Synthesis of fluoroalkenes via Julia and Julia-Kocienski olefination reactions

Base-Mediated Allylic Defluorinative Functionalizations of β-CF2H-1,3-enynes Enables the Construction of Terminal Monofluoroenynes

The base-mediated allylic defluorinative functionalization of β-CF2H-1,3-enynes with nucleophiles is described, affording terminal monofluoroalkenes bearing an alkynyl group in synthetically useful yields and Z/E selectivities. Importantly, the resultant Z/E mixture could be separated by flash chromatography in all cases; thus, stereoisomerically pure monofluoroenynes were obtained. Postsynthetic modifications of the synthesized monofluoroenynes were also accomplished to access diverse molecular structures. Computational studies disclosed the origin of the diastereoselectivity.

Controllable Fluorocarbon Chain Elongation: TMSCF2Br-Enabled Trifluorovinylation and Pentafluorocyclopropylation of Aldehydes

Controllable fluorocarbon chain elongation (CFCE) is a promising yet underdeveloped strategy for the well-defined synthesis of structurally novel polyfluorinated compounds. Herein, the direct and efficient trifluorovinylation and pentafluorocyclopropylation of aldehydes are described by using TMSCF2Br (TMS = trimethylsilyl) as the sole fluorocarbon source, accomplishing the goals of CFCE from C1 to C2 and from C1 to C3, respectively. The key to the success of these CFCE processes lies in the unique and diversified chemical reactivity of TMSCF2Br, which can serve as two different precursors, namely, a TMSCF2 radical precursor and a difluorocarbene precursor. Various functional groups are amenable to this new synthetic protocol, providing streamlined access to a broad range of alcohols containing trifluorovinyl or pentafluorocyclopropyl moieties from abundantly available aldehydes. The potential utility of these methods is further demonstrated by the gram-scale synthesis, derivatization, and measurement of log P values of the products.

Recent Advances in Monofluorinated Carbenes, Carbenoids, Ylides, and Related Species

The synthesis of monofluorinated compounds is of great interest because of the vast applications of organofluorine compounds. Recently, the introduction of monofluorocarbene synthons has emerged as an important strategy for the synthesis of fluorine-containing products. In contrast to direct fluorination, in which C-F bonds are formed, the use of monofluorinated carbenes and related reactive species involves C-C or C-X bond formation while delivering valuable fluorine atoms into the target structure. Owing to increased knowledge on carbon-carbon and carbon-heteroatom bond formations, monofluorinated carbenes have enormous potential for the synthesis of organofluorine compounds, which, in our opinion, has not yet been fully exploited. This review summarizes the recent advances in the synthetic applications of monofluorinated carbenes, carbenoids, ylides, and related species.

gem-Difluoroolefination of Amides

A metal-free one-pot process for the gem-difluoroolefination of amides is described. The reaction is based on interaction of generated in situ α-chloroiminium salts with difluorinated phosphorus ylide formed from difluorocarbene and triphenylphosphine. The olefination involves nucleophile-assisted dephosphorylation and proceeds within one hour at low temperature. The gem-difluoroenamines were used in further transformations leading to a variety of fluoroalkylated amines.