Fluorine-containing drugs approved by the FDA in 2019

Synthesis of Sterically Hindered Dialkyl Ethers via Palladium-Catalyzed Fluoro-alkoxylation of gem-Difluoroalkenes

Organofluorine compounds are of high value in medicinal and agricultural chemistry. Herein, we report a palladium-catalyzed fluoro-alkoxylation of gem-difluoroalkenes for the synthesis of much more challenging sterically hindered ethers. This reaction represents a direct synthesis method for α-trifluoromethyl ethers with a broad functional group tolerance and excellent regioselectivity. This system employs N-fluorobenzenesulfonimide (NFSI) as an electrophilic fluorine source and alcohols as nucleophilic donors, including but not limited to sterically hindered tert-substituted alcohols.

Phosphine-Catalyzed Domino Annulation of γ-Vinyl Allenoates: Synthesis of Tetrahydrofuro[3,2-c]quinoline Derivatives

A novel phosphine-catalyzed domino annulation reaction of γ-vinyl allenoates and o-aminotrifluoacetophenones for the construction of terahydrofuro[3,2-c]quinoline derivatives has been developed. In this domino reaction, two kinds of terahydrofuro[3,2-c]quinoline compounds containing CF3 groups were obtained with good yields under mild conditions, three new C-N, C-C, and C-O bonds can be built in one step, and the reaction selectivity is achieved by adjusting the reaction conditions. Furthermore, preliminary studies on an asymmetric variant of this reaction proceeded with moderate enantioselectivity.

Visible Light-Induced 1,2-Diphenyldisulfane-Mediated Defluoroborylation of Polyfluoroarenes

A green and practical protocol of defluoroborylation of polyfluoroarenes with stable and readily accessible NHC-borane was developed, using 1,2-diphenyldisulfane as a hydrogen atom transfer (HAT) and single electron transfer (SET) reagent precursor under visible-light irradiation, leading to the concise formation of value-added fluorinated organoboron scaffolds. Mechanism studies revealed the method underwent a boryl radical addition reaction with polyfluoroarene, followed by successive single electron transfer pathways and defluorination of the C-F bond to offer the targeted product. This unprecedented platform relies on 1,2-diphenyldisulfane and base without using expensive photocatalysts, highlighting the methodology has promising application value to prepare borylated polyfluoroarene compounds.

A SmI2-mediated reductive cyclisation reaction using the trifluoroacetamide group as the radical precursor

A samarium(II)-mediated reductive cyclisation reaction with the aminoketyl radical from the trifluoroacetamide group for synthesising 2-trifluoromethylindolines was developed. This reaction is the first example of using an acyclic amide group, which is considered difficult to react with SmI2, in a reductive cyclisation. Additionally, the conversion of the obtained product into 2-trifluoromethylindole was achieved.

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

An efficient multicomponent reaction of newly designed β-trifluoromethyl β-diazo esters, acetonitrile, and carboxylic acids via an interrupted esterification process under copper-catalyzed conditions has been developed, which affords various unsymmetrical β-trifluoromethyl N,N-diacyl-β-amino esters in good to excellent yields. The reaction features mild conditions, a wide scope of β-amino esters and carboxylic acids, and also applicability to large-scale synthesis, thus providing an efficient way for the synthesis of β-trifluoromethyl β-diacylamino esters. Furthermore, this reaction represents the first example of a Mumm rearrangement of β-trifluoromethyl β-diazo esters.

Latest developments in coumarin-based anticancer agents: mechanism of action and structure-activity relationship studies

Many researchers around the world are working on the development of novel anticancer drugs with different mechanisms of action. In this case, coumarin is a highly promising pharmacophore for the development of novel anticancer drugs. Besides, the hybridization of this moiety with other anticancer pharmacophores has emerged as a potent breakthrough in the treatment of cancer to decrease its side effects and increase its efficiency. This review aims to provide a comprehensive overview of the recent development of coumarin derivatives and their application as novel anticancer drugs. Herein, we highlight and describe the largest number of research works reported in this field from 2015 to August 2023, along with their mechanisms of action and structure-activity relationship studies, making this review different from the other review articles published on this topic to date.

