Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• complementing the series, but did not yet describe synthetic details [7]. Xue et al. published a donor–acceptor photosensitizer for dye-sensitized solar cells, in which the N-phenylated SN4 unit serves as bridge between donor and acceptor moieties [34]. Further replacement of sulfur by nitrogen can lead to

• opposite effects. The basic SN4 and SN4'' frameworks represent novel core molecules for further functionalization, for example with terminal acceptor groups, leading to highly absorbing dye molecules for application in organic solar cells. Heteroacenes: tetrathienoacene (TTA), S,N-heteroacenes SN4, SN4

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• employed to gain insight into the experimental data. Results and Discussion Synthesis As depicted in Scheme 1, dye 2 was obtained in good yield by reacting malononitrile and 4-aminoacetophenone (compound 1) according to our previous published procedure [31][32]. The styryl-based organic chromophores 3–7

• little effect on the shift for dye 3 (6 nm). In case of the Schiff bases 8–11, similar bathochromic shifts were observed. In addition, experimentally, there was no solvatochromic behavior observed for dyes 7 and 12 as was predicted by theoretical calculations. Based on theoretical calculations, the main

• MeOH and ACN, and the emission band of dye 3 was red-shifted by 60 nm from PhMe (λemmax = 584 nm) to DMSO (λemmax = 644 nm) (Figure 3). The dyes showed considerably different fluorescence color magnitudes with changing polarity except for compound 12 that was non-fluorescent. The fluorescence intensity

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

• Patrizia Andreozzi,
• Lorenza Tamberi,
• Elisamaria Tasca,
• Gina Elena Giacomazzo,
• Marta Martinez,
• Mirko Severi,
• Marco Marradi,
• Stefano Cicchi,
• Sergio Moya,
• Giacomo Biagiotti and
• Barbara Richichi

Beilstein J. Org. Chem. 2020, 16, 2272–2281, doi:10.3762/bjoc.16.188

• with small molecules, in a green and scalable process. Results and Discussion The boron dipyrromethene dye 1 bearing a phenylboronic acid moiety (PBA) at the meso position of the BODIPY core (Scheme 1) was prepared in four synthetic steps starting from 4-formylbenzeneboronic acid (2) and pyrrole (3

• excess of PBA (more than 60-fold excess of PBA to dextran, in a glucose/PBA 1:1 molar ratio reaction) was employed. However, the resulting dextran functionalization was low (1.6 PBA units out of 60 glucose units). In our studies we used PBA-BODIPY (1), a dye which proved to show excellent optical

• by UV–vis spectroscopy (λmax = 508–511 nm). The DMSO/ethanol mixtures and ethanol solutions were dried under vacuum, the recovered dye was solubilized in DMSO, and the UV–vis spectra were recorded. The amount of recovered PBA-BODIPY (1) was estimated (Figure 2A), using the molar extinction

Naphthalene diimide bis-guanidinio-carbonyl-pyrrole as a pH-switchable threading DNA intercalator

• Poulami Jana,
• Filip Šupljika,
• Carsten Schmuck and
• Ivo Piantanida

Beilstein J. Org. Chem. 2020, 16, 2201–2211, doi:10.3762/bjoc.16.185

• ][6]. Among many strategies to achieve novel dye properties, one is based on combining two or more DNA/RNA binding modes in one small molecule (dye), thus building elaborate constructs which are able to recognise and report between slightly different DNA/RNA structures [2][7]. For the recognition

• not observe any emission, neither for single dye binding to DNA, nor in crowding conditions (excess of dye over DNA binding sites) at which eventually fluorescent excimers could be formed. Interactions with DNA/RNA Because of significant differences in the protonation states of compound 4, studies

• longer incubation times [23][26][27], the time required for reaching equilibrium was checked by repeatedly collecting UV–vis spectra of compound 4 upon the additions of DNA or RNA aliquots to the dye solution in 10 s intervals. The results showed that an incubation period of 180 s proved to be sufficient

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• , triplet state energies and lifetimes of several small organic molecule/dye PSCats. Figure 7 shows the corresponding information for selected prototypical transition metal complexes. 2.2 Fluorination reagents An extensive discussion on the different types of fluorination reagents is beyond the scope of

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

• Annike Weißenstein,
• Myroslav O. Vysotsky,
• Ivo Piantanida and
• Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

