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Search for "UV irradiation" in Full Text gives 129 result(s) in Beilstein Journal of Organic Chemistry.

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

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  • 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
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Published 10 Apr 2017

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

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  • 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
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Published 28 Dec 2016

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

  • Josef Schachtner,
  • Patrick Bayer and
  • Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170

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  • (with dyes of ε > 10,000 M−1 cm−1) and traditional photochemistry (involving mostly UV irradiation of colourless organic molecules of ε < 1,000 M−1 cm−1) [61]. The much lower molar attenuation coefficients of the majority of organic molecules which are directly irradiated by UV light in photochemical
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Published 11 Aug 2016

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

  • Jaroslav Padevět,
  • Marcus G. Schrems,
  • Robin Scheil and
  • Andreas Pfaltz

Beilstein J. Org. Chem. 2016, 12, 1185–1195, doi:10.3762/bjoc.12.114

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  • chloride derivatives and sodium diphenylphosphide in liquid ammonia by an SNR2 reaction induced by UV irradiation. Huttner and co-workers [22] on the other hand achieved high yields in nucleophilic substitutions of diarylphosphines with MeC(CH2Cl)3 in DMSO using aqueous KOH as base at elevated temperature
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Published 13 Jun 2016

The role of alkyl substituents in deazaadenine-based diarylethene photoswitches

  • Christopher Sarter,
  • Michael Heimes and
  • Andres Jäschke

Beilstein J. Org. Chem. 2016, 12, 1103–1110, doi:10.3762/bjoc.12.106

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  • substitution pattern, diarylethenes with one alkyl group can exhibit significant photochromism, but they generally show poor stability towards extended UV irradiation, low thermal stability, and decreased fatigue resistance. The results obtained provide an important direction for the design of new efficient
  • nm (phenyl, 1c vs 2c, Table 1). (3) While all two-methyl compounds are stable towards further UV irradiation, the one-methyl compounds are not (see insets in the Figures). Absorbance decreases after reaching a maximum, implying that the closed-ring form undergoes a further light-dependent
  • (Supporting Information File 1, Figure S5). To understand why the one-methyl compounds are so rapidly degraded upon continued UV irradiation, we carried out HPLC and LC–MS analysis of solutions of 1b–d after different times of UV irradiation and compared them with 2b–d (Figure 4). While no additional peaks
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Published 01 Jun 2016

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

  • José M. Andrés,
  • Miriam Ceballos,
  • Alicia Maestro,
  • Isabel Sanz and
  • Rafael Pedrosa

Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61

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  • = triplet, q = quartet, m = multiplet, br = broad), coupling constants in Hertz, and integration. Flash chromatography was carried out using silica gel (230–240 mesh). TLC analysis was performed on glass-backed plates coated with silica gel 60 and an F254 indicator, and visualized by either UV irradiation
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Published 01 Apr 2016

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

  • Julia Wappel,
  • Roland C. Fischer,
  • Luigi Cavallo,
  • Christian Slugovc and
  • Albert Poater

Beilstein J. Org. Chem. 2016, 12, 154–165, doi:10.3762/bjoc.12.17

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  • average number molecular weight (Mn) can be used to characterize the ratio of initiation rate to propagation rate (ki/kp) of a given initiator to monomer combination [28][44][45][46]. Under the applied conditions (prolonged reaction time, reaction temperature up to 100 °C, UV-irradiation) none of the
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Published 28 Jan 2016

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

  • Yury A. Sayapin,
  • Inna O. Tupaeva,
  • Alexandra A. Kolodina,
  • Eugeny A. Gusakov,
  • Vitaly N. Komissarov,
  • Igor V. Dorogan,
  • Nadezhda I. Makarova,
  • Anatoly V. Metelitsa,
  • Valery V. Tkachev,
  • Sergey M. Aldoshin and
  • Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

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  • which has attracted much attention due to the applications in various molecular probes and luminescent materials because of the remarkable photophysical properties of the ESIPT (excited state intramolecular proton transfer) chromophores [33][34]. UV-irradiation of solutions of these compounds in
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Published 12 Nov 2015

Dicarboxylic esters: Useful tools for the biocatalyzed synthesis of hybrid compounds and polymers

