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The development of novel synthetic methods for quaternary ammonium salts is highly demanded since the current synthesis heavily relies on the conventional Menshutkin reaction. Herein, we report photoredox-catalyzed alkylation of α-brominated alkenylammonium salts. Mechanistically, the generation of a highly reactive α-ammoniovinyl radical is the key to our method. This reaction enables the synthesis of various unprecedented α-alkylated alkenylammonium salts. [ABSTRACT FROM AUTHOR]

A simple and efficient methodology for the selective oxygenation of benzylic C(sp3)−H bond and oxidation of primary and secondary alcohols using non‐noble photoredox copper catalyst under visible light irradiation is described. Notably, non‐noble copper photoredox catalysts were found to be good for the oxidation reactions when compared to various commercially available photoredox catalysts employed in the present methodology. In addition, oxygen as clean oxidant at room temperature and compatible for both the oxygenation and oxidation reactions. A wide range of carbonyl compounds bearing both electron rich and electron deficient substituents was synthesized in moderate to excellent yields under milder and environmentally friendly conditions. Also, a thorough investigation was carried out to understand the mechanism of both oxidation reactions. [ABSTRACT FROM AUTHOR]

Recently, photoredox catalysis using 9,10-phenanthrenequinone (PQ) has emerged as an efficient method for the transformation of various organic compounds. Low cost and good availability make it a promising alternate to typical transition metal complex-based photocatalysts. It has emerged as an alternative in photoredox catalysis highlighting recent advancement in organic transformation using (PQ) as photocatalyst. [ABSTRACT FROM AUTHOR]

Spirocycles are important structural motifs, found in natural and pharmaceutical compounds, which have attracted considerable interest in modern drug discovery research. Herein, we describe the development of a visible light‐mediated ipso‐cyclization of amino acid derivatives with N‐(2‐phenyl)benzoyl groups, allowing easy access to a variety of spirocyclohexadienes. The addition of water was found to be beneficial in promoting the reaction progress. Investigation of the substrate scope revealed that incorporating an electron‐donating moiety at the 3′‐position of the biphenyl group resulted in a more favorable outcome for spirocycle formation. [ABSTRACT FROM AUTHOR]

Polyamines, such as putrescine and spermidine, are pivotal in various biological processes across living organisms. Despite their significance, structurally modified polyamines offer a less‐explored avenue for discovering bioactive compounds. The limitation is attributed to the synthetic difficulty of accessing functionalized polyamines. In this study, we accomplished photoredox‐catalyzed functionalization of polyamines to diversify their structure. The rapid functionalization allows attaching fluorophores to the target polyamine, facilitating the development of molecular probes for advancing chemical biology studies. [ABSTRACT FROM AUTHOR]

Photocatalytic C−H bond phosphonioethylation of aldehydes with vinylphosphonium bromide has been developed. Various β‐phosphonioalkylketones are synthesized from readily available aldehydes under neutral conditions. Mechanistic studies suggest that C−H activation of aldehydes occurs through hydrogen‐atom transfer by a bromine radical and that an alcoholic additive, which showed marked effects in increasing the efficiency of the reaction, is involved in the reaction as a proton source. [ABSTRACT FROM AUTHOR]

Fluoroalkyl compounds are widely used, underscoring a pressing need for the development of methods for their synthesis. However, reports on perfluoroalkylation to styrenes have been sparse. In this study, both hydroxy- and hydro-perfluoroalkylation of styrene were achieved using visible light reactions, catalyzed by eosin Y, by selecting appropriate additives and controlling the eosin Y quenching cycle. These reactions are heavy-metal free, use water as the hydroxyl or hydrogen source, and employ inexpensive and readily available reagents. [ABSTRACT FROM AUTHOR]

Fluoroalkyl compounds are widely used, underscoring a pressing need for the development of methods for their synthesis. However, reports on perfluoroalkylation to styrenes have been sparse. In this study, both hydroxy- and hydro-perfluoroalkylation of styrene were achieved using visible light reactions, catalyzed by eosin Y, by selecting appropriate additives and controlling the eosin Y quenching cycle. These reactions are heavy-metal free, use water as the hydroxyl or hydrogen source, and employ inexpensive and readily available reagents.

