Synthesis of N-CF3 Alkynamides and Derivatives Enabled by Ni-Catalyzed Alkynylation of N-CF3 Carbamoyl Fluorides

Photoredox-Catalyzed Trifluoromethylamination of Alkenes with Concomitant Introduction of a Quinoxalin-2(1H)-one Moiety

A photoredox-catalyzed strategy for the difunctionalization of alkenes with quinoxalin-2(1H)-ones and N-CF3 hydroxylamine reagents was developed. This reaction was carried out under photoirradiation conditions, affording the corresponding three-component coupling products in moderate to high yields with excellent regioselectivity. It provides a new protocol to access valuable quinoxalin-2(1H)-one derivatives containing a N-CF3 group.

Nitrogen-Based Organofluorine Functional Molecules: Synthesis and Applications

Fluorine and nitrogen form a successful partnership in organic synthesis, medicinal chemistry, and material sciences. Although fluorine-nitrogen chemistry has a long and rich history, this field has received increasing interest and made remarkable progress over the past two decades, driven by recent advancements in transition metal and organocatalysis and photochemistry. This review, emphasizing contributions from 2015 to 2023, aims to update the state of the art of the synthesis and applications of nitrogen-based organofluorine functional molecules in organic synthesis and medicinal chemistry. In dedicated sections, we first focus on fluorine-containing reagents organized according to the type of fluorine-containing groups attached to nitrogen, including N-F, N-RF, N-SRF, and N-ORF. This review also covers nitrogen-linked fluorine-containing building blocks, catalysts, pharmaceuticals, and agrochemicals, underlining these components' broad applicability and growing importance in modern chemistry.

Access to N-Monofluoromethylated (Thio)Carbamates, Formamides, Alkynamides, and Related Derivatives

This work presents the first general synthetic access to N-CH₂F and N-CHRF carbamates, thiocarbamates, formamides, alkynamides, and related compounds. The synthetic approach employs N-CH2F and N-CHRF carbamoyl fluorides as versatile strategic building blocks, which can be efficiently synthesized in a single step directly from readily available amines or imines.

eFluorination for the Rapid Synthesis of Fluorothioformates from Oxalic Acid Monothioesters

An efficient and practical electrochemical method for synthesizing fluorothioformate derivatives, an underexplored functional group, is reported. The strategy is based on the anodic decarboxylation of oxalic acid monothioesters, which rapidly generates highly reactive alkyl (oxomethylidene)sulfonium intermediates. These intermediates are effectively trapped by the inexpensive and commercially available triethylamine trihydrofluoride (Et3N·3HF), which acts as both a nucleophilic fluoride source and a supporting electrolyte, leading to the formation of the desired fluorothioformates. This methodology enables the rapid and scalable synthesis of fluorothioformate derivatives, enabling their broader exploration in organic chemistry. In particular, these compounds can be readily and selectively converted to S-thiocarbamates and urea derivatives in a one-pot process through reactions with amines, demonstrating their synthetic utility. The scalability of this electrochemical fluorination was validated, showing no loss of yield. Cyclic voltammetry studies were carried out to shed some light on the mechanism of these novel transformations.

Desulfurizative Fluorination of N-CF3 Thioformamides for the Efficient Synthesis of N(CF3)(CF2H) Amines with Enhanced Stability

With poor metabolic stability being a major cause of failure in drug development, there is a pressing need for strategic molecular modifications to optimize for desired properties and function. N-substitution has emerged as a powerful approach, with N-CF3 amines previously demonstrating enhanced lipophilicity and reduced susceptibility to oxidation, albeit inherent instability to hydrolysis. This report discloses the further evolution of this motif-the introduction of an additional N-difluoromethyl unit, resulting in an extraordinary 2000-fold increase in stability. We present the first general synthetic strategy for accessing N(CF3)(CF2H) amines. The method relies on an operationally simple desulfurization-fluorination strategy of N-CF3 thioformamides and is characterized by broad functional group tolerance.

A Photo- and Electrochemistry-Triggered Redox-Neutral Cyclization Strategy to Access Cyclic N-CF3 Amides

While the construction of N-CF3 amides has seen significant progress, the current synthetic repertoire is largely limited to noncyclic variants. Here, we report synthetic access to N-CF3 isoindolinones. The developed redox-neutral cyclization leverages amino acid-derived N-CF3 redox-active esters under photo- or electrochemical activation. Mechanistic studies reveal that N-CF3 uniquely enables this disconnection through its distinct electronic impact, which enhances conformational flexibility and lowers the propensity for overoxidation.

