Enantioselective synthesis of α,α-difluoro-β-amino acid and 3,3- difluoroazetidin-2-one via the reformatsky-type reaction of ethyl bromodifluoroacetate with chiral 1,3-oxazolidines

Article abstract of DOI:10.1021/jo990868b

Chiral oxazolidines 2a-e can be diastereoselectively alkylated with BrCF₂CO₂Et to furnish 3,3-difluoroazetidin-2-ones 3a-e with up to 99% de. Selective cleavage of the chiral appendage provided the corresponding unsubstituted azetidinones. Formation of optically pure α,α-difluoro-β- amino acids 5a-c can be achieved by acidic hydrolysis of N-vinyl-azetidin-2- ones.