  • Ivan Bassanini,
  • Karl Hult and
  • Sergio Riva

Beilstein J. Org. Chem. 2015, 11, 1583–1595, doi:10.3762/bjoc.11.174

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  • % methacrylate ends were used directly in film formation, without any other purification than filtering off the immobilized lipase (Figure 21). The telechelics were either homopolymerized or polymerized in combination with a tetrathiol cross-linker to form strong films under UV irradiation [78]. In a similar
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Published 09 Sep 2015

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

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  • with both solvents are very stable for months of storage in a closed container, and no significant changes can be found. However, upon UV irradiation, the gel to sol phase transition became transparent as a result of trans-to-cis isomerization. Moreover, the solution has a tendency to reverse the sol
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Published 29 Jun 2015

Probing multivalency in ligand–receptor-mediated adhesion of soft, biomimetic interfaces

  • Stephan Schmidt,
  • Hanqing Wang,
  • Daniel Pussak,
  • Simone Mosca and
  • Laura Hartmann

Beilstein J. Org. Chem. 2015, 11, 720–729, doi:10.3762/bjoc.11.82

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  • zeta potential measurements. In addition, we explore the effect of the reaction conditions, such as concentration of reagents or UV irradiation time on the functionalization degree of CA-functionalized particles. Comparison of the functionalization of PEG SCPs with different carboxylic acid monomers
  • because it reduces nonspecific interactions and also complicates the bioconjugation. To deal with this problem, we adjusted a surface chemistry route including radical generation at the PEG backbone by UV irradiation [15]. This enabled the addition of unsaturated carboxylic moieties onto the PEG scaffold
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Published 12 May 2015

Automated solid-phase synthesis of oligosaccharides containing sialic acids

  • Chian-Hui Lai,
  • Heung Sik Hahm,
  • Chien-Fu Liang and
  • Peter H. Seeberger

Beilstein J. Org. Chem. 2015, 11, 617–621, doi:10.3762/bjoc.11.69

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  • equiv TfOH, NIS, DCM, −30 °C (5 min), −10 °C (25 min) for 9 and 10. Fmoc Deprotection: e) 3 × 20% NEt3 in DMF, 5 min. Photocleavage: f) UV irradiation using a continuous flow reactor, DCM, rt. Synthesis of 12 or 13: (1) 6, b, (2) e, (3) 4 or 5, a (4) f, 30% for four steps to yield 12, 40% for four steps
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Published 04 May 2015

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

  • Nikolai V. Rostovskii,
  • Mikhail S. Novikov,
  • Alexander F. Khlebnikov,
  • Galina L. Starova and
  • Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

Graphical Abstract
  • (4e) 2H-1,4-oxazines proved to be stable in the dark but undergo an irreversible ring opening to azadienes 3 under UV irradiation. Thus, irradiation of oxazine 4a for 1.5 h gives quantitatively azadiene Z-3a which was also obtained by the reaction of azirine 1a and α-diazo-α-phenylacetone (2a, Table 1
  • , entry 1). By contrast, 5-acetyl-substituted oxazines 4f–i are photochromic compounds. Being pale yellow colored, under UV irradiation in a CDCl3 solution at room temperature they undergo a ring opening to yellow–orange azadienes 3f–i which cyclize back to oxazines 4f–i in the dark. The effect of the C5
  • in the dihydroazireno[2,1-b]oxazole intermediate. Under UV irradiation 5-unsubstituted and 5-aryl-substituted 2H-1,4-oxazines produce stable 2-azabuta-1,3-dienes. In contrast, 5-acyl-substituted 2H-1,4-oxazines are photochromic compounds, i.e., under UV irradiation they undergo ring opening to 2
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Published 02 Mar 2015

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

  • Pablo Wessig,
  • Roswitha Merkel and
  • Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

Graphical Abstract
  • scope of the present study and will be published elsewhere. All of the cinnamoyl derivatives 32b, 33a and 39 are photochemically reactive and both the UV irradiation spectra as well as MS and NMR spectra of the crude product mixture suggest that the formation of cyclic truxinates took place as the
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Published 16 Jan 2015

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

  • Lidija-Marija Tumir,
  • Marijana Radić Stojković and
  • Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

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  • -halobenzyl)arylamines, oxime carbonates, isocyanobiphenyls, etc.). Phenanthridines are usually obtained within 2–3 reaction steps, by application of different radical initiators. An intriguing alternative is the radical generation by UV irradiation with or even without a photocatalyst. The major advantage of
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Published 10 Dec 2014

Synthesis and characterization of a new photoinduced switchable β-cyclodextrin dimer

