An azobenzene container showing a definite folding – synthesis and structural investigation

• Abdulselam Adam,
• Saber Mehrparvar and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

• chemistry. Here, we present the synthesis of a foldable container consisting of two different types of Lissoclinum macrocyclic peptides which are connected via two azobenzene units. The container is controllable by light: irradiation with UV light causes a switching process to the compact cis,cis-isomer

Reversible end-to-end assembly of selectively functionalized gold nanorods by light-responsive arylazopyrazole–cyclodextrin interaction

• Maximilian Niehues,
• Patricia Tegeder and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2019, 15, 1407–1415, doi:10.3762/bjoc.15.140

• reversibility of the switching behavior. The dispersion of AuNR assemblies after visible light irradiation can also be verified by TEM bright field images (Figure 4d) showing that the disassembly is possible without the combination of irradiation and sonication. This can be attributed to the favorable

• photostationary states of the AAP moiety in comparison to azobenzenes used in previous studies. Furthermore, dynamic light scattering was conducted to analyze the assembly in solution (Figure 5). The mean diameter increases upon dAAP addition from ca. 100 nm to ca. 230 nm. Upon UV-light irradiation, the mean

Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

• Ayato Yamada,
• Manabu Abe,
• Yoshinobu Nishimura,
• Shoji Ishizaka,
• Masashi Namba,
• Taku Nakashima,
• Kiyofumi Shimoji and
• Noboru Hattori

Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

• , at wavelengths of 710–760 nm and power of 700 mW. ESR spectra acquired during the photolysis of 2a (5 mM) in benzene using 365 nm light. Irradiation time-dependent decline in viability of LLC cells with compound 2a. Detection of intracellular ROS only in irradiated LLC cells with 2a-containing medium

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

• diphenyl diselenides 12 for the synthesis of 2-phenylseleny-3,3-diarylcyclobutenes 13 under visible light irradiation (Scheme 5) [51]. The desired products 13 contained a cyclobutene group and a selenium atom, which makes the products possess unique biological and pharmaceutical activities. The mechanism

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

• contradicts the use of visible light irradiation due to vanishing extinction coefficients at the edge to the visible region. To reach for high excited state reduction potentials and excite at rather long irradiation wavelengths an energetically high lying electronic groundstate potential has to be connected

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

• degenerative transfer of xanthates to olefins is enabled by the iridium-based photocatalyst [Ir{dF(CF3)ppy}2(dtbbpy)](PF6) under blue LED light irradiation. Detailed mechanistic investigations through kinetics and photophysical studies revealed that the process operates under a radical chain mechanism, which

• excited triplet state of 1a formed by direct 355 nm laser light excitation and triplet–triplet energy transfer involving the excited photocatalyst 8. To confirm the possibility of a direct photoexcitation of xanthate 1 using blue LED light irradiation as an alternative mechanism, a steady-state UV–vis

• ]. After irradiation of the mixture of xanthate 1a and olefin 2b under optimal reaction conditions with blue LED light irradiation for 4 h (Scheme 3), product 3ab was obtained in 58% yield. This is consistent with 12 equivalents of xanthate adduct 3ab produced per photon absorbed by the photocatalyst 8 (Φ

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

• : these processes are usually slow, expensive by requiring high temperature and high energy and release solvent (VOC). As an alternative of thermal polymerizations, polymerization upon light irradiation offers a good alternative. In both cases, polymerization occurs by the action of an initiating system

• interest in the past few decades. The development of photoredox catalysts is one of the major advances. 1.1 Photoinitiating system (PIs) Photoinitiated polymerization processes are polymerizations initiated by light irradiation. For that, a photoinitiator (PI) or a photoinitiating system (PIs) is mixed

• already found wide applications such as in water splitting, solar energy storage, proton-coupled electron transfer or photovoltaic for example [18]. 1.3 Electronic transitions involved into photoredox processes For selected photoredox catalysts, light irradiation has enough energy for the excitation 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

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• -phenylmalonate at −2.0 V vs Ag/AgCl yielded carboxylic ester migrated product as the major product. Conversely, the electrolysis of the substrate at −1.0 V vs Ag/AgCl through light irradiation, as well as at −1.5 V vs Ag/AgCl in the dark, yielded the simple reduced product and the phenyl migrated product. The

