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

Abstract

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 - n EX n (R = Ph, Et; E = C, Si, Ge, Sn, Pb; X = Cl, Br) to yield the organometalloid trifluoropropynyl compounds R4 - n E(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.

Activation of tetrafluoropropenes by rhodium(i) germyl and silyl complexes

“…The chemical shis and coupling constant values are similar to data found for olens with hydrogen atoms in a trans position such as E-CF 3 CH]CH(Bpin) and E-CF 3 CH]CH(SiPh 3 ). 3d, 23 Finally, catalytic reactions involving the silane HSi(OEt) 3 and the tetra-uoropropenes under study were performed using both [Rh{Si(OEt) 3 }(PEt 3 ) 3 ] (5) and [Rh(H)(PEt 3 ) 3 ] ( 8) as a catalyst (see Table 1). When HFO-1234yf is reacted together with HSi(OEt) 3 and 10 mol% of complex 5, generation of 3,3,3-triuoropropene and 3,3,3-triuoropropane together with small amounts of the olen Z-CF 3 CH]CH(Si(OEt) 3 ) ( 7) was observed, similar to the generation of vinyl germanes from tertiary germanes.…”

Oxidative 3,3,3-trifluoropropylation of arylaldehydes

“…On the other hand, the 2,2,2-trifluoroethylation and the 3,3,3-trifluoropropylation, which elongate the product by two and three carbon atoms, respectively, have not been explored yet. 2-Bromo-3,3,3-trifluoropropene [14–26] and 1,1,1,3,3-pentafluoropropane [27–28] have been used in place of (3,3,3-trifluoropropynyl)lithium, which can add to carbonyl compounds and couple with aryl halides through a zinc intermediate. For the 3,3,3-trifluoropropenyl synthon Yamazaki et al reported the use of 2-(trifluoromethyl)-1-(phenylsulfenyl)vinyltrimethylsilane for the addition to aldehydes in the presence of fluoride anion [29].…”

Non-Deprotonating Methodologies for Organolithium Reagents Starting from Non-Halogenated Materials. Part 2: Transmetallation and Addition to Multiple Bonds

“…Different organolithium reagents gave addition to the trifluoropropynyl derivatives 204 at low temperature producing the corresponding alkenes 205 as single (E)-diastereomers (Scheme 51). In contrast, when the reaction was performed at room temperature, a mixture of both isomers was obtained [126]. A mixture of 204 and tert-butyllithium in THF heated up to reflux gave the expected addition followed by cyclisation via a lithium fluoride elimination, producing gem-difluorocyclopropenyl compounds 206.…”