Thermoinduced Radical Cyclization for the Synthesis of Sultines

A thermoinduced radical homolytic substitution cyclization of alkenyl tethered sulfinate esters was displayed under mild metal-free conditions, enabling the functionalization of alkenes and leading to structurally diverse value-added sultine products. The process utilizes readily available substrates using inexpensive 5% benzoyl peroxide (BPO) as an initiator to generate functionalized sultines with broad functional group tolerance in medium to excellent yields in a highly atom-economical manner. In addition, the obtained sultines could be further readily functionalized toward valuable sultone frameworks in one pot. A thermo-catalytic radical chain process was proposed based on mechanistic studies.

Nickel-Catalyzed Aminofluoroalkylative Cyclization of Styrenes with Ethyl Fluoroacetate and Anilines toward Fluoro-γ-Lactams

A novel method for the nickel-catalyzed multicomponent aminofluoroalkylation/cyclization of styrenes with ethyl fluoroacetate and anilines has been developed. This protocol provides general and efficient access to a diverse range of fluoro-γ-lactams from simple and readily available starting materials. Control experiments prove the involvement of radical intermediates and excluded the presence of 2-fluoro-N-phenylacetamide.

A review: FDA-approved fluorine-containing small molecules from 2015 to 2022

Fluorine-containing small molecules have occupied a special position in drug discovery research. The successful clinical use of fluorinated corticosteroids in the 1950s and fluoroquinolones in the 1980s led to an ever-increasing number of approved fluorinated compounds over the last 50 years. They have shown various biological properties such as antitumor, antimicrobial, and anti-inflammatory activities. Fluoro-pharmaceuticals have been considered a strong and practical tool in the rational drug design approach due to their benefits from potency and ADME (absorption, distribution, metabolism, and excretion) points of view. Herein, approved fluorinated drugs from 2015 to 2022 were reviewed.

Synthesis of Alkylated Polyfluorobenzenes through Decarboxylative Giese Addition of Aliphatic N-Hydroxyphthalimide Esters with Polyfluorostyrene

Polyfluoroaromatic compounds play crucial roles in medicinal and material science. However, the synthesis of alkylated polyfluoroarenes has been relatively underdeveloped. In this study, we devised a novel decarboxylative coupling reaction between aliphatic N-hydroxyphthalimide esters and polyfluorostyrene, leveraging the photochemical activity of electron donor-acceptor (EDA) complexes. This method offers simple reaction conditions, a broad substrate scope, and excellent functional group tolerance. Furthermore, we have demonstrated the practicality of this protocol through late-stage polyfluoroaryl modification of biologically active molecules using readily available carboxylic acids as starting materials, thus providing an important supplement to the current toolbox for accessing alkylated polyfluoroaryl motifs.

Cascade Detrifluoroacetylation, C-S Bond Cleavage, and SN2' Reaction of α,α-Difluorinated Gem-Diols with MBH Esters

A new SN2' reaction type of Morita-Baylis-Hillman (MBH) ester with sulfonyl anion, generated in situ via detrifluoroacetylation as a nucleophile is developed. Experimental results and DFT calculations disclose that the reaction proceeds via C-C bond cleavage to generate a PhSO2CF2 anion, C-S bond cleavage to generate a sulfonyl anion with the release of CF2 carbene, and an SN2' reaction with the MBH ester. The reaction features operational simplicity, wide substrate scope, high yields, and excellent stereoselectivity, which represents a new reaction mode of fluorinated gem-diols and also provides an efficient way to obtain β,γ-unsaturated sulfones.

