Abstract The available 2-benzoylamino-3, 3-dichloroacrylonitrile and its analogs when treated with excess hydrazine hydrate convert to 2-aryl-4-cyano-5-hydrazinooxazoles. The products are fairly stable in usual conditions but undergo recyclization on heating in acetic acid to give previously unknown derivatives of 2-methyl-1, 3, 4-oxadiazole with a 5- acylamino (carbamoyl) methyl substituent, whose structure was established by ...