Ruthenium indenylidene “1^st generation” olefin metathesis catalysts containing triisopropyl phosphite

• Stefano Guidone,
• Fady Nahra,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2015, 11, 1520–1527, doi:10.3762/bjoc.11.166

• ” cis-complexes. These have been used in olefin metathesis reactions. The cis-Ru species exhibit noticeable differences with the trans-Ru parent complexes in terms of structure, thermal stability and reactivity. Experimental data underline the importance of synergistic effects between phosphites and L

• synergistic effects in the case of the mixed phosphine/phosphite system. Complex 1 is a thermally-switchable, latent pre-catalyst displaying higher thermal stability compared to the phosphine-based Ind-I. Consequently, a brief study of the scope of the reaction was investigated employing “1st generation

• reaction showing similarities with cis-Caz-1 in terms of reactivity. Both pre-catalysts need thermal activation; they display an induction period in the reaction profiling and exhibit higher thermal stability compared to their phosphine-based analogues. In terms of catalytic efficiency, Ind-I was found

Thermal properties of ruthenium alkylidene-polymerized dicyclopentadiene

• Yuval Vidavsky,
• Yotam Navon,
• Yakov Ginzburg,
• Moshe Gottlieb and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2015, 11, 1469–1474, doi:10.3762/bjoc.11.159

• initiators where only cross-linked polymers are obtained. This polyolefinic cross-linked thermoset material exhibits outstanding thermal stability [22], mechanical strength [23], fracture toughness [24] and dielectric characteristics [25]. Thanks to these properties PDCPD has become a very attractive polymer

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• -position changes the thermodynamic equilibrium favoring the trans- over the cis-isomers. In any case, a remarkable thermal stability of all studied compounds was found. Intrigued by the observed phenomenon, we turned to structural studies. Structures of 14 and 15 have been determined using single-crystal X

• thermal stability of the precatalyst becomes irrelevant once it is in the presence of the substrate [33], because it is the thermal stability of the actual active species in the reaction mixture that governs the reaction outcome. In the present case, the methylidene complex formed during metathesis with

• educt as well as that of the product is observed. However, the results for 5a as the precatalyst make clear that the thermal stability of the methylidene is not the only factor governing the outcome of the studied reactions. If the stability of the methylidene were the only crucial factor in all cases

Synthesis and spectroscopic properties of β-triazoloporphyrin–xanthone dyads

• Dileep Kumar Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2015, 11, 1434–1440, doi:10.3762/bjoc.11.155

• porphyrins can be modulated by introducing diverse functionalities on their periphery or changing the metal ions in the porphyrin core [3][4]. Due to the high thermal stability and extended π-electron system, porphyrins are very useful for the construction of molecular switches [5][6] and other organic

Carboxylated dithiafulvenes and tetrathiafulvalene vinylogues: synthesis, electronic properties, and complexation with zinc ions

• Yunfei Wang and
• Yuming Zhao

Beilstein J. Org. Chem. 2015, 11, 957–965, doi:10.3762/bjoc.11.107

• of 9). It is therefore reasonable to propose that the microporosity in 8 is directly related to the coordination polymer structure. Finally, the thermal stability of coordination polymer 8 and Zn-DTF 9 were evaluated by differential scanning calorimetric (DSC) analysis, and detailed DSC traces are

• illustrated in Figure 6. The DSC data of Zn-TTFV 8 (Figure 6A) manifested very good thermal stability up to 400 °C, without any significant melting or decomposition except a slight phase transition at 272 °C. Comparatively, the DSC trace of carboxyl-TTFV ligand 6 showed a distinctive melting process at 317 °C

• considerably improved thermal stability, a property particularly beneficial for practical device and material applications. Conclusion In summary, we have synthesized carboxylated diphenyl-TTFV 6 and phenyl-DTF 7 as redox-active ligands to complex with Zn(II) ions. The electronic and electrochemical properties

Mechanical stability of bivalent transition metal complexes analyzed by single-molecule force spectroscopy

