Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• inert atmosphere of argon. Concentrations (c) in the general procedures refer to the limiting reagent and are given in mmol/mL. Thin-layer chromatography (TLC) was carried out on Merck aluminium foil backed sheets precoated with 0.2 mm Kielselgel 60 F254. The spots were visualized by UV irradiation (λ

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• the rigid coordination of the imidazole group to the metal ion, which prevents the rotation of the group needed for cyclization. Families of diarylethene-bases ligands with spatial proximity of coordination site (blue) and photoactive framework (red). Electronic spectra of diarylethene 6 upon UV

• irradiation (313 nm, toluene, c = 3.4 × 10−5 M). Inset: fatigue resistance upon multiple subsequent irradiation with UV (365 nm) and visible light (green LED) in acetonitrile. Molecular structure of complexes 8 (top) and 9 (bottom) at 100 K. The H atoms are omitted for clarity; the thermal ellipsoids are

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• photoisomerization of encapsulated E-1. UV irradiation (365 nm light-emitting diode, LED) of the transparent yellow solution of (E-1)22 in water did not result in any pronounced visual changes. However, UV–vis absorption spectroscopy showed (Figure 4) a dramatic decrease in the intensity of E-1’s absorption at 336

• photoisomerization reaction, we investigated it by NMR spectroscopy under in-situ irradiation (with an optical fiber inserted into the NMR spectrometer). Figure 6 shows a series of spectra recorded after increasing UV irradiation times. We found that whereas the position of 2’s H4 signal did not change (9.26 ppm

• with any of the three methyl groups. Furthermore, we note that the resonance due to Hb – very broad in complex (E-1)22 as a consequence of dimer formation – becomes as sharp as those of the other protons after UV irradiation (compare spectra i and ii in Figure S23, Supporting Information File 1). Taken

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• ring-closure reaction was fully reversible by irradiation with longer wavelengths. This offers the possibility of reversible switching a DAE only with visible, avoiding harmful (cytotoxic) UV irradiation. In view of the forthcoming solubilizing strategies applicable to fluorescent DAEs and intended for

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

• solutions (λex = 370 nm). (c) The fluorescence quenching of THF 100 vol % (water 0 vol %) solution at 670 nm (broken line) and that of THF/water = 10:90 (v/v) at 585 nm (solid line) upon UV irradiation. (a) Crystals of 1o before UV light irradiation, (b) Green fluorescence of 1o observed under UV light (λ

• = 365 nm) irradiation, (c) Cyclization proceeded to form 1c with suppression of the fluorescence, (d) Fluorescence spectra of 1o in the crystalline state (λex = 370 nm, λmax = 537 nm), (e) The fluorescence quenching of 1o in the crystalline state (λex = 370 nm, λem = 537 nm) upon UV irradiation

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• unclear. Photochemistry of azastilbenes The photochemical behaviour of stilbenes has been subject to intense investigation in the past. It is reported that unsubstituted stilbene undergoes E→Z photoisomerization [47], as well as photocyclization to dihydrophenanthrene upon UV irradiation, which is

• provided deeper insights and clarified the differential behaviour observed in the UV–vis spectra of 2b and 2f after UV irradiation. As anticipated, UV irradiation lead to E→Z isomerization of the C=C double bond in both compounds. The (Z)-isomers were found to be slightly more polar than the respective (E

• stilbene motive of selected stilbene 2c by a diazeno group, because photoisomerization of azo dyes was anticipated to proceed fast and reversible by application of UV irradiation and visible light, respectively in this analogue. 5-Diazenylnicotinamide 11 was synthetically accessible in two steps through

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

• -functionalized with the CD, no assembly could be observed after addition of the divalent azobenzene linker. Moreover, the assemblies could only once be disassembled by the combination of UV irradiation and physical forces by sonication. The light-induced back-isomerization of azobenzenes did not form similar end

• with dAAP during four cycles of irradiation. a) Longitudinal SPR. b) Transversal SPR. TEM-BF images of a) [tCD+tTEG]AuNR. b and c) AuNR end-to-end assemblies by dAAP (15 µM). d) Dissolved AuNR by UV irradiation (λ = 360 nm). Reversible aggregation of [tCD+tTEG]AuNR by addition of dAAP (15 µM) monitored

Remarkable effect of alkynyl substituents on the fluorescence properties of a BN-phenanthrene

