Atom-transfer radical addition of fluoroalkyl bromides to alkenes via a photoredox/copper catalytic system.

A method for the addition of fluorinated alkyl bromides to alkenes is described. The reaction proceeds under visible light irradiation in the presence of two catalysts: Ir(ppy)3 and N-heterocyclic carbene ligated copper bromide (IMesCuBr). The role of the iridium photocatalyst is to generate the fluoralkyl radical, while the copper promotes formation of the carbon-bromine bond.

Photoredox Reaction of 2-Mercaptothiazolinium Salts with Silyl Enol Ethers.

A method for the generation of free radicals from thiazolinium salts upon photocatalytic reduction is described. The thiazolinium salts are generated by treatment with methyl triflate of 2-mercaptothiazolines, which can be readily obtained from alkyl bromides and tosylates via a nucleophilic substitution reaction or by hydrothiolation of alkenes. Silyl enol ethers were used to trap the radicals, furnishing ketones after successive single-electron oxidation and elimination of the silyl cation.

Nucleophilic Difluoromethylation Using (Bromodifluoromethyl)trimethylsilane.

A combination of (bromodifluoromethyl)trimethylsilane (Me3SiCF2Br), triphenylphosphine, and DMPU serves as a source of difluorinated phosphorus ylide Ph3P═CF2 under mild conditions. The system was used to effect nucleophilic difluoromethylation of ketones and nitro alkenes. The reaction efficiency is believed to be associated with Lewis acidic activation of the substrates by a silylium species formed upon generation of the phosphorus ylide.

Coupling of α,α-difluoro-substituted organozinc reagents with 1-bromoalkynes.

α,α-Difluoro-substituted organozinc reagents generated from conventional organozinc compounds and difluorocarbene couple with 1-bromoalkynes affording gem-difluorinated alkynes. The cross-coupling proceeds in the presence of catalytic amounts of copper iodide in dimethylformamide under ligand-free conditions.

Difluoromethylene phosphabetaine as an equivalent of difluoromethyl carbanion.

A method for nucleophilic difluoromethylation of reactive Michael acceptors, aldehydes, and azomethines is described. The reaction is performed using the readily available and air-stable reagent difluoromethylene phosphabetaine. The process involves interaction of an electrophilic substrate with in situ generated difluorinated phosphonium ylide followed by hydrolysis of the carbon-phosphorus bond under mild conditions.

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.

Copper-catalyzed allylation of α,α-difluoro-substituted organozinc reagents.

A method for the coupling of organozinc reagents, difluorocarbene, and allylic electrophiles is described. The reaction involves insertion of difluorocarbene into the carbon-zinc bond followed by copper-catalyzed allylic substitution.

Reactions of difluorocarbene with organozinc reagents.

Reactions of difluorocarbene with benzyl and alkylzinc halides leading to fluorinated organozinc species have been described. The generated α-difluorinated organozinc reagents are reasonably stable in solution and can be quenched with external electrophiles (iodine, bromine, proton), affording compounds containing the CF(2) fragment.