Palladium-Catalyzed Electrooxidative Hydrofluorination of Aryl-Substituted Alkenes with a Nucleophilic Fluorine Source

Electrochemical Decarboxylative Cross-Coupling with Nucleophiles

Decarboxylative cross-coupling reactions are powerful tools for carbon-heteroatom bonds formation, but typically require pre-activated carboxylic acids as substrates or heteroelectrophiles as functional groups. Herein, we present an electrochemical decarboxylative cross-coupling of carboxylic acids with structurally diverse fluorine, alcohol, H2O, acid, and amine as nucleophiles. This strategy takes advantage of the ready availability of these building blocks from commercial libraries, as well as the mild and oxidant-free conditions provided by electrochemical system. This reaction demonstrates good functional-group tolerance and its utility in late-stage functionalization.

Photoinduced Transition-Metal and External Photosensitizer Free Benzylic Fluorination of Unactivated Alkylarenes

A green and efficient protocol for the direct monofluorination of unactivated alkylarenes under visible-light irradiation has been developed, without any extraneous transition-metal catalysts or photosensitizers. This method is compatible with a broad spectrum of functional groups, including carboxylic and alcoholic scaffolds, under mild reaction conditions. Gram-scale synthesis of a fluorine-containing pharmaceutical analogue was successfully executed, underscoring the strategy's reliability and practicality. Furthermore, mechanistic studies suggest that a single-electron transfer mechanism might be responsible for the generation of the benzylic radicals in initiation step.

Silver-Catalyzed Carbofluorination of Olefins and α-Fluoroolefins with Carbamoyl Radicals

The reactivity of carbamoyl radicals, generated in situ from sodium oxamate salts, has been investigated in the context of radical carbofluorination reactions of olefins and α-fluoroolefins, respectively. Both transformations are catalyzed by silver salts and required the presence of potassium persulfate (K2S2O8) and SelectfluorTM as a radicophilic fluorine source. The reported methods provide a direct access to β-fluoroamides and β,β-difluoroamides.

Nickel-Catalyzed Hydrofluorination in Unactivated Alkenes: Regio- and Enantioselective C-F Bond Formation

Catalytic formation of a regio- and enantioselective C-F bond chiral center from readily available alkenes is a crucial goal, yet it continues to pose significant challenges in organic synthesis. Here, we report the regioselective formation of C-F bonds facilitated by NiH catalysis and a coordination directing strategy that enables precise hydrofluorination of both terminal and internal alkenes. Notably, we have optimized this methodology to achieve high enantioselectivity in creating aliphatic C-F stereogenic centers especially with β,γ-alkenyl substrates, using a tailored chiral Bn-BOx ligand. Another pivotal finding in our research is the identification of the (+)-nonlinear effect under optimized conditions, allowing for high enantioselectivity even with moderately enantiomerically enriched chiral ligands. Given the significant role of fluorine in pharmaceuticals and synthetic materials, this research offers essential insights into the regioselective and enantioselective formation of C-F bond chiral centers, paving the way for the efficient production of valuable fluorinated compounds.

Co-Catalyzed Hydrofluorination of Alkenes: Photocatalytic Method Development and Electroanalytical Mechanistic Investigation

The hydrofluorination of alkenes represents an attractive strategy for the synthesis of aliphatic fluorides. This approach provides a direct means to form C(sp3)-F bonds selectively from readily available alkenes. Nonetheless, conducting hydrofluorination using nucleophilic fluorine sources poses significant challenges due to the low acidity and high toxicity associated with HF and the poor nucleophilicity of fluoride. In this study, we present a new Co(salen)-catalyzed hydrofluorination of simple alkenes utilizing Et3N·3HF as the sole source of both hydrogen and fluorine. This process operates via a photoredox-mediated polar-radical-polar crossover mechanism. We also demonstrated the versatility of this method by effectively converting a diverse array of simple and activated alkenes with varying degrees of substitution into hydrofluorinated products. Furthermore, we successfully applied this methodology to 18F-hydrofluorination reactions, enabling the introduction of 18F into potential radiopharmaceuticals. Our mechanistic investigations, conducted using rotating disk electrode voltammetry and DFT calculations, unveiled the involvement of both carbocation and CoIV-alkyl species as viable intermediates during the fluorination step, and the contribution of each pathway depends on the structure of the starting alkene.

Electrochemical Late-Stage Functionalization

Late-stage functionalization (LSF) constitutes a powerful strategy for the assembly or diversification of novel molecular entities with improved physicochemical or biological activities. LSF can thus greatly accelerate the development of medicinally relevant compounds, crop protecting agents, and functional materials. Electrochemical molecular synthesis has emerged as an environmentally friendly platform for the transformation of organic compounds. Over the past decade, electrochemical late-stage functionalization (eLSF) has gained major momentum, which is summarized herein up to February 2023.

Highlights on U.S. FDA-approved fluorinated drugs over the past five years (2018-2022)

The objective of this review is to provide an update on the fluorine-containing drugs approved by U.S. Food and Drug Administration in the span of past five years (2018-2022). The agency accepted a total of fifty-eight fluorinated entities to diagnose, mitigate and treat a plethora of diseases. Among them, thirty drugs are for therapy of various types of cancers, twelve for infectious diseases, eleven for CNS disorders, and six for some other diseases. These are categorized and briefly discussed based on their therapeutic areas. In addition, this review gives a glimpse about their trade name, date of approval, active ingredients, company developers, indications, and drug mechanisms. We anticipate that this review may inspire the drug discovery and medicinal chemistry community in both industrial and academic settings to explore the fluorinated molecules leading to the discovery of new drugs in the near future.