Mono- and Difluorinated Saturated Heterocyclic Amines for Drug Discovery: Systematic Study of Their Physicochemical Properties

A comprehensive study of physicochemical properties (pKa , LogP, and intrinsic microsomal clearance) within the series of mono- and difluorinated azetidine, pyrrolidine, and piperidine derivatives was performed. While the number of fluorine atoms and their distance to the protonation center were the major factors defining the compound's basicity, both pKa and LogP values were affected considerably by the conformational preferences of the corresponding derivatives. For example, features of "Janus face" (facially polarized) cyclic compounds (i. e., unusually high hydrophilicity) were identified for cis-3,5-difluoropiperidine, preferring a diaxial conformation. Intrinsic microsomal clearance measurements demonstrated high metabolic stability of the compounds studied (with a single exception of the 3,3-difluoroazetidine derivative). According to pKa - LogP plots, the title compounds provide a valuable extension of the fluorine-containing (e. g., fluoroalkyl-substituted) saturated heterocyclic amine series as building blocks for rational optimization studies in early drug discovery.

Chemistry and Pharmacology of Fluorinated Drugs Approved by the FDA (2016-2022)

Fluorine is characterized by high electronegativity and small atomic size, which provide this molecule with the unique property of augmenting the potency, selectivity, metabolic stability, and pharmacokinetics of drugs. Fluorine (F) substitution has been extensively explored in drug research as a means of improving biological activity and enhancing chemical or metabolic stability. Selective F substitution onto a therapeutic or diagnostic drug candidate can enhance several pharmacokinetic and physicochemical properties such as metabolic stability and membrane permeation. The increased binding ability of fluorinated drug target proteins has also been reported in some cases. An emerging line of research on F substitution has been addressed by using 18F as a radiolabel tracer atom in the extremely sensitive methodology of positron emission tomography (PET) imaging. This review aims to report on the fluorinated drugs approved by the US Food and Drug Administration (FDA) from 2016 to 2022. It cites selected examples from a variety of therapeutic and diagnostic drugs. FDA-approved drugs in this period have a variety of heterocyclic cores, including pyrrole, pyrazole, imidazole, triazole, pyridine, pyridone, pyridazine, pyrazine, pyrimidine, triazine, purine, indole, benzimidazole, isoquinoline, and quinoline appended with either F-18 or F-19. Some fluorinated oligonucleotides were also authorized by the FDA between 2019 and 2022.

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.

Synthesis of Aminoalkyl Sclareolide Derivatives and Antifungal Activity Studies

Sclareolide was developed as an efficient C-nucleophilic reagent for an asymmetric Mannich addition reaction with a series of N-tert-butylsulfinyl aldimines. The Mannich reaction was carried out under mild conditions, affording the corresponding aminoalkyl sclareolide derivatives with up to 98% yield and 98:2:0:0 diastereoselectivity. Furthermore, the reaction could be performed on a gram scale without any reduction in yield and diastereoselectivity. Additionally, deprotection of the obtained Mannich addition products to give the target sclareolide derivatives bearing a free N-H group was demonstrated. In addition, target compounds 4-6 were subjected to an antifungal assay in vitro, which showed considerable antifungal activity against forest pathogenic fungi.

Enantioselective Cu-Catalyzed Nucleophilic Substitutions of Polyfluoroarenes: Synthesis of Chiral Polyfluoroaryl Diarylmethanes

Optically pure diarylmethanes are frequently presented in pharmaceuticals and bioactive molecules. However, minor efforts have been devoted to chiral polyfluoroarene-containing diarylmethanes, and their synthesis is still challenging. Herein, we describe an enantioselective Cu/sulfoxide phosphine (SOP) catalyzed nucleophilic substitution reaction by using polyfluoroarenes as the polyfluoroaryl reagent. Under mild conditions, this protocol enables the efficient synthesis of chiral polyfluoroaryl diarylmethanes with fluorinated quaternary stereogenic center in good yields (up to 93%), high regioselectivties, and excellent enantioselectivities (up to 99% ee). Moreover, gram-scale experiments, product derivations, and late-stage diversifications were performed to demonstrate the utility of this method.