• interacted with ds-DNA/RNA by threading intercalation. Different from a reference NDI dye with identical visible range absorbance (520–540 nm) and Stokes shifts in emission (+60 nm, quantum yield > 0.2), only these amino acid–NDI conjugates showed selective fluorimetric response for GC-DNA in respect to AT(U

• : for instance, binding of a large aromatic dye by aromatic stacking on the terminal base pairs [35], as a competitive binding mode to expected intercalation. Further, the chosen DNA/RNA polynucleotides are characterised by different secondary structures [36][37]: poly(dA-dT)2 representing the B-helical

• we took advantage of the fluorescence of 3a,b, and 5. Since suspected threading intercalation usually requires longer incubation times, the time required for reaching equilibrium was checked by repeatedly collecting emission spectra upon additions of DNA or RNA aliquots to the dye solution

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• ]. The band at 1678 cm−1 was the characteristic feature of an antiparallel conformation of the sheet structure or the β-turn structure [61]. To further confirm the β-sheet formation, we performed a ThT fluorescence spectroscopy assay. ThT is a widely used fluorescent dye that is amyloid-specific and can

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• , using multiwell plates and registering data on the fluorescence intensity and fluorescence localization in thousands of cells per condition, at HT [56][57][58][59]. To properly assess its potential, automated HC imaging was optimized first. The fluorescence of the Hoechst dye and the GFP of the fusion

• the reaction of 25 with HaloTags on mitochondria (b). Afterwards, the unreacted HaloTags are labeled with the reporter 26 for quantification (c). Examples from the automated HC imaging of stable HGM cells with HaloTag–GFP on mitochondria, labeled with 26 and Hoechst dye. a) GFP channel (left) and cell

• selection (right), showing the cell body mask (light blue areas) and the mitochondrial mask (yellow areas). b) Overlay image of the GFP (green), 26 (red), and the Hoechst dye (blue) channels, showing off-target fluorescence from 26 (white arrows). Scale bar: 10 µm. Evaluation of the automated HC imaging of

Three new O-isocrotonyl-3-hydroxybutyric acid congeners produced by a sea anemone-derived marine bacterium of the genus Vibrio

• Dandan Li,
• Enjuro Harunari,
• Tao Zhou,
• Naoya Oku and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1869–1874, doi:10.3762/bjoc.16.154

• affected. After incubating the test plate for 84 h, 100 μL of the medium containing MTT 1 mg/mL was added to each well, and the plate was further incubated for 4 h. The medium was carefully removed by aspiration, and formazan dye formed at the bottom of the wells was solubilized by the addition of 150 μL

Mechanochemical green synthesis of hyper-crosslinked cyclodextrin polymers

• Alberto Rubin Pedrazzo,
• Fabrizio Caldera,
• Marco Zanetti,
• Silvia Lucia Appleton,
• Nilesh Kumar Dhakar and
• Francesco Trotta

Beilstein J. Org. Chem. 2020, 16, 1554–1563, doi:10.3762/bjoc.16.127

• instance, dye-modified cyclodextrins and CD derivatives have found wide use for the preparation of chemical sensors [24][25]. As CDs and consequently CD nanosponges can be easily coupled with fluorophores, they could find applications in the pharmacological area, for example, as biological markers, in

• nucleophilic carboxylic group. The simplified schematic reaction (previously reported by Staab [31] and more recently by Jadhav et al. [33]), with the relative ζ-pot of nanoparticles after functionalization, is presented in Figure 8. Through a simple reaction in closed vials with an excess (dye/CD ratio) of

• the organic dye, a covalent bond formation with the still reactive NS was achieved. As shown by elemental analysis, after PS extraction, the amount of nitrogen and therefore of reactive IM was very low. The experiment was conducted on nanosponges having 1:2, 1:4, 1:8 βCD/CDI ratios, and good results

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• charge–transfer transitions [95]. These transitions are commonly observed in metal–organic framework (MOF) HPCats, discussed more in Section 2.5. Dye-sensitised semiconductor photocatalysts have organic photosensitiser molecules immobilised to their surface. This strategy is typically used to activate a

