Copper-Catalyzed Regioselective Monodefluoroborylation of Polyfluoroalkenes en Route to Diverse Fluoroalkenes

Synthesis of Axially Chiral Monofluoroalkenes via Nickel-Catalyzed Reductive Cross-Coupling of gem-Difluoroalkenes

Enantioenriched monofluoroalkenes are important structural motifs in life science and functional materials. To date, only limited strategies were reported for the synthesis of monofluoroalkenes with stereogenic carbon centers; the axially chiral counterpart is still highly desirable. Herein, we report Ni-catalyzed defluorinative cross-electrophile coupling of gem-difluoroalkenes with biaryl electrophiles for the synthesis of axially chiral monofluoroalkenes. The resulting axially chiral monofluoroalkenes are formed with excellent regio- and stereoselectivities. Synthetic transformation of these axially enantioenriched monofluoroalkenes was also demonstrated.

Regio-, stereo-, and enantioselective ipso- and migratory defluorinative olefin cross-coupling to access highly functionalized monofluoroalkenes

Monofluoroalkenes serve as nonhydrolyzable mimetics of amides and are frequently encountered in drug candidates. Herein we report a regio-, enantio-, and stereoselective NiH-catalyzed ipso- and migratory defluorinative olefin cross-coupling employing readily available olefins and gem-difluoroalkenes under mild conditions. This approach enables the efficient synthesis of a broad array of structurally diverse monofluoroalkenes bearing a tertiary allylic stereogenic center. Mechanistically, the challenging migratory defluorinative olefin cross-coupling process is successfully realized through a ligand relay catalytic strategy, enabling the formal C(sp3)-H/C(sp2)-F activation with high levels of regio-, stereo-, and enantiocontrol.

Copper-catalyzed highly switchable defluoroborylation and hydrodefluorination of 1-(trifluoromethyl)alkynes

CF2-containing compounds hold significant potential in drug discovery, organic synthesis, and materials science. However, synthesizing various CF2-containing building blocks from a single compound remains challenging. Here, we present a Cu-catalyzed, switchable defluoroborylation and hydrodefluorination of trifluoromethylated alkynes, yielding four types of CF2-containing compounds. The chemo- and regio-selective sp2/sp3 1,2-diborylation and sp2 monoborylation of 1-(trifluoromethyl)alkynes are controlled by adjusting the solvent and ligand quantity. Additionally, altering the base allows selective generation of gem-difluoroalkenes or difluoromethylalkenes. Notably, our method prevents over-defluorination of the CF3 group on unsaturated C-C bonds during nucleophilic additions, preserving the pharmaceutically valuable CF2 group. Experimental data and density functional theory (DFT) calculations elucidate the regioselectivities of Cu-Bpin addition and the regulatory role of the ligand in selective deborylation processes.

Palladium-Catalyzed Regioselective Monofluoroallylation of Indoles with gem-Difluorocyclopropanes

We present a palladium-catalyzed ring-opening reaction that induces indoles to cross-couple with gem-difluorocyclopropanes. The reaction proceeds through a domino process of C-C bond activation and C-F bond elimination, followed by C-C(sp2) coupling to produce various 2-fluoroallylindoles. This method is characterized by its high functional group tolerance, good yields and high regioselectivity, under base-free conditions. The synthetic utility of the products is illustrated by the functionalization of the NH and C2 positions of the indole scaffold.

1,2-Difluoroethylene (HFO-1132): synthesis and chemistry

This article provides a comprehensive overview of the synthesis and chemistry of 1,2-difluoroethylene (HFO-1132). The major routes for the preparation of the E- and Z-isomer of HFO-1132 are reviewed, along with the chemistry in radical, nucleophilic, and electrophilic reactions.

Chemoselective Thioacylation of Amines Enabled by Synergistic Defluorinative Coupling

A mild and chemoselective method for the thioacylation of amines, including amino acids and peptides, using gem-difluoroalkenes and sulfide, is reported. The distinguishing of the different nucleophilic sites (S-site and diverse N-sites) by the chemoselective C-F bond functionalization of gem-difluoroalkenes enables the unique synergistic defluorinative coupling reaction. This reaction features mild conditions, is operationally simple, efficient, and gram-scalable, tolerates various functional groups, and is activator-free and without racemization. Thioamide moieties were incorporated site-specifically into bioactive compounds. The proposed mechanism is illustrated by a DFT calculation.

