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

• found that the employment of the less reducing Ir catalysts 7 [46] and 8 [47] also worked for the process (Table 1, entries 2 and 3). Especially, the rather oxidizing [Ir{dF(CF3)ppy}2(dtbpy)](PF6) (8) resulted in full conversion of 1a, affording 3aa in 89% yield (Table 1, entry 3). Other photocatalysts

• feasible. In contrast, the triplet energy ET of xanthate 1a was estimated as 57.5 kcal/mol by DFT calculation, that is close to those of photocatalysts 7 and 8 (ET = 60.1 kcal/mol [50]), indicating that the process could be initiated by the triplet sensitization pathway [51][52]. This assumption is in

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

• of sectors such as coatings, adhesives, paints, inks, composites, 3D-printing, dentistry, data storage ... [5][6][7]. Review 1 Photopolymerization processes and uses of photocatalysts (PCs) Traditionally, polymer manufacturing is made through thermal curing. However, this route has many limitations

• , respectively, gathered in Table 10 and Table 11. Additives used for both free radical polymerization and cationic polymerization are discussed in Section 1 and depicted in Scheme 1. Photocatalysts mentioned in Table 10 and Table 11 are the ones described in Section 2 and depicted in Scheme 2 and Scheme 4. To

• . The photopolymerization performance of the free radical polymerization using photoredox catalysis is presented in Table 10 and for cationic polymerization in Table 11. As observed in Table 10, all photocatalysts presented before lead to a free radical polymerization. The first interesting property 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

• ][12][13][14], mild reaction conditions and visible-light irradiation), which should be easily embraced by the synthetic community. To further develop the photochemical alcohol→halide transformation, the use of alternative photocatalysts based upon more abundant metals was envisioned [15][16][17][18

• ]. Specifically, our group has demonstrated that heteroleptic Cu(I) complexes [19][20][21] have significant potential as photocatalysts that can promote a variety of mechanistically distinct photochemical transformations including single electron transfer (SET), energy transfer (ET), and proton-coupled electron

• UV–vis absorption characteristics of the photocatalysts [28]. Stephenson and co-workers had previously reported that a primary alcohol structurally similar to 1 underwent conversion to the corresponding bromide in 96% yield upon irradiation in the presence of Ru(bpy)3Cl2 (1 mol %). The screening for

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

• SCE. Other photocatalysts like Ru(bpy)3Cl2, Ru(bpz)3PF6, DDQ, acridinium dyes, Eosin Y, Eosin Y disodium salt and 4-CzIPN were evaluated, but under our reaction conditions either low substrate conversion or the degradation of the photocatalyst was observed (see Supporting Information File 1, Table S1

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

• value of these methods to medicinal chemistry is considered. An overview of the general characteristics of the photocatalysts as well as some electrochemical data is presented. In addition, the general reaction mechanisms for organocatalysed photoredox transformations are discussed and some individual

• mechanistic considerations are highlighted in the text when appropriate. Keywords: C–H functionalisation; heterocycles; late-stage functionalisation; medicinal chemistry; organic dyes; organic photocatalysts; peptide chemistry; photoredox catalysis; Review 1 Introduction 1.1 Main advantages of

• ) components than traditional reactions. Organocatalysed photoredox catalysis combines the advantages of both these fields. Thus, it is not only a new field filled with exciting discoveries, but also is sustainable and beneficial in the long term. 1.2 General characteristics of photocatalysts 1.2.1 Brief

Recent advances in materials for organic light emitting diodes

• Eli Zysman-Colman

Beilstein J. Org. Chem. 2018, 14, 1944–1945, doi:10.3762/bjoc.14.168

• (LEECs), two types of electroluminescent devices; (ii) sensing materials employed in electro-chemiluminescence; and (iii) photocatalysts employed in photoredox catalytic reactions.

Visible light-mediated difluoroalkylation of electron-deficient alkenes

• Vyacheslav I. Supranovich,
• Vitalij V. Levin,
• Marina I. Struchkova,
• Jinbo Hu and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2018, 14, 1637–1641, doi:10.3762/bjoc.14.139

• addition step cannot be oxidized by photocatalysts. Herein we report a convenient method for performing hydroperfluoroalkylation of electron-deficient alkenes employing iodides 1 mediated by visible light. The reaction proceeds without the use of a photosensitizer or a photocatalyst. Generation of

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• photocatalysts, metal-free methods also have made tremendous advance. For trifluoromethylation of prefunctionalized substrates, these developments have expanded the substrate scope and provided milder conditions, but this field still suffered from limited and expensive trifluoromethylation reagents. Moreover

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

• sulfoxide. Different aryl thiols were reacted with aliphatic and aromatic alkenes, showing a reasonable functional group tolerance. In 2015, the group of Greaney substituted the transition metal photocatalysts by titanium dioxide (TiO2) nanoparticles (Scheme 7) [37]. Photoexcitation of electrons to the

