Nitrogen-Nitrogen Bond Formation via a Substrate-Bound Anion at a Mononuclear Nickel Platform

The nickel-C4F8 fragment coordinates an aminoaryl N-H ketimine to form a stable complex, which upon treatment with base and oxidant leads to an N-N bond forming reaction and the release of indazole product. A key and previously unidentified intermediate in the formation of the indazole was a diimine complex of nickel bearing significant charge on the aryl ring that initially contained the amine substituent. The C4F8 coligand was key for the redox transformation and for stabilization of the intermediate for characterization

Nitrogen-Nitrogen Bond Formation via a Substrate-Bound Anion at a Mononuclear Nickel Platform

The nickel-C4F8 fragment coordinates an aminoaryl N-H ketimine to form a stable complex, which upon treatment with base and oxidant leads to an N-N bond forming reaction and the release of indazole product. A key and previously unidentified intermediate in the formation of the indazole was a diimine complex of nickel bearing significant charge on the aryl ring that initially contained the amine substituent. The C4F8 coligand was key for the redox transformation and for stabilization of the intermediate for characterization

Difluoro(trimethylsilyl)acetonitrile: Synthesis and Fluoroalkylation Reactions

A new silicon reagent, difluoro­(trimethylsilyl)­acetonitrile, was prepared by insertion of difluorocarbene into silyl cyanide. The obtained silane served as a good cyanodifluoromethylating reagent toward aldehydes, <i>N</i>-tosylimines, <i>N</i>-alkylimines, and enamines under basic or acidic conditions

Nucleophilic Bromo- and Iododifluoro­methylation of Aldehydes

A method for bromo- and iododifluoromethylation of aldehydes using bromo- and iodo-substituted difluoromethyl silicon reagents (Me₃SiCF₂X) is described. The reaction is performed in the presence of a combination of tetrabutylammonium and lithium salts Bu₄NX/LiX (X = Br or I) in propionitrile. It is believed that, in this process, a short-lived halodifluoromethyl carbanion serves as nucleophile, which is reversibly generated from difluorocarbene and a halide anion

Difluoro(trimethylsilyl)acetonitrile: Synthesis and Fluoroalkylation Reactions

A new silicon reagent, difluoro­(trimethylsilyl)­acetonitrile, was prepared by insertion of difluorocarbene into silyl cyanide. The obtained silane served as a good cyanodifluoromethylating reagent toward aldehydes, <i>N</i>-tosylimines, <i>N</i>-alkylimines, and enamines under basic or acidic conditions

Halogenative Difluorohomologation of Ketones

A method for the difluorohomologation of ketones accompanied by halogenation of a C–H bond is described. The reaction involves silylation, difluorocarbene addition using Me₃SiCF₂Br activated by a bromide ion, and halogenation of intermediate cyclopropanes with <i>N</i>-bromo- or <i>N</i>-iodosuccinimide. The whole process is performed without isolation of intermediates. The resulting α,α-difluoro-β-halo-substituted ketones can be readily converted into fluorine containing pyrazole derivatives and oxetanes

Reactions of Sulfur- and Phosphorus-Substituted Fluoroalkylating Silicon Reagents with Imines and Enamines under Acidic Conditions

Nucleophilic fluoroalkylation reactions of imines and enamines with α-phenylthio, α-phenylsulfonyl, and α-diethylphosphoryl substituted fluorinated silanes have been investigated. The reactions are promoted by hydrofluoric acid generated <i>in situ</i> from potassium hydrodifluoride and trifluoroacetic acid. Sulfur reagents worked well with both imines and enamines, whereas phosphorus reagent efficiently coupled only with enamines

Nitrogen–Nitrogen Bond Formation via a Substrate-Bound Anion at a Mononuclear Nickel Platform

The nickel-C₄F₈ fragment coordinates an aminoaryl N–H ketimine to form a stable complex, which upon treatment with base and oxidant leads to an N–N bond-forming reaction and the release of indazole product. A key and previously unidentified intermediate in the formation of the indazole was a diimine complex of nickel bearing significant charge on the aryl ring that initially contained the amine substituent. The C₄F₈ coligand was key for the redox transformation and for stabilization of the intermediate for characterization

Nucleophilic Bromodifluoromethylation of Iminium Ions

A method for bromodifluoromethylation of iminium ions using Me₃SiCF₂Br is described. The reaction involves room temperature activation of the silicon reagent by HMPA to generate difluorocarbene, which upon interacting with excess of bromide ion provides bromodifluoromethyl carbanionic species. The iminium electrophiles are generated in situ from aldehydes, secondary amines, proton sponge, and silyl triflate. The reaction can be extended for introduction of chlorodifluoromethyl and iododifluoromethyl groups

Geminal Silicon/Zinc Reagent as an Equivalent of Difluoromethylene Bis-carbanion

A new difluorinated reagent, [difluoro­(trimethylsilyl)­methyl]­zinc bromide, bearing C–Zn and C–Si bonds is described. The reagent is conveniently prepared by cobalt-catalyzed halogen/zinc exchange. It can be coupled with two different C-electrophiles in a stepwise manner (with allylic halides for C–Zn bond and aldehydes for C–Si bond) affording products containing a difluoromethylene fragment