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

• [Cu(I)(dpp)2]PF6 complex can be excited under visible light irradiation (530 nm), and the resulting excited [Cu(I)]* complex undergoes an SET to reduce the diaryliodonium species, providing the oxidized [Cu(II)] complex. The reduced diaryliodonium species collapses into an aryl radical and the

• large panel of substrates was functionalized under visible light irradiation. The functional group tolerance of the process was excellent and the products were obtained in moderate to excellent isolated yields. The authors suggested a chain radical process to explain the formation of the product. The

• 2012, Collins and co-workers described a copper-catalyzed photocyclization to synthesize [5]helicene (Scheme 29) [43]. Using the in situ-formed [Cu(I)(dmp)(xantphos)]BF4 (25 mol %) in the presence of iodine and propylene oxide as the oxidant system under visible light irradiation, [5]helicene was

In search of visible-light photoresponsive peptide nucleic acids (PNAs) for reversible control of DNA hybridization

• Lei Zhang,
• Greta Linden and
• Olalla Vázquez

Beilstein J. Org. Chem. 2019, 15, 2500–2508, doi:10.3762/bjoc.15.243

• , artificial probes activated by visible-light irradiation are highly desired in biological applications. Here, we report two novel types of visible-light photoswitchable peptide nucleic acids (PNAs) based on the molecular transducers: hemithioindigo and tetra-ortho-fluoroazobenzene. Our study reveals that the

• tetra-ortho-fluoroazobenzene–PNA conjugates have promising properties (fast reversible isomerization, exceptional thermal stability, high isomer conversions and sensitivity to visible-light irradiation) as reversible modulators to control oligonucleotide hybridization in biological contexts. Furthermore

• first compounds here reported, may find applications in different fields such as chemical biology, nanotechnology and materials science. Keywords: azobenzene; hemithioindigo; peptide nucleic acid (PNA); photoswitch; visible-light irradiation; Introduction Light-driven control of oligonucleotide

Targeted photoswitchable imaging of intracellular glutathione by a photochromic glycosheet sensor

• Xianzhi Chai,
• Hai-Hao Han,
• Yi Zang,
• Jia Li,
• Xiao-Peng He,
• Junji Zhang and
• He Tian

Beilstein J. Org. Chem. 2019, 15, 2380–2389, doi:10.3762/bjoc.15.230

• ring-closed photoisomer [28]. The absorption band at 550 nm remained unchanged after 3 min of irradiation as the photostationary state (PSS) was reached. The absorption spectra of the ring-opened isomer could be fully recovered upon visible light irradiation (4 min), suggesting a photocycloreversion or

• several times in buffer solution without obvious degradation (Figure 1B), demonstrating the robustness of Glyco-DTE. Figure 1C shows the photoswitching of emission spectra of Glyco-DTE (1 × 10−5 mol/L) in PBS buffer upon alternating UV and visible light irradiation at room temperature. Upon excitation

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• changed to blue with increasing the absorption band at 587 nm of the closed-ring isomer 1c, then by visible light irradiation the color disappeared and reproducing the absorption spectra at 285 nm of 1o. The cyclization and cycloreversion reactions of 1 were measured in THF and methanol. The results were

• nm) and AS ONE Handy UV Lamp SLUV-4 (λ = 365 nm) were used. For visible light irradiation, a 500W USHIO SX-UI501XQ Xenon lamp attached with Toshiba color filters (Y-48, Y-44, and UV-29) was used. The Gaussian09 program package [32] was used for geometry optimizations with DFT for ground states and

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

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

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

• 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

• , and Irdfppy system was used for radical-mediated isomerization reactions. Visible-light irradiation of diethyl 2-bromomethyl-2-phenylmalonate produced the phenyl-migrated product (Scheme 10) [104]. The product distribution highly depended on the solvents. The yield of phenyl-migrated products relative

• presence of 1 in methanol/n-Bu4NClO4 to form Co(III)–RF complexes with deiodination. These complexes released RF radicals on the Co(III)-bond cleavage through visible-light irradiation. The resultant radicals reacted with aromatic reagents to form the target products through direct C–H functionalization

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

• (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

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

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

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

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 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

Kinetic analysis of mechanoradical formation during the mechanolysis of dextran and glycogen

• Naoki Doi,
• Yasushi Sasai,
• Yukinori Yamauchi,
• Tetsuo Adachi,
• Masayuki Kuzuya and
• Shin-ichi Kondo

Beilstein J. Org. Chem. 2017, 13, 1174–1183, doi:10.3762/bjoc.13.116

• TCNE under visible-light irradiation. We adopted this method by Sakaguchi et al for the detection of mechanoanions (see Experimental). Figure 5 shows the observed ESR spectrum before and after visible-light irradiation of the fractured sample of Dx and TCNE. As no ESR spectrum was observed after the

• mechanochemical reaction of pure TCNE, it was assumed that the ESR spectrum depicted in Figure 5a might be ascribed to the radical produced by the reaction of Dx mechanoradical and TCNE. As the characteristics of the spectrum and the intensity before and after visible-light irradiation remained unaffected, there

• induce electron release. After vigorously shaking of the mixture it was transferred to an ESR tube in the dark. ESR spectra were taken before and after visible-light irradiation. Molecular weight measurements Similarly as described in [19], the molecular weight of each resulting polymer was measured by

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

• and to minimize the formation of the byproducts was conducted. As recently surveyed, photoredox catalysts are widely employed for the generation of radicals for diverse radical reactions [19]. Further, the application of aryl radicals generated from aryldiazonium salts under visible light irradiation

• radical I was initially generated under visible light irradiation [14][15]. Subsequently, the radical I attacked the sulfur atom of carbon disulfide to provide the intermediate II which can be converted to radical intermediate III through the cleavage of the carbon–sulfur bond accompanied with the release

Copper-catalyzed asymmetric sp³ C–H arylation of tetrahydroisoquinoline mediated by a visible light photoredox catalyst

• Pierre Querard,
• Inna Perepichka,
• Eli Zysman-Colman and
• Chao-Jun Li

Beilstein J. Org. Chem. 2016, 12, 2636–2643, doi:10.3762/bjoc.12.260

• , entries 7 and 8). A tentative reaction mechanism has been proposed in Scheme 3, in order to rationalize this arylation reaction. Upon visible light irradiation, [Ir(ppy)2(dtbbpy)]PF6 I was converted into an excited state II, Ir(III)* [11][33][34][35][36][37]. The THIQ undergoes a single electron transfer

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

• substrates would be grinded under visible light irradiation. In contrast to mechanochemistry, the process would be driven by light energy and not by mechanical energy, but profit from the absence of toxic solvents, high concentrations of the substrate, and easy work-up. Furthermore, undesired effects of the

Synthesis of photoresponsive cholesterol-based azobenzene organogels: dependence on different spacer lengths

• Yuchun Ren,
• Bin Wang and
• Xiuqing Zhang

Beilstein J. Org. Chem. 2015, 11, 1089–1095, doi:10.3762/bjoc.11.122

• organogelators and soft matter. Changes in the absorption over time in the UV–vis spectra of dilute THF solution of M0: (a) upon UV-light irradiation (λ = 365 nm) and (b) upon visible-light irradiation (λ = 450 nm) of the solution obtained after irradiation of 365 nm. DSC thermogram of the compounds M0-n

• obtained on (a) heating and (b) cooling. Photographic images of the M6 sol-gel transition behavior after UV or visible light irradiation in different solution (a) ethanol, (b) isopropanol and (c) 1-butanol. SEM images of xerogels formed with M6 from solution: (a) ethanol, (b) isopropanol and (c) 1-butanol