CO₂ Chemistry

• Thomas E. Müller and
• Walter Leitner

Beilstein J. Org. Chem. 2015, 11, 675–677, doi:10.3762/bjoc.11.76

• fixation of CO2, which can be applied in the synthesis of carboxylic acids [8]. Also highly interesting is the combination of enzymatic and photocatalytic approaches for activating CO2 [9]. Bifunctional catalyst systems are frequently needed and well-understood in the synthesis of cyclic carbonates [10

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

• additive. Photocatalytic additions of a variety of alcohols gave the corresponding products in good to excellent yields. The proposed photocatalytic electron transfer mechanism was supported by detection of the PDI radical anion as key intermediate and by comparison of two intramolecular reactions with

• [8]. The way towards a really complete organo-type photoredox catalysis has mainly been established for eosin Y as an important alternative for [Ru(bpy)3]2+ [9]. Photocatalytic nucleophilic additions of amines and alcohols to olefins, especially styrenes, became an increasingly important task due to

• /70s, and Lewis identified exciplex states as key intermediates [13][14]. The corresponding photohydration worked only if the aromatic olefins as starting material were directly excited by UV light [15][16]. The first approach towards a photocatalytic version of this type of reaction came from Arnold

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

• properties of these complexes is well understood [6][7][8]. As a result, a variety of Ru and Ir based chromophores spanning a range of redox potentials have recently become widely utilized in the design of new photocatalytic transformations [9]. In particular, the homoleptic tris(bipyrazyl) complex 2 (Ru(bpz

Visible-light-induced bromoetherification of alkenols for the synthesis of β-bromotetrahydrofurans and -tetrahydropyrans

• Run Lin,
• Hongnan Sun,
• Chao Yang,
• Youdong Yang,
• Xinxin Zhao and
• Wujiong Xia

Beilstein J. Org. Chem. 2015, 11, 31–36, doi:10.3762/bjoc.11.5

• alkenols with CBr4 as the bromine source, utilizing visible-light-induced phototedox catalysis. The reaction proceeds with high efficiency and regioselectivity for the synthesis of β-bromotetrahydrofurans and -tetrahydropyranes. Experimental General procedure for the photocatalytic bromoetherification of

• bromoethrification of alkenols. Proposed mechanism for the photocatalytic bromoetherification of alkenols. Survey on the photocatalytic bromoetherification of alkenols. Photocatalytic bromoetherification of butenols.a Photocatalytic bromoetherification of pentenolsa. Supporting Information Supporting Information

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

• , 70126 Bari, Italy Department of Chemistry, University of Bari, Via Orabona 4, 70125 Bari, Italy Faculty of Chemistry Jagiellonian University Ingardena 3, 30-060 Kraków, Poland 10.3762/bjoc.10.267 Abstract A hybrid enzymatic/photocatalytic approach for the conversion of CO2 into methanol is described

• gap energy of 3.2 eV (which is not compatible for use with visible light), modified TiO2 is known to be more suitable for carrying out photocatalytic processes utilizing the visible part of the solar spectrum [17]. In previous work, systems based on stable, encapsulated enzymes [7] for the enzymatic

• , and the in situ photocatalytic reduction of NAD+ to NADH under visible-light irradiation, using semiconductors in water/bioglycerol mixtures. Bioglycerol is being produced in increasing volumes for bio-diesel production from oleaginous seeds. New applications for this product are being investigated [7

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

• examples of lamellarin alkaloids. Photocatalytic metal free construction of pyrrolo[2,1-a]isoquinolines. Evaluation of the substrate scope. Evaluation of the substrate scope with activated alkynes. Optimization of the reaction conditions.a Supporting Information Supporting Information File 56

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• visible region and appropriate redox activity in the excited states. Many potent photoredox catalysts with sufficient long-term stability are transition metal complexes with excited MLCT states that can be generated in the visible. Another important group of photocatalytic active compounds are

