Efficient Trifluoromethylation of Activated and Non-Activated Alkenyl Halides by Using (Trifluoromethyl)trimethylsilane

Electrochemical Decarboxylative Trifluoromethylation of Cinnamic Acids Revisited: A Combined Experimental and Computational Study

β-(Trifluoromethyl)styrenes are potentially useful building blocks for the synthesis of organofluorine compounds because their electron-deficient C=C double bonds can undergo diverse transformations. One of the most practical methods for preparing β-(trifluoromethyl)styrenes is the decarboxylative trifluoromethylation of readily available cinnamic acid derivatives using the Langlois reagent as a less expensive trifluoromethyl source. We revisited the electrochemical decarboxylative trifluoromethylation of cinnamic acid derivatives to identify modified conditions that reduce the loading of the Langlois reagent without additional additives. The reaction mechanism was computationally investigated to gain insight into the dependence of the product yields on the aryl terminal groups. The synthetic utility of the obtained β-(trifluoromethyl)styrenes was demonstrated by their transformation into 4-aryl-3-(trifluoromethyl)pyrrolidines.

Stereoselective synthetic approach toward β-trifluoromethyl vinyl ethers and diethers via reaction of (E)-1,2-dichloro-3,3,3-trifluoroprop-1-ene with phenols

A convenient method for synthesizing β-trifluoromethyl vinyl ethers and diethers through the base-mediated C-O coupling of (E)-1,2-dichloro-3,3,3-trifluoroprop-1-ene and phenols has been developed. Remarkably, the present process shows perfect regioselective and stereoselective yield of the Z/E isomers for β-trifluoromethyl vinyl ethers with high efficiency. Additionally, β-trifluoromethyl vinyl diethers with identical/diverse phenoxy groups were also obtained and the regulation of the product configuration was achieved. These reactions feature transition-metal-free conditions, wide substrate scope, and atom economy.

gem-Difluoroallene (DFA): an emerging versatile synthetic precursor to enable diverse fluorinated molecules

Organofluorine compounds are increasingly found in diverse fields, such as pharmaceuticals, agrochemicals, and materials science. gem-Difluoroallenes, which have gem-difluoro alkenes and allenes-like properties, offer a distinct and adaptable platform for novel synthetic transformations. Their distinctiveness is highlighted by various strategies, where the gem-difluoro group's presence plays a pivotal role in successful reactions. This review article presents a comprehensive overview of the latest progress in utilizing gem-difluoroallenes for selective additions, defluorination, as well as cycloaddition and cyclization reactions. We also discuss the limitations and future directions in this area, inspiring further exploration and innovation.

Hydroxylamine-Mediated C(sp2)-H Trifluoromethylation of Terminal Alkenes

Introduction of the trifluoromethyl (CF3) group into organic compounds has garnered substantial interest because of its significant role in pharmaceuticals and agrochemicals. Here, we report a hydroxylamine-mediated radical process for C(sp2)-H trifluoromethylation of terminal alkenes. The reaction shows good reactivity, impressive E/Z selectivity (up to >20 : 1), and broad functional group compatibility. Expansion of this approach to perfluoroalkylation and late-stage trifluoromethylation of bioactive molecules demonstrates its promising application potential. Mechanistic studies suggest that the reaction follows a radical addition and subsequent elimination pathway.

Z-Selective access to α-trifluoromethyl arylenes through Pd-catalysed fluoroarylation of 1,1-difluoroallenes

The synthesis of stereo-defined α-trifluoromethyl arylenes is of great importance in medical chemistry, organic chemistry, and materials science. However, despite the recent advances, the Z-selective formation of α-trifluoromethyl arylenes has remained underdeveloped. Here, we describe a facile approach towards Z-α-trifluoromethyl arylenes through Pd-catalysed stereoselective fluoroarylation of 1,1-difluoroallenes in the presence of a bulky monophosphine ligand.

Rhodium-Catalyzed Anti-Markovnikov Transfer Hydroiodination of Terminal Alkynes

A rhodium-catalyzed anti-Markovnikov hydroiodination of aromatic and aliphatic terminal alkynes is reported. Depending on the choice of ligand and substrate, either (E)- or (Z)-configured alkenyl iodides are obtained in high to exclusive isomeric purity. The reaction exhibits a broad substrate scope and high functional group tolerance, employing easily accessible or commercially available aliphatic iodides as HI surrogates through a shuttle process. The synthesized vinyl iodides were applied in several C-C and C-heteroatom bond-forming reactions with full retention of the stereoselectivity. The developed method could be used to significantly shorten the total synthesis of a marine cis-fatty acid. Additionally, initial deuterium-labeling experiments and stoichiometric reactions shed some light on the potential reaction mechanism.

Copper-Catalyzed Regioselective Olefination and Trifluoromethylation of Carboxylic Acids To Give (Z)-Trifluoromethyl Enol Esters

Herein, we describe a method to produce (Z)-trifluoromethyl enol esters via the olefination and trifluoromethylation of carboxylic acids with TMSCF₃. This synthetic method uses inexpensive and easy-to-handle TMSCF₃. It employs a commercially available CuCl catalyst to transform a broad range of carboxylic acids into versatile (Z)-trifluoromethyl enol esters with good regio- and stereoselectivity. This protocol allows the concise synthesis of highly functionalized (Z)-trifluoromethyl enol esters directly from carboxylic acids.

