Trifluoroacetic acid-promoted synthesis of 3-hydroxy, 3-amino and spirooxindoles from α-keto-N-anilides.
Résumé
Ketoanilides containing alkyl side chains were readily cyclized to 3-hydroxy-2-oxindoles or spirooxindoles by a single or double intramolecular Friedel-Crafts reaction in the presence of trifluoroacetic acid (TFA) at room temperature or at 45 °C. α-Iminocarboxamides, generated in situ from ketoamides, cyclized similarly to 3-aminooxindoles under identical conditions.