• the homogeneous catalytic titanium species The original protocol for photocatalytic hydroxymethylation involves titanium tetrachloride in methanol as the reactive catalyst/donor mixture and carbonyl compounds as the acceptor components. During the exothermic dissolution process of TiCl4 in methanol

Direct C–H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis

• Ren Tomita,
• Yusuke Yasu,
• Takashi Koike and
• Munetaka Akita

Beilstein J. Org. Chem. 2014, 10, 1099–1106, doi:10.3762/bjoc.10.108

• CF3-substituted alkenes via direct Calkenyl–H trifluoromethylation. 1,1-Di- and trisubstituted alkenes were applicable to this photocatalytic system, providing the corresponding multisubstituted CF3-alkenes. In addition, use of an excess amount of the CF3 source induced double C–H trifluoromethylation

• trifluoromethylating reagents (+CF3) can serve as more efficient CF3 radical sources under mild photocatalytic reaction conditions. In addition, the putative β-CF3 carbocation intermediate formed through SET photoredox processes is playing a key role in our reaction systems (vide infra). Trifluoromethylated alkenes

• trisubstituted alkenes (Scheme 3c). Herein we disclose a highly efficient direct C–H trifluoromethylation of di- and trisubstituted alkenes with easy-handling and shelf-stable Umemoto’s reagent 1a by visible-light-driven photoredox catalysis under mild conditions. This photocatalytic protocol allows us easy

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• discussed on the basis of pH, solvent polarity, lamp type, absorption properties, and quantum yields. Determination of the latter proved to be an especially valuable tool for the distinction between radical chain and photocatalytic reactions. Keywords: mechanism; organocatalysis; photocatalysis; photoredox

• visible range of the solar spectrum have been demonstrated to catalyze light-driven organic reactions. The use of the pyridyl-based complexes [Ru(bpy)3]2+, [Ir(ppy)3] and [Ir(ppy2)(dtbbpy)]+ for the mediation of redox processes has certainly attracted the most interest, incipiently in photocatalytic

• no appreciable absorption at this wavelength. However, the addition of minor quantities of base (TBAOH) to the reaction mixture resulted in strong absorption at 535 nm and good photocatalytic activity under irradiation. The substitution of acetonitrile with DMSO in the same reaction gave strong

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• kinetics occuring in so called photocatalytic systems. The simple kinetic model used is enough to outline the benefit of the cyclic system and to give the basic requirements in term of chemical combination needed to be fulfilled in order to obtain a photocatalytic behavior. Keywords: computation; electron

• responsible for the higher efficiency of PCIS [9][31][53][54][55] in photopolymerization reactions. Therefore, as the dye is regenerated during the photochemical reaction, a catalytic behavior appears, leading to the so-called photocatalytic system. In this paper an experimental and mechanistic study of Type

• II PIS will be given and compared with a PCIS. Then, in order to improve the knowledge of PCIS, a thermodynamic and mechanistic approach of PCIS exhibiting an ideal photocatalytic behavior will be presented. The proposed scheme will be used as model to run some computation. This will permit to

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• anion. Later on, other amines (N,N-diisopropylethylamine, N,N-dimethylformamide) and bromides (ethyl 2-bromoisobutyrate, benzyl bromide) were proposed for the photocatalytic radical polymerization of various methacrylates [53]. Ir complexes can also be used. As only carbon centered radicals can be

Visible-light photoredox catalysis enabled bromination of phenols and alkenes

• Yating Zhao,
• Zhe Li,
• Chao Yang,
• Run Lin and
• Wujiong Xia

Beilstein J. Org. Chem. 2014, 10, 622–627, doi:10.3762/bjoc.10.53

• the optimized conditions in hand, we prepared a variety of phenols which were subjected to the photocatalytic reaction. In general, both electron-withdrawing and electron–donating groups were tolerated as substituents R2 in this process. Interestingly, the substrates protected with TMS (trimethylsilyl

