Copper(0)-mediated tetrafluoroethylenation of various aromatic compounds

Experimental and Theoretical Studies on Cobalt-Catalyzed Regioselective Hydrosilylation of Tetrafluorinated Cyclohexa-1,3-dienes

Cyclohexa-1,3-dienes bearing a tetrafluoroethylene group underwent highly regioselective hydrosilylation in the presence of 1-10 mol % Co2(CO)8 in 1,2-dichloroethane under mild conditions (reflux, 3 h), which led to an abundant yield of homoallylsilanes. Mechanistic studies proved that the reaction proceeds as per the modified Chalk-Harrod mechanism; via DFT calculation, the reason for homoallylsilanes being exclusively obtained was demonstrated. The formal synthesis of a tetrafluorinated negative-type liquid crystal demonstrated the synthetic utility of such hydrosilylation.

Diverse Synthetic Transformations Using 4-Bromo-3,3,4,4-tetrafluorobut-1-ene and Its Applications in the Preparation of CF2 CF2 -Containing Sugars, Liquid Crystals, and Light-Emitting Materials

Organic molecules with fluoroalkylene scaffolds, especially a tetrafluoroethylene (CF2 CF2 ) moiety, in their molecular structures exhibit unique biological activities, or can be applied to functional materials such as liquid crystals and light-emitting materials. Although several methods for the syntheses of CF2 CF2 -containing organic molecules have been reported to date, they have been limited to methods using explosives and fluorinating agents. Therefore, there is an urgent need to develop simple and efficient approaches to synthesize CF2 CF2 -containing organic molecules from readily available fluorinated substrates using carbon-carbon bond formation reactions. This personal account summarizes the simple and efficient transformation of functional groups at both ends of 4-bromo-3,3,4,4-tetrafluorobut-1-ene and discusses its synthetic applications to biologically active fluorinated sugars and functional materials, such as liquid crystals and light-emitting molecules.

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

(1,1,2,2-Tetrafluorobut-3-en-1-yl)zinc bromide was prepared by insertion of the zinc–silver couple into the CF₂–Br bond of commercially available 4-bromo-3,3,4,4-tetrafluorobut-1-ene in DMF at 0 °C for 0.5 h, The resultant polyfluorinated zinc reagent was found to be thermally stable at ambient temperature and storable for at least 1.5 years in the refrigerator. This CF₂CF₂-containing organozinc reagent could be easily transmetallated to copper species, which underwent cross-coupling reactions with various aromatic iodides or acyl chlorides to produce a broad range of CF₂CF₂-containing organic molecules in good-to-excellent yields. Therefore, the zinc reagent could become a new and practical synthetic tool for producing functional molecules with a CF₂CF₂ fragment.

Rational design and synthesis of a novel laterally-tetrafluorinated tricyclic mesogen with large negative dielectric anisotropy

Guided by theoretical calculations, we predicted that 5,5,6,6-tetrafluoro-1-methoxycyclohex-1-ene, a new structural motif, exhibits a large negative dielectric anisotropy, and then developed a synthetic strategy for the preparation of the novel tetrafluorinated tricyclic mesogen in twelve reaction steps starting from a commercially available fluorinated starting material. During the evaluation of its liquid-crystalline characteristics, the tetrafluorinated mesogen was found to display low birefringence and a large negative dielectric anisotropy, confirming that its molecular structure is a reasonable design for the further development of novel mesogenic molecules with large negative dielectric anisotropies.

Synthesis of tetrafluoroethylene- and tetrafluoroethyl-containing azides and their 1,3-dipolar cycloaddition as synthetic application

Tetrafluoroethylene-containing azides are accessed in two steps (one pot) from tetrafluoroalkyl bromides by metalation and reaction with electrophilic azides. Subsequent copper(i)-catalyzed azide-alkyne cycloaddition afforded N-tetrafluoroethyl and N-tetrafluoroethylene 4-substituted 1,2,3-triazoles. In addition, the protocol for the synthesis of 4,5-disubstituted 1,2,3-triazoles is presented.