FDA-Approved Fluorinated Heterocyclic Drugs from 2016 to 2022

The inclusion of fluorine atoms or heterocyclic moiety into drug structures represents a recurrent motif in medicinal chemistry. The combination of these two features is constantly appearing in new molecular entities with various biological activities. This is demonstrated by the increasing number of newly synthesized fluorinated heterocyclic compounds among the Food and Drug Administration FDA-approved drugs. In this review, the biological activity, as well as the synthetic aspects, of 33 recently FDA-approved fluorinated heterocyclic drugs from 2016 to 2022 are highlighted.

New Approved Drugs Appearing in the Pharmaceutical Market in 2022 Featuring Fragments of Tailor-Made Amino Acids and Fluorine

The strategic fluorination of oxidatively vulnerable sites in bioactive compounds is a relatively recent, widely used approach allowing us to modulate the stability, bio-absorption, and overall efficiency of pharmaceutical drugs. On the other hand, natural and tailor-made amino acids are traditionally used as basic scaffolds for the development of bioactive molecules. The main goal of this review article is to emphasize these general trends featured in recently approved pharmaceutical drugs.

Fluorine-a small magic bullet atom in the drug development: perspective to FDA approved and COVID-19 recommended drugs

During the last twenty years, organic fluorination chemistry established itself as an important tool to get a biologically active compound. This belief can be supported by the fact that every year, we are getting fluorinated drugs in the market in extremely significant numbers. Last year, also ten fluorinated drugs have been approved by FDA and during the COVID-19 pandemic, fluorinated drugs played a very crucial role to control the disease and saved many lives. In this review, we surveyed all ten fluorinated drugs approved by FDA in 2021 and all fluorinated drugs which were directly-indirectly used during the COVID-19 period, and emphasis has been given particularly to their synthesis, medicinal chemistry, and development process. Out of ten approved drugs, one drug pylarify, a radioactive diagnostic agent for cancer was approved for use in positron emission tomography imaging. Also, very briefly outlined the significance of fluorinated drugs through their physical, and chemical properties and their effect on drug development.

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Synthesis of Difluoromethylated Carbinols via a HFIP-Promoted Hydroxydifluoromethylation of Aniline, Indole, and Pyrrole Derivatives with Difluoroacetaldehyde Ethyl Hemiacetal

A hexafluoroisopropanol (HFIP)-promoted hydroxydifluoromethylation of aniline, indole, and pyrrole derivatives with difluoroacetaldehyde ethyl hemiacetal has been developed. This protocol provides a facile and straightforward approach to access diverse difluoromethylated carbinols in good to excellent yields under mild conditions. Furthermore, gram-scale and synthetic derivatization experiments have also been demonstrated.

Synthesis of gem-Difluorinated 1,4-Dienes via Nickel-Catalyzed Three-Component Coupling of (Trifluoromethyl)alkenes, Alkynes, and Organoboronic Acids

Herein, a nickel-catalyzed defluorinative three-component coupling of trifluoromethyl alkenes, internal alkynes, and organoboronic acids is presented. The protocol provides a highly efficient and selective route for the synthesis of structurally diverse gem-difluorinated 1,4-dienes under mild conditions. Mechanistic studies suggest that C-F bond activation proceeds probably through the oxidative cyclization of trifluoromethyl alkenes with Ni(0) species, sequential addition to alkynes, and β-fluorine elimination.

TIES 2.0: A Dual-Topology Open Source Relative Binding Free Energy Builder with Web Portal

Relative binding free energy (RBFE) calculations are widely used to aid the process of drug discovery. TIES, Thermodynamic Integration with Enhanced Sampling, is a dual-topology approach to RBFE calculations with support for NAMD and OpenMM molecular dynamics engines. The software has been thoroughly validated on publicly available datasets. Here we describe the open source software along with a web portal (https://ccs-ties.org) that enables users to perform such calculations correctly and rapidly.

