Highly Carbon-Selective Monofluoromethylation of β-Ketoesters with Fluoromethyl Iodide

A novel 1-benzoazepine-derived Michael acceptor and its hetero-adducts active against MRSA

Multidrug-resistant bacterial infections continue to be a rising global health concern. Herein, we describe the development of a novel class of 3-substituted benzoazepinedione derivatives with promising antibacterial activity. The pivotal compound, benzoazepinedione carboxylate 9, represents a highly electrophilic Michael acceptor, enabling divergent access to a wide range of thia-, aza-, oxa-, and phospha-Michael adducts. Notably, most prepared compounds exhibited potent antibacterial activity against both drug-susceptible and drug-resistant strains of Staphylococcus aureus (MIC90 of up to 2 μg mL-1). The cytotoxicity assessment in the VERO6 cell line revealed that thia-adduct 10d (IC50 of 36.5 μg mL-1) exhibits lower toxicity compared to its parent electrophile 9 (IC50 of 14.3 μg mL-1), which is in agreement with the hypothesis of covalently modified prodrugs. Additionally, stability studies of the prepared compounds in CD3OD and a DMSO-PBS mixture confirmed that thia-Michael adducts 10 are stable under neutral conditions while dynamic under mildly basic conditions. Moreover, 3D reconstructed tissue models (human lung epithelial EpiAirway™ and a human small intestine model) did not exhibit a viability decrease below 80% of the untreated control at all concentrations tested, indicating tolerance to higher concentrations of potential drugs and prodrugs.

Harnessing dual-mode RIPK1 ligands for cross-species anti-necroptosis inhibitor compounds

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) has a crucial role in cell death and inflammation. A promising approach to develop novel inhibitors of RIPK1 mediated necroptosis is to mix the different binding modes of the known RIPK1 inhibitors into one molecule. Herein we report the synthesis and biological evaluation of novel mixed type inhibitors. Using Eclitasertib as a starting point, and applying our previous, published knowledge regarding cyclic malonamides, we successfully identified a library of active compounds. The active enantiomer of the most balanced and promising compound was subjected to pharmacokinetics and in vivo hypothermia study in mice.

Palladium-catalysed aryl/monofluoroalkylation of allenamides: access to fluoroalkyl indoles and isoquinolones

A palladium catalysed construction of fluoroalkyl indoles and isoquinolones through aryl/monofluoroalkylation of allenamides has been developed. Monofluoromethyl-substituted heterocycles could be accessed under mild conditions with broad functional group tolerance. In addition, indole-oxindole bisheterocyclic scaffolds bearing a fluorine atom were successfully synthesized with 3-fluoro-oxindole as the nucleophile by applying this method.

Palladium-catalyzed carbomonofluoromethylation of unactivated alkenes: rapid access to γ-monofluoromethyl carboxylic acid derivatives

Herein, we report a palladium-catalyzed regioselective carbomonofluoromethylation of unactivated alkenes. The reaction uses easily available fluorobis(phenylsulfonyl)methane (FBSM) as a fluoromethylating reagent, and proceeds smoothly with a wide variety of carbon electrophiles, including (hetero)aryl iodides, styrenyl iodides and TIPSBr. A range of remote γ-CH2F/CD2F carboxylic acid derivatives were constructed rapidly after a simple reductive desulfonylation step. The reaction features high regioselectivity, mild and simple reaction conditions and a broad substrate scope, and is easy to scale up.

The synthetic versatility of fluoroiodomethane: recent applications as monofluoromethylation platform

In recent years, fluoroiodomethane (CH₂FI) has emerged as an easy-to-handle, non-ozone depleting agent and readily available platform for monofluoromethylation strategies. Recent applications in nucleophilic substitutions, lithiation reactions, transition-metal catalyzed transformations, radical processes, and ¹⁸F-radiolabelling chemistry showcase the potential of this reagent for the preparation of organofluorine compounds. In this minireview, we provide an update to the field covering the recent relevant literature on the use of CH₂FI.

Diversity-Oriented Synthesis of Fluoromethylated Arenes via Palladium-Catalyzed C-H Fluoromethylation of Aryl Iodides

Herein we report the first versatile and expeditious method for the site-selective C-H fluoromethylation of aryl iodides via Pd/norbornene cooperative catalysis, which could work as a robust toolbox for the diversity-oriented synthesis (DOS) of fluoromethylated arenes. This methodology features the use of the low-cost industrial raw material CH₂IF as the fluoromethyl source, an excellent functional group tolerance, and a broad ipso termination scope and can be expanded to the late-stage modification of biorelevant molecules.

Hypervalent Iodine(III) Reagents with Transferable Primary Amines: Structure and Reactivity on the Electrophilic α-Amination of Stabilized Enolates

A new family of hypervalent iodine reagents containing transferable primary amine groups is described. Benziodoxolone-based reagents were synthesized on the gram-scale through operationally simple reactions in up to quantitative yields. These bench-stable solids were characterized by X-ray analysis and successfully employed in the α-amination of indanone-based β-ketoesters in up to 83% yield. Mechanistic studies indicate a substitution mechanism involving an electrophilic amine.

