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

摘要

The reaction of 1,1,1,3,3-pentafluoropropane (CF3CH2CF2H, HFC-245fa) with 3 equiv of n-butyllithium. at -10 degreesC 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, Ph; X = Cl, Br) to yield the organometalloid trifluoropropynyl compounds R4-nE(Cequivalent toCCF(3))(n). Three of these compounds, Ph(3)ECequivalent toCCF(3) (E = C, Si, Ge), have been crystallographically characterized, representing the first such study of these materials. The silane Ph(3)SiCequivalent toCCF(3) 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 beta-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 Ph(3)SiCequivalent toCCF(3), 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. [References: 44]