1-Trifluoromethylvinylsilane as a CF₂C^-−CH₂⁺ Synthon:  Synthesis of Functionalized 1,1-Difluoro-1-alkenes via Isolable 2,2-Difluorovinylsilanes

Abstract

Various 1,1-difluoro-1-alkenes such as monosubstituted 1,1-difluoro-1-alkenes, 2-bromo-1,1-difluoro-1-alkenes, and 3,3-difluoroallylic alcohols are synthesized in two simple steps from 1-trifluoromethylvinylsilane: (i) its SN2' reaction with nucleophiles to construct 2,2-difluorovinylsilanes and (ii) the subsequent substitution of electrophiles for the vinylic silyl group. The combination of these two processes allows a one-pot synthesis of the functionalized 1,1-difluoro-1-alkenes starting from 1-trifluoromethylvinylsilane, which functions as a CF2=C(-)-CH2+ synthon.

Substitution of Two Fluorine Atoms in a Trifluoromethyl Group: Regioselective Synthesis of 3‐Fluoropyrazoles

“…Synthesis of 4‐unsubstituted 3‐fluoropyrazoles was also accomplished by using 2‐silylated trifluoromethylalkenes (Scheme ). Although the parent, 2‐unsubstituted 3,3,3‐trifluoropropene was not a suitable substrate for the S N 2′‐type reaction with hydrazines,17 2‐silylated trifluoropropene 1 e was readily subjected to S N 2′‐type reactions with Boc‐ and phenylhydrazines, 2 a and 2 b 3a. Desilylation occurred during cyclization to give 3‐fluoropyrazoles 7 i and 7 j in high yields.…”

2,2‐Difluorovinyl Pinacolborane – A New Versatile Reagent for the Suzuki–Miyaura Reaction

“…Apart from that, gem ‐difluorinated alkenes (in particular, gem ‐difluorostyrenes) are of great value for organic synthesis since they can be straightforward precursors of other fluorinated compounds (e.g. monofluorinated alkenes, di‐ and trifluoromethyl‐substituted compounds, fluorinated heterocycles, fluorinated vinylsilanes, as well as polymers) . Hence efficient methods for the preparation of gem ‐difluorostyrenes are of high request.…”

Single C(sp3)–F Bond Activation in a CF3 Group: Ipso-Defluorooxylation of (Trifluoromethyl)alkenes with Oximes

“…(Trifluoromethyl)­alkenes are readily available substrates that have been successfully utilized in the transformations of C­(sp 3 )–F bonds activation in a CF 3 group. ,− Cleavage of a C­(sp 3 )–F bond in (trifluoromethyl)­alkenes can be accomplished using anionic S N 2′-type substitution (Scheme a), Lewis acid promoted cationic S N 1′-type substitution (Scheme b), transition-metal-catalyzed defluorinative functionalization (Scheme c), and photocatalysis via radical-polar crossover (Scheme d) . Intrinsically, the attached trifluoromethyl group lowers the LUMO of the double bond in the (trifluoromethyl)­alkene.…”