Efficient Synthesis of Trifluoromethyl Amines through a Formal Umpolung Strategy from the Bench‐Stable Precursor (Me 4 N)SCF 3

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.

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.

Metal-Free SF6 Activation: A New SF5 -Based Reagent Enables Deoxyfluorination and Pentafluorosulfanylation Reactions

The activation of SF₆ , a potent greenhouse gas, under metal-free and visible light conditions is reported. Herein, mechanistic investigations including EPR spectroscopy, NMR studies and cyclic voltammetry allowed the rational design of a new fluorinating reagent which was synthesized from the 2-electron activation of SF₆ with commercially available TDAE. This new SF₅ -based reagent was efficiently employed for the deoxyfluorination of CO₂ and the fluorinative desulfurization of CS₂ allowing the formation of useful fluorinated amines. Moreover, for the first time we demonstrated that our SF₅ -based reagent could afford the mild generation of Cl-SF₅ gas. This finding was exploited for the chloro-pentafluorosulfanylation of alkynes and alkenes.

Stable and Storable N(CF3 )2 Transfer Reagents

Fluorinated groups are essential for drug design, agrochemicals, and materials science. The bis(trifluoromethyl)amino group is an example of a stable group that has a high potential. While the number of molecules containing perfluoroalkyl, perfluoroalkoxy, and other fluorinated groups is steadily increasing, examples with the N(CF₃ )₂ group are rare. One reason is that transfer reagents are scarce and metal-based storable reagents are unknown. Herein, a set of Cu^I and Ag^I bis(trifluoromethyl)amido complexes stabilized by N- and P-donor ligands with unprecedented stability are presented. The complexes are stable solids that can even be manipulated in air for a short time. They are bis(trifluoromethyl)amination reagents as shown by nucleophilic substitution and Sandmeyer reactions. In addition to a series of benzylbis(trifluoromethyl)amines, 2-bis(trifluoromethyl)amino acetate was obtained, which, upon hydrolysis, gives the fluorinated amino acid N,N-bis(trifluoromethyl)glycine.

N-Trifluoromethyl Hydrazines, Indoles and Their Derivatives

Reported herein is the first efficient strategy to synthesize a broad range of unsymmetrical N-CF₃ hydrazines, which served as platform to unlock numerous currently inaccessible derivatives, such as tri- and tetra-substituted N-CF₃ hydrazines, hydrazones, sulfonyl hydrazines, and valuable N-CF₃ indoles. These compounds proved to be remarkably robust, being compatible with acids, bases, and a wide range of synthetic manipulations. The feasibility of RN(CF₃ )-NH₂ to function as a directing group in C-H functionalization is also showcased.

Facile Access to AgOCF3 and Its New Applications as a Reservoir for OCF2 for the Direct Synthesis of N-CF3 , Aryl or Alkyl Carbamoyl Fluorides

The development of innovative fluorination strategies is greatly dependent also on the availability, safety and practicability of available fluorinating reagents. We herein show a straightforward and quantitative strategy for the preparation of valuable AgOCF₃ at room temperature and showcase its performance in trifluoromethoxylations or as reservoir for O=CF₂ . This enabled the direct, practical and safe synthesis of valuable N-alkyl/aryl and N-CF₃ carbamoyl fluorides from secondary amines and isothiocyanides, respectively. Our mechanistic data indicate that AgOCF₃ does not liberate O=CF₂ until it is activated by a nucleophilic co-reagent, reinforcing the stability of the salt under our new preparation strategy.

A Convenient Synthesis of Difluoroalkyl Ethers from Thionoesters Using Silver(I) Fluoride

Herein we report the mild and rapid fluorodesulfurization of thionoesters using only silver(I) fluoride. This reaction demonstrates excellent functional group tolerance and complements existing strategies for difluoroalkyl ether synthesis, which rely on toxic and often dangerous reagents that demonstrate limited functional group compatibility. We additionally report the translation of this finding to the production of ¹⁸ F-labelled difluoroalkyl ethers using fluoride-derived [¹⁸ F]AgF. This new process should enable the synthesis of a wide range of difluoroalkyl ethers with applications in medicinal and materials chemistry, and radiotracer production.

Reaction of Thiocarbonyl Fluoride Generated from Difluorocarbene with Amines

The reaction of thiocarbonyl fluoride, generated from difluorocarbene, with various amines under mild conditions is described. Secondary amines, primary amines, and o-phenylenediamines are converted to thiocarbamoyl fluorides, isothiocyanates, and difluoromethylthiolated heterocycles, respectively. Thiocarbamoyl fluorides were further transformed into trifluoromethylated amines by using a one-pot process. Thiocarbonyl fluoride is generated in situ and is rapidly fully converted in one pot under mild conditions; therefore, no special safety precautions are needed.

Palladium-Catalyzed 2,2,2-Trifluoroethoxylation of Aromatic and Heteroaromatic Chlorides Utilizing Borate Salt and the Synthesis of a Trifluoro Analogue of Sildenafil

A simple and convenient method was developed for the introduction of a 2,2,2-trifluoroethoxy group to various aromatic and heteroaromatic systems. The novel process utilizes aromatic chlorides as substrates, and tetrakis(2,2,2-trifluoroethoxy) borate salt as an inexpensive and readily available fluoroalkoxy source in a palladium-catalyzed cross-coupling reaction. The power of the developed methodology was demonstrated in the synthesis of a fluorous derivative of Sildenafil.