  • Florian Hamon,
  • Claire Blaszkiewicz,
  • Marie Buchotte,
  • Estelle Banaszak-Léonard,
  • Hervé Bricout,
  • Sébastien Tilloy,
  • Eric Monflier,
  • Christine Cézard,
  • Laurent Bouteiller,
  • Christophe Len and
  • Florence Djedaini-Pilard

Beilstein J. Org. Chem. 2014, 10, 2874–2885, doi:10.3762/bjoc.10.304

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  • confirm this hypothesis, the same ITC study was performed after UV irradiation at 365 nm for 120 min (Figure 6e). To improve the stability of cis-AZO-CDim 1, the titration was carried out at 278 K under the same experimental conditions as previously performed. The average values for the thermodynamic
  • parameters are summarized in Table 1. Again, two jumps can be observed in the enthalpogram (Figure 6d), the stoichiometry of which has been shifted due to the UV irradiation. Neither the 20 °C difference nor the changing stoichiometry is thought to greatly affect the formation constants of the complexes. We
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Published 04 Dec 2014

Photo, thermal and chemical degradation of riboflavin

  • Muhammad Ali Sheraz,
  • Sadia Hafeez Kazi,
  • Sofia Ahmed,
  • Zubair Anwar and
  • Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

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  • reaction was higher on UV irradiation as compared to that of the visible irradiation. Similarly, the magnitude of the formation of the photoproducts was higher in solutions exposed to UV light as compared to the visible light. The difference in rates might be due to the higher intensity of the UV radiation
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Published 26 Aug 2014

Improving the reactivity of phenylacetylene macrocycles toward topochemical polymerization by side chains modification

  • Simon Rondeau-Gagné,
  • Jules Roméo Néabo,
  • Maxime Daigle,
  • Katy Cantin and
  • Jean-François Morin

Beilstein J. Org. Chem. 2014, 10, 1613–1619, doi:10.3762/bjoc.10.167

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  • are also present in the Raman spectrum of PAM2 due to partial photo-induced polymerization during spectrum acquisition. This demonstrates the high reactivity of PAM2 under UV irradiation. Further research on the resulting nanoarchitectures is currently underway to establish if covalent nanotubes have
  • to PAM3. Scanning electron microscopy (SEM) images of PAM2 xerogel in cyclohexane (10 mg/mL). Scales are a) 1 μm and b) 0.5 μm. UV–vis spectrum of PAM2 before (black) and after (red) polymerization (PDA). Background-corrected Raman spectra of PAM2 (red) and the blue material obtained after UV
  • irradiation (black). Synthetic pathway to PAM2 and PAM3. Supporting Information Supporting Information File 456: Experimental part. Acknowledgements This work was supported by NSERC through a Discovery Grant. We thank Rodica Plesu (U. Laval) and Jean-François Rioux (U. Laval) for their help in polymer
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Published 15 Jul 2014

Orthogonal dual thiol–chloroacetyl and thiol–ene couplings for the sequential one-pot assembly of heteroglycoclusters

  • Michele Fiore,
  • Gour Chand Daskhan,
  • Baptiste Thomas and
  • Olivier Renaudet

Beilstein J. Org. Chem. 2014, 10, 1557–1563, doi:10.3762/bjoc.10.160

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  • of DMF and H2O under UV irradiation (λ = 365 nm) in the presence of 2,2-dimethoxy-2-phenylacetophenone (DPAP) as a radical initiator (Scheme 1, route A). In previous studies [26], we observed that the TEC reaction requires the utilization of 3 equivalents of sugar per reaction site to be complete
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Published 08 Jul 2014

Multichromophoric sugar for fluorescence photoswitching

  • Stéphane Maisonneuve,
  • Rémi Métivier,
  • Pei Yu,
  • Keitaro Nakatani and
  • Juan Xie

Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151

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  • multichromophoric glucopyranoside 2 bearing three dicyanomethylenepyran (DCM) fluorophores and one diarylethene (DAE) photochrome has been prepared by Cu(I)-catalyzed alkyne–azide cycloaddition reaction. The fluorescence of 2 was switched off upon UV irradiation, in proportion with the open to closed form (OF to CF
  • -dicyanomethylene-2-tert-butyl-6-(p-dialkylaminostyryl)-4H-pyran) [3] with a photochromic diarylethene (DAE) which showed a photoreversible two-way FRET controlled by the state of the photochromic moiety, and 49% quenching of the fluorescence upon UV irradiation [4]. Bifunctional molecules built on two distinct
  • illumination is composed of 91% of 9-CF and 9% of 9-OF (Figure 3c, dashed line). The target compound 2 can be considered as the assembly of the fluorescent model derivative 6 and the photochromic model compound 9. Indeed, before any UV irradiation, the absorption spectrum of 2 in its open form (2-OF
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Published 30 Jun 2014

