Mononuclear isoheterocyclic rearrangements. Note I. Interconversion of 3‐benzoylamino‐5‐methyl‐1,2,4‐oxadiazole and 3‐acetylamino‐5‐phenyl‐1,2,4‐oxadiazole

The first example of mononuclear isoheterocyclic rearrangement is reported. The 3‐benzoylamino‐5‐methyl‐1,2,4‐oxadiazole (5) furnishes through a reversible process (slowly at room temperature in methanol, acetone or dioxane, fast in DMSO or in methanol in the presence of strong bases) a mixture of 5 and 3‐acethylamino‐5‐phenyl‐1,2,4‐oxadiazole (6). The equilibrium process can be achieved also by heating 5 at 181° and the same reaction mixture can be obtained using 6 as the starting material. 3‐Trichloroacetylamino‐5‐methyl‐1,2,4‐oxadiazole (7) was unaffected by similar treatment. The results obtained are discussed.