Stereodivergent Palladium-Catalyzed C-F Bond Functionalization of gem-Difluoroalkenes

We herein describe a stereodivergent C-F bond functionalization of gem-difluoroalkenes. Using trisubstituted β,β-difluoroacrylates, both E and Z monofluoroalkene products can be obtained with excellent diastereoselectivities. The design of two different reaction manifolds, i.e., Pd(II)- versus Pd(0)-catalyzed cross-coupling of boronic acids, is the key to stereocontrol.

Design, Synthesis, and Antifungal Activities of Novel Potent Fluoroalkenyl Succinate Dehydrogenase Inhibitors

The development of new fungicide molecules is a crucial task for agricultural chemists to enhance the effectiveness of fungicides in agricultural production. In this study, a series of novel fluoroalkenyl modified succinate dehydrogenase inhibitors were synthesized and evaluated for their antifungal activities against eight fungi. The results from the in vitro antifungal assay demonstrated that compound 34 exhibited superior activity against Rhizoctonia solani with an EC50 value of 0.04 μM, outperforming commercial fluxapyroxad (EC50 = 0.18 μM) and boscalid (EC50 = 3.07 μM). Furthermore, compound 34 showed similar effects to fluxapyroxad on other pathogenic fungi such as Sclerotinia sclerotiorum (EC50 = 1.13 μM), Monilinia fructicola (EC50 = 1.61 μM), Botrytis cinerea (EC50 = 1.21 μM), and also demonstrated protective and curative efficacies in vivo on rapeseed leaves and tomato fruits. Enzyme activity experiments and protein-ligand interaction analysis by surface plasmon resonance revealed that compound 34 had a stronger inhibitory effect on succinate dehydrogenase compared to fluxapyroxad. Additionally, molecular docking and DFT calculation confirmed that the fluoroalkenyl unit in compound 34 could enhance its binding capacity with the target protein through p-π conjugation and hydrogen bond interactions.

Streamlining Fluoroalkenyl Arene Synthesis Illuminated with Mechanistic Insights

Fluorinated compounds are a staple of modern-day chemical innovation, and efficient strategies for their synthesis are highly valuable. In this chemical space, fluoroalkenes continue to be the object of much interest across diverse fields, including drug development and pharmaceuticals with active roles as bioisosteres. Herein, in expanding chemists' synthetic toolbox for constructing valuable organofluorine compounds, we report a "pipeline" strategy for the synthesis of fluorinated olefins, viz., gem-difluoroalkenyl and monofluoroalkenyl arenes with high E-isomeric selectivity. The advantages of this streamlined synthetic protocol include mild reaction conditions, operational simplicity, broad substrate scope, and good to excellent yields, even at gram scales. Critical to this robust procedure is the use of widely available and inexpensive "scavenger" solid-support Merrifield peptide resin for removing phosphine impurities. Further computational investigations offering clarity into this reactivity are disclosed.

Total Syntheses of Borolithochromes A, D and G

Total syntheses of borolithochromes A, D and G, red pigments isolated from fossils of Jurassic putative red alga Solenopora jurassica, have been achieved. The benzo[gh]tetraphene skeletons of the borate ligands in these substances were constructed using Diels-Alder reactions of aryl dienes with naphthoquinone, followed by intramolecular Corey-Chaykovsky reactions. Complexation of these ligands with trimethyl borate generated homocomplexes, which upon sequential O-demethylation produced borolithochromes A and G. In the route to borolithochrome D, a heterocomplex was prepared by stepwise complexation of the ligands with 2-(dimethylamino)ethyl dimethyl borate. The strategy devised to accomplish the first total synthesis of borolithochromes A, D and G should be applicable to the preparation of other borolithochromes as well as spiroborates possessing two fused polycyclic aromatic ligands.

