Rongalite-mediated sequential homologative fluorination of oxindoles en route to 3-(fluoromethyl)-3-methylindolin-2-ones.

A rongalite-mediated, transition-metal-free reductive homologative-fluorination strategy has been developed for the synthesis of 3-(fluoromethyl)-3-methylindolin-2-ones. This methodology involves the monofluoromethylation of indolin-2-one derivatives, employing rongalite as a C1-homologating reagent, and diethylaminosulfur trifluoride (DAST) as the fluorine source. The reaction proceeds under mild conditions, offering excellent yields, high selectivity, and broad functional group tolerance on oxindoles. Overall, this approach provides a practical and sustainable route for CH2F incorporation, thereby expanding the scope of fluoroalkylation chemistry and opening new avenues for the synthesis of fluorinated bioactive molecules.