A convenient synthesis of 3-aryl-1,2,4-oxadiazoles from ethyl acetoacetate and amidoximes under solvent-free conditions

Juliana L. L. F. Regueira, João R. de Freitas Filho


1,2,4-Oxadiazole containing compounds have attracted great attention due to their applications in material chemistry and therapeutics. Herein we report a convenient synthesis of 3-aril-[1,2,4-oxadiazol-5yl] propan-2-one (3a-d) by heating of b-ceto esters and an amidoximes without any solvent and in the absence of base. The arylamidoximes (1a-f) was synthesized in moderate and excellent yields (31- 89%) by reaction of nitrile with hydroxylamine hydrochloride in water at 25ºC. In the general synthetic strategy employed in our study is illustrated in scheme 1. The 3-aril-[1,2,4-oxadiazol-5yl] propan-2-one (3a-f) were synthesized by treatment of arylamidoxime (1a-f with b-ceto esters for 4 hour without any solvent and in the absence of base. The reaction was monitored  by TLC   (thin layer chromatography). The heterocycles (3a-f) were obtained in moderate and good yields (60-88%). The products were identified using both analytical and spectral data (IR, 1H and 13C NMR) and all compounds are in full agreement with the proposed structure.


amidoximes; 1,2,4-oxadiazoles; solvent-free

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