• iridium(III) complexes such as Irdfppy [112] are superior to [Ru(bpy)3]Cl2 in terms of their photosensitization abilities in visible-light-driven B12 catalytic systems (Scheme 9) [104]. This was probably due to the gradual decomposition of [Ru(bpy)3]Cl2 under visible light irradiation. This is consistent

• with the report by Yoon et al. in which light irradiation to Ru(bpy)32+ resulted in rapid decomposition during the photocatalytic reaction [113]. It was remarkable that a significantly high turnover number based on 1 (10,880) was obtained in the prolonged reaction with Irdfppy. Quenching experiments

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

• disulfides in the presence of catalytic amounts of [Ir(dF(CF3)ppy)2(dtbpy)]PF6 and (NH4)2S2O8 under blue light irradiation to yield arylthiols. The reaction proceeds at room temperature and avoids the use of prefunctionalized arenes. Experimental evidence suggests a radical–radical cross coupling mechanism

• (dtbpy)]PF6 as the photocatalyst. The reaction was carried out under nitrogen under visible-light irradiation at 455 nm. The oxidation potential of this test arene is 1.02 V vs SCE, which allows oxidation by [Ir(dF(CF3)ppy)2(dtbpy)]PF6 having an estimated excited state oxidation potential of 1.21 V vs

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• -redox catalyst under visible-light irradiation conditions [48]. Zhao and Wu reported the visible-light-driven hydrocarboxylation of alkynes in the presence of a Co catalyst [49]. The reaction of alkynes was carried out using CoBr2/dcype (dcype = bis(dicyclohexylphosphino)ethane) as catalysts in the

• et al. reported the Rh-catalyzed hydrocarboxylation of alkenes driven by visible-light irradiation conditions in the presence of a photoredox catalyst (Scheme 37) [75]. A model reaction using 4-cyanostyrene (40a) was carried out using iPrNEt2 as a sacrificial electron donor in the presence of [Ru(bpy

• )3](PF6)2 as a photoredox catalyst under visible-light irradiation (425 nm). Employing Rh(PPh3)3H as a catalyst, the desired hydrocarboxylated product 41a was obtained in 33% yield along with the formation of reduced product 42a. Rh(PPh3)3Cl and [Rh(PPh3)2Cl]2 were not efficient while a use of [Rh(P

Microfluidic light-driven synthesis of tetracyclic molecular architectures

• Javier Mateos,
• Nicholas Meneghini,
• Marcella Bonchio,
• Nadia Marino,
• Tommaso Carofiglio,
• Xavier Companyó and
• Luca Dell’Amico

Beilstein J. Org. Chem. 2018, 14, 2418–2424, doi:10.3762/bjoc.14.219

• light-irradiation, the highly reactive photoenol intermediate A' [7] and trapping of the latter by a competent electron-deficient reaction partner (Figure 1). The synthetic approach is not only restricted to electron-poor dienophiles such as maleimides B (see Figure 1a), but has also been implemented

• showed that in the absence of light irradiation, the cyclization product was not detected (Table 1, entry 6), confirming the photochemical nature of the present reaction. With the optimal reaction conditions in hand we next explored the generality and limitations of the photochemical transformation

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

• . Besides the CO2 reduction performance of the molecular complexes was evaluated by cooperation with a ruthenium photosensitizer Ru(bpy)32+ (bpy = 2’,2-bipyridine) with visible light irradiation [61][62][63][64][65][66][67]. As shown in Figure 5b, the activity of the CO2 reaction is reduced with the

• oxidation and (b) CO2 reduction. (c) Long-time course of water oxidation for 1-CN under UV–vis light irradiation (λ > 300 nm) in two recycling tests. (d) CO2 reduction for 1-OMe under visible light irradiation (λ > 420 nm) in four recycling tests. aWithout 1-R. Long-time course of water oxidation for 1-CN

• and Co2+ under UV–vis light irradiation (λ >300 nm). Supporting Information Supporting Information File 420: Additional data. Acknowledgements This work was financially supported by the National Key Technologies R & D Program of China (2018YFA0209301), the National Natural Science Foundation of

