Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• in photocatalysis using copper complexes. Their applications in various reactions, such as ATRA, reduction, oxidation, proton-coupled electron transfer, and energy transfer reactions are discussed. Keywords: ATRA reactions; copper catalysis; energy transfer; oxidation; PCET reactions; photocatalysis

• ; reduction; Introduction For a decade, the realm of catalysis has known a significant renewal with the rise of photocatalysis [1]. The fact that a reaction can be carried out, and, more specifically, catalyzed in the presence of visible light and a photosensitive catalyst (organic or organometallic

• ) provided a drastic change of paradigm to the community. Indeed, photocatalysis allows carrying out photochemical reactions in the visible region (redox transformation and energy transfer process). This tremendous progress provided a huge gain of selectivity in photochemical transformations. Indeed, as most

Naphthalene diimides with improved solubility for visible light photoredox catalysis

• Barbara Reiß and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201

• ; photoredox catalysis; Introduction Photocatalysis couples the physical process of light absorption to an organic-chemical reaction by means of time, space and energetics. In order to apply visible light for photocatalysis despite its rather low energy this coupling requires to be mediated by a sensitizing

• support by the Deutsche Forschungsgemeinschaft (Wa 1386/16-1) and KIT is gratefully acknowledged. BR thanks the GRK 1626 “Chemical photocatalysis” (funded by the Deutsche Forschungsgemeinschaft) for participation in their qualification program.

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• -component reaction with aryldiazonium tetrafluoroborates 68, DABCO·(SO2)2 (69) and nitriles 70 under Ru(IV) photocatalysis with visible light and in the presence of a Lewis acid (Scheme 21) [101]. Up to 24 isoindolinone derivatives were obtained, bearing a wide variety of aryl moieties at the sulfonyl group

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• strategies, such as photocatalysis or electrocatalysis, can be another orientation for further developments. This review opens the scope for future developments in new methodologies which promise the synthesis of novel fused cyclic systems with a wide range of medicinal and synthetic applications. The

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• 12: Copies of 1H and 13C NMR spectra, mass spectra, absorption and emission spectra and cyclic voltammetry data of 1–11 and 17. Acknowledgements Financial support by the Deutsche Forschungsgemeinschaft (Wa 1386/16-2) and KIT is gratefully acknowledged. DR thanks the GRK 1626 “Chemical photocatalysis

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• is initiated through triplet-sensitization of xanthates by the long-lived triplet state of the iridium-based photocatalyst. Keywords: energy transfer; olefin; photocatalysis; radical; xanthate; Introduction A degenerative radical transfer of xanthates to olefins has been developed as a robust

• ]. Based on these backgrounds, we wondered if the degenerative transfer of xanthates onto olefins could be facilitated by visible-light photocatalysis under milder reaction conditions. We therefore commenced our investigation with the reaction of ethyl ethoxycarbonylmethyl xanthate (1a) and 1-octene (2a

• rate was observed compared to the optimal reaction conditions (Table 1, entry 9). In principle, visible-light-mediated photocatalysis can serve for electron transfer (for either oxidation or reduction) and/or for energy transfer. We found that the reduction potential Ep/2 of xanthate 1a is −1.78 V vs

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• oxide photoredox catalysts have been also developed but not for polymer applications [65]. Iron oxide can offer the same advantages than TiO2 but with a lower gap between its HOMO and its LUMO which enable visible light excitation and thus, wide applications in heterogeneous photocatalysis for example

• allow access to unique chemistries such as photocatalysis at different wavelength or photoconductivity for example [76]. Moreover, they can be characterized by lower costs. For examples, methylene blue or eosin-Y are examples of widespread photoredox catalytic dyes [18]. There is a wide range of

Photocatalyic Appel reaction enabled by copper-based complexes in continuous flow

• Clémentine Minozzi,
• Jean-Christophe Grenier-Petel,
• Shawn Parisien-Collette and
• Shawn K. Collins

