Visible-Light-Induced, Copper-Catalyzed Three-Component Coupling of Alkyl Halides, Olefins, and Trifluoromethylthiolate to Generate Trifluoromethyl Thioethers

Overcoming Copper Reduction Limitation in Asymmetric Substitution: Aryl-Radical-Enabled Enantioconvergent Cyanation of Alkyl Iodides

Cu-catalyzed enantioconvergent cross-coupling of alkyl halides has emerged as a powerful strategy for synthesizing enantioenriched molecules. However, this approach is intrinsically limited by the weak reducing power of copper(I) species, which restricts the scope of compatible nucleophiles and necessitates extensive ligand optimization or the use of complex chiral scaffolds. To overcome these challenges, we introduce an aryl-radical-enabled strategy that decouples the alkyl halide activation step from the chiral Cu center. We demonstrate that merging aryl-radical-enabled iodine abstraction with Cu-catalyzed asymmetric radical functionalization enables the conversion of racemic α-iodoamides to enantioenriched alkyl nitrile products with good yield and enantioselectivity. The rational design of chiral ligands identified a new class of carboxamide-containing BOX ligands. Mechanistic studies support an aryl-radical-enabled pathway and the unique hydrogen-bonding ability in the newly designed BOX ligands. This aryl-radical-enabled asymmetric substitution reaction has the potential to significantly expand the scope of Cu-catalyzed enantioconvergent cross-coupling reactions.

Harnessing Bromo/Acyloxy Transposition (BrAcT) and Excited-State Copper Catalysis for Styrene Difunctionalization

1,2-Difunctionalization of styrenes, adding two distinct functional groups across the C═C double bond, has emerged as a powerful tool for enhancing molecular complexity. Herein, we report the development of a regioconvergent β-acyloxylation-α-ketonylation of styrenes through bromo/acyloxy transposition (BrAcT) and excited-state copper catalysis. This approach is amenable to gram-scale synthesis and tolerates a wide range of functional groups and complex molecular frameworks, including derivatives of natural products and marketed drugs. Our experimental and computational studies suggest a unique mechanism featuring a dynamic, ionic BrAcT process and excited-state copper-catalyzed redox reactions. We anticipate that this BrAcT process could serve as a broadly applicable and versatile strategy for β-acyloxylation-α-functionalization of styrenes, creating valuable intermediates for preparing new pharmaceuticals, agrochemicals, and functional materials.

Visible Light-Induced Copper-Catalyzed Regio- and Stereoselective Difluoroalkylthiocyanation of Alkynes

The first regio- and stereoselective difluoroalkylthiocyanation of alkynes with BrCF2R and KSCN has been disclosed under visible light-induced copper catalysis. The copper complex photosensitizer formed in situ not only promotes the generation of CF2-alkyl radicals but also facilitates the construction of C-SCN bonds, allowing the reaction to proceed smoothly without any additional photocatalysts or radical initiators. Moreover, the challenging internal alkynes can also be transformed to deliver CF2-derived tetrasubstituted olefins with potential applications in agricultural and medicinal chemistry.

NIR-II emissive anionic copper nanoclusters with intrinsic photoredox activity in single-electron transfer

Ultrasmall copper nanoclusters have recently emerged as promising photocatalysts for organic synthesis, owing to their exceptional light absorption ability and large surface areas for efficient interactions with substrates. Despite significant advances in cluster-based visible-light photocatalysis, the types of organic transformations that copper nanoclusters can catalyze remain limited to date. Herein, we report a structurally well-defined anionic Cu40 nanocluster that emits in the second near-infrared region (NIR-II, 1000-1700 nm) after photoexcitation and can conduct single-electron transfer with fluoroalkyl iodides without the need for external ligand activation. This photoredox-active copper nanocluster efficiently catalyzes the three-component radical couplings of alkenes, fluoroalkyl iodides, and trimethylsilyl cyanide under blue-LED irradiation at room temperature. A variety of fluorine-containing electrophiles and a cyanide nucleophile can be added onto an array of alkenes, including styrenes and aliphatic olefins. Our current work demonstrates the viability of using readily accessible metal nanoclusters to establish photocatalytic systems with a high degree of practicality and reaction complexity.

