Organotellurium-mediated living radical polymerization under photoirradiation by a low-intensity light-emitting diode

• Yasuyuki Nakamura and
• Shigeru Yamago

Beilstein J. Org. Chem. 2013, 9, 1607–1612, doi:10.3762/bjoc.9.183

• conditions [8][9][10][11]. In addition, photochemical activation is beneficial for increasing the fidelity of the polymer-end structure [12]. However, the experimental setup required for the reaction provides problems, as distinctive light sources such as γ-rays or high-intensity UV irradiation are required

Diastereoselective radical addition to γ-alkyl-α-methylene-γ-butyrolactams and the synthesis of a chiral pyroglutamic acid derivative

• Tomoko Yajima,
• Eriko Yoshida and
• Masako Hamano

Beilstein J. Org. Chem. 2013, 9, 1432–1436, doi:10.3762/bjoc.9.161

• ][7][8] and no reports on radical addition. We have already investigated diastereoselective alkyl radical additions to α-methylene-γ-phenyl- γ-lactam and reported that the N-unsubstituted lactam yields cis-α,γ-disubstituted lactams using (Me3Si)3SiH under UV irradiation, whereas the reactions of N

• temperature under UV irradiation. The reactions of 1a and 1b yielded strong cis-diastereoselectivities, but the reactions of 1c and 1d were less diastereoselective. Next, isopropyl radical additions to N-pivaloyl substrates 3a–3d in the presence of a Lewis acid were investigated (Table 2). The reactions of 3a

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• phenylacetylene under UV irradiation or upon heating in the presence of AIBN (Scheme 6) [27]. The reaction consists of the addition of a diorganophosphanyl radical to phenylacetylene and the homolytic substitution of tetraorganodiphosphine with the resulting vinyl radical to afford the adduct and to regenerate

• fluorescence (Scheme 8). The initially formed diphosphanylethylene derivatives are not very stable in air, and therefore sulfidation or oxidation was performed to accurately assess the efficiency of the diphosphination reactions. Ogawa independently reported similar diphosphination under UV irradiation (Table

Design and synthesis of tag-free photoprobes for the identification of the molecular target for CCG-1423, a novel inhibitor of the Rho/MKL1/SRF signaling pathway

• Jessica L. Bell,
• Andrew J. Haak,
• Susan M. Wade,
• Yihan Sun,
• Richard R. Neubig and
• Scott D. Larsen

Beilstein J. Org. Chem. 2013, 9, 966–973, doi:10.3762/bjoc.9.111

• 29 (Figure 4), i.e., an analogue of 2 with slightly greater potency (IC50 = 6.4 µM) that was identified in later SAR studies [23]. UV irradiation was applied for 30 min at room temperature by using the long-wavelength setting of a hand-held illuminator (366 nm, UVL-56 lamp, UltraViolet Products, San

High-spin intermediates of the photolysis of 2,4,6-triazido-3-chloro-5-fluoropyridine

• Sergei V. Chapyshev,
• Denis V. Korchagin,
• Patrik Neuhaus and
• Wolfram Sander

Beilstein J. Org. Chem. 2013, 9, 733–742, doi:10.3762/bjoc.9.83

• -spin intermediates formed during the photolysis of asymmetric triazide 11, providing the first information about selective photochemical decomposition of three nonequivalent azido groups in monocyclic aromatic compounds. Results and Discussion Brief UV irradiation (2 min, λ = 260–320 nm) of triazide 11

• when an additional line-broadening parameter Γ(E) was used in the spin-Hamiltonian calculations [24]. The necessity of the use of this parameter in calculations is due to the presence in matrices of numerous conformational isomers of the starting azides. Upon UV irradiation, these conformers decompose

• UV irradiation of triazide 11. Microwave frequency ν0 = 9.605832 GHz. UB3LYP/6-311G*+BLYP/EPRII calculated orientations of the tensors DSS and DSO in nitrenes 15–18. The tensors DSS and DTot have the same orientations. Mulliken spin populations on the nitrene units and parameters DTSS in cm−1 of

Towards a biocompatible artificial lung: Covalent functionalization of poly(4-methylpent-1-ene) (TPX) with cRGD pentapeptide

