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

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

• (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

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

• 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

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

• 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

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

• = 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

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

• 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

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

• 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

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

• % 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

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

• 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

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

• 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

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

• 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

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

• (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

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

• 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

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

• -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

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

• 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

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

• 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

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

• 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