Addition reactions of ketene silyl acetals with alkenes that do not have an electron‐withdrawing group are generally difficult because the nucleophilicity of ketene silyl acetals and the electrophilicity of alkenes are not sufficient. Herein, we report photocatalytic addition reactions of ketene silyl acetals with alkenes that proceed through formation of α‐carbonyl radicals. In the presence of an appropriate protic additive, the reactions proceeded smoothly under blue‐light irradiation to afford the desired products in moderate to high yields. [ABSTRACT FROM AUTHOR]

Organocatalyzed atom transfer radical polymerization (O‐ATRP) is a method of producing polymers with precise structures under mild conditions using organic photoredox catalysts (PCs). Due to the unknown toxicity of PCs and their propensity to introduce color in polymers synthesized by this method, removal of the PC from the polymer product can be important for certain applications of polymers produced using O‐ATRP. Current purification methods largely rely on precipitation to remove the PC from the polymer, but a more effective and efficient purification method is needed. In this work, an alternative purification method relying on oxidation of the PC to PC·+ followed by filtration through a plug to remove PC·+ from the polymer and removal of the volatiles was developed. A range of chemical oxidants and stationary phases were tested for their ability to remove PCs from polymers, revealing chemical oxidation by N‐bromosuccinimide followed by a filtration through a silica plug can remove up to 99% of the PC from poly(methyl methacrylate). Characterization of the polymer before and after purification demonstrated that polymer molecular weight, dispersity, and chain‐end fidelity are not signficantly impacted by this purification method. Finally, this purification method was tested on a range of dihydrophenazine, phenoxazine, dihydroacridines, and phenothiazine PCs, revealing the strength of the chemical oxidant must match the oxidation potential of the PC for effective purification. [ABSTRACT FROM AUTHOR]

Herein reported is a two‐step protocol for the α‐allylic alkylation of alcohols consisting of photocatalytic anti‐Markovnikov addition of the α‐C−H bond of alcohols to vinylphosphonium bromides and subsequent Wittig olefination with aldehydes. The protocol is marked by simplicity of the photoreaction system with a single catalyst and broad scope of alcohols, ranging from readily available chemical feedstocks to functionalized molecules, and is attractive as a synthetic tool. Both primary and secondary alcohols can be functionalized at the α‐C−H bond to produce the corresponding α‐tertiary and quaternary (E)‐homoallylic alcohols. The mechanistic studies suggest that α‐C−H activation of alcohols occurs through hydrogen atom transfer by a bromine radical, which is photocatalytically generated from a vinylphosphonium bromide. [ABSTRACT FROM AUTHOR]

Direct functionalization of inert C(sp3)-H bonds in pharmaceutically significant compounds is very important in modern synthetic organic chemistry. In this article, we disclose a practical and efficient method for the oxidative lactonization of benzylic C(sp3)-H bonds enabled by the synergistic interactions of organic dye-type rose bengal, n-Bu4N·Br, O2 and Na2HPO4 under visible light irradiation. This reaction does not require transition metal catalysts or strong oxidants. A range of structurally diverse phthalides has been synthesized with excellent selectivity and high functional group compatibility. The late-stage application of this reaction to the preparation of structurally complex phthalides demonstrates its synthetic utility. [ABSTRACT FROM AUTHOR]

Oxygen‐tolerant reversible addition‐fragmentation chain transfer polymerization (RAFT) can be successfully achieved through the addition of organic and inorganic photoredox catalysts or other additives. Thus, developing a simple oxygen‐tolerant RAFT without additional catalyst and initiator will augment the development of this field. In this work, two‐component systems, 2‐(dimethylamino)ethyl methacrylate (DMAEMA) and 4‐cyanopentanoic acid dithiobenzoate (CPADB), have been successfully applied to develop green and oxygen‐tolerant RAFT under aqueous conditions without any additional catalysts, where dithioester CPADB was employed as an iniferter agent (initiator‐transfer‐terminator) for polymerization control, as well as an intrinsic photoredox catalyst for deoxygenation. DMAEMA was utilized as monomer and electron donor. In the present work, dithioester‐assisted oxygen removal in aqueous RAFT photopolymerization is reported for the first time. This work provides a simple and green method for oxygen‐tolerant RAFT polymerization. [ABSTRACT FROM AUTHOR]

A simple and efficient method has been developed to synthesize 1‐oxa‐4‐aza‐spirooxazolines. The reaction was carried out at room temperature using rose bengal as an organic photoredox catalyst and blue LED as a light source. It was observed that quinones underwent spiroannulation reaction with vinyl azide on C−O double bond instead of C−C double bond through which various corresponding 1‐oxa‐4‐aza‐spirooxazolines have been synthesized in good to excellent yields. [ABSTRACT FROM AUTHOR]