Photoinduced decatungstate-catalyzed C(sp3)-H thioetherification by sulfinate salts

Thiols and thioesters play crucial roles in pharmaceuticals, biology, and material science as essential organosulfur compounds. Leveraging readily available and cost-effective inert alkanes through direct thioetherification holds promise for yielding high-value-added products. Herein, we present a photoinduced strategy for sulfur-containing modification of inert alkanes utilizing decatungstate as hydrogen atom transfer reagent, offering a straightforward and practical approach for synthesizing thioethers and thioesters.

Copper-Catalyzed Enantioselective C(sp3 )-SCF3 Coupling of Carbon-Centered Benzyl Radicals with (Me4 N)SCF3

In contrast with the well-established C(sp2 )-SCF3 cross-coupling to forge the Ar-SCF3 bond, the corresponding enantioselective coupling of readily available alkyl electrophiles to forge chiral C(sp3 )-SCF3 bond has remained largely unexplored. We herein disclose a copper-catalyzed enantioselective radical C(sp3 )-SCF3 coupling of a range of secondary/tertiary benzyl radicals with the easily available (Me4 N)SCF3 reagent. The key to the success lies in the utilization of chiral phosphino-oxazoline-derived anionic N,N,P-ligands through tuning electronic and steric effects for the simultaneous control of the reaction initiation and enantioselectivity. This strategy can successfully realize two types of asymmetric radical reactions, including enantioconvergent C(sp3 )-SCF3 cross-coupling of racemic benzyl halides and three-component 1,2-carbotrifluoromethylthiolation of arylated alkenes under mild reaction conditions. It therefore provides a highly flexible platform for the rapid assembly of an array of enantioenriched SCF3 -containing molecules of interest in organic synthesis and medicinal chemistry.

Photoredox/Copper-Catalyzed One-Pot Aminoalkylation/Cyclization of Alkenes with Primary Amines to Synthesize Polysubstituted γ-Lactams

Visible-light-driven chemical transformation has emerged as a powerful tool for the synthesis of γ-lactams. However, during this transformation, the α-bromoimides need to be pre-prepared. Herein, we report a photoreodox/copper-catalyzed one-pot three-component reaction of alkenes with primary amines for the construction of γ-lactams. In this transformation, the orthoquinones were generated via a photocatalytic pathway, followed by attack by Cu-amido complexes and intramolecular cyclization to give the γ-lactams. This method represents a simple synthetic route displaying broad functional group tolerance, including substrates bearing alcohols, ketones, heterocycles, esters, halides, alkynes, nitriles, ethers, etc.

Organophotocatalyzed Mono- and Bis-Alkyl/Difluoroalkylative Thio/Selenocyanation of Alkenes

Organophotocatalyzed three-component 1,2-difluoroacetyl/alkyl/perfluoroalkylative thio/selenocyanation of styrene derivatives under stoichiometric, transition metal-, oxidant-, and additive-free, and mild redox-neutral conditions is reported. Organophotocatalyst 4CzIPN operates the overall radical-polar-crossover mechanistic cycle via initial oxidative luminescence quenching, and the key intermediates were experimentally detected. Selective mono-alkylative thiocyanation of alkenes using dibromoalkanes is also demonstrated. This one-pot synthetic methodology is suitable for primary, secondary, and tertiary alkyl halides and also extended for double alkylative thiocyanation of the dibromoalkanes with excellent yields.

Photoinduced copper-catalyzed selective three-component 1,2-amino oxygenation of 1,3-dienes

This study presents a highly effective method for the photoinduced copper-catalyzed 1,2-amino oxygenation of 1,3-dienes. This synthetic strategy involves the dual roles of a single copper catalyst, which can act as a photosensitizer to generate nitrogen radicals and can also react with allyl radicals via single electron transfer (SET) processes. The method produces a range of quaternary carbon-centered allyl carboxylic esters and tertiary ethers with high yields and excellent regioselectivity under mild reaction conditions.

Photoinduced Copper-Catalyzed Aminoalkylation of Amino-Pendant Olefins

The combination of photo and copper catalysts has emerged as a novel paradigm in organic catalysis, which provides access to the acceleration of chemical synthesis. Herein, we describe an aminoalkylation of amino-dependent olefins with maleimides through a cooperative photo/copper catalytic system. In this report, the strategy allows the generation of a broad complex of functionalized nitrogenous molecules including oxazolidinones, 2-pyrrolidones, imidazolidinones, thiazolidinones, pyridines, and piperidines in the absence of an external photosensitizer and base. The approach is achieved through a photoinduced Cu(I)/Cu(II)/Cu(III) complex species of nitrogen nucleophiles, intermolecular radical addition, and hydrogen atom transfer (HAT) processes. The plausible mechanism is investigated by a series of control experiments and theoretical tests, including radical scavenging experiments, deuterium labeling experiments, ultraviolet-visible absorption, and cyclic voltammetry (CV) tests.

