Controlled synthesis of poly(3-hexylthiophene) in continuous flow

• Helga Seyler,
• Jegadesan Subbiah,
• David J. Jones,
• Andrew B. Holmes and
• Wallace W. H. Wong

Beilstein J. Org. Chem. 2013, 9, 1492–1500, doi:10.3762/bjoc.9.170

• evidence for the quasi-living nature [21] of the polymerization in flow processing (Table 1 and Figure 1). In fact, the molecular-weight data obtained in conventional batch reactions were very similar to those recorded in continuous-flow reactions (Figure 1). Matrix-assisted laser desorption ionization

Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

• Martin Goez and
• Martin Vogtherr

Beilstein J. Org. Chem. 2013, 9, 1448–1454, doi:10.3762/bjoc.9.164

• to radical pairs by laser flash photolysis. Without further action on the part of the experimenter, the radical pair mechanism then creates opposite polarizations in the geminate products, i.e., in the starting materials A and D regenerated by reverse electron transfer, and in the escaping free

• of 1...100 microseconds for suitably chosen substrate concentrations. A radiofrequency pulse (typical duration: microseconds for protons) applied at a certain point of time after the laser flash converts the polarizations present in D at that precise moment into observable coherences and isolates

• them from the further cancelation, which only operates for magnetizations. Hence, a series of such time-resolved CIDNP experiments [13][14][15][16] with different delays between laser flash and observation pulse provides a direct way of measuring the self-exchange rates [17][18][19][20]. Practically

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

• Laura Bekere,
• David Gachet,
• Vladimir Lokshin,
• Wladimir Marine and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2013, 9, 1311–1318, doi:10.3762/bjoc.9.147

• dyes for natural and synthetic fibers [1], optical brighteners in detergents, textiles, polymeric materials [1][2][3] and chemiluminiscent agents [4]. Owing to the high fluorescence quantum yields 1,8-naphthalimides are used as laser dyes [5][6]. Some naphthalimide derivatives have also been reported

• modification of ZnO nanoparticles produced by femtosecond laser ablation was demonstrated to afford nanohybrid materials for biophotonic applications [13][14]. Results and Discussion Synthesis and characterization Yellow 4-amino-1,8-naphthalimides are usually synthesized in two steps. The first step is the

• square of the laser power shown in the inset (Figure 5) clearly demonstrates the two-photon excitation nature. Quantum mechanical calculations Quantum mechanical calculations were performed for derivative 4 to gain deeper insight into the nature of the longest wavelength transition and to estimate the

Linkage of α-cyclodextrin-terminated poly(dimethylsiloxanes) by inclusion of quasi bifunctional ferrocene

• Helmut Ritter,
• Berit Knudsen and
• Valerij Durnev

Beilstein J. Org. Chem. 2013, 9, 1278–1284, doi:10.3762/bjoc.9.144

• -flight mass spectrometer. The device operates both in the linear mode and in reflector mode with a 337 nm nitrogen laser. The samples were dissolved in a suitable solvent. A dithranol (DIT) or 2,5-dihydroxybenzoic acid (DHB) matrix was used. The IR spectra were recorded with a Fourier transform infrared

• spectrometer FTIR Nicolet 5SXB. The calibration of the wave numbers was done by using a He–Ne laser. The ATR measurements were performed with a Specac Golden Gate diamond-ATR unit. For the NMR measurements at 300 MHz a Bruker Avance III - 300 (2010) spectrometer was used. The magnetic field strength was 7.05 T

• hydrodynamic diameters of the derivatives and their complexes were determined by use of dynamic light scattering (DLS) in the back scattering mode with a Malvern Zetasizer Nano ZS ZEN3600 at a laser wavelength of 633 nm and a detection angle of 173°. The samples were dissolved in chloroform (10 mg·mL−1) and

Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

• Jianhuai Ye,
• Yoshihisa Fujiwara and
• Manabu Abe

Beilstein J. Org. Chem. 2013, 9, 925–933, doi:10.3762/bjoc.9.106

• entropy effect were found to play crucial roles in increasing the lifetime. Keywords: laser flash photolysis; lifetime; singlet diradicals (biradicals); substituent effect; π-single bond; Introduction Localized singlet diradicals are key intermediates in processes involving the homolytic bond-cleavage

• diradicals. Thus, the aryl substituent was introduced at C(1), C(2), or/and C(3) positions of the diradicals DRd–g, and the substituent effects on the lifetime of the singlet diradicals were compared with the lifetime of a phenyl-group-substituted diradical DRc and the parent diradical DRa. The laser flash

