Recyclization of N-arylitaconimides with hydrazines as a new effective synthesis of 2-(3-oxopyrazolidin-4-yl)acetanilides

Recyclization of N-arylitaconimides with hydrazine in dioxane at room temperature selectively leads to 2-(3-oxopyrazolidin- 4-yl)acetanilide derivatives in moderate to good yields. The similar reaction with phenylhydrazine proceeds with the simultaneous formation of isomeric 3- and 5-oxo- 1-phenylpyrazolidine-containing acetanilides.