• density on the TiO2 surface at a lower pH value, which favours the adsorption of the dye via its negatively charged sulfonate groups. However, at a natural pH value, the increasing dye concentration gradually raises the pH value of the system and negatively charges the TiO2 surface, leading to an

• electrostatic repulsion that prevents the dye adsorption. 2.2 Organic semiconductor photocatalysis Polyaniline was the first conductive polymer reported by Henry Letheby in 1862 [99][100], but the potential of organic electronics was not realised until the 1960s, and the seminal work of Heeger, MacDiarmid, and

4-Hydroxy-3-methyl-2(1H)-quinolone, originally discovered from a Brassicaceae plant, produced by a soil bacterium of the genus Burkholderia sp.: determination of a preferred tautomer and antioxidant activity

• Dandan Li,
• Naoya Oku,
• Yukiko Shinozaki,
• Yoichi Kurokawa and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1489–1494, doi:10.3762/bjoc.16.124

• -colored CAS stock solution (50 μL) and further brought up to 100 μL with H2O (final concentration of 1: 160 mM). After 10 min at an ambient temperature, the solution turned orange due to the loss of Fe3+ from the indicator CAS dye, indicating positive to the iron-binding ability of 1. A prolonged reaction

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• the design of dye-sensitized solar cells (DSSC) [4]. Typical methods for the construction of a phenanthrene core involve transition-metal-catalyzed cycloisomerizations starting from arynes [5][6], o-alkynyl-biaryls [7][8], or substituted N-tosylhydrazones [9]. However, since the introduction in 1964

• recourse to the photoorganocatalyst eosin B dye [65]. The generation of phenyl radicals from arylhydrazines was assured even when using the covalent organic framework 2D-COF-1 in place of eosin B [66]. Notably, the use of 2D-COF-1 allowed to extend the protocol to the synthesis of 6-alkylphenanthridines

Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

• Kazuyuki Sato,
• Akira Kawasaki,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2020, 16, 1411–1417, doi:10.3762/bjoc.16.117

• with 2c. This observation suggested that the strong electronegativity of fluorine might affect the electron density on the isoxazole ring. Synthesis of boron ketoiminates and α-fluorinated boron ketoiminates Boron ketoiminates (BKIs, 6) are one of the new types of boron-chelating dye [34][35][36][37

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• ][20][21][22][23][24][25]. Most of these reports are organized according to the structural features of the dye and/or their applications in synthetic chemistry. In contrast, this review will focus on the different possible conceptual approaches based on organic photocatalysts for the generation of

• reported a visible light-promoted photochemical reductive decarboxylation/alkylation of carboxylic acid analogs (Scheme 4) [45]. In this protocol, the carboxylic acids are converted into the corresponding RAE 4.1 by a condensation with N-hydroxyphthalimide. The organic dye eosin Y (OD13, E(PC/PC−) ≈ −1.1 V

• after the fragmentation of the oxidized form. Due to their attitude towards SET oxidations, these substrates are valuable alkyl radical precursors; however, they are generally less available than carboxylic acids, and the fragmentations release stoichiometric amounts of byproducts. The organic dye

A smart deoxyribozyme-based fluorescent sensor for in vitro detection of androgen receptor mRNA

• Ekaterina A. Bryushkova,
• Erik R. Gandalipov and
• Julia V. Nuzhina

Beilstein J. Org. Chem. 2020, 16, 1135–1141, doi:10.3762/bjoc.16.100

• target 60-AR_RNA, and connected with T2 and T3 strands through polythymidine linkers (Figure 1A). The MGA strands can hybridize with each other and attach a molecule of malachite green dye (Figure 1C and D) only in the presence of target mRNA. It provided the high specificity of SDFS. After being

• enclosed inside a hybridized MGA, malachite green dye produces a signal (648 nm) after excitation on 610 nm, which is easily detectable by a fluorescence spectrophotometer. The complete SDFS was assembled by annealing the individual component strands (T1–T5) to each other. The efficiency of the SDFS

• malachite green dye was 25 μM. After incubation fluorescence measurement was conducted using fluorescence spectrophotometry (610/648 nm) (Figure 2A, B, and C) and the cleavage was verified by denaturing PAGE (Figure 2D). According to the densitometry analysis of PAGE, after 6 h of incubation at 37 °C around

Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties

• Nuray Altinolcek,
• Ahmet Battal,
• Mustafa Tavasli,
• William J. Peveler,
• Holly A. Yu and
• Peter J. Skabara

Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93

• , respectively. Keywords: carbazole; electrochemistry; fluorescence; formyl group; solvatochromism; Introduction Carbazole derivatives have found many different applications in a variety of technologically important areas, such as organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), dye

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• fluorescent dye that is tethered to an acetyllysine-containing peptide. If the acetyl moiety of the fluorophore is enzymatically hydrolyzed by HDAC8, it will produce a strongly fluorescent signal at 360 nm. Table 1 shows the percentage of HDAC8 inhibition at 100, 10, and 1 µM concentration of the designed

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• meso-position comprising either electron-donating or electron-withdrawing substituents complement the design of tailor made absorption [52][53][54]. The fact that many investigations were pursued in the visible range assigned these materials in general as dyes, which should not be correct. The term dye

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• compound, with applications ranging from thickening agents (carboxymethyl cellulose, E466) [1][2], herbicides (2,4-dichlorophenoxyacetic acid), cosmetics (cocamidopropyl betaine), dyes (indigo vat dye) [3], to pharmaceuticals (ibuprofen, glycine, malonates) [4] (see Figure 1). Many reactions with

• by the work of Yoon, Stephenson and MacMillan [11]. By selective excitation of an organic or organometallic dye by visible light a species is formed that can act as a single-electron oxidant and single-electron reductant. In this way reactive radical intermediates can be formed catalytically in situ

• -yl)-10-(naphthalen-1-yl)-10H-phenoxazine instead of [Ir(ppy)3] as the photoredox catalyst had no beneficial effect on the yield or conversion, and also led to the formation of a precipitate. However, the precipitate that was formed when the organic dye 5,10-di(naphthalene-2-yl)-5,10-dihydrophenazine

Two antibacterial and PPARα/γ-agonistic unsaturated keto fatty acids from a coral-associated actinomycete of the genus Micrococcus

• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku,
• Nobuyasu Matsuura,
• Agus Trianto and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 297–304, doi:10.3762/bjoc.16.29

• well. After incubating for 4 h at 37 °C, the medium was carefully removed by a suction aspirator, and formazan dye, formed by respiratory reduction by living cells, was quantified by the absorption at 450 nm, read by a microplate reader to calculate the rate of cell growth inhibition at each

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• photoredox catalyst 6 [93]. Significantly, the use of this organic dye was much more feasible and economical as compared to other transition metal photoredox catalysts. The group worked with a dual visible light photoredox catalytic system by combining photoredox catalyst 6 with a Pd catalyst in the presence

Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin: experimental and computational evidence for intramolecular and intermolecular C–F···H–C bonds

• Vuyisa Mzozoyana,
• Fanie R. van Heerden and
• Craig Grimmer

Beilstein J. Org. Chem. 2020, 16, 190–199, doi:10.3762/bjoc.16.22

• coumarins have been identified from natural sources [1][2]. Coumarins have been reported to play a vital role as food and cosmetics constituents, cigarette additives, and dye-sensitized solar cells [3][4]. In addition, coumarins possess some biological activities such as anti-inflammatory [5], antitumor [6

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

• Lorenzo Sansalone,
• Jun Zhao,
• Matthew T. Richers and
• Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

• an internal solution containing (in mM): 135 potassium gluconate, 4 MgCl2, 10 HEPES, 4 Na2-ATP, 0.4 Na2-GTP, 10 Na2-phosphocreatine, pH 7.35. The red fluorescent dye Alexa 594 (0.05 mM, ThermoFisher Scientific, Waltham, MA, USA) was added to visualize the morphology of the neurons. Normal ACSF was

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• liberation of Ca2+ upon photexcitation in solution, azobenzene macrocyle 1 was used as a reversible Ca2+ photoejector in the presence of a Ca2+-selective “turn-on” fluorescent probe (3, Figure 7) [41]. The fluorescence of BODIPY dye 3 in the absence of calcium, is quenched by an intramolecular photoinduced

• electron-transfer reaction, while ion binding blocks this quenching pathway restoring emission. Thus, ion liberation from 1 and transfer to 3 would result in a fluorescence off–on switching of the latter. To perform the ion-transfer experiment, the fluorescent dye is loaded with one equivalent of Ca2