Metal-Free sp3 C-SCF3 Coupling Reactions between Cycloketone Oxime Esters and S-trifluoromethyl 4-Methylbenzenesulfonothioate

Copper-catalyzed thiocyanation of cyclobutanone oxime esters using ammonium thiocyanate

A copper-catalyzed thiocyanation of cycloketone oxime esters with ammonium thiocyanate has been developed for the first time. This innovative approach allows access to cyano and thiocyano bifunctionally substituted alkanes, which can be further transformed into their respective trifluoromethylthiol-substituted or difluoromethylthiol-substituted alkylnitriles, alkynyl sulfides, and phosphorothioate esters. The readily available nature of ammonium thiocyanate and the cost-effectiveness of the copper catalyst make this method a promising strategy for the synthesis of sulfur-containing alkylnitriles.

Copper-catalyzed ring-opening trifluoromethylthiolation/trifluoromethylselenolation of cyclopropanols with TsSCF3 or Se-(trifluoromethyl) 4-methoxybenzenesulfonoselenoate

We report a ring-opening trifluoromethylthiolation of cyclopropanols with TsSCF₃ by using Cu(OAc)₂ as the catalyst. Moreover, by using this strategy, the trifluoromethylselenolation of cyclopropanols with Se-(trifluoromethyl) 4-methoxybenzenesulfonoselenoate to access β-SeCF₃-substituted carbonyl compounds is achieved for the first time. The broad substrate scope, readily accessible reagents and cheap catalyst make this protocol an alternative and efficient method for the synthesis of β-SCF₃-substituted or β-SeCF₃-substituted carbonyl compounds.

Deacylative Thiolation by Redox-Neutral Aromatization-Driven C-C Fragmentation of Ketones

Herein we report the development of deacylative thiolation of diverse methyl ketones. The reaction is redox-neutral, and heavy-metal-free, which provides a new way to introduce thioether groups site-specifically to unactivated aliphatic positions. It also features excellent functional group tolerance and broad substrate scope, thus allowing late-stage derivatization. The process benefits from efficient condensation between the activation reagent and ketone substrates, which triggers aromatization-driven C-C fragmentation and rapid radical coupling with thiosulfonates. Experimental and computational mechanistic studies suggest the involvement of a radical chain pathway.

Visible-Light-Promoted Trifluoromethylthiolation and Trifluoromethylselenolation of 1,4-Dihydropyridines

We report a metal-free trifluoromethylthiolation and trifluoromethylselenolation of 1,4-dihydropyridines with S-(trifluoromethyl) 4-methylbenzenesulfonothioate and Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate under visible light irradiation. This transformation was tolerated with a wide range of functional groups and provided an alternative and green strategy for the synthesis of trifluoromethylthioesters and trifluoromethylselenoesters.

Electroreductive Ring-Opening Carboxylation of Cycloketone Oxime Esters with Carbon Dioxide

Electroreductive ring-opening carboxylation of cycloketone oxime esters with atmospheric carbon dioxide is reported. This reaction proceeded under simple constant current conditions in an undivided cell using glassy carbon as the cathode and magnesium as the sacrificial anode, providing substituted γ- and δ-cyanocarboxylic acids in moderate to good yields. Electrochemically generated cyanoalkyl radicals and cyanoalkyl anion are proposed as the key intermediates.

Synthesis of 3-SCF2H-/3-SCF3-chromones via Interrupted Pummerer Reaction/Intramolecular Cyclization Mediated by Difluoromethyl or Trifluoromethyl Sulfoxide and Tf2O

The reaction of alkynyl aryl ketones bearing an o-methoxy group with difluoromethyl sulfoxide in the presence of Tf₂O was found to conveniently afford the corresponding 3-SCF₂H-substituted chromones. The combining use of difluoromethyl sulfoxide/Tf₂O could represent the first reagents system that can introduce the biologically important SCF₂H moiety under base-free conditions via an interrupted Pummerer reaction. The same protocol could also be applied to the synthesis of 3-SCF₃-substituted chromones by replacing difluoromethyl sulfoxide with trifluoromethyl sulfoxide and CH₃CN with toluene.

