Metal-Free Aminomethylation of Pyrazolones: Direct Access to 4-Aminomethylated Pyrazolones

A metal-free aminomethylation of pyrazolones is accomplished with cyclic amines such as morpholine and piperazine analogues in the presence of (diacetoxyiodo)benzene at ambient temperature. Various sensitive functional groups can be compatible under the reaction conditions. Preliminary mechanistic investigation reveals that morpholine or piperazine analogues are likely to be the source of methylene group. This method provides a straightforward route for the preparation of 4-aminomethylated pyrazolone derivatives under mild conditions.