Transition-metal-catalyzed C-H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

The last decade has witnessed the emergence of innovative synthetic tools for the synthesis of fluorinated molecules. Among these approaches, the transition-metal-catalyzed functionalization of various scaffolds with a panel of fluorinated groups (XRF, X = S, Se, O) offered straightforward access to high value-added compounds. This review will highlight the main advances made in the field with the transition-metal-catalyzed functionalization of C(sp2) and C(sp3) centers with SCF3, SeCF3, or OCH2CF3 groups among others, by C-H bond activation. The scope and limitations of these transformations are discussed in this review.

Photoinduced Copper-Catalyzed C(sp3)-P Bond Formation by Coupling of Secondary Phosphines with N-(Acyloxy)phthalimides and N-Fluorocarboxamides

A photoinduced copper-catalyzed C(sp³)-P bond formation has been developed by using N-(acyloxy)phthalimides as radical precursors and secondary phosphine boranes as coupling partners. A variety of alkyl carboxylic acid derivatives can be readily transformed into the corresponding phosphines with high reaction efficiency and structural diversity. Besides, utilizing the 1,5-HAT of the N-centered radical process, the δ C(sp³)-H bond can be coupled with secondary phosphines, which provides a novel method for the regioselective formation of C(sp³)-P bonds.

Coupling of α-bromoamides and unactivated alkenes to form γ-lactams through EDA and photocatalysis

γ-Lactams are prevalent in small-molecule pharmaceuticals and provide useful precursors to highly substituted pyrrolidines. Despite numerous methods for the synthesis of this valuable motif, previous redox approaches to γ-lactam synthesis from α-haloamides and olefins require additional electron withdrawing functionality as well as N-aryl substitution to promote electrophilicity of the intermediate radical and prevent competitive O-nucleophilicity about the amide. Using α-bromo imides and α-olefins, our strategy enables the synthesis of monosubstituted protected γ-lactams in a formal [3 + 2] fashion. These species are poised for further derivatization into more complex heterocyclic scaffolds, complementing existing methods. C-Br bond scission occurs through two complementary approaches, the formation of an electron donor-acceptor complex between the bromoimide and a nitrogenous base which undergoes photoinduced electron transfer, or triplet sensitization with photocatalyst, to furnish an electrophilic carbon-centered radical. The addition of Lewis acids allows for further increased electrophilicity of the intermediate carbon-centered radical, enabling tertiary substituted α-Br-imides to be used as coupling partners as well as internal olefins.

Polydentate hydrazones as multitasking catalysts in visible-light-induced coupling reactions of amines

A Cu/hydrazone catalyst has been applied in the coupling reactions of anilines for the synthesis of diarylamines and azobenzenes. The copper complex that is formed in situ plays a double duty by harnessing photon energy as a photocatalyst and then by catalysing organometallic elementary steps as a transition metal catalyst. By the selection of hydrazones and bases, the reaction selectivity of aniline can be tuned between homo-coupling and its cross-coupling with arylboronic acid, exhibiting the great potential of such hydrazones in organic synthesis.

Synthesis of Ketonylated Carbocycles via Excited-State Copper-Catalyzed Radical Carbo-Aroylation of Unactivated Alkenes

Carbocycles are core skeletons in natural and synthetic organic compounds possessing a wide diversity of important biological activities. Herein, we report the development of an excited-state copper-catalyzed radical carbo-aroylation of unactivated alkenes to synthesize ketonylated tetralins, di- and tetrahydrophenanthrenes, and cyclopentane derivatives. The reaction is operationally simple and features mild reaction conditions that tolerate a broad range of functional groups. Preliminary mechanistic studies suggest a reaction pathway beginning with photoexcitation of [CuI-BINAP]2 and followed by a single electron transfer (SET), radical aroylation of unactivated alkenes, radical cyclization, and re-aromatization, affording the desired ketonylated carbocycles.