Organochromium(III) species are versatile nucleophiles in complex molecule synthesis due to their high functional group tolerance and chemoselectivity for aldehydes. Traditionally, carbonyl addition reactions of organochromium(III) species were performed through reduction of organohalides either using stoichiometric chromium(II) salts or catalytic chromium salts in the presence of stoichiometric reductants [such as Mn(0)]. Recently, alternative methods emerged involving organoradical formation from readily available starting materials (e.g., N -hydroxyphthalimide esters, alkenes, and alkanes), followed by trapping the radical with stoichiometric or catalytic chromium(II) salts. Such methods, especially using catalytic chromium(II) salts, will lead to the development of sustainable chemical processes minimizing salt wastes and number of synthetic steps. In this review, methods for generation of organochromium(III) species for addition reactions to carbonyl compounds, classified by nucleophiles are described. 1 Introduction 2 Alkylation 2.1 Branch-Selective Reductive Alkylation of Aldehydes Using Unactivated Alkenes 2.2 Linear-Selective Alkylation of Aldehydes 2.2.1 Catalytic Decarboxylative Alkylation of Aldehydes Using NHPI -Esters 2.2.2 Catalytic Reductive Alkylation of Aldehydes Using Unactivated Alkenes 2.2.3 Alkylation of Aldehydes via C(sp3)–H Bond Functionalization of Unactivated Alkanes 2.3 Catalytic α-Aminoalkylation of Carbonyl Compounds 3 Allylation 3.1 Catalytic Allylation of Aldehydes via Three-Component Coupling 3.2 Catalytic Allylation of Aldehydes via C(sp3)–H Bond Functionalization of Alkenes 4 Propargylation: Catalytic Propargylation of Aldehydes via Three-Component Coupling 5 Conclusion [ABSTRACT FROM AUTHOR]

This article presents, for the first time, the kinetics and the general conversion features of a 3-component system, benzophenone–triphenylamine(BT)/iodonium/Amine, based on proposed mechanism of Liu et al., for both free radical polymerization (FRP) of acrylates and the free radical promoted cationic polymerization (CP) of epoxides using the new multi-functional initiator of BT. The additives, iodonium and amine, ethyl 4-(dimethylamino)benzoate (EDB), have the dual function of (i) regeneration BT and (ii) produce of extra radicals for improved FRP and CP. Analytic formulas are developed to explore the new features including: (i) the conversion efficacy (CE) of FRP is an increasing function of the light intensity, the effective absorption coefficient, and the concentration sum of each of the components, BT, Iod, amine, for transient state. However, CE at steady-state is independent to the light intensity; (ii) the trifunctional hybrid structures of BT3 leads to larger light absorption than other types of BT; it also provides more active sites for the H-abstraction in the presence of EDB, leading to high CE; (iii) the efficacy of FRP is an increasing function of the amine (EDB) concentration, in contrast to that of CP having an opposite dependence; (iv) the consumption rate of BT3 in the BT3/Iod/EDB system is slower than that of the BT3/Iod system due to photoredox catalytic cycle, and the larger initiator regeneration (RGE) in the three-component system. A comprehensive model is also proposed that the CE (for both FRP and CP) is governed by (NjKjbI), whereas more complex formulas are developed; where Kj is an effective rate constant proportional to the electron transfer quantum yield, and the combined effects of other coupling rate constants; b is an effective absorption coefficient given by the light absorption and excited state quantum yield. Measured data are analyzed by numerical simulation for the CE of FRP and CP, based on ten rate equations. [ABSTRACT FROM AUTHOR]

An efficient synthesis of methoxy-substituted thioxanthylium salts has been developed. The reaction of diaryl sulfides with benzoyl chlorides in the presence of TfOH smoothly proceeded to give the desired thioxanthylium salts in good yields. In their UV–vis spectra, the maximum absorption wavelengths of methoxy-functionalized thioxanthylium salts were observed at around 460 nm, which show a drastic red shift compared to the parent thioxanthylium salts. The present reaction provides a versatile access to functionalized thioxanthylium salts, and therefore it constitutes a promising tool for the synthesis of biologically and photochemically active molecules.

Recent progresses achieved in terms of synthetic procedures allow now the access to polymers of well-defined composition, molecular weight and architecture. Thanks to these recent progresses in polymer engineering, the scope of applications of polymers is far wider than that of any other class of material, ranging from adhesives, coatings, packaging materials, inks, paints, optics, 3D printing, microelectronics or textiles. From a synthetic viewpoint, photoredox catalysis, originally developed for organic chemistry, has recently been applied to the polymer synthesis, constituting a major breakthrough in polymer chemistry. Thanks to the development of photoredox catalysts of polymerization, a drastic reduction of the amount of photoinitiators could be achieved, addressing the toxicity and the extractability issues; high performance initiating abilities are still obtained due to the catalytic approach which regenerates the catalyst. As it is a fast-growing field, this review will be mainly focused on an overview of the recent advances concerning the development of organic and organometallic photoredox catalysts for the photoreticulation of multifunctional monomers for a rapid and efficient access to 3D polymer networks.

