Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• ) [50][51]. It yields copolymers of the desired average molecular mass and narrow molecular mass distribution (Ð = Mw/Mn = 1.0–1.19) and enables control over the block sequence and length in the copolymer chains (sequence-controlled multiblock copolymers). However, in practice this method is restricted

• years, the cross metathesis involving double bonds in the polymer backbone was considered as an undesired chain-transfer process that broadens molecular mass distribution, leads to the formation of cyclooligomers and reshuffling of monomer units in the course of the polymer synthesis [77]. The cross

• found that the width distribution of crystalline lamellae in NB–COE copolymers correlates with the average length of the trans-octenylene blocks. Compared with the pure PCOE or its equimolar blend with PNB, the NB–COE copolymers form considerably smaller crystallites (Figure 8) [92]. Conclusion It is

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• positions 4 and 6 of GalNAc units favor the formation of 1,2-cis glycosidic bonds, even in the presence of 2-participating groups [43][44]. Treatment with (HF)n·Py complex in THF followed by standard acetylation provided compound 7. This derivative displayed a suitable protecting group distribution for the

• the glycosylation outcome, we decided to prepare 2,3-di-O-pivaloyl compound 26 with the GlcA protecting group distribution used in this study. For this purpose, donor 3 was glycosylated with 4-methoxyphenol and then treated with hydrazine monohydrate in a pyridine/acetic acid/CH2Cl2 mixture to afford

Adhesion, forces and the stability of interfaces

• Robin Guttmann,
• Johannes Hoja,
• Christoph Lechner,
• Reinhard J. Maurer and
• Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

• ., polyaromatic hydrocarbons) induces a dipole moment; likewise, when a spherical charge distribution is deformed to an ellipsoid, a quadrupole is induced. Discussion of WMI, as found in the chemical literature, often suffers from a profound confusion of tongues due to the preference of a folkloristic [12

• molecules A and B due to both the nuclei and the electrons. The nuclei are assumed to be point charges in space whereas the electrons form a continuous charge distribution. According to classical electrostatics, this gives rise to two basic contributions, called electrostatics and induction, also called

• stronger than long-range forces” [6]. Exchange repulsion Exchange repulsion, or Pauli repulsion, is a consequence of the Pauli exclusion principle, which states that Fermions avoid coming spatially close to each other. Thus, exchange repulsion has an enormous impact on the spatial distribution of electrons

Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning

• Hiroaki Yoshida,
• Ken Kikuta and
• Toshiyuki Kida

Beilstein J. Org. Chem. 2019, 15, 89–95, doi:10.3762/bjoc.15.10

• ). Because the red photoluminescence of C60 is useful for a bioimaging applications [30][31], the electrospun fibers were measured with confocal laser scanning microscopy (CLSM). Interestingly, a uniform red color distribution is observed (Figure S9, in Supporting Information File 1), indicating the presence

New standards for collecting and fitting steady state kinetic data

• Kenneth A. Johnson

Beilstein J. Org. Chem. 2019, 15, 16–29, doi:10.3762/bjoc.15.2

• parameters rather than kcat and Km (Equation 1). To test this assertion, synthetic data were generated by computer simulation with kcat = 50 s−1 and Km = 20 μM. Data were generated at various concentrations of substrate (5, 10, 20, 30, and 40 μM), with a Gaussian distribution of random noise added to the

• favor of fitting to derive kcat/Km directly. However, as a counterpoint, the only “experimental errors” in the data are random since the added noise conforms to a normal distribution, so this may make the fitting to define kcat and Km more accurate than seen in the laboratory. The “experiment” was

• Figure 5A. Spacing points evenly on a double reciprocal plot does not provide the best distribution of data given the importance of accurately defining kcat and kcat/Km. A better alternative is to space points evenly on a logarithmic scale (Figure 5B,C). Here 11 points can be distributed on a log scale

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• distribution with no isomerization was observed without the use of any additive even after 24 h of reaction performed at 50 °C under neat conditions. N-Alkyl substituents possessing functionalities or heteroatoms In 2001, the Fürstner group reported on phosphine-containing ruthenium complexes having