Facile Synthesis of Carbamoyl Fluorides via N-Carbamoylimidazole Activation

The untapped potential of carbamoyl fluorides for various chemico/biological applications is hampered by the scarcity of straightforward and benign methods for their synthesis. In this report, we disclose a novel mild three-step procedure that avoids exotic, corrosive, and highly toxic reagents. Briefly, commercially available secondary amines are carbamoylated with 1,1'-carbonyldiimidazole, followed by alkylation to improve nucleofugality, and exchange with inorganic KF. This procedure works on a gram scale without chromatographic purification. It is however limited to basic, sterically unhindered secondary amines without alkylation-prone functional groups.

N-Halosuccinimide enables cascade oxidative trifluorination and halogenative cyclization of tryptamine-derived isocyanides

Both the pyrroloindoline core and N-CF3 moiety hold significant importance in medicinal chemistry. However, to date, no instances of constructing N-CF3-containing pyrroloindolines have been reported. Herein, we present a robust and operationally simple approach to assembling such intriguing skeletons from tryptamine-derived isocyanides through a cascade sequence, which includes an oxidative trifluorination and a subsequent halogenative cyclization. Key to the success lies in the development of a facile conversion of isocyanides to N-CF3 moiety with commercially available reagents N-halosuccinimide and Et3N·HF. The protocol features mild reaction conditions, broad functional group tolerance, good to excellent yields, and high diastereoselectivities. In addition, we demonstrate that the halide substituent within the products serves as a versatile functional handle for accessing diverse C3-quaternary-substituted N-CF3-pyrroloindolines.

Synthesis of Diverse N-Trifluoromethyl Pyrazoles by Trapping of Transiently-Generated Trifluoromethylhydrazine

A one-pot synthesis of functionalized N-trifluoromethyl pyrazoles from readily available di-Boc trifluoromethylhydrazine and dialdehydes, diketones, carbonylnitriles, and ketoesters/amides/acids is described. 19F NMR studies were used to characterize the stability of trifluoromethylhydrazine HCl salt in solution and in solid form and identified a short solution-state half-life of ∼6 h. Optimization of cyclization conditions identified DCM, combined with a strong acid, as a key to suppress the undesired des-CF3 side products, which formed as a result of the instability of trifluoromethylhydrazine and related intermediates. Despite the short-lived nature of these transient intermediates, their reactivity could be utilized to directly deliver a diverse array of pharmaceutically relevant N-trifluoromethyl pyrazoles in synthetically useful yields.

Diversified Reactivity of Triphenylphosphine: Reinvestigation of the Phosphine-Mediated Reductive Condensation Approach for the Synthesis of Substituted Furans

A reinvestigation of "Phosphine-Mediated Reductive Condensation of γ-Acyloxy Butynoates: A Diversity Oriented Strategy for the Construction of Substituted Furans" (J. Am. Chem. Soc. 2004, 126, 4118-4119) revealed different chemoselectivity of triphenylphosphine in the reactions with the γ-acyloxy butynoate substrates of varying substitution patterns/electronics. Furthermore, the electronics of the triaryl phosphine reagent could be tuned to trap a putative intermediate such as A, leading to the semihydrogenation of propiolamide substrates.

Recent Advances in the Synthesis of N-fluoroalkyl Amides/Sulfonamides and Their Carbonyl/Sulfonyl Derivatives

Organofluorine compounds have consistently demonstrated practical applications in the life sciences due to the fascinating properties imparted by the fluorine substituents. In recent years, significant advancements have been made in the synthesis of N-fluoroalkyl carbonyl and sulfonyl compounds. This review offers a current overview of the various synthetic routes for N-fluoroalkyl amides/sulfonamides and their transformation to new unexplored N-fluoroalkyl carbonyl/sulfonyl derivatives, categorized into three parts based on the different fluoroalkyl groups.

N-CF3 Imidoyl Chlorides: Scalable N-CF3 Nitrilium Precursors for the Construction of N-CF3 Compounds

A wide range of N-CF3 imidoyl chlorides were synthesized for the first time via the N-trifluoromethylation of nitriles in DCM by using AlCl3-activated PhICF3Cl as the CF3 source. The reactions of them with N-/O-/S-nucleophiles, as well as with 1,3-dipoles, were carried out to efficiently deliver N-CF3 amidines/imidates/thioimidates and N-CF3 azoles, demonstrating that they are a class of scalable NCF3-containing synthons in the synthesis of N-CF3 compounds.