Homocoupling reactions of benzylamines and benzyl alcohols were examined under synergistic catalysis conditions with a photoredox catalyst and thiobenzoic acid as a hydrogen atom abstractor. When pivalaldehyde was used as an electron acceptor, oxidative dimerization proceeded selectively, whereas the use of benzaldehydes or iminium ions as electron acceptors resulted in redox‐neutral coupling. These reactions afforded symmetrical 1,2‐diamines and 1,2‐diols in good yields. [ABSTRACT FROM AUTHOR]

In the present study, an efficient visible‐light and cercosporin catalyzed direct sulfenylation of electron rich aromatic compounds such as indoles, active methylenes, and phenols with thiols through a photoredox catalyzed process has been reported through the cleavage of a C−H/S−H bond at room temperature under transition‐metal‐free conditions. The reported methodology gives a direct way in the formation of C−S bonds with broad functional group compatibility, which produces 3‐sulfenylated indoles, α‐sulfenylated carbonyl compounds and diaryl sulfides in moderate to good yields. The advantage of the reaction is that it meets the criteria of green and sustainable synthetic chemistry and can be used widely in the fields of organic synthesis and pharmaceutical chemistry. [ABSTRACT FROM AUTHOR]

The development of multi‐component orthogonal polymerizations (MOPs) with simple procedure and high efficiency is crucial for rational polymer synthesis. In this work, photo‐triggered Cu(I)‐catalyzed azide‐alkyne cycloaddition (CuAAC) polymerization are first investigated, employing copper(II) thioxanthone carboxylate (Cu(TX)2) as photoredox catalyst and sunlight as stimuli. Then, the novel MOPs using one photoredox catalyst, Cu(TX)2 to simultaneously mediate two different photopolymerizations, are successfully realized in one‐pot, where photo‐induced electron transfer atom transfer radical polymerization and photo‐activated CuAAC polymerization can effectively proceed in a one‐pot and non‐interfering fashion to afford predetermined copolymers with well‐defined structure. [ABSTRACT FROM AUTHOR]

The development of catalyst-controlled, site-selective C(sp3)–H functionalization reactions is currently a major challenge in organic synthesis. In this paper, a novel bond-weakening catalyst that recognizes the hydroxy group of alcohols through formation of a borate is described. An electron-deficient borinic acid–ethanolamine complex enhances the chemical yield of the α-C–H alkylation of alcohols when used in conjunction with a photoredox catalyst and a hydrogen atom transfer catalyst under irradiation with visible light. This ternary hybrid catalyst system can, for example, be applied to functional-group-enriched- peptides. [ABSTRACT FROM AUTHOR]

The improved catalytic conditions and detailed reaction mechanism of the visible-light driven hydrocarboxylation of alkenes with CO2 by the Rh(I) and photoredox dual catalysts were investigated. The use of the benzimidazoline derivative, BI(OH)H, as a sacrificial electron donor was found to increase the yield of the hydrocarboxylated product by accelerating the reduction process. In addition, the incorporation of the cyclometalated Ir(III) complex as a second photosensitizer with [Ru(bpy)3]2+ photosensitizer also resulted in the promotion of the reduction process, supporting that the catalytic cycle includes two photochemical elementary processes: photoinduced electron and energy transfers.

The reaction of readily available and bench‐stable N‐alkoxypyridinium salts with arylboronic and vinylboronic acids afforded δ‐aryl and δ‐vinyl alcohols, respectively, in the presence of fac‐Ir(ppy)3 and Cu(OTf)2 dual catalysts. The reaction takes place through a domino process involving the reductive generation of alkoxyl radicals, 1,5‐hydrogen atom transfer (1,5‐HAT) and the copper‐catalyzed cross‐coupling reaction of the resulting translocated carbon radicals with boronic acids. Complementary to the Minisci reaction, this method allows for the arylation of nucleophilic alkyl radicals with both electron‐rich and electron‐poor arenes under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Abstract Four ferrocene-based D-π-A dyes with effective intramolecular charge transfer (ICT) properties are designed and synthesized. These dyes can be used as new photoredox catalysts in free radical photopolymerization under soft blue and green LED irradiations. Different π-conjugation bridge molecules contained in the molecular structures have been shown to affect the photoreactivities of the synthesized dyes in the photoinitiating systems. The UV–Vis absorption, electrochemical, and third-order nonlinear optical properties are investigated. Experimental results are completed with theoretical calculations to gain further insight into the ICT of the dyes with different π-conjugation bridge molecules. A good correlation of the π-conjugation bridge molecule changes of the dyes with the experimental results is established. Graphical abstract Ferrocene based D-π-A dyes as novel photoredox catalysts in photopolymeization under soft visible LED irradiations. Image 1 Highlights • Four ferrocene-indanone organometallic dyes are designed and synthesized. • The dyes exhibit effective ICT characters and show good nonlinear absorption properties. • A good correlation of experimental and theoretical results is established. • The dyes can be used as photoredox catalysts in photopolymerization under LED irradiations. [ABSTRACT FROM AUTHOR]