Photoactive Copper Complexes: Properties and Applications

Photocatalyzed and photosensitized chemical processes have seen growing interest recently and have become among the most active areas of chemical research, notably due to their applications in fields such as medicine, chemical synthesis, material science or environmental chemistry. Among all homogeneous catalytic systems reported to date, photoactive copper(I) complexes have been shown to be especially attractive, not only as alternative to noble metal complexes, and have been extensively studied and utilized recently. They are at the core of this review article which is divided into two main sections. The first one focuses on an exhaustive and comprehensive overview of the structural, photophysical and electrochemical properties of mononuclear copper(I) complexes, typical examples highlighting the most critical structural parameters and their impact on the properties being presented to enlighten future design of photoactive copper(I) complexes. The second section is devoted to their main areas of application (photoredox catalysis of organic reactions and polymerization, hydrogen production, photoreduction of carbon dioxide and dye-sensitized solar cells), illustrating their progression from early systems to the current state-of-the-art and showcasing how some limitations of photoactive copper(I) complexes can be overcome with their high versatility.

Excited-State Copper-Catalyzed [4 + 1] Annulation Reaction Enables Modular Synthesis of α,β-Unsaturated-γ-Lactams

Synthesis of α,β-unsaturated-γ-lactams continue to attract attention due to the importance of this structural motif in organic chemistry. Herein, we report the development of a visible-light-induced excited-state copper-catalyzed [4 + 1] annulation reaction for the preparation of a wide range of γ-H, -OH, and -OR-substituted α,β-unsaturated-γ-lactams using acrylamides as the 4-atom unit and aroyl chlorides as the 1-atom unit. This modular synthetic protocol features mild reaction conditions, broad substrate scope, and high functional group tolerance. The reaction is amenable to late-stage diversification of complex molecular architectures, including derivatives of marketed drugs. The products of the reaction can serve as versatile building blocks for further derivatization. Preliminary mechanistic studies suggest an inner-sphere catalytic cycle involving photoexcitation of the Cu(BINAP) catalyst, single-electron transfer, and capture of radical intermediates by copper species, followed by reductive elimination or protonation to give the desired γ-functionalized α,β-unsaturated-γ-lactams.

Copper-Catalyzed Multicomponent Reactions of Intramolecular and Intermolecular Thiotrifluoromethylation of Alkenes: Access to CF3-Containing 2-Iminothiazolidines and Isothioureas

A copper-catalyzed multicomponent reaction of secondary amines bearing allyl substitution, isothiocyanates, and Togni reagent II has been developed under Cs₂CO₃ in DCE at 75 °C. An intermolecular multicomponent reaction of thioureas, activated and unactivated alkenes, and Togni reagent II has also been developed under DMAP in acetonitrile at room temperature. These two alkene difunctionalization reactions provide CF₃-containing 2-iminothiazolindines and isothioureas in moderate to excellent yields with broad substrate scope and good functional group tolerance, respectively.

One-Metal/Two-Ligand for Dual Activation Tandem Catalysis: Photoinduced Cu-Catalyzed Anti-hydroboration of Alkynes

A dual catalyst system based on ligand exchange of two diphosphine ligands possessing different properties in a copper complex has been devised to merge metal- and photocatalytic activation modes. This strategy has been applied to the formal anti-hydroboration of activated internal alkynes via a tandem sequence in which Cu/Xantphos catalyzes the B₂pin₂-syn-hydroboration of the alkyne whereas Cu/BINAP serves as a photocatalyst for visible light-mediated isomerization of the resulting alkenyl boronic ester. Photochemical studies by means of UV–vis absorption, steady-state and time-resolved fluorescence, and transient absorption spectroscopy have allowed characterizing the photoactive Cu/BINAP species in the isomerization reaction and its interaction with the intermediate syn-alkenyl boronic ester through energy transfer from the triplet excited state of the copper catalyst. In addition, mechanistic studies shed light into catalyst speciation and the interplay between the two catalytic cycles as critical success factors.

