Well-Defined CuC2F5Complexes and Pentafluoroethylation of Acid Chlorides

Synthesis and application of well-defined [Ph4P]+[Cu(CF2CF3)2]- complex as a versatile pentafluoroethylating reagent

We herein describe the preparation and application of a new bispentafluoroethylated organocuprate [Ph4P]+[Cu(CF2CF3)2]-. This complex has demonstrated a remarkable range of reactivities towards carboxylic acids, diazonium salts, organic halides, boronic esters, terminal alkynes and (hetero)arenes as a versatile pentafluoroethylating reagent. The construction of C(sp3)-/C(sp2)-/C(sp)-CF2CF3 bonds can therefore be achieved using a single reagent.

CsF-Catalyzed Fluoroacylation of Tetrafluoroethylene Using Acyl Fluorides for the Synthesis of Pentafluoroethyl Ketones

A catalytic method for the synthesis of pentafluoroethyl ketones­ has been developed. The cesium fluoride catalyst can be used to convert acyl fluorides into the pentafluoroethyl ketones under tetrafluoroethylene pressure without generating stoichiometric quantities of chemical waste. Mechanistic studies suggest that high reaction temperature is crucial for the ketone to be the major product.

Stable and Storable N(CF3 )2 Transfer Reagents

Fluorinated groups are essential for drug design, agrochemicals, and materials science. The bis(trifluoromethyl)amino group is an example of a stable group that has a high potential. While the number of molecules containing perfluoroalkyl, perfluoroalkoxy, and other fluorinated groups is steadily increasing, examples with the N(CF₃ )₂ group are rare. One reason is that transfer reagents are scarce and metal-based storable reagents are unknown. Herein, a set of Cu^I and Ag^I bis(trifluoromethyl)amido complexes stabilized by N- and P-donor ligands with unprecedented stability are presented. The complexes are stable solids that can even be manipulated in air for a short time. They are bis(trifluoromethyl)amination reagents as shown by nucleophilic substitution and Sandmeyer reactions. In addition to a series of benzylbis(trifluoromethyl)amines, 2-bis(trifluoromethyl)amino acetate was obtained, which, upon hydrolysis, gives the fluorinated amino acid N,N-bis(trifluoromethyl)glycine.

Pentafluoroethylation of Carbonyl Compounds by HFC-125 via the Encapsulation of the K Cation with Glymes

A simple protocol to overcome the explosive pentafluoroethylation of carbonyl compounds by HFC-125 is described. The use of potassium (K) bases with triglyme or tetraglyme as a solvent safely yields the pentafluoroethylation products in good to high yields. The experimental results suggest that an encapsulation of the K cation by glymes as K(glyme)₂ inhibits the contact between the K cation and the reactive anionic pentafluoroethyl counterion, preventing their transformation into KF and explosive tetrafluoroethylene (TFE). The generation of sterically demanding [K(G3)₂]⁺ and [K(G4)₂]⁺ is an effective way as an unstable pentafluoroethyl anion reservoir.

Radical Pentafluoroethylation of Unactivated Alkenes Using CuCF2CF3

We have found that the CuCF₂CF₃ complex generated from low-cost pentafluoroethane is a convenient and practical source for the CF₂CF₃ radical under aerobic conditions at room temperature. Using this system, readily available unactivated alkenes can be pentafluoroethylated to provide novel allylic CF₂CF₃ compounds with excellent E-selectivity and functional group tolerability. Mechanistic studies including TEMPO-CF₂CF₃ trapping and radical clock experiments provided strong evidence for radical pathways, offering a new opportunity for copper-mediated radical perfluoroalkylation.

