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

Water and Air Stable Copper(I) Complexes of Tetracationic Catenane Ligands for Oxidative C-C Cross-Coupling

Aqueous soluble and stable Cu(I) molecular catalysts featuring a catenane ligand composed of two dicationic, mutually repelling but mechanically interlocked macrocycles are reported. The ligand interlocking not only fine-tunes the coordination sphere and kinetically stabilizes the Cu(I) against air oxidation and disproportionation, but also buries the hydrophobic portions of the ligands and prevents their dissociation which are necessary for their good water solubility and a sustained activity. These catenane Cu(I) complexes can catalyze the oxidative C-C coupling of indoles and tetrahydroisoquinolines in water, using H2O2 as a green oxidant with a good substrate scope. The successful use of catenane ligands in exploiting aqueous Cu(I) catalysis thus highlights the many unexplored potential of mechanical bond as a design element for exploring transition metal catalysis under challenging conditions.

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.

Nucleophilic Organocatalyst for Photochemical Carbon Radical Generation via SN2 Substitution

Photochemical generation of radicals is a powerful way to construct various molecules. But most of these methods rely on initiators or the redox properties of radical precursors. Herein, we report a photochemical organic catalyst that reacts with benzyl halide to generate carbon radical via an SN2 pathway. This nucleophilic catalyst can be easily prepared and is bench-stable. The SN2 process does not rely on the redox properties of halides, showing potential synthetic utility. Control experiments and UV-vis spectroscopic analysis indicate that the SN2 substitution adduct is the key intermediate.

Modulating β-Keto-enamine-Based Covalent Organic Frameworks for Photocatalytic Atom-Transfer Radical Addition Reaction

The atom-transfer radical addition (ATRA) reaction simultaneously forges carbon-carbon and carbon-halogen bonds. However, frequently-used photosensitizers such as precious transition metal complexes, or organic dyes have limitations in terms of their potential toxicity and recyclability. Three β-ketoenamine-linked covalent organic frameworks (COFs) from 1,3,5-triformylphloroglucinol and 1,4-phenylenediamines with variable transient photocurrent and photocatalytic activity have been prepared. A COF bearing electron-deficient Cl atoms displayed the highest photocatalytic activity toward the ATRA reaction of polyhalogenated alkanes to give halogenated olefins under visible light at room temperature. This heterogeneous photocatalyst exhibited good functional group tolerance and could be recycled without significant loss of activity.

Revealing the Mechanism of Alcohol Dehydroxylation and C-C Bond Formation through Concerted Catalysis by Ir/Cu Bimetallic Complexes

The density functional theory (DFT) was employed to theoretically investigate the reaction mechanism of alcohol deoxygenation/trifluoromethylation. The substrate alcohol (R1) forms a complex (INT3) by binding with benzoxazole salts (NHCs). Under the influence of the photocatalyst ([IrIII]*) and quinuclidine, the C-H bond in INT3 is activated through either electron transfer-proton transfer (ETPT) or hydrogen atom transfer (HAT) mechanisms, resulting in the cleavage of C-O bonds and generation of deoxyalkyl radicals. The distribution of high-valent and low-valent states in the catalytic cycle of [Ir]-complexes is governed by the redox potential mechanism. Investigation was conducted on the source of hydrogen atom transfer reagents in the HAT reaction process under both optimal and nonoptimal conditions. The results demonstrate distinct reactivity among various radicals involved in the Cu-mediated radical capture process. Further investigations into INT3 activation modes, cycling facilitated by [Ir]-complexes, and understanding the role played by [Cu]-complexes in this reaction system provide a valuable theoretical foundation for comprehending and enhancing Ir/Cu bimetallic cooperative catalysis in alcohol deoxygenation/trifluoromethylation reactions. This provides anticipated theoretical support for future designs of more efficient and rational alcohol deoxygenation reactions.

Photochemical Synthesis of Acyl Fluorides Using Copper-Catalyzed Fluorocarbonylation of Alkyl Iodides

Acyl fluorides are important reagents due to their unique balance between reactivity and stability. Here, we report a copper-catalyzed carbonylative coupling strategy for synthesizing acyl fluorides under photoirradiation. Alkyl iodides were transformed in high yields into acyl fluorides by using a commercially available copper precatalyst (CuBr·SMe2) and a readily available fluoride salt (KF) at ambient temperature and mild CO pressure (6 atm) under blue light irradiation.

