Copper-catalyzed synthesis of α-trifluoromethylthio-substituted ketones

Photocatalytic Perfluoroalkylation of Disulfides and Diselenides. Syntheses of Perfluoroalkyl Thio- and Seleno-ethers

The synthesis of alkyl(aryl)-fluoroalkyl sulfanyl [R(Ar)-S-RF] and aryl-fluoroalkyl selenolyl (Ar-Se-RF) ethers through visible-light photocatalysis has been successfully carried out. This process involves disulfides, and diselenides [R(Ar)-X-X-R(Ar), where X = S or Se], and fluoroalkyl iodides (RF-I) in the presence of a base as an additive under photocatalysis. The photocatalyst Eosin Y and green light-emitting diodes are utilized for irradiation of R(Ar)-S-RF and Ar-Se-RF syntheses. Our method integrates low-energy visible-light photocatalysis, commercially available perfluoroalkylating reagents (RF-I), and easily obtainable disulfides and diselenides as starting materials. Mechanistic studies and a detailed synthetic procedure for (Ar)-S-RF on a large scale are presented.

Copper-Catalyzed Enantioselective C(sp3 )-SCF3 Coupling of Carbon-Centered Benzyl Radicals with (Me4 N)SCF3

In contrast with the well-established C(sp2 )-SCF3 cross-coupling to forge the Ar-SCF3 bond, the corresponding enantioselective coupling of readily available alkyl electrophiles to forge chiral C(sp3 )-SCF3 bond has remained largely unexplored. We herein disclose a copper-catalyzed enantioselective radical C(sp3 )-SCF3 coupling of a range of secondary/tertiary benzyl radicals with the easily available (Me4 N)SCF3 reagent. The key to the success lies in the utilization of chiral phosphino-oxazoline-derived anionic N,N,P-ligands through tuning electronic and steric effects for the simultaneous control of the reaction initiation and enantioselectivity. This strategy can successfully realize two types of asymmetric radical reactions, including enantioconvergent C(sp3 )-SCF3 cross-coupling of racemic benzyl halides and three-component 1,2-carbotrifluoromethylthiolation of arylated alkenes under mild reaction conditions. It therefore provides a highly flexible platform for the rapid assembly of an array of enantioenriched SCF3 -containing molecules of interest in organic synthesis and medicinal chemistry.

Visible-Light-Induced Photocatalytic Trifluoromethylation of Bunte Salts: Easy Access to Trifluoromethylthiolated Synthons

A metal-free visible-light-induced trifluoromethylation of Bunte salts of α-bromoketones/alkyl bromide/benzyl bromides/functionalized allyl (Baylis-Hillman) bromides has been accomplished using Langlois' reagent in the presence of inexpensive eosin Y as a photocatalyst to form the privileged trifluoromethylthiolated synthons. The method is straightforward, operationally simple, and endowed with broad substrate scope and good functional group tolerance.

Trifluoromethylthiolation of Hindered α-Bromoamides with Nucleophilic Trifluoromethylthiolating Reagents

General methods have not been previously developed for the synthesis of sterically hindered α-SCF₃-substituted carbonyl compounds using nucleophilic trifluoromethylthiolating reagents. Thus, we herein report sp³C-SCF₃ bond formation in hindered α-bromoamides containing 3-bromo-oxindoles and linear α-bromoamides using CuSCF₃ or AgSCF₃ under mild conditions to access sterically hindered α-SCF₃-substituted amides. This transformation is applicable to not only 3-SCF₃-substituted oxindoles but also primary and secondary amides and reveals a broad functional group tolerance. This method will benefit the fields of medicinal and agricultural chemistry.

Synthetic developments on the preparation of sulfides from thiol-free reagents

This critical review covers the main thiolating reagents with respect to their characteristics and reactivities. In fact, they are complementary to each other and bring different thiolation strategies, avoiding the hazardous thiol derivatives.

[(bpy)CuSCF3]: A Practical and Efficient Reagent for the Construction of C–SCF3 Bonds

In this account, we summarize recent work on the direct introduction of the SCF3 group by using [(bpy)CuSCF3] as trifluoromethylthiolating reagent. A number of efficient and convenient strategies have been disclosed for the synthesis of trifluoromethylthiolated compounds, including trifluoromethylthiolation of aryl, alkenyl, and alkyl halides, and arylboronic acids. These reactions afford various trifluoromethyl sulfides in good yields.

1 Introduction

2 Synthesis of [(bpy)CuSCF3]

3 Trifluoromethylthiolation of Aryl Halides

4 Trifluoromethylthiolation of Alkenyl Halides

5 Trifluoromethylthiolation of Alkyl Halides

6 Miscellaneous

7 Conclusion

Radical-mediated oxidative annulations of 1,n-enynes involving C–H functionalization

Recent progress in oxidative annulations of 1,n-enynes involving C–H functionalization is summarized.

Formal α-trifluoromethylthiolation of carboxylic acid derivatives via N-acyl pyrazoles

A direct and general one-pot approach to α-trifluoromethylthiolated amides, esters and carboxylic acids has been successfully developed under mild, catalytic and metal-free conditions.

Electrochemical trifluoromethylation/semipinacol rearrangement sequences of alkenyl alcohols: synthesis of β-CF3-substituted ketones

Electrochemical oxidative radical trifluoromethylation/semipinacol rearrangement sequences of alkenyl alcohols were developed in this study. This approach is environmentally benign and uses the shelf-stable Langlois reagent as a trifluoromethyl radical precursor and electrons as the oxidizing reagents. The present protocol offers a facile route to prepare β-trifluoromethylated ketone derivatives.