• Manuel Gensler,
• Christian Eidamshaus,
• Maurice Taszarek,
• Hans-Ulrich Reissig and
• Jürgen P. Rabe

Beilstein J. Org. Chem. 2015, 11, 817–827, doi:10.3762/bjoc.11.91

• 10.3762/bjoc.11.91 Abstract Multivalent biomolecular interactions allow for a balanced interplay of mechanical stability and malleability, and nature makes widely use of it. For instance, systems of similar thermal stability may have very different rupture forces. Thus it is of paramount interest to study

• latent catalysts for self-healing, mechanochroism or mechanoluminescence [14]. The thermal stability of a molecular system is inversely proportional to the thermal off-rate. However, this alone gives an incomplete image of bond rupture under physiological conditions. For example, depending on the

• ) model, finally giving the rupture length rb and the thermal off-rate koff (a measure of the inverse thermal stability) [20][21][22]. This method is especially useful in the case of interactions with low affinity of low yield that are inaccessible for ensemble measurements. For example in 2009

DNA display of glycoconjugates to emulate oligomeric interactions of glycans

• Alexandre Novoa and
• Nicolas Winssinger

Beilstein J. Org. Chem. 2015, 11, 707–719, doi:10.3762/bjoc.11.81

• helical structure and thermal stability. Surface plasmon resonance (SPR) affinity measurements with murine C-type lectin receptor (mMGL) showed specific binding only for duplexes containing two or four Lewis-X units. Alternatively, Ebara and co-workers have shown that glycan–DNA conjugates can be accessed

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

• across the single С–N bond (the С2–N1–С3–C4 dihedral angle is 4.3°, Figure 1), unlike its C4-aryl-substituted analogs with the angle of 73–75° [26]. The Е-configuration of the С=N bond, unfavorable for cyclization into 1,4-oxazine, explains the enhanced thermal stability of compound 3e. Heating azadiene

Properties of cationic monosubstituted tetraalkylammonium cyclodextrin derivatives – their stability, complexation ability in solution or when deposited on solid anionic surface

• Martin Popr,
• Sergey K. Filippov,
• Nikolai Matushkin,
• Juraj Dian and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2015, 11, 192–199, doi:10.3762/bjoc.11.20

• , Czech Republic Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16, Prague 2, Czech Republic 10.3762/bjoc.11.20 Abstract The thermal stability of the monosubstituted cationic cyclodextrin (CD) derivatives PEMEDA-β-CD and

• , yet robust and a straightforward process as well. Keywords: cyclodextrins; inclusion properties; solid surface; tetraalkylammonium derivatives; thermal stability; Introduction Cyclodextrins (CDs) are a very interesting group of natural macrocyclic carbohydrates, which were first described by

• transport of aromatic compounds [30]. In this paper we report on a comprehensive study of the properties of the novel monosubstituted cationic CD derivative PEMPDA-β-CD (PErMethylated PropyleneDiAmine substituted). Its thermal stability is compared to the previously reported analogue PEMEDA-β-CD

Enhancing the reactivity of 1,2-diphospholes in cycloaddition reactions

• Almaz Zagidullin,
• Vasili Miluykov,
• Elena Oshchepkova,
• Artem Tufatullin,
• Olga Kataeva and
• Oleg Sinyashin

Beilstein J. Org. Chem. 2015, 11, 169–173, doi:10.3762/bjoc.11.17

• (with thermal stability up to 190 °C) and 2H-phospholes (exhibiting high reactivity in the cycloaddition reaction at 25 °C) [9][10][11]. In the present work, attempts to increase the reactivity of the dienic system of 1,2-diphospholes using two different approaches are described: (a) by the introduction

• reaction mixtures showed many multiplets at 80 and −40 ppm with a coupling constant 1JPP ca. 200–210 Hz characteristic for the products of [4 + 2] cycloaddition reaction – 1,7-diphosphanorbornadienes [9][11]. Remarkably, 1-alkyl-1,2-diphospholes without EWGs reveal significant thermal stability and