• Ananikov and co-workers (Scheme 9) [39]. Their aim was to develop a photocatalytic method that is applicable for the industrial synthesis of pharmaceuticals or bioactive compounds. Using metal-based photocatalysts may leave traces of metal impurities in the crude product causing elaborative purification

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• were obtained for styrene derivatives, although with a subsequent dehydrochlorination step. If the nature of the substrate undoubtedly played an important role in the reaction process, it was also the case of the catalyst. Indeed, the use of other usual photocatalysts such as [Ru(bpy)3]Cl2, [Ir(ppy)2

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• presence of an iridium photoredox catalyst as reported by Zhu, Zhang and co-workers [41]. Of the photocatalysts tested, Ir[dF(CF3)ppy]2(dtbbpy)PF6 had appropriate redox potentials and gave the best results. A wide range of terminal alkenes featuring several functional groups reacted with exclusive anti

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• systems [69] such as solar cell materials as well as photocatalysts for organic reactions. A phthalocyanine dimer in which TFEO-Pcs are directly linked by C–C bonds has been reported (Scheme 4) [70][71]. This homodimer was synthesized by a palladium-catalyzed homo-coupling reaction of two A3B type

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

• the photodimerizations of olefins by manual grinding of the reactants followed by long UV-light exposure [10], or by vortex grinding [11]. However, until now, studies of photocatalyzed mechanochemical reactions involving, for example, metal complexes [12] or organic photocatalysts (PC) [13] has been

• ] and, more important, the exploration of new photomechanochemical organic reactions, where solubility constrains caused by working with low-soluble photocatalysts, substrates or products can be bypassed by mechanochemical means. (a) Cartoon representing the merging of light and mechanical energy. (b

Chemoselective synthesis of diaryl disulfides via a visible light-mediated coupling of arenediazonium tetrafluoroborates and CS₂

• Jing Leng,
• Shi-Meng Wang and
• Hua-Li Qin

Beilstein J. Org. Chem. 2017, 13, 903–909, doi:10.3762/bjoc.13.91

• 0.5 equiv, the yield of the product 3a dropped to 42%, whereas increasing amounts of CS2 did not significantly increase the yield of the product. Subsequently, different photocatalysts were investigated and it turned out that the choice of catalyst also had a significant impact on our model reaction

• . Ru(bpy)3Cl2 catalyzed this coupling to afford the desired product 3a in a moderate yield of 65% (Table 3, entry 8). However, when the iridium-based photocatalysts Ir(ppy)3 [24], [Ir(ppy)2(bpy)]PF6 and [Ir(ppy)2(dtbbpy)]PF6 (bpy = 2,2’-bipyridine, ppy = 2-phenylpyridine, dtbbpy = 4,4’-di-tert-butyl

• Screening of the solvents and sulfur sources for the visible light-mediated coupling of benzenediazonium tetrafluoroborate (1a) and CS2 (2) and other sulfur sources in the presence of Ru(bpy)3(PF6)2 as the photocatalyst.a Screening of photocatalysts for the visible light-mediated coupling of

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

• residence time. Noël optimized, for the first time, a trifluoromethylation of aromatic heterocycles by continuous-flow photoredox catalysis. The process benefited from the use of microreactor technology and readily available photocatalysts. The process was also employable for perfluoroalkylation. The

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

• decomposition [27][28]. Recently, various photocatalysts modified by CDs have been described. For instance, reduced graphene oxide/β-CD/titanium dioxide showed enhanced removal of phenol and Cr(VI) [29], graphene nanosheets with self-assembled nanolayer of TiO2 stabilized by β-CD resulted in improved

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

• solvent-free photocatalysis is the application of heterogeneous, semiconducting photocatalysts, often based on titanium dioxide and other metal oxides [6][7][8]. However, to the best of our knowledge, no solvent-free visible-light driven transformation of a solid substrate applying an organic

• flavin derivatives in general are well-known blue-light absorbing photocatalysts, which can oxidize a variety of substrates under aerobic conditions with oxygen as terminal oxidant. Flavins were studied extensively for the oxidation of alcohols, amines, methylbenzenes, styrenes, and phenylacetic acids [9

Biocatalysis for the application of CO₂ as a chemical feedstock

• Apostolos Alissandratos and
• Christopher J. Easton

Beilstein J. Org. Chem. 2015, 11, 2370–2387, doi:10.3762/bjoc.11.259

• approach utilised photocatalysts to generate electrons from solar energy, which in turn were donated for the production of methanol [137]. Though methanol yields and catalyst efficiencies are low, these results are highly promising for the future development of biochemical systems for the solar-driven

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

• light sources, the research field of photoredox catalysis has tremendously grown over the past decade [1][2][3][4][5][6][7]. Transition metal complexes, mainly [Ru(bpy)3]2+ [7], were most often used as photocatalysts, whereas the potential of organic compounds and dyes has not yet been fully exploited

Eosin Y-catalyzed visible-light-mediated aerobic oxidative cyclization of N,N-dimethylanilines with maleimides

