Synthesis of Chiral α,α-Difluoro-β-hydroxy Esters by Enantioselective Reformatsky Reaction

The addition of the Reformatsky reagent generated from ethyl bromo-α,α-difluoroacetate to aldehydes, in the presence of chiral amino alcohols, yields α,α-difluoro-β-hydroxy esters with good enantiomeric excess (ee) for aromatic aldehydes or modest ee for aliphatic ones. (1S,2R)-Ephedrine derivatives are better chiral inductors than (1S,2R)-dibutylnorephedrine, whereas the enantiodifferentiation is also affected by the molar ratio of the reactants. The best results are obtained from a molar ratio aldehyde/Reformatsky reagent/amino alcohol: 1/4/1.

enantioselective Reformatsky reaction - α,α-difluoro-β-hydroxy esters - chiral ligands enantioselective synthesis - chiral 1,2-amino alcohols