Organocatalytic Synthesis of α-Trifluoromethyl Allylboronic Acids by Enantioselective 1,2-Borotropic Migration

Chiral α-substituted allylboronic acids were synthesized by asymmetric homologation of alkenylboronic acids using CF₃/TMS-diazomethanes in the presence of BINOL catalyst and ethanol. The chiral α-substituted allylboronic acids were reacted with aldehydes or oxidized to alcohols in situ with a high degree of chirality transfer. The oxygen-sensitive allylboronic acids can be purified via their isolated diaminonaphthalene (DanH)-protected derivatives. The highly reactive purified allylboronic acids reacted in a self-catalyzed reaction at room temperature with ketones, imines, and indoles to give congested trifluoromethylated homoallylic alcohols/amines with up to three contiguous stereocenters.

(Z)-Trifluoromethyl-Trisubstituted Alkenes or Isoxazolines: Divergent Pathways from the Same Allene

Because of a charge-dipole interaction involving nonbonding electron pairs on fluorine, protonation of trifluoromethyl allenes leads to tri- or tetrasubstituted alkenes with high (Z)-selectivity. Treatment of the same allenes with catalytic Au(I) initiates a reaction cascade that produces isoxazolines in high yield.

Photoredox-Catalyzed Selective Synthesis of Allylic Perfluoroalkanes from Alkenes

We report herein a novel photoredox-catalyzed synthesis of allylic trifluoromethanes. The use of sulfilimino iminium as a source of trifluoromethyl radicals proves crucial to achieving high selectivity. Importantly, both styrene derivatives and unactivated alkenes are for the first time suitable partners for this process. The mild reaction conditions are compatible with a variety of functional groups. Remarkably, this method is readily broadened to other perfluoroalkyl groups (R_F =CFCl₂ , CF₂ Br, C₄ F₉ ). An extensive mechanistic study is also provided.

Rapid Syntheses of [11C]Arylvinyltrifluoromethanes through Treatment of (E)-Arylvinyl(phenyl)iodonium Tosylates with [11C]Trifluoromethylcopper(I)

We report a method for labeling arylvinyltrifluoromethanes with carbon-11 (t_1/2 = 20.4 min) as representatives of a new radiolabeled chemotype that has potential for developing radiotracers for biomedical imaging with positron emission tomography. Treatment of (E)-arylvinyl(phenyl)iodonium tosylates (1a-1k) with [¹¹C[CuCF₃ gave the corresponding [¹¹C]arylvinyltrifluoromethanes ([¹¹C]2a-[¹¹C]2k) in high radiochemical yields (90-97%) under rapid (2 min) and mild (60 °C) conditions.

Recent advances in direct trifluoromethylation of olefinic C-H bonds

The aim of this review is to provide a comprehensive overview of the direct trifluoromethylation of olefinic C-H bonds with special attention on the mechanistic aspects of the reactions. The review is divided into two major sections. The first focuses exclusively on trifluoromethylation of terminal alkenes, while the second will cover trifluoromethylation of internal alkenes. Literature has been surveyed until the end of April 2019.

Fluoroalkenylation of boronic acids via an oxidative Heck reaction

A fluoroalkenylation of boronic acids with fluoroalkyl alkenes has been developed. The Pd-catalyzed oxidative Heck coupling reaction proceeds under an oxygen atmosphere at room temperature, in the absence of a base and/or a ligand, showing excellent practicality of the process. This simple transformation is highly stereoselective to provide only E-isomers. In addition to the general approach using alkenes with functionalized fluoroalkyl reagents, this method, by transferring an aromatic system to the electron-deficient fluoroalkyl alkene, provides an efficient alternative method to yield valuable organofluorines.

Iron-catalyzed ortho trifluoromethylation of anilines via picolinamide assisted photoinduced C-H functionalization

A convenient, oxidant-free protocol was developed for the ortho trifluoromethylation of aniline via picolinamide assisted Fe-promoted C-H functionalization under ultraviolet irradiation. In this transformation acetone essentially acted as both a solvent to dissolve reactants and a low-cost radical initiator to efficiently generate a CF3 radical from Langlois' reagent. A broad substrate scope was tolerated and picolinamide bearing strong electron withdrawing groups also could be transformed into the corresponding products with acceptable yields. Furthermore, the value of this method has been highlighted via the efficient synthesis of the nonsteroidal anti-inflammatory drug floctafenine.

Synthesis of α-Trifluoromethylacrylates by Ligand-Free Palladium-Catalyzed Mizoroki-Heck Reaction

Efficient ligand-free palladium catalyzed Mizoroki-Heck reaction allowed the formation of trisubstituted α-trifluoromethylacrylates. The reaction showed good chemical tolerance and furnished moderate to excellent yields of reaction. Silver salt additive proved to be essential for the reaction. The reaction has been then applied to the formation of 3-trifluoromethyl coumarins and analogues of therapeutic agents.

