Recent advances in the synthesis of fluoroalkylated compounds using fluoroalkyl anhydrides

Visible-light organophotoredox-catalyzed fluoroalkyl aminoxylation of unactivated and activated alkenes

An efficient method for the regioselective tetra-, tri-, di- and per-fluoroalkyl aminoxylation of unactivated and activated alkenes has been achieved with various fluorinated alkyl halides and OH-hydroxylamines. This developed photoredox-neutral protocol features versatile transformations to novel tetrafluoroethylene-containing compounds.

B12-Dependent Radical SAM Enzymes Catalyze C-Fluoromethylation via a CH2F-Cobalamin Intermediate

Fluorine and fluorine-containing functional groups play important roles in drugs and agrochemicals. Recently, SAM-dependent methyltransferases and several SAM analogues have been reported for fluoromethyl transfer through a nucleophilic mechanism. However, fluoromethylation of unactivated carbon centers is very challenging, and their substitution usually involves a radical mechanism. To date, no biocatalysts have been developed for fluoromethylation of unactivated carbon centers. In this study, we found that the B12-dependent radical SAM methyltransferase (B12-RSMT) QCMT can fluoromethylate the glutamine Cα position of peptides with fluorinated SAM (F-SAM) generated in situ by the enzyme AclHMT. QCMT can cleave F-SAM to produce the 5'-dA radical. The significant reaction intermediate CH2FCbI was characterized by HR-MS, 19F NMR spectroscopy and X-ray crystallography. In addition, B12-RSMTs CysS and GenD1 can also transfer fluoromethyl groups onto natural products. We also found that F-SAM is not compulsory. The reduced B12-RSMTs can directly generate CH2FCbI with CH2FI and transfer the CH2F group when SAM is used as the radical initiator. Our results demonstrate a radical-mediated enzymatic strategy for fluoromethylation with abiological cofactors and expand radical SAM enzymes to the field of fluorine chemistry.

A review of the synthetic strategies toward the antiviral drug tecovirimat

This review provides a comprehensive analysis of synthetic routes for tecovirimat, an antiviral drug used to treat orthopoxvirus infections, including monkeypox and smallpox. We focus on the scale-up synthesis of key intermediates, including cycloheptatriene, as documented in the published literature and patent records. The review highlights the efficiency, yield, and purity of these approaches, as well as the minimization of genotoxic and in-process impurities. Furthermore, we critically evaluate the recently reported optimized industrial-scale synthesis process, highlighting its advantages and limitations, and identifying avenues for further improvement. By obtaining insights from the published literature and patent records, this review elucidates the current state of knowledge regarding key synthesis parameters influencing tecovirimat production and emphasizes the critical importance of optimizing synthesis techniques to achieve remarkable improvements in safety and environmental impact. This review serves as a valuable resource for researchers and industry professionals in the field of R&D and production of APIs, particularly in expediting the safe and efficient industrial production of tecovirimat.

Photoinduced fluoroalkylation-peroxidation of alkenes enabled by ligand-to-iron charge transfer mediated decarboxylation

We report here a photoinduced iron-catalyzed fluoroalkylation-peroxidation of activated and/or unactivated alkenes with fluoroalkyl carboxylic acids and hydroperoxide. The ligand-to-iron charge transfer strategy effectively overcomes the high redox potential of the fluoroalkyl carboxylic acids, facilitating the difunctionalization reaction to occur smoothly under mild reaction conditions. The late-stage functionalization of drug and natural product derivatives was also demonstrated.

Cu0-Promoted Truce-Smiles Rearrangement for Aryl-Difluoromethylenation of C═C Bonds via a Reductive Radical-Polar Crossover Process

An efficient Cu0-promoted Truce-Smiles rearrangement for the aryl-difluoromethylenation of C═C bonds by the reaction of N-alkyl-N-(arylsulfonyl)methacrylamide and 2-bromodifluoromethyl-1,3-benzodiazole via a reductive radical-polar crossover process under mild reaction conditions is presented. The protocol enables practical access to a variety of single regioisomer α-aryl-β-difluoromethylene amides in good to excellent yields through consecutive difluoromethylenation, radical-polar crossover, 1,4-aryl migration, SO2 extrusion, and N-H bond formation cascade reaction.

