Preparation and Functionalization of a Range of Main-Group Trifluoropropynyl Organometallic Compounds: The Application of Metalloid-Directed Carbolithiation to the Selective Synthesis of Novel Fluorocarbon Fragments

The reaction of 1,1,1,3,3-pentafluoropropane (CF3CH2CF2H, HFC-245fa) with 3 equiv of
n-butyllithium at −10 °C leads to the generation of trifluoropropynyllithium in excellent
yields. This reagent reacts readily with a range of group 14 electrophiles R4-nEXn (R = Ph,
Et; E = C, Si, Ge, Sn, Pb; X = Cl, Br) to yield the organometalloid trifluoropropynyl
compounds R4-nE(C⋮CCF3)n. Three of these compounds, Ph3EC⋮CCF3 (E = C, Si, Ge), have
been crystallographically characterized, representing the first such study of these materials.
The silane Ph3SiC⋮CCF3 has been derivatized by reaction with LiAlH4 and a range of
organolithium reagents (RLi, R = n-Bu, Ph, t-Bu) to afford a new series of β-CF3-substituted
vinylsilanes of the type Ph3SiCHC(CF3)R, with predominantly E geometry at the double
bond. In the cases R = n-Bu, t-Bu, and Ph, these materials have been crystallographically
characterized. Additionally, a remarkably facile cyclization pathway for Ph3SiC⋮CCF3,
initiated by t-BuLi, that yields the respective gem-difluorocyclopropene has been explored
and is described in detail, along with its extension to a number of other systems.