Copper-Mediated Trifluoromethylation Research Articles

Unimolecular Reactivity of [Cu(R)(CF3 )3 ]- Complexes (R=Organyl): Stepwise versus Concerted Mechanism in Copper-Mediated Trifluoromethylation.

The cuprate complexes [Cu(R)(CF3 )3 ]- (R=organyl) offer an efficient synthetic access to valuable trifluoromethylation products RCF3 . Here, electrospray-ionization mass spectrometry is used to analyze the formation of these intermediates in solution and probe their fragmentation pathways in the gas phase. Furthermore, the potential energy surfaces of these systems are explored by quantum chemical calculations. Upon collisional activation, the [Cu(R)(CF3 )3 ]- complexes (R=Me, Et, Bu, s Bu, allyl) afford the product ions [Cu(CF3 )3 ]⋅- and [Cu(CF3 )2 ]- . The former obviously results from an R⋅ loss, whereas the latter originates either from the stepwise release of R⋅ and CF3 ⋅ radicals or a concerted reductive elimination of RCF3 . The gas-phase fragmentation experiments as well as the quantum chemical calculations indicate that the preference for the stepwise reaction toward [Cu(CF3 )2 ]- increases with the stability of the formed organyl radical R⋅. This finding suggests that the recombination of R⋅ and CF3 ⋅ radicals may possibly contribute to the formation of RCF3 from [Cu(R)(CF3 )3 ]- in synthetic applications. In contrast, the [Cu(R)(CF3 )3 ]- complexes (R=aryl) only yield [Cu(CF3 )2 ]- when subjected to collision-induced dissociation. These species exclusively undergo a concerted reductive elimination because the competing stepwise pathway is disfavored by the low stability of aryl radicals.

Direct Arene Trifluoromethylation Enabled by a High-Valent CuIII -CF3 Compound.

Direct C-H trifluoromethylation of arenes and heteroarenes poses an important synthetic challenge that is highly desirable. High-valent CuIII -CF3 compounds have often been invoked in copper-mediated trifluoromethylation reactions, but the fundamental reactivity toward arenes is elusive. Herein, direct C-H trifluoromethylation of arenes/heteroarenes by a high-valent CuIII -CF3 compound is disclosed for the first time. The CuIII -CF3 compound serves CF3 radical and a CuII oxidant by homolytic cleavage of a CuIII -CF3 bond, which engage synergistically in a SE Ar type reaction with arenes. The presence of K2 S2 O8 co-oxidant can significantly improve the reaction yields. This reaction shows good efficiency, broad functional group tolerance, and the potential in late-stage functionalization. The reactivity of high-valent CuIII -CF3 compounds disclosed in this study represents an important progress in organofluorine and CuIII chemistry.

Correction to “Mechanistic Insight into Copper-Mediated Trifluoromethylation of Aryl Halides: The Role of CuI”

Correction to “Mechanistic Insight into Copper-Mediated Trifluoromethylation of Aryl Halides: The Role of CuI”

A Fruitful Decade of Organofluorine Chemistry: New Reagents and Reactions

A Fruitful Decade of Organofluorine Chemistry: New Reagents and Reactions

New Avenues in Copper-Mediated Trifluoromethylation Reactions Using Fluoroform as the CF3 Source