• cyclohexane-1,3-dione (5) and (E)-4-(4-methoxyphenyl)but-3-en-1-ol (7) under the same reaction conditions led to 2,2-dibromocyclohexane-1,3-dione (6) and bromofuran compound 8 in 22% and 52% yield, respectively (Scheme 4). This outcome demonstrates the efficiency of the Ru(bpy)3Cl2/CBr4 photocatalytic system

• situ generation of bromine. Synthesis of dibromophenol product 2b''. Scope of the photocatalytic bromination of alkenes. Bromination of diketones and cyclization reactions. Survey of the photocatalytic bromination reaction conditions. Scope of the photocatalytic bromination of phenols. Supporting

Synthesis, characterization and initial evaluation of 5-nitro-1-(trifluoromethyl)-3H-1λ³,2-benziodaoxol-3-one

• Nico Santschi,
• Roman C. Sarott,
• Elisabeth Otth,
• Reinhard Kissner and
• Antonio Togni

Beilstein J. Org. Chem. 2014, 10, 1–6, doi:10.3762/bjoc.10.1

• directed towards the photocatalytic one-electron reduction of these compounds in order to generate the highly electrophilic trifluoromethyl radical [5][6][7]. For example, Gouverneur et al. have highlighted the regioselective allylic trifluoromethylation employing reagent 2, [Ru(bpy)3]Cl2 and allylsilanes

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• approach work, several hurdles need to be addressed. First, a labile carbon–metal bond is desired in order to have an efficient turnover of the metal. Second, the metal complex needs to be compatible with the strongly reducing intermediates (e.g., superoxide) produced in the photocatalytic cycle. Third

• and indoles are then added to the N-acyliminium ions 68b to provide the amidoalkylation products 69. Alternatively, the use of only persulfate at 55 °C afforded the same products. However, higher yields and better selectivities were generally observed with the photocatalytic process. Intercepted by

[3 + 2]-Cycloadditions of nitrile ylides after photoactivation of vinyl azides under flow conditions

• Stephan Cludius-Brandt,
• Lukas Kupracz and
• Andreas Kirschning

Beilstein J. Org. Chem. 2013, 9, 1745–1750, doi:10.3762/bjoc.9.201

• to perform many transformations that are hardly possible under thermal conditions. This includes photocatalytic reactions that have seen an immense interest lately [1]. Nitrile ylides 3 are 1,3-dipoles that have served for the preparation of different five-membered N-heterocycles in 1,3-dipolar

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• the photocatalytic oxidative activation of NHPI by graphitic carbon nitride (g-C3N4) and visible light irradiation [65]. g-C3N4, the most stable allotrope of carbon nitride, is a two-dimensional polymer with a tri-s-triazine ring unit and a π-conjugated layered structure similar to graphene. It is a

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

• Sofia Telitel,
• Frédéric Dumur,
• Thomas Faury,
• Bernadette Graff,
• Mohamad-Ali Tehfe,
• Didier Gigmes,
• Jean-Pierre Fouassier and
• Jacques Lalevée

Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101

• both Rp and conv are better when comparing to Py_3/MDEA. Photocatalyst behavior of the Co_Pys The photocatalytic behavior of the Co_Pys is investigated in the most interesting compounds reported above for the photopolymerization reactions. The steady-state photolysis of Py_3/PBr, Py_3/Iod, Py_3/MDEA

• , we have demonstrated the true occurrence of a unique oxidation cycle). Conclusion In this paper, the core-pyrene π structures Co_Pys appear as interesting photoinitiators. Successful cationic and radical photopolymerization reactions were carried out under near-UV–vis irradiation. A photocatalytic

