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Search for "switch" in Full Text gives 182 result(s) in Beilstein Journal of Organic Chemistry.

A bisazobenzene crosslinker that isomerizes with visible light

  • Subhas Samanta,
  • Harris I. Qureshi and
  • G. Andrew Woolley

Beilstein J. Org. Chem. 2012, 8, 2184–2190, doi:10.3762/bjoc.8.246

Graphical Abstract
  • -lifetimes may be longer when the crosslinker is attached to a biomolecule, it appears the para-piperazine unit may be best suited for applications where rapid thermal relaxation is required. Keywords: azobenzene; molecular switches; switch; photo-control; visible; Introduction Azobenzene derivatives have
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Published 14 Dec 2012

Flow photochemistry: Old light through new windows

  • Jonathan P. Knowles,
  • Luke D. Elliott and
  • Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

Graphical Abstract
  • microreactor, which demonstrated that doubling the residence time allowed the switch from a 300 W Hg lamp to a 15 W black light, i.e., a significant increase in photon efficiency, and resulted in an increased percentage yield (71% versus 56%). The same yields could be achieved by using a 1.7 W UV-LED under
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Published 21 Nov 2012

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

  • Vadim A. Soloshonok,
  • José Luis Aceña,
  • Hisanori Ueki and
  • Jianlin Han

Beilstein J. Org. Chem. 2012, 8, 1920–1928, doi:10.3762/bjoc.8.223

Graphical Abstract
  • *) and (Ra*,Ph*,Rc*) occurs by intramolecular trans-coordination of Ni–NH and Ni–O bonds providing a basis for a chiral switch model. Keywords: axial chirality; central chirality; chiral switches; coordination bonds; functional materials; helical chirality; modular structural design; molecular devices
  • diastereomeric transformations are considered as the most promising models for the development of molecular switches with nondestructive read out of the optical information [14][15][16][17][18]. Taking into account the issue of fatigue resistance or durability of a potential molecular switch, the newly emerging
  • design strategies make use of the formation and cleavage of metal–ligand coordination bonds as a basis for a chiral conformational switch in the conformationally restricted molecular backbone [19][20][21][22][23]. Here, we would like to describe a new design and synthesis of quasi-diastereomeric
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Published 13 Nov 2012

Evaluation of a chiral cubane-based Schiff base ligand in asymmetric catalysis reactions

  • Kyle F. Biegasiewicz,
  • Michelle L. Ingalsbe,
  • Jeffrey D. St. Denis,
  • James L. Gleason,
  • Junming Ho,
  • Michelle L. Coote,
  • G. Paul Savage and
  • Ronny Priefer

Beilstein J. Org. Chem. 2012, 8, 1814–1818, doi:10.3762/bjoc.8.207

Graphical Abstract
  • in obtaining high stereoselectivity, and thus we decided to switch to Michael addition with organomagnesium and organozinc reagents. Since the copper source that produced the highest ee value with the cyclopropanation above was Cu(I) triflate tetrakisacetonitrile, we decided to initially focus on
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Published 22 Oct 2012

A simple and efficient dual optical signaling chemodosimeter for toxic Hg(II)

  • Sabir H. Mashraqui,
  • Sapna A. Tripathi,
  • Sushil S. Ghorpade and
  • Smita R. Britto

Beilstein J. Org. Chem. 2012, 8, 1352–1357, doi:10.3762/bjoc.8.155

Graphical Abstract
  • ratiometric or switch-on responses even for the paramagnetic metal ions [17][18][19]. The first luminescence chemodosimeter for Hg2+ was developed by Czarnik et al. and was based on the Hg2+-mediated desulfurization of anthracene-thioamide chromophore [20][21]. Following this pioneering report, several other
  • responses or cross affinities, especially from Ag+, Pb2+ and Cu2+ [41][42][43][44][45][46][47][48][49][50][51]. Consequently, designing easily accessible Hg2+-selective chemosensors with dual colorimetric and fluorescence switch-on capabilities is deemed of interest in supramolecular research. Acridone, a
  • conclusion, 10-methylthioacridone constitutes one of the simplest and most easily accessible chemodosimeters affording dual colorimetric and fluorescence switch-on responses for the selective and sensitive targeting of toxic Hg2+. Other merits of the chemodosimeter include visible-light excitation and
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Published 22 Aug 2012

