Regio- and Chemoselective Fluorination of 1,3-Dicarbonyl Compounds

Highly regioselective α-fluorination of 1,3-dicarbonyl compounds could proceed smoothly by virtue of 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo2.2.2octane bis(tetrafluoroborate) as the fluorine source in the mixed solvent of ethanol and water. By adjusting the amount of the fluorine source and reaction time, the desired 2-fluoro- and 2,2-difluoro-1,3-dicarbonyl compounds could also be efficiently constructed with an excellent chemoselectivity. The reaction readily took place via a single electron transfer process at room temperature without any transition-metal catalyst, alkaline additive or additional oxidant and could be applicated in gram-scale synthesis, which features a convenient and practical free-radical fluorination.