Tetrachlorophthalimides as Organocatalytic Acceptors for Electron Donor-Acceptor Complex Photoactivation

Unveiling Heavier Dihydropyridine Chalcogenol Esters in Metallaphotoredox Catalyst-Enabled Regioselective Hydrothio(seleno)carbonylation

Herein, aromaticity-driven thio(seleno)ester group transfer from novel 1,4-dihydropyridine thio(seleno)esters to alkene feedstocks is disclosed by merging palladium and photoredox catalysis. In this process, photoactivation of dihydropyridine thio(seleno)esters is integrated with regioselective hydrometalation of alkenes, avoiding photoinduced Pd-C bond homolysis of organopalladium intermediates. Additionally, a regioselective hydroselenocarbonylation of an alkene is accomplished for the first time using a bench-stable selenoester reagent. The activation mode of novel dihydropyridine thioesters has been illustrated by detailed mechanistic studies, spectroscopic analysis, intermediate trapping, and isotope labeling experiments.

Enhancing Electron Donor-Acceptor Complex Photoactivation with a Stable Perylene Diimide Metal-Organic Framework

Electron donor-acceptor complexes are commonly employed to facilitate photoinduced radical-mediated organic reactions. However, achieving these photochemical processes with catalytic amounts of donors or acceptors can be challenging, especially when aiming to reduce catalyst loadings. Herein, we have unveiled a framework-based heterogenization approach that significantly enhances the photoredox activity of perylene diimide species in radical addition reactions with alkyl silicates by promoting faster and more efficient electron donor-acceptor complex formation. Besides offering broad substrate scope in alkene hydroalkylation, the newly developed heterogeneous photocatalysis substantially improves the catalyst turnover numbers in comparison to previous homogeneous photocatalytic systems and demonstrates outstanding catalyst recyclability. These research findings pave the way for the advancement of various efficient and practical organic transformations using framework-supported organocatalysts.

Heterocoupling Two Similar Benzyl Radicals by Dual Photoredox/Cobalt Catalysis

Transition-metal-regulated radical cross coupling enables the selective bonding of two distinct transient radicals, whereas the catalytic method for sorting two almost identical transient radicals, especially similar benzyl radicals, is still rare. Herein, we show that leveraging dual photoredox/cobalt catalysis can selectively couple two similar benzyl radicals. Using easily accessible methylarenes and phenylacetates (benzyl N-hydroxyphthalimide (NHPI) esters) as benzyl radical sources, a range of unsymmetrical 1,2-diarylethane classes via the 1°-1°, 1°-2°, 1°-3°, 2°-2°, 2°-3° and 3°-3° couplings were obtained with broad functional group tolerance. Besides the photochemical continuous flow synthesis, the one-pot procedure that directly uses phenylacetic acids and NHPI as the starting materials to avoid the pre-preparation of benzyl NHPI esters for the gram-scale synthesis is also feasible and affords good yields, showcasing the synthetic utility of our protocol.

Photocatalytic CeCl3-Promoted C-H Alkenylation and Alkynylation of Alkanes

The reemerging field of photoredox catalysis offers numerous advantages towards the development of novel, sustainable and easy-to-execute organic transformations. Herein, we report a light-triggered application of cerium complexes towards the C-H alkenylation and alkynylation of alkanes. An indirect HAT-mediated photocatalytic protocol was developed, using a cerium salt (CeCl3 ⋅ 7H2O) and a chlorine source (TBACl) as the catalytic system. A variety of cyclic and linear hydrocarbons were utilized, delivering the corresponding alkenylation or alkynylation products in good to high yields, displaying high regioselectivity. A series of mechanistic experiments were conducted.

Generation of Triplet States by Host-Stabilized Through-Space Conjugation for the Construction of Efficient Supramolecular Photocatalysts

Promoting the generation of triplet states is essential for developing efficient photocatalytic systems. This research presents a novel approach of host-stabilized through-space conjugation via the combination of covalent and non-covalent methods. The designed building block, 4,4'-(1,4(1,4)-dibenzene cyclohexaphane-1,4-diyl)bis(1-phenylpyridinium) chloride, features inherently stable through-space conjugation. When this block forms a 1 : 1 host-guest complex with cucurbit[8]uril, the through-space conjugation is further stabilized within the confined cavity. Both the generation and lifetime of triplet state are significantly increased, resulting from the host-stabilized through-space conjugation. Additionally, the ultrahigh binding constant of 6.58×1014 M-1 ensures the persistence of host-stabilization effect. As a result, the host-guest complex acts as a highly efficient catalyst in the photocatalytic oxidation of thioether and aromatic alcohol. In the photodegradation of lignin, a complex natural product, the host-guest complex also exhibits high efficiency, demonstrating its robustness. This line of research is anticipated to enrich the toolbox of supramolecular photochemistry and provide a strategy for fabricating efficient supramolecular photocatalysts.