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

• solvent could significantly influence the activity and selectivity of the enzymatic reaction as well as increase the thermal stability of enzymes [66]. The high sensitivity of lipases towards the medium environment mainly stems from experimental observations that different organic solvents had a different

A comparative study of the interactions of cationic hetarenes with quadruplex-DNA forming oligonucleotide sequences of the insulin-linked polymorphic region (ILPR)

• Darinka Dzubiel,
• Heiko Ihmels,
• Mohamed M. A. Mahmoud and
• Laura Thomas

Beilstein J. Org. Chem. 2014, 10, 2963–2974, doi:10.3762/bjoc.10.314

• thermal stability of the ILPR-DNA with respect to unfolding was also examined by emission spectroscopy in K+- and Na+-containing buffer, i.e., the melting temperature, Tm, of the dye-labelled quadruplex-forming ILPR sequence Fa2T [fluorescein-d(ACAG4TGTG4ACAG4TGTG4)-tetramethylrhodamine] was determined by

Synthesis and properties of novel star-shaped oligofluorene conjugated systems with BODIPY cores

• Clara Orofino-Pena,
• Diego Cortizo-Lacalle,
• Joseph Cameron,
• Muhammad T. Sajjad,
• Pavlos P. Manousiadis,
• Neil J. Findlay,
• Alexander L. Kanibolotsky,
• Dimali Amarasinghe,
• Peter J. Skabara,
• Tell Tuttle,
• Graham A. Turnbull and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2704–2714, doi:10.3762/bjoc.10.285

• oligofluorene arm length and substitution patterns of the central BODIPY core have been synthesised, leading to two families of compounds, T-B1–T-B4 and Y-B1–Y-B4, with T- and Y-shaped motifs, respectively. Thermal stability, cyclic voltammetry, absorption and photoluminescence spectroscopy of each member of

• molecular bromine which was used previously [33]. Thermal, electrochemical and optical properties TGA and DSC analyses All of the final target compounds showed good thermal stability. Thermogravimetric analysis (TGA) revealed decomposition temperatures in the range 396–442 °C (Table 1, Figure S1, Supporting

Encapsulation of biocides by cyclodextrins: toward synergistic effects against pathogens

• Véronique Nardello-Rataj and
• Loïc Leclercq

Beilstein J. Org. Chem. 2014, 10, 2603–2622, doi:10.3762/bjoc.10.273

• -CD inclusion complexes greatly improves the thermal stability of the biocide with no negative influence on its activity and toxicity. In 2013, Hill et al. reported that β-CD can be used to encapsulate various essential oil constituents (e.g., trans-cinnamaldehyde, eugenol, etc.) for antimicrobial

• their high thermal stability, low toxicity to human cells and effective broad-spectrum antibacterial activity. The antibacterial activity of these nanoparticles is probably due to their rapid breakdown which releases ionic silver that interact with the thiol residues of bacterial enzymes [80]. As a

Synthesis and characterization of a hyper-branched water-soluble β-cyclodextrin polymer

• Francesco Trotta,
• Fabrizio Caldera,
• Roberta Cavalli,
• Andrea Mele,
• Carlo Punta,
• Lucio Melone,
• Franca Castiglione,
• Barbara Rossi,
• Monica Ferro,
• Vincenza Crupi,
• Domenico Majolino,
• Valentina Venuti and
• Dominique Scalarone

Beilstein J. Org. Chem. 2014, 10, 2586–2593, doi:10.3762/bjoc.10.271

• 30000. Thermogravimetric analyses (Figure 3) clearly show that thermal stability increases by selecting molecular weights greater than 10000 Da (red line) and 30000 Da (green line), and these samples are characterized by a remarkable thermal stability. Degradation of such larger fractions starts at