Access to N-Difluoromethyl Amides, (Thio)Carbamates, Ureas, and Formamides

The first efficient access to N-difluoromethyl amides, carbamates, thiocarbamates, ureas, formamides, and their derivatives is reported herein. The synthetic strategy relies on the initial synthesis and straightforward derivatization of N-CF2H carbamoyl fluorides, which were prepared through a desulfurization-fluorination of thioformamides (─NH─C(H)═S) coupled with carbonylation. The newly made N-CF2H carbonyl compounds proved to be highly robust and compatible with numerous chemical transformations and downstream derivatizations, underscoring the potential of this novel motif as a building block in complex functional molecules.

Synthetic Advantages of Defluorinative C-F Bond Functionalization

Much progress has been made in the development of methods to both create compounds that contain C-F bonds and to functionalize C-F bonds. As such, C-F bonds are becoming common and versatile synthetic functional handles. This review summarizes the advantages of defluorinative functionalization reactions for small molecule synthesis. The coverage is organized by the type of carbon framework the fluorine is attached to for mono- and polyfluorinated motifs. The main challenges, opportunities and advances of defluorinative functionalization are discussed for each class of organofluorine. Most of the text focuses on case studies that illustrate how defluorofunctionalization can improve routes to synthetic targets or how the properties of C-F bonds enable unique mechanisms and reactions. The broader goal is to showcase the opportunities for incorporating and exploiting C-F bonds in the design of synthetic routes, improvement of specific reactions and advent of new methods.

General Synthesis of N-CF3 Heteroaryl Amides via Successive Fluorination and Acylation of Sterically Hindered Isothiocyanates

We report the one-pot synthesis of N-CF3 heteroaryl amides (NTFMHA) from heteroaryl carboxylic acids and sterically hindered isothiocyanates, including various amino acid analogues, in the presence of AgF. The key to this reaction is the utilization of free heteroaryl acyl chlorides, rather than their corresponding hydrochloride salts. This method represents a complementary method of our previous work and enables modification to a variety of previously inaccessible structures, including α-tertiary amines and N-CF3-modified pharmaceuticals.

Fluoride-Catalyzed Cross-Coupling of Carbamoyl Fluorides and Alkynylsilanes

We report the synthesis of alkynamides via the cross-coupling of carbamoyl fluorides and alkynylsilanes catalyzed by tetrabutylammonium fluoride (TBAF). In contrast to previously reported transformations of carbamoyl fluorides, C-F bond cleavage is achieved under exceptionally mild conditions (room temperature, low catalyst loadings, and short reaction times) without the need for strongly nucleophilic reagents and/or catalysts. This method offers distinct advantages over transition-metal-catalyzed approaches, such as tolerance to aryl halide moieties and complementary chemoselectivity.

Recent Advances in the Syntheses of N-CF3 Scaffolds up to Their Valorization

This review provides a recent overview of the different synthetic routes of the N-CF3 group. This scaffold can be prepared from the desulfurization of thiocabamoyl fluorides or isothiocyanates with fluoride ions. Electrophilic and radical trifluoromethylations are also a great way to generate this motif. This report also focuses on the valorization of some N-CF3 compounds, which leads to new unknown N-trifluoromethyl derivatives. Finally, the first metabolic stability studies will be given for certain structures.

Recent Advances in the Synthesis and Transformation of Carbamoyl Fluorides, Fluoroformates, and Their Analogues

Carbamoyl fluorides, fluoroformates, and their analogues are a class of important compounds and have been evidenced as versatile building blocks for the preparation of useful molecules in organic chemistry. While major achievements were made in the synthesis of carbamoyl fluorides, fluoroformates, and their analogues in the last half of 20th century, an increasing number of reports have focused on using O/S/Se=CF2 species or their equivalents as the fluorocarbonylation reagents for the direct construction of these compounds from the parent heteroatom-nucleophiles in recent years. This review mainly summarizes the advances in the synthesis and typical application of carbamoyl fluorides, fluoroformates, and their analogues by the halide exchanges and fluorocarbonylation reactions since 1980.