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

• such a mild and selective oxidation. MacMillan and co-workers have recently developed a method for the bioconjugation of peptides by radical decarboxylation of the C-terminus of peptides and subsequent Giese-type addition to Michael acceptors. This is performed under blue light irradiation, using

A self-assembled photoresponsive gel consisting of chiral nanofibers

• Lei Zou,
• Dan Han,
• Zhiyi Yuan,
• Dongdong Chang and
• Xiang Ma

Beilstein J. Org. Chem. 2018, 14, 1994–2001, doi:10.3762/bjoc.14.174

• and the chirality of the nanostructures could both be adjusted by subsequent light irradiation at different wavelengths. The helical nanofiber-like morphology was verified in the internal structure of the gel. The performance of this gel was investigated by a series of methods, such as UV–vis

• , whereby the equilibrium could be reached within 6 min and 4 min, respectively. However, the fatigue durability of this compound did not meet the expected requirement; after two cycles of light irradiation, the photoresponsiveness was clearly weakened. This defect may be ascribed to the rigid structure of

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

• capable of photocatalyzing CO2 reduction into formate with high selectivity under visible light irradiation, as confirmed by isotope tracer experiments with 13CO2 [8][9][10][11][12]. After the first report of a metal complex/C3N4 hybrid for CO2 reduction, several groups have presented similar reports

• W high-pressure Hg lamp (SEN) was used as a light source, in combination with a NaNO2 solution as a filter to provide visible light irradiation (λ > 400 nm). The gaseous reaction products were analyzed using a gas chromatograph with a thermal conductivity detector (GL Science, Model GC323). The

Synthesis and photophysical studies of a multivalent photoreactive Ru^II-calix[4]arene complex bearing RGD-containing cyclopentapeptides

• Sofia Kajouj,
• Lionel Marcelis,
• Alice Mattiuzzi,
• Adrien Grassin,
• Damien Dufour,
• Pierre Van Antwerpen,
• Didier Boturyn,
• Eric Defrancq,
• Mathieu Surin,
• Julien De Winter,
• Pascal Gerbaux,
• Ivan Jabin and
• Cécile Moucheron

Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150

• upon light irradiation. Two types of photooxidative damages can be induced: (i) by photosensitization of singlet oxygen and subsequent generation of highly reactive oxygen species (ROS) (type I photosensitization) or (ii) by direct oxidative electron transfer to biological molecules such as DNA or

• 500 ns after the laser pulse (gray, top) and 1 µs after the laser pulse in the presence of 10 mM GMP (purple, bottom). MALDI–MS analysis of a solution containing conjugate 9 and GMP after continuous light irradiation. In the inset, the experimental (bottom) and theoretical (top) isotope distributions

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• initiated by the decomposition of PIFA to form the trifluoroacetoxy radical under visible light irradiation [50]. Our approach for the generation of radical species for the benzylic carboxylation using a hypervalent iodine reagent relies on the unique reactivity of the hypervalent iodine(III)–bromine bond

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

• visible-light irradiation of the photoorganocatalyst. Aliphatic and aromatic thiols reacted with aliphatic olefins and styrene derivatives in high yields. Recently, additional procedures for the photoredox-catalyzed radical thiol–ene and thiol–yne reaction were reported. Xia and co-workers describe a

• . Carbon disulfide Formation of 1,3-oxathiolane-2-thiones In 2016, Yadav and co-workers reported a photoredox-catalyzed C–S bond formation with carbon disulfide (CS2) as starting material (Scheme 30) [65]. The reaction of CS2 with styrenes under visible-light irradiation and Eosin Y as organic

• enamides could not be reacted with sodium sulfinates to yield the respective products. Wang and co-workers described a new method for the cyclization of phenyl propiolates with sulfinic acids, generating valuable coumarin derivatives in 2015 (Scheme 44) [81]. Visible-light irradiation of Eosin Y allows the

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

• the presence of Eosin Y under visible light irradiation (Scheme 2) [9]. Acetophenone derivatives with various substitution patterns as well as aliphatic or heteroaromatic ketones were equally well tolerated. This methodology offered the advantage of minimising the chlorination side reaction