Trifluoromethylthiolation, Trifluoromethylation, and Arylation Reactions of Difluoro Enol Silyl Ethers

This study reports a new application area of difluoro enol silyl ethers, which can be easily obtained from trifluoromethyl ketones. The main focus has been directed to the electrophilic fluoroalkylation and arylation methods. The trifluoromethylthiolation of difluoro enol silyl ethers can be used for the construction of a novel trifluoromethylthio-α,α-difluoroketone (−COCF₂SCF₃) functionality. The −CF₂SCF₃ moiety has interesting properties due to the electron-withdrawing, albeit lipophilic, character of the SCF₃ group, which can be combined with the high electrophilicity of the difluoroketone motif. The methodology could also be extended to difluoro homologation of the trifluoromethyl ketones using the Togni reagent. In addition, we presented a method for transition-metal-free arylation of difluoro enol silyl ethers based on hypervalent iodines.

Copper-based fluorinated reagents for the synthesis of CF2R-containing molecules (R ≠ F)

Over the years, the development of new methodologies for the introduction of various fluorinated motifs has gained a significant interest due to the importance of fluorine-containing molecules in the pharmaceutical and agrochemical industries. In a world eager to eco-friendlier tools, the need for innovative methods has been growing. To address these two challenges, copper-based reagents were developed to introduce CF2H, CF2RF, CF2CH3, CF2PO(OEt)2 and CF2SO2Ph motifs on a broad range of substrates. Copper-based fluorinated reagents have the advantage of being inexpensive and generally in situ generated or prepared in a few steps, which make them convenient to use. In this review, an overview of the recent advances made for the synthesis of fluorinated molecules using copper-based fluorinated reagents will be given.

N-Heterocyclic Carbene Complexes of Copper, Nickel, and Cobalt

The emergence of N-heterocyclic carbenes as ligands across the Periodic Table had an impact on various aspects of the coordination, organometallic, and catalytic chemistry of the 3d metals, including Cu, Ni, and Co, both from the fundamental viewpoint but also in applications, including catalysis, photophysics, bioorganometallic chemistry, materials, etc. In this review, the emergence, development, and state of the art in these three areas are described in detail.

Copper-Promoted Functionalization of Organic Molecules: from Biologically Relevant Cu/O2 Model Systems to Organometallic Transformations

Copper is one of the most abundant and less toxic transition metals. Nature takes advantage of the bioavailability and rich redox chemistry of Cu to carry out oxygenase and oxidase organic transformations using O₂ (or H₂O₂) as oxidant. Inspired by the reactivity of these Cu-dependent metalloenzymes, chemists have developed synthetic protocols to functionalize organic molecules under enviormentally benign conditions. Copper also promotes other transformations usually catalyzed by 4d and 5d transition metals (Pd, Pt, Rh, etc.) such as nitrene insertions or C-C and C-heteroatom coupling reactions. In this review, we summarized the most relevant research in which copper promotes or catalyzes the functionalization of organic molecules, including biological catalysis, bioinspired model systems, and organometallic reactivity. The reaction mechanisms by which these processes take place are discussed in detail.

Synthesis and Reactivity of Mn–CF3 Complexes

The synthesis, characterization and reactivity of several bi- and tridentate, N-ligated manganese carbonyl trifluoromethyl complexes are presented. These complexes exhibit elongated Mn–CCF3 bonds (versus Mn(CF3)(CO)5), suggesting a lability that could be utilized for the transfer or insertion of the CF3 functional group into organic substrates. Unlike their Mn–X congeners (X = Cl, Br), these Mn–CF3 complexes exhibit a preference for hard donor ancillary ligands, thus enabling the synthesis of 4 N-ligated Mn–CF3 complexes including a mixed-donor tridentate complex using an NNS Schiff base ([2-(methylthio)-N-(1-(pyridin-2-yl)ethylidene)aniline]). Although we have not yet identified efficient CF3 transfer reactions, fluoride abstraction from the Mn–CF3 complexes using trimethylsilyl triflate affords the first stable Mn fluorocarbenes as evidenced by 19F NMR spectroscopy.

Highly enantioselective addition of dimethylzinc to fluorinated alkyl ketones, and the mechanism behind it

Switching the solvent from toluene to dichloromethane results in a very important enhancement in the yield and enantiomeric excess of nucleophilic addition.