C(sp2)-Arylsulfones Directly from Arylsulfonyl Chlorides with Boronic Acids by Photoactivation of Boosted EDA Complexes

Directly with arylsulfonyl chlorides, a green and efficient deborylativesulfonylation of aryl(alkenyl)boronic acids has been developed to access both diarylsulfones and vinylarylsulfones in moderate to excellent yields at room temperature under visible-light irradiation. This protocol features broad C(sp2)-arylsulfone applicability, simple operation, accessibility of raw materials and ease of scale-up. The key to the success of this photoredox transformation is introducing catalytic amounts of additives, naphthalen-2-ols, thus boosting the formed electron donor-acceptor (EDA) complexes, which can dramatically improve not only the reaction efficiency but also the selectivity. This strategy was inspired and derived from specific substrates, representing a rare paradigm of how to exploit a more general reaction system. Moreover, extensive control experiments provide insights into the proposed mechanism.

Photoinduced Electron Donor Acceptor Complex-Enabled α-C(sp3)-H Alkenylation of Amines

Allylic amines are prevalent and vital structural components present in many bioactive compounds and natural products. Additionally, they serve as valuable intermediates and building blocks, with wide-ranging applications in organic synthesis. However, direct α-C(sp3)-H alkenylation of feedstock amines, particularly for the preparation of α-alkenylated cyclic amines, has posed a longstanding challenge. Herein, we present a general, mild, operationally simple, and transition-metal-free α-alkenylation of various readily available amines with alkenylborate esters in excellent E/Z - and diastereoselectivities. This method features good compatibility with water and oxygen, broad substrate scope, and excellent functional group tolerance, thereby enabling the late-stage modification of various complex molecules. Mechanistic studies suggest that the formation of a photoactive electron donor-acceptor complex between 2-iodobenzamide and the tetraalkoxyborate anion, which subsequently undergoes photoinduced single electron transfer and intramolecular 1,5-hydrogen atom transfer to generate the crucial α-amino radicals, is the key to success of this chemistry.

Catalytic Generation of Pyridyl Radicals via Electron Donor-Acceptor Complex Photoexcitation: Synthesis of 2-Pyridylindole-Based Heterobiaryls

We report the catalytic generation of pyridyl radicals through photoexcitation of the electron donor-acceptor (EDA) complex, which enables the C2-selective heteroarylation of indole under ambient conditions. In this manifold, catalytic triarylamine and chloropyridine aggregate into an EDA complex in the presence of an inorganic base, making readily available chloropyridines good precursors for the generation of diverse pyridyl radicals. Given the broad reaction scope, this catalytic EDA complex protocol provides robust access to heterobiaryl scaffolds that are widely present in biologically important molecules.

Arylcyanation of Styrenes by Photoactive Electron Donor-Acceptor Complexes/Copper Catalysis

A novel electron donor-acceptor (EDA) complex/copper catalysis model has been proposed for the construction of 2,3-diarylpropionitriles under visible light conditions. The developed protocol proceeds via intermolecular charge transfer between the photoactive EDA complex of dibutamine (DBA), aryl thianthrenium salts, and trimethylsilyl cyanide (TMSCN), followed by a copper catalytic cycle. UV-vis absorption measurements confirm the participation of EDA complexes as reactive intermediates. This three-component process proceeds smoothly in the presence of pharmaceutically relevant core structures and sensitive functional groups, which offers the possibility of the precise editing of drug molecules with important scaffolds.