Cyclization–endoperoxidation cascade reactions of dienes mediated by a pyrylium photoredox catalyst

  • Nathan J. Gesmundo and
  • David A. Nicewicz

Beilstein J. Org. Chem. 2014, 10, 1272–1281, doi:10.3762/bjoc.10.128

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  • were inspired by the work of Miyashi, who, during the course of the investigation of the cation radical Cope rearrangement, discovered an intriguing endoperoxide-forming reaction (Scheme 1, reaction 1). Upon exposure of 1,5 and 1,6-dienes to catalytic quantities of 9,10-dicyanoanthracene (DCA) under UV
  • irradiation in the presence of oxygen, bicyclic endoperoxides were obtained [12]. Formation of the 1,2-dioxanes was presumed to occur via single electron oxidation of the diene by the excited state DCA followed by either 6-endo or 7-endo cyclization modes to generate a fleeting distonic cation radical species
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Published 03 Jun 2014

Atherton–Todd reaction: mechanism, scope and applications

  • Stéphanie S. Le Corre,
  • Mathieu Berchel,
  • Hélène Couthon-Gourvès,
  • Jean-Pierre Haelters and
  • Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117

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  • mechanism proceeding by radical processes. Indeed, the use of UV irradiation or radical initiators in the absence of trialkylamine was found to be unsuccessful to produce phosphoramidates. Recently, Krutikov et al. [9] have reported that hexahydroazepine (a secondary amine with a pKa of 11.1 (Scheme 3-iii
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Published 21 May 2014

Solid-phase-supported synthesis of morpholinoglycine oligonucleotide mimics

  • Tatyana V. Abramova,
  • Sergey S. Belov,
  • Yulia V. Tarasenko and
  • Vladimir N. Silnikov

Beilstein J. Org. Chem. 2014, 10, 1151–1158, doi:10.3762/bjoc.10.115

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  • plates (Merck, Germany) in the proper solvent systems (see below) and visualized by UV irradiation, ninhydrin (amine groups) or cystein/aqueous sulfuric acid (nucleoside and trityl groups). Preparative silica gel column chromatography, RPC, and cation exchange chromatography were performed using silica
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Published 20 May 2014

Domino reactions of 2H-azirines with acylketenes from furan-2,3-diones: Competition between the formation of ortho-fused and bridged heterocyclic systems

  • Alexander F. Khlebnikov,
  • Mikhail S. Novikov,
  • Viktoriia V. Pakalnis,
  • Roman O. Iakovenko and
  • Dmitry S. Yufit

Beilstein J. Org. Chem. 2014, 10, 784–793, doi:10.3762/bjoc.10.74

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  • -system (4.56, 4.68 ppm). Attempts to initiate the reaction by UV-irradiation (at 20 or 50 °C) or catalysis by compounds of transition metals (Cu(acac)2, Fe(acac)3, Pd(bzac)2, Rh2(AcO)4, Cu(OTf)2, Pd/C) at 20 or 40 °C failed. Benzene was found to be a solvent of choice, and a 1:1 molar ratio of reagents
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Published 04 Apr 2014

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

  • Dae Won Cho,
  • Patrick S. Mariano and
  • Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

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  • which nitrogen-linked side chains containing polyethoxy-tethered phthalimides and naphthalimides, possessing terminal α-trialkylsilyl groups, are synthesized utilizing concise routes and UV-irradiation to form macrocyclic ring systems. In contrast, the indirect route developed for the synthesis of
  • naphthalimides, possessing terminal α-trialkylsilyl groups, are synthesized utilizing concise routes and UV-irradiation to form the macrocyclic ring systems (Scheme 6). In contrast, the indirect route developed for the synthesis of lariat-type crown ethers employs sequences in which the SET-promoted
  • branched chain-tethered phthalimides In order to explore the feasibility of using the direct approach for the preparation of lariat-type crown ethers, branched, bis(α-silyl ether)-terminated chains containing phthalimides 32 and 33 were prepared and subjected to UV-irradiation in MeOH solution containing
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Published 27 Feb 2014
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