Acyclic Boryl Complexes of Copper(I)

Reaction of (6-Dipp)CuOtBu (6-Dipp=C{NDippCH2 }2 CH2 , Dipp=2,6-iPr2 C6 H3 ) with B2 (OMe)4 provided access to (6-Dipp)CuB(OMe)2 via σ-bond metathesis. (6-Dipp)CuB(OMe)2 was characterised by NMR spectroscopy and X-ray crystallography and shown to be a monomeric acyclic boryl of copper. (6-Dipp)CuB(OMe)2 reacted with ethylene and diphenylacetylene to provide insertion compounds into the Cu-B bond which were characterised by NMR spectroscopy in both cases and X-ray crystallography in the latter. It was also competent in the rapid catalytic deoxygenation of CO2 in the presence of excess B2 (OMe)4 . Alongside π-insertion, (6-Dipp)CuB(OMe)2 reacted with LiNMe2 to provide a salt metathesis reaction at boron, giving (6-Dipp)CuB(OMe)NMe2 , a second monomeric acyclic boryl, which also cuproborated diphenylacetylene. Computational interrogation validated these acyclic boryl species to be electronically similar to (6-Dipp)CuBpin.

Palladium-Catalyzed Cross-Coupling of gem-Difluorocyclopropanes with gem-Diborylalkanes for the Synthesis of Boryl-Substituted Fluorinated Alkenes

This study presents a novel method for the regioselective coupling of gem-difluorinated cyclopropanes with gem-diborylmethane, utilizing a Pd-catalyst system. This innovative approach enables the synthesis of 2-fluoroalkenyl monoboronate scaffolds with high Z-selectivity. The resulting products undergo further transformations, including oxidation, Suzuki cross-coupling, and trifluoroborylation, all of which are achieved with good yields. This work introduces a valuable synthetic pathway to access important fluorinated compounds for various applications in organic chemistry.

Synthetic Advantages of Defluorinative C-F Bond Functionalization

Much progress has been made in the development of methods to both create compounds that contain C-F bonds and to functionalize C-F bonds. As such, C-F bonds are becoming common and versatile synthetic functional handles. This review summarizes the advantages of defluorinative functionalization reactions for small molecule synthesis. The coverage is organized by the type of carbon framework the fluorine is attached to for mono- and polyfluorinated motifs. The main challenges, opportunities and advances of defluorinative functionalization are discussed for each class of organofluorine. Most of the text focuses on case studies that illustrate how defluorofunctionalization can improve routes to synthetic targets or how the properties of C-F bonds enable unique mechanisms and reactions. The broader goal is to showcase the opportunities for incorporating and exploiting C-F bonds in the design of synthetic routes, improvement of specific reactions and advent of new methods.

N-Heterocyclic Carbenes with Polyfluorinated Groups at the 4- and 5-Positions from [3 + 2] Cycloadditions between Formamidinates and cis-1,2-Difluoroalkene Derivatives

We herein report the formation of fluorinated N-heterocyclic carbenes (NHCFs) that bear fluorine atoms at the 4- and 5-positions of the imidazol-2-ylidene ring. Treatment of sodium N,N'-bis(aryl)formamidinates with tetrafluoroethylene followed by the addition of LiBF4 induced a [3 + 2] cycloaddition to afford 4,5-difluorinated imidazolium salts, which served as the precursors for 4,5-difluorinated NHCs. A key feature of this procedure is its applicability to other perfluorinated compounds, which enabled us to incorporate polyfluorinated functional groups at 4- and 5-positions on the imidazol-2-ylidene skeleton. Thus, employing octafluorocyclopentene and hexafluorobenzene led to the formation of 4,4,5,5,6,6-hexafluoro-1,3-diaryl-3,4,5,6-tetrahydrocyclopenta[d]imidazolium (CypIPrF·HBF4) and 4,5,6,7-tetrafluoro-1,3-diarylbenzimidazolium (BIPrF·HBF4) salts, respectively. A thorough NMR analysis of these NHCFs, their selenium adducts, and their tricarbonyl nickel complexes, (NHCF)Ni(CO)3, demonstrated that the fluorine substituents, contrary to expectations, tend to act as electron donors owing to the considerable positive mesomeric effect, while the perfluorocyclopentene-fused and tetrafluorobenzo-fused rings are pure electron acceptors due to their strong negative inductive effect. The unique and increased π-accepting character of the perfluorocyclopentene-fused and tetrafluorobenzo-fused NHCFs in both stoichiometric and catalytic reactions is further demonstrated by employing (NHCF)Ni(CO)3 and (NHCF)AuCl species, respectively. Moreover, an analysis of the % buried volume (%Vbur) values clearly suggests that the modification of the NHC backbone with polyfluorinated groups can drastically alter the electronic properties of the NHC ligand without substantially changing its steric properties. Our experimental results were further corroborated by a series of computational calculations.