Biomimetic Photoexcited Cobaloxime Catalysis in Organic Synthesis

Drawing inspiration from nature has long been a cornerstone of chemical innovation, with natural systems offering a wealth of untapped potential for discovery. In this minireview, we delve into the burgeoning field of cobaloxime catalysis in organic synthesis, which mimics the catalytic activity of the natural organometallic alkylcobalamine enzymes. Our focus lies on elucidating the latest advancements in this area, as well as delineating the primary mechanistic pathways at play. By describing, and comparing these mechanisms, we provide a comprehensive overview of the current state-of-the-art, while also shedding light on the key unresolved challenges that await further exploration.

Development of an Easy-To-Handle Redox Active Group for Alcohols: Catalytic Transformation of Tertiary Alcohols to Nitriles

The generation of radical intermediates via SET-mediated deoxygenation of activated alcohol derivatives is desirable, as alcohols can be utilized in various radical-mediated reactions. Herein, we introduce α-N-phthalimido-oxy isobutyrate (NPIB) as a novel activating group for alcohols. Essentially, it is a more chemically robust alternative to Overman's N-phthalimidoyl oxalate group. The utility of the NPIB group is showcased in the conversion of tertiary alcohols to nitriles under Ir/Cu dual catalysts and in the presence of TMSCN upon blue LED irradiation. With our newly developed NPIB handle, the reactivities of N-hydroxyphthalimide esters derived from carboxylic acids would be achievable with naturally and commercially more abundant alcohol substrates.

Decyanative Heteroarylations of Glycine Derivatives

Amino acids and aromatic nitrogen heterocycles are widely used in pharmaceuticals. Herein, we present an effective visible-light-driven thiobenzoic acid (TBA)-catalyzed decyanative C(sp3)-H heteroarylation of glycine derivatives. This process occurs under mild and straightforward conditions, affording a range of valuable yet challenging-to-obtain α-heteroaryl amino acid derivatives. Moreover, this organocatalytic C(sp3)-C(sp2) bond formation reaction is applicable to the late-stage modification of various short peptides.

Photoreduction of Trifluoromethyl Group: Lithium Ion Assisted Fluoride-Coupled Electron Transfer from EDA Complex

Photoinduced single-electron reduction is an efficient method for the mono-selective activation of the C-F bond on a trifluoromethyl group to construct a difluoroalkyl group. We have developed an electron-donor-acceptor (EDA) complex mediated single-electron transfer (EDA-SET) of α,α,α-trifluoromethyl arenes in the presence of lithium salt to give α,α-difluoroalkylarenes. The C-F bond reduction was realized by lithium iodide and triethylamine, two common feedstock reagents. Mechanistic studies revealed the generation of a α,α-difluoromethyl radical by single-electron reduction and defluorination, followed by the radical addition to alkenes. Lithium salt interacted with the fluorine atom to promote the photoinduced reduction mediated by the EDA complex. Computational studies indicated that the lithium-assisted defluorination and the single-electron reduction occurred concertedly. We call this phenomenon fluoride-coupled electron transfer (FCET). FCET is a novel approach to C-F bond activation for the synthesis of organofluorine compounds.

Acetone Serving as a Solvent and Interaction Partner Promotes the Direct Olefination of N-Tosylhydrazones under Visible Light

The photochemistry of noncovalent interactions to promote organic transformations is an emerging approach to providing fresh opportunities in synthetic chemistry. Generally, the external substance is necessary to add as an interaction partner, thereby sacrificing the atom economy of the reaction. Herein, we describe a catalyst-free and noncovalent interaction-mediated strategy to access the olefination of N-tosylhydrazones using acetone as a solvent and an interaction partner. This protocol also features broad substrate scope, excellent functional group compatibility, and mild reaction conditions without transition metals. Moreover, the gram-scale synthesis of olefins and the generation of pharmaceutical intermediates highlighted its practical applicability. Lastly, mechanistic studies indicate that the reaction was initiated via noncovalent interactions between acetone and N-tosylhydrazone anion, which is also supported by density functional theory calculations.

3-Chloropropylbis(catecholato)silicate as a Bifunctional Reagent for the One-Pot Synthesis of Tetrahydroquinolines from o-Bromosulfonamides

Bis(catecholato)silicate salts are easily accessible reagents that can be used to install alkyl fragments through photoredox-enabled cross-coupling. These reagents can incorporate various functional groups including pendant alkyl halides. A halogenated organosilicate reagent was leveraged to develop a one-pot synthesis of tetrahydroquinolines from o-bromosulfonamides, where the bifunctional reagent participates in a nickel/photoredox cross-coupling followed by intramolecular nucleophilic substitution. The functional group tolerance of this cross-coupling strategy allowed for the preparation of a series of substituted tetrahydroquinolines.

