Hydrodefluorinations of trifluorotoluenes by LiAlH4 and TiCl4

Exhaustive Hydrodefluorination or Deuterodefluorination of Trifluoromethylarenes via Metal-Free Photoredox Catalysis

Perfluoroalkyl compounds are persistent environmental pollutants due to their chemical and thermal stability. Hydrodefluorination is one of the most promising strategies for the disposal of fluorine-containing compounds, which has attracted much attention from a broad spectrum of scientific communities. Herein, we disclose a metal-free, visible-light-promoted protocol for the exhaustive hydrodefluorination of a wide variety of trifluoromethylarenes with up to 95% yields. Moreover, methyl-d3 groups can be obtained via deuterium water with a D ratio of up to 94%.

C-F Transformations of Benzotrifluorides by the Activation of Ortho-Hydrosilyl Group

Single C-F transformations of aromatic trifluoromethyl compounds are challenging issues due to the strong C-F bond. We have recently developed selective methods for single C-F transformations such as allylation of o-hydrosilyl-substituted benzotrifluorides through the hydride abstraction with trityl cations. Single C-F thiolation and azidation of o-(hydrosilyl)benzotrifluorides were achieved using trityl sulfides and trityl azide catalyzed by Yb(OTf)3 . Treatment of o-(hydrosilyl)benzotrifluorides with trityl chloride resulted in single C-F chlorination. The resulting fluorosilyl group served in further transformations including protonation, halogenation, and Hiyama cross-coupling with C-Si cleavage. We also synthesized benzyl fluorides by LiAlH4 -reduction of the resulting fluorosilanes and further C-F transformations. These methods enabled us to prepare a broad range of organofluorines from simple benzotrifluorides through C-F and C-Si transformations.

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.

Palladium-catalyzed selective defluorinative arylation for the efficient stereospecific synthesis of (E)-β-fluoroacrylamides

A practical and efficient method for the synthesis of (E)-β-fluoroacrylamides was developed by the selective defluorinative arylation of trifluoropropanamides with arylboronic acids.

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.

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.

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.

Competing reaction pathways of 3,3,3-trifluoropropene at rhodium hydrido, silyl and germyl complexes: C–F bond activation versus hydrogermylation

The reactivity of the Rh complexes [Rh(L)(PEt₃)₃] (L = H, Si(OEt)₃, GePh₃) towards CH₂CHCF₃ was investigated which involve C–F bond activation and germylation reactions.

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.