AbstractPresented is a novel intermolecular radical trifluoromethylfluorosulfonylation of unactivated alkenes under mild reaction conditions with good functional-group tolerance in the most atom-economic manner by using readily available Ag(O2CCF2SO2F) and N-fluorobenzenesulfonimide (NFSI). Both the trifluoromethyl and sulfonyl groups in the products originate from Ag(O2CCF2SO2F).

AbstractPresented is a novel intermolecular radical trifluoromethylfluorosulfonylation of unactivated alkenes under mild reaction conditions with good functional-group tolerance in the most atom-economic manner by using readily available Ag(O2CCF2SO2F) and N-fluorobenzenesulfonimide (NFSI). Both the trifluoromethyl and sulfonyl groups in the products originate from Ag(O2CCF2SO2F).

This review summarizes the recent advances in the catalytic syntheses of CF3S-containing organic molecules using various nucleophilic or electrophilic trifluoromethylthiolating reagents. C–halogen and CH bonds in various molecules have been transformed to CSCF3 bonds by transition-metal-catalyzed reactions, such as cross-coupling of aryl halides. Enantioselective reactions controlled by chiral metal complexes or chiral organocatalysts have afforded many trifluoromethylthiolated chiral architectures, such as β-ketoesters and oxindoles. Very recently, visible-light-induced photoredox trifluoromethylthiolations have been developed, providing versatile CF3S-containing structures efficiently.The trifluoromethylthio group (CF3S) with high lipophilicity and strong electron-withdrawing properties plays an exceedingly important part in biological and medicinal chemistry. The review summarizes the recent developments in direct trifluoromethylthiolation using three catalytic methods, namely, transition-metal catalysis, chiral organocatalysis, and photocatalysis.Download high-res image (122KB)Download full-size image

Cu-promoted reactions of 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) with dialkyl phosphonates produced dialkyl (2,2,2-trifluoroethyl)phosphonates efficiently under mild conditions by successively activating the two inert C–Cl bonds in HCFC-123. These reactions can be efficiently carried out on a >30 g scale with moderate to good yields.

•A hydrochlorofluorocarbon (HCFC) is used to synthesize 2,2,2-trifluoroethyl diynes.•The C–C bond formation is promoted by copper and ethanolamine.•Two examples of converting the diynes to heterocycles are demonstrated.Copper-mediated reaction of terminal 1,3-diynes with 1,1-dichloro-2,2,2-trifluoroethane (CF3CHCl2) using ethanolamine as ligand gave trifluoroethylated unsymmetrical 1,3-diynes in moderate to good yields. The reaction were carried out under mild conditions, and were easy to operate. Aryl groups with weak electron-withdrawing group or electron-donating group, and alkyl substitutents at terminal 1,3-diynes were tolerated. Synthesis of a trifluoroethylated conjugated triyne by using this method was demonstrated. Further transformation of the trifluoroethylated unsymmetrical 1,3-diyne to provide trifluoroethyl-substituted 1,2,3-triazole and isoxazole as application examples were successfully realized.

A mild, operationally simple, visible light-induced photoredox method for constructing novel trifluoromethylated quaternary carbon centers from trifluoromethylated tertiary bromides has been developed. Using this method, a wide range of alkenes were successfully bifunctionalized to γ-butyrolactams. As for electron-rich alkenes, reactions catalyzed by Ir(dF(CF3)ppy)2(dtbbpy)(PF6) were kinetic processes with high yields and short times. For styrenes, reactions catalyzed by Ir(ppy)2(dtbbpy)(PF6) were thermodynamic processes with moderate yields and prolonged reaction times. For aliphatic alkenes, the reactions were neither thermodynamic nor kinetic and fac-Ir(ppy)3 was used as catalyst. Thus, reactions were not as efficient as electron-rich alkenes. The atom-transfer radical addition reactions of trifluoromethylated tertiary bromides with alkynes were also achieved. The configuration of products we separated was E type only. Some of the products exhibited bactericidal activity.