Dioxygen compatible electron donor-acceptor catalytic system and its enabled aerobic oxygenation

The photochemical properties of Electron Donor-Acceptor (EDA) complexes present exciting opportunities for synthetic chemistry. However, these strategies often require an inert atmosphere to maintain high efficiency. Herein, we develop an EDA complex photocatalytic system through rational design, which overcomes the oxygen-sensitive limitation of traditional EDA photocatalytic systems and enables aerobic oxygenation reactions through dioxygen activation. The mild oxidation system transfers electrons from the donor to the effective catalytic acceptor upon visible light irradiation, which are subsequently captured by molecular oxygen to form the superoxide radical ion, as demonstrated by the specific fluorescent probe, dihydroethidine (DHE). Furthermore, this visible-light mediated oxidative EDA protocol is successfully applied in the aerobic oxygenation of boronic acids. We believe that this photochemical dioxygen activation strategy enabled by EDA complex not only provides a practical approach to aerobic oxygenation but also promotes the design and application of EDA photocatalysis under ambient conditions.

Characterization of A π-π stacking cocrystal of 4-nitrophthalonitrile directed toward application in photocatalysis

Photoexcitation of the electron-donor-acceptor complexes have been an effective approach to achieve radicals by triggering electron transfer. However, the catalytic version of electron-donor-acceptor complex photoactivation is quite underdeveloped comparing to the well-established utilization of electronically biased partners. In this work, we utilize 4-nitrophthalonitrile as an electron acceptor to facilitate the efficient π-stacking with electron-rich aromatics to form electron-donor-acceptor complex. The characterization and energy profiles on the cocrystal of 4-nitrophthalonitrile and 1,3,5-trimethoxybenzene disclose that the electron transfer is highly favorable under the light irradiation. This electron acceptor catalyst can be efficiently applied in the benzylic C-H bond photoactivation by developing the Giese reaction of alkylanisoles and the oxidation of the benzyl alcohols. A broad scope of electron-rich aromatics can be tolerated and a mechanism is also proposed. Moreover, the corresponding π-anion interaction of 4-nitrophthalonitrile with potassium formate can further facilitate the hydrocarboxylation of alkenes efficiently.

An Expanded EDA Complex Profile: Construction of Aza-arenes and Their Synthetic Application as Fluorescence Probes

We developed a visible-light-driven expanded EDA complex profile for the synthesis of aza-arenes via aza-6π electrocyclization of 2-styrylanilines with aromatic aldehydes. This protocol relies on the EDA complexes of AlCl3 with imine to induce the absorption red-shift to visible light from ultraviolet light. An array of 2,3-disubstituted quinolines were constructed smoothly after excitation with blue-light-emitting diodes at room temperature. In addition, the resultant product, used as a cell permeable lipid droplet-specific probe, shows a low working concentration, a short staining time, and functionality in living and fixed cells.

Catalytic π-π Interactions Triggered Photoinduced Synthesis of Biaryls

A highly regioselective photocatalytic method to access a variety of biaryl motifs under metal-free conditions has been developed. The organophotocatalyst is involved in π-π stacking interactions with the alkyne species, which promotes this photocatalytic process with thiophene. Mechanistic studies have shed light on these interactions and the overall process. Along with a broad functional-group tolerance and excellent regioselectivity, this protocol has been utilized in the late-stage functionalization of pharmaceuticals and other natural products.

Photoinduced Direct Electron Transfer between Quinoxalin-2(1H)-ones and Alkyl Carboxylic Acids for C-H Alkylation

The progress of efficient and sustainable approaches for decarboxylative coupling reactions is synthetically appealing due to the structural diversity, lack of toxicity, and widespread commercial accessibility of carboxylic acids. However, the decarboxylation reaction still encounters challenges related to the utilization of oxidants, catalysts, and prefunctionalization conditions. We report herein a mild method that facilitates direct electron transfer between alkyl carboxylic acids and excited-state substrates for C-H alkylation of quinoxalin-2(1H)-ones without the involvement of any catalyst or additive.