Beilstein J. Org. Chem. 2018, 14, 2730–2736, doi:10.3762/bjoc.14.251

• anhydrides. The protocol was also amendable and optimized under continuous flow conditions. Keywords: Appel; continuous flow; copper; halides; photocatalysis; Introduction Synthetic photochemistry and photocatalysis continues to influence molecular synthesis [1][2][3][4]. In exploring photochemical

• organic halide from the corresponding alcohol (Figure 1) [6][7]. The Appel reaction is representative of a host of transformations that require stoichiometric reagents to effect a functional group change of an alcohol. In 2011, Stephenson and co-workers reported that photocatalysis could be used to

• adapted to continuous flow using purple LED reactors. The batch and continuous flow processes were all made possible due to the ability to screen highly modular copper-based complexes for photocatalysis. Alcohol→bromide functional group transformations. Ligands used in the library generation of

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• . Keywords: arenes; oxidation; photocatalysis; thiolation; visible light; Introduction The generation of carbon–sulfur bonds is an important task in organic synthesis, because of their abundance in target structures, such as natural products and drugs [1][2][3]. They are found in organic semiconductors

Bioinspired cobalt cubanes with tunable redox potentials for photocatalytic water oxidation and CO₂ reduction

• Zhishan Luo,
• Yidong Hou,
• Jinshui Zhang,
• Sibo Wang and
• Xinchen Wang

Beilstein J. Org. Chem. 2018, 14, 2331–2339, doi:10.3762/bjoc.14.208

• Zhishan Luo Yidong Hou Jinshui Zhang Sibo Wang Xinchen Wang State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou 350002, China 10.3762/bjoc.14.208 Abstract The development of efficient, robust and earth-abundant catalysts for

• reactions. Keywords: CO2 reduction; cobalt cubane; photocatalysis; water oxidation; water splitting; Introduction The direct conversion of solar energy into chemical fuels (e.g., H2, CO and hydrocarbons) through water splitting and carbon fixation reactions is a sustainable solution to environmental

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• structural characteristic of peptides is the disulfide bridge formed by cysteines. This functional group is much more prevalent in peptide medicinal chemistry. Noël et al. have published a protocol for the aerobic oxidation of thiols to disulfides, using Eosin Y photocatalysis and TMEDA (Scheme 3) [43]. The

• , benzothiophenes and benzimidazoles seen in many drugs. In another demonstration of the value of diazonium salts, the König group have published a protocol for the synthesis of substituted benzothiophenes using Eosin Y photocatalysis, starting from o-methylthioarenediazonium salts and substituted alkynes (Scheme

• benzofused heterocycles (indole etc.) – such as benzimidazoles or tetrazolopyridines are often seen in medicinal chemistry. Singh et al. reported a method for preparing 3-arylnitrobenzimidazoles from 2-aminopyridines and nitroalkanes, using green LED Eosin Y photocatalysis, with molecular oxygen as the

Graphitic carbon nitride prepared from urea as a photocatalyst for visible-light carbon dioxide reduction with the aid of a mononuclear ruthenium(II) complex

• Kazuhiko Maeda,
• Daehyeon An,
• Ryo Kuriki,
• Daling Lu and
• Osamu Ishitani

Beilstein J. Org. Chem. 2018, 14, 1806–1812, doi:10.3762/bjoc.14.153

• phase. Keywords: artificial photosynthesis; heterogeneous photocatalysis; hybrid material; metal complexes; solar fuels; Introduction Carbon nitride is one of the oldest synthetic polymers [1], and has several allotropes. Among them, graphitic carbon nitride (g-C3N4) is the most stable form and is an

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• including photocatalysis [6], bio-imaging [7][8], and solar-energy conversion [9], just to cite a few. Thompson and Forrest reported in 1998 on the first example of a phosphorescent emitter, namely 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (Pt(OEP)), used as dopant for the fabrication of

