Metal-mediated base pairs in parallel-stranded DNA

• Jens Müller

Beilstein J. Org. Chem. 2017, 13, 2671–2681, doi:10.3762/bjoc.13.265

• base pair (Scheme 4e) within regular B-DNA did not include any data on the stabilizing effect of the Ag(I) ion coordination but unequivocally confirmed metal-mediated base pair formation via the quenching of the intrinsic fluorescence of MePC [61]. The 2PyrPC–Ag(I)–C and 3PyrPC–Ag(I)–C base pairs

A concise flow synthesis of indole-3-carboxylic ester and its derivatisation to an auxin mimic

• Marcus Baumann,
• Ian R. Baxendale and
• Fabien Deplante

Beilstein J. Org. Chem. 2017, 13, 2549–2560, doi:10.3762/bjoc.13.251

• , temperature and reagent stoichiometry – selected results are presented in Table 1. Although DMF and MeCN were shown to be excellent solvents for the reaction (Table 1, entries 3–6, 10, 15–23, and 26) we encountered difficulties in efficiently extracting the product upon quenching the reactions (1 M HCl

• positioned run-off. At flow rates of 0.5–1.2 mL/min emanating from the main reactor this unit performed reliably giving excellent quenching and separation. However, at higher flow rates issues were encountered with incomplete partitioning (some emulsion formation) of the biphasic mixture resulting in the

• the problematic mixing chip with various configured T- and Y-connectors but this immediately gave other issues due to incomplete quenching which resulted in poor product recovery and associated contamination. A more straightforward approach proved to be to introduce a flow stratification zone prior to

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• 3nπ* state decays nonradiatively to the ground state, directly or via internal conversion to lower triplet states. Thus, the 3nπ* state provides a path for efficient depopulation of the emissive 1ππ* singlet state and, thus, for quenching of fluorescence. In the hydroxy derivatives 4 and 5, such low

• pyrene 1ππ* state). Thus, intersystem crossing between these two states can be efficient giving rise to also efficient radiationless depopulation of the emissive singlet state relative to aliphatic analogues, in that quenching 3nπ* states are not present. Interactions with oligonucleotides Compounds 2–5

Asymmetric synthesis of propargylamines as amino acid surrogates in peptidomimetics

• Matthias Wünsch,
• David Schröder,
• Tanja Fröhr,
• Lisa Teichmann,
• Sebastian Hedwig,
• Nils Janson,
• Clara Belu,
• Jasmin Simon,
• Shari Heidemeyer,
• Philipp Holtkamp,
• Jens Rudlof,
• Lennard Klemme,
• Alessa Hinzmann,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2017, 13, 2428–2441, doi:10.3762/bjoc.13.240

• sulfinamide (S)-1 into N-sulfinylimine 5w, which was reacted with (trimethylsilyl)ethynyllithium. However, following the usual procedure GP-4 with warming up the reaction mixture to room temperature before quenching with water led to the formation of triazole 13w, which was isolated in 56% yield (Table 4

Synthesis and photophysical properties of novel benzophospholo[3,2-b]indole derivatives

• Mio Matsumura,
• Mizuki Yamada,
• Atsuya Muranaka,
• Misae Kanai,
• Naoki Kakusawa,
• Daisuke Hashizume,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2017, 13, 2304–2309, doi:10.3762/bjoc.13.226

• = 75%) was high, comparable to that of phosphole and indole-fused pentacyclic heteroacene (Ф = 70%) [35]. On the other hand, a low fluorescence intensity was observed for phosphine sulfide 5 and selenide 6 (Ф = 1% and 0.3%, respectively). Quenching of fluorescence emission due to a soft sulfur

A novel application of 2-silylated 1,3-dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes

• Grzegorz Mlostoń,
• Paulina Pipiak,
• Róża Hamera-Fałdyga and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 1900–1906, doi:10.3762/bjoc.13.185