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

• Maurizio Fagnoni,
• Stefano Protti,
• Davide Ravelli and
• Angelo Albini

Beilstein J. Org. Chem. 2013, 9, 800–808, doi:10.3762/bjoc.9.91

• aromatic compounds known to participate in photosubstitution or photocatalytic alkylation reactions. It was proposed to ascertain whether these may accumulate, as often observed in electrochemistry [33][34] and by pulse radiolysis [35], but rarely in photochemistry. Results The acceptors chosen for this

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• nanoparticles can effectively produce singlet oxygen when irradiated with LEDs in the oxidative degradation of 1,3-diphenylisobenzofuran [40]. Photocatalytic reactions Photocatalytic reactions are an area in which continuous flow can be particularly advantageous due to the large surface-to-volume ratio ensuring

• , thus, gave data ideally suited to mechanistic studies [56]. The potential of microreactors in the photocatalytic splitting of water has also come under investigation. In this case a rhodium-containing inorganic photocatalyst was employed, and again online QMS permitted mechanistic studies to be

Photochemistry with laser radiation in condensed phase using miniaturized photoreactors

• Elke Bremus-Köbberling,
• Arnold Gillner,
• Frank Avemaria,
• Céline Réthoré and
• Stefan Bräse

Beilstein J. Org. Chem. 2012, 8, 1213–1218, doi:10.3762/bjoc.8.135

• combinatorial flow chemistry in lab-on-a-chip applications. Photochemical processes are in this case particularly interesting because of their enhanced molecular activation [8]. Photochemistry in microreactors is an emerging research area [9], and especially photocatalytic reactions have been investigated in

Synthesis of new pyrrole–pyridine-based ligands using an in situ Suzuki coupling method

• Matthias Böttger,
• Björn Wiegmann,
• Steffen Schaumburg,
• Peter G. Jones,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2012, 8, 1037–1047, doi:10.3762/bjoc.8.116

• nine and thereby saturated. Our interest in this type of complex is driven by its potential analytical application for luminescence degradation measurements on photocatalytic surfaces [8]. Currently, β-diketonate complexes are in use for this analysis, but homoleptic complexes may be advantageous in

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• catalytic efficacy, flavin derivatives bearing a guanidinium ion as oxoanion binding site were prepared. Chromophore and substrate binding site are linked by a rigid Kemp’s acid structure. The molecular structure of the new flavins was confirmed by an X-ray structure analysis and their photocatalytic

• bonding site for oxoanions or carbonyl groups [45][46][47][48][49]. The structure of the new flavins was determined in solid state and in solution and their photocatalytic properties were tested. Results and Discussion Synthesis The synthesis of the potential photocatalysts 1 and 2, consisting of the

• bonds [54][55][56][57][58] and in solution the flavin chromophore is expected to rotate freely around the C–C single bonds of the ethane linker. Photocatalytic reactions Compounds 1 and 2 were tested as photocatalysts in three different reactions and their performance was compared to tetraacetyl

Photosonochemical catalytic ring opening of α-epoxyketones

• Hamid R. Memarian and
• Ali Saffar-Teluri

Beilstein J. Org. Chem. 2007, 3, No. 2, doi:10.1186/1860-5397-3-2

• carbonyl compounds [43][44][45][46][47][48][49][50] or by nucleophilic attack of appropriate reagents. [36][39][51] Recently, we have reported on the photocatalytic ring opening of α-epoxyketones 1a-f and 2,4,6-triphenylpyrilium tetrafluoroborate (TPT) as photocatalyst in methanol, [37] cyclohexanone, [38

• simultaneous irradiation of ultrasound and UV-light for catalytic ring opening of α-epoxyketones 1a-f in the presence of this photocatalyst in methanol. The main goal of the present work was to elucidate the effect of both irradiation sources separately or together on the rate of photocatalytic ring opening of

• of photocatalytic ring opening of α-epoxyketones 1b, 1d and 1f, the same substituents on the phenyl ring of the benzoyl group (1c and 1e) have a smaller effect. In the cases of 1b and 1d, the ratios of the diastereomeric photoproducts are inversed. We have proposed the involvement of three different