Photoredox-Catalyzed Chlorotrifluoromethylation of Arylallenes: Synthesis of a Trifluoromethyl Building Block

A new class of trifluoromethyl building blocks─2-trifluoromethyl allyl chlorides─have been obtained through a photoredox-catalyzed chlorotrifluoromethylation of aryl allenes. The reaction proceeded in a regio- and stereoselective manner. A trifluoromethylated analog of the flunarizine drug was synthesized.

Design, synthesis, spectroscopic characterizations, single crystal X-ray analysis, in vitro xanthine oxidase and acetylcholinesterase inhibitory evaluation as well as in silico evaluation of selenium-based N-heterocyclic carbene compounds

Herein, eight new NHC-based selenourea derivatives were synthesized and characterized by using spectroscopic method (1H, 19F, and 13C NMR, FT-IR), and elemental analysis techniques. These compounds were synthesized by mixing benzimidazolium salts, potassium carbonate, and selenium powder in ethyl alcohol. Additionally, the molecular and crystal structures of the three compounds (1c, 2b, and 2c) were determined using the single-crystal x-ray diffraction (XRD) method. Diffraction analysis demonstrated the partial carbon-selenium double-bond character of these compounds. All compounds were determined to be highly potent inhibitors for AChE and XO enzymes. The IC50 values for the compounds were found in the range of 0.361-0.754 μM for XO and from 0.995 to 1.746 μM for AChE. The DNA binding properties of the compounds were investigated. These compounds did not have a remarkable DNA binding property. Also, DPPH radical scavenging activities of the compounds were also investigated. Compounds (1c), (2a), (3a), and (3b) exhibited more pronounced DPPH radical scavenging activity when compared to other compounds. Docking studies were applied by using AutoDock 4 to determine interaction mechanism of the selected compounds (1a), (1b), and (3b). The compound (1b) has good binding affinity (-9.78 kcal/mol) against AChE, and (-6.86 kcal/mol) for XO target. Drug similarity properties of these compounds compared to positive controls were estimated and evaluated by ADMET analysis. Furthermore, molecular dynamics simulations have been applied to understand the accuracy of docking studies. These findings and the defined compounds could be potential candidates for the discovery and progress of effective medicine(s) for AChE and XO in the future.Communicated by Ramaswamy H. Sarma.

Benzimidazolium Salts Containing Trifluoromethoxybenzyl: Synthesis, Characterization, Crystal Structure, Molecular Docking Studies and Enzymes Inhibitory Properties

The method for producing 4-trifluoromethoxybenzyl substituted benzimidazolium salts is described in this article. The method is based on the reaction of 4-trifluoromethoxybenzyl substituent alkylating agent with 1-alkylbenzimidazole. This method yielded 1-(4-trifluoromethoxybenzyl)-3-alkylbenzimidazolium bromide salts. These benzimidazolium salts were characterized by using ¹ H-NMR, ¹³ C-NMR, FT-IR spectroscopy, and elemental analysis techniques. The crystal structure of 1f was enlightened by single crystal X-ray diffraction studies. Also, the enzyme inhibition effects of the synthesised compounds were investigated. They demonstrated highly potent inhibition effect on acetylcholinesterase (AChE) and carbonic anhydrases (hCAs) (K_i values are in the range of 7.24±0.99 to 39.12±5.66 nM, 5.57±0.96 to 43.07±11.76 nM, and 4.38±0.43 to 18.68±3.60 nM for AChE, hCA I, and hCA II, respectively). In molecular docking study, the interactions of active compounds showing activity against AChE and hCAs enzymes were examined. The most active compound 1f has -10.90 kcal/mol binding energy value against AChE enzyme, and the potential structure compound 1e, which has activity against hCA I and hCA II enzymes, was -7.51 and -8.93 kcal/mol, respectively.

