Synthesis of benzoylmethylpyrazolidine regioisomers on the surface of basic adsorbents: a competitive attack of crotonaldehyde at the two nitrogen atoms of 1,2-acetylphenylhydrazine

In the interaction of 5-hydroxypyrazolidines with acetophenone on the surface of basic adsorbents, regioisomeric 3-benzoylmethylpyrazolidine was formed along with expected 5-benzoylmethylpyrazolidine as a consequence of the retro-Michael degradation of the starting compounds followed by an attack of crotonaldehyde at the imide nitrogen atom.