AbstractOrganic molecules containing the trifluoromethyl (CF3) group play a vital role in pharmaceuticals, agrochemicals, and materials. New trifluoromethylation methods should encompass capabilities to address issues in efficiency, selectivity, and CF3 source all at once. Fluoroform (CF3H), an industrial byproduct, has emerged as an attractive CF3 source. The reaction profile of the [CuCF3] reagent derived from fluo­roform has surpassed its original applications in cross-coupling-type trifluoromethylation. We have discovered a host of unique copper-mediated trifluoromethylation reactions using [CuCF3] from fluoroform, especially under oxidative conditions, to deliver efficient and selective synthesis of trifluoromethylated compounds.1 Introduction2 Construction of C–CF3 Bonds for the Synthesis of Trifluoromethylated Building Blocks2.1 C(sp)–CF3 Bond Formation2.2 C(sp2)–CF3 Bond Formation2.3 C(sp3)–CF3 Bond Formation3 Domino Synthesis of Trifluoromethylated Heterocycles3.1 3-(Trifluoromethyl)indoles3.2 3-(Trifluoromethyl)benzofurans3.3 2-(Trifluoromethyl)indoles4 Trifluoromethylative Difunctionalization of Arynes4.1 Trifluoromethylation–Allylation of Arynes4.2 1,2-Bis(trifluoromethylation) of Arynes5 Pentafluoroethylation of Unactivated Alkenes6 Conclusion

Mechanistic Insight into Copper-Mediated Trifluoromethylation of Aryl Halides: The Role of CuI.

The synthesis, characterization, and reactivity of key intermediates [Cu(CF3)(X)]-Q+ (X = CF3 or I, Q = PPh4) in copper-mediated trifluoromethylation of aryl halides were studied. Qualitative and quantitative studies showed [Cu(CF3)2]-Q+ and [Cu(CF3)(I)]-Q+ were not highly reactive. Instead, a much more reactive species, ligandless [CuCF3] or DMF-ligated species [(DMF)CuCF3], was generated in the presence of excess CuI. On the basis of these results, a general mechanistic map for CuI-promoted trifluoromethylation of aryl halides was proposed. Furthermore, on the basis of this mechanistic understanding, a HOAc-promoted protocol for trifluoromethylation of aryl halides with [Ph4P]+[Cu(CF3)2]- was developed.

Interrupting the Barton-McCombie Reaction: Aqueous Deoxygenative Trifluoromethylation of O-Alkyl Thiocarbonates.

The site-selective trifluoromethylation of aliphatic systems remains an important challenge. This work describes a light-driven, copper-mediated trifluoromethylation of O-alkyl thiocarbonates. The reaction provides broad functional group tolerance (e.g., alkyne, alkene, phenol, free alcohol, electron-rich and -deficient arenes), thereby offering orthogonality and practicality for trifluoromethylation. A radical organometallic mechanism is proposed.

Copper-Mediated Trifluoromethylation of Borylporphyrins Using an in situ-Generated CF3 Radical from NaSO2CF3 and tert-Butyl Hydroperoxide

Copper-Mediated Trifluoromethylation of Borylporphyrins Using an in situ-Generated CF3 Radical from NaSO2CF3 and tert-Butyl Hydroperoxide

Copper-Mediated Trifluoromethylation of Aryl Sulfonium Salts

Key words trifluoromethylation - photoredox catalysis - arylsulfonium salts

Copper-Mediated Trifluoromethylation-Allylation of Arynes.

An unprecedented three-component copper-mediated vicinal trifluoromethylation-allylation of arynes is described. A wide range of structurally diverse trifluoromethylated allylarenes can be quickly assembled in one step. The application of the method has been demonstrated in the expedient synthesis of the CF3-containing analogue of the antispasmodic drug papaverine. The new reactivity of the [CuCF3] reagent, which is generated from the inexpensive industrial byproduct fluoroform, is revealed with unique advantages.

Diverse copper(iii) trifluoromethyl complexes with mono-, bi- and tridentate ligands and their versatile reactivity.