Zinc 1,1,2,2-Tetrafluoroethanesulfinate: A Synthetically Useful Oxidative and Photoredox Source of the 1,1,2,2-Tetrafluoroethyl Radical

1,1,2,2-Tetrafluoroethyl-containing molecules are of potential importance in drug discovery, but the efficient synthesis of such compounds is still relatively unexplored due to the lack of readily available reagents for the incorporation of the HCF2CF2 group. Herein, we introduce a new reagent, zinc 1,1,2,2-tetrafluoroethanesulfinate, which can be useful for the oxidative tetrafluoroethylation of arylboronic acids and heteroarenes as well as for a novel photoredox, three component hydro-tetrafluoroethylation of two alkenes of complementary reactivity.

Multiple-cycle photochemical cascade reactions

Cascade reactions represent an efficient and economical synthetic approach, enabling the rapid synthesis of a wide array of structurally complex organic compounds. These compounds, previously inaccessible, can now be synthesized in a remarkably limited number of steps. Concurrently, the photochemical reactions of organic molecules have gained prominence as a potent strategy for accessing a diverse range of radical species and intermediates. This is achieved in a controlled manner under mild conditions. Owing to the relentless endeavors of chemists, significant strides have been made in the realm of photochemical cascade reactions. These advancements have facilitated the synthesis of novel molecular structures with high complexity, structures that are typically challenging to generate under thermal conditions. In this review, we comprehensively summarize and underscore the recent pivotal advancements in visible-light-induced cascade reactions. Our focus is on the elucidation of multiple photochemical catalytic cycles, emphasizing the catalytic activation modes and the types of reactions involved.

Visible-Light-Driven Unsymmetric gem-Difunctionalization of Vinyl Azides with Thiosulfonates or Selenosulfonates

Thiosulfonylation and selenosulfonylation of vinyl azides with thiosulfonates and selenosulfonates were achieved using Cu(dap)2Cl as a photosensitizer under visible-light irradiation. This reaction is the application of a vinyl azide substrate in a group transfer radical addition (GTRA) reaction, through β-difunctionalization, to obtain a variety of unsymmetric difunctionalized N-unprotected enamines.

Regioselective Dearomative Amidoximation of Nonactivated Arenes Enabled by Photohomolytic Cleavage of N-nitrosamides

Dearomative spirocyclization reactions represent a promising means to convert arenes into three-dimensional architectures; however, controlling the regioselectivity of radical dearomatization with nonactivated arenes to afford the spirocyclizative 1,2-difunctionalization other than its kinetically preferred 1,4-difunctionalization is exceptionally challenging. Here we disclose a novel strategy for dearomative 1,2- or 1,4-amidoximation of (hetero)arenes enabled by direct visible-light-induced homolysis of N-NO bonds of nitrosamides, giving rise to various highly regioselective amidoximated spirocycles that previously have been inaccessible or required elaborate synthetic efforts. The mechanism and origins of the observed regioselectivities were investigated by control experiments and density functional theory calculations.

Iron-catalyzed fluoroalkylative alkylsulfonylation of alkenes via radical-anion relay

Transition metal-catalyzed reductive difunctionalization of alkenes with alkyl halides is a powerful method for upgrading commodity chemicals into densely functionalized molecules. However, super stoichiometric amounts of metal reductant and the requirement of installing a directing group into alkenes to suppress the inherent β-H elimination bring great limitations to this type of reaction. We demonstrate herein that the difunctionalization of alkenes with two different alkyl halides is accessible via a radical-anion relay with Na2S2O4 as both reductant and sulfone-source. The Na2S2O4 together with the electron-shuttle catalyst is crucial to divert the mechanistic pathway toward the formation of alkyl sulfone anion instead of the previously reported alkylmetal intermediates. Mechanistic studies allow the identification of carbon-centered alkyl radical and sulfur-centered alkyl sulfone radical, which are in equilibrium via capture or extrusion of SO2 and could be converted to alkyl sulfone anion accelerated by iron electron-shuttle catalysis, leading to the observed high chemoselectivity.

Chemoselective Reactions of Functionalized Sulfonyl Halides

Chemoselective transformations of functionalized sulfonyl fluorides and chlorides are surveyed comprehensively. It is shown that sulfonyl fluorides provide an excellent selectivity control in their reactions. Thus, numerous conditions are tolerated by the SO2 F group - from amide and ester formation to directed ortho-lithiation and transition-metal-catalyzed cross-couplings. Meanwhile, sulfur (VI) fluoride exchange (SuFEx) is also compatible with numerous functional groups, thus confirming its title of "another click reaction". On the contrary, with a few exceptions, most transformations of functionalized sulfonyl chlorides typically occur at the SO2 Cl moiety.