Visible-Light-Driven Organophotocatalyzed Multicomponent Approach for Tandem C(sp3)-H Activation and Alkylation Followed by Trifluoromethylthiolation

A visible-light-driven organophotocatalyzed multicomponent approach has been developed for tandem direct C(sp³)-H activation and alkylation followed by trifluoromethylthiolation in a one-pot operation. We report a completely metal-free, tandem, three-component approach for the difunctionalization of activated alkenes via the photoinduced radical pathway. This protocol allows the formation of two new C(sp³)-C(sp³) and C(sp³)-SCF₃ bonds using a bench-stable, easy-to-handle trifluoromethylthiolating reagent under mild reaction conditions. The generosity of this reaction is shown with a library of C(sp³)-H donors and alkenes derivatives. The reaction conditions can tolerate a wide variety of functional groups. Gram-scale synthesis using environmentally benign and straightforward conditions highlights the synthetic advancement of the methodology. Further functionalization of the final product is also successfully demonstrated.

Copper-photocatalyzed ATRA reactions: concepts, applications, and opportunities

Atom transfer radical addition (ATRA) reactions are linchpin transformations in synthetic chemistry enabling the atom-economic difunctionalization of alkenes. Thereby a rich chemical space can be accessed through smart combinations of simple starting materials. Originally, these reactions required toxic and hazardous radical initiators or harsh thermal activation and thus, the recent resurgence and dramatic evolution of photocatalysis appeared as an attractive complement to catalyze such transformations in a mild and energy-efficient manner. Initially, this technique relied primarily on complexes of precious metals, such as ruthenium or iridium, to absorb the visible light. Hence, copper photocatalysis rapidly developed into a powerful alternative, not just from an economic point of view. Originally considered to be disadvantageous as a pathway for deactivation by quenching their excited state, the dynamic nature of Cu-complexes enables them to undergo facile ligand exchange and thus opens up special opportunities for transformations utilizing their inner-coordination sphere. Moreover, the ability of Cu(II), representing a persistent radical, to capture incipient radicals offers the possibility to access heretofore elusive two-component, but also three-component, ATRA reactions, not feasible with ruthenium or iridium catalysts. In this regard, the idea of using Cu(I)-substrate assemblies as active photocatalysts is an emerging field to achieve such 3-component coupling reactions even under enantioselective control, which is reflected by an increasing number of reports being covered in this review.

Photoredox-catalyzed fluorodifluoroacetylation of alkenes with FSO2CF2CO2Me and Et3N·3HF

Photoredox-catalyzed three-component fluorodifluoroacetylation of aromatic alkenes is reported, which features a wide substrate scope and functional group tolerance. An advantage of the reaction is the use of a nucleophilic fluoride source and a general difluoroacetylation reagent for the fluorodifluoroacetylation of alkenes.

Photoredox Catalysis Mediated by Tungsten(0) Arylisocyanides in 1,2-Difluorobenzene

We have studied the photochemical cyclization of 1-(2-iodobenzyl)-pyrrole (IBP) and 1-(2-bromobenzyl)-pyrrole (BBP) to 5H-pyrrolo[2,1-a]isoindol catalyzed by W(CNDipp)₆ (CNDipp = 2,6-diisopropylphenylisocyanide) in 1,2-difluorobenzene (DFB). Irradiation (445 nm) of W(CNDipp)₆ (5 mol %) in DFB solution converted 78% of IBP (50 mM) to product after 1 h (16 turnovers). Addition of tetra-n-butyl ammonium hexafluorophosphate (TBAPF₆) (0.2 M) to the DFB solution led to rapid photoinduced disappearance of W(CNDipp)₆ but, remarkably, did not inhibit photochemical cyclization of IBP, indicating that IBP cyclization could be driven by a nonluminescent photocatalyst.

Visible Light-Induced Transition Metal Catalysis

In recent years, visible light-induced transition metal catalysis has emerged as a new paradigm in organic photocatalysis, which has led to the discovery of unprecedented transformations as well as the improvement of known reactions. In this subfield of photocatalysis, a transition metal complex serves a double duty by harvesting photon energy and then enabling bond forming/breaking events mostly via a single catalytic cycle, thus contrasting the established dual photocatalysis in which an exogenous photosensitizer is employed. In addition, this approach often synergistically combines catalyst-substrate interaction with photoinduced process, a feature that is uncommon in conventional photoredox chemistry. This Review describes the early development and recent advances of this emerging field.