• Lena Möller,
• Christian Hess,
• Jiří Paleček,
• Yi Su,
• Axel Haverich,
• Andreas Kirschning and
• Gerald Dräger

Beilstein J. Org. Chem. 2013, 9, 270–277, doi:10.3762/bjoc.9.33

• 2 with a methanolic solution of nitrene precursor 3, and then drying followed by UV irradiation (Hg lamp, 254 nm) initially did not lead to surface modification. The presence of F and N on the TPX membrane was not detectable by XPS analysis. The photoinduced reaction of azide 3 with cyclohexane

• membrane 2 (see below; bars are given in cm) was treated with a solution of azide 3 as described above and UV-irradiation gave covalently functionalized polymer 4. For practicability reasons, flat TPX membranes instead of hollow fibers were used. Physicochemical analysis of modified TPX foils Analysis of

A bisazobenzene crosslinker that isomerizes with visible light

• Subhas Samanta,
• Harris I. Qureshi and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2012, 8, 2184–2190, doi:10.3762/bjoc.8.246

• -modified biomolecules require longer azobenzene derivatives that undergo large end-to-end distance changes upon photoisomerization. In addition, isomerization that occurs with visible rather than UV irradiation is preferred for biological applications. Results: We report the synthesis and characterization

Hydrophobic analogues of rhodamine B and rhodamine 101: potent fluorescent probes of mitochondria in living C. elegans

• Laurie F. Mottram,
• Safiyyah Forbes,
• Brian D. Ackley and
• Blake R. Peterson

Beilstein J. Org. Chem. 2012, 8, 2156–2165, doi:10.3762/bjoc.8.243

• Science). TLC plates were visualized by UV irradiation (254 nm) or stained with a solution of phosphomolybdic acid and sulfuric acid in ethanol (1:1:20). Flash column chromatography employed ICN SiliTech Silica Gel (32–63 μm). Melting points were measured with a Thomas Hoover capillary melting point

S-Fluorenylmethyl protection of the cysteine side chain upon N^α-Fmoc deprotection

• Johannes W. Wehner and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2012, 8, 2149–2155, doi:10.3762/bjoc.8.242

• , Merck). Detection was effected by UV irradiation and subsequent charring with 10% sulfuric acid in EtOH followed by heat treatment. Flash chromatography was performed on silica gel 60 (230–400 mesh, particle size 0.040–0.063 mm, Merck). Preparative MPLC was performed on a Büchi apparatus by using a

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• total reaction solution “sees” intense UV irradiation from the UV source. This leads to very efficient, uniform irradiation of the whole reaction solution over time. • The UV exposure time can be precisely controlled by the flow-rate and reactor volume. This can address both the under- and over

Photochemistry with laser radiation in condensed phase using miniaturized photoreactors

• Elke Bremus-Köbberling,
• Arnold Gillner,
• Frank Avemaria,
• Céline Réthoré and
• Stefan Bräse

Beilstein J. Org. Chem. 2012, 8, 1213–1218, doi:10.3762/bjoc.8.135

• was shown that a largely better selectivity can be achieved, compared to the one obtained in a standard UV irradiation setup (Figure 2). Experiments were performed in batch as well as flow-injection configuration. The continuous process used allowed us to vary the residence time in the reactor by

Synthesis of new pyrrole–pyridine-based ligands using an in situ Suzuki coupling method

• Matthias Böttger,
• Björn Wiegmann,
• Steffen Schaumburg,
• Peter G. Jones,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2012, 8, 1037–1047, doi:10.3762/bjoc.8.116

• were tried) we noticed smearing of the blue fluorescent product under UV irradiation. Even deactivated aluminium oxide provides enough acidity to split the Boc-moiety, which probably causes the generated amine to partly remain on the column. In the case of 6, using an excess of 19 lead to better yields

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• , associated with the n→π* transition. Upon UV-irradiation, the trans-to-cis photoisomerisation occurs, producing a decrease in the intensity of the 355 nm band and an increase in the 450 nm signal until the photostationary state is reached, that is, the inverse process of that shown in Figure 4 [44]. The