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• . General concepts, synthetic strategies and the substrate scope of reactions yielding thiols, disulfides, sulfoxides, sulfones and other organosulfur compounds are discussed together with the proposed mechanistic pathways. Keywords: disulfides; photocatalysis; sulfones; sulfoxides; thiols; visible light

• conditions. The key concepts of photocatalysis and photoredox-catalyzed reactions for carbon–carbon and carbon–heteroatom (C–X) bond formation have been reviewed in detail. However, several new photocatalytic methods for the formation of carbon–sulfur (C–S) bonds were recently reported and we aim to

Mechanochemical borylation of aryldiazonium salts; merging light and ball milling

• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1463–1469, doi:10.3762/bjoc.13.144

• –solvent charge-transfer complex formation. Keywords: aryldiazonium salts; borylation; eosin Y; mechanochemistry; photocatalysis; Introduction The use of mechanical force to process materials or to induce chemical transformations is perhaps as old as the history of mankind itself [1]. Similarly, from

• underexplored [14], despite photocatalysis could clearly benefit from the excellent mixing under neat or liquid-assisted grinding (LAG) [15] conditions. Additionally, in contrast to solution-based methods, reactions by milling do not suffer from solubility restrictions due to the possibility to bring reactants

Photocatalyzed synthesis of isochromanones and isobenzofuranones under batch and flow conditions

• Manuel Anselmo,
• Lisa Moni,
• Hossny Ismail,
• Davide Comoretto,
• Renata Riva and
• Andrea Basso

Beilstein J. Org. Chem. 2017, 13, 1456–1462, doi:10.3762/bjoc.13.143

• ; photocatalysis; photo-Meerwein arylation–addition; Introduction Photoinduced multicomponent reactions are currently receiving remarkable attention [1]. Indeed, the possibility to obtain multiple-bond forming reactions under clean and mild conditions is nowadays one of the main targets of green chemistry

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• ]. Contribution of continuous-flow metal-, organo-, and photocatalysis in green chemistry The development of continuous-flow catalysis is appealing because it combines the advantages of a catalytic reaction with the benefits of flow microreactors. Under homogeneous conditions a soluble catalyst, which flows

• batch mode [61]. Pericàs and co-workers taking advantage of the high catalytic activity, robustness and recyclability of the supported catalyst, performed also straightforward gram synthesis of target compounds. In the context of photocatalysis and oxidations using flow microreactors [62][63], Noël

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants

• Tamás Zoltán Agócs,
• István Puskás,
• Erzsébet Varga,
• Mónika Molnár and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2016, 12, 2873–2882, doi:10.3762/bjoc.12.286

• , Hungary 10.3762/bjoc.12.286 Abstract Advanced oxidation processes (AOPs) are considered highly competitive water treatment technologies for the removal of organic pollutants. Among AOP techniques, photocatalysis has recently been the most widely studied. Our aims were to investigate how the dispersion of

• cyclodextrin polymer (CDP) using KMnO4 [19]. Advanced oxidation processes (AOPs) based on in situ generation of highly reactive species can mineralize organic contaminants into relatively harmless compounds. Research activities have been recently focused on photocatalysis belonging to these AOP techniques [20

Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst

• Martin Obst and
• Burkhard König

Beilstein J. Org. Chem. 2016, 12, 2358–2363, doi:10.3762/bjoc.12.229

• reaction mixture. The corresponding carbonyl compounds were obtained in moderate to good yields. Keywords: benzylic alcohol; oxidation; photocatalysis; solvent free; visible light; Introduction According to a classification made by Wilhelm Ostwald, one of the pioneers in the field of physical chemistry

• for mechanochemical syntheses include stoichiometric reactions such as the Knoevenagel condensation and the Wittig reaction, but also reactions catalyzed by metal catalysts, like the Sonogashira coupling and the Suzuki coupling [1]. Photocatalysis, as a part of Ostwald’s sub-discipline photochemistry