Copper-Catalyzed Oxidative Synthesis of 3-Aryl-5-fluoroalkyl-1,3,4-oxadiazol-2(3H)-ones Using Perfluorocarboxylic Anhydride as a Reagent

A copper-catalyzed oxidative annulation of sydnones with perfluorocarboxylic anhydride for the synthesis of 3-aryl-5-fluoroalkyl-1,3,4-oxadiazol-2(3H)-ones is developed. A diverse array of 3-aryl-5-fluoroalkyl-1,3,4-oxadiazol-2(3H)-ones are prepared with good yields (>73 examples, yields up to 95%). The synthetic utility of the developed protocol was demonstrated by gram-scale synthesis, and the synthetic transformation to 1,2,4-triazol-3-one products. A mechanistic study suggests that the reaction proceeds via the extrusion of carbon dioxide to generate the hydrazide intermediate, which then undergoes intramolecular cyclization and oxidation.

Iron photocatalysis via Brønsted acid-unlocked ligand-to-metal charge transfer

Reforming sustainable 3d-metal-based visible light catalytic platforms for inert bulk chemical activation is highly desirable. Herein, we demonstrate the use of a Brønsted acid to unlock robust and practical iron ligand-to-metal charge transfer (LMCT) photocatalysis for the activation of multifarious inert haloalkylcarboxylates (CnXmCOO-, X = F or Cl) to produce CnXm radicals. This process enables the fluoro-polyhaloalkylation of non-activated alkenes by combining easily available Selectfluor as a fluorine source. Valuable alkyl fluorides including potential drug molecules can be easily obtained through this protocol. Mechanistic studies indicate that the real light-harvesting species may derive from the in situ-assembly of Fe3+, CnXmCOO-, H+, and acetonitrile solvent, in which the Brønsted acid indeed increases the efficiency of LMCT between the iron center and CnXmCOO- via hydrogen-bond interactions. We anticipate that this Brønsted acid-unlocked iron LMCT platform would be an intriguing sustainable option to execute the activation of inert compounds.

Copper Loading-Controlled Selective Synthesis of 2,5-Bis(trifluoromethyl) and Monotrifluoromethyl-Substituted Oxazoles

A general domino annulation reaction of sulfonylmethyl isocyanide with trifluoroacetic anhydride in the presence of copper chloride as an additive is developed. The reaction affords 2,5-bis(trifluoromethyl)oxazoles in modest to good yields under mild conditions. A wide variety of sulfonylmethyl isocyanide and perfluorocarboxylic anhydride substrates are amenable to this transformation. Under a higher copper salt loading conditions, the reaction led to the formation of monotrifluoromethyl-substituted oxazole product.

Recent advances in ligand-enabled palladium-catalyzed divergent synthesis

Developing efficient and straightforward strategies to rapidly construct structurally distinct and diverse organic molecules is one of the most fundamental tasks in organic synthesis, drug discovery and materials science. In recent years, divergent synthesis of organic functional molecules from the same starting materials has attracted significant attention and has been recognized as an efficient and powerful strategy. To achieve this objective, the proper adjustment of reaction conditions, such as catalysts, solvents, ligands, etc., is required. In this review, we summarized the recent efforts in chemo-, regio- and stereodivergent reactions involving acyclic and cyclic systems catalyzed by palladium complexes. Meanwhile, the reaction types, including carbonylative reactions, coupling reactions and cycloaddition reactions, as well as the probable mechanism have also been highlighted in detail.

Recent advances on non-precious metal-catalysed fluorination, difluoromethylation, trifluoromethylation, and perfluoroalkylation of N-heteroarenes

This review highlights the recent advances, from 2015 to 2023, on the introduction of organo-fluorine derivatives at the N-heteroarene core. Notable features considering new technologies based on organofluorine compounds such as: (i) approaches based on non-precious metal catalysis (Fe, Co, Mn, Ni, etc.), (ii) the development of new strategies using non-precious metal-catalysts for the introduction of organo-fluorinine derivatives using N-heterocycles with one or more heteroatoms, (iii) newer reagents for fluorination, difluoromethylation, trifluoromethylation, or perfluoroalkylation of N-heteroarenes using different approaches, (iv) mechanistic studies on various catalytic transformations, as and when required, and (v) the synthetic applications of various bio-active organo-fluorine compounds, including post-synthetic drug derivatization, are discussed.