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• having a high molecular weight with a narrow molecular weight distribution. It was proposed that the polymerization is initiated by single-electron reduction of xanthate 4 by the highly reducing photo-excited state of fac-Ir(ppy)3 (6) [46], although the details were not elucidated (Scheme 2) [39][40

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• electronically excited state which significantly changes the distribution of electrons in the molecule. Thus, chemical properties such as reactivity, oxidation potential or reduction potential change drastically. With appropriate donors or acceptors, electron charge transfer is possible via this excited state

• transition metal complexes” [106]. In this mechanism, the catalyst is the most important component: it determines the equilibrium constant between the active and dormant species which is directly linked to the distribution of chain lengths [107]. As photoredox catalysts for ATRP applications, copper(II

Reactions of 3-(p-substituted-phenyl)-5-chloromethyl-1,2,4-oxadiazoles with KCN leading to acetonitriles and alkanes via a non-reductive decyanation pathway

• Akın Sağırlı and
• Yaşar Dürüst

Beilstein J. Org. Chem. 2018, 14, 3011–3017, doi:10.3762/bjoc.14.280

• unexpected product distribution of the reaction prompted us to investigate the reaction of 5-(chloromethyl)-3-(p-substituted-phenyl)-1,2,4-oxadiazoles 1 with KCN. Our initial effort was to investigate the limitation of the reaction. For this, the effect of temperature on this reaction was examined in CH3CN

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• such broad series of cyclic sulfur containing cations Aa,b and Ba–h. Allenes 2i,j did not react with acids at room temperature, however, they react with TfOH at higher temperature (see below). To estimate the charge distribution in species Aa, Ba we carried out DFT calculations (Table 2). The

The influence of the cationic carbenes on the initiation kinetics of ruthenium-based metathesis catalysts; a DFT study

• Magdalena Jawiczuk,
• Angelika Janaszkiewicz and
• Bartosz Trzaskowski

Beilstein J. Org. Chem. 2018, 14, 2872–2880, doi:10.3762/bjoc.14.266

• Hov and 1–3-Hov catalysts. Natural partial charges distribution in carbenes of 1–3-Hov and 1–3-GrI. Supporting Information Supporting Information File 260: Mulliken partial charges, energy values and Cartesian coordinates for all investigated systems. Acknowledgements This work was supported by

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• weight distribution (PDI = 1.05), suggesting the living nature of the ROMP even within the protein scaffold. Neither regioselectivity (cis/trans) nor tacticity were affected [56]. The transmembrane protein FhuA The β-barrel proteins introduced for the construction of artificial metatheases up to this

Enhanced single-isomer separation and pseudoenantiomer resolution of new primary rim heterobifunctionalized α-cyclodextrin derivatives

• Iveta Tichá,
• Gábor Benkovics,
• Milo Malanga and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2018, 14, 2829–2837, doi:10.3762/bjoc.14.261

• work-up, the reaction mixture, consisting of unreacted α-CD, mono-, di- and trisubstituted products, was converted into the corresponding 6A,6X-diazido-α-CDs 4 [29]. The ratio of the regioisomers was assessed as AB/AC/AD = 39:33:29. The distribution of the positional isomers is almost statistical, and

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• [15]. The ee of propylene glycol, which was obtained after hydrolysis of the copolymer obtained with (S)-PO and PA, was found to be 88%, indicating a high level of regioregularity. Molecular weight distributions are relatively narrow, while a bimodal distribution was observed in the SEC traces. The

• spectrometry (MALDI–TOF MS, Figure 2). Several series of signals with a regular interval of 206.1 (repeating unit) were observed in the lower mass range. The m/z value of each signal of the major distribution corresponds with [166.0 (C6F5COO, initiating group) + 206.1n (repeating unit) + 59.1 (CH2CHMeOH

• , terminal group) + 23.0 (Na+ ion)]. Thus, the expected α-C6F5COO,ω-OH-terminated copolymer was obtained as a main product. As a minor distribution, the α-C6F5COO,ω-COOH-terminated copolymer was observed, while the cyclic polyester via intramolecular transesterification was not detected (Supporting

