Thermolysis of 3-phenyl-5-arylamino-1,2,4-oxadiazole and thiadiazole derivatives

Thermal reactions of 3-phenyl-5-arylamino-1,2,4-oxadiazoles I and II were investigated. Neat heating at ca. 250°C for 6 hours afforded H₂O, benzonitrile, arylcyanamides, arylamines, azobenzene, benzimidazole derivatives, and 3,3′-diphenyl-5,5′-bis1,2,4-oxadiazolyl]. Analogous results were obtained by the thermolysis of 3-phenyl-5-anilino-1,2,4-thiadiazole III at ca. 200°C for 2 hours. In addition to H₂S, NH₃, and HNCS, phenyl isothiocyanate and thiocarbanilide were obtained. Thermolysis of III in quinoline as a radical trap gave analogous resuLts but also 2-anilinoquinoline. A free-radical mechanism has been suggested to account for the identified products. © 1997 John Wiley & Sons, Inc.