• to yield tetraaryl/hetarylethene 9 and dithioformic acid anion (12). For comparison reasons, two other 2-trimethylsilyl 1,3-dithiolanes 13a,b with no substituents at C4 and C5 were prepared and tested in desilylation reactions performed with TBAF in THF solutions. In both cases, quenching of the

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

A novel approach to oxoisoaporphine alkaloids via regioselective metalation of alkoxy isoquinolines

• Benedikt C. Melzer and
• Franz Bracher

Beilstein J. Org. Chem. 2017, 13, 1564–1571, doi:10.3762/bjoc.13.156

• acylation following Kunitomo’s strategy. Main advantage of this approach should be that the laborious introduction of the carboxy residue at a late stage of the total synthesis is circumvented. Alternatively, quenching of the 1-magnesiated alkoxyisoquinolines with iodine should lead to 1-iodoisoquinolines

• -(isoquinolin-1-yl)benzoates 10 after up to 72 h at room temperature or 60 °C [22]. Starting materials were recovered almost quantitatively. However, quenching with iodine gave the 1-iodoisoquinolines 8a [23], 8b, and 8c in good yields (53–67%, Scheme 2). For the introduction of ring D of the oxoisoaporphine

• ) at C-8 of the isoquinoline ring, which should be followed by an intramolecular trapping of the amide group to give the oxoisoaporphine bianfugecine (6, Scheme 5). However, only starting material 12 was recovered from this reaction. A D2O quenching experiment after the metalation period (4 equiv LDA

Synthesis of oligonucleotides on a soluble support

• Harri Lönnberg

Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134

• precipitate was dissolved in MeCN and conventional aq I2 oxidation was performed. After bisulfite quenching, the mixture was diluted with chloroform and washed with water to remove salts. The organic phase was evaporated to foam and subjected to detritylation with TFA in DCM or MeCN. The detritylated material

A strategic approach to [6,6]-bicyclic lactones: application towards the CD fragment of DHβE

• Tue Heesgaard Jepsen,
• Emil Glibstrup,
• François Crestey,
• Anders A. Jensen and
• Jesper Langgaard Kristensen

Beilstein J. Org. Chem. 2017, 13, 988–994, doi:10.3762/bjoc.13.98

• terminal alkyne with n-BuLi and subsequent quenching with ethyl chloroformate provided the desired ester 3 in 43% yield. The subsequent stereoselective addition of lithium iodide [17] provided the Z-vinyl iodide 4 in 76% yield with no trace of the undesired E-isomer. After extensive screening (see

• attempted functionalization by treatment with n-BuLi and quenching with ethyl chloroformate led to a complex mixture of products; the same trend was also observed when switching to LDA as the base. When LiHMDS was applied in this reaction a double addition of ethyl formate took place giving rise to

• allenamide 14 as the major product [21]. After extensive optimization, the optimal results were obtained by treatment of 13 with 1 equiv of LiHMDS at −78 °C for 2 h before the addition of 5 equiv of ethyl chloroformate. The resulting mixture was then left at –78 °C for 1 h before quenching at low temperature

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

• literature in multistep synthesis, we have classified the literature and have identified the case studies based on few criteria viz. type of reaction, heating methods, processes involving in-line separation units, telescopic synthesis, processes involving in-line quenching and process with the smallest time

• (viz. forcefully quenching the reaction). There should also be a sequence of operation procedures which can take the process from one state of operating conditions to another state of operation. Dynamic simulations can be a useful tool to study the special purpose operations (viz. start-up, shut-down

• ]), and conventional heating in a constant temperature bath/circulator. The cinnarizine/buclizine derivative process was selected as it involved in-line quenching [23]. Most of the above processes involve separation units and hence we decided to select telescopic synthesis of tamoxifen and rufinamide as

Molecular-level architectural design using benzothiadiazole-based polymers for photovoltaic applications

• Vinila N. Viswanathan,
• Arun D. Rao,
• Upendra K. Pandey,
• Arul Varman Kesavan and
• Praveen C. Ramamurthy