Copper(II)-photocatalyzed Hydrocarboxylation of Schiff bases with CO2: antimicrobial evaluation and in silico studies of Schiff bases and unnatural α-amino acids

We synthesized and characterized two copper(II) complexes: [CuL2Cl]Cl and [CuL'2Cl]Cl, where L = 2,2'-bipyridine and L' = 4,4'-dimethyl-2,2'-bipyridine. We evaluated their photocatalytic hydrocarboxylation properties on a series of synthesized Schiff bases (SBs): (E)-1-(4-((5-bromo-2-hydroxybenzylidene)amino)phenyl)ethanone (SB1), (E)-N-(4-(dimethylamino)benzylidene)benzo[d]thiazol-2-amine (SB2), (E)-4-Bromo-2-((thiazol-2-ylimino)methyl)phenol (SB3), and (E)-4-((5-bromo-2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (SB4). Under mild photocatalytic reaction conditions (room temperature, 1 atm CO2, 30-watt Blue LED light), the derivatives of α-amino acids UAA1-4 were obtained with yields ranging from 5% to 44%. Experimental results demonstrated that [CuL2Cl]Cl exhibited superior photocatalytic efficiency compared to [CuL'2Cl]Cl, attributed to favourable electronic properties. In silico studies revealed strong binding strengths with E. faecalis DHFR (4M7U) for docked Schiff bases (SB) and unnatural α-amino acids (UAAs). In vitro studies further demonstrated significant antimicrobial and antifungal activity for SB2, SB3, and SB4, while none of the synthesized UAAs exhibited such properties, primarily due to the electronic and binding properties of these molecules.Communicated by Ramaswamy H. Sarma.

Visible-Light-Mediated Divergent and Regioselective Vicinal Difunctionalization of Styrenes with Arylazo Sulfones

Activated by visible light, arylazo sulfones can serve as multifaceted reactants and are employed in diazenylation, sulfonylation, and arylation reactions under (photo)catalyst-free conditions. Such versatile reactivity enabled us to develop an operationally simple, regioselective, and tunable difunctionalization of styrenes with arylazo sulfones to produce α-sulfonyl arylhydrazones and 1,2-alkoxyarylated products in moderate to excellent yields. Furthermore, such difunctionalized products have been exploited as key building blocks for the synthesis of various heterocycles.

Asymmetric Photoaerobic Lactonization and Aza-Wacker Cyclization of Alkenes Enabled by Ternary Selenium-Sulfur Multicatalysis

An adaptable, sulfur-accelerated photoaerobic selenium-π-acid ternary catalyst system for the enantioselective allylic redox functionalization of simple, nondirecting alkenes is reported. In contrast to related photoredox catalytic methods, which largely depend on olefinic substrates with heteroatomic directing groups to unfold high degrees of stereoinduction, the current protocol relies on chiral, spirocyclic selenium-π-acids that covalently bind to the alkene moiety. The performance of this ternary catalytic method is demonstrated in the asymmetric, photoaerobic lactonization and cycloamination of enoic acids and unsaturated sulfonamides, respectively, leading to an averaged enantiomeric ratio (er) of 92:8. Notably, this protocol provides for the first time an asymmetric, catalytic entryway to pharmaceutically relevant 3-pyrroline motifs, which was used as a platform to access a 3,4-dihydroxyproline derivative in only seven steps with a 92:8 er.

N-Heterocyclic Carbene and Manganese Synergistic Catalysis: A Three-Component Radical Acylmonofluoroalkylation of Alkenes

Despite the importance of monofluoroalkyl groups in pharmaceutically relevant molecules, catalytic protocols for their incorporation into alkenes remain limited. We describe herein a three-component acylmonofluoroalkylation of alkenes for the introduction of such moieties through an unprecedented cooperativity between the N-heterocyclic carbene catalyst and earth-abundant Mn(II) complex. This general method can be applied to a variety of alkenes, including styrenes, 1,3-enynes, and allenes, as well as complex substrates containing natural product and drug motifs.