Syntheses of 2-(2,2,2-trifluoroethylidene)/(2,2-difluoroethyl)-1,3-dicarbonyl compounds and their fungicidal activities

A Knoevenagel-type reaction of 1,3-diketone substrates with trifluoroacetic/difluoroacetic anhydride for the synthesis of 2-(2,2,2-trifluoroethylidene)/(2,2-difluoroethyl)-1,3-dicarbonyl compounds has been developed.

From C1 to C2 : TMSCF3 as a Precursor for Pentafluoroethylation

A highly efficient copper-mediated aromatic pentafluoroethylation method using TMSCF₃ as the sole fluoroalkyl source is described. The reaction proceeds by a key C₁ to C₂ process, that is, the generation of CuCF₃ from TMSCF₃ , followed by a subsequent spontaneous transformation into CuC₂ F₅ . Various aryl iodides were pentafluoroethylated with the TMSCF₃ -derived CuC₂ F₅ . This method represents the first practical and efficient method for pentafluoroethylation of aryl iodides using commercially available TMSCF₃ as a pentafluoroethyl precursor.

Trifluoromethylation of Electron-Rich Alkenyl Iodides with Fluoroform-Derived "Ligandless" CuCF3

We herein present a flexible approach for the incorporation of CF₃ units into a predefined site of electron-rich alkenes that exploits the regiocontrolled introduction of an iodine handle and subsequent trifluoromethylation of the C(sp²)-I bond using fluoroform-derived "ligandless" CuCF₃. The broad substrate scope and functional group tolerance together with the scalability and purity of the resulting products enabled the controlled, late-stage synthesis of single regioisomers of complex CF₃-scaffolds, such as sugars, nucleosides (antivirals), and heterocycles (indoles and chromones), with potential for academic and industrial applications.

Copper-catalyzed trifluoromethylation of styrene derivatives with CF3SO2Na

A radical-type copper(i)-catalyzed direct trifluoromethylation of styrene derivatives using CF₃SO₂Na as a trifluoromethylating source for accessing trifluoromethylated alkenes has been developed.

Metal-free radical trifluoromethylation of β-nitroalkenes through visible-light photoredox catalysis

First report an efficient catalytic conversion of nitroalkenes to 1-trifluoromethyalkenes under metal-free visible-light photoredox catalysis is disclosed.

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.

Highly efficient synthesis of polyfluorinated dendrons suitable for click chemistry

A new and efficient access to C_2v-symmetric dendrons with up to 72 magnetically equivalent fluorine atoms is presented. Those dendrons are well suited to act as potential ¹⁹F MRI probes.

Metal-free radical perfluoroalkylation of (hetero)arenes

We report a metal-free radical perfluoroalkylation method which uses inexpensive and commercially available perfluorocarboxylic anhydrides as an easy to use source of perfluoroalkyl radicals.

Direct C-H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis

Background: Trifluoromethylated alkene scaffolds are known as useful structural motifs in pharmaceuticals and agrochemicals as well as functional organic materials. But reported synthetic methods usually require multiple synthetic steps and/or exhibit limitation with respect to access to tri- and tetrasubstituted CF₃-alkenes. Thus development of new methodologies for facile construction of C_alkenyl–CF₃ bonds is highly demanded.

Results: The photoredox reaction of alkenes with 5-(trifluoromethyl)dibenzo[b,d]thiophenium tetrafluoroborate, Umemoto’s reagent, as a CF₃ source in the presence of [Ru(bpy)₃]²⁺ catalyst (bpy = 2,2’-bipyridine) under visible light irradiation without any additive afforded CF₃-substituted alkenes via direct C_alkenyl–H trifluoromethylation. 1,1-Di- and trisubstituted alkenes were applicable to this photocatalytic system, providing the corresponding multisubstituted CF₃-alkenes. In addition, use of an excess amount of the CF₃ source induced double C–H trifluoromethylation to afford geminal bis(trifluoromethyl)alkenes.

Conclusion: A range of multisubstituted CF₃-alkenes are easily accessible by photoredox-catalyzed direct C–H trifluoromethylation of alkenes under mild reaction conditions. In particular, trifluoromethylation of triphenylethene derivatives, from which synthetically valuable tetrasubstituted CF₃-alkenes are obtained, have never been reported so far. Remarkably, the present facile and straightforward protocol is extended to double trifluoromethylation of alkenes.

Methylenation of perfluoroalkyl ketones using a Peterson olefination approach

An operationally simple, inexpensive, and rapid route for the olefination of a wide array of trifluoromethyl ketones to yield 3,3,3-trifluoromethylpropenes is reported. Using a Peterson olefination approach, the reaction gives good to excellent yields of the alkene products and can be performed without purification of the β-hydroxysilyl intermediate. The reaction can be extended to other perfluoroalkyl substituents and is easily scaled up. The alkenes prepared can be readily transformed into a variety of other perfluoroalkyl-containing compounds.