• . Detection of singlet diradicals DRc–g. The detection of singlet diradicals DRc–g was examined by the photochemical denitrogenation of azoalkanes AZc–g in a glassy matrix of 2-methyltetrahydrofurane (MTHF) at 80 K, [AZ] ≈ 4 × 10−3 mol/L, and by the laser flash photolysis experiments of AZc–g at room

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

• Sofia Telitel,
• Frédéric Dumur,
• Thomas Faury,
• Bernadette Graff,
• Mohamad-Ali Tehfe,
• Didier Gigmes,
• Jean-Pierre Fouassier and
• Jacques Lalevée

Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101

• photocatalysts. Successful results in terms of rates of polymerization and final conversions were obtained. The strong MO coupling between the six different cores and the pyrene moiety was studied by DFT calculations. The different chemical intermediates are characterized by ESR and laser flash photolysis

• –10 mW cm−2). Recent works have aimed at working under soft irradiation conditions (near-UV–vis light, low light intensity), which allows the use of Xe lamps, laser diodes, solar radiation, household halogen lamps, fluorescent bulbs and blue, green and white LEDs (see a recent review in [1]). New high

• , Py_3, Py_4, Py_9, Py_10) two functionalized triazines (Py_7, Py_12), a triphenylamine (Py_6), a carbazole (Py_11) and a benzothiadiazole (Py_8) (Scheme 3). The idea is to get a high absorption around 380–410 nm where Xe–Hg lamps, Xe lamps, LED, laser diodes and even household halogen lamps are usable

Superstructures of fluorescent cyclodextrin via click-reaction

• Arkadius Maciollek,
• Helmut Ritter and
• Rainer Beckert

Beilstein J. Org. Chem. 2013, 9, 827–831, doi:10.3762/bjoc.9.94

• from Deutero GmbH, Germany. 1H NMR spectra were recorded on a Bruker Avance DRX 300 at 20 °C, shifts (δ) are given relative to signals arising from the solvent. FT IR spectra were recorded on a Nicolet 6700 FT IR spectrometer equipped with an ATR unit. Matrix-assisted laser desorption/ionization-time

• -of-flight mass spectrometry (MALDI–TOFMS) was performed on a Bruker Ultraflex TOF mass spectrometer. Ions were formed with a pulsed nitrogen laser (25 Hz, 337 nm) and the molecular masses were recorded in linear mode. 2,5-Dihydroxybenzoic acid (DBH) in acetonitrile/water was used as a matrix. Mass

• Elmer LS55 luminescence spectrometer. AF4 measurements in ultrapure water were carried out on a combined system comprising the following elements: refractive index detector Optilabrex (Wyatt Technologies, laser wavelength 658 nm), three angle light scattering detector miniDawn TREOS (Wyatt Technologies

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

• Maurizio Fagnoni,
• Stefano Protti,
• Davide Ravelli and
• Angelo Albini

Beilstein J. Org. Chem. 2013, 9, 800–808, doi:10.3762/bjoc.9.91

• the presence of a variety of donors (D–X, step a). In all of the above cases, the generated radical anion (A–Y•−) is a persistent species easily detected by laser flash photolysis. This approach applies to a variety of donors, including amines [12][13], carboxylic acids or their derivatives [14][15

• further tertiary amines, iPr3N causes a somewhat slower accumulation (the conformation of the radical cation is known to be less favorable for deprotonation) [48][49][50], and DABCO (for which deprotonation is impossible [51][52]) causes no detectable formation of TCB•−. Indeed, previous laser flash

Photoionisation of the tropyl radical

• Kathrin H. Fischer,
• Patrick Hemberger,
• Andras Bodi and
• Ingo Fischer

Beilstein J. Org. Chem. 2013, 9, 681–688, doi:10.3762/bjoc.9.77

• ) [24], cyclopropenylidene [25] and fulvenallenyl [26]. In the case of allyl [27][28] and propargyl [29] they are in excellent agreement with high-resolution laser studies. Such data are important for the derivation of bond dissociation energies and heats of formation of radicals, but also aid in the in

New reactive intermediates in organic chemistry

• Götz Bucher

Beilstein J. Org. Chem. 2013, 9, 613–614, doi:10.3762/bjoc.9.67

• and hence can be studied for an extended period of time; or laser flash photolysis, where the reactive intermediate is generated by a very short pulse of laser light, and can be investigated in real time; or specialised mass-spectrometric techniques such as ion cyclotron resonance MS. Due to the

Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

• Martin Goez,
• Isabell Frisch and
• Ingo Sartorius

Beilstein J. Org. Chem. 2013, 9, 437–446, doi:10.3762/bjoc.9.46

• pulsed laser triggers a photoreaction; after a short delay, the polarizations of the products are probed with an NMR pulse; variation of the delay yields the kinetics. The method is very well suited to study bimolecular reactions of the free radicals, because typical NMR pulses are of microsecond

• bimolecular reaction; as a control experiment we, therefore, varied the concentrations of free radicals by varying the laser energy. The results are displayed in Figure 2. As is clearly discernible, the measured exchange rates remained constant over a concentration range spanning a factor of about 20. Because

• magnitude larger in the case of XA (in fact so unusually strong that for aligning the optical path of the excitation laser we found XA/DABCO to be the best system, other points in its favour being that it is extremely photostable and that its NMR signal is a singlet). This remarkable signal strength must

A peptidic hydrogel that may behave as a “Trojan Horse”

• Nicola Castellucci,
• Giorgio Sartor,
• Natalia Calonghi,
• Carola Parolin,
• Giuseppe Falini and
• Claudia Tomasini

Beilstein J. Org. Chem. 2013, 9, 417–424, doi:10.3762/bjoc.9.44

• by confocal laser scanning microscopy, we prepared also three fluorescent compounds B, C and D, all containing the fluorescent dansyl group (Dans) [24]. First we prepared hydrogels 1 and 2 (Table 1), both containing A and a mixture of water and ethanol in 9:1 ratio and 1:1 ratio, respectively. Both

• cells were grown on glass coverslips for 24 h before being exposed to hydrogels for 30 min. Confocal laser scanning microscopy shows that all the hydrogels internalize in IGROV-1 cells (as indicated by the green fluorescence in the cytoplasm Figure 4), but very few green spots are present in Figure 4a

• with small amounts of dansyl-containing compounds, needed to show the cellular uptake into IGROV-1 cells by confocal laser scanning microscopy. These gels are readily internalized by cells and are biologically inactive. In contrast, the hydrogel 6 formed only by B and a water/ethanol mixture is

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

• at ca. 10 K with green light (514 nm from Ar+ laser) leads to convertion of the LS state to the metastable HS state. The optical spectrum of the white spot (ca. 1 mm in diameter) is virtually identical to that measured at 300 K. Mössbauer spectroscopy is ideally suited to follow the light-induced

• recorded with a polycrystalline sample of [Fe(ptz)6](BF4)2, which was first cooled to 15 K, at which the sample is in the LS state (upper left). Irradiating the sample with green light (ca. 500 nm from an argon ion laser) at 15 K converts the LS state (resonance signal shown in blue) quantitatively to the

• and HS ground states are displaced due to the fact that the metal-ion–donor-atom distance in the HS state is weaker and therefore longer compared to the stronger and therefore shorter bond distance in the LS state (Figure 1). Green light (514 nm from an Argon ion laser) excites the LS state (1A1) by

From bead to flask: Synthesis of a complex β-amido-amide for probe-development studies

• Kevin S. Martin,
• Cristian Soldi,
• Kellan N. Candee,
• Hiromi I. Wettersten,
• Robert H. Weiss and
• Jared T. Shaw

Beilstein J. Org. Chem. 2013, 9, 260–264, doi:10.3762/bjoc.9.31

• laser desorption/ionization mass spectrometry [14]. In the current synthesis, we set out to develop a concise and scalable solution-phase route to 1 and provide characterization data for 1 and all intermediate compounds. In our retrosynthetic analysis, we envisioned 1 coming from acylation of

Asymmetric synthesis of host-directed inhibitors of myxoviruses

• Terry W. Moore,
• Kasinath Sana,
• Dan Yan,
• Pahk Thepchatri,
• John M. Ndungu,
• Manohar T. Saindane,
• Mark A. Lockwood,
• Michael G. Natchus,
• Dennis C. Liotta,
• Richard K. Plemper,
• James P. Snyder and
• Aiming Sun

Beilstein J. Org. Chem. 2013, 9, 197–203, doi:10.3762/bjoc.9.23

• substituted phenyl rings or heterocyclic rings. The compounds were initially assayed in two screening assays: (1) a measles virus cytopathic effect (CPE) reduction assay [12] and (2) a solubility assay based on laser nephelometry [18]. Unfortunately, compounds with the highest aqueous solubilities (>100 µg/mL