Quantitative DFT modeling of product concentration in organometallic reactions: Cu-mediated pentafluoroethylation of benzoic acid chlorides as a case study

DFT calculations are widely used for computing properties, reaction mechanisms and energy profiles in organometallic reactions. A qualitative agreement between the experimental and the calculated results seems to usually be enough to validate a computational methodology but recent advances in computation indicate that a nearly quantitative agreement should be possible if an appropriate DFT study is carried out. Final percent product concentrations, often reported as yields, are by far the most commonly reported properties in experimental metal-mediated synthesis studies but reported DFT studies have not focused on predicting absolute product amounts. The recently reported stoichiometric pentafluoroethylation of benzoic acid chlorides (R-C₆H₄COCl) with [(phen)Cu(PPh₃)C₂F₅] (phen = 1,10-phenanthroline, PPh₃ = triphenylphosphine) has been used as a case study to check whether the experimental product concentrations can be reproduced by any of the most popular DFT approaches with high enough accuracy. To this end, the Gibbs energy profile for the pentafluoroethylation of benzoic acid chloride has been computed using 14 different DFT methods. These computed Gibbs energy profiles have been employed to build kinetic models predicting the final product concentration in solution. The best results are obtained with the D3-dispersion corrected B3LYP functional, which has been successfully used afterwards to model the reaction outcomes of other simple (R = o-Me, p-Me, p-Cl, p-F, etc.) benzoic acid chlorides. The product concentrations of more complex reaction networks in which more than one position of the substrate may be activated by the copper catalyst (R = o-Br and p-I) are also predicted appropriately.

(18)F-Labeling of Arenes and Heteroarenes for Applications in Positron Emission Tomography

Diverse radiochemistry is an essential component of nuclear medicine; this includes imaging techniques such as positron emission tomography (PET). As such, PET can track diseases at an early stage of development, help patient care planning through personalized medicine and support drug discovery programs. Fluorine-18 is the most frequently used radioisotope in PET radiopharmaceuticals for both clinical and preclinical research. Its physical and nuclear characteristics (97% β(+) decay, 109.8 min half-life, 635 keV positron energy) and high specific activity make it an attractive nuclide for labeling and molecular imaging. Arenes and heteroarenes are privileged candidates for (18)F-incorporation as they are metabolically robust and therefore widely used by medicinal chemists and radiochemists alike. For many years, the range of (hetero)arenes amenable to (18)F-fluorination was limited by the lack of chemically diverse precursors, and of radiochemical methods allowing (18)F-incorporation in high selectivity and efficiency (radiochemical yield and purity, specific activity, and radio-scalability). The appearance of late-stage fluorination reactions catalyzed by transition metal or small organic molecules (organocatalysis) has encouraged much research on the use of these activation manifolds for (18)F-fluorination. In this piece, we review all of the reactions known to date to install the (18)F substituent and other key (18)F-motifs (e.g., CF3, CHF2, OCF3, SCF3, OCHF2) of medicinal relevance onto (hetero)arenes. The field has changed significantly in the past five years, and the current trend suggests that the radiochemical space available for PET applications will expand rapidly in the near future.

Isolation and characterization of copper(iii) trifluoromethyl complexes and reactivity studies of aerobic trifluoromethylation of arylboronic acids

Novel phenCu^III–CF₃ complexes, isolated purely and fully characterized, are highly reactive for aerobic trifluoromethylation of arylboronic acids.

Ligand-dependent formation of ion-pair CuI/CuIII trifluoromethyl complexes containing bisphosphines

Novel ion-pair Cu^I/Cu^III trifluoromethyl complexes with representative bisphosphines are isolated and fully characterized to feature square planar [Cu^III(CF₃)₄]⁻ and tetrahedral [L₂Cu]⁺ units. They show unprecedented excellent reactivity for aerobic trifluoromethylation of arylboronic acids in generally good to quantitative yields.