• Alberto Abengózar,
• David Sucunza,
• Patricia García-García and
• Juan J. Vaquero

Beilstein J. Org. Chem. 2019, 15, 1257–1261, doi:10.3762/bjoc.15.122

• these compounds are summarized in Table 1, and a picture of their solutions under UV irradiation are shown in Figure 3. The emission maxima were not significantly affected by the presence of substituents, except for 7-amino substituted BN-phenanthrene 1d and 1-alkynyl substituted BN-phenanthrene 5

• BN-phenanthrenes 1 and 5 in cyclohexane (≈0.02 mM). Solutions of 1a–f and 5 (from left to right) under UV irradiation. Synthesis of Cl-substituted BN-phenanthrene 1b. Palladium-catalyzed cross-couplings of Cl-substituted BN-phenanthrene 1b. Pd-catalyzed Sonogashira reactions of Cl-substituted BN

Insertion of [1.1.1]propellane into aromatic disulfides

• Robin M. Bär,
• Gregor Heinrich,
• Martin Nieger,
• Olaf Fuhr and
• Stefan Bräse

Beilstein J. Org. Chem. 2019, 15, 1172–1180, doi:10.3762/bjoc.15.114

• the first to use UV irradiation in this reaction, but did not report detailed conditions [28]. They used diacetyldithiol and 1 to obtain bisacetylthio[n]staffanes. To find feasible conditions for the insertion of 1 into disulfide bonds, a screening with irradiations of different wavelengths and other

• the UV irradiation. In the benzyl group only the aromatic part can absorb the light and a transfer has to take place to promote the homolytic cleavage of the disulfide. In first purification attempts [2]staffane 14 could be identified in a mixture with 13 in traces. From the product mixture we could

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

• by a radical process promoted by UV irradiation, with an initial formation of aryl radical 116 from the corresponding aryl iodide 113 (Scheme 33). This radical would cyclize in an intramolecular 5-exo mode to furnish cyclic radical 117 which, in turn, can be caught by intermediate 118, formed by

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• ]-cycloaddition methodology. They used the vertex grinding technique where solid-state grinding and UV irradiation was done simultaneously [111] and verified co-crystal formation of a resorcinol derivative with dipyridylethylene in the solid state. Also, the supramolecular catalysis of [2 + 2] photodimerization

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

• of 1a and 2a under 365 nm UV lamp irradiation without a photocatalyst delivered product 3aa in 75% yield (Table 1, entry 9). This indicates the excitation of xanthate 1a through an n→π* electronic transition of the C=S bond is in operation in the UV irradiation process. The involvement of a radical

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

• cleavage has been reported for alkyl and aryl disulfides in an oxidative [44][45][46] and triplet sensitized mechanism [47]. It is also well known in literature that aromatic disulfides are cleaved homolytically under UV irradiation yielding the corresponding radicals [48]. A recent study from Nicewicz

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• film hydration method. To identify an optimal calixarene–AEPCDA ratio a series of PDA vesicles containing 1, 5, 10, 50 mol % of 10b was prepared. Polymerization of AEPCDA–calixarene vesicles was performed under UV irradiation using 254 nm light in quartz cuvettes of 1 cm path length. The absorbance

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

• fluorinated alkyl radicals is typically realized either by single-electron reduction or by radical abstraction of iodine [41][42][43]. Furthermore, the carbon–iodine bond is prone to homolytic cleavage under UV irradiation [44]. In this regard, we were inspired by the work of Ryu describing the use of

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• last possibility of how to influence the cycloaddition between sydnones and alkynes involves photochemical performance of this reaction. Under UV-irradiation sydnones form the corresponding unstable nitrilimines which then undergo [3 + 2]-cycloaddition to give pyrazoles carrying substituents

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Enhanced quantum yields by sterically demanding aryl-substituted β-diketonate ancillary ligands

• Rebecca Pittkowski and
• Thomas Strassner

Beilstein J. Org. Chem. 2018, 14, 664–671, doi:10.3762/bjoc.14.54

• -phenylimidazole platinum(II) complex with acetylacetonate as counter ligand, Pt(MPIM)(acac) [42], which shows a very weak emission (Φ = 7%), the new complexes exhibit a dramatically enhanced quantum yield (emission under UV irradiation is shown in Figure 5). The higher emission efficiency is accompanied by a red

