Transformation of Trifluorotoluenes Triggered by Titanium(IV) Chloride-Catalyzed Hydrodefluorination using Hydrosilanes

Poly(vinyl chloride) Dechlorination Catalyzed by Zirconium

Poly(vinyl chloride) undergoes dechlorination in the presence of triethylsilane (Et3SiH) and a catalytic amount of [Cp2Zr(NPh2)][CH3B(C6F5)3] (1 b) at 40-80 °C, with up to 91 % efficiency. Stoichiometric reactivity studies conducted on cyclohexyl chloride as a model suggest that 1 b dechlorinates PVC by initial chloride abstraction, followed by hydride transfer to the cationic PVC chain from Et3SiH. Consumer items such as pipe fitting, vinyl disc or electric cable insulation undergo either dechlorination or hydrosilylation of the carbonyl-containing copolymer (polyvinyl acetate) or plasticizer (phthalate).

Electrochemical C-F bond activation of trifluoromethylarenes using silylium ions

We report a mild, electrochemical trihydrodefluorination (e-THDF) for breaking highly stable C-F bonds in trifluoromethyl arenes to form the corresponding methyl arene products. Uniquely, this "green" approach relies on the in situ generation of Lewis acidic silyl cations that mediate fluoride abstraction. Overall, e-THDF has significantly improved functional group tolerance over current methods and should inspire the continued development of defluorinative processes.

Nickel-Catalyzed Exhaustive Hydrodefluorination of Perfluoroalkyl Arenes

Perfluoroalkyl compounds are persistent environmental pollutants due to their strong C(sp³)-F bonds. Hydrodefluorination has emerged as a potential alternative disposal method for perfluoroalkyl compounds. Although the transformation of trifluoromethyl arenes into the corresponding methyl arenes has been studied by several research groups, hydrodefluorination reactions of longer perfluoroalkyl chains remain rare. Herein, we report exhaustive hydrodefluorination reactions of pentafluoroethyl arenes and longer-chain analogues using molecular nickel catalysis. Despite the cleavage of multiple C(sp³)-F bonds, the reaction already proceeds upon gentle heating (60 °C). A mechanistic investigation indicated that the reaction proceeds via benzylic hydrodefluorination reactions followed by homobenzylic ones. We reveal the multiple roles of the Ni catalyst, which include C-F bond cleavage, promotion of HF elimination, and hydrosilylation.

Bond Energy Enabled Amines Distinguishing: Chemo-, Regioselective 1,3-Diamination of (Trifluoromethyl)alkenes with Different Amines by Two C(sp3)-F Bonds Cleavage

The methods to distinguish different amines are rarely investigated. In this manuscript, a bond energy enabled amines distinguishing strategy is reported. With (trifluoromethyl)alkenes as linchpins, a chemo-, regioselective three-component defluorinative...

Two C(sp3)-F Bond Activation in a CF3 Group: ipso-Defluorinative Amination Triggered 1,3-Diamination of (Trifluoromethyl)alkenes with Indoles, Carbazoles, Pyrroles, and Sulfonamides

A novel strategy enabled cleavage of two C(sp³)-F bonds in a CF₃ group is reported. Triggered by ipso-defluorinative amination, this 1,3-diamination of (trifluoromethyl)alkenes with indoles, carbazoles, pyrroles, and sulfonamides gave acyclic 1,3-diamine products bearing a monofluoroalkene moiety in high yields with good to excellent Z/E selectivities. Preliminary mechanistic studies enable the isolation of the reaction intermediate and indicate that a unique sequential ipso-/γ-selective defluorinative amination pathway is involved in this transformation.

Hydrodehalogenation of organohalides by Et3SiH catalysed by group 4 metal complexes and B(C6F5)3

The use of the Et₃SiH/B(C₆F₅)₃ system for the activation of group 4 metal catalysts allows the efficient and selective catalytic hydrodefluorination of trifluorotoluenes.

Palladium-catalyzed selective defluorinative sulfenylation for the synthesis of fluorovinylthioethers

An efficient transformation of trifluoromethylated benzyl bromides to monofluoroalkenes through Pd-catalyzed selective defluorinative sulfenylation is described.

Picking One out of Three: Selective Single C-F Activation in Trifluoromethyl Groups

The introduction of a trifluoromethyl (CF₃ ) group into an organic molecule can modify its chemical behavior and lead to changes in its physicochemical and pharmacological properties. The CF₃ group is often chosen for its chemical inertness and stability, which are related to the strong C-F bonds. In recent years, the potential of gaining straightforward access to difluorinated compounds through selective single C-F activation in CF₃ groups has been unveiled. This review describes the latest methodologies for the synthesis of difluoromethylated arenes, difluoroalkenes and difluorinated aldol products of potential synthetic and/or biological interest, employing low-valent metals, transition metal catalysis, FLP and Lewis acid mediated transformations as well as photoredox catalysis.

Activation of C–F bonds α to C–C multiple bonds

A closer look is given to the successful approaches to the C(sp³)–F activation of benzylic, allylic, propargylic and allenylic fluorides.

Domino C-F Bond Activation of the CF3 Group: Synthesis of Fluorinated Dibenzo[a,c][7]annulenes from 2-(Trifluoromethyl)-1-alkenes and 2,2'-Diceriobiaryls

The construction of ring-fluorinated seven-membered carbocycles was readily achieved via the domino S_N2'-type/S_NV reaction between 2-(trifluoromethyl)-1-alkenes and 1,4-carbodianions. The S_N2'-type reaction of 2-(trifluoromethyl)-1-alkenes with 2,2'-diceriobiaryls generated the intermediary 1,1-difluoro-1-alkenes bearing a monoceriobiaryl moiety, which in turn underwent intramolecular S_NV reaction to afford fluorinated 5H-dibenzo[a,c][7]annulenes.

Niobium(v)-catalyzed defluorinative triallylation of α,α,α-trifluorotoluene derivatives by triple C–F bond activation

The conjugation between the carbocation center and the adjacent fluorine atoms worked effectively in the cascade defluorinative triallylation of α,α,α-trifluorotoluene derivatives.