Transition-Metal- and Light-Free Generation of an Iminyl Radical: Facile Approach to Oxindoles and Isoquinolinediones with a Quaternary Carbon Center via Cyanoalkylarylation

We have developed an efficient and non-toxic method for the environmental-friendly generation of an iminyl radical from cyclobutanone oxime ester via direct thermolysis in the absence of light, transition metals, "tin", and other activators. This redox-neutral cyanoalkylarylation protocol enjoys a wide substrate scope and a good functional group tolerance, providing facile access to oxindoles and isoquinolinediones with a quaternary carbon center that are difficult to prepare by traditional methods.

Visible-Light-Promoted Selenocyanation of Cyclobutanone Oxime Esters Using Potassium Selenocyanate

We report the visible-light-promoted selenocyanation of cyclobutanone oxime esters using potassium selenocyanate in the presence of a fac-Ir(ppy)₃ catalyst for the first time. Because of the mild conditions employed and use of readily accessible potassium selenocyanate, this method is an effective and green strategy for the synthesis of cyano and selenocyano bifunctional substituted alkanes.

Catalyst-Free Decarbonylative Trifluoromethylthiolation Enabled by Electron Donor-Acceptor Complex Photoactivation

A catalyst- and additive-free decarbonylative trifluoromethylthiolation of aldehyde feedstocks has been developed. This operationally simple, scalable, and open-to-air transformation is driven by the selective photoexcitation of electron donor-acceptor (EDA) complexes, stemming from the association of 1,4-dihydropyridines (donor) with N-(trifluoromethylthio)phthalimide (acceptor), to trigger intermolecular single-electron transfer events under ambient- and visible light-promoted conditions. Extension to other electron acceptors enables the synthesis of thiocyanates and thioesters, as well as the difunctionalization of [1.1.1] propellane. The mechanistic intricacies of this photochemical paradigm are elucidated through a combination of experimental efforts and high-level quantum mechanical calculations [dispersion-corrected (U)DFT, DLPNO-CCSD(T), and TD-DFT]. This comprehensive study highlights the necessity for EDA complexation for efficient alkyl radical generation. Computation of subsequent ground state pathways reveals that SH2 addition of the alkyl radical to the intermediate radical EDA complex is extremely exergonic and results in a charge transfer event from the dihydropyridine donor to the N-(trifluoromethylthio)phthalimide acceptor of the EDA complex. Experimental and computational results further suggest that product formation also occurs via SH2 reaction of alkyl radicals with 1,2-bis(trifluoromethyl)disulfane, generated in-situ through combination of thiyl radicals.

Radical-Promoted Distal C-H Functionalization of C(sp3 ) Centers with Fluorinated Moieties

Due to their unique properties, fluorinated scaffolds are pivotal compounds in pharmaceuticals, agrochemicals, and materials science. Over the last years, the development of versatile strategies for the selective synthesis of fluorinated molecules by direct C-H bond functionalization has attracted a lot of attention. In particular, the design of novel transformations based on a radical process was a bottleneck for distal C-H functionalization reactions, offering synthetic solutions for the selective introduction of fluorinated groups. This Minireview highlights the major contributions in this blossoming field. The development of new methodologies for the remote functionalization of aliphatic derivatives with various fluorinated groups based on a 1,5-hydrogen atom transfer process and a β-fragmentation reaction will be showcased and discussed.

Organocatalytic Three-Component 1,2-Cyanoalkylacylation of Alkenes via Radical Relay

Here, we report an unprecedented regioselective, intermolecular 1,2-cyanoalkylacylation of feedstock alkenes with readily available oxime esters and aldehydes by N-heterocyclic carbene (NHC) organocatalysis. The crux of this success is the exquisite control over the radical relay process by an NHC organocatalyst. This protocol offers a general platform for diversity-oriented synthesis of valuable ketonitriles under mild, transition-metal-free, and redox-neutral conditions and highlights its potential in the late-stage functionalization of pharmaceutical architectures and natural products.