A Novel Diastereoselective Synthesis of (Z)-Fluoroalkenes via a Nozaki−Hiyama−Kishi-Type Reaction

Electrocatalysis-Enabled Defluorinative Cross-Coupling of gem-Difluoroalkenes with Aldehydes and Ketones

An electrochemical defluorinative cross-coupling of gem-difluoroalkenes with carbonyl compounds was described, by which highly stereoselective monofluoroalkene allyl alcohols were synthesized. The reaction tolerates a broad range of functional groups and has successfully been applied to synthesize complex molecules. Mechanistic studies indicate that the reaction starts from electron reduction of gem-difluoroalkenes to generate radical negative ions, which undergo β-fluoride elimination and subsequent reduction to form anions. These anions are subsequently trapped by carbonyl compounds to furnish target products.

Iron-catalyzed decarboxylative and oxidative decarbonylative cross-coupling: a new strategy for the synthesis of monofluoroalkenes

Herein, an iron(ii)-catalyzed decarboxylative and oxidative decarbonylative cross-coupling of α-fluoro cinnamic acids with aliphatic aldehydes is presented.

Copper-catalyzed direct monofluoroalkenylation of C(sp3)–H bonds via decarboxylation of α-fluoroacrylic acids

Herein, a protocol for the copper-catalyzed direct monofluoroalkenylation of C(sp3)–H bonds is reported.

Ruthenium(ii)-catalyzed α-fluoroalkenylation of arenes via C–H bond activation and C–F bond cleavage

1,2-Diaryl-substituted monofluoroalkenes with good regio-and stereo-selectivities were achieved through C–H activation by a Ru(ii)-catalyst.

Synthesis of monofluoroalkenes through selective hydrodefluorination of gem-difluoroalkenes with Red-Al®

A practical approach for the selective hydrodefluorination of gem-difluoroalkenes using Red-Al® as reductant at room temperature in CH₂Cl₂ was reported. Monofluoroalkenes were obtained in moderate to high yields with good E-selectivity.

Transition-metal-free carbofluorination of TBS-protected nitrogen-containing cyclic enynols: synthesis of fluorinated azabicycles

The synthesis of fluorinated azabicycles from tert-butyldimethylsilyl-protected N-containing cyclic enynols using inexpensive BF3·OEt2 is described. In this reaction, BF3 reacts as both the Lewis acid and the fluoride source for cyclization/fluorination of the TBS-protected cyclic N-containing enynols. The method provides an easy access to fluorinated azabicycles where a new C(sp(2))-F bond and a new bicyclic skeleton are generated at ambient temperature within 1-13 min under metal-free reaction conditions.

Stereoselective synthesis of mono-fluoroalkenes

Recent developments in the stereoselective synthesis of fluoroalkenes, which include hydrofluorination of alkyne, fluorination of alkenylmetal, condensation methods, dehydrofluorination of gem-difluoro compounds, and a cross-coupling reaction using fluorohaloalkenes or fluoroalkenylmetal, are described in this chapter.

One-pot multicomponent coupling methods for the synthesis of diastereo- and enantioenriched (Z)-trisubstituted allylic alcohols

(Z)-trisubstituted allylic alcohols are widespread structural motifs in natural products and biologically active compounds but are difficult to directly prepare. Introduced herein is a general one-pot multicomponent coupling method for the synthesis of (Z)-alpha,alpha,beta-trisubstituted allylic alcohols. (Z)-trisubstituted vinylzinc reagents are formed in situ by initial hydroboration of 1-bromo-1-alkynes. Addition of dialkylzinc reagents induces a 1,2-metalate rearrangement that is followed by a boron-to-zinc transmetalation. The resulting vinylzinc reagents add to a variety of prochiral aldehydes to produce racemic (Z)-trisubstituted allylic alcohols. When enantioenriched aldehyde substrates are employed, (Z)-trisubstituted allylic alcohols are isolated with high dr (>20:1 in many cases). For example, vinylation of enantioenriched benzyl-protected alpha- and beta-hydroxy propanal derivatives furnished the expected anti-Felkin addition products via chelation control. Surprisingly, silyl-protected alpha-hydroxy aldehydes also afford anti-Felkin addition products. A protocol for the catalytic asymmetric addition of (Z)-trisubstituted vinylzinc reagents to prochiral aldehydes with a (-)-MIB-based catalyst has also been developed. Several additives were investigated as inhibitors of the Lewis acidic alkylzinc halide byproducts, which promote the background reaction to form the racemate. Alpha-ethyl and alpha-cyclohexyl (Z)-trisubstituted allylic alcohols can now be synthesized with excellent levels of enantioselectivity in the presence of diamine inhibitors.

Modified Julia fluoroolefination: selective preparation of fluoroalkenoates

The modified Julia olefination reaction has been applied to develop a stereoselective synthesis of fluoroalkenoate derivatives from a fluorobenzothiazolyl sulfone and aldehydes or a ketone. The olefination reaction can be achieved by using a variety of bases. DBU and DBU in the presence of MgBr2 were found to be the most efficient systems to prepare either (Z)- or (E)-alkenoates in moderate to excellent stereoselectivity.

Chiral dipeptide mimics possessing a fluoroolefin moiety: a relevant tool for conformational and medicinal studies

The replacement of the amide bond in a peptide backbone is a promising strategy in peptidomimetic drug research. Over the various amide bond surrogates, the fluoroolefin moiety has been successfully developed as an effective mimic. Today, fluorine-containing compounds account for a large proportion of new active molecules in life sciences. The synthesis of fluoroolefin peptide mimics is not a trivial task and innovative approaches often need to be addressed, in particular for the stereocontrol of the double bond configuration and the chiral centres adjacent to the fluoroalkene. These fluorinated peptidomimetics have been synthesised and evaluated as metabolically stable and/or conformationally constrained analogs of enzyme inhibitors, and as tools for probing the function, structure, and binding process of receptors.

First Stereospecific Synthesis of (E)- or (Z)-α-Fluoroenones via a Kinetically Controlled Negishi Coupling Reaction

A highly stereospecific synthesis of (E)- or (Z)-alpha-fluoro-alpha,beta-unsaturated ketones 4, via a kinetically controlled Negishi palladium-catalyzed coupling reaction, was developed, providing an easy and general access to valuable fluorinated intermediates (pharmaceutical, peptide mimic, and so on). The synthesis involved a reaction between E/Z gem-bromofluoroolefins 2 and alkoxyvinylzinc species 6 under controlled reaction temperature. At 10 degrees C, (Z)-4 (70 to 99% yields) was obtained along with unreacted (Z)-2 (66 to 99% yields). At THF reflux, the recovered olefin was transformed into (E)-4 (up to 98% yield).