Diastereoselective Synthesis of Aliphatic α,α-Difluoro-β³-Amino Esters via a Sonocatalyzed Reformatsky Reaction

(<i>R</i>)-2-Phenylglycine ethyl ester was found to be a cheap and effective auxiliary for the preparation of aliphatic α,α-difluoro-β³-amino esters via a Reformatsky reaction performed under sonication conditions. The products were obtained in good to high yield and ≥96:4 dr, thus providing a new stereoselective route to this under-represented class of compounds. A facile one-pot removal of the phenylglycine moiety and concomitant Boc protection subsequently afforded the corresponding Boc-protected β³-amino esters in excellent yield