Synthesis of 3‑Amino-3-hydroxymethyloxindoles and 3‑Hydroxy-3-hydroxymethyloxindoles by Rh₂(OAc)₄‑Catalyzed Three-Component Reactions of 3‑Diazooxindoles with Formaldehyde and Anilines or Water

Efficient Rh­(II)-catalyzed three-component reactions of 3-diazooxindoles and formaldehyde with either anilines or water were developed to give a series of substituted 3-amino-3-hydroxymethyloxindoles or 3-hydroxy-3-hydroxymethyloxindoles in good to excellent yields. In this atom- and step-economic transformation, Rh2(OAc)4-catalyzed decomposition of 3-diazooxindoles with anilines or water forms the corresponding active ammonium or oxonium ylides. Electrophilic trapping of the resulting ammonium ylides or oxonium ylides by formaldehyde in the form of formalin efficiently produces the title compounds in one step.