The visible-light-induced photoredox difunctionalization reactions of styrenes with 1,1,1-trifluoro-2-iodoethane under an oxygen atmosphere in the presence of water give γ-trifluoromethyl alcohols. In this radical reaction, the oxygen atom in the product originates from molecular oxygen, and water is shown to be important to promote the reaction.

Single electrode materials capable of both electric double-layer and Faradic redox-based pseudo capacitance can be used for fabrication of high performance supercapacitors in an easy way and thus are highly desirable in the energy storage field. This contribution reports a new kind of such materials based on alkylated graphene materials (CnrGO, n is the carbon number of their alkyl side chains) having different alkyl side chains (n = 4, 8, and 16). These materials were prepared via esterification of KOH-treated GO with the corresponding alkyl bromides in the presence of a phase transfer catalyst. More importantly, water was used as the reaction medium, and thus endowing the preparation method an eco-friend feature. The so-prepared graphene materials displayed chain length-dependent specific surface area and the population of residue CO functionalities, and thus affording vast differences in their supercapacitor behaviors. C4rGO, the product having butyl side chains, showed the best supercapacitor performance with a capacitance up to 242.2 F g−1 at a scan rate of 100 mV s−1 and a good cycling stability.

Redox-active graphene materials are highly desirable for the production of high performance supercapacitors. Following our previous work that found that alkylated graphene nanosheets are a new kind of such material, we report here that the simple replacement of alkyl side chains with partially fluorinated alkyl chains further improves their capacitive electrode performance. In this work, one partially fluorinated graphene material (pFAG) was prepared by the reaction of KOH-pretreated graphene oxide with 2-perfluorohexylethyl bromide in the presence of a phase transfer catalyst. Compared with the graphene material modified with octyl side chains (AG), pFAG possesses a larger amount of residual oxygen functionalities, which is favorable to endow the material with a redox-active nature and achieve a larger faradaic capacitance. Moreover, pFAG presented a special self-assembly behavior and formed continuous and large plate-like objects in the solid state. Finally, a supercapacitor electrode was fabricated with pFAG and its performance was compared with the previously reported AG-based electrode in detail. It was found that the pFAG electrode has a much better capacitive performance than that based on AG (218.3 vs. 160.0 F g−1 at a scan rate of 100 mV s−1 by cyclic voltammetry, and 187.0 vs. 118.8 F g−1 at a current density of 3 A g−1 by galvanostatic charge/discharge method). When charge/discharge was carried out at 1 A g−1, the specific capacitance of pFAG-based electrode reached 388.0 F g−1, among the highest values of reported graphene-based electrodes. Furthermore, pFAG electrodes exhibited a good cycling stability. All these demonstrate graphene nanosheets modified with partially fluorinated alkyl chains would be a good way to achieve high performance redox-active electrode materials.

•This review covers compounds with a CF bond, CF2 or CF3.•Various organic compounds are synthesized through CF bond activation.•Aliphatic fluorides could be activated by Lewis acid, Brønsted superacids or hydrogen bonding.•The cleavage of CF bond could be mediated by transition-metal or rare earth metal.•Dehydrofluorination by a base or SN2′ displacement by a nucleophile could be a method for leaving of a fluoride.CF bond activation of aliphatic fluorides provides new methodologies for synthesis of new fluorinated building blocks as well as versatile non-fluorinated products. This review covers the recent CF bond cleavage examples and further transformation of compounds bearing with an aliphatic fluoride, difluoromethylene group or trifluoromethyl groups. The methods to activate a CF bond include activation by Lewis acid, Brønsted superacids and hydrogen bonding, and mediation by transition-metals and rare earth metals. Partial reduction of trifluoromethyl group through a single electron transfer (SET) process can provide the compounds with less fluorine. Bases are often used for the elimination of hydrofluoride. SN2′ displacement is also an important method for transformation of monofluorinated, difluorinated and trifluorinated olefins to various synthetically interesting molecules.