BF3-Catalyzed Intramolecular Fluorocarbamoylation of Alkynes via Halide Recycling

A BF₃-catalyzed atom-economical fluorocarbamoylation reaction of alkyne-tethered carbamoyl fluorides is reported. The catalyst acts as both a fluoride source and Lewis acid activator, thereby enabling the formal insertion of alkynes into strong C-F bonds through a halide recycling mechanism. The developed method provides access to 3-(fluoromethylene) oxindoles and γ-lactams with excellent stereoselectivity, including fluorinated derivatives of known protein kinase inhibitors. Experimental and computational studies support a stepwise mechanism for the fluorocarbamoylation reaction involving a turnover-limiting cyclization step, followed by internal fluoride transfer from a BF₃-coordinated carbamoyl adduct. For methylene oxindoles, a thermodynamically driven Z-E isomerization is facilitated by a transition state with aromatic character. In contrast, this aromatic stabilization is not relevant for γ-lactams, which results in a higher barrier for isomerization and the exclusive formation of the Z-isomer.

A Brief Review on the Synthesis of the N-CF3 Motif in Heterocycles

The trifluoromethyl group is widely recognized for its significant role in the fields of medicinal chemistry and material science due to its unique electronic and steric properties that can alter various physiochemical properties of the parent molecule, such as lipophilicity, acidity, and hydrogen bonding capabilities. Compared to the well-established C-trifluoromethylation, N-trifluoromethylation has received lesser attention. Considering the extensive contribution of nitrogen to drug molecules, it is predicted that constructing N-trifluoromethyl (N-CF3) motifs will be of great significance in pharmaceutical and agrochemical industries. This review is mainly concerned with the synthesis of heterocycles containing this motif. In three-membered heterocycles containing the N-CF3 motif, the existing literature mostly demonstrated the synthetic strategy, as it does for four- and larger-membered heterocycles. Certain structures, such as oxaziridines, could serve as an oxidant or building blocks in organic synthesis. In five-membered heterocycles, it has been reported that N-CF3 azoles showed a higher lipophilicity and a latent increased metabolic stability and Caco-2-permeability compared with their N-CH3 counterparts, illustrating the potential of the N-CF3 motif. Various N-CF3 analogues of drugs or bioactive molecules, such as sildenafil analogue, have been obtained. In general, the N-CF3 motif is developing and has great potential in bioactive molecules or materials. Give the recent development in this motif, it is foreseeable that its synthesis methods and applications will become more and more extensive. In this paper, we present an overview of the synthesis of N-CF3 heterocycles, categorized on the basis of the number of rings (three-, four-, five-, six- and larger-membered heterocycles), and focus on the five-membered heterocycles containing the N-CF3 group.

Photoinduced N-Heterocyclic Nitrenium-Catalyzed Single Electron Reduction of Acyl Fluorides for Phenanthridine Synthesis

Acyl fluorides are versatile reagents in organic synthesis. However, there is no precedent to employ acyl fluorides as acyl radical precursors. We herein report an N-heterocyclic nitrenium iodide salt-catalyzed photoreduction of acyl fluorides to produce acyl radicals, which could react with 2-isocyanobiaryls to afford various carbonyl phenanthridines.

Access to N-CF3 Formamides by Reduction of N-CF3 Carbamoyl Fluorides

The departure into unknown chemical space is essential for the discovery of new properties and function. We herein report the first synthetic access to N-trifluoromethylated formamides. The method involves the reduction of bench-stable NCF₃ carbamoyl fluorides and is characterized by operational simplicity and mildness, tolerating a broad range of functional groups as well as stereocenters. The newly made N-CF₃ formamide motif proved to be highly robust and compatible with diverse chemical transformations, underscoring its potential as building block in complex functional molecules.

Synthesis of Carbamoyl Fluorides Using a Difluorophosgene Surrogate Derived from Difluorocarbene and Pyridine N-Oxides

We report a method for the synthesis of carbamoyl fluorides from secondary amines using bench-stable, inexpensive, and readily accessible starting materials that, when combined, yield a surrogate for toxic difluorophosgene (COF₂) gas. In contrast to state-of-the-art methods for the synthesis of carbamoyl fluorides, our protocol does not require the use of pre-functionalized substrates, the preparation of light-, temperature-, and/or moisture-sensitive chemicals, or the application of explosive fluorinating reagents.

