involve initial rearrangement to the corresponding 3-aroylamino-5-methyl-l,2,4-... 

It was shown that furoxans can be transformed to 1,2,3-triazoles. Thus, 4-acetylamino-3-arylazo-l,2,5-oxadiazole 2-oxides undergo two successive (cascade) mononuclear heterocyclic rearrangements in an aqueous basic medium with the formation of 4-acetylamino-2-aryl-5-nitro-2/7-l,2,3-triazoles (Equation 12) <2001MC230>, or 3,3 -disubsti-tuted 4,4 -azo-l,2,5-oxadiazole 2-oxides were found to undergo a rearrangement into 2-(furoxan-4-yl)-4-nitro-2//-1,2,3-triazole 1-oxides on heating in pertrifluoroacetic or peracetic acids (Equation 13) <2003MC272>. 

Buscemi, S., Macaluso, G., and Vivona, N., Heterocyclic photorearrangements — photochemical behavior of some 3-acetylamino-5-aryl-l,2,4-oxadiazoles. A photoinduced iso-heterocydic rearrangement, Heterocycles, 29,1301, 1989. 

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