• , is a rather new field of great academic interest. Namely, visible-light photocatalysis applying an organic, redox-active catalyst allows mild and efficient transformations. By exciting the photocatalyst, which then exchanges electrons with the substrate, light energy is converted into chemical energy

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

• Josef Schachtner,
• Patrick Bayer and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170

• standard batch reactions at 10−4–10−2 M concentrations of the dye so that large volumes of the reaction remain in the dark [9][52]. It is important to note that the magnitude of attenuation coefficients of the employed chromophores is a key difference between the recently emerging field of photocatalysis

• ). Conversion vs substrate concentration.a Residence time and conversion with different light sources.a Supporting Information Supporting Information File 446: Experimental. Acknowledgements We gratefully acknowledge financial and intellectual support from the Graduate School on Chemical Photocatalysis of the

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• ; organic synthesis; photocatalysis; titania; Introduction Synthetic chemistry is the springboard into innovative new products and materials for improving the wellbeing of society. In this context discovering cleaner, greener, more environmentally friendly preparative chemical methods has grown to an

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation

• Martin Weiser,
• Sergej Hermann,
• Alexander Penner and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2015, 11, 568–575, doi:10.3762/bjoc.11.62

• different electron density. Representative mesoflow reactor experiments allowed to significantly shorten the irradiation times and to use sunlight as “green” light source. Keywords: electron transfer; perylene bisimide; photocatalysis; photochemistry; pyrene; Introduction Photocatalysts are organic or

• derivatives by photocatalysis. The regioselectivity – Markovnikov or anti-Markovnikov – can simply be controlled by the chosen photocatalyst, either Py or 1,7-dicyanoperylene-3,4:9,10-tetracarboxylic acid bisimide (PDI). Results and Discussion Photocatalytic complementarity The photocatalytic complementarity

• cycle of this process, and subsequent nucleophilic attack accompanied by deprotonation gives the Markovnikov-type addition product. Reductive route: Markovnikov regioselectivity For the reductive mode of photocatalysis towards the Markovnikov-oriented addition products, we recently applied Py as

An improved procedure for the preparation of Ru(bpz)₃(PF₆)₂ via a high-yielding synthesis of 2,2’-bipyrazine

• Danielle M. Schultz,
• James W. Sawicki and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9

• ; palladium; photocatalysis; reductive coupling; Findings Visible light-photoredox catalysis using transition metal chromophores is rapidly becoming recognized as an important strategy in organic synthesis [1][2][3][4][5]. This approach towards reaction design enables the facile generation and exploitation

• , we have developed an improved, Pd-catalyzed method for the synthesis of 2,2’-bipyrazine, an important ligand with growing utility in the context of visible light photocatalysis. This method is readily scalable to enable the gram-scale preparation of 2,2’-bipryazine, which facilitates the preparative

An integrated photocatalytic/enzymatic system for the reduction of CO₂ to methanol in bioglycerol–water

• Michele Aresta,
• Angela Dibenedetto,
• Tomasz Baran,
• Antonella Angelini,
• Przemysław Łabuz and
• Wojciech Macyk

Beilstein J. Org. Chem. 2014, 10, 2556–2565, doi:10.3762/bjoc.10.267

• , such reduction would require implementation of the most energetically and economically convenient technologies, such as visible-light-driven photocatalysis, as chemical methods are either too expensive or not compatible with the enzymes [7]. To date, photocatalysis has shown great potential for

• photodegradation of environmental pollutants [8][9]. Most interesting is that photocatalysis may play a relevant role in the conversion of large quantities of CO2 into fuel by using water or waste organics as the hydrogen source [7][10][11]. Therefore, integrated photochemical CO2 reduction/organic oxidation and

• line), and of 1,4-NADH formed from NAD+ upon photocatalysis in the absence (blue) and the presence (green) of the Rh-complex as a mediator and [CrF5(H2O)]2−@TiO2 as a photocatalyst. Photocurrent generated at the [CrF5(H2O)]2−@TiO2 electrode as a function of the wavelength of the incident light