• compounds were measured by using laser nephelometry at pH 3.0, 5.0, and 7.4 (Table 2). Analysis of the data reveals several trends. First, with the exception of a single case in which enantiomer potencies are similar (14c, ΔEC50 < 3-fold), six other comparisons reveal the (S)-enantiomer to be more active

• molecules described herein, a more detailed description of the laser nephelometry assay, and data tables for the crystal structures of (S)-1 and (R)-1. Supporting Information File 362: Detailed synthetic procedures and characterization data. Acknowledgments This work was supported, in part, by Public

A chemist and biologist talk to each other about caged neurotransmitters

• Graham C.R. Ellis-Davies

Beilstein J. Org. Chem. 2013, 9, 64–73, doi:10.3762/bjoc.9.8

• most purposes. I have been confused by some reports of “rates of reactions” being given as a time course for steady-state photolysis over many seconds or minutes [45], whereas other reports show rates from laser flash photolysis [3][61]. Can you help clarify this? Chemist: Only the latter should be

Influence of cyclodextrin on the solubility and the polymerization of (meth)acrylated Triton^® X-100

• Melanie Kemnitz and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 2176–2183, doi:10.3762/bjoc.8.245

• , matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF MS), dynamic light scattering (DLS), gel-permeation chromatography (GPC) and turbidity measurements. Additionally, the viscosity change of the methacrylic homopolymer with RAMEB-CD was evaluated. Keywords: (meth)acrylated Triton

• equipped with an ATR unit at rt. The measurements were performed in the range of 4000–300 cm−1. DLS data were recorded in backscattering mode on a Malvern Zetasizer Nano ZS ZEN 3600 at a temperature of 20 °C with a laser wavelength of 633 nm and a detection angle of 173°. Measured solutions contained 5 mg

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

• tissues by confocal laser scanning microscopy after treatment for 2 h at concentrations as low as 100 picomolar. Because transgenes are poorly expressed in the germline of these animals, these small molecules represent superior tools for labeling dynamic mitochondria in this tissue compared with the

• distribution of synthetic rhodamines and analogues in vivo, living adult C. elegans were initially subjected to an acute treatment followed by confocal laser scanning microscopy of mechanically immobilized whole animals (20× objective). In contrast to previous reports where treatment with rhodamines for 36–48

• 2.5% (w/v) polystyrene beads (50 nm, Bangs Laboratory) to prevent movement. Imaging employed an Olympus FV1000 laser scanning confocal microscope and Fluoview software. Images were acquired with Plan-apochromat objectives. Structures of known fluorophores (1–8) and novel hydrophobic analogues of

Chemical modification allows phallotoxins and amatoxins to be used as tools in cell biology

• Jan Anderl,
• Hartmut Echner and
• Heinz Faulstich

Beilstein J. Org. Chem. 2012, 8, 2072–2084, doi:10.3762/bjoc.8.233

• . 3.4, Kratos Kompact Software Ver. 5.2.0) and were usually the average of 50–100 individual laser shots across the width of the sample spot. Data were smoothed and baseline-corrected, generally with a window width of 30 channels. Polymers linked to aminophalloidin Poly-(L)-lysine (hydrobromide; Mr

• confocal laser scanning microscope TCS SP2 (Leica Microsystems, Heidelberg/Mannheim, Germany), equipped with an inverted microscope DMIRE2 and an incubation chamber (Pe-Con Erbach, Germany). Image data stacks and time-lapse studies of the live cells were obtained at 37 °C and in 5% CO2 atmosphere with a

Cyclodextrin-induced host–guest effects of classically prepared poly(NIPAM) bearing azo-dye end groups

• Gero Maatz,
• Arkadius Maciollek and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 1929–1935, doi:10.3762/bjoc.8.224

• 210 Plus UV–visible spectrophotometer (Analytik Jena AG, Germany). SEC-MALS measurements were carried out on a combined system comprising the following elements: refractive-index detector Optilabrex (Wyatt Technologies, laser wavelength 658 nm), three-angle light-scattering detector miniDawn TREOS

• (Wyatt Technologies, laser wavelength 658 nm, detector angles at 43.5°, 90.0° and 136.5°), UV detector Waters 486 (Waters), column set of HEMAbio 300 and HEMAbio 100 (MZ-Analysentechnik), pump, degasser and autosampler (Agilent 1200, Agilent technologies). The eluent was ultrapure water at a flow rate 1

