Dynamic Kinetic Resolution overCinchona-Modified Platinum Catalyst: Hydrogenation of Racemic Ethyl 2-Fluoroacetoacetate

The enantioselective hydrogenation over a Cinchona alkaloid-modified supported platinum catalyst and parallel spontaneous racemization under the reaction conditions of the unreacted enantiomer of ethyl 2-fluoroacetoacetate are described. Using the appropriate reaction conditions an 82% enantiomeric excess in favor of the (2S,3R)-ethyl 2-fluoro-3-hydroxy-butanoate and a 99/1 threolerythro ratio were obtained. This novel method for producing optically enriched α-fluoro-β-hydroxy esters is the first example of dynamic kinetic resolution of a chirally labile racemic fluorinated compound over a modified heterogeneous metal catalyst carried out without using supplementary additives except the chiral modifier. The hydrogenation described here shows that the activation of the keto group of acetoacetates by one fluorine atom in the a position is also sufficient for obtaining high enantiomeric excess in the Orito reaction.