Base-Mediated Defluorosilylation of C(sp2 )−F and C(sp3 )−F Bonds

Nickel-Catalyzed, Reductive C(sp3 )-Si Cross-Coupling of α-Cyano Alkyl Electrophiles and Chlorosilanes

A nickel/zinc-catalyzed cross-electrophile coupling of alkyl electrophiles activated by an α-cyano group and chlorosilanes is reported. Elemental zinc is the stoichiometric reductant in this reductive coupling process. By this, a C(sp3 )-Si bond can be formed starting from two electrophilic reactants whereas previous methods rely on the combination of carbon nucleophiles and silicon electrophiles or vice versa.

Catalytic SN Ar Hydroxylation and Alkoxylation of Aryl Fluorides

Nucleophilic aromatic substitution (S_N Ar) is a powerful strategy for incorporating a heteroatom into an aromatic ring by displacement of a leaving group with a nucleophile, but this method is limited to electron-deficient arenes. We have now established a reliable method for accessing phenols and phenyl alkyl ethers via catalytic S_N Ar reactions. The method is applicable to a broad array of electron-rich and neutral aryl fluorides, which are inert under classical S_N Ar conditions. Although the mechanism of S_N Ar reactions involving metal arene complexes is hypothesized to involve a stepwise pathway (addition followed by elimination), experimental data that support this hypothesis is still under exploration. Mechanistic studies and DFT calculations suggest either a stepwise or stepwise-like energy profile. Notably, we isolated a rhodium η⁵ -cyclohexadienyl complex intermediate with an sp³ -hybridized carbon bearing both a nucleophile and a leaving group.

Experimental and Computational Studies of the Iron-Catalyzed Selective and Controllable Defluorosilylation of Unactivated Aliphatic gem-Difluoroalkenes

The first iron-catalyzed defluorosilylation of unactivated gem-difluoroalkenes was developed, delivering gem-disilylated alkenes and (E)-silylated alkenes with excellent efficiency. This protocol features good functional group compatibility and excellent regio- and stereoselectivity, enabling the late-stage silylation of biologically relevant compounds, thus providing good opportunities for applications in medicinal chemistry. Preliminary mechanistic studies and DFT calculations reveal that a nucleophilic addition and elimination of the second C-F bond might be involved in the disilylation catalytic system, demonstrating unusual reactivity characteristics of iron catalysis.

Concerted Nucleophilic Aromatic Substitution Reactions

Recent developments in experimental and computational chemistry have identified a rapidly growing class of nucleophilic aromatic substitutions that proceed by concerted (cSN Ar) rather than classical, two-step, SN Ar mechanisms. Whereas traditional SN Ar reactions require substantial activation of the aromatic ring by electron-withdrawing substituents, such activating groups are not mandatory in the concerted pathways.