• -point photometer TP1. The relative transmission of a laser beam with a wavelength of 670 nm was recorded for each experiment. The measurements were performed in a temperature range between 5 and 60 °C and at a heating rate of 1 °C min−1 by using Hellma Suprasil precision cells 110 Q-S. Critical solution

Self-assembled organic–inorganic magnetic hybrid adsorbent ferrite based on cyclodextrin nanoparticles

• Ângelo M. L. Denadai,
• Frederico B. De Sousa,
• Joel J. Passos,
• Fernando C. Guatimosim,
• Kirla D. Barbosa,
• Ana E. Burgos,
• Fernando Castro de Oliveira,
• Jeann C. da Silva,
• Bernardo R. A. Neves,
• Nelcy D. S. Mohallem and
• Rubén D. Sinisterra

Beilstein J. Org. Chem. 2012, 8, 1867–1876, doi:10.3762/bjoc.8.215

• by using a Sonics Vibra Cell coupled with a microprobe, at 25% amplitude for 5 min. Samples were measured by monochromatic light (10 mW He–Ne laser, wavelength 632.4 nm) and the scattered light intensity was measured in an angle of 173°. Hydrodynamic diameters were measured five times independently

• potential ZP measurements were carried out in a Malvern Zetasizer Nano Series ZS (Malvern Instruments, UK) with a 633 nm red laser, through the Malvern Standard M3 technique (with Doppler electrophoresis as the basic principle of operation) by using capillary cell (DPS1060) [37][47]. Average of the ZP

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• anticoagulants, antifungal agents, antioxidants, or as anthelmintic, hypnotic and cytotoxic agents [1][2][3][4]. Due to their fluorescent properties, coumarins are also widely used as agrochemicals, additives in cosmetics and food, optical brighteners, and dispersed fluorescent and tunable laser-dye optical

Influence of cyclodextrin on the solubility of a classically prepared 2-vinylcyclopropane macromonomer in aqueous solution

• Helmut Ritter,
• Jia Cheng and
• Monir Tabatabai

Beilstein J. Org. Chem. 2012, 8, 1528–1535, doi:10.3762/bjoc.8.173

• ) instrument equipped with a He–Ne-laser and an Avalanche photodiode detector. The turbidity measurements were carried out using a power-regulated semiconductor laser (λ = 670 nm) and a silicon photodiode in a TP1 turbidity photometer from TEPPER-Analytik. Glass-transition temperatures (Tg) were measured using

• at 1 °C/min−1 in a magnetically stirred cell; values of the cloud points were defined as the temperature at which the deepest point of the derivative curve was achieved. MALDI-TOF MS was performed on a Bruker Ultraflex TDF mass spectrometer using a 337 nm nitrogen laser. GPC analyses were performed

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• (Figure 3d) were linear, with their slopes giving the second-order rate constants k2 (M–1 s–1) [35][36]. For the investigations of reactions of the iminium ions on the micro- and nanosecond time scale, laser flash spectroscopy was employed [37]. As tertiary phosphines PR3 (10) are known to be excellent

• photonucleofuges [38][39][40][41], the stable iminium salts 3-PF6 were treated with tertiary phosphines 10 at room temperature to give the enamino-phosphonium ions 11 instantaneously (Figure 4a). Their irradiation with 7 ns laser pulses (266 nm) regenerated the iminium ions, the decay of which was monitored

• conjugate additions of nucleophiles [23][24][25][26][27][28]. Kinetics of the reactions of the iminium ion 3a with the silylated ketene acetal 7a [35]. Laser flash photolytic generation of iminium ions 3a. Correlations of the reactivities of the iminium ions 3a and 3b toward nucleophiles with the

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

• Elke Bremus-Kobberling Arnold Gillner Frank Avemaria Celine Rethore Stefan Brase Fraunhofer Institute for Laser Technology, Steinbachstrasse 15, D-52074 Aachen, Germany Institute of Organic Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 6, D-76131 Karlsruhe, Germany Institute of

• Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany 10.3762/bjoc.8.135 Abstract Miniaturized microreactors enable photochemistry with laser irradiation in flow mode to convert azidobiphenyl into carbazole with high efficiency

• . Keywords: azides; chemical diversity; flow chemistry; heterocycles; laser; micro reactor; Introduction Classical combinatorial chemistry [1][2] approaches usually aim at the synthesis of multi-milligram amounts of new compounds to extend screening decks used in multiple screening campaigns [3]. An