gem-Difluoroolefin synthesis: general methods via thermostable difluorovinylmetals starting from 2,2,2-trifluoroethanol derivatives

gem-Difluoroolefins with a wide range of substituents are readily synthesized from commercially available 2,2,2-trifluoroethyl p-toluenesulfonate, via a pathway that comprises the following two processes: (i) a boron-mediated alkylation leading to gem-difluorovinylborane, and (ii) subsequent direct functionalizations via gem-difluorovinylcopper. This methodology provides a general one-pot synthesis of unsymmetrically disubstituted difluoroolefins by the introduction of difluorovinylidene unit as an ambiphile (CF2C−+). α-Nonsubstituted difluorovinylzirconocene and -zinc generated in situ from 2,2-difluorovinyl p-toluenesulfonate opens a complementary way to the synthesis of monosubstituted gem-difluoroolefins bearing unsaturated carbon substituents. These difluorovinylmetals (B, Cu, Zr, Zn) are all remarkably thermostable against β-elimination in spite of the absence of electron-withdrawing groups, and are therefore easy to handle and react readily.