Synthesis, Structures, and Aggregation-Induced Emission Properties of Distyrylbenzene Derivatives Containing Fluorine Groups

Distyrylbenzene derivatives with substituents on the vinylene moieties have been studied due to interest in their optoelectronic properties. In this study, we focused on distyrylbenzene derivatives with monofluoroolefin structures, expecting intermolecular H-F interactions in the solid state. UV-vis and fluorescence spectra of the obtained compounds were measured and compared with those of unsubstituted distyrylbenzene. The crystal structures of each compound were determined by single crystal X-ray diffraction and Hirshfeld surface analysis to understand the intermolecular contacts.

Tunable Synthesis of Monofluoroalkenes and Gem-Difluoroalkenes via Solvent-Controlled Rhodium-Catalyzed Arylation of 1-Bromo-2,2-difluoroethylene

Divergent synthesis of fluorine-containing scaffolds starting from a suite of raw materials is an intriguing topic. Herein, we report the solvent-controlled rhodium-catalyzed tunable arylation of 1-bromo-2,2-difluoroethylene. The selection of the reaction solvents provides switchable defluorinated or debrominated arylation from readily available feedstock resources (both arylboronic acids/esters and 1-bromo-2,2-difluoroethylene are commercially available). This switch is feasible because of the difference in coordination ability between the solvent (CH2 Cl2 or CH3 CN) and the rhodium center, resulting in different olefin insertion. This protocol allows the convenient synthesis of monofluoroalkenes and gem-difluoroalkenes, both of which are important scaffolds in the fields of medicine and materials. Moreover, this newly developed solvent-regulated reaction system can be applied to the site-selective dechlorinated arylation of trichloroethylene. Overall, this study provides a useful strategy for the divergent synthesis of fluorine-containing scaffolds and provides insight into the importance of solvent selection in catalytic reactions.

Nickel-Catalyzed Selective C(sp2 )-F Bond Alkylation of Industrially Relevant Hydrofluoroolefin HFO-1234yf

The selective transition-metal catalyzed C-F bond functionalization of inexpensive industrial fluorochemicals represents one of the most attractive approaches to valuable fluorinated compounds. However, the selective C(sp2 )-F bond carbofunctionalization of refrigerant hydrofluoroolefins (HFOs) remains challenging. Here, we report a nickel-catalyzed selective C(sp2 )-F bond alkylation of HFO-1234yf with alkylzinc reagents. The resulting 2-trifluoromethylalkenes can serve as a versatile synthon for diversified transformations, including the anti-Markovnikov type hydroalkylation and the synthesis of bioactive molecule analogues. Mechanistic studies reveal that lithium salt is essential to promote the oxidative addition of Ni0 (Ln ) to the C-F bond; the less electron-rich N-based ligands, such as bipyridine and pyridine-oxazoline, feature comparable or even higher oxidative addition rates than the electron-rich phosphine ligands; the strong σ-donating phosphine ligands, such as PMe3 , are detrimental to transmetallation, but the less electron-rich and bulky N-based ligands, such as pyridine-oxazoline, facilitate transmetallation and reductive elimination to form the final product.

Rhodium-Catalyzed Enantioselective 1,4-Oxyamination of Conjugated gem-Difluorodienes via Coupling with Carboxylic Acids and Dioxazolones

The incorporation of fluorine atoms in organics improves their bioactivity and lipophilicity. Catalytic functionalization of gem-difluorodienes represents one of the most straightforward approaches to access fluorinated alkenes. In contrast to the regular 1,3-dienes that undergo diverse asymmetric di/hydrofunctionalizations, the regio- and enantioselective oxyamination of gem-difluorodienes remains untouched. Herein, we report asymmetric 1,4-oxyamination of gem-difluorodiene by chiral rhodium-catalyzed three-component coupling with readily available carboxylic acid and dioxazolone, affording gem-difluorinated 1,4-amino alcohol derivatives. Our asymmetric protocol exhibits high 1,4-regio- and enantioselectivity with utility in the late-stage modification of pharmaceuticals and natural products. Stoichiometric experiments provide evidences for the π-allylrhodium pathway. Related oxyamination was also realized when trifluoroethanol was used as an oxygen nucleophile.