• information-transmitting photochromic switches. Figure 25 shows the information-transmission capability of azo-dye 26 with time. The repeatability of the different optical oscillators was tested by submitting them to consecutive UV-irradiation–dark cycles. The optical photochromic switches reported show no

• -trans isomerisation processes of azobenzenes. Effect of the presence of the electron-withdrawing cyano and nitro groups on the thermal relaxation time in ethanol at 298 K, τ, for the type-I azoderivatives 5 and 6. Transient absorption generated by UV irradiation (λ = 355 nm) for azo-dyes 8 (right) and 9

Enaminones in a multicomponent synthesis of 4-aryldihydropyridines for potential applications in photoinduced intramolecular electron-transfer systems

• Nouria A. Al-Awadi,
• Maher R. Ibrahim,
• Mohamed H. Elnagdi,
• Elizabeth John and
• Yehia A. Ibrahim

Beilstein J. Org. Chem. 2012, 8, 441–447, doi:10.3762/bjoc.8.50

• to the border of the visible region. In the presence of an appropriate electron-acceptor substituent in position 4, the absorbed UV irradiation can cause intramolecular electron transfer, thus converting light into charge separation over a distance of ca. 6 Å. This expectation is based on the recent

Natural product biosyntheses in cyanobacteria: A treasure trove of unique enzymes

• Jan-Christoph Kehr,
• Douglas Gatte Picchi and
• Elke Dittmann

Beilstein J. Org. Chem. 2011, 7, 1622–1635, doi:10.3762/bjoc.7.191

• /protection, and UV-absorption compounds. Cyanobacteria produce two types of sunscreen compounds, induced under UV irradiation: Scytonemin (19) and mycosporine-like amino acids 20 (Figure 11). Biosynthesis of the two groups of compounds has recently been elucidated, providing further examples for the

Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• 4 provided the homoquadricyclane product 12 in 42% yield after 2 h of UV irradiation in the presence of 100 equiv of 1,4-CHD. Under the same conditions, the p-substituted acetylene 3 reacts with 1,4-CHD sluggishly and gave <5% of product after 8.5 h of UV irradiation according to the 1H NMR spectrum

• 3. However, when the reaction was repeated in neat 1,4-CHD, the corresponding homoquadricyclane product 11 was isolated in 95% yield after only 1 h of UV irradiation. This result indicates that the photoaddition reaction of 3 can occur efficiently under more favorable conditions when there is a

• of <1 μM. On the other hand, conjugate 1 displayed strong phototoxicity toward the human melanoma A375 cell line in the nanomolar range (CC50 = 1.49 × 10−7 M) after 10 min of UV irradiation at 360 nm. Conjugates 6 and 7 also showed some phototoxicity. This result of cell proliferation inhibition by

Novel carbazole–pyridine copolymers by an economical method: synthesis, spectroscopic and thermochemical studies

• Aamer Saeed,
• Madiha Irfan and
• Shahid Ameen Samra

Beilstein J. Org. Chem. 2011, 7, 638–647, doi:10.3762/bjoc.7.75

• . DSC graph for polymer P1a. UV–vis spectra of the polymers of (a) series P1 and (b) series P2. Photoluminescence spectra of polymers P1and P2 in CHCl3 solution. (a) Polymers of P2 series in visible light; (b) observed fluorescence (CHCl3 dilute solutions) under UV irradiation (254 nm). Synthesis of the

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• was observed in (c). The UV–vis absorption spectra of the polymerized gel formed by compound 18A in ethanol (10 mg/mL): A, at room temperature after 3 min UV irradiation (λmax = 650 nm); B, at 50 °C ( λmax = 634 nm); C, at 60 °C incubation for 90 min (λmax = 534 nm, other peaks are 582, 636 nm); D

Exceptionally small supramolecular hydrogelators based on aromatic–aromatic interactions

• Junfeng Shi,
• Yuan Gao,
• Zhimou Yang and
• Bing Xu

Beilstein J. Org. Chem. 2011, 7, 167–172, doi:10.3762/bjoc.7.23

• properties. Notably, compound 6 can undergo cis/trans-isomerization upon UV irradiation. Keywords: aromatic–aromatic interaction; cinnamoyl; hydrogel; hydrogelator; supramolecular; Introduction Gels formed by three-dimensional, elastic networks to encapsulate a liquid [1], have many useful properties (e.g

