Dialkylzinc-Mediated Cross-Coupling Reactions of Perfluoroalkyl and Perfluoroaryl Halides with Aryl Halides

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.

Diverse Synthetic Transformations Using 4-Bromo-3,3,4,4-tetrafluorobut-1-ene and Its Applications in the Preparation of CF2 CF2 -Containing Sugars, Liquid Crystals, and Light-Emitting Materials

Organic molecules with fluoroalkylene scaffolds, especially a tetrafluoroethylene (CF2 CF2 ) moiety, in their molecular structures exhibit unique biological activities, or can be applied to functional materials such as liquid crystals and light-emitting materials. Although several methods for the syntheses of CF2 CF2 -containing organic molecules have been reported to date, they have been limited to methods using explosives and fluorinating agents. Therefore, there is an urgent need to develop simple and efficient approaches to synthesize CF2 CF2 -containing organic molecules from readily available fluorinated substrates using carbon-carbon bond formation reactions. This personal account summarizes the simple and efficient transformation of functional groups at both ends of 4-bromo-3,3,4,4-tetrafluorobut-1-ene and discusses its synthetic applications to biologically active fluorinated sugars and functional materials, such as liquid crystals and light-emitting molecules.

Perfluoroalkoxylation reaction via dual concurrent catalysis

A catalytic amount of CsI enables dual concurrent activation of poorly reactive perfluoroalkoxide and alkyl halides, especially alkyl chlorides, leading to the formation of diverse perfluoroalkoxylated organic compounds. Installation of perfluoroalkoxy groups by this methodology is cost-effective, circumventing the need for over-stoichiometric cesium or silver salts. This methodology also provides high functional group compatibility and tolerance of sterically hindered substrates.

Regioselective and late-stage polyfluoroarylation of arenes with diverse fluoroaryl nucleophiles via Pd-catalysis

Dehydrogenative coupling of arenes with fluoroaryl nucleophiles enables the efficient synthesis of fluoroaromatic compounds from readily available starting materials.

Modern methods for the synthesis of perfluoroalkylated aromatics

Perfluoroalkyl-containing substances (PFAS), have become omnipresent materials in the modern world for both commercial and research applications. Compounds such as perfluoroalkylated arenes and heteroarenes have found uses in surfactants, lubricants, and flame retardants as a result of their astonishing chemical stability. Consequently, the synthesis of such compounds encompasses a large body of scientific articles and patents developed in the previous century. Most recent reviews on this subject have thus focused on summarizing this traditional literature, and have thereby spurred the development of a new wave of reaction manifolds employing modern synthesis principles. This new generation of methodologies focuses on the greener synthesis of perfluoroalkylated aromatic scaffolds, through the use of more efficient organometallic reactions, as well as by photochemical and electrochemical strategies. Herein, we will summarize this cohort of reactions while highlighting current challenges and future desirable outcomes for their environmentally friendly synthesis.

Diethylzinc-Mediated Radical 1,2-Addition of Alkenes and Alkynes

A novel diethylzinc-mediated radical 1,2-addition of perfluoroalkyl iodides to unactivated alkenes and alkynes is presented, which demonstrates a novel way to generate an ethyl difluoroacetate radical. This method is highly efficient and gives full conversions of the substrates, high yields of the products, and negligible byproducts and requires no column chromatography purifications. The mild conditions enable this protocol to exhibit excellent functional group compatibility.

Copper-Catalyzed Perfluoroalkylation of Alkynyl Bromides and Terminal Alkynes

A copper-catalyzed one-pot perfluoroalkylation of alkynyl bromides and terminal alkynes has been disclosed, and the corresponding perfluoroalkylated alkynes could be attained in good to excellent yields. The new straightforward transformation shows high efficiency (0.01-0.5 mol % catalyst loading), broad substrate scope, and remarkable functional group tolerance and provides a facile approach for useful application in life and material sciences.