Reversibly locked thionucleobase pairs in DNA to study base flipping enzymes

• Christine Beuck and
• Elmar Weinhold

Beilstein J. Org. Chem. 2014, 10, 2293–2306, doi:10.3762/bjoc.10.239

• absorption band above 300 nm in the UV spectrum (c, solid) compared to the spectrum of 1I6S∙2U4S (dashed). The thermal stability of the cross-linked duplex 1I6S-Et-S4U2 (d, solid) is drastically increased compared to 1I6S∙2U4S (dashed). Characterization of HPLC-purified cross-linked duplex 1G6S-Et-S4U2 (a

• ) by denaturing anion exchange HPLC (b). Alkylation at the sulfur atoms within the thionucleobases is confirmed by the strong reduction of the absorption band above 300 nm in the UV spectrum of 1G6S-Et-S4U2 (c, solid) compared to the spectrum of 1G6S∙2U4S (dashed). The thermal stability of the cross

The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units

• Aurica Farcas,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert,
• Flavian Farcas,
• Iuliana Stoica and
• Anton Airinei

Beilstein J. Org. Chem. 2014, 10, 2145–2156, doi:10.3762/bjoc.10.222

• -dioctylfluorene 3 and compared with those of the corresponding non-rotaxane 4 counterpart. Rotaxane formation results in improvements of the solubility, the thermal stability, and the photophysical properties. Polyrotaxanes 4a and 4b exhibited slightly red-shifted absorption bands with respect to the non-rotaxane

• “insulation” of the individual molecular wires. Moreover, recently reported results have shown improvements of the thermal stability, solubility, luminescence and surface characteristics of polyrotaxanes compared to those of non-rotaxane counterparts [8][13][19][20][21][22][23][24][25]. This approach has also

• polyrotaxanes exhibited a thermal decomposition temperature around 412 °C, whereas the thermal decomposition temperature of reference 4 was around 414 °C at 5% weight loss (Figure 4 and Table 1). It is noteworthy that the polyrotaxane formation increases the thermal stability of the macrocycle molecules

Second generation silver(I)-mediated imidazole base pairs

• Susanne Hensel,
• Nicole Megger,
• Kristina Schweizer and
• Jens Müller

Beilstein J. Org. Chem. 2014, 10, 2139–2144, doi:10.3762/bjoc.10.221

• artificial metal-mediated base pairs. We show here that its stability can be further improved by formally replacing the imidazole moiety by a 2-methylimidazole or 4-methylimidazole moiety. A comparison of the thermal stability of several double helices shows that the addition of one equivalent of Ag(I) leads

• absolute melting temperature. In the presence of one equivalent of Ag(I), the thermal stability of the duplexes increases significantly. Notably, the increase in Tm is larger by about 50% for the methylated imidazole nucleosides compared with the non-methylated one, amounting to about 8.5 °C per silver(I

• )-mediated base pair. The significantly increased thermal stability of the duplexes comprising either 2-methylimidazole or 4-methylimidazole therefore cannot be attributed to the above-mentioned hydrophobic interaction only but must also be a direct effect of the formation of the metal-mediated base pairs

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

• stable complexes are formed with Zn and Ni, showing higher degradation temperatures as compared to pure RF whereas the remaining complexes showed similar or lower thermal stability to that of the pure RF with the Fe-complex found to be most rapidly degraded [161]. The presence of various metal ions

Efficient CO₂ capture by tertiary amine-functionalized ionic liquids through Li⁺-stabilized zwitterionic adduct formation

• Zhen-Zhen Yang and
• Liang-Nian He

Beilstein J. Org. Chem. 2014, 10, 1959–1966, doi:10.3762/bjoc.10.204

• . These efforts include the development of liquid and solid absorbents and membranes [2][3][4][5][6][7]. Ionic liquids (ILs), which have attractive properties such as negligible vapor pressure, a wide liquid temperature ranges, good thermal stability, high ionic conductivity, and versatile solvation