Ferrocene catalyzed carbohydroxylation of alkenes using H2O and cycloketone oxime esters

A cyanoalkyl-hydroxylation reaction of aryl alkenes has been successfully devised, employing ferrocene as a catalyst for the addition of a cycloketone oxime ester and H2O across the double bond of the alkene. This environmentally friendly approach employs a solvent mixture consisting of water and demonstrates redox neutrality, along with exceptional regio- and chemoselectivity, leading to the formation of diverse distal hydroxy-nitrile compounds. Moreover, this research presents noteworthy contributions in terms of late-stage functionalization of complex molecules and offers valuable insights into the mechanistic aspects of the reaction.

Selective copper-catalysed atom transfer radical addition (ATRA) in water under environmentally benign conditions

Simple and green conditions for copper-catalysed ATRA reactions in water have been developed. Firstly, [Cu(ADPA)(H2O)(ClO4)2] (1b, ADPA = 9-[(2,2'-dipicolylamino)methyl]anthracene) was demonstrated to be capable of selectively catalysing the ATRA of CCl4 to styrene using L-ascorbic acid (AsH2) as a reducing agent in organic solvent mixtures under ambient atmosphere. Mechanistic investigation suggested that our ATRA reaction proceeded via a single-electron transfer (SET) mechanism through an inner-sphere complex, which is consistent with the widely accepted mechanism for copper-catalysed ATRA. To perform the reaction in water as a sole solvent, a biocompatible surfactant (2 wt% Tween 20 or Tween 80) was added to improve solubility and increase the local concentration of organic reagents and the copper catalyst. Without the need for a complicated oxygen-free set-up, the ATRA reaction catalysed by this simple aqueous-dispersed system can be performed at a mild temperature (60 °C) and a relatively short reaction time (6 h) using 1 mol% of the catalyst. Furthermore, this facile protocol is also applicable for other alkene substrates demonstrated in this work, resulting in satisfactory to excellent substrate conversion and product yields.

Recent Advances in Photochemical Asymmetric Three-Component Reactions

Over the past decades, asymmetric photochemical synthesis has garnered significant attention for its sustainability and unique ability to generate enantio-enriched molecules through distinct reaction pathways. Photochemical asymmetric three-component reactions have demonstrated significant potential for the rapid construction of chiral compounds with molecular diversity and complexity. However, noteworthy challenges persist, including the participation of high-energy intermediates such as radical species, difficulties in precise control of stereoselectivity, and the presence of competing background and side reactions. Recent breakthroughs have led to the development of sophisticated strategies in this field. This review explores the intricate mechanisms, synthetic applications, and limitations of these methods. We anticipate that it will contribute towards advancing asymmetric catalysis, photochemical synthesis, and green chemistry.

Recent Developments on Photochemical Synthesis of 1,n-Dicarbonyls

1,n-dicarbonyls are one of the most fascinating chemical feedstocks finding abundant usage in the field of pharmaceuticals. Besides, they are utilized in a plethora of synthesis in general synthetic organic chemistry. A number of 'conventional' methods are available for their synthesis, such as the Stetter reaction, Baker-Venkatraman rearrangement, oxidation of vicinal diols, and oxidation of deoxybenzoins, synonymous with unfriendly reagents and conditions. In the last 15 years or so, photocatalysis has taken the world of synthetic organic chemistry by a remarkable renaissance. It is fair to say now that everybody loves the light and photoredox chemistry has opened a new gateway to organic chemists towards milder, more simpler alternatives to the previously available methods, allowing access to many sensitive reactions and products. In this review, we present the readers with the photochemical synthesis of a variety of 1,n-dicarbonyls. Diverse photocatalytic pathways to these fascinating molecules have been discussed, placing special emphasis on the mechanisms, giving the reader an opportunity to find all these significant developments in one place.

Unleashing the photocatalytic potential of a noble-metal-free heteroleptic copper complex-based nanomaterial for an enhanced aza-Henry reaction

In this work, we fabricated a versatile and noble metal free copper-based heterogeneous photocatalyst, representing a green shift away from precious group metals such as Ir, Ru, Pt, which have been widely utilized as photocatalysts. The successfully synthesized and characterized copper photocatalyst was employed to establish a cross dehydrogenative coupling via C-H activation between tertiary amines and carbon nucleophiles. The highly efficient copper-based photocatalyst was characterized by numerous physico-chemical techniques, which confirmed its successful formation as well as its high activity. Inductively coupled plasma (ICP-OES) analysis revealed that the composite Cu@Xantphos@ASMNPs had a very high loading of 0.423 mmol g-1 of copper. The magnetic Cu@Xantphos@ASMNPs were utilized as a potential heterogeneous photocatalyst for the very facile and regioselective conversion of aryl tetrahydroqinoline to the respective nitroalkyl aryl tetrahydroisoquinoline in high yield using air as an oxidant and methanol as a green solvent with irradiation with visible light under mild reaction conditions. Additionally, the catalyst shows exceptional chemical stability and reusability without any agglomeration even after several cycles of use, which is one of the key features of this material, rendering it a potential candidate from economic and environmental perspectives.