Control over molecular motion using the cistrans photoisomerization of the azo group

  • Estíbaliz Merino and
  • María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

Graphical Abstract
  • ]. On the other hand, the isomerization can also occur through a rotation mechanism [11][30], which involves a π→π* transition (S0→S2) (Figure 3). This mechanism is similar to that produced in the isomerization of stilbene [23]. Azobenzenes as molecular switches A molecular switch is a molecular system
  • that allows mechanical movements to be carried out when the system is subjected to an external stimulus, such as light, resulting in conformational and environmental changes of the switch. The basis of a molecular switch is the reversible transformation of chemical species caused by light between two
  • condition for a molecule to behave as a switch is the existence of two different and stable isomeric forms that interconvert when an external stimulus is applied to it. The most important requirements for a molecule to behave as a molecular switch are the following [31][32][33][34][35]: The transformation
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Published 12 Jul 2012

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety

  • Renjie Wang,
  • Shouzhi Pu,
  • Gang Liu and
  • Shiqiang Cui

Beilstein J. Org. Chem. 2012, 8, 1018–1026, doi:10.3762/bjoc.8.114

Graphical Abstract
  • or ortho position of the terminal benzene ring were synthesized. Their photochromism, fluorescent-switch, and electrochemical properties were investigated. Among these diarylethenes, the one with a formyl group at the ortho position of benzene displayed the largest molar absorption coefficients and
  • cytotoxicity [32]. Piao et al. developed a multiresponsive fluorescent molecular switch containing terpyridine. This diarylethene can serve as a detector for metal-ion transmembrane transport [33]. Singer et al. explored a novel diarylethene with a 7-deazaadenosine, which led to new research in photochromic
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Published 05 Jul 2012

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

  • Jaume García-Amorós and
  • Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

Graphical Abstract
  • few decades. The interconversion between the different states of the molecular switch can be performed by a great variety of environmental stimuli, which can be classified into three main groups: light energy, electrical energy and chemical energy (pH, solvent, the presence of a determined metal or
  • the azobenzene core is one of the main factors that allows modulating the thermal relaxation rate of azo-dyes and, therefore, determines the response time of the photochromic molecular switch. The response time of the photochromic switch is a key feature in its overall performance. This parameter is
  • for decreasing the relaxation time of the photochromic switch by placing two hydroxy groups in the same ring of the azobenzene moiety, to obtain an added effect of the two hydroxy groups. The relaxation time of the ortho-para-di-substituted azophenol cis-17 was 12 ms in ethanol and 53 ms in toluene
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Published 04 Jul 2012

Toward unidirectional switches: 2-(2-Hydroxyphenyl)pyridine and 2-(2-methoxyphenyl)pyridine derivatives as pH-triggered pivots

  • Christina Tepper and
  • Gebhard Haberhauer

Beilstein J. Org. Chem. 2012, 8, 977–985, doi:10.3762/bjoc.8.110

Graphical Abstract
  • performed, the M isomer of 13 is more stable than the P isomer by 4.4 kJ·mol−1. This means that in equilibrium the ratio between the diastereomers amounts to 85:15 in favor of the M isomer. In the case of a protonation of the pyridine switch 13 the rotation during the switching process will be in sum
  • unidirectional (in our case counterclockwise). In the case of the methoxyphenylpyridine switch 10 the difference between the M and the P isomer was calculated with B3LYP/6-31G* to be 2.1 kJ·mol−1 in favor of the M isomer. According to this calculation the ratio between the diastereomers amounts to 70:30
  • unidirectionally. Another result is found for the switch 10: If we compare the simulated spectra of (M)-10 and (P)-10, using time-dependent density functional theory (TD-DFT-B3LYP/6-31G*; Figure 7b) with the measured spectrum of 10 in DCM (Figure 7a), it becomes evident that the M isomer is the prevailing one. The
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Published 29 Jun 2012

On the bromination of the dihydroazulene/vinylheptafulvene photo-/thermoswitch

  • Virginia Mazzanti,
  • Martina Cacciarini,
  • Søren L. Broman,
  • Christian R. Parker,
  • Magnus Schau-Magnussen,
  • Andrew D. Bond and
  • Mogens B. Nielsen