This investigation presents the use of a photoredox catalyst "G1" as a photoinitiating system for free radical/cationic hybrid polymerization under mild irradiation conditions. The G1 system (G1/iodonium salt/ N -vinylcarbazole), can simultaneously initiate the free radical and cationic polymerization reactions upon exposure to a visible (405 nm) light from a Light Emitting Diode (LED) source. The multicomponent G1 system is able to simultaneously generate radical and cationic species through a catalytic photoredox process. The curing of thin samples (25 μm), thick samples (1.4 mm) as well as the manufacture of hybrid system/glass fibers composites (˜2 to 4 mm thickness) was realized and the influence of the ratio of cationic/radical monomer blends on the polymerization kinetics was studied. The use of G1 in visible light photoinitiating system for the access to composites and 3D printing experiments was particularly outlined. G1 was also shown to have low levels of migration from the cured materials. When compared to reference materials ("F1", a similar copper complex and an anthracene derivative, dibutoxy anthracene), G1 showed better polymerization efficiency. The initiation efficiency was investigated through the real-time Fourier transform infrared (RT-FTIR) spectroscopy and optical pyrometry. Dynamical Mechanical Analysis has been used to determine the glass temperature transition of the cured hybrid system as a complementary technique. [ABSTRACT FROM AUTHOR]

Under mild dual photoredox/copper catalysis, the reaction of N‐alkoxypyridinium salts with readily available silyl reagents (TMSN3, TMSCN, TMSNCS) afforded δ‐azido, δ‐cyano, and δ‐thiocyanato alcohols in high yields. The reaction went through a domino process involving alkoxy radical generation, 1,5‐hydrogen atom transfer (1,5‐HAT) and copper‐catalyzed functionalization of the resulting C‐centered radical. Conditions for catalytic enantioselective δ‐C(sp3)−H cyanation were also documented. Be selective: δ‐Azido, δ‐cyano, and δ‐thiocyanato alcohols were obtained in high yields from N‐alkoxypyridinium salts under mild dual photoredox/copper catalysis. A catalytic enantioselective δ‐cyanation protocol in the presence of a chiral bisoxazoline ligand was also developed. [ABSTRACT FROM AUTHOR]

Highlights • Metallocorroles are still much less frequently used as photocatalysts than metalloporphyrins or ruthenium bipyridine complexes. • The photophysical properties of metallocorroles are easily tuned and their intersystem crossing yield to the triplet can be approaching 99%. • Metallocorroles have a great future for photocatalysis. • Metallocorroles are efficient agents for photodynamic therapy and inhibition. Abstract Despite the similarity with porphyrins, the focus on the photophysical properties of corroles and their chelates with transition and post-transition metal ions (metallocorroles) started quite late. Free base corroles are much more fluorescent than related macrocycles; and this feature can be easily changed and tuned by facile synthetic manipulations. Metallocorroles may be designed as to display desired properties such as delayed fluorescence, RT phosphorescence, high yield of intersystem crossing, efficient singlet oxygen generation, and more. The practical utility of metallocorroles has been exemplified by their use as photosensitizers in photodynamic therapy for fighting cancer, photodynamic inactivation of microorganisms, as catalysts for photo-assisted organic reactions and energy-relevant inorganic transformations. Key to success in the above applications is the ability to delicately control the photophysical properties, redox potentials, and the selective positioning of substituents on the corrole macrocycle. [ABSTRACT FROM AUTHOR]

Olefin bifunctionalization is a facile route to obtain complex molecules from abundant and commercially available olefin feedstocks. Visible light together with a catalytic amount of tris(bipyridine)ruthenium salt catalyzes the aryl alkoxylation of styrenes with aryl diazonium salts in alcohol solvents via a photoredox process. The scope of this proposed reaction with respect to various aryl diazonium salts and styrenes has been investigated. Worth its salt: Visible light along with a catalytic amount of tris(bipyridine)ruthenium salt catalyzes the aryl alkoxylation reaction of styrenes with aryl diazonium salts in alcoholic solvents by a photoredox process. The scope of the reaction for various aryl diazonium salts and styrenes have been investigated. [ABSTRACT FROM AUTHOR]

The mechanisms of action (MoA) have been proposed to further reduce the O 2 dependence of photodynamic therapy (PDT) significantly. However, the triplet states of traditional photosensitizers are relatively short and also are easily deactivated by the quenching of H 2 O or O 2 . This is not conducive for the electron transfer in the photocatalytic process and poses a great obstacle to establish the MoA. Therefore, we selected and synthesized a zirconium(IV) complex (Zr( Mes PDP Ph ) 2 ) reported by Milsmann to address this issue. The specific symmetric and intact geometry endowed Zr( Mes PDP Ph ) 2 NPs with long-lived triplet excited state (τ = 350 μs), desired sensitized ability, and improved anti-interfering performance on O 2 , which was matched with the requirements of photoredox catalyst significantly. The results showed that while PDT (I) and PDT (II) could be achieved simultaneously by leveraging Zr( Mes PDP Ph ) 2 NPs, it also could be served as a rare example of thermally activated delayed fluorescence (TADF)-based photoredox catalyst to implement the MoA of PDT. It involved the oxidation of NADH and the establishment of catalytic cycle collaborating by O 2 and cytochrome c (cyt c ) in normoxia and hypoxia, respectively. As a result, the oxygen-free PDT and tumor-growth inhibition was realized.

