Solvent- and Catalyst-Free Synthesis of gem-Difluorinated and Polyfluoroarylated Compounds with Nucleophilic or Electrophilic Fluorine-Containing Reaction Partners, Respectively

A novel, efficient and environmentally friendly solvent-free and catalyst-free approach for the synthesis of structurally diverse gem-difluorinated and polyfluoroarylated derivatives with readily available nucleophilic and electrophilic fluorine-containing reaction partners, difluoroenoxysilane and pentafluorobenzaldehyde, is described. This neat protocol is induced by the direct hydrogen-bond interactions between fluorinated and non-fluorinated reactants without the use of heavy metal catalysts or volatile organic solvents and with no need for column chromatographic separation for most cases.

Enantioselective Cu-Catalyzed Nucleophilic Substitutions of Polyfluoroarenes: Synthesis of Chiral Polyfluoroaryl Diarylmethanes

Optically pure diarylmethanes are frequently presented in pharmaceuticals and bioactive molecules. However, minor efforts have been devoted to chiral polyfluoroarene-containing diarylmethanes, and their synthesis is still challenging. Herein, we describe an enantioselective Cu/sulfoxide phosphine (SOP) catalyzed nucleophilic substitution reaction by using polyfluoroarenes as the polyfluoroaryl reagent. Under mild conditions, this protocol enables the efficient synthesis of chiral polyfluoroaryl diarylmethanes with fluorinated quaternary stereogenic center in good yields (up to 93%), high regioselectivties, and excellent enantioselectivities (up to 99% ee). Moreover, gram-scale experiments, product derivations, and late-stage diversifications were performed to demonstrate the utility of this method.

Visible-light-induced selective defluoroalkylations of polyfluoroarenes with alcohols

To provide α-polyfluoroarylalcohols, a novel protocol for the selective defluoroalkylation of polyfluoroarenes with easily accessible alcohols was reported via the cooperation of photoredox and hydrogen atom transfer (HAT) strategies with the assistance of Lewis acids under visible light irradiation. The protocol featured broad scope, excellent regioselectivity for both C-H and C-F bond cleavages, and mild conditions. Mechanistic studies suggested that the reaction occurred through Lewis acid-promoted HAT to provide an alkyl radical and sequential addition to polyfluoroarenes. Impressively, the regioselectivity for C-F cleavage was verified with the Fukui function. The feasibility and application of this protocol on fluoroarene synthesis were well illustrated by gram-scale synthesis under both batch and flow conditions, late-stage decoration of bioactive compounds, and further transformations of the fluoroarylalcohols.

Transition Metal Catalyst-Free, Base-Promoted 1,2-Additions of Polyfluorophenylboronates to Aldehydes and Ketones

A novel protocol for the transition metal-free 1,2-addition of polyfluoroaryl boronate esters to aldehydes and ketones is reported, which provides secondary alcohols, tertiary alcohols, and ketones. Control experiments and DFT calculations indicate that both the ortho-F substituents on the polyfluorophenyl boronates and the counterion K+ in the carbonate base are critical. The distinguishing features of this procedure include the employment of commercially available starting materials and the broad scope of the reaction with a wide variety of carbonyl compounds giving moderate to excellent yields. Intriguing structural features involving O-H⋅⋅⋅O and O-H⋅⋅⋅N hydrogen bonding, as well as arene-perfluoroarene interactions, in this series of racemic polyfluoroaryl carbinols have also been addressed.

Reactions of Bifunctional Perfluoroarylsilanes with Activated C-F Bonds in Perfluorinated Arenes

Reactions of bifunctional perfluoroarylsilanes, p- and m-C₆F₄(SiMe₃)₂ as well as o-BrC₆F₄SiMe₃, with substituted perfluoroarenes having electron-withdrawing groups were investigated using NMR and density functional theory calculation techniques. The C-F bond in perfluoroarenes was activated by the para-position of an electron-withdrawing group, such as CF₃, C₆F₅, CN, and NO₂. The reaction of C₆F₄(SiMe₃)₂ mainly occurred at the para-position of the perfluoroarenes and also occurred at the ortho-position of C₆F₅CN and C₆F₅NO₂. Two equivalent reactions of perfluoroarenes with bifunctional p- and m-C₆F₄(SiMe₃)₂ provided disubstituted perfluoroarenes, along with a small amount of protonated monosubstituted perfluoroarenes. The reaction of o-BrC₆F₄SiMe₃ with the CF₃- and CN-substituted pentafluorobenzenes provided unexpected coupling products between C-Br and C-F bonds, in addition to the coupling products between C-SiMe₃ and C-F bonds.

Nucleophilic fluoroalkylation/cyclization route to fluorinated phthalides

Discribed in this article is a versatile and practical method for the synthesis of C3-perfluoroalkyl-substituted phthalides in a one-pot manner. Upon treatment of KF or triethylamine, 2-cyanobenzaldehyde reacted with (perfluoroalkyl)trimethylsilanes via nucleophilic addition and subsequent intramolecular cyclization to give perfluoroalkylphthalides in good yields.