Beilstein J. Org. Chem. 2012, 8, 958–966, doi:10.3762/bjoc.8.108

Graphical Abstract
  • , renders the system interesting as a light-controlled molecular switch in, for example, molecular electronics. Indeed, light-induced conductance switching was recently observed for a DHA derivative situated in a single-molecule junction [4]. For the further exploration of the DHA/VHF switch in this field
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Published 27 Jun 2012

Algicidal lactones from the marine Roseobacter clade bacterium Ruegeria pomeroyi

  • Ramona Riclea,
  • Julia Gleitzmann,
  • Hilke Bruns,
  • Corina Junker,
  • Barbara Schulz and
  • Jeroen S. Dickschat

Beilstein J. Org. Chem. 2012, 8, 941–950, doi:10.3762/bjoc.8.106

Graphical Abstract
  • switch in P. gallaeciensis from exhibiting mutualistic to pathogenic properties mediated by the algicidal roseobacticides, which are only produced upon induction by 5 [21][22]. Roseobacticide A (4) was suggested to arise from tropone (3), p-hydroxyphenylacetic acid, which is potentially formed from 5
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Published 25 Jun 2012

Parallel and four-step synthesis of natural-product-inspired scaffolds through modular assembly and divergent cyclization

  • Hiroki Oguri,
  • Haruki Mizoguchi,
  • Hideaki Oikawa,
  • Aki Ishiyama,
  • Masato Iwatsuki,
  • Kazuhiko Otoguro and
  • Satoshi Ōmura

Beilstein J. Org. Chem. 2012, 8, 930–940, doi:10.3762/bjoc.8.105

Graphical Abstract
  • precursors, 51 and 52, using amines 49 and 50, with different methylene lengths and attempts to switch reaction sites. Four-step synthesis of hexacyclic scaffold 63 employing manifold 15. For details of the synthesis of 60 and 61 see Supporting Information File 1. In vitro anti-trypanosomal activities of
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Published 22 Jun 2012

Diarylethene-modified nucleotides for switching optical properties in DNA

  • Sebastian Barrois and
  • Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2012, 8, 905–914, doi:10.3762/bjoc.8.103

Graphical Abstract
  • photoswitchable components in nucleic acids and are suitable for the control of a variety of different biological functions. The photoinduced cis–trans isomerization of azobenzene nucleosides can reversibly switch between the formation and dissociation of DNA duplexes [14][15][16][17], photoregulate DNA
  • only is a structural change observed but a large change in polarity is yielded additionally [10][22]. It is expected that the ring-closed spiropyran form of this molecular switch does not insert into the base stack due to its twisted structure, but the open merocyanine form could intercalate based on
  • its planarity and polarity. This assumption was experimentally verified by synthetic spiropyrans as noncovalent DNA and RNA binders [23][24][25]. As expected, ground-state interactions between the noncovalently bound molecular switch and the DNA bases were detected in the case of the merocyanine form
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Published 20 Jun 2012

Building photoswitchable 3,4'-AMPB peptides: Probing chemical ligation methods with reducible azobenzene thioesters

  • Gehad Zeyat and
  • Karola Rück-Braun

Beilstein J. Org. Chem. 2012, 8, 890–896, doi:10.3762/bjoc.8.101

Graphical Abstract
  • -terminus, which follows behind the azo-switch, and the side chains that are critical for PDZ recognition (as exemplified in Scheme 1 for the 4,4'-substituted azobenzene system). However, the design presented herein, in combination with an appropriate ligation method, seems also to be applicable to the
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Published 18 Jun 2012

The importance of the rotor in hydrazone-based molecular switches

  • Xin Su,
  • Timo Lessing and
  • Ivan Aprahamian

Beilstein J. Org. Chem. 2012, 8, 872–876, doi:10.3762/bjoc.8.98

Graphical Abstract
  • of a series of hydrazone-based systems having different functional groups as part of the rotor (R = COMe, CN, Me, H), was studied. The switching efficiency of these systems was compared to that of a hydrazone-based molecular switch (R = COOEt) whose E/Z isomerization is fully reversible. It was found
  • their configuration (i.e., E/Z isomerization) as a function of pH [22][23][24], or upon the addition of a Lewis acid (i.e., Zn2+) [25]. The simplest hydrazone switch (PPH-1, Scheme 1) for example, exists mainly as its E isomer (PPH-1-E) in solution, as illustrated by the E/Z isomer ratio of 93:7 in
  • than PPH-5, suggesting that PPH-1 is a more ideal system to be used as a molecular switch. This analysis is clearly in line with the acid switching experiments that show that PPH-1 can be fully switched, whereas PPH-5 cannot. Conclusion In summary, we have synthesized four hydrazone-based systems
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Published 13 Jun 2012

