Access to All-Carbon Quaternary Centers by Photocatalytic Fluoroalkylation of α-Halo Carbonyl Compounds.

Perfluoroalkyl groups have become significantly important in pharmaceutical and agrochemical applications. In this study, we present a visible light-mediated photoredox neutral strategy for the fluoroalkylation of tertiary alkyl chlorides under transition-metal-free conditions. This method allows for the facile synthesis of fluoroalkylated all-carbon quaternary centers, exhibiting excellent functional group compatibility. Mechanistic studies reveal the involvement of two reactive radical intermediates and the in situ formation of metal enolates in a radical-polar crossover manner. The versatility of this methodology is demonstrated through synthetic transformations based on the carbonyl group, showcasing its potential for the rapid assembly of diverse organic molecules bearing fluoroalkyl all-carbon quaternary centers.

Copper-Catalyzed Radical Aminotrifluoromethylation of Alkenes.

We report herein an unprecedented protocol for aminotrifluoromethylation of alkenes. With Cu(OTf)2 as the catalyst, the reaction of alkenes, (bpy)Zn(CF3)2, and N-fluorobis(benzenesulfonyl)imide (NFSI) at room temperature provides the corresponding aminotrifluoromethylation products in satisfactory yields with high regioselectivity opposite to those driven by CF3 radical addition. The method exhibits a broad substrate scope and wide functional group compatibility. A mechanism involving N-radical addition to alkenes followed by trifluoromethylation of alkyl radicals is proposed.

Copper-Catalyzed Ring-Opening Radical Trifluoromethylation of Cycloalkanone Oximes.

The copper-catalyzed ring-opening C-trifluoromethylation of cycloalkanone oximes with Zn(CF3)2 complexes is described. The reaction proceeds in dichloromethane under mild conditions, providing an efficient and general entry to γ- or δ-CF3-substituted nitriles via tandem N-O and C(sp2)-C(sp3) bond cleavage and C(sp3)-CF3 bond formation. The protocol exhibits a broad substrate scope and wide functional group compatibility. A radical mechanism involving the CF3 transfer from Cu(II)-CF3 complexes to alkyl radicals is proposed.

Copper-Catalyzed Remote C(sp3 )-H Trifluoromethylation of Carboxamides and Sulfonamides.

Reported herein is an unprecedented protocol for trifluoromethylation of unactivated aliphatic C(sp3 )-H bonds. With Cu(OTf)2 as the catalyst, the reaction of N-fluoro-substituted carboxamides (or sulfonamides) with Zn(CF3 )2 complexes provides the corresponding δ-trifluoromethylated carboxamides (or sulfonamides) in satisfactory yields under mild reaction conditions. A radical mechanism involving 1,5-hydrogen atom transfer of N-radicals followed by CF3 -transfer from CuII -CF3 complexes to the thus formed alkyl radicals is proposed.

Radical C(sp2)-H Trifluoromethylation of Aldehydes in Aqueous Solution.

The copper-mediated C(sp2)-H trifluoromethylation of aldehydes is described. The reaction of aldehydes with (bpy)Cu(CF3)3, Et3SiH, and K2S2O8 in aqueous acetone at room temperature provides the corresponding trifluoromethyl ketones in satisfactory yields. The protocol is applicable to both aliphatic and aromatic aldehydes and exhibits a broad substrate scope and wide functional group compatibility. A mechanism involving Cu(II)-mediated trifluoromethylation of acyl radicals is proposed.

Radical Carbofluorination of Unactivated Alkenes with Fluoride Ions.

The copper-assisted radical carbofluorination of unactivated alkenes with fluoride ions is described. With [Cu(L3)F2]H2O (L3 = 4,4'-di(methoxycarbonyl)-2,2'-bipyridine) as the fluorine source and [Ag(DMPhen)(MeCN)]BF4 (DMPhen = 2,9-dimethyl-1,10-phenanthroline) as the chloride scavenger, the reaction of unactivated alkenes with CCl4 in acetonitrile provided the corresponding carbofluorination products in satisfactory yields. The protocol exhibited a wide functional group compatibility and broad substrate scope and could be extended to the use of a variety of activated alkyl chlorides other than CCl4. A copper-catalyzed fluorotrifluoromethylation of unactivated alkenes was then successfully developed with CsF as the fluorine source and Umemoto's reagent as the trifluoromethylating agent. A mechanism involving the fluorine atom transfer from Cu(II)-F complexes to alkyl radicals is proposed.

Selective Radical Fluorination of Tertiary Alkyl Halides at Room Temperature.

Direct fluorination of tertiary alkyl bromides and iodides with Selectfluor is described. The halogen-exchange fluorination proceeds efficiently in acetonitrile at room temperature under metal-free conditions and exhibits a wide range of functional group compatibility. Furthermore, the reactions are highly selective in that alkyl chlorides and primary and secondary alkyl bromides remain intact. A radical mechanism is proposed for this selective fluorination.

Silver-Catalyzed Decarboxylative Trifluoromethylation of Aliphatic Carboxylic Acids.

The silver-catalyzed decarboxylative trifluoromethylation of aliphatic carboxylic acids is described. With AgNO3 as the catalyst and K2S2O8 as the oxidant, the reactions of aliphatic carboxylic acids with (bpy)Cu(CF3)3 (bpy = 2,2'-bipyridine) and ZnMe2 in aqueous acetonitrile at 40 °C afford the corresponding decarboxylative trifluoromethylation products in good yield. The protocol is applicable to various primary and secondary alkyl carboxylic acids and exhibits wide functional group compatibility. Mechanistic studies reveal the intermediacy of -Cu(CF3)3Me, which undergoes reductive elimination and subsequent oxidation to give Cu(CF3)2 as the active species responsible for the trifluoromethylation of alkyl radicals.

Trifluoromethylation of Alkyl Radicals in Aqueous Solution.

The copper-mediated trifluoromethylation of alkyl radicals is described. The combination of Et3SiH and K2S2O8 initiates the radical reactions of alkyl bromides or iodides with BPyCu(CF3)3 (BPy = 2,2'-bipyridine) in aqueous acetone at room temperature to afford the corresponding trifluoromethylation products in good yield. The protocol is applicable to various primary and secondary alkyl halides and exhibits wide functional group compatibility. A mechanism involving trifluoromethyl group transfer from Cu(II)-CF3 intermediates to alkyl radicals is proposed.

Catalytic Radical Trifluoromethylalkynylation of Unactivated Alkenes.

The trifluoromethylalkynylation of unactivated alkenes with alkynyl sulfones and Togni's reagent was developed. The reaction was catalyzed by 2,4,6-trimethylpyridine, leading to various ß-trifluoromethylated alkynes under metal-free conditions with a broad substrate scope and wide functional group compatibility. A mechanism involving catalytic nonchain radical processes is proposed.