Base-Promoted (3 + 2) Cycloaddition of Trifluoroacetohydrazonoyl Chlorides with Imidates En Route to Trifluoromethyl-1,2,4-Triazoles

A base-mediated (3 + 2) cycloaddition of trifluoroacetohydrazonoyl chlorides with imidates for the construction of 3-trifluoromethyl-1,2,4-triazoles has been described. This reaction is characterized by readily starting materials, simple reaction conditions, good yields, a broad substrate scope, and excellent regioselectivity. The utility of this protocol has been validated by the synthesis of a drug-like molecule.

Photoredox-Catalyzed Tandem Radical Cyclization/Hydroxylation for the Synthesis of 4-Hydroxyalkyl-3,3-difluoro-γ-lactams

The photoredox-catalyzed radical difluoroalkylation/cyclization/hydroxylation cascade reaction of various 2-bromo-2,2-difluoro-N-arylacetamides containing unactivated alkene moieties has been developed, providing green and efficient access to various 4-hydroxyalkyl-3,3-difluoro-γ-lactams. Control experiments confirmed a radical process, and inexpensive air acted as the sole hydroxy resource. In addition, the highlights of this protocol include good tolerance for a variety functional groups, lower photocatalyst loading, and ease of operation.

Self-Sustaining Fluorination of Active Methylene Compounds and High-Yielding Fluorination of Highly Basic Aryl and Alkenyl Lithium Species with a Sterically Hindered N-Fluorosulfonamide Reagent

Fluorination of carbanions is pivotal for the synthesis of fluorinated compounds, but the current N-F fluorinating agents have significant drawbacks due to many reactive locations that surround the reactive N-F site. By developing a sterically hindered N-fluorosulfonamide reagent, namely N-fluoro-N-(tert-butyl)-tert-butanesulfonamide (NFBB), we discovered a conceptually novel base-catalyzed, self-sustaining fluorination of active methylene compounds and achieved the high-yielding fluorination of the hitherto difficult highly basic (hetero)aryl and alkenyl lithium species. In the former, the mild and high yield fluorination of active methylene compounds exhibited wide functional group tolerance and its novel catalytic fluorination-deprotonation cycle mechanism was demonstrated by deuterium-tracing experiments. In the latter, NFBB reacted with a variety of highly basic (hetero)aryl and alkenyl lithium species to provide the desired fluoro (hetero)arenes and alkenes in unprecedented high or quantitative yields.

FDA-Approved Trifluoromethyl Group-Containing Drugs: A Review of 20 Years

As people around the world regard 2020 as the year of COVID-19, the medical community considers this year to be the second-best year, shared with the year 1996, with respect to the number of drug molecules approved by the US Food and Drug Administration (FDA). Both years, 2020 and 1996, had a record of 53 new drug molecules approved by the FDA. In the year 2020, 53 new chemical entities and 13 biological medicines were approved, including 10 monoclonal antibodies, 2 antibody-drug conjugates, 3 peptides, and 2 oligonucleotides. Among them, most of the compounds were found to have fluorine or fluorine-containing functional groups exhibiting numerous pharmacological activities. Herein, we summarized the trifluoromethyl (TFM, -CF3)-group-containing FDA-approved drugs for the last 20 years. This article specially features and details the previous 20-year literature data, covering CF3-incorporated potential drug molecules, including their syntheses and uses for various diseases and disorders. The review covers the detailed chemistry of 19 FDA-approved drugs in the past 20 years, which contains the TFM group as one of the pharmacophores.

