Selective monofluorination of active methylene compounds: the important role of ZnCl2 in inhibiting overfluorination

Abstract

In the presence of zinc chloride (ZnCl₂), active methylene compounds can be selectively monofluorinated at room temperature, and the undesired overfluorination (gem-difluorination) can be significantly diminished. The mechanistic study shows that ZnCl₂ plays an important role in selective monofluorination through its interaction with a Brønsted base to control the deprotonation of the starting methylene compounds over the corresponding monofluorinated products.