Photo-induced imino functionalizations of alkenes via intermolecular charge transfer

A catalyst-free photosensitized strategy has been developed for regioselective imino functionalizations of alkenes via the formation of an EDA complex. This photo-induced protocol facilitates the construction of structurally diverse β-imino sulfones and vinyl sulfones in moderate to high yields. Mechanistic studies reveal that the reaction is initiated with an intermolecular charge transfer between oximes and sulfinates, followed by fragmentation to generate a persistent iminyl radical and transient sulfonyl radical. This catalyst-free protocol also features excellent regioselectivity, broad functional group tolerance and mild reaction conditions. The late stage functionalization of natural product derived compounds and total synthesis of some bioactive molecules have been demonstrated to highlight the utility of this protocol. Meanwhile, the compatibility of different donors has proved the generality of this strategy.

EDA Photochemistry: Mechanistic Investigations and Future Opportunities

Recently, organic synthesis has seen a renaissance in radical chemistry due to the accessibility of mild methods for radical generation using visible light. While renewed interest in synthetic radical chemistry has been driven by the advent of photoredox catalysis, a resurgence of electron donor-acceptor (EDA) photochemistry has also led to many new radical transformations. Similar to photoredox catalysis, EDA photochemistry involves light-promoted single-electron transfer pathways. However, the mechanism of electron transfer in EDA systems is unique wherein the lifetimes of radical intermediates are often shorter due to competitive back-electron transfer. Distinguishing between EDA and photoredox mechanisms can be challenging since they can form identical products. In this perspective, we seek to provide insight on the mechanistic studies which can distinguish between EDA and photoredox manifolds. Additionally, we highlight some key challenges in EDA photochemistry and suggest future goals which could advance the synthetic potential of this field of research.

Difluoroalkylation of Anilines via Photoinduced Methods

The development of sustainable and mild protocols for the fluoroalkylation of organic backbones is of current interest in chemical organic synthesis. Herein, we present operationally simple and practical transition-metal-free methods for the preparation of difluoroalkyl anilines. First, a visible-light organophotocatalytic system working via oxidative quenching is described, providing access to a wide range of difluoroalkyl anilines under mild conditions. In addition, the formation of an unprecedented electron donor-acceptor (EDA) complex between anilines and ethyl difluoroiodoacetate is reported and exploited as an alternative, efficient, and straightforward strategy to prepare difluoroalkyl derivatives.

Sulfonium Salts as Acceptors in Electron Donor-Acceptor Complexes

The photoactivation of electron donor-acceptor complexes has emerged as a sustainable, selective and versatile strategy for the generation of radical species. Electron donor-acceptor (EDA) complexation, however, imposes electronic constraints on the donor and acceptor components and this can limit the range of radicals that can be generated using the approach. New EDA complexation strategies exploiting sulfonium salts allow radicals to be generated from native functionality. For example, aryl sulfonium salts, formed by the activation of arenes, can serve as the acceptor components in EDA complexes due to their electron-deficient nature. This "sulfonium tag" approach relaxes the electronic constraints on the parent substrate and dramatically expands the range of radicals that can be generated using EDA complexation. In this review, these new applications of sulfonium salts will be introduced and the areas of chemical space rendered accessible through this innovation will be highlighted.

Visible-light-driven oxidation of organosilanes by a charge-transfer complex

Direct oxidation of organosilanes is one of the most straightforward ways to access silanols. Herein, we describe a novel photo-induced strategy for oxidation of organosilanes to access silanols, promoted by a photoactive charge-transfer complex (CTC) between sodium benzenesulfinate and molecular O₂. A streamlined sequence transformation of organosilanes to silyl ethers was also readily achieved. This developed protocol represents the first example of CTC-based oxidation of organosilanes, offering a facile approach to access a series of silanol and silyl ether products.

Photosynthesis of 3-Alkylated Coumarins from Carboxylic Acids Catalyzed by a Na2S-Based Electron Donor-Acceptor Complex

A simple and practical electron donor-acceptor (EDA) strategy to synthesize various 3-alkylated coumarins from easily available coumarins and naturally abundant carboxylic acids under photocatalyst-, oxidant-, and additive-free and mild conditions is reported. Using Na₂S as the catalytic electron donor, a series of primary, secondary, and tertiary carbon radicals can be efficiently generated, and the EDA complex can be regenerated without an alkaline additive.