Design and Synthesis of New α-hydroxy β-fluoro/β-trifluoromethyl and Unsaturated Phosphonates from Carbohydrate-Derived Building Blocks via Pudovik and Horner–Wadsworth–Emmons Reactions

Herein, we present the application of fluorinated carbohydrate-derived building blocks for α-hydroxy β-fluoro/β-trifluoromethyl and unsaturated phosphonates synthesis. Pudovik and Horner–Wadsworth–Emmons reactions were applied to achieve this goal. The proposed pathway of the key reactions is supported by the experimental results, as well as quantum chemical calculations. The structure of the products was established by spectroscopic (1D, 2D NMR) and spectrometric (MS) techniques. Based on our data received, we claim that the progress of the Pudovik and HWE reactions is significantly influenced by the acidic protons present in the molecules as assessed by pKa values of the reagent.

The Latest FDA-Approved Pharmaceuticals Containing Fragments of Tailor-Made Amino Acids and Fluorine

Nowadays, the selective introduction of fluorine into bioactive compounds is a mature strategy in the design of drugs allowing to increase efficiency, biological half-life and bio-absorption. On the other hand, amino acids (AAs) represent one of the most ubiquitious classes of naturally occurring organic compounds, which are found in over 40% of newly marked small-molecule pharmaceutical drugs and medical formulations. The primary goal of this work is to underscore two major trends in the design of modern pharmaceuticals. The first is dealing with the unique structural characteristics provided by the structure of amino acids featuring an abundance of functionality and the presence of a stereogenic center, all of which bodes well for the successful development of targeted bioactivity. The second is related to fine-tuning the desired activity and pharmacokinetics by selective introduction of fluorine. Historically, both trends were developed separately as innovative and prolific approaches in modern drug design. However, in recent decades, these approaches are clearly converging leading to an ever-increasing number of newly approved pharmaceuticals containing both structural features of amino acids and fluorine.

Mechanochemical Synthesis of Fluorinated Imines

A number of imines, including 12 new compounds, previously not reported in the literature, derived from variously fluorinated benzaldehydes and different anilines or chiral benzylamines were synthesized by a solvent-free mechanochemical method, which was based on the manual grinding of equimolar amounts of the substrates at the room temperature. In a very short reaction time of only 15 min, the method produced the expected products with good-to-excellent yields. The yields were comparable or significantly higher than those reported in the literature for the imines synthesized by other methods. Importantly, the conditions used for the reactions with aniline derivatives also resulted in the high yields of imines obtained from chiral benzylamines, and can be extended to the synthesis with other similar amines. Structures of all imines were confirmed by NMR spectroscopy: ¹H, ¹³C and ¹⁹F. For four compounds, X-ray structures were also obtained. The synthetic approach presented in this paper contributes to the prevention of environmental pollution and can be easily extended for larger-scale syntheses. The mechanochemical solvent-free method provides a convenient strategy particularly useful for the preparation of fluorinated imines being versatile intermediates or starting material in the synthesis of drugs and other fine chemicals.

Solvent-controlled base-free synthesis of bis(trifluoromethyl)-cyclopropanes and -pyrazolines via cycloaddition of 2-trifluoromethyl-1,3-enynes with 2,2,2-trifluorodiazoethane

A highly efficient solvent-controlled synthesis of bis(trifluoromethyl)cyclopropanes and bis(trifluoromethyl)pyrazolines via a [2 + 1] or [3 + 2] cycloaddition reaction of 2-trifluoromethyl-1,3-conjugated enynes with CF₃CHN₂ was developed. The reactions of 2-trifluoromethyl-1,3-conjugated enynes with CF₃CHN₂ proceeded smoothly under transition-metal and base-free conditions, affording the expected cycloaddition products in good to excellent yields. When DMAc (N,N-dimethylacetamide) was used as the solvent, bis(trifluoromethyl)pyrazolines were obtained; however, in contrast, bis(trifluoromethyl)cyclopropanes were formed by changing the solvent from DMAc to DCE (1,2-dichloroethane).

