Difluoromethylation of Alkyl Bromides and Iodides with TMSCF2H

Nickel-catalyzed reductive cross-coupling of difluoromethylated secondary alkyl bromides with organohalides

We present a highly efficient and versatile nickel-catalyzed protocol for the reductive cross-coupling of unactivated CF2H-substituted electrophiles with a wide variety of aryl and alkenyl halides. This novel approach offers high catalytic reactivity and broad functional group compatibility, enabling late-stage fluoroalkylation of drug molecules.

Synthesis of Fluoromethylated Chromones and Their Heteroatom Analogues via Sodium Fluoromethanesulfinate-Enabled Direct Fluoromethylation

An array of biologically interesting tri/difluoromethylated chromones and their heteroatom analogues were conveniently synthesized from the reaction of chromones and their heteroatom analogues with CF3SO2Na or HCF2SO2Na in the presence of tert-butyl hydroperoxide under mild conditions. A mechanistic pathway involving the generation of the electrophilic tri/difluoromethyl radical, followed with the radical substitution of chromones and their heteroatom analogues, was postulated.

Oxidant- and Base-Free, Copper-Catalyzed Difluoromethylation of Haloalkynes

We report herein a highly efficient copper-catalyzed protocol for the transformation of haloalkynes to the corresponding difluoromethylated alkynes. This scalable protocol exhibits a broad substrate scope and excellent functional group tolerance, enabling the late-stage difluoromethylation of bioactive molecules. Additionally, the strategy of utilizing the difluoromethylalkynes in gram-scale reactions and multiple transformations has proven to be highly valuable in synthetic chemistry.

Divergent Construction of Thiochromanes and N-Arylbutanamides via Arylthiodifluoromethyl Radical-Triggered Cascade of Alkenes

A strategy utilizing silver-catalyzed oxidative decarboxylation radical cascade cyclization of arylthiodifluoroacetic acids with alkenes for the simple and efficient preparation of difluoromethylated thiochromanes and 2,2-disubstituted-N-arylbutanamides derivatives has been developed. This approach includes good functional group tolerance, easily accessible starting materials, and operational simplicity.

Adaptive Planar Chirality of Pillar[5]arenes Invertible by n-Alkane Lengths

Chirality of host molecules can be induced and/or inverted by the guest molecules. However, the adapting chirality of hosts to the length of n-alkanes remains a great challenge because n-alkanes are neutral, achiral, and linear molecules, resulting in a weak interaction with most compounds. Herein, we report a system with chirality adapted to n-alkane lengths, using a pillar[5]arene-based macrocyclic host, S-Br, which contains five stereogenic carbons and five terminal bromine atoms on each rim. The electron-rich cavity of S-Br could include n-alkanes and the planar-chiral isomers sensitively inverted in response to the lengths of the complexed n-alkanes. The inclusion of a short n-alkane such as n-pentane made S-Br more inclined to be in the pS-form, whereas the inclusion of long n-alkanes such as n-heptane made the pR-form more favorable. The difference in the stability of the isomers was supported by the crystal structures and the theoretical calculations. Furthermore, temperature drives the adaptive chirality of S-Br with n-alkanes. An n-alkane with middle length, n-hexane, showed the dominance of the pR-form of S-Br at a higher temperature, whereas the pS-form was shown at a lower temperature.

Copper-Catalyzed Difluoromethylation of Alkyl Iodides Enabled by Aryl Radical Activation of Carbon-Iodine Bonds

The engagement of unactivated alkyl halides in copper-catalyzed cross-coupling reactions has been historically challenging, due to their low reduction potential and the slow oxidative addition of copper(I) catalysts. In this work, we report a novel strategy that leverages the halogen abstraction ability of aryl radicals, thereby engaging a diverse range of alkyl iodides in copper-catalyzed Negishi-type cross-coupling reactions at room temperature. Specifically, aryl radicals generated via copper catalysis efficiently initiate the cleavage of the carbon-iodide bonds of alkyl iodides. The alkyl radicals thus generated enter the copper catalytic cycles to couple with a difluoromethyl zinc reagent, thus furnishing the alkyl difluoromethane products. This unprecedented Negishi-type difluoromethylation approach has been applied to the late-stage modification of densely functionalized pharmaceutical agents and natural products.

Electrochemical-Promoted Nickel-Catalyzed Oxidative Fluoroalkylation of Aryl Iodides

This work describes a general strategy for metal-catalyzed cross-coupling of fluoroalkyl radicals with aryl halides under electrochemical conditions. The contradiction between anodic oxidation of fluoroalkyl sulfinates and cathodic reduction of low-valent nickel catalysts can be well addressed by paired electrolysis, allowing for direct introduction of fluorinated functionalities into aromatic systems.

Late-stage difluoromethylation: concepts, developments and perspective

This review describes the conceptual advances that have led to the multiple difluoromethylation processes making use of well-defined CF₂H sources.