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.

Diazazethrene bisimide: a strongly electron-accepting π-system synthesized via the incorporation of both imide substituents and imine-type nitrogen atoms into zethrene

The development of highly electron-accepting π-systems is a fundamentally challenging issue despite their potential applications as high-performance n-type organic semiconductors, organic rechargeable batteries, and stable redox-active organocatalysts. Herein, we demonstrate that the incorporation of both imide substituents and imine-type nitrogen atoms into zethrene affords the strongly electron-accepting π-system diazazethrene bisimide (DAZBI). DAZBI has a low-lying LUMO (-4.3 eV vs. vacuum) and is readily reduced by the weak reductant l-ascorbic acid to afford the corresponding dihydro species. The injection of two electrons into DAZBI provides the corresponding dianion. These reduced species display remarkable stability, even under ambient conditions, and an intense red fluorescence. A DAZBI dimer, which was also synthesized, effectively accommodated four electrons upon electron injection.

Overcoming Back Electron Transfer in the Electron Donor-Acceptor Complex-Mediated Visible Light-Driven Generation of α-Aminoalkyl Radicals from Secondary Anilines

An additive-free, visible light-driven annulation between N-aryl amino acids and maleimide to form tetrahydroquinolines (THQs) is disclosed. Photochemical activation of an electron donor-acceptor (EDA) complex between amino acids and maleimides drives the reaction, and aerobic oxygen acts as the terminal oxidant in the net oxidative process. A range of N-aryl amino acids and maleimides have been investigated as substrates to furnish the target THQ in good to excellent yield. Mechanistic investigations, including titration and UV-vis studies, demonstrate the key role of the EDA complex as the photoactive species.

Synthesis of 10-Phenanthrenols via Photosensitized Triplet Energy Transfer, Photoinduced Electron Transfer, and Cobalt Catalysis

Due to the inert redox activity and high triplet energy, radical chemistry of 1,3-dicarbonyl compounds usually requires prefunctionalization substrates, external oxidant, and high-energy UV light. Here, we report a visible-light-driven photocatalyst/cobaloxime system composed of a photosensitized energy transfer reaction (PEnT) and photoinduced electron transfer reaction (PET) and with an interrupted 6π-photocyclization/dehydrogenative aromatization in one pot to synthesize 10-phenanthrenols. Preliminary mechanistic studies revealed that fac-Ir(ppy)₃ plays the dual roles of energy transfer catalysis for photocycloaddition via 1,2-biradical intermediates of 1,3-dicarbonyl compounds and photoredox/cobaloxime catalysis dehydrogenative aromatization of 1,4-biradical rather than the intermediates via 6π photocyclization in the tandem reaction. In contrast to previous well-established radical chemistry of 1,3-dicarbonyl compounds, we provide a new strategy for the activation of 1,3-dicarbonyl compounds under visible light catalysis, affording a novel cyclization strategy with extremely high atom economy for the synthesis of 10-phenanthrenols.

Recent Advances in Employing Catalytic Donors and Acceptors in Electron Donor-Acceptor Complex Photochemistry

Electron donor-acceptor (EDA) complexes provide a means to initiate radical reactions under visible light irradiation using substrates that do not absorb visible light individually. Catalytic approaches to complex formation are vital for advancing this synthetic strategy as it decouples the complexation and photogeneration of radicals from substrate functionalization, a limitation inherent to stoichiometric approaches that restricts structural diversity. This Synopsis highlights recent developments in EDA complex photochemistry in which either the donor or acceptor are employed catalytically.

Electron donor–acceptor complex-catalyzed photoredox reactions mediated by DIPEA and inorganic carbonates

A DIPEA–NHPI ester–inorganic carbonate catalytic EDA complex is reported as an efficient and sustainable radical generation platform for developing photocatalytic reactions.

Photocatalytic synthesis of 10-phenanthrenols via intramolecular cycloaromatization under oxidant-free conditions

A novel tandem photocycloaddition/dehydrogenative aromatization with hydrogen evolution of ortho biaryl-appended 1,3-dicarbonyl compounds for the synthesis of 10-phenanthrenol via cobaloxime catalysis is disclosed.