Excited-State Copper Catalysis for the Synthesis of Heterocycles

Heterocycles are one of the largest groups of organic moieties with significant medicinal, chemical, and industrial applications. Herein, we report the discovery and development of visible-light-induced, synergistic excited-state copper catalysis using a combination of Cu(IPr)I as a catalyst and rac-BINAP as a ligand, which produces more than 10 distinct classes of heterocycles. The reaction tolerates a broad array of functional groups and complex molecular scaffolds, including derivatives of peptides, natural products, and marketed drugs. Preliminary mechanistic investigation suggests in situ generations of [Cu(BINAP)₂ ]⁺ and [Cu(IPr)₂ ]⁺ catalysts that work cooperatively under visible-light irradiation to facilitate catalytic carbo-aroylation of unactivated alkenes, affording a wide range of useful heterocycles.

Visible-light-promoted trifluoromethylselenolation of ortho-hydroxyarylenaminones

Development of an efficient process that employs easy to handle and shelf-stable reagents for the synthesis of trifluoromethylselenylated heterocyclics remains a daunting challenge in organic synthesis. Herein, we report a...

A concise method for cyclic gem-difluoroacyl scaffolds via visible-light-mediated redox-neutral cascade radical cyclization of alkenes

A series of diverse alkenes were engaged in redox-neutral radical tandem cyclization initiated by a CF2 radical precursor via visible-light-induced photocatalysis, affording various cyclic gem-difluoroacyl arenes in good to excellent yields.

Metal-free photocleavage of C(non-acyl)-S bond of thioesters for regioselective pyridylthioesterification of styrenes

Transformation of thioesters via transition-metal-mediated C(acyl)−S bond cleavage is an emerging method to forge C-C and C-heteroatom bonds. Herein, we report the first activation of stronger C(non-acyl)–S bond of thioesters...

A desulphurization strategy for Sonogashira couplings by visible light/copper catalysis

We have developed a new copper-based photocatalyst, [(binap)(tpy)Cu]Cl, and applied it in the visible-light promoted Sonogashira coupling reactions.

Synthesis of unsymmetrical 1,3-substituted-1,3-dihydro-benzimidazolones via copper-catalyzed C–N coupling under visible light

Although photoinduced copper catalysis for carbon–nitrogen (C–N) amine bond formation with alkyl/aryl halides has been developed, the potential of copper photocatalysis for the synthesis of 1,3-substituted benzimidazolones remains mostly unexplored.

Recent advances in visible-light mediated functionalization of olefins and alkynes using copper catalysts

Over the past decade, visible-light photoredox catalysis has blossomed as a powerful strategy and offers a discrete activation mode complementary to thermal controlled reactions. Visible-light-mediated photoredox catalysis also offers exciting...

Visible-Light-Promoted Hydroxydifluoroalkylation of Alkenes Enabled by Electron Donor-Acceptor Complex

A catalyst-free strategy for regioselective hydroxydifluoroalkylation of alkenes with alkyl bromides was developed, affording a series of difluoroalkylated tertiary alcohols in moderate to good yields. This photocatalyst-free protocol shows broad substrate scope under mild conditions. Moreover, mechanistic studies revealed that a newly identified electron donor-acceptor complex is crucial to this transformation.

Recent Advances in Visible-Light-Promoted Copper Catalysis in Organic Reactions

In recent years, visible-light-mediated copper photocatalysis has emerged as an attractive strategy for the diverse construction of basic bonds in an ecologically benign and cost-effective fashion. The intense activity in these areas has been stimulated by the distinctive properties of copper photocatalysts and has led to the rapid development and expansion of their applications. In this review, we focus on a series of significant achievements in the use of copper complexes as standalone photocatalysts in organic reactions to exhibit their high flexibility and potential in synthetic chemistry.