Access to Trifluoromethylketones from Alkyl Bromides and Trifluoroacetic Anhydride by Photocatalysis

Aliphatic trifluoromethyl ketones are a type of unique fluorine-containing subunit which play a significant role in altering the physical and biological properties of molecules. Catalytic methods to provide direct access to aliphatic trifluoromethyl ketones are highly desirable yet remain underdeveloped, partially owing to the high reactivity and instability of trifluoroacetyl radical. Herein, we report a photocatalytic synthesis of trifluoromethyl ketones from alkyl bromides with trifluoroacetic anhydride. The reaction features dual visible-light and halogen-atom-transfer catalysis, followed by an enabling radical-radical cross-coupling of an alkyl radical with a stabilized trifluoromethyl radical. The reaction provides straightforward access to aliphatic trifluoromethyl ketones from readily available and cost-effective alkyl halides and trifluoroacetic anhydride (TFAA).

Understanding and Controlling Fluorinated Diacyl Peroxides and Fluoroalkyl Radicals in Alkene Fluoroalkylations

The demand for practical methods for the synthesis of novel fluoroalkyl molecules is increasing owing to their diverse applications. Our group has achieved efficient difunctionalizing fluoroalkylations of alkenes using fluorinated carboxylic anhydrides as user-friendly fluoroalkyl sources. Fluorinated diacyl peroxide, prepared in situ from carboxylic anhydrides, enables the development of novel reactions when used as a radical fluoroalkylating reagent. In this account, we aim to provide an in-depth understanding of the structure, bonding, and reactivity of fluorinated diacyl peroxides and radicals as well as their control in fluoroalkylation reactions. In the first part of this account, the physical properties and reactivity of diacyl peroxides and fluoroalkyl radicals are described. In the subsequent part, we categorize the reactions into copper-catalyzed and metal-free methods utilizing the oxidizing properties of fluorinated diacyl peroxides. We also outline examples and mechanisms.

Photoredox Activation of Anhydrides for the Solvent-Controlled Switchable Synthesis of gem-Difluoro Compounds

The incorporation of the gem-difluoromethylene (CF2 ) group into organic frameworks is highly sought due to the influence of this unit on the physicochemical and pharmacological properties of molecules. Herein we report an operationally simple, mild, and switchable protocol to access various gem-difluoro compounds that employs chlorodifloroacetic anhydride (CDFAA) as a low-cost and versatile fluoroalkylating reagent. Detailed mechanistic studies revealed that electron-transfer photocatalysis triggers mesolytic cleavage of a C-Cl bond generating a gem-difluoroalkyl radical. In the presence of alkene, this radical species acts as a unique intermediate that, under solvent-controlled reaction conditions, delivers a wide range of gem-difluorinated γ-lactams, γ-lactones, and promotes oxy-perfluoroalkylation. These protocols are flow- and batch-scalable, possess excellent chemo- and regioselectivity, and can be used for the late-stage diversification of complex molecules.

Regioselective Synthesis of 5-Trifluoromethyl 1,2,4-Triazoles via [3 + 2]-Cycloaddition of Nitrile Imines with CF3CN

We herein describe a general approach to 5-trifluoromethyl 1,2,4-triazoles via the [3 + 2]-cycloaddition of nitrile imines generated in situ from hydrazonyl chloride with CF₃CN, utilizing 2,2,2-trifluoroacetaldehyde O-(aryl)oxime as the precursor of trifluoroacetonitrile. Various functional groups, including alkyl-substituted hydrazonyl chloride, were tolerated during cycloaddition. Furthermore, the gram-scale synthesis and common downstream transformations proved the potential synthetic relevance of this developed methodology.