Stereoselective Palladium-Catalyzed C-F Bond Alkenylation of Tetrasubstituted gem-Difluoroalkenes via Mizoroki-Heck Reaction

A highly diastereoselective Pd(0)-catalyzed Mizoroki-Heck reaction of gem-difluoroalkenes is described. Unlike previously reported C-F bond functionalization with organometallic reagents, this reaction takes place between two different alkenes to achieve a formal C-F and C-H bond cross-coupling via a distinct pathway. Monofluorinated 1,3-diene products can be synthesized with control of the geometry of each alkene and good functional group tolerability.

Copper and Palladium Cocatalyzed Defluorinative Coupling of gem-Difluoroalkenes and Acyl Chloride

A novel copper and palladium cocatalyzed defluorinative coupling of gem-difluoroalkenes and acyl chlorides has been developed. It is a practical method to prepare α-fluorochalcones, which are a kind of important unit in a variety of bioactive compounds. Under mild reaction conditions, a series of substrates with various functional groups could afford desired products smoothly. Further synthetic studies illustrated that the products of this chemistry could be used as versatile precursors to access complicated compounds. Furthermore, the reaction mechanism was proposed based on control experiments.

Anthranilic Diamides Containing Monofluoroalkene Amide Linkers as Potential Insect RyR Activators: Design, Synthesis, Bio-evaluation, and Computational Study

In order to develop anthranilic diamides with novel chemotypes, a series of anthranilic diamides with acrylamide linkers were designed and synthesized. The results of preliminary bioassays indicated that compounds with a monofluoroalkene amide linker (Z-isomer) exhibited good larvicidal activity against lepidopteran pests. The LC₅₀ values of compound A23 against Mythimna separata and Plutella xylostella were 1.44 and 3.48 mg·L^-1, respectively, while those of chlorantraniliprole were 0.08 and 0.06 mg·L^-1, respectively. Compound A23 also exhibited the same level of lethal potency against resistant and susceptible strains of Spodoptera frugiperda at 50 mg·L^-1. Compound A23 exhibited similar symptoms as chlorantraniliprole in test larvae. Comparative molecular field analysis was conducted to demonstrate the structure-activity relationship. Central neuron calcium imaging experiments indicated that monofluoroalkene compounds were potential ryanodine receptor (RyR) activators and activated calcium channels in both the endoplasmic reticulum and the cell membrane. Molecular docking suggested that A23 had a better binding potency to P. xylostella RyR than chlorantraniliprole. The MM|GBSA dG bind value of A23 with P. xylostella RyR was 117.611 kcal·mol^-1. Monofluoroalkene was introduced into anthranilic diamide insecticides for the first time and brought a novel chemotype for insect RyR activators. The feasibility of fluoroalkenes as insecticide fragments was explored.

Chromium-Catalyzed Defluorinative Reductive Coupling of Aldehydes with gem-Difluoroalkenes

Herein, a mild and convenient defluorinative reductive cross coupling of gem-difluoroalkenes with aliphatic aldehydes has been developed to afford diverse silyl-protected β-fluorinated allylic alcohols. The reaction is operationally simple and shows good functional group tolerance with moderate to excellent yields. The utility of this method is demonstrated by converting the products into various bioactive fluorinated compounds, showing its potential applications in drug discovery and biochemistry.

Recent Advances in Alkenyl sp2 C-H and C-F Bond Functionalizations: Scope, Mechanism, and Applications

Alkenes and their derivatives are featured widely in a variety of natural products, pharmaceuticals, and advanced materials. Significant efforts have been made toward the development of new and practical methods to access this important class of compounds by selectively activating the alkenyl C(sp²)-H bonds in recent years. In this comprehensive review, we describe the state-of-the-art strategies for the direct functionalization of alkenyl sp² C-H and C-F bonds until June 2022. Moreover, metal-free, photoredox, and electrochemical strategies are also covered. For clarity, this review has been divided into two parts; the first part focuses on currently available alkenyl sp² C-H functionalization methods using different alkene derivatives as the starting materials, and the second part describes the alkenyl sp² C-F bond functionalization using easily accessible gem-difluoroalkenes as the starting material. This review includes the scope, limitations, mechanistic studies, stereoselective control (using directing groups as well as metal-migration strategies), and their applications to complex molecule synthesis where appropriate. Overall, this comprehensive review aims to document the considerable advancements, current status, and emerging work by critically summarizing the contributions of researchers working in this fascinating area and is expected to stimulate novel, innovative, and broadly applicable strategies for alkenyl sp² C-H and C-F bond functionalizations in the coming years.