Cross‐coupling reactions of alkenyl halides with 4‐alkyl‐1,4‐dihydropyridines as alkylation reagents have been achieved by combination of nickel and photoredox catalysts. Alkenyl halides bearing alkyl and aryl substituents are available. Particularly, in the use of aryl‐substituted alkenyl halides, cross‐coupling reactions are associated with E to Z isomerization of alkenes. Thus, Z‐isomers of the products are obtained as major products. The present strategy provides a novel synthetic method to control the stereochemistry around alkenes. Photoredox catalyst serves dual roles! E to Z isomerization proceeds in the nickel‐ and photoredox‐catalyzed cross‐coupling reactions of alkenyl halides with dihydropyridines. The photoredox catalyst works not only to generate alkyl radicals but also to achieve isomerization. [ABSTRACT FROM AUTHOR]

• Eleven 2-arylbenzoazolyl based Ir (III) complexes were prepared. • The configuration of trans- and cis-isomer were confirmed by X-ray. • The substituents effects on photophysical and electrochemical properties were explored. • The photocatalytic efficiency were superior or comparable to [Ir(dF(CF 3)ppy) 2 dtbbpy]PF 6. The [Ir(C^N) 2 (N^N)]+ complexes are one of the most employed family of photocatalyst. The substituent effect of C^N ligand, specifically 2-arylbenzo[ d ]oxazole (pbo) and 2-arylbenzo[ d ]thiazole (pbt), on complexes was discussed in this work. For this purpose, a series of Ir(III) complexes (A1∼C9) with differently substituted pbo/pbt ligands were designed, synthesized and characterized. Crystal structures show that A2 and A6 have a C2 -symmetric trans -configuration while B8 possesses C1 -symmetric cis -isomeric structure. These complexes are highly photoluminescent with quantum yield up to 69% in dilute solution. The maximum emission wavelength span from 485 to 615 nm. The substituent electronic effects on the para -position of phenyl have the greatest impact on the fluorescence properties of the complexes. Electron withdrawing nitro group on the 4-site of phenyl make the greatest red shift in the emission spectra while fluorination leads to blue shifts. The electrochemical measurements were combined with fluorescence data to estimate the excited-state potentials (ESP) of these complexes. Both oxidative and reductive ESP are in a good range compared to the widely applied [Ir(dF(CF 3)ppy) 2 dtbbpy]PF 6 , suggesting that they are high-potential in photoredox catalysis. The complexes A1∼C9 were further applied in the deoxygenation-addition synthesis of N -dimethyl-4-oxo-4-(p -tolyl)butanamide to test the catalytic activity. Excellent yields (up to 91%) were obtained with catalyst A2, A8 and B8. Substitution on substrates was also tolerated in a degree. [Display omitted] [ABSTRACT FROM AUTHOR]

A mild and efficient methodology for the bromination of phenols and alkenes has been developed utilizing visible light-induced photoredox catalysis. The bromine was generated in situ from the oxidation of Br− by Ru(bpy)33+, both of which resulted from the oxidative quenching process.

Photoreactions of acetonitrile solutions of 3,3-diaryl-1,1-dicyano-2-methylprop-1-enes (1a–c) with allyltrimethylsilane (2) in the presence of phenanthrene as a photoredox catalyst and acetic acid as a proton source formed photoallylation (3) and photoreduction (4) products via photoinduced electron transfer pathways. When (S)-mandelic acid was used as the proton source, the reactions proceeded with 3.4 and 4.8 %ee for formation of 3 and 4, respectively. The results of studies of the effect of aryl ring substituents and several chiral carboxylic acids suggested that the enantioselectivities of the reactions are governed by steric controlled proton transfer in intermediate complexes formed by π-π and OH-π interactions of anion radicals derived from 1a–c and chiral carboxylic acids.

Photocatalytic isomerization of thermodynamically stable E-alkene to less stable Z-alkene has been the subject of numerous studies, being successfully achieved mainly under UV irradiation. Recent development of visible light photoredox catalysis has witnessed it emerging as a powerful tool for the access of new structural complexity and many challenging targets. Herein, we report a visible light-promoted E to Z isomerization of cinnamates. When E-isomer of cinnamates was irradiated with blue light in the presence of an organo-photocatalyst, fac-Ir(ppy)3, Z-isomer was exclusively obtained in high yields and with good selectivity. The mild, convenient reaction condition has made this protocol an effective synthetic methodology, which was subsequently implemented in an efficient synthesis of coumarins. [ABSTRACT FROM AUTHOR]