Ligand Promoted Olefination of Anilides for Indirectly Introducing Fluorinated Functional Groups via Palladium Catalyst

We report a palladium-catalyzed, ligand promoted, C-H fluorine-containing olefination of anilides with 4-bromo-3,3,4,4-tetrafluorobutene as the fluorinated reagent, which has a potential transformation into other compounds due to its -CF₂CF₂Br functional group. -CF₂CF₂H was obtained by using the mild reducing agent sodium borohydride. Bioactive compounds such as aminoglutethimide derivative and propham were well-tolerated in this reaction, both of which highlight the synthetic importance of this method.

Silver-Mediated Perfluoroalkylation of Terminal Alkynes with Perfluoroalkyl Iodides

The incorporation of a perfluoroalkyl group (R_F) into drug candidates has become an increasingly important strategy in drug molecule design. In this study, the silver-mediated perfluoroalkylation reaction based on the addition-elimination process of terminal alkynes which was initiated by a perfluoroalkyl radical to form a C(sp)-R_F bond has been developed. The reaction proceeds under mild conditions using readily available, low-cost perfluoroalkyl iodides as the sources of the R_F group. This method allows access to a variety of perfluoroalkylated alkynes.

Recent Advances of the Halogen-Zinc Exchange Reaction

For the preparation of zinc organometallics bearing highly sensitive functional groups such as ketones, aldehydes or nitro groups, especially mild halogen-zinc exchange reagents have proven to be of great potential. In this Minireview, the latest research in the area of the halogen-zinc exchange reaction is reported, with a special focus lying on novel dialkylzinc reagents complexed with lithium alkoxides. Additionally, the preparation and application of organofluorine zinc reagents and transition-metal-catalyzed halogen-zinc exchange reactions are reviewed.

Visible-Light Induced Radical Perfluoroalkylation/Cyclization Strategy To Access 2-Perfluoroalkylbenzothiazoles/Benzoselenazoles by EDA Complex

A novel and practical fluoroalkyl radical-initiated cascade reaction was developed to access diverse 2-fluoroalkylbenzothiazoles by reacting various fluoroalkyl radical sources, including perfluoroalkyl iodide (IC _nF_{2 n+1}, n = 3-8, 10), ICF(CF₃)₂, ICF₂COOEt, ICF₂CF₂Cl, or ICF₂CF₂Br, tetramethylethane-1,2-diamine (TMEDA), and 2-isocyanoaryl thioethers in tetrahydrofuran under nitrogen atmosphere and blue-light irradiation conditions. Furthermore, this one-pot protocol could well be expanded to access various 2-fluoroalkylbenzoselenazoles starting from (2-isocyanophenyl)(methyl)selane, perfluoroalkyl iodides (IC _nF_{2 n+1}, n = 3-8) or ICF₂COOEt and TMEDA.

Copper-Catalyzed Perfluoroalkylation of Allyl Phosphates with Stable Perfluoroalkylzinc Reagents

A general and practical method for copper-catalyzed cross-coupling of allyl phosphates with stable perfluoroalkylzinc reagents has been developed. The reaction proceeds under mild reaction conditions with high efficiency, good functional group tolerance, and high regio- and stereoselectivities and provides general, straightforward, and useful access to allyl-perfluoroalkyl compounds. Preliminary mechanistic studies reveal that the allyl copper intermediate may be involved in the catalytic cycle.

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

(1,1,2,2-Tetrafluorobut-3-en-1-yl)zinc bromide was prepared by insertion of the zinc–silver couple into the CF₂–Br bond of commercially available 4-bromo-3,3,4,4-tetrafluorobut-1-ene in DMF at 0 °C for 0.5 h, The resultant polyfluorinated zinc reagent was found to be thermally stable at ambient temperature and storable for at least 1.5 years in the refrigerator. This CF₂CF₂-containing organozinc reagent could be easily transmetallated to copper species, which underwent cross-coupling reactions with various aromatic iodides or acyl chlorides to produce a broad range of CF₂CF₂-containing organic molecules in good-to-excellent yields. Therefore, the zinc reagent could become a new and practical synthetic tool for producing functional molecules with a CF₂CF₂ fragment.