•Trifluoromethylated ketene aminoacetals were prepared.•Pd-catalyzed allylation was carried out.•Asymmetric reaction was researched.•Quaternary carbon centers were built.A new development in the palladium-catalyzed allylation reaction of trifluoromethylated ketene aminoacetals was reported. These nucleophilic reagents were prepared by adding aminoalcohols to methyl 3,3,3-trifluoro-2-trifluoromethylpropanoate. The asymmetric version of the allylation reaction was investigated using chiral oxazolidine-based starting materials or chiral palladium catalysts. Asymmetric allylic alkylation was carried out with up to 74% ee using a chiral catalyst. However, no improvement was observed using double stereodifferentiation. These results provided a novel access for trifluoromethylated all-carbon quaternary carbon centers.

•Entrainment reaction.•Indirect SRN1 reaction.•Cleavage of unactivated CCl bond.An interesting entrainment process in SRN1 reactions of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) with thiolates were studied by experiments and DFT calculations. The radical-anion intermediate, generated from coupling of the fluorinated radical with the thiolate was considered as the key intermediate in this reaction.Entrainment process was found in the SRN1 reaction of HCFC-123 with thiolates initiated by catalytic amount Na2S2O4.

A method has been developed for the synthesis of α-trifluoromethyl ketones via the Cu-catalyzed trifluoromethylation of silyl enol ethers with an electrophilic trifluoromethylating agent, which produces a trifluoromethyl radical.

Significant synthetic challenges remain for the asymmetric synthesis of tertiary α-fluoro ketones, which are potentially useful molecules for the development of drugs, agrochemicals, and functional materials. Herein, we describe the development of a method for the catalytic enantioselective synthesis of tertiary α-fluoro ketones via the Tsuji–Trost reaction of racemic acyclic α-fluorinated ketones. Enantioenriched acyclic α-cabonyl tertiary fluorides can be produced with the aid of a palladium/phosphinooxazoline catalyst.

Oxidative coupling of benzylamines to imines by molecular oxygen is efficiently realized in the presence of very low catalyst loadings of Co(II) β-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrin. Due to the effect of four β-CF3 groups, the catalyst shows good selectivity and very high turnover number. The reaction is easily scaled up and may provide a convenient way to prepare many imines in large scale.

A novel group of β-multi-substituted push–pull porphyrins (1, 2 and 3) has been designed and synthesized. Only one tautomer was observed for each of them and electron-withdrawing (Br, CF3, –(CF)4−) and -donating (MeO) groups within those porphyrins were believed to be out of the major delocalization pathway.

CF3-containing esters smoothly reacted with electron-deficient alkenes in the presence of a phosphine (2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl) organocatalyst at room temperature in an aerobic atmosphere. These Michael reactions efficiently provided products with a CF3 quaternary carbon center.

The reductive cleavage of the unactivated carbon–chlorine bond of 2-chloro-1,1,1-trifluoroethane (HCFC-133a) via a single electron transfer (SET) process using transition-metal-catalysis has been achieved. Ni(0) or Cu(0) catalytic systems afford 1,1,1-trifluoroethane (HFC-143a) or 1,1-difluoroethylene (VDF) with excellent yields respectively. The formation of VDF may be due to the β-elimination of the 1,1,1-trifluoroethyl anion generated by SET between the corresponding radical and a Cu(I) intermediate.

A copper-mediated cross-coupling reaction between HCFC-123 and phenols or thiophenols has been achieved. It is found that diethyl amine, which serves as both the activator and ligand of copper, plays a key role in this reaction. Two possible radical involved processes are proposed for the reaction mechanism.

The reductive cleavage of the unactivated carbon–chlorine bond of 2-chloro-1,1,1-trifluoroethane (HCFC-133a) via a single electron transfer (SET) process using transition-metal-catalysis has been achieved. Ni(0) or Cu(0) catalytic systems afford 1,1,1-trifluoroethane (HFC-143a) or 1,1-difluoroethylene (VDF) with excellent yields respectively. The formation of VDF may be due to the β-elimination of the 1,1,1-trifluoroethyl anion generated by SET between the corresponding radical and a Cu(I) intermediate.