The volatility of noble metals prices, globally increasing demands, and its limited resources drive chemists to find alternatives in the place of expensive transition metal catalysts. So, this is a time for the scientific community to find alternative sources to replace Nobel metals, and it is making genuine changes in developing sustainable synthetic methods. Photoexcited transition-metal catalysis is revitalizing the research area for functionalizing diverse π-bond systems. The massive progression of the two conventional photochemical reactivity modes, photoredox catalysis, and synergetic photocatalyst/transition-metal catalysis, has fueled the search for a next-level mechanistic paradigm visible-light initiated excited-state transition-metal catalysis (Cu, Pd, Fe, Au, Co, Ni, W, and Mn), which can be deployed to harvest light energy and convert it into chemical energy in a single catalytic cycle. This review summarizes early examples of the visible-light-induced photocatalytic activities of conventional transition metals employed in C-H activation, π-bond functionalization, and annulation reactions of unsaturated compounds, and excluding the commonly used expensive photocatalysts (i.e., Ir-, and Ru-based pyridyl complexes). Unlike the other two classical photochemical approaches, the discrete inner-sphere mechanism associated with photoexcited transition metals facilitates reactive substrate-metal-complex interactions. It enables the direct involvement of excited-state catalysts in bond-forming or-breaking processes. • The light driven radical capture mechanism solve the long-standing slow oxidative addition problem of copper catalyst. • At higher oxidation state, iron metal acting as a of Lewis acid, and stimulating the π-bond activation reactions. • The "super nucleophilic" Co(III)* complexes can generate the carbon centered radicals via homolytic Co-C bond cleavage. • TBADT, a polyoxotungstate involved C-H bond activation via S H 2 mechanism is irrespective of substrate redox potential. • Manganese employed photochemical reactions mostly follow the atom transfer radical mechanism (ATRM). [ABSTRACT FROM AUTHOR]

The bad impact of fossil fuel and the need of green energy resources have directed many researchers to develop various light-driven, CO 2 non emissive hydrogen producing catalytic routes. Majority of such routes involve a catalytic duo made up of a light harvesting photoredox catalyst and a proton reducing catalyst in combination with an excessive amount of sacrificial electron donor. An increasing number of molecular photocatalytic systems for hydrogen evolution reaction (HER) are found in the literature with the progressive turnover frequency (TOF) and turnover number (TON). The development is tip toeing towards the photocatalytic systems with required efficiency and durability for the production of green hydrogen. The present work is focused on conferring the basic understanding of the photoredox process for the generation of molecular hydrogen as green fuel, covering recent important reports available in the literature under homogeneous reaction medium. It also includes the future direction of research and perspective for the economically viable green route of hydrogen production. [Display omitted] • Fundamental discussion on photoredox catalysis and its applications in different fields. • Summarization of various photoredox catalytic routes for the production of green hydrogen. • Discussion on reactivity of high performing earth abundant metal based molecular complexes for the hydrogen production. • Comparative study on TON and TOF of the catalysts and discussion on scope of work with future directions. [ABSTRACT FROM AUTHOR]

Photoinitiated living radical polymerization has attracted wide attention in recent years. Titanium dioxide (TiO) is a kind of semi-conducting metal oxide which is widely used in water treatment, photovoltaics and organic synthesis. However, there is few application in living radical polymerization. In this study, photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of methyl methacrylate (MMA) using TiO as photoredox catalyst is successfully carried out. It offers good control over molecular weights and polydispersities (PDI). The end group fidelity of PMMA is successfully demonstrated by chain extension for the preparation of poly(methyl methacrylate)- b-poly(dimethylaminoethyl methacrylate) (PMMA- b-PDMAEMA) copolymer. Moreover, the polymerization can be controlled by switching 'ON' and 'OFF' the light. [ABSTRACT FROM AUTHOR]

The photochemical transformations have gained widespread recognition in the recent years because of the generally mild reaction conditions needed for substrate activation, ideally the light alone and their appropriateness for green reactions. A variety of catalyst systems have been developed for visible light driven reactions. The unprecedented [Ru(bpy)3]2+ complexes as well as xanthene based organic dyes has gained widespread recognition due to their effectiveness and broad applications in organic synthesis. The Photoredox catalyst based on transition metal complexes or organic dyes have comparable redox abilities but each system has its own distinctive benefits. In this perspective photocatalytic efficacy of organometallic ruthenium and eosin Y have been investigated in connection to their pursuit for the photocatalytic oxidative coupling of N-aryl tetrahydroisoquinoline with carbon and sulfur containing nucleophiles. The eosin Y confirmed to be more efficient in our studies. The photophysical properties and reaction mechanism of both types of catalysts are well established in the literature. [ABSTRACT FROM AUTHOR]