Fluorinated S-Adenosylmethionine as a Reagent for Enzyme-Catalyzed Fluoromethylation

Strategic replacement of protons with fluorine atoms or functional groups with fluorine-containing fragments has proven a powerful strategy to optimize the activity of therapeutic compounds. For this reason, the synthetic chemistry of organofluorides has been the subject of intense development and innovation for many years. By comparison, the literature on fluorine biocatalysis still makes for a slim chapter. Herein we introduce S-adenosylmethionine (SAM) dependent methyltransferases as a new tool for the production of fluorinated compounds. We demonstrate the ability of halide methyltransferases to form fluorinated SAM (S-adenosyl-S-(fluoromethyl)-L-homocysteine) from S-adenosylhomocysteine and fluoromethyliodide. Fluorinated SAM (F-SAM) is too unstable for isolation, but is accepted as a substrate by C-, N- and O-specific methyltransferases for enzyme-catalyzed fluoromethylation of small molecules.

Nickel-catalyzed reductive monofluoroakylation of alkyl tosylate with bromofluoromethane to primary alkyl fluoride

A nickel-catalysed direct terminal monofluoromethlyation between alkyl tosylates and a low-cost, industrial raw material bromofluoromethane has been developed. This transformation has demonstrated high efficiency, mild conditions, and good functional-group compatibility. The key to success of this transformation lies in the ligand and mild base selection, ensuring the generation of various terminal monofluormethylation products.

Asymmetric α-electrophilic difluoromethylation of β-keto esters by phase transfer catalysis

An efficient and enantioselective α-electrophilic difluoromethylation of β-keto esters has been achieved by phase-transfer catalysis. This procedure is applicable to different kinds of β-keto esters with a series of cinchona-derived C-2' aryl-substituted phase-transfer catalysts. The reaction gives the corresponding products in good enantioselectivities (up to 83% ee) and yields (up to 92%) with high C/O regioselectivities (up to 98 : 2). Moreover, the C/O selectivity of β-keto esters could be easily reversed and controlled. This asymmetric difluoromethylation provided a novel and efficient way for introducing chiral C-CF2H groups.

Fluoromethyl-2,4,6-trinitrophenylsulfonate: A New Electrophilic Monofluoromethylating Reagent

Fluoromethyl-2,4,6-trinitrophenylsulfonate has been prepared for the first time and qualified as a simple to use monofluoromethylating reagent. Its molecular structure in the solid state has been determined by single-crystal X-ray diffraction studies. This reagent proves to be effective for the electrophilic introduction of a CH₂F group into selected chalcogen and nitrogen nucleophiles. Monofluoromethyl derivatives of various bifunctional N,O-nucleophiles have been synthesized using fluoromethyl-2,4,6-trinitrophenylsulfonate. Due to the good crystallizing properties of the anion, the fluoromethylated products as well as side products that are difficult to identify by nuclear magnetic resonance spectroscopy can readily be characterized by X-ray crystallographic techniques.

Reagents for Selective Fluoromethylation: A Challenge in Organofluorine Chemistry

The introduction of a monofluoromethyl moiety has undoubtedly become a very important area of research in recent years. Owing to the beneficial properties of organofluorine compounds, such as their metabolic stability, the incorporation of the CH2 F group as a bioisosteric substitute for various functional groups is an attractive strategy for the discovery of new pharmaceuticals. Furthermore, the monofluoromethyl unit is also widely used in agrochemistry, in pharmaceutical chemistry, and in fine chemicals. The problems associated with climate change and the growing need for environmentally friendly industrial processes mean that alternatives to the frequently used CFC and HFBC fluoromethylating agents (CH2 FCl and CH2 FBr) are urgently needed and also required by the Montreal Protocol. This has recently prompted many researchers to develop alternative fluoromethylation agents. This Minireview summarizes both the classical and new generation of fluoromethylating agents. Reagents that act via electrophilic, nucleophilic, and radical pathways are discussed, in addition to their precursors.

Direct and Chemoselective Electrophilic Monofluoromethylation of Heteroatoms (O-, S-, N-, P-, Se-) with Fluoroiodomethane

The commercially available fluoroiodomethane represents a valuable and effective electrophilic source for transferring the CH₂F unit to a series of heteroatom-centered nucleophiles under mild basic conditions. The excellent manipulability offered by its liquid physical state (bp 53.4 °C) enables practical and straightforward one-step nucleophilic substitutions to retain the chiral information embodied, thus allowing it to overcome de facto the requirement for fluoromethylating agents with no immediate access. The high-yielding methodology was successfully applied to a variety of nucleophiles including a series of drugs currently in the market.

Fluoromethoxymethylation of Nitrogen Heterocyclic Compounds with Fluoromethyl Iodide

The fluoromethoxymethylation of nitrogen heterocyclic compounds with fluoromethyl iodide has been reported for the first time. In this reaction, a number of unexplored fluoromethoxymethylated nitrogen heterocyclic compounds including indoles, carbazoles, and 1H-indazoles were efficiently formed. Mechanistic studies indicated that this transformation consists of electrophilic monofluoromethylation, rapid hydrolysis, and another electrophilic monofluoromethylation. This method makes it possible to synthesize complex bioactive molecules containing a CH₂OCH₂F group, which have the potential to be a new series of fluorine-containing chemical entities for medicinal chemists.