Stereochemically Defined Various Multisubstituted Alkenes Bearing a Tetrafluoroethylene (-CF2CF2-) Fragment

Highly regio- and stereoselective transformation of commercially available 4-bromo-3,3,4,4-tetrafluoro-1-butene into multisubstituted alkenes having a tetrafluoroethylene fragment through Heck reactions and/or Suzuki-Miyaura cross-coupling reactions was established. Thus, the obtained alkenes underwent a smooth reductive coupling reaction with aldehydes under the influence of MeLi/LiBr-free, affording structurally unprecedented fluorinated materials.

Nucleophilic Tetrafluoroethylation Employing in Situ Formed Organomagnesium Reagents

Tetrafluoroalkyl bromides are metalated with equimolar iPrMgCl·LiCl (Turbo Grignard) to form organomagnesium compounds which are stable at low temperatures and react with various electrophiles (aldehydes, ketones, CO₂, cyclic sulfate and sulfamidate, N-sulfonylimines, nitrone, chlorophosphate, nonaflyl azide) to afford novel functionalized tetrafluoroethylene-containing products. Ease of operation, excellent selectivity, high nucleophilicity, and enhanced stability of the reactive species together with a broad substrate scope comprise a highly attractive nucleophilic tetrafluoroethylation protocol affording unique synthetic building blocks.

Photomediated Controlled Radical Polymerization and Block Copolymerization of Vinylidene Fluoride

This review summarizes recent research on novel photochemical methods for the initiation and control of the polymerization of main chain fluorinated monomers as exemplified by vinylidene fluoride (VDF) and for the synthesis of their block copolymers. Such reactions can be carried out at ambient temperature in glass tubes using visible light. Novel, original protocols include the use of hypervalent iodide carboxylates alone or in conjunction with molecular iodine, as well as the use of photoactive transition metal carbonyls in the presence of alkyl, fluoroalkyl, and perfluoroalkyl halides. An in-depth study of the reaction parameters highlights the use of dimethyl carbonate as a preferred polymerization solvent and outlines the structure-property relationship for hypervalent iodide carboxylates and halide initiators in both the free radical and iodine degenerative transfer controlled radical polymerization (IDT-CRP) of VDF. Finally, the rational selection of metal carbonyls that are successful not only as IDT mediators but, more importantly, in the quantitative activation of both PVDF-CH2-CF2-I and PVDF-CF2-CH2-I chain ends toward the synthesis of well-defined PVDF block copolymers is presented.

Direct Catalytic Asymmetric Mannich-Type Reaction of α- and β-Fluorinated Amides

The last two decades have witnessed the emergence of direct enolization protocols providing atom-economical and operationally simple methods to use enolates for stereoselective C-C bond-forming reactions, eliminating the inherent drawback of the preformation of enolates using stoichiometric amounts of reagents. In its infancy, direct enolization relied heavily on the intrinsic acidity of the latent enolates, and the reaction scope was limited to readily enolizable ketones and aldehydes. Recent advances in this field enabled the exploitation of carboxylic acid derivatives for direct enolization, offering expeditious access to synthetically versatile chiral building blocks. Despite the growing demand for enantioenriched fluorine-containing small molecules, α- and β-fluorinated carbonyl compounds have been neglected in direct enolization chemistry because of the competing and dominating defluorination pathway. Herein we present a comprehensive study on direct and highly stereoselective Mannich-type reactions of α- and β-fluorine-functionalized 7-azaindoline amides that rely on a soft Lewis acid/hard Brønsted base cooperative catalytic system to guarantee an efficient enolization while suppressing undesired defluorination. This protocol contributes to provide a series of fluorinated analogs of enantioenriched β-amino acids for medicinal chemistry.

Cross-Coupling of [2-Aryl-1,1,2,2-tetrafluoroethyl](trimethyl)silanes with Aryl Halides

The synthesis of arylCF2CF2SiMe3 and their reactivity in cross-coupling reactions with aryl iodides and aryl bromides to afford a range of 1,1,2,2-tetrafluoro-1,2-arylethanes is reported. The use of pyridine as an alternative to phenanthroline, and the ability to carry out the reaction at 60 °C or room temperature are the key features of this Cu-Ag mediated cross-coupling methodology. The chemistry is compatible with (hetero)aryl halides, offering a platform to develop products of interest in material and medicinal chemistry.