A Cross-Dehydrogenative Annulation Strategy towards Synthesis of Polyfluorinated Phenanthridinones with Copper

The first cross-dehydrogenative annulation of (hetero)aromatic amides with polyfluoro(hetero)arenes is presented. This operationally simple oxidative annulation process is mediated by inexpensive copper salt, accommodates a wide range of substrates with exquisite chemo- and regioselectivity profile, and produces demanding polyfluorinated phenanthridinones in high yields (up to 92 %). Using alkenyl amides under identical conditions, the synthesis of polyfluorinated 2-quinolones has also been accomplished. Given the importance of fluorinated heterocycles in the pharmaceutical industry and drug discovery, this work is highly significant.

Heptafluoroisopropyl diazomethane (i-C3F7CHN2): in situ generation and synthesis of pyrazoles

A novel chemical reagent, heptafluoroisopropyl diazomethane (i-C₃F₇CHN₂), has been generated in situ in aqueous media. It reacts with electron-deficient alkynes towards polyfluorinated pyrazoles that are important in agrochemistry.

Palladium-Catalyzed Negishi Cross-Coupling Reaction of Aryl Halides with (Difluoromethyl)zinc Reagent

The palladium-catalyzed Negishi cross-coupling reaction of aryl iodides and bromides with (difluoromethyl)zinc reagent bearing a diamine such as TMEDA is achieved to provide the difluoromethylated aromatic compounds in good to excellent yields. The advantages of (difluoromethyl)zinc reagent are that (1) the derivatives, which possess different stability and reactivity, can be readily prepared via ligand screening and (2) transmetalation of a difluoromethyl group from the zinc reagent to palladium catalyst efficiently proceeds without an activator.

Copper-Catalyzed Difluoromethylation of Aryl Iodides with (Difluoromethyl)zinc Reagent

The combination of difluoroiodomethane and zinc dust or diethylzinc can readily lead to (difluoromethyl)zinc reagents. Therefore, the first copper-catalyzed difluoromethylation of aryl iodides with the zinc reagents is accomplished to afford the difluoromethylated arenes. The reaction proceeds efficiently through the ligand/activator-free operation without addition of ligands for copper catalyst (e.g., phen and bpy) and activators for zinc reagent (e.g., KF, CsF, and NaO-t-Bu). Moreover, transmetalation of the CF2H group from zinc reagent to copper catalyst proceeds even at room temperature to form the cuprate [Cu(CF2H)2](-).

Direct isoperfluoropropylation of arenediazonium salts with hexafluoropropylene

Perfluoropropylene can be used directly for isoperfluoropropylation of arenediazonium salts in the presence of silver fluoride and cuprous iodide. A practical tandem diazotization and isoperfluoropropylation protocol was developed for aniline derivatives to generate isoperfluoropropylarenes with good functional-group compatibility.

A class of effective decarboxylative perfluoroalkylating reagents: [(phen)2Cu](O2CRF)

A class of effective reagents [(phen)₂Cu](O₂CR_F) for the decarboxylative perfluoroalkylation of aryl and heteroaryl halides have been invented.

Efficient generation of perfluoroalkyl radicals from sodium perfluoroalkanesulfinates and a hypervalent iodine(iii) reagent: mild, metal-free synthesis of perfluoroalkylated organic molecules

Introduction of perfluoroalkyl groups into various organic molecules was achieved from sodium perfluoroalkanesulfinates and a hypervalent iodine(iii) reagent.

Direct heptafluoroisopropylation of arylboronic acids via hexafluoropropene (HFP)

A novel and straightforward strategy for heptafluoroisopropylation of arylboronic acids under mild reaction conditions has been developed, directly using hexafluoropropene (HFP). This method provides a new way to synthesize a variety of synthetically useful heptafluoroisopropylated arenes. No extra oxidant was used in this reaction.

Perfluoroalkylation reactions of (hetero)arenes

Methods for the perfluoroalkylation of (hetero)arenes can be classified as thermal and photochemical, which in turn can be conducted in the presence or absence of metals.