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

  • Marcin Jasiński,
  • Dieter Lentz and
  • Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

Graphical Abstract
  • well with high certainty. The stereochemical outcome observed for the reactions studied also deserves some comment. Whereas lithiated methoxy- and TMS-ethoxyallene yielded the diastereomers in ca. 2:1 ratio, in the case of lithiated benzyloxyallene a significant switch of the selectivity to an
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Published 30 Apr 2012

Laterally substituted symmetric and nonsymmetric salicylideneimine-based bent-core mesogens

  • Sonja Findeisen-Tandel,
  • Wolfgang Weissflog,
  • Ute Baumeister,
  • Gerhard Pelzl,
  • H. N. Shreenivasa Murthy and
  • Channabasaveshwar V. Yelamaggad

Beilstein J. Org. Chem. 2012, 8, 129–154, doi:10.3762/bjoc.8.15

Graphical Abstract
  • ). In the case of a ferroelectric response, the compound would switch between the states (Figure 12a and Figure 12c), and after the field is switched off one of these textures would be remain. By extensive electro-optical studies employing lower frequencies and a modified triangular wave voltage, the
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Published 24 Jan 2012

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

  • Paul Knochel,
  • Matthias A. Schade,
  • Sebastian Bernhardt,
  • Georg Manolikakes,
  • Albrecht Metzger,
  • Fabian M. Piller,
  • Christoph J. Rohbogner and
  • Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

Graphical Abstract
  • exchange with the very electron-poor tribromoquinoline 73, it was necessary to reduce the reactivity of the exchange reagent and thus, to switch from iPrMgCl·LiCl (64) to the less reactive mesitylmagnesium reagent MesMgCl·LiCl (71). This reagent is readily prepared by the reaction of mesityl bromide with
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Published 13 Sep 2011

Microphotochemistry: 4,4'-Dimethoxybenzophenone mediated photodecarboxylation reactions involving phthalimides

  • Oksana Shvydkiv,
  • Kieran Nolan and
  • Michael Oelgemöller

Beilstein J. Org. Chem. 2011, 7, 1055–1063, doi:10.3762/bjoc.7.121

Graphical Abstract
  • molecules with a “flick of a switch” [1][2][3][4]. Light is furthermore considered a clean “reagent” and consequently, photochemistry has contributed extensively to the growing field of Green Chemistry [5][6][7]. It is therefore surprising that synthetic organic photochemistry has been widely neglected by
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Published 02 Aug 2011

Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

  • Estela Álvarez,
  • Delia Miguel,
  • Patricia García-García,
  • Manuel A. Fernández-Rodríguez,
  • Félix Rodríguez and
  • Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89

Graphical Abstract
  • responsible for the selectivity switch in favor of the Nazarov product. Nevertheless, the beneficial effect of the bulky phosphite ligand is also significant factor with regards to both reactivity and selectivity. To examine further the scope of this switch of selectivity in favor of the Nazarov pathway in
  • , temperature), in the gold(I)-catalyzed tandem reactions of 3-propargylindoles initiated by 1,2-indole migrations. We have been able to switch the preference of 3-propargylindoles, bearing (hetero)aromatic substituents at both propargylic and terminal positions of the alkyne moiety, from undergoing an aura-iso
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Published 09 Jun 2011

When cyclopropenes meet gold catalysts

  • Frédéric Miege,
  • Christophe Meyer and
  • Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

Graphical Abstract
  • ethers 11a and 11’a was obtained under the previously used reaction conditions. By lowering the temperature to 10 °C and increasing the quantity of n-BuOH (15 equiv), the tertiary allylic ether 11a (65%) was obtained regioselectively (11a/11’a > 99:1). Curiously, a complete switch of the regioselectivity
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Published 30 May 2011

Kinetic evaluation of the solvolysis of isobutyl chloro- and chlorothioformate esters

  • Malcolm J. D’Souza,
  • Matthew J. McAneny,
  • Dennis N. Kevill,
  • Jin Burm Kyong and
  • Song Hee Choi

Beilstein J. Org. Chem. 2011, 7, 543–552, doi:10.3762/bjoc.7.62