Organocatalyzed Controlled Radical Copolymerization toward Hybrid Functional Fluoropolymers Driven by Light

Photo-controlled polymerizations are attractive to tailor macromolecules of complex compositions with spatiotemporal regulation. In this work, with a convenient synthesis for trifluorovinyl boronic ester (TFVB), we report a light-driven organocatalyzed copolymerization of vinyl monomers and TFVB for the first time, which enabled the controlled synthesis of a variety of hybrid fluorine/boron polymers with low dispersities and good chain-end fidelity. The good behaviors of "ON/OFF" switch, chain-extension polymerizations and post-modifications further highlight the versatility and reliability of this copolymerization. Furthermore, we demonstrate that the combination of fluorine and boron could furnish copolymer electrolytes of high lithium-ion transference number (up to 0.83), bringing new opportunities of engineering high-performance materials for energy storage purposes.

Synthesis of remote fluoroalkenyl ketones by photo-induced ring-opening addition of cyclic alkoxy radicals to fluorinated alkenes

Fluoroalkenyl moieties are often used as carbonyl mimics in medicine preparation, and thus the development of facile routes for the synthesis of such compounds is of great importance. In this work, we report a photocatalytic ring-opening addition of cyclic alcohols to α-(trifluoromethyl)styrenes, which underwent a proton-coupled electron transfer and β-scission process, delivering a great variety of remote gem-difluoroalkenyl ketone derivatives. This methodology can also be applied in the reaction of gem-difluorostyrenes and 1,1,2-trifluorostyrenes to access monofluoro- and 1,2-difluoroalkenyl ketones.

Theoretical Insight into the Multiple Roles of LiHMDS in Pd-Catalyzed Borylation of Fluorobenzene

Pd-catalyzed borylation of fluorobenzene was theoretically studied. DFT calculations revealed that the reaction occurs through an unprecedented 3 + 6-membered ring transition state, in which one LiHMDS (HMDS = hexamethyldisilazane) acts as a ligand and another LiHMDS is essential to provide Li···N and Li···F interactions, overcoming the large destabilization of the strong phenyl-F bond distortion. The characteristic feature of LiHMDS was elucidated by comparing it with HMDS and NaHMDS analogues.

Synthesis of gem-Difluorinated 1,3-Dienes via Synergistic Cu/Pd-Catalyzed Borodifluorovinylation of Alkynes

gem-Difluoroalkenes (=CF₂), which normally act as metabolically stable bioisosteres for carbonyl groups (C═O), are widely applied in agrochemicals and pharmaceuticals and are also used as building blocks in organic synthesis. Herein, an example of Cu/Pd-catalyzed borodifluorovinylation was achieved using alkynes, difluoroethylene bromide, and B₂pin₂ as chemical feedstocks, providing the corresponding conjugated gem-difluoroalkene scaffold with good functional group compatibility. Moreover, an array of fluorinated synthons can be obtained through further transformations.

Synergistic Pd/Cu-catalyzed enantioselective Csp2-F bond alkylation of fluoro-1,3-dienes with aldimine esters

Due to high bond dissociation energies of Csp2-F bonds, using fluorinated compounds in Csp2-Csp3 cross-coupling is difficult. Here the authors report a protocol for enantioselective Csp2-Csp3 coupling of dienyl fluorides with aldimine esters, enabled by synergistic copper and palladium catalysis. This reaction represents the first example of asymmetric Csp2-Csp3 cross-coupling involving an inert Csp2-F bond and provides expeditious access to chiral α-alkenyl α-amino acids with high enantioselectivity. Control experiments suggest that the Csp2-F bond activation occurs through a pathway involving PdH migratory insertion and subsequent allylic defluorination, rather than by direct oxidative addition of the Csp2-F bond to Pd(0). The detailed mechanism is further investigated by DFT calculation and the enantioselectivity is rationalized.

