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

The unexpected formation of 3‐aryl‐5‐arylamino‐1,2,4‐oxadiazoles took place, when arylamidoximes reacted thermally with ethoxycarbonylmethylene(triphenyl)phosphorane. Furoxans, nitriles, ureas were also isolated suggesting aryl cyanide oxides as intermediates. 3‐Aryl‐5‐arylamino‐1,2,4‐oxadiazoles were formed via an aryl migration from the carbon atom to the nitrogen atom of the amidoxime, and the structure was further proved from the X‐ray crystal structure of the N‐(4‐bromobenzoyl) derivative.