• visible light irradiation, a first SET reduction of CF3SO2Cl occurred, ultimately leading to the formation of the stabilised trifluoromethyl radical after releasing SO2 and chloride anion. This electron deficient radical was then added on the most electron-rich position of the arene substrate to yield

• -nitroalkenes with trifluoromethanesulfonyl chloride [39]. They found out that in the presence of the photocatalyst Eosin Y, under visible-light irradiation, such substrates could be selectively converted into (E)-1-trifluoromethylalkenes in moderate to good yields (Scheme 30). A plausible mechanism for this

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

• the presence of the organic photocatalyst N-methyl-9-mesitylacridinium (17), CF3SO2Na was converted into CF3• upon visible-light irradiation. The CF3• radical reacted with the vinyl azide to give the iminyl radical 18 that was reduced by Mes-Acr• (Mes-Acr: 9-mesityl-10-methylacridinium) into the

• authors also realised the same chemical transformation under visible light irradiation at 450 nm by means of the iridium photocatalyst Ir[dF(CF3)ppy]2(dtbbpy)PF6 ([4,4’-bis(tert-butyl)-2,2’-bipyridine]bis[3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridinyl]phenyl]iridium(III) hexafluorophosphate), which

• ,b or N-trifluoromethylthiosaccharin 43 in the presence of N-methyl-9-mesitylacridinium under visible light irradiation at room temperature. Terminal, internal, and gem-substituted alkenes bearing imide, ester, amide, ketone, aldehyde and electron-rich aryl functional groups were suitable substrates

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

• into cancer cells and kills them by reactive oxygen species with cytotoxicity generated by light irradiation [94][95]. In addition to reducing the psychological burden of the patients because this process does not require surgical operation, damage to normal cells can be minimized by irradiating the

• under Sonogashira cross-coupling conditions (Scheme 6). UV–vis absorption measurements suggested that the deoxyribonucleoside-linked TFEO-Pcs had a non-aggregation property, as expected. Unfortunately, it was also found that these conjugates gradually decomposed under light irradiation, so their

• deoxyribonucleoside conjugates. An in vitro investigation showed that cyclodextrin-linked TFEO-Pcs were ideal PDT drugs that exhibits high cytotoxicity under light irradiation while displaying little cytotoxicity in the dark (Table 2). On the other hand, interestingly, the fluorine-free tert-butylated derivative

β-Cyclodextrin- and adamantyl-substituted poly(acrylate) self-assembling aqueous networks designed for controlled complexation and release of small molecules

• Liang Yan,
• Duc-Truc Pham,
• Philip Clements,
• Stephen F. Lincoln,
• Jie Wang,
• Xuhong Guo and
• Christopher J. Easton

Beilstein J. Org. Chem. 2017, 13, 1879–1892, doi:10.3762/bjoc.13.183

• ]. Generally, the retention and the release of the drug is controlled by the thermodynamics of drug complexation and in some systems the drug release is stimulated by either pH variation [28][30][34] or light irradiation [38][45]. The drug types include small molecular species, exemplified by diflunisal

Synthesis and metal binding properties of N-alkylcarboxyspiropyrans

• Alexis Perry and
• Christina J. Kousseff

Beilstein J. Org. Chem. 2017, 13, 1542–1550, doi:10.3762/bjoc.13.154

• binding occurs as a result of stabilisation of the zwitterionic merocyanine isomer via phenoxide–metal complexation [17] (Figure 1). Commonly, merocyanines undergo photoreversion to their corresponding spiropyran under visible light irradiation and metal complexation is usually achieved either in darkness

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

• to enable external light irradiation of the reaction mixture while having simultaneously the high-speed ball milling acting on the mixture of reactants and PC (Figure 1; for details, see Supporting Information File 1). Subsequently, with the aim to determine the role of the light, PC and the

• spectroscopy. This time trace quantities of product 3a were detected (Table 1, entry 5). This interesting result under solvent-free conditions encouraged performing the light irradiation accompanied by milling to improve mixing and to increase the surface exposure of the reaction mixture. In a following set of

• ) in the mixture. Indeed, milling the product 3a under the standard milling conditions using the LEDs led to its melt. Similarly, milling a mixture of 1a, 2 and 3a for 1 h under light irradiation reached a eutectic melt phase. The need for simultaneous light and mechanical milling was also confirmed