Recent Advances in the Construction of Fluorinated Organoboron Compounds

Fluorinated organoboron compounds are important synthetic building blocks that combine the unique characteristics of a fluorinated motif with the versatile synthetic applications of organoboron moiety. This review article guides the research on fluorinated organoboron compounds mainly from four aspects in recent years: selective monodefluoroborylation of polyfluoroarenes and polyfluoroalkenes, selective borylation of fluorinated substrates, selective fluorination of organoboron compounds, and borofluorination of alkynes/olefins. In addition, this review will provide a necessary guidance and inspiration for the research on the valuable synthetic building block fluorinated organoboron compounds.

Stereodefined alkenes with a fluoro-chloro terminus as a uniquely enabling compound class

Trisubstituted alkenyl fluorides are important compounds for drug discovery, agrochemical development and materials science. Despite notable progress, however, many stereochemically defined trisubstituted fluoroalkenes either cannot be prepared efficiently or can only be accessed in one isomeric form. Here we outline a general solution to this problem by first unveiling a practical, widely applicable and catalytic strategy for stereodivergent synthesis of olefins bearing a fluoro-chloro terminus. This has been accomplished by cross-metathesis between two trisubstituted olefins, one of which is a purchasable but scarcely utilized trihaloalkene. Subsequent cross-coupling can then be used to generate an assortment of trisubstituted alkenyl fluorides. The importance of the advance is highlighted by syntheses of, among others, a fluoronematic liquid-crystal component, peptide analogues bearing an E- or a Z-amide bond mimic, and all four stereoisomers of difluororumenic ester (an anti-cancer compound).

Inorganometallics (Transition Metal-Metalloid Complexes) and Catalysis

While the formation and breaking of transition metal (TM)-carbon bonds plays a pivotal role in the catalysis of organic compounds, the reactivity of inorganometallic species, that is, those involving the transition metal (TM)-metalloid (E) bond, is of key importance in most conversions of metalloid derivatives catalyzed by TM complexes. This Review presents the background of inorganometallic catalysis and its development over the last 15 years. The results of mechanistic studies presented in the Review are related to the occurrence of TM-E and TM-H compounds as reactive intermediates in the catalytic transformations of selected metalloids (E = B, Si, Ge, Sn, As, Sb, or Te). The Review illustrates the significance of inorganometallics in catalysis of the following processes: addition of metalloid-hydrogen and metalloid-metalloid bonds to unsaturated compounds; activation and functionalization of C-H bonds and C-X bonds with hydrometalloids and bismetalloids; activation and functionalization of C-H bonds with vinylmetalloids, metalloid halides, and sulfonates; and dehydrocoupling of hydrometalloids. This first Review on inorganometallic catalysis sums up the developments in the catalytic methods for the synthesis of organometalloid compounds and their applications in advanced organic synthesis as a part of tandem reactions.

Competing C-H and C-F bond activation reactions of a fluorinated olefin at Rh: a fluorido vinylidene complex as an intermediate in an unprecedented dehydrofluorination step

The hydrofluoroolefin Z-1,3,3,3-tetrafluoropropene has been activated via an initial C-F bond activation and subsequent C-H bond activation using [Rh(H)(PEt3)3] (1) or via C-H bond activation at [Rh(CH3)(PEt3)3] (8). In both cases the formation of [Rh{(E)-CF[double bond, length as m-dash]CHCF3}(PEt3)3] (3) was observed. Importantly, the C-F activation product [Rh{(E)-CH[double bond, length as m-dash]CHCF3}(PEt3)3] (2) reacts in the presence of Z-1,3,3,3-tetrafluoropropene into 3. The latter converted into [Rh(C[triple bond, length as m-dash]CCF3)(PEt3)3] (6) by an unprecedented dehydrofluorination reaction, presumably via a vinylidene complex as intermediate. When the carbonyl complex [Rh(C[triple bond, length as m-dash]CCF3)(CO)(PEt3)3] (12) was treated with an excess of NEt3·3HF or HBF4 at low temperature, the formation of the phosphonioalkenyl compounds [Rh{(Z)-C(PEt3)[double bond, length as m-dash]CHCF3}(CO)(PEt3)2]X (X = F(HF) x , BF4) (13) was observed. The formation of 13 can be explained by an attack of PEt3 at the electrophilic α-carbon atom of an intermediate vinylidene complex. The employment of PiPr3 derivatives as model compounds allowed for the isolation of the unique fluorido vinylidene complex trans-[Rh(F)([double bond, length as m-dash]C[double bond, length as m-dash]CHCF3)(PiPr3)2] (16), which in the presence of PEt3 transforms into [Rh(C[triple bond, length as m-dash]CCF3)(PEt3)3] (6).