• reason for phase separation, compound 6 was placed in a UV reactor for the same duration. As revealed by the 1H NMR (Figure 1F), a new set of peaks at 5.9 ppm and 6.6 ppm appears after UV irradiation, indicating that cis-6 forms upon the photo-excitation [36]. Since there was no new peak in the range of

• -isomer during UV irradiation. Thus, we infer that the formation of two layers in the gel IV after UV irradiation originates from geometric (cis/trans-) isomerism. Compound 6 also exhibits another interesting phenomenon. On acidification by 1N HCl solution, the solution of 6 (Figure 2A, 2.0 wt %) first

Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers

• Daniel Crespy and
• Katharina Landfester

Beilstein J. Org. Chem. 2010, 6, 1132–1148, doi:10.3762/bjoc.6.130

• that could be cleaved by UV-irradiation, temperature, or by pH change [122]. In order to study the release of encapsulated sulforhodamine dye from the capsules, polyurethane with and without cleavable functionalities were synthesized. Fluorescence spectroscopy of the supernatant obtained by the

• centrifugation of both polymer capsules submitted to different stimuli was recorded and the release of the dye was found to occur on different time-scales in the case of the cleavable shells, i.e., minutes for UV-irradiation, hours for a temperature increase, and days for a pH change. Polycondensation In aqueous

Light-induced olefin metathesis

• Yuval Vidavsky and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2010, 6, 1106–1119, doi:10.3762/bjoc.6.127

• trioxide (MoO3/SiO2) could be activated by UV irradiation under an alkane atmosphere in the metathesis of propene and 1-hexene. More recently, Sundararajan et al. [52][53][54], and Higashimura et al. [55] applied W(CO)6/CX4/hν methodologies for the polymerisation of alkyne derivatives, especially

• , the nitrile complexes displayed low activity even at room temperature. UV irradiation at 364 nm significantly enhanced the activity of all these complexes. The activity of the compounds, including comparisons with thermally active catalysts, are summarised in Table 1. Overall, the polymers obtained

• UV irradiation. The ruthenium complexes 12 showed much higher reactivity in the polymerisation of norbornene, albeit none of these complexes was completely thermally latent for this reaction. The remarkable tolerance of 12b to impurities and water, was highlighted by the fact that polymerisation can

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• 488 nm, the ε-value being a linear function of the DPP content. Upon UV irradiation the copolymers gradually decomposed. The rate of photodecomposition was found to increase with decreasing DPP phenylene comonomer ratio. Two different photoprocesses were recognized: a slow process originating from the

A bivalent glycopeptide to target two putative carbohydrate binding sites on FimH

• Thisbe K. Lindhorst,
• Kathrin Bruegge,
• Andreas Fuchs and
• Oliver Sperling

Beilstein J. Org. Chem. 2010, 6, 801–809, doi:10.3762/bjoc.6.90

• reactions were carried out under an atmosphere of nitrogen or argon. Thin layer chromatography was performed on silica gel plates (GF 254, Merck). Detection was effected by UV irradiation and subsequent charring with 10% sulfuric acid in EtOH followed by heat treatment. Flash chromatography was performed on

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

• -phenols, and diaryl disulfides with perfluoroalkyl iodides in liquid ammonia under UV irradiation Kornblum’s work on nucleophilic substitution in alkyl halides [134][135][136][137] and Bunnett’s reactions with non-activated aromatic substrates [138][139][140][141][142] (under UV irradiation) introduced

• polarity, and in spite of their tendency to undergo homolytic decomposition under UV irradiation, it is probable that they are also able to react with thiolate anions by a similar mechanism. Indeed, they react readily with aliphatic, aromatic and heterocyclic thiols [143][144][145][146], and with seleno

• - [147] and tellurophenols [148] under UV irradiation with formation of corresponding perfluoroalkyl sulfides, -selenides and -tellurides. The original method required liquid ammonia as the solvent and Pyrex glassware. Thiophenol and its derivatives containing both, electron-donating and electron