• Zhongwei Liang,
• Song Xu,
• Wenyan Tian and
• Ronghua Zhang

Beilstein J. Org. Chem. 2015, 11, 425–430, doi:10.3762/bjoc.11.48

• capable of catalyzing a broad range of useful reactions. A variety of new methods have been developed to accomplish known and new chemical transformations by means of these transition metal-based photocatalysts so far. However, the ruthenium and iridium catalysts usually are high-cost, potentially toxic

• and not sustainable. Similar to the redox properties of these organometallic complexes, some metal-free organic dyes such as Eosin Y, Rose Bengal, Fluorescein, and Methylene Blue, have shown superiority of their applications as photocatalysts, which are easy to handle, environmentally friendly

• light (two 9 W blue LEDs) at room temperature. Gratifyingly, the desired product tetrahydroquinoline 3a was obtained in 82% yield after 18 h (Table 1, entry 1). We screened a number of metal-free organic dyes for photocatalysts. Of the dyes screened, Eosin Y showed the highest efficiency (Table 1, entry

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

• -absorbing photocatalysts for synthetic applications. Among the most attractive features of this approach is the availability of many known complexes with well-characterized photophysical and electrochemical properties. In particular, Ru(bpz)32+ is a powerful photooxidant that has proven to be uniquely

• )32+) [10] has emerged as one of the most useful transition metal photocatalysts for oxidatively induced organic transformations (Figure 1). Due to the electron-deficient nature of its bipyrazyl ligands, the excited state redox potential of 2 is quite positive (+1.45 V vs SCE) [11]. Consequently, it

One-pot functionalisation of N-substituted tetrahydroisoquinolines by photooxidation and tunable organometallic trapping of iminium intermediates

• Joshua P. Barham,
• Matthew P. John and
• John A. Murphy

Beilstein J. Org. Chem. 2014, 10, 2981–2988, doi:10.3762/bjoc.10.316

• ). Alternatively, the α-amino radicals can be trapped by electrophiles [7][8][9]. Oxidative C–H functionalisation of THIQs is reported using Cu(I) [10][11], Fe(III) [12], V(IV) [13] and I2 [14][15] catalysts, but also with heterogeneous [16], metal-organic [17][18] and organic [19][20] photocatalysts. Such

• tertiary amine substrates and unstabilised carbon nucleophiles. Recently, visible-light photoredox catalysis has gained interest as a technique for oxidative functionalisation [34][35]. An important feature of photoredox catalysis is that different photocatalysts have different redox potentials upon

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

• . For the approach discussed here, the production of one mol of CH3OH from CO2 requires three enzymes and the consumption of three mol of NADH. Regeneration of the cofactor NADH from NAD+ was achieved by using visible-light-active, heterogeneous, TiO2-based photocatalysts. The efficiency of the

• H2O splitting have received significant interest due to their potential environmental and resource preservation benefits [12][13]. Interestingly, the oxidized forms of some common waste organics may find practical application. The use of heterogeneous photocatalysts in the process of NADH regeneration

• ]. Additionally, the properties of other photocatalysts (Cu2O, InVO4, and TiO2, which are less active than the Cr-modified TiO2 photocatalysts), which were modified with the organic compound “rutin”, are briefly presented. Figure 2 shows the transformed diffuse reflectance spectra of the photocatalysts converted

Visible light photoredox-catalyzed deoxygenation of alcohols

• Daniel Rackl,
• Viktor Kais,
• Peter Kreitmeier and
• Oliver Reiser

Beilstein J. Org. Chem. 2014, 10, 2157–2165, doi:10.3762/bjoc.10.223

• substitution pattern of benzoates we intended to shift the electrochemical reduction potentials of the substances into a region that could be accessed by common visible light photocatalysts. The substituents should be as inert as possible in order not to interfere with the photochemical reaction itself

• ; dtb-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine] as photocatalysts, Hantzsch ester (diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate) as hydrogen donor, and iPr2NEt as sacrificial electron donor in DMF (Scheme 3). Light generated from a high power LED was channeled into the reaction solution in

• monobenzoate 6e. Reduction of benzoate moiety in case of non-benzylic alcohols. Optimized conditions for larger scale applications. Comparison of different esters and photocatalysts in deoxygenation reaction. Solvent/temperature dependence and control experiments of deoxygenation reaction with 3,5-bis

Visible-light photoredox catalyzed synthesis of pyrroloisoquinolines via organocatalytic oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade with Rose Bengal

• Carlos Vila,
• Jonathan Lau and
• Magnus Rueping

Beilstein J. Org. Chem. 2014, 10, 1233–1238, doi:10.3762/bjoc.10.122

• recently Zhao reported the same reaction using C60-Bodipy hybrids [30] and porous material immobilized iodo-Bodipy [31] as photocatalysts, obtaining in both cases good yields for different pyrrolo[2,1-a]isoquinolines. Finally, Lu presented in 2013 a dirhodium complex for the synthesis of these compounds