Journal of the American Chemical Society, Vol.127, No.24, 8826-8828, 2005
Enantioselective organocatalytic alpha-fluorination of aldehydes
The first direct enantioselective catalytic alpha-fluorination of aldehydes has been accomplished. The use of enamine catalysis has provided a new organocatalytic strategy for the enantioselective fluorination of aldehydes to generate a-fluoro aldehydes, an important chiral synthon for medicinal agent synthesis. The use of imidazolidinone 1 as the asymmetric catalyst has been found to mediate the fluorination of a large variety of aldehyde substrates with N-fluorobenzenesulfonimide serving as the electrophilic source of fluorine. A diverse spectrum of aldehyde substrates can also be accommodated in this new organocatalytic transformation. While catalyst quantities of 20 mol % were generally employed in this study, successful halogenation can be accomplished using catalyst loadings as low as 2.5 mol %.