Emerging Trends in Copper-Promoted Radical-Involved C-O Bond Formations

The C-O bond is ubiquitous in biologically active molecules, pharmaceutical agents, and functional materials, thereby making it an important functional group. Consequently, the development of C-O bond-forming reactions using catalytic strategies has become an increasingly important research topic in organic synthesis because more conventional methods involving strong base and acid have many limitations. In contrast to the ionic-pathway-based methods, copper-promoted radical-mediated C-O bond formation is experiencing a surge in research interest owing to a renaissance in free-radical chemistry and photoredox catalysis. This Perspective highlights and appraises state-of-the-art techniques in this burgeoning research field. The contents are organized according to the different reaction types and working models.

Merging Cu(I) and Cu(II) Photocatalysis: Development of a Versatile Oxohalogenation Protocol for the Sequential Cu(II)/Cu(I)-Catalyzed Oxoallylation of Vinylarenes

A sequential photocatalytic strategy is developed via the merger of Cu(II)/Cu(I)-catalytic cycles for the oxoallylation of vinyl arenes via α-haloketones. The initial Cu(II)-photocatalyzed oxohalogenation exploits ligand-to-metal charge transfer (LMCT) to generate halide radicals from acyl halides utilizing air as a terminal oxidant and can be employed for the late-stage modification of pharmaceuticals and agrochemicals. α-Bromoketones obtained this way can be subsequently subjected to a one-pot Cu(I)-photocatalyzed allylation. This sequential photocatalysis proceeds in a highly regio- and chemoselective fashion and is inconsequential to the electronic nature of styrenes.

Visible-Light-Induced Synthesis of Branched Ethers via Multicomponent Reactions

The Spin-Center Shift (SCS) elimination is a specific way for the generation of radicals with relevance in synthetic and biochemical pathways. The combination of SCS-mediated radical chemistry and atom-transfer radical addition (ATRA) offers new directions in diversity-oriented chemical synthesis. Herein, we report a photoredox three-component reaction of α-acyloxy-N-heterocycles as radical precursors, styrene derivatives as radical trapping agents, and alcohols as nucleophilic quenchers. The novel radical-polar crossover reaction provides access to a diverse set of branched ethers possessing high structural complexity. The utility of the transformation was also demonstrated by the synthesis of a complex drug derivative and it was easily scalable to the multigram level. The scope and limitations were also explored and a plausible mechanism was proposed.

Copper-mediated bromine atom transfer radical cyclisation of unactivated alkyl bromides

The atom transfer radical cyclisation of unactivated alkyl bromides was realized by using a catalytic system of CuBr and Me₆-TREN. This protocol is applicable to the preparation of five-membered rings from unsaturated primary and secondary bromides.

Photoinduced Copper-Catalyzed Late-Stage Azidoarylation of Alkenes via Arylthianthrenium Salts

The arylethylamine pharmacophore is conserved across a range of biologically active natural products and pharmaceuticals, particularly in molecules that act on the central nervous system. Herein, we present a photoinduced copper-catalyzed azidoarylation of alkenes at a late stage with arylthianthrenium salts, allowing access to highly functionalized acyclic (hetero)arylethylamine scaffolds that are otherwise difficult to access. A mechanistic study is consistent with a rac-BINAP-Cu^I-azide (2) as the photoactive catalytic species. We show the utility of the new method by the expedient synthesis of racemic melphalan in four steps through C-H functionalization.

Light-Mediated Synthesis of Aliphatic Anhydrides by Cu-Catalyzed Carbonylation of Alkyl Halides

Acid anhydrides are valuable in the chemical industry for their role in synthesizing polymers, pharmaceuticals, and other commodities, but their syntheses often involve multiple steps with precious metal catalysts. The simplest anhydride, acetic anhydride, is currently produced by two Rh-catalyzed carbonylation reactions on a bulk scale for its use in synthesizing products ranging from aspirin to cellulose acetate. Here, we report a light-mediated, Cu-catalyzed process for producing aliphatic, symmetric acid anhydrides directly by carbonylation of alkyl (pseudo)halides in a single step without any precious metal additives. The transformation requires only simple Cu salts and abundant bases to generate a heterogeneous Cu⁰ photocatalyst in situ, maintains high efficiency and selectivity upon scale-up, and operates by a radical mechanism with several beneficial features. This discovery will enable the engineering of bulk processes for producing commodity anhydrides efficiently and sustainably.