Beilstein J. Org. Chem. 2017, 13, 863–873, doi:10.3762/bjoc.13.87

• 1.87 eV, respectively. Again, a lower band gap is observed for P3 owing to the extended conjugation over the other polymers. The combined optical, electrochemical, and theoretical calculations are summarized in Table 2. Photoluminescence (PL) quenching studies were performed with pure donor polymers

• blend ratios, are shown in Figure 5. Polymers P1, P2, and P3 were excited at their absorption maxima of ≈377 nm, 543 nm and ≈395 nm, respectively. It is evident from the spectra that all polymers show significant quenching in their emission, indicating their suitability for OPVs. Next, we fabricated

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• of the substrate coordinating cavity. Recently reported targeted engineering [51] of the Class I taxadiene synthase from Taxus brevifolia (TXS) enabled new understanding of the mechanistic procedures that are carried out by this enzyme on the substrate GGPP. Quenching the carbocation cascade that

Energy down converting organic fluorophore functionalized mesoporous silica hybrids for monolith-coated light emitting diodes

• Markus Börgardts and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 768–778, doi:10.3762/bjoc.13.76

• aggregation induced self-quenching and singlet oxygen dependent dye degradation can be efficiently prevented [14][15]. By the rigid silica host framework bimolecular photochemical reactions are also suppressed [16]. Additionally, mesoporous materials possess the crucial advantage that they can be synthesized

• causes a drop of quantum yields, presumably due to self-quenching effects. Based on the assumption that energy transfer typically occurs at distances of less than 10 nm between two dye molecules, self-quenching should be observed if more than one molecule is found in an area of 10 × 10 nm [29]. If dye

• loadings of the hybrids are correlated with the surface area of the silica material, typically 700 m2·g−1, self-quenching effects should occur at loadings higher than 10 μmol·g−1 as illustrated in Figure 3 [24]. Although aggregation-induced self-quenching can be prevented by covalently ligating dye

Fluorinated cyclohexanes: Synthesis of amine building blocks of the all-cis 2,3,5,6-tetrafluorocyclohexylamine motif

• Tetiana Bykova,
• Nawaf Al-Maharik,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2017, 13, 728–733, doi:10.3762/bjoc.13.72

• reduction on benzoic acid, quenching with methyl iodide, and then subsequent conversion of the cyclohexadiene product to a tetrafluorocycloheane motif [11]. The methyl group was a design feature to block hydrogen fluoride elimination from the position alpha to the aldehyde. The diastereoisomers of all cis

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

• traditionally difficult to detect. The team was able to show significant quenching of the CDs via tryptophan oxidation of the exposed residues on the surface of CDs (Scheme 5). Post-oxidation fluorescence is compromised and therefore can be used as a signal for selectively sensing peroxynitrite up to

• significantly, when compared to other reported heteroatom-doping syntheses, the fluorescence of the B-CDs was dynamically quenched by Fe3+ ions. Mechanistic studies suggested that a dynamic quenching model was prevalent at low concentrations due to interactions between Fe3+ and the CD surface, possibly

• indicating the interception of an excited CD state by the Fe3+ ion that leads to fluorescence quenching. The group exemplified the applicability of the material by demonstrating the ability of the B-CD to sense Fe3+ in tap water samples with a limit of detection of 242 nM, which complies with U.S

Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• dye in the same solvent (ΦΔ = 0.49) [31]. This result excludes any significant intra- or interencapsulation of the excited triplet state of the dye within the β-CD. If this was the case, the reduced quenching by oxygen due to steric hindrance would have resulted in a much smaller value for ΦΔ. The

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• the possibility to generate highly reactive intermediates, such as halomethyllithium carbenoids, that need to be used under internal-quenching technique in batch mode. In 2014, the first example of effective external trapping of a reactive chloromethyllithium (CML) has been reported [28]. α

