Reagent-Controlled Reversal of Regioselectivity in Nucleophilic Fluorination of Spiro-epoxyoxindole: Synthesis of 3-Fluoro-3-hydroxymethyloxindole and 3-Aryl-3-fluoromethyloxindole

A convenient and metal/catalyst-free approach for the reversal of regioselectivity in nucleophilic fluorination of a wide range of spiro-epoxyoxindoles has been reported simply by altering the nucleophilic fluoride reagents. Py·(HF)x-mediated fluorination at the tertiary sp3-C center of spiro-epoxyoxindole furnishes 3-fluoro-3-hydroxymethyloxindoles, whereas TBAF-mediated fluoride addition at the primary sp3-C center renders 3-fluoromethyl-3-hydroxyoxindoles, which have been utilized for the synthesis of 3-aryl-3-fluoromethyloxindole.