Photochemical and Atom-Economical Sulfonylimination of Alkenes with Bifunctional N-Sulfonyl Ketimine

An organo-photocatalytic sulfonylimination of alkenes was developed by employing readily available N-sulfonyl ketimines as bifunctional reagents. This transformation, featuring prominent functional group tolerance, provides a direct and atom-economic approach for the synthesis of valuable β-amino sulfone derivatives as a single regioisomer. In addition to terminal alkenes, internal alkenes participate in this reaction with high diastereoselectivity. N-Sulfonyl ketimines with aryl or alkyl substituents were found to be compatible with this reaction condition. This method could be applied in the late-stage modifications of drugs. Additionally, a formal insertion of alkene into cyclic sulfonyl imine was observed, affording a ring expansion product.

Copper(I) Photocatalyzed Bromonitroalkylation of Olefins: Evidence for Highly Efficient Inner-Sphere Pathways

We report the visible light-mediated copper-catalyzed vicinal difunctionalization of olefins utilizing bromonitroalkanes as ATRA reagents. This protocol is characterized by high yields and fast reaction times under environmentally benign reaction conditions with exceptional scope, allowing the rapid functionalization of both activated and unactivated olefins. Moreover, late-stage functionnalization of biologically active molecules and upscaling to gram quantities is demonstrated, which offers manifold possibilities for further transformations, e.g. access to nitro- and aminocyclopropanes. Besides the synthetic utility of the title transformation, this study undergirds the exclusive role of copper in photoredox catalysis showing its ability to stabilize and interact with radical intermediates in its coordination sphere. EPR studies suggest that such interactions can even outperform a highly favorable cyclization of transient to persistent radicals contrasting iridium-based photocatalysts.

Photocatalyst-free visible light driven synthesis of gem-dihaloenones from alkynes, tetrahalomethanes and water

Photocatalytic reactions, in particular, processes without photosensitisers, have attracted increased attention due to their green aspect and high economic value and are considered valuable tools in organic synthesis. A new practical photocatalytic system was investigated in this study, and it can efficiently produce gem-dihaloenones by combining terminal alkynes with tetrahalomethanes (BrCCl₃ and CBr₄) and water without a photocatalyst, and the yield can reach up to 87%. The catalytic system is straightforward, the raw materials are inexpensive and easy to obtain, and the operation is simple.

Theoretical Study of Atom-Transfer Radical Addition Reactions between Perfluoroalkyl Iodides and Styrene Using a Copper Photoredox Catalyst

The reaction mechanism of atom-transfer radical addition (ATRA) reactions of perfluoroalkyl iodides with styrene using a Cu(I) photoredox catalyst was analyzed using density functional theory calculations. From among four previously mentioned mechanisms, the ligand-transfer mechanism (ligand abstraction by the radical intermediate) was shown to be most plausible. It was also suggested that the ATRA product would also be reduced by the photoexcited Cu(I) complex.

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.

Divergent and Synergistic Photocatalysis: Hydro- and Oxoalkylation of Vinyl Arenes for the Stereoselective Synthesis of Cyclopentanols via a Formal [4+1]-Annulation of 1,3-Dicarbonyls

The controllable divergent reactivity of 1,3-dicarbonyls is described, which enables the efficient hydro- and oxoalkylation of vinyl arenes. Both reaction pathways are initiated through the formation of polarity-reversed C-centered-radical intermediates at the active methylene center of 1,3-dicarbonyls via direct photocatalytic C–H bond transformations. The oxoalkylation of alkenes is achieved under aerobic conditions via a Cu(II)-photomediated rebound mechanism, while the corresponding hydroalkylation becomes possible under a nitrogen atmosphere by the combination of 4CzIPN and a Brønsted base. The breadth of these divergent protocols is demonstrated in the late-stage modification of drugs and natural products and by the transformation of the products to a variety of heterocycles such as pyridines, pyrroles, or furans. Moreover, the two catalytic modes can be combined synergistically for the stereoselective construction of cyclopentanol derivatives in a formal [4+1]-annulation process.