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

Fluorine chemistry plays an increasingly important role in pharmaceutical, agricultural, and materials industries. The incorporation of fluorine-containing groups into organic molecules can improve their chemical and physical properties, which attracts continuous interest in organic synthesis. Among various reported methods, transition-metal-catalyzed fluorination/fluoroalkylation has emerged as a powerful method for the construction of these compounds. This review attempts to describe the major advances in the transition-metal-catalyzed incorporation of fluorine, trifluoromethyl, difluoromethyl, trifluoromethylthio, and trifluoromethoxy groups reported between 2011 and 2019.

Novel Bifunctionalization of Activated Methylene: Base-Promoted Trifluoromethylthiolation of β-Diketones with Trifluoromethanesulfinyl Chloride

A novel bifunctionalization of activated methylene was achieved successfully through the base-promoted trifluoromethylthiolation of β-diketones or β-ketoesters with trifluoromethanesulfinyl chloride. A series of α-trifluoromethylthiolated α-chloro-β-diketones and α-chloro-β-ketoesters were obtained in moderate to good yields under mild conditions. When β-diketones containing a phenyl group with a hydroxyl or amino substituent at the ortho position were used as substrates, intramolecular trifluoromethylthiolation/cyclization reaction took place to give the corresponding cyclic products. Furthermore, the protocol could be extended to perfluoroalkylthiolation with the sodium perfluoroalkanesulfinate/POCl₃ system. On the basis of experimental results, plausible mechanisms are proposed.

Visible-light-induced oxidative difunctionalization of styrenes: synthesis of α-trifluoromethylthio-substituted ketones

A novel and practical synthesis of α-trifluoromethylthio-substituted ketones has been accomplished through the visible-light-induced aerobic oxidation of styrenes. The protocol employs the combination of CF₃SO₂Na and CS₂ as a new source of SCF₃ radicals in the presence of eosin Y as a photoredox catalyst.

The CF3-DAST-induced deacylative trifluoromethylthiolation of cyclic 1,3-diketones/lactams/lactones and its extension to deacylative pentafluorophenylthiolation

CF₃-DAST-induced deacylative trifluoromethylthiolation of cyclic 1,3-diketones lactams, and lactones that provides cyclic trifluoromethylthioketones, lactams and lactones is reported.

Direct thiolation of aza-heteroaromatic N-oxides with disulfides via copper-catalyzed regioselective C–H bond activation

A novel and efficient thiolation reaction of aza-heteroaromatic N-oxides with disulfides via copper catalyzed C–H activation has been developed.

Nucleophilic trifluoromethylthiolation of bromoalkynones with AgSCF3: C(sp)–SCF3 bond formation towards ynonyl trifluoromethyl sulfides

C(sp)–SCF₃ bond formation via the AgSCF₃ mediated nucleophilic trifluoromethylthiolation of bromoalkynones, delivering various ynonyl trifluoromethyl sulfides in high yields.

Elemental sulfur as a sulfuration agent in the copper-catalyzed C-H bond thiolation of electron-deficient arenes

By utilizing elemental sulfur as the thiolation agent and oxidant, a copper-catalyzed direct C-H bond thiolation of electron-deficient arenes was demonstrated. Various electron-deficient arenes were proved to be suitable for this transformation. Preliminary mechanistic studies indicated that this reaction underwent a radical pathway, in which the trisulfur radical anion (S₃˙^-) might play a vital role. Meanwhile, KIE experiments suggested that C-H bond cleavage was not involved in the rate-determining step.

Oxidative dual C–H thiolation of imidazopyridines with ethers or alkanes using elemental sulphur

Dual C–H thiolation reactions using elemental sulphur remain a challenge.

Tandem trifluoromethylthiolation/aryl migration of aryl alkynoates to trifluoromethylthiolated alkenes

The oxidative trifluoromethylthiolation of aryl alkynoates with AgSCF₃ provided a new access to trifluoromethylthiolated alkenes.

AgSCF3-mediated trifluoromethylthiolation of α,α-diaryl allylic alcohols via radical neophyl rearrangement

A novel example of AgSCF₃-mediated oxidative radical trifluoromethylthiolation of α,α-diaryl allylic alcohols is presented, producing various α-aryl-β-trifluoromethylthiolated carbonyl ketones via radical neophyl rearrangement under mild conditions.

Metal-free direct thiocarbamation of imidazopyridines with carbamoyl chloride and elemental sulfur

Metal-free direct thiocarbamation of imidazopyridines using elemental sulfur.

Synthesis of 1,2,2-trifluorovinyl sulphides and selenides from trifluorovinylation of organic thiocyanates and selenocyanates

A nucleophilic trifluorovinylation of organothiocyanates with trifluorovinyl trimethylsilane for the synthesis of trifluorovinyl sulphides has been developed.

18F-Fluoroform: a 18F-trifluoromethylating agent for the synthesis of SCF218F-aromatic derivatives

A new protocol for the synthesis of SCF₂¹⁸F-aromatic derivatives from ¹⁸F-fluoroform is described.

Copper-Catalyzed 2,2,2-Trifluoroethylthiolation of Aryl Halides

Herein, a copper-catalyzed 2,2,2-trifluoroethylthiolation reaction of aryl bromides and iodides with elemental sulfur, and 1,1,1-trifluoro-2-iodoethane is described. The reaction showed excellent functional group tolerance and allowed the synthesis of various substituted aryl 2,2,2-trifluoroethyl thioethers with good to excellent yields. This transformation constitutes a one-pot synthesis of 2,2,2-trifluoroethylthiolated compounds from inexpensive, readily available starting materials. Utility of the protocol was further demonstrated in the late-stage synthesis of the pirfenidone derivative. The copper thiolate species were prepared and proposed as key intermediates in the catalytic cycle.