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• , and Irdfppy system was used for radical-mediated isomerization reactions. Visible-light irradiation of diethyl 2-bromomethyl-2-phenylmalonate produced the phenyl-migrated product (Scheme 10) [104]. The product distribution highly depended on the solvents. The yield of phenyl-migrated products relative

Comparative cell biological study of in vitro antitumor and antimetastatic activity on melanoma cells of GnRH-III-containing conjugates modified with short-chain fatty acids

• Eszter Lajkó,
• Sarah Spring,
• Rózsa Hegedüs,
• Beáta Biri-Kovács,
• Sven Ingebrandt,
• Gábor Mező and
• László Kőhidai

Beilstein J. Org. Chem. 2018, 14, 2495–2509, doi:10.3762/bjoc.14.226

• cells (Table 4). Since the conjugates had no or minor apoptotic effect, the cell cycle kinetics of the cells treated with GnRH-III-based conjugates was also investigated to reveal the mechanism of growth inhibition of these conjugates. The distribution of the control and treated cells in the different

• cell cycle phases was analyzed by measurements of relative DNA contents of individual cells by flow cytometry after propidium iodide (Sigma-Aldrich, St. Louis, MO, USA) staining. The effects of conjugates and Dau on cell cycle phase distribution of A2058 cells are shown in Figure 4. The apoptotic

• phase distribution [45][47]. Based on the findings about the different mechanism of [4Lys(Bu)]-GnRH-III(Dau=Aoa) than the other conjugates, it is assumed that its apoptotic effect could attribute to the presence of butyryl side chain, known for its ability to activate apoptosis [20][39]. Cell adhesion

Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

• Piotr Pomarański,
• Piotr Roszkowski,
• Jan K. Maurin,
• Armand Budzianowski and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214

• research groups have shown beneficial impact of the additional palladium chelation on the products distribution [31][32][33][34]. We also observed an additional chelation effect (N-chelation) in the case of 4-amino-3,5-diaryl-2,6-dimethylpyridine derivatives [30]. The above mentioned examples illustrate

• the transition state what causes that isomer (anti)-8 is formed in a smaller amount. The oxygen atom may serve as an extra ligand. Therefore, the coordination by the methoxy group to palladium may cause changes in the geometry of the complex, reflected in the atropisomers distribution. A similar

• the synthesis of 4-amino-3,5-diaryl-2,6-dimethylpyridine derivatives [30]. The use of different cross-coupling conditions did not significantly change the product distribution of the coupling reaction (Table 1). Interestingly, only one mono-substituted derivative 6 was observed in the reaction mixture

Coordination-driven self-assembly of discrete Ru₆–Pt₆ prismatic cages

• Aderonke Ajibola Adeyemo and
• Partha Sarathi Mukherjee

Beilstein J. Org. Chem. 2018, 14, 2242–2249, doi:10.3762/bjoc.14.199

• +, 961.88 [3a]6+; 3b at m/z = 1398.79 [3b(NO3−)2]4+, 1106.64 [3b(NO3−)]5+, 911.87 [3b]6+ and all peaks are well-resolved isotopically and matched with the theoretical isotopic distribution patterns (Figure 3 and Supporting Information File 1, Figure S22). Geometry optimization of the heterometallic cages

• distribution patterns of the charged fragments. Energy-minimized structure of heterometallic trigonal prismatic cage 3a. Hydrogen atoms are omitted for the sake of clarity [Ru: green, Pt: pink, O: red, N: blue, P: orange, C: grey]. Self-assembly of the heterometallic prismatic cages. Synthesis of the platinum

Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• are based on extended Debye–Hückel theory [2] and Poisson–Boltzmann distribution [3] to describe ionic profiles near the glass-electrode surface. These classical models may be good approximations for ions such as Li+ and F−, but they are poor models for ions that don’t behave as hard point charges [4

• of one time using a separate solution of host. Those data were then averaged and presented herein. Results shown are representative of the volume-weighted distribution. Surface plots of the raw, volume-weighted distribution data were plotted using OriginPro software. NMR solution sample preparation

• site of 1 (blue). Representative plots of the volume-weighted distribution obtained by DLS for salts titrated into 2.00 mM 1: a) LiCl, b) LiBr, c) LiI, d) NaF, e) NaCl, f) NaBr, g) NaI, h) KF, i) KCl, j) KBr, k) KI, l) CsF, m) CsCl, n) CsBr, o) CsI. Scale shown in the upper-left corner. The x-axis

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• hydrogen bonding. Detailed electrochemical measurements and digital simulations revealed the ring still to be bound to the ammonium station in the TTF●+ state. However, after double oxidation a wheel distribution of 1:1 between the ammonium and the isoxazole station was found indicating a dynamic motion

Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds – an experimental and theoretical study

• Ana-Maria Preda,
• Małgorzata Krasowska,
• Lydia Wrobel,
• Philipp Kitschke,
• Phil C. Andrews,
• Jonathan G. MacLellan,
• Lutz Mertens,
• Marcus Korb,
• Tobias Rüffer,
• Heinrich Lang,
• Alexander A. Auer and
• Michael Mehring

Beilstein J. Org. Chem. 2018, 14, 2125–2145, doi:10.3762/bjoc.14.187

• distribution of the dispersion interaction within each dimer. An especially high dispersion energy contribution is observed for dimer 1c-2-1 (−83 kJ mol−1). By looking at the distribution of the dispersion energy (dispersion energy density plots) for this dimer it is noticed that almost the entire monomers

Coordination-driven self-assembly vs dynamic covalent chemistry: versatile methods for the synthesis of molecular metallarectangles

• Li-Li Ma,
• Jia-Qin Han,
• Wei-Guo Jia and
• Ying-Feng Han

Beilstein J. Org. Chem. 2018, 14, 2027–2034, doi:10.3762/bjoc.14.178

• 3a. The peak was isotopically resolved and agrees well with the theoretical isotopic distribution. In addition, the IR spectrum of the rhodium metallarectangle 3a showed a C=N stretching band at 1618 cm−1. The same self-assembly protocol can also be used for the synthesis of metallarectangle 3b. The

• . Similar to that observed in complex 3a, a peak at m/z = 450.0868 was observed, which is attributable to [3b − 4OTf]4+, and its isotopic pattern is in good agreement with the theoretical distribution (Figure 3, right). The absorption band at 1620 cm−1 in the IR spectrum indicated the existence of an imine

Host–guest complexes of conformationally flexible C-hexyl-2-bromoresorcinarene and aromatic N-oxides: solid-state, solution and computational studies

• Rakesh Puttreddy,
• Ngong Kodiah Beyeh,
• S. Maryamdokht Taimoory,
• Daniel Meister,
• John F. Trant and
• Kari Rissanen

Beilstein J. Org. Chem. 2018, 14, 1723–1733, doi:10.3762/bjoc.14.146

• ) the positive charge distribution in lower-rim host cavity [+0.06 to −0.06 a.u.]. An expansion of the 1H NMR (6.6 mM at 298 K, 500 MHz) of BrC6 complexes with 3. Spectra are produced from BrC6, 3 and an equimolar mixture of BrC6 and 3 in: (a) (CD3)2O, (b) CD3OD/CDCl3 1:1 v/v, and (c) CD3OD/DMSO-d6 9:1

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• mediated. The size of nanospheres (expressed by their average diameters, D) ranged in a large domain (234–1454 nm) with a quite wide distribution of D values in all situations (Supporting Information File 1, p. S41, Figure S55). With the exception of compound 6, all other G-2 dendrimers were, in fact

A conformationally adaptive macrocycle: conformational complexity and host–guest chemistry of zorb[4]arene

• Liu-Pan Yang,
• Song-Bo Lu,
• Arto Valkonen,
• Fangfang Pan,
• Kari Rissanen and
• Wei Jiang

Beilstein J. Org. Chem. 2018, 14, 1570–1577, doi:10.3762/bjoc.14.134

• the substituents to leverage the primary cation···π interactions and thus the final binding affinities. This may explain the parabolic distribution of binding affinities over the Hammett parameters (σp) of the substituents as shown in Figure 2. The conformational adaptivity or flexibility allows ZB4