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• protic solvents such as H2O or EtOH at 100 °C, the desired products were formed in short reactions (1–20 min) and chromene-2-carbonitriles 12–15 were isolated in 61–88% yields. Saito et al. generated o-QMs starting from Mannich bases by low-energy UV irradiation in aqueous acetonitrile [68]. In the

Stimuli-responsive oligonucleotides in prodrug-based approaches for gene silencing

• Françoise Debart,
• Christelle Dupouy and
• Jean-Jacques Vasseur

Beilstein J. Org. Chem. 2018, 14, 436–469, doi:10.3762/bjoc.14.32

• currently, most of the activities of photocaged ONs have been validated on reporter gene models except for a few studies on specific genes in zebrafish embryos. Despite the advantages described above, the use of light to control gene expression has several drawbacks. Extended UV irradiation may produce side

• reactions, lowering the yield of active ON and inducing toxicity. Moreover, the diffusion of light resulting from long UV irradiation decreases temporal and spatial resolution for experiments in cells. Finally, because light has poor tissue diffusion, the photocaging approach may be restricted to in vitro

• (Scheme 20C). These caged siRNAs were completely inactive until removal of the protecting groups with UV irradiation at 366 nm, whereas modifications surrounding the central part of the siRNA were less effective. It was argued that modified nucleotides in the central part of siRNA lead to a bulge of the

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

• anhydride and dimethyl maleate were hydrotrifluoromethylated with CF3SO2Na in the presence of 4,4’-dimethoxybenzophenone as photosensitiser under near-UV irradiation (350 nm) and hexafluoroisopropanol (HFIP) as a proton donor (Scheme 20) [40]. The reactions were performed in batch and under continuous flow

• prototypical (hetero)aromatic substrates that were trifluoromethylated with CF3SO2Na in the presence of 4,4’-dimethoxybenzophenone as photosensitiser under near-UV irradiation (350 nm) and HFIP as a proton donor [40]. More recently, Yuan and co-workers reported an efficient and operationally simple method for

• out under UV irradiation with either a 300 W xenon lamp (emission wavelengths between 200 and 1000 nm) or the photoreactor (λ = 254 nm). This photochemical process allowed the synthesis of trifluoromethylated arenes (Scheme 51), but also heteroarenes and nucleosides in good yields [74]. Further to

New electroactive asymmetrical chalcones and therefrom derived 2-amino- / 2-(1H-pyrrol-1-yl)pyrimidines, containing an N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment: synthesis, optical and electrochemical properties

• Daria G. Selivanova,
• Alexei A. Gorbunov,
• Olga A. Mayorova,
• Alexander N. Vasyanin,
• Igor V. Lunegov,
• Elena V. Shklyaeva and
• Georgii G. Abashev

Beilstein J. Org. Chem. 2017, 13, 1583–1595, doi:10.3762/bjoc.13.158

• colourless (2a,b) to orange (7a,b). Under UV irradiation (λeх = 315–390 nm) the luminescence of solutions varies from blue (2a,b) to orange (7a,b). It has been found out that UV-irradiated solutions of the obtained chromophores 6a,b–8a,b change their colours in different solvents of various polarity; for

• example, compounds 7a,b demonstrate a yellow fluorescence in dichloromethane, DMF, acetone, and an orange one in ethanol, that is most likely connected with the enhancement of the intramolecular charge transfer under UV irradiation. The prepared compounds differ from each other only by the nature of the

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

• or under UV irradiation. Greater stabilisation of merocyanine–metal cation complexes is often achieved through the addition of extra ligation sites and this effect is particularly pronounced in structures bearing an 8′-OMe substituent with respect to binding divalent metal cations [18] (Scheme 1

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

• cyclodextrin utilised, with each CD showing a green emission under UV irradiation and excitation-independent emission from 360 to 460 nm excitation, which is typical of a uniform morphology. The authors proposed that the uniform emission could be attributed to either the uniform size distribution or 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

• nanosized titanium dioxide (nanoTiO2) applied in photodegradation-based procedures can be stabilized with cyclodextrins in order to obtain a new, more efficient photocatalyst for the purification of waters polluted by xenobiotics applying UV irradiation. During our work, on the one hand, we studied the

• -stabilized nanoTiO2 as additive hardly any decrease in the drug concentration upon UV irradiation was measured especially in tap water. It is well-known that the complexation often has a protective effect on the included guest molecules [8]. Either catalysis or inhibition of the light-induced cleavage can