Difunctionalization of gem-Difluoroalkenes via Photoredox Catalysis: Synthesis of Diverse α,α-Difluoromethyl-β-alkoxysulfones

Visible-light-promoted alkoxysulfonylation of gem-difluoroalkenes using sulfonyl chlorides and alcohols has been developed. The reaction exhibits a relatively broad substrate scope with excellent functional group compatibility. This synthesis method includes an atom transfer radical addition-like process. The products can be used as platform molecules for further modification.

Chemo- and regio-divergent access to fluorinated 1-alkyl and 1-acyl triazenes from alkynyl triazenes

The 1,1,2,2-tetrafluoroethylene unit is a prevalent pattern in bioactive molecules and functional materials. Despite being in principle a straightforward strategy to access this motif, the direct tetrafluorination of alkynes involves...

Csp3‒H Monofluoroalkenylation via Stereoselective C‒F Bond Cleavage

A practical nickel- and photoredox-catalyzed Csp3‒H monofluoroalkenylation through chelation-assisted Csp2‒F bond cleavage of gem-difluoroalkenes has been developed, which provides an expedient access to the synthesis of tetrasubstituted fluoroalkenes with complete...

Synthesis of α-trifluoromethyl sulfides through fluorosulfuration of gem-difluoroalkenes

A new fluoro-sulfuration of gem-difluoroalkenes is demonstrated that occurs through a nucleophilic fluorination and subsequent interrupted electrophilic sulfuration cascade.

Synthesis of bioactive fluoropyrrolidines via copper(i)-catalysed asymmetric 1,3-dipolar cycloaddition of azomethine ylides

Chiral pyrrolidinyl units are important building blocks in biologically active natural products and drugs, and the development of efficient methods for the synthesis of diverse structured pyrrolidine derivatives is of great importance. Meanwhile, incorporating fluorine containing groups into small molecules often changes their activities to a great extent due to the special physicochemical properties of fluorine atoms. Herein, we report an efficient route to obtain enantioenriched 3,3-difluoro- and 3,3,4-trifluoropyrrolidinyl derivatives by Cu(i)-catalysed enantioselective 1,3-dipolar cycloaddition of azomethine ylides with less active 1,1-difluoro- and 1,1,2-trifluorostyrenes. A series of new fluorinated pyrrolidines have been prepared in high yields (up to 96%) and with excellent stereoselectivities (up to >20 : 1 dr and 97% ee), and these unique structural blocks could be readily introduced into some natural compounds and pharmaceuticals. Additionally, antifungal activity investigation against four common plant fungi showed that some products possess general and high biological activities; comparison with the low antifungal activities of corresponding nonfluorinated compounds revealed that the fluorine atoms at the pyrrolidinyl rings play a crucial role in the antifungal activity.

Chiral fluoropyrrolidines were synthesized by Cu(i)-catalyzed enantioselective 1,3-dipolar cycloaddition of azomethine ylides with less active fluorinated styrenes, with broad substrate scope and high yield, stereoselectivity and biological activity.

Highly Active Cross-Metathesis of Tetrafluoroethylene with a Seven-Membered N-Heterocyclic-Carbene-Ruthenium Catalyst

A drastic increase in catalyst turnover number (TON) was accomplished in the cross-metathesis of tetrafluoroethylene (TFE) and vinyl ethers. Under a continuous flow of TFE, catalyst Ru7, which contains a seven-membered N-heterocyclic carbene (NHC) ligand, reached a TON of 4100; this is 2 orders of magnitude higher than the highest hitherto reported value. Mechanistic studies revealed that the expanded NHC successfully destabilizes the stable intermediates with a difluorocarbene structure, which strongly promotes the reaction.