Access to a new class of synthetic building blocks via trifluoromethoxylation of pyridines and pyrimidines

Copper-catalyzed three-component cyclization of amidines, styrenes, and fluoroalkyl halides for the synthesis of modular fluoroalkylated pyrimidines

An efficient copper-catalyzed three-component cyclization for the construction of highly functionalized pyrimidine derivatives from amidines, styrenes and fluoroalkyl halides is developed.

Synthesis of heteroaromatic trifluoromethyl ethers with trifluoromethyl triflate as the source of the trifluoromethoxy group

A series of nitrogen-heterocycles have been transformed to the corresponding trifluoromethyl and higher perfluoroalkyl ethers by the reaction of the N-oxides with trifluoromethyl triflate as a bifunctional reagent.

Asymmetric synthesis of α-trifluoromethoxy ketones with a tetrasubstituted α-stereogenic centre via the palladium-catalyzed decarboxylative allylic alkylation of allyl enol carbonates

The Pd-catalyzed asymmetric decarboxylative allylic alkylation of trifluoromethoxy allyl enol carbonates is disclosed.

Direct Dehydroxytrifluoromethoxylation of Alcohols

The first example of a direct dehydroxytrifluoromethoxylation of alcohols has been developed. This method generated an alkyl fluoroformate in situ from alcohols, followed by nucleophilic trifluoromethoxylation with trifluoromethyl arylsulfonate (TFMS) as the trifluoromethoxylation reagent. The reaction is operationally simple and scalable, and it proceeds under mild reaction conditions to provide access to a wide range of trifluoromethyl ethers from alcohols. In addition, this method is suitable for the late-stage trifluoromethoxylation of complex small molecules.

Fluoroalkyl Amino Reagents for the Introduction of the Fluoro(trifluoromethoxy)methyl Group onto Arenes and Heterocycles

Fluoroalkyl amino reagents 1a and 2a have been developed from commercially available trifluoromethyl trifluorovinyl ether via a hydroamination reaction with diethylamine or dimethylamine. These reagents can be activated by treatment with a Lewis acid and subsequently used as a mono- or dielectrophile for the introduction of the fluoro(trifluoromethoxy)methyl group, either in Vilsmeier-type acylations of aromatic substrates or in the synthesis of fluorinated pyrazoles from CH-acidic substrates and of bis-fluorinated pyrazoles, all being important building blocks for medicinal and agricultural chemistry.

Dichlorotrifluoromethoxyacetic Acid: Preparation and Reactivity

We describe the first gram scale preparation of the reagent dichlorotrifluoromethoxyacetic acid. This stable compound is obtained in five steps starting from the cheap diethylene glycol. The reactivity of the sodium salt of this fluorinated acid was also tested and allowed the preparation of new amides.

Selective C-O bond formation via a photocatalytic radical coupling strategy: access to perfluoroalkoxylated (ORF) arenes and heteroarenes

Synthesis of perfluoroalkoxylated (hetero)arenes (Ar–OR_F) from readily available perfluoroalkyl iodides (R_F–I) through photocatalytic selective O–R_F bond formation.

Development of an efficient process that employs commercially available and cost effective reagents for the synthesis of perfluoroalkoxylated aromatic compounds (Ar–OR_F) remains a daunting challenge in organic synthesis. Herein, we report the first catalytic protocol using readily available perfluoroalkyl iodides (R_FI) and N-(hetero)aryl-N-hydroxylamides to access a wide range of perfluoroalkoxylated (hetero)arenes. Mild reaction conditions allow for selective O–R_F bond formation over a broad substrate scope and are tolerant of a wide variety of functional groups. Mechanistic studies suggest the formation and recombination of persistent N-hydroxyl radicals and transient R_F radicals under photocatalytic reaction conditions to generate N–OR_F compounds that rearrange to afford the desired products.

Cationic N-Heterocyclic Carbene Copper-Catalyzed [1,3]-Alkoxy Rearrangement of N-Alkoxyanilines

The [1,3]-alkoxy rearrangement reactions of N-alkoxyanilines were efficiently catalyzed by cationic N-heterocyclic carbene (NHC)-Cu catalysts in affording 2-alkoxyaniline derivatives in good to excellent yields with high functional group compatibility. For N-alkoxyanilines having an electron-withdrawing substituent at the meta-position, the alkoxy group selectively migrated to the more hindered ortho-position. In contrast, the alkoxy group migrated to the less hindered ortho-position for N-alkoxyanilines having an electron-donating substituent. Mechanistic studies suggest that the rearrangement reactions proceed via an intramolecular route.