Recent Advances in C–F Bond Activation of Acyl Fluorides Directed toward Catalytic Transformation by Transition Metals, N-Heterocyclic Carbenes, or Phosphines

Numerous studies on the activation of carbon–fluorine bonds have been reported in recent years. For example, acyl fluorides have been utilized as versatile reagents for acylation, arylation, and even fluorination. In this review, we focus on acyl fluorides as compounds with carbon–fluorine bonds, and highlight recent advances in strategies for the activation of their C–F bonds via transition-metal catalysis, N-heterocyclic carbene (NHCs) catalysis, organophosphine catalysis, and classical nucleophilic substitution reactions.

1 Introduction

2 Transition-Metal-Mediated C–F Bond Activation

2.1 Acylation (Carbonyl-Retentive) Coupling Reactions

2.2 Decarbonylative Reactions

2.3 C–F Bond Activation by Other Transition Metals

3 C–F Bond Activation by N-Heterocyclic Carbenes (NHCs)

3.1 NHC-Catalyzed Cycloaddition of Acyl Fluorides

3.2 NHC-Catalyzed Radical Functionalization of Acyl Fluorides

3.3 NHC-Catalyzed Nucleophilic Fluorination of (Hetero)aromatics

4 C–F Bond Activation by Phosphines

4.1 Phosphine-Catalyzed Direct Activation of the C–F Bond of Acyl Fluorides

4.2 Phosphine-Catalyzed Indirect Activation of the C–F Bond of Acyl Fluorides

5 C–F Bond Activation by Classical Nucleophilic Substitution

6 Miscellaneous Examples

7 Summary and Perspective

Aroyl Fluorides as Bifunctional Reagents for Dearomatizing Fluoroaroylation of Benzofurans

The 2,3-dihydrobenzofuran scaffold is widely found in natural products and biologically active compounds. Herein, dearomatizing 2,3-fluoroaroylation of benzofurans with aroyl fluorides as bifunctional reagents to access 2,3-difunctionalized dihydrobenzofurans is reported. The reaction that occurs by cooperative NHC/photoredox catalysis provides 3-aroyl-2-fluoro-2,3-dihydrobenzofurans with moderate to good yield and high diastereoselectivity. Cascades proceed via radical/radical cross-coupling of a benzofuran radical cation generated in the photoredox catalysis cycle with a neutral ketyl radical formed through the NHC catalysis cycle. The redox-neutral transformation exhibits broad substrate scope and high functional group compatibility. With anhydrides as bifunctional reagents, dearomatizing aroyloxyacylation of benzofurans is achieved and the strategy can also be applied to N-acylated indoles to afford 3-aroyl-2-fluoro-dihydroindoles.

Access to Cyclic N-Trifluoromethyl Ureas through Photocatalytic Activation of Carbamoyl Azides

We report the mild activation of carbamoyl azides to the corresponding nitrenes using a blue light/[Ir]-catalyzed strategy, which enables stereospecific access to N-trifluoromethyl imidazolidinones and benzimidazolones. These novel structural motifs proved to be highly robust, allowing their downstream diversification. On the basis of our combined computational and experimental studies, we propose that an electron rebound with the excited metal catalyst is undergone, involving a reduction-triggered nitrogen loss, followed by oxidation to the corresponding carbamoyl nitrene and subsequent C-H insertion.

Synthesis of N-CF3 Amidines/Imidates/Thioimidates via N-CF3 Nitrilium Ions

An efficient methodology for the synthesis of a wide range of N-CF₃ imidic acid derivatives is presented. In this reaction, N-CF₃ nitrilium ions were generated via N-trifluoromethylation of nitriles using PhICF₃Cl under catalysis with DMAP, followed by the capture of N-, O-, or S-centered nucleophiles to give diverse N-CF₃ amidines, imidates, and thioimidates. The method provides a platform for preparing N-CF₃ compounds with potential applications.

Synthesis of N-CF3 hydrazines through radical trifluoromethylation of azodicarboxylates

We report here the synthesis of a novel family of N-CF₃ hydrazines from a direct way involving the available and cheap Langlois reagent (CF₃SO₂Na). These derivatives have shown very high stability whatever the conditions used and are excellent precursors for building previously inaccessible N-CF₃ functionalized compounds, such as substituted hydrazides, hydrazine-amino-acids, hydrazones, N-aziridines and pyrazoles.