Amphiphilic Indoles as Efficient Phase-Transfer Catalysts for Bromination in Water

Brominated compounds are important, but they are usually prepared in organic solvents. Here, efficient amphiphilic indole-based phase-transfer organocatalysts were developed for environmentally benign bromination reactions in water. As test reactions, hydroxybromination of olefins and aromatic bromination could be conducted in a greener and more sustainable manner compared with methods using organic solvents, producing the corresponding bromides in good yields. Some pure products could be obtained without column chromatography.

Enantio-, Diastereo- and Regioselective Synthesis of Chiral Cyclic and Acyclic gem-Difluoromethylenes by Palladium-Catalyzed [4+2] Cycloaddition

gem-Difluoromethylene moieties are attractive in medicinal chemistry due to their ability to mimic other more ubiquitous functional groups. Thus, effective asymmetric methods for their construction are highly desirable, especially for the industrial production of chiral drugs. Using a Pd-catalyzed asymmetric [4+2] cycloaddition between substituted-2-alkylidenetrimethylene carbonates and gem-difluoroalkyl ketones, we were able to easily access chiral 1,3-dioxanes that contain a tetrasubstituted difluoroalkyl stereogenic center in cyclic and acyclic skeletons. A novel phosphoramidite ligand, which contains a bulky 1,1-dinaphthylmethanamino moiety, was developed to provide the products in high yield with excellent enantio-, diastereo-, and regioselectivity. Strikingly, the gem-difluoro substitution pattern promotes the reaction, and pentafluoroethylketone, an α,α-difluorinated β-ketoester, and a β-ketosulfone are suitable substrates for this method.

New synthesis of a late-stage tetracyclic key intermediate of lumateperone

New approaches have been tested for the synthesis of lumateperone intermediates. As a result of these efforts, a novel synthesis of the late-stage tetracyclic key intermediate of lumateperone starting from the commercially available quinoxaline is described. The tetracyclic skeleton was constructed by the reaction of 1-trifluoroacetyl-4-aminoquinoxaline with ethyl 4-oxopiperidine-1-carboxylate in a Fischer indole synthesis. The inexpensive starting material, the efficient synthetic steps, and the avoidance of the borane-based reduction step provide a reasonable potential for scalability.

Recent Progress in the Selective Fluorinations of Some Functionalized Cycloalkenes

Organofluorine compounds have had an increasing impact in synthetic organic chemistry and pharmaceutical research over the past two decades. Their syntheses and the development of novel synthetic approaches towards versatile fluorinated small molecules have received great interest. Our research team has designed various selective and stereocontrolled methods for the construction of fluorine-containing small molecular entities, involving the transformation of various functionalized cycloalkenes across their ring olefin bond. The synthetic methodologies developed to access various pharmacologically interesting fluorinated derivatives with multiple chiral centers might be valuable protocols for the preparation of other classes of organic compounds as well.

Catalytic Stereoconvergent Synthesis of Homochiral β-CF3, β-SCF3, and β-OCF3 Benzylic Alcohols

We describe an efficient catalytic strategy for enantio- and diastereoselective synthesis of homochiral β-CF₃, β-SCF₃, and β-OCF₃ benzylic alcohols. The approach is based on dynamic kinetic resolution (DKR) with Noyori–Ikariya asymmetric transfer hydrogenation leading to simultaneous construction of two contiguous stereogenic centers with up to 99.9% ee, up to 99.9:0.1 dr, and up to 99% isolated yield. The origin of the stereoselectivity and racemization mechanism of DKR is rationalized by density functional theory calculations. Applicability of the previously inaccessible chiral fluorinated alcohols obtained by this method in two directions is further demonstrated: As building blocks for pharmaceuticals, illustrated by the synthesis of heat shock protein 90 inhibitor with in vitro anticancer activity, and in particular, needle-shaped crystals of representative stereopure products that exhibit either elastic or plastic flexibility, which opens the door to functional materials based on mechanically responsive chiral molecular crystals.