Asymmetric silver-catalysed intermolecular bromotrifluoromethoxylation of alkenes with a new trifluoromethoxylation reagent

Fluorinated organic compounds are becoming increasingly important in pharmaceuticals, agrochemicals and materials science. The introduction of trifluoromethoxy groups into new drugs and agrochemicals has attracted much attention due to their strongly electron-withdrawing nature and high lipophilicity. However, synthesis of trifluoromethoxylated organic molecules is difficult owing to the decomposition of trifluoromethoxide anion and β-fluoride elimination from transition-metal-trifluoromethoxide complexes, and no catalytic enantioselective trifluoromethoxylation reaction has been reported until now. Here, we present an example of an asymmetric silver-catalysed intermolecular bromotrifluoromethoxylation of alkenes with trifluoromethyl arylsulfonate (TFMS) as a new trifluoromethoxylation reagent. Compared to other trifluoromethoxylation reagents, TFMS is easily prepared and thermally stable with good reactivity. In addition, this reaction is operationally simple, scalable and proceeds under mild reaction conditions. Furthermore, broad scope and good functional group compatibility has been demonstrated by application of the method to the bromotrifluoromethoxylation of double bonds in natural products and natural product derivatives.

Synthetic Approaches to Trifluoromethoxy-Substituted Compounds

Because of the unique properties of the trifluoromethoxy group, molecules bearing this moiety will find applications in various fields, particularly in the life sciences. However, despite the great interest in this functional group, only a small number of trifluoromethoxylated molecules are currently synthetically accessible. Over the last few years, several innovative and promising strategies for the synthesis of trifluoromethoxylated compounds have been described. This Minireview discusses these existing methods with a particular focus on more recent advances.

O-Trifluoromethylation of Phenols: Access to Aryl Trifluoromethyl Ethers by O-Carboxydifluoromethylation and Decarboxylative Fluorination

A new strategy for the synthesis of aryl trifluoromethyl ethers (ArOCF3) by combining O-carboxydifluoromethylation of phenols and subsequent decarboxylative fluorination is reported. This protocol allows easy construction of functionalized trifluoromethoxybenzenes and trifluoromethylthiolated arenes (ArSCF3) in moderate to good yields. Moreover, it utilizes accessible and inexpensive reagents sodium bromodifluoroacetate and SelectFluor II and, thus, is practical for O-trifluoromethylation of phenols. The potential application of this method is demonstrated with the preparation of a plant-growth regulator, Flurprimidol.

Direct Difluoromethylation of Alcohols with an Electrophilic Difluoromethylated Sulfonium Ylide

A general method for the formation of alkyl difluoromethylethers under mild reaction conditions and with good functional-group tolerance was developed. The development of the method was based on the invention of a stable, electrophilic, difluoromethylating reagent, difluoromethyl-(4-nitrophenyl)-bis(carbomethoxy) methylide sulfonium ylide, which was synthesized by reaction of the easily available 4-nitrophenyl (difluoromethyl)thioether and dimethyl diazomalonate in the presence of a rhodium catalyst.

Mechanistic studies on intramolecular C-H trifluoromethoxylation of (hetero)arenes via OCF3-migration

The one-pot two-step intramolecular aryl and heteroaryl C-H trifluoromethoxylation recently reported by our group has provided a general, scalable, and operationally simple approach to access a wide range of unprecedented and valuable OCF3-containing building blocks. Herein we describe our investigations to elucidate its reaction mechanism. Experimental data indicate that the O-trifluoromethylation of N-(hetero)aryl-N-hydroxylamine derivatives is a radical process, whereas the OCF3-migration step proceeds via a heterolytic cleavage of the N-OCF3 bond followed by rapid recombination of a short-lived ion pair. Computational studies further support the proposed ion pair reaction pathway for the OCF3-migration process. We hope that the current study would provide useful insights for the development of new transformations using versatile N-(hetero)aryl-N-hydroxylamine synthons.

Silver-mediated direct trifluoromethoxylation of α-diazo esters via the (-)OCF3 anion

Silver-mediated direct trifluoromethoxylation of α-diazo esters and ketosteroid was disclosed. The reactions of alkyl α-diazo arylacetates with AgOCF3 or CF3SO2OCF3/AgF at -30 to 10 °C under a N2 atmosphere provided α-trifluoromethoxyl arylacetates in up to 90% yield, while alkyl α-diazo vinylacetates reacting with CF3SO2OCF3/AgF or AgOCF3 afforded γ-trifluoromethoxyl α,β-unsaturated esters in up to 94% yield. The α-diazo ketosteroid was also trifluoromethoxylated under the standard reaction conditions. This protocol allows for an effective and convenient access to a large number of synthetic building blocks, which are promising in the development of new functional OCF3-molecules.

Synthesis of Trifluoromethoxylated (Hetero)Arenes via OCF3 Migration

Incorporation of the OCF3 group into organic molecules, especially aromatic and heteroaromatic compounds, is recognized as one of the major challenges in synthetic organic chemistry. Although many attempts have been made to develop efficient trifluoromethoxylation strategies, most of the current approaches still require use of highly toxic, thermally unstable reagents, or impractical reaction conditions. Herein, we highlight a recent contribution from our group towards the synthesis of (hetero)aryltrifluoromethyl ethers. Our protocol is scalable, operationally simple, and allows an easy access to a wide range of synthetically useful ortho-OCF3 aniline derivatives, as well as functionalized trifluoromethoxylated pyridines and pyrimidines under mild reaction conditions.

New entries toward the synthesis of OCF3-containing molecules

The OCF₃ group is of high interest in the quest for new drugs and agrochemicals, thanks to its atypical features. This Highlight article depicted the recent and impressive advances toward the synthesis of OCF₃-containing molecules.