• chemistry, and has elements of sustainability considering that in batch macroreactors, in order to avoid metal-assisted α-elimination, in situ quenching, an excess of reagents, and very low temperature are required [32][33]. Running the reaction in a flow system at −40 °C, by using residence times between

• 0.18–0.31 s high yields of homologated products have been obtained under external quenching conditions (Scheme 5). The results described above nicely show the potential, as green technology, of flow microreactor systems for synthetic processes involving highly unstable intermediates. Another nice

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• Havis et al. through the dropwise addition of 7 in chloroform to a solution of primary amines such as aminocyclohexane at room temperature [30]. After stirring for 24 hours the resulting diamino hydrobromide was isolated in moderate yield. To avoid quenching/scavenging of the hydrobromide in the later

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• reduction of radical probes (no rearranged products formed from 25d,l,m) and deuterium-labelling experiments (no deuterium incorporation using THF-d8 and quenching with D2O) discard the possibility of a single-electron transfer pathway. Other reductions suggest a hydride addition with formation of an iminyl

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

• Jonas Becher,
• Daria V. Berdnikova,
• Darinka Dzubiel,
• Heiko Ihmels and
• Phil M. Pithan

Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23

• a complex formation, namely a hypochromic effect and red shift of the absorption as well as fluorescence quenching upon addition of the host (Figure 6 and Supporting Information File 1, Figure S3). Furthermore, the significant line broadening of the absorption bands occurs most likely due to

Nucleophilic displacement reactions of 5′-derivatised nucleosides in a vibration ball mill

• Olga Eguaogie,
• Patrick F. Conlon,
• Francesco Ravalico,
• Jamie S. T. Sweet,
• Thomas B. Elder,
• Louis P. Conway,
• Marc E. Lennon,
• David R. W. Hodgson and
• Joseph S. Vyle

Beilstein J. Org. Chem. 2017, 13, 87–92, doi:10.3762/bjoc.13.11

• . Suspending the reaction mixture in methanol and quenching excess selenocyanate with benzyl bromide enabled pure 3a to be isolated following extensive purification. In contrast, LAG of TsT (1c) with DMF for 9 h achieved 90% conversion (by TLC) to a single product. Likewise, efficient (ca. 95%) conversions

• attempted but in all cases the levels of transformation were reduced compared with DMF. Extraction of NCSedT (3b) from the reaction vessels in methanol and quenching excess inorganic selenocyanate with benzyl bromide enabled the product to be purified by silica gel column chromatography. In the absence of

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• the benzyl ester 19 with lithium diisopropylamide and quenching the enolate with carbon dioxide (Scheme 2a). Benzyl 2-tert-butylmalonate (6) was prepared in good yield using a method of Krapcho et al. [18], by double deprotonation of 3,3-dimethylbutyric acid (20) with LDA and quenching the dianion

Formose reaction accelerated in aerosol-OT reverse micelles

• Makoto Masaoka,
• Tomohiro Michitaka and
• Akihito Hashidzume

Beilstein J. Org. Chem. 2016, 12, 2663–2667, doi:10.3762/bjoc.12.262

• the cases of AOT and CTAB, the radius of the water pools (Rw) was evaluated by dynamic light scattering, whereas, in the case of TX, Rw was estimated by the fluorescence quenching technique. As can be seen in Supporting Information File 1, Figure S1, Rw for AOT and CTAB is almost proportional to the

Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid

• Federica Santoro,
• Matteo Mariani,
• Federica Zaccheria,
• Rinaldo Psaro and
• Nicoletta Ravasio

Beilstein J. Org. Chem. 2016, 12, 2627–2635, doi:10.3762/bjoc.12.259

• reaction of 1a and 2a. This is quite different from the case of ZnI2-catalyzed reaction that requires an excess of thiophenol, use of anhydrous CH2Cl2 as solvent, quenching of the catalyst with water, double extraction with dichloromethane, washing with brine, drying over sodium sulfate and evaporation of