Direct α-fluorination of ketones using N-F reagents

The use of 1-fluoro-4-hydroxy-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Accufluor(TM) NFTh) as a fluorine atom transfer reagent and methanol as solvent enabled direct regiospecific fluorofunctionalization of the alpha-carbonyl position in ketones without prior activation of the target molecules. Methoxy or hydroxy substituted derivatives of 1-indanone, 1-tetralone and oxo derivatives of thiophene, benzo[b]thiophene, benzofuran and benzopyran were regiospecifically transformed to the corresponding alpha-fluoro, derivatives in high yield, while 2alpha-fluoro-5alpha-cholestan-3-one (28) and 16alpha-fluoro-3beta-hydroxy-5alpha-androstan-17-one (30) were regio- and stereospecifically obtained starting directly from the corresponding keto steroids.