Copper-Catalyzed Highly Stereoselective Hydrodifluoroallylation of Cyclopropenes and Alkenyl Boronates with 3,3-Difluoroallyl Sulfonium Salts?

Despite the paramount applications of organofluorine compounds in life and materials sciences, efficient strategies for stereoselectively constructing the C(sp(3))-CF2R bond at the stereogenic center remain limited. Here, we report a copper-catalyzed hydrodifluoroallylation of cyclopropenes and alkenyl boronates with 3,3-difluoroallyl sulfonium salts (DFASs). The use of DFASs overcomes the previous challenge of suppressing the reduction of fluoroalkylating reagents with M-H species. The reaction provides an array of gem-difluoroallyl cyclopropanes and borylalkanes with high efficiency and stereoselectivity under mild reaction conditions. Using chiral phosphine ligand could provide gem-difluoroallyl borylalkanes with high enantioselectivities, paving a new way for the catalytic asymmetric fluoroalkylation with ubiquitous alkenes. The advantages of this protocol are synthetic convenience, high functional group tolerance, and the synthetic versatility of the resulting gem-difluoroallyl cyclopropanes and borylalkanes. The synthetic utility of this approach has also been demonstrated by the diversified transformations of the gem-difluoroallylated products and the rapid synthesis of bioactive molecule analogs.