ABSTRACT A new strategy is developed to prepare both α,ω-dithiol and α,ω-divinyl linear telechelic polythiolether oligomers by visible light induced thiol-ene chemistry in the presence of a fac-Ir(ppy)3 photoredox catalyst. Polythiolether oligomers of well-defined end groups and controlled molecular weights have been successfully synthesized at varying monomer molar ratios of 1,4-benzenedimethanethiol (BDMT) to diethylene glycol divinyl ether (DEGVE). 1H NMR and MALDI-TOF MS analyses demonstrate that as-prepared polythiolethers possess high end-group fidelity, which is further supported by the successful polyaddition of polythiolethers bearing α,ω-dithiol and α,ω-divinyl groups. For example, with the α,ω-dithiol- ( Mn = 1900 g mol−1, PDI = 1.25) and α,ω-divinyl-terminated ( Mn = 2000 g mol−1, PDI = 1.29) polythiolethers as macromonomers, the molecular weight of resulting polythiolether is up to 7700 g mol−1 with PDI as 1.67. The reactivity of the terminal thiol group is further confirmed by the addition reaction with N-(1-pyrenyl)maleimide. UV-vis spectra and fluorescene measurements suggest that fac-Ir(ppy)3 undergo a redox quenching process reacted with BDMT to generate thiyl free radicals. With these results, the mechanism of the thiol-ene reaction catalyzed by photoredox catalyst is proposed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 740-749 [ABSTRACT FROM AUTHOR]

An efficient hetero-cross-dehydrogenative-coupling (hetero-CDC) reaction betweenN-protected indoles and phosphites to 2-indolyphosphites is described. The regioselective methodology took place in the presence of photo redox catalyst Ru(bpy)3(PF6)2combined with oxygen as an clean oxidant when exposed to visible light, furnishing the 2-indolyphosphites as the exclusive products in moderate to good yields with good functional group tolerance. Moreover, the phosphonylation protocol was proved by the control reaction to proceed through the radical pathway. [ABSTRACT FROM PUBLISHER]

Despite the robustness and flexibility of thermal controlled radical polymerization (CRP), it still remains a big challenge to prepare clickable polymers bearing acetenyl groups. In this paper, visible light CRP of propargyl methacrylate (PgMA) is investigated using ethyl-α-bromophenylacetate as initiator andfac-Ir(ppy)3as a photoredox catalyst. By controlling the polymerization time, a linear increase of Mnwith monomer conversion and narrow polydispersity index is achieved. Specifically, with [PgMA]/[Initiator]/[fac-Ir(ppy)3]=210:1:0.0285, the products show Mn=8300 g/mol and Mw/Mn=1.24 at 17% monomer conversion and Mn=17100 g/mol and Mw/Mn=1.52 at 50% monomer conversion. This result is much better than that of thermally activated Cu-ATRP of PgMA. When the ratio of MMA/PgMA is 5:1, the copolymerization product shows Mn=25300 g/mol and Mw/Mn=1.75 at 66% monomer conversion. The FTIR,1H-NMR and13C-NMR spectra of the PPgMA show nosp2-sp2carbon-carbon bond, indicating that acetenyl groups are intact. In conclusion, this technology offers a versatile route for the preparation of (co)polymers with pendant alkynyl groups. [ABSTRACT FROM PUBLISHER]

ABSTRACT A new visible light-induced controlled radical polymerization of methacrylate with perfluoro-1-iodohexane (CF3(CF2)5I) as the initiator in the presence of a photoredox catalyst ( fac-[Ir(ppy)3]) was developed. Mechanistically, a photoexcited fac-[Ir(ppy)3]* complex reacted with dormant C-I species to generate the chain propagating radical and IrIVI complex, which could be reversibly reduced by the propagating radical. The molecular weight ( Mn) and the corresponding distribution index ( Mw /Mn = 1.4) were controlled in the polymerization of methyl methacrylate (MMA). For the polymerization of functional monomers, such as glycidyl methacrylate (GMA) and trifluoroethyl methacrylate, their monomer conversions could be up to 96 and 94%, respectively. No polymerization reaction took place without external light stimulation, indicating that the system was an ideal photo 'on−off' switchable system. Furthermore, a clean diblock copolymer PMMA- b-PGMA was successfully synthesized with PMMA-I as the macroinitiator. With CF3(CF2)5I as the initiator, short CF3(CF2)5− group tags were introduced on the produced polymer chains. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3283-3291 [ABSTRACT FROM AUTHOR]

ABSTRACT A new visible light-induced controlled radical polymerization of methacrylate with perfluoro-1-iodohexane (CF3(CF2)5I) as the initiator in the presence of a photoredox catalyst ( fac-[Ir(ppy)3]) was developed. Mechanistically, a photoexcited fac-[Ir(ppy)3]* complex reacted with dormant C-I species to generate the chain propagating radical and IrIVI complex, which could be reversibly reduced by the propagating radical. The molecular weight ( Mn) and the corresponding distribution index ( Mw /Mn = 1.4) were controlled in the polymerization of methyl methacrylate (MMA). For the polymerization of functional monomers, such as glycidyl methacrylate (GMA) and trifluoroethyl methacrylate, their monomer conversions could be up to 96 and 94%, respectively. No polymerization reaction took place without external light stimulation, indicating that the system was an ideal photo 'on−off' switchable system. Furthermore, a clean diblock copolymer PMMA- b-PGMA was successfully synthesized with PMMA-I as the macroinitiator. With CF3(CF2)5I as the initiator, short CF3(CF2)5− group tags were introduced on the produced polymer chains. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3283-3291 [ABSTRACT FROM AUTHOR]