Anodic fluorination of various N-acetyl-3-substituted indole derivatives was successfully carried out in Et4NF-4HF/MeCN to provide the corresponding trans-2, 3-difluoro-2, 3- dihydroindoles exclusively or selectively. Treatment of difluorinated products with a base provided monofluoroindole derivatives or monofluoroindoline derivative depending on the substituents at the 3-position.