Cu(iii) trifluoromethyl complexes are proposed as essential intermediates for many copper-promoted trifluoromethylation reactions, but remain elusive and scarcely explored. We report herein the isolation and spectroscopic and X-ray crystallographic characterization of diverse CuIII-CF3 complexes (6-10) with varied coordinating motifs (mono-, bi- or tridentate) and formal charges (neutral or monoanionic) for the ligand L (L is pyridine, 2,4,6-trimethylpyridine, quinol-8-yloxide or 2,6-bis(2'-pyridyl)pyridine). Square planar complexes 6, 7 and 9 show rapid dynamic behavior in solution possibly due to the weak Cu-CF3 bonds that can quickly dissociate and recombine with the CF3 radical. In contrast, 10, with octahedral geometry, is more rigid. Reactivity studies show that except for ion-pair complex 8, they are highly reactive for the trifluoromethylation of arylboronic acids and the C-H bond of terminal alkynes. Furthermore, syn-fluoro- and -oxy-trifluoromethylation across the triple bond of alkynes can be achieved using 6 and CsF or NaOPh. These results greatly expand the scope of isolated and well-characterized Cu(iii)-CF3 complexes, and establish their versatile reactivity that may be widely involved in copper-mediated trifluoromethylation reactions, thus substantiating the essential yet undeveloped aspects of trifluoromethylation chemistry.

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.

The Role of Ate Complexes in the Copper-Mediated Trifluoromethylation of Alkynes.

Trifluoromethylation reactions have recently received increased attention because of the beneficial effect of the trifluoromethyl group on the pharmacological properties of numerous substances. A common method to introduce the trifluoromethyl group employs the Ruppert-Prakash reagent, that is, Si(CH3 )3 CF3 , together with a copper(I) halide. We have applied this method to the trifluoromethylation of aromatic alkynes and used electrospray-ionization mass spectrometry to investigate the mechanism of these reactions in tetrahydrofuran, dichloromethane, and acetonitrile as well as with and without added 1,10-phenanthroline. In the absence of the alkyne component, the homoleptic ate complexes [Cu(CF3 )2 ](-) and [Cu(CF3 )4 ](-) were observed. In the presence of the alkynes RH, the heteroleptic complexes [Cu(CF3 )3 R](-) were detected as well. Upon gas-phase fragmentation, these key intermediates released the cross-coupling products R-CF3 with perfect selectivity. Apparently, the [Cu(CF3 )3 R](-) complexes did not originate from homoleptic cuprate anions, but from unobservable neutral precursors. The present results moreover point to the involvement of oxygen as the oxidizing agent.

Copper-mediated trifluoromethylation of diaryliodonium salts with difluoromethyltriflate

Abstract The reaction of diaryliodonium salts with difluoromethyltriflate in the presence of TBAT and CuTC gave the corresponding trifluoromethylated arenes in moderate yields. Compared to other difluorocarbene-derived trifluoromethylation reactions, the current one proceeded at mild reaction conditions (room temperature) within short reaction time (5 min).

Trifluoromethylation of (hetero)aryl iodides and bromides with copper(i) chlorodifluoroacetate complexes

A new copper-mediated trifluoromethylation of aryl halides using copper(i) chlorodifluoroacetate complexes as reagent has been developed.

Copper-mediated trifluoromethylation of diaryliodonium salts with TMSCF3 at room temperature

Abstract A convenient method for the preparation of trifluoromethylated arenes from the reaction of diaryliodonium salts with TMSCF3 in the presence of CuBF4·(MeCN)4 and KF at room temperature within 25 min was developed. This reaction provides a valuable complement to the previously established trifluoromethylation methods.

Copper-Mediated Radical Trifluoromethylation

Copper-Mediated Radical Trifluoromethylation

Copper-Mediated Trifluoromethylation

Copper-Mediated Trifluoromethylation

Copper-Mediated Trifluoromethylation Using Phenyl Trifluoromethyl Sulfoxide

A new method for the generation of trifluoromethylcopper ("CuCF3") species from readily available phenyl trifluoromethyl sulfoxide has been developed. The "CuCF3" reagent can be applied in efficient trifluoromethylations of aryl iodides and activated aryl bromides in the absence of additional ligands. Furthermore, the "CuCF3" species can also undergo oxidative cross-coupling with terminal alkynes and arylboronic acids.

Copper-Mediated E-Selective Trifluoromethylation of α,β-Unsaturated Hydrazones

Copper-Mediated E-Selective Trifluoromethylation of α,β-Unsaturated Hydrazones