Asymmetric Transfer Hydrogenation Ofgem-Difluorocyclopropenyl Esters: Access To Enantioenrichedgem-Difluorocyclopropanes

Catalytic enantioselective access to disubstituted functionalizedgem-difluorocyclopropanes, which are emerging fluorinated motifs of interest in medicinal chemistry, was achieved through asymmetric transfer hydrogenation ofgem-difluorocyclopropenyl esters, catalyzed by a Noyori-Ikariya (p-cymene)-ruthenium(II) complex, with (N-tosyl-1,2-diphenylethylenediamine) as the chiral ligand and isopropanol as the hydrogen donor. The resultingcis-gem-difluorocyclopropyl esters were obtained with moderate to high enantioselectivity (ee=66-99 %), and post-functionalization reactions enable access to valuable building blocks incorporating acis- ortrans-gem-difluorocyclopropyl motif.