• . The thermal stability of the chelated ILs was strongly increased compared to the corresponding neutral ligands. The decomposition temperature increased by 90 °C and 60 °C for PEG150MeTMG and PEG150MeBu2N, respectively, after coordination with LiNTf2 (Figure 2a). In the 1H NMR spectrum, the proton

• . Indeed, the thermal stability and the CO2 capacity of the neutral ligands (e.g., PEG150MeBu2N) was highly increased after coordination with lithium salts to form chelated ILs (e.g., [PEG150MeBu2NLi][NTf2]). Experimental Materials All reagents used in this work were purchased from Sigma-Aldrich and used

Aryl substitution of pentacenes

• Andreas R. Waterloo,
• Anna-Chiara Sale,
• Dan Lehnherr,
• Frank Hampel and
• Rik R. Tykwinski

Beilstein J. Org. Chem. 2014, 10, 1692–1705, doi:10.3762/bjoc.10.178

• (vide infra). Thermal analysis The thermal stability of selected aryl pentacenes has been explored by traditional melting point analysis (MPA) in open capillary tubes, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) measurements; the results are summarized in Table 2. TGA

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

• groups lead to a significant decrease of solubility, even in hot solvents, limiting the formation of organogels. In order to investigate the crystallization temperature of solvents within the gel and to compare the influence of the 2-hydroxyethoxy side chains on the thermal stability of the gel, two gel

Photoswitchable precision glycooligomers and their lectin binding

• Daniela Ponader,
• Sinaida Igde,
• Marko Wehle,
• Katharina Märker,
• Mark Santer,
• David Bléger and
• Laura Hartmann

Beilstein J. Org. Chem. 2014, 10, 1603–1612, doi:10.3762/bjoc.10.166

• phenylamine one for two reasons: first, its higher nucleophilicity allows for a smoother synthesis and second, the resulting Z-azobenzene exhibits a high thermal stability as compared to the fully conjugated push-pull azobenzene based on the phenylamine fragment. In total, five precision glycooligomers were

• , demonstrating the reversibility of the systems. Finally, the thermal stability of Z-Azo-Gal(1,3)-3 in the buffer solution is quite high. Indeed, after 48 h at 25 °C only 12% of the Z-isomers converted back to the E-isomer (see Supporting Information File 1). The thermal stability of the trivalent Azo-Gal(1,3,5

Influence of perylenediimide–pyrene supramolecular interactions on the stability of DNA-based hybrids: Importance of electrostatic complementarity

• Christian B. Winiger,
• Simon M. Langenegger,
• Oleg Khorev and
• Robert Häner

Beilstein J. Org. Chem. 2014, 10, 1589–1595, doi:10.3762/bjoc.10.164

• pyrene–pyrene interactions, whereas duplex 1*6 has the maximum number pyrene–PDI interactions. Thermal denaturation experiments Thermal denaturation experiments revealed a clear trend in duplex stability (Figure 2). The thermal stability correlates with the number of pyrene–PDI interactions [56] and

Pyrene-modified PNAs: Stacking interactions and selective excimer emission in PNA₂DNA triplexes

• Alex Manicardi,
• Lucia Guidi,
• Alice Ghidini and
• Roberto Corradini

Beilstein J. Org. Chem. 2014, 10, 1495–1503, doi:10.3762/bjoc.10.154

• using standard Fmoc-based manual solid phase protocol. The crude products were purified by RP-HPLC and characterized by HPLC–UV–MS (Supporting Information File 1, Figures S6–S11). Thermal stability of PNA:DNA complexes The introduction of a modification in a PNA stand can lead to different effects

• the presence of DNA was found to be in accordance with the UV melting measurements (Supporting Information File 1, Figure S15). Fluorescence studies Beside the modification of thermal stability and selectivity induced by the incorporation of pyrene moieties described above, we evaluated the

• hybridization, a property which is very important also in the case of more elaborated methods such as gated detection. These characteristics make PNA2 a very good fluorescent probe, with very high single-base selectivity in both thermal stability and excimer formation upon binding to target DNA. Thus, the