1 Introduction

2 Redox Coupling Reactions

2.1 Carbon–Nitrogen Redox Coupling Reactions

2.2 Carbon–Carbon Redox Coupling Reactions

3 Oxidative Coupling Reactions

4 Difunctionalization of Olefins

5 C–H Bond Functionalization

6 Radical Alkylation of Imines

7 Conclusions and Outlook

Photoredox Catalysis Mediated by Tungsten(0) Arylisocyanides

W(CNAr)₆ (CNAr = arylisocyanide) photoreductants catalyze base-promoted homolytic aromatic substitution (BHAS) of 1-(2-iodobenzyl)-pyrrole in deuterated benzene. Moderate to high efficiencies correlate with W(CNAr)₆ excited-state reduction potentials upon one-photon 445 nm excitation, with 10 mol % loading of the most powerful photoreductants W(CNDipp)₆ (CNDipp = 2,6-diisopropylphenylisocyanide) and W(CNDippPh^OMe3)₆ (CNDippPh^OMe3 = 4-(3,4,5-trimethoxyphenyl)-2,6-diisopropylphenylisocyanide) affording nearly complete conversion. Stern-Volmer quenching experiments indicated that catalysis is triggered by substrate reductive dehalogenation. Taking advantage of the large two-photon absorption (TPA) cross sections of W(CNAr)₆ complexes, we found that photocatalysis can be driven with femtosecond-pulsed 810 nm excitation. For both one- and two-photon excitation, photocatalysis was terminated by the formation of seven-coordinate W^II-diiodo [WI₂(CNAr)₅] complexes. Notably, we discovered that W(CNDipp)₆ can be regenerated by chemical reduction of WI₂(CNDipp)₅ with excess ligand present in solution.

Metallaphotoredox: The Merger of Photoredox and Transition Metal Catalysis

The merger of photoredox catalysis with transition metal catalysis, termed metallaphotoredox catalysis, has become a mainstay in synthetic methodology over the past decade. Metallaphotoredox catalysis has combined the unparalleled capacity of transition metal catalysis for bond formation with the broad utility of photoinduced electron- and energy-transfer processes. Photocatalytic substrate activation has allowed the engagement of simple starting materials in metal-mediated bond-forming processes. Moreover, electron or energy transfer directly with key organometallic intermediates has provided novel activation modes entirely complementary to traditional catalytic platforms. This Review details and contextualizes the advancements in molecule construction brought forth by metallaphotocatalysis.

Visible-light-mediated copper photocatalysis for organic syntheses

Photoredox catalysis has been applied to renewable energy and green chemistry for many years. Ruthenium and iridium, which can be used as photoredox catalysts, are expensive and scarce in nature. Thus, the further development of catalysts based on these transition metals is discouraged. Alternative photocatalysts based on copper complexes are widely investigated, because they are abundant and less expensive. This review discusses the scope and application of photoinduced copper-based catalysis along with recent progress in this field. The special features and mechanisms of copper photocatalysis and highlights of the applications of the copper complexes to photocatalysis are reported. Copper-photocatalyzed reactions, including alkene and alkyne functionalization, organic halide functionalization, and alkyl C-H functionalization that have been reported over the past 5 years, are included.

Recent advances in intermolecular 1,2-difunctionalization of alkenes involving trifluoromethylthiolation

Trifluoromethylthiolative difunctionalization of alkenes, a cheap and abundant feedstock, which installs a trifluoromethylthiol (SCF3) group and another unique functional group across the carbon-carbon double bonds, provides an ideal strategy for the preparation of β-functionalized alkyl trifluoromethyl sulfides and has become a hot topic recently. This review aims to summarize the major progress in this exciting research area, with particular emphasis on the mechanistic aspects of the reaction pathways.

Copper-catalyzed carbo-difluoromethylation of alkenes via radical relay

Organic molecules that contain alkyl-difluoromethyl moieties have received increased attention in medicinal chemistry, but their synthesis in a modular and late-stage fashion remains challenging. We report herein an efficient copper-catalyzed radical relay approach for the carbo-difluoromethylation of alkenes. This approach simultaneously introduces CF2H groups along with complex alkyl or aryl groups into alkenes with regioselectivity opposite to traditional CF2H radical addition. We demonstrate a broad substrate scope and a wide functional group compatibility. This scalable protocol is applied to the late-stage functionalization of complex molecules and the synthesis of CF2H analogues of bioactive molecules. Mechanistic studies and density functional theory calculations suggest a unique ligand effect on the reactivity of the Cu-CF2H species.

Radical-Promoted Distal C-H Functionalization of C(sp3 ) Centers with Fluorinated Moieties

Due to their unique properties, fluorinated scaffolds are pivotal compounds in pharmaceuticals, agrochemicals, and materials science. Over the last years, the development of versatile strategies for the selective synthesis of fluorinated molecules by direct C-H bond functionalization has attracted a lot of attention. In particular, the design of novel transformations based on a radical process was a bottleneck for distal C-H functionalization reactions, offering synthetic solutions for the selective introduction of fluorinated groups. This Minireview highlights the major contributions in this blossoming field. The development of new methodologies for the remote functionalization of aliphatic derivatives with various fluorinated groups based on a 1,5-hydrogen atom transfer process and a β-fragmentation reaction will be showcased and discussed.