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

• cycloisomerization side reaction. Further, the latter species is not able to isomerize the educt or the RCM product. Upon increasing the temperature to 140 °C, the said decomposition reaction is faster leading to the observed switch of reactivity in favor of the cycloisomerization pathway and isomerization of the

• gave mostly RCM and minor amounts of cycloisomerization product, the unmodified congener which preferentially exists in its cis-dichloro isomer, shows a switched reactivity. The reactivity switch is most probably caused by different substrate-induced decomposition reactions being responsible for the

A novel and widespread class of ketosynthase is responsible for the head-to-head condensation of two acyl moieties in bacterial pyrone biosynthesis

• Darko Kresovic,
• Florence Schempp,
• Zakaria Cheikh-Ali and
• Helge B. Bode

Beilstein J. Org. Chem. 2015, 11, 1412–1417, doi:10.3762/bjoc.11.152

• products have been shown to be potent antibiotics targeting the newly identified switch region of the bacterial RNA polymerase [24]. Furthermore the promiscuity of MxnB regarding its substrate specificity has been used in mutasynthesis experiments to produce novel myxopyronin derivatives [25]. Recently the

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

• strain (Figure 5). The maximum velocity in the DFS experiment is very slow on the atomic length scale, thus the remaining complex could also switch to para-configuration. After additional 0.33 nm rupture length for a monovalent interaction, an overall rupture length around 0.94 nm would be gained by the

Impact of multivalent charge presentation on peptide–nanoparticle aggregation

• Daniel Schöne,
• Boris Schade,
• Christoph Böttcher and
• Beate Koksch

Beilstein J. Org. Chem. 2015, 11, 792–803, doi:10.3762/bjoc.11.89

• few nanoparticle systems by means of temperature [19]; most of the assemblies are irreversibly formed [9], or reversibility is only achieved by adding, for example, oxidizing reagents [27]. Continuous switch behaviour between aggregated and non-aggregated nanoparticles is not obtained as the formation

• refolding into α-helical fibers. Thus, the whole reaction is endothermic. Moreover, a pH switch has a dramatic effect on the observed nanoparticle assembly for the peptide–nanoparticle aggregates of R2A2, R2A3, and R2A4. Increasing the pH value to 11 causes a refolding of the peptide fibers into a coiled

• (C) R2A2 in the presence of 0.05 µM Au/MUA nanoparticles at pH 9 visualised by UV light (left) and visible light (right). Cryo TEM images of 100 µM R2A2 and 0.05 µM Au/MUA nanoparticles at pH 9 at a defocus of (A) −1.2 µm, (B) −1.8 µm and (D) after pH switch from 11 to 9 at a defocus of −1.8 µm. (C

Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency

• Anna K. Ciuk and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 668–674, doi:10.3762/bjoc.11.75

• influence their recognition by lectins [7]. Recently, we have introduced a photoswitchable glycoazobenzene-covered surface, in which alteration of ligand orientation allowed to switch cell adhesion without changing the recognition quality or the valency of the ligand itself [6]. It is also well-known that

Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions

• Bichlien H. Nguyen,
• Robert J. Perkins,
• Jake A. Smith and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2015, 11, 280–287, doi:10.3762/bjoc.11.32

• was used as the electrolyte for the oxidation of the sugar derivative (Scheme 2a). The result was a dramatic reduction in the current efficiency of the process. The switch to LiClO4 as the electrolyte led to a more hydrophilic double layer that no longer excluded the sugar-based substrate, leading to

Novel biphenyl-substituted 1,2,4-oxadiazole ferroelectric liquid crystals: synthesis and characterization

• Mahabaleshwara Subrao,
• Dakshina Murthy Potukuchi,
• Girish Sharada Ramachandra,
• Poornima Bhagavath,
• Sangeetha G. Bhat and
• Srinivasulu Maddasani

Beilstein J. Org. Chem. 2015, 11, 233–241, doi:10.3762/bjoc.11.26

• an input triangular ac wave (20 Hz, 10 Vp-p bias field) (Figure 2), the smectic domains are started to switch and the output wave is found to develop a peak. The area under the peak is found to increase with decreasing the temperature. This observation reflects on the temperature-dependent

One-pot functionalisation of N-substituted tetrahydroisoquinolines by photooxidation and tunable organometallic trapping of iminium intermediates

• Joshua P. Barham,
• Matthew P. John and
• John A. Murphy

Beilstein J. Org. Chem. 2014, 10, 2981–2988, doi:10.3762/bjoc.10.316

• volatilities of BrCCl3 and CHCl3 by removing them under vacuum and replacing the solvent. A solvent switch was also reported when photoredox activation of 4a was combined with thiourea-catalysed enantioselective alkylation [37]. The enantioselectivity of the thiourea-catalysed alkylation was optimal in non

• -polar solvents, yet low photocatalyst solubility in these solvents precluded photoactivation of 4a. Thus, a solvent switch was used to capitalise on the beneficial properties of both solvents. At this stage, we employed an MeCN/H2O (4:1) solvent system and Ru(bpy)3Cl2 in photoactivations which

• allylzinc reagents have failed [44]. Gratifyingly, an allylindium reagent [45] appeared inert to pathways available to the allyl Grignard and allylzinc reagent, affording a 92% yield of 6aj. Strikingly, the same reagent was added without a solvent switch and tolerated BrCCl3, CHCl3 and water, affording 6aj

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• affinity, thus the affinity of guanidine derivative 2 (Figure 2) towards AT-rich DNA sequences was significantly stronger compared to ethidium and comparable to that of the known DNA minor groove binder furamidine. The above mentioned guanidine-induced switch of the DNA- and RNA-binding mode [57] inspired

• between various DNA and RNA polynucleotides was attributed to the switch of the binding mode (intercalation into dGdC-DNA and AU-RNA and minor groove binding into dAdT-DNA). A common strategy for the modification of DNA- and RNA-targeting molecules by preparation of homo-dimers was also implemented on the

• , stressing the importance of steric control over selectivity (Scheme 16). The selectivity of 7 was based on the switch of binding mode; the very rigid pocket between two phenanthridinium moieties allows only bis-intercalation into single-stranded polynucleotides and only binding with double-stranded

Synthesis and characterization of a new photoinduced switchable β-cyclodextrin dimer

• Florian Hamon,
• Claire Blaszkiewicz,
• Marie Buchotte,
• Estelle Banaszak-Léonard,
• Hervé Bricout,
• Sébastien Tilloy,
• Eric Monflier,
• Christine Cézard,
• Laurent Bouteiller,
• Christophe Len and
• Florence Djedaini-Pilard

Beilstein J. Org. Chem. 2014, 10, 2874–2885, doi:10.3762/bjoc.10.304

• to the guest molecules [9][10]. These cyclodextrins linked by ester [11], thioether [12][13][14][15][16], urea [17][18][19], or triazole [20] moieties have been previously described. In addition, aromatic azobenzenes are excellent candidates as molecular switch linkers as they have two forms, namely

• shifted slightly to a shorter wavelength and is significantly less intense at 320 nm. Because the n–π* transition is possible in the cis isomer, this band increases in intensity [22][23]. A molecular switch is based on the light-induced, reversible transformation of chemical species between two molecular

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• -methoxynaphthalene (AMN) can be converted to hydroxynaproxen (HN), a precursor of naproxen (Scheme 13) [85][86]. Although yields up to 90% were obtained in a 1 L flow reactor, the switch to a 75 L system was accompanied by leaks and instrument problems resulting in a low yield (58%) and current efficiency (30%) [86

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

• sequence with prevalence of pyrimidine bases, complementary to cystic fibrosis W1282X point mutation were synthesized. These compounds showed sequence-selective switch-on of pyrene excimer emission in the presence of target DNA, due to PNA2DNA triplex formation, with stability depending on the number and

• , but of the entire triplex, leading to high mismatch recognition. This induces the very high selectivity in the switch-on of the excimer fluorescence emission (Figures 2, 3 and 4). All the other tested dispositions are not so effective in terms of stabilization, fluorescence response and selectivity

Multichromophoric sugar for fluorescence photoswitching

• Stéphane Maisonneuve,
• Rémi Métivier,
• Pei Yu,
• Keitaro Nakatani and
• Juan Xie

Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151

• colorless form (state A), the absence of FRET would keep the fluorescence alive, showing that the combination of these two functional molecules leads to a photon-driven fluorescence switch. Previously, we have synthesized a fluorescent-photochromic dyad (1, Figure 2) combining a DCM fluorophore (4

4-Hydroxy-6-alkyl-2-pyrones as nucleophilic coupling partners in Mitsunobu reactions and oxa-Michael additions

• Michael J. Burns,
• Thomas O. Ronson,
• Richard J. K. Taylor and
• Ian J. S. Fairlamb

Beilstein J. Org. Chem. 2014, 10, 1159–1165, doi:10.3762/bjoc.10.116

• . Following reaction optimisation, we applied these conditions to a number of different propiolate esters and alkylated 4-hydroxy-2-pyrones (Table 3). Surprisingly, the tolerance of the reaction to different ester groups proved rather limited. The switch from methyl propiolate to tert-butyl propiolate (6b

Towards allosteric receptors – synthesis of β-cyclodextrin-functionalised 2,2’-bipyridines and their metal complexes

• Christopher Kremer,
• Gregor Schnakenburg and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 814–824, doi:10.3762/bjoc.10.77

• Abstract Herein, we present three new 2,2’-bipyridines that carry two β-cyclodextrin moieties in different substitution patterns. When coordinated by zinc(II) or copper(I) ions (or their complexes), these compounds undergo conformational changes and switch between “open” and “closed” forms and thereby

• out of it [7][8][9][10][11][12][13][14]. 2,2’-Bipyridines have been demonstrated to be excellent artificial allosteric centres due to their well-known ability to switch between syn- and anti-conformations as an answer to an external stimulus [15]. This switching process can be controlled either by

Modulating NHC catalysis with fluorine

• Yannick P. Rey and
• Ryan Gilmour

Beilstein J. Org. Chem. 2013, 9, 2812–2820, doi:10.3762/bjoc.9.316

• . Deletion of these Ph units from the exocyclic group (6) resulted in a switch to the synclinal-exo conformation (ΦNCCF +67.9°), with the monofluoromethyl group occupying a quasi-axial orientation. Interestingly, this synclinal-endo → synclinal-exo switch is also observed in the corresponding pyrrolidino

The regulation and biosynthesis of antimycins

• Ryan F. Seipke and
• Matthew I. Hutchings

Beilstein J. Org. Chem. 2013, 9, 2556–2563, doi:10.3762/bjoc.9.290

• genes in stationary phase also suggests that specific regulatory mechanisms must exist to switch off the expression of all four ant operons. Despite this, the 14 ant gene clusters contain only a single conserved regulatory gene, antA, which encodes an orphan ECF RNA polymerase σ factor named σAntA

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• intermolecular addition of α-amino radicals to Michael acceptors (Scheme 25) [92]. Oxygen was found to act as a chemical switch to two competing reaction pathways from the same starting anilines. Irradiation of a degassed solution of aniline 99, 2-benzylidenemalononitrile 100, 5 mol % Ir(ppy)2(bpy)](PF6) in MeCN

• Michael acceptors. Conjugated addition of α-amino radicals to Michael acceptors assisted by a Brønsted acid. Conjugated addition of α-amino radicals derived from anilines to Michael acceptors. Oxygen switch between two pathways involving α-amino radicals. Interception of α-amino radicals by

Gold(I)-catalysed one-pot synthesis of chromans using allylic alcohols and phenols

• Eloi Coutant,
• Paul C. Young,
• Graeme Barker and
• Ai-Lan Lee

Beilstein J. Org. Chem. 2013, 9, 1797–1806, doi:10.3762/bjoc.9.209

• via an initial SN2 Friedel–Crafts regioselectivity, thus γ,γ-disubstitution on the alkene appears to be responsible for the switch in regioselectivity (Table 3, entry 11). This implies that the initial Friedel–Crafts allylation goes via Markovnikov selectivity. The unsubstituted secondary allylic

Development of an additive-controlled, SmI₂-mediated stereoselective sequence: Telescoped spirocyclisation, lactone reduction and Peterson elimination

• Brice Sautier,
• Karl D. Collins and
• David J. Procter

Beilstein J. Org. Chem. 2013, 9, 1443–1447, doi:10.3762/bjoc.9.163

• to “switch on” individual steps mediated by the electron transfer reagent. The sequence involves the use of two activated SmI2 reagent systems and a silicon stereocontrol element that exerts complete diastereocontrol over the cyclisation and is removed during the final stage of the sequence by

• manuscript, we report studies on SmI2-mediated cyclisation and lactone reduction that culminate in a “telescoped” sequence, i.e., a sequence of steps carried out on a single reaction mixture by the sequential addition of various reagents. In the sequence, additives are used with SmI2 to “switch on

• in the final stage of the sequence. The procedure is scalable and the overall yields of the telescoped sequences compare well to the combined yields of the analogous stepwise processes. The use of additives to “switch on” individual steps in a particular sequence mediated by the same electron

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

• Eietsu Hasegawa,
• Minami Tateyama,
• Ryosuke Nagumo,
• Eiji Tayama and
• Hajime Iwamoto

Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156

• fast oxidation of the more stable isomer 10 by stronger oxidants such as CuCl2 or Cu(OTf)2 occurs to give the stable tertiary carbocation 13, which is then captured by Cl− or MeCN. In order to explore the generality of the proposed counter-anion-dependent reactivity switch in the nature of copper(II

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• digital camera (Figure 20). Varying the flow rate of the acid stream altered the pH of the combined outflow. The bromocresol green indicator underwent a distinctive change from orange to blue when the concentration of ammonia exceeded the concentration of added acid. By monitoring for a switch in the

• inline evaporation apparatus was developed to perform a solvent switch from dichloromethane (DCM) to dimethylformamide (DMF). The reactor output was dripped into a heated vial containing DMF where a flow of nitrogen gas removed the DCM solvent (Figure 23). A pump removed the concentrated solution through

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

• from the precursor, respectively. When we decrease the photon energy to 7.8 eV again and switch on the pyrolysis, (bottom trace in Figure 2) an intense photoionisation signal is observed at the masses m/z = 91 and 92, which is due to the direct photoionisation of tropyl and its 13C isotopologue. We

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

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• differs from many other docked FimH ligands. Here, the higher affinity for the open-gate FimH can be explained by strong π–π stacking of the first aromatic ring of the azobenzene unit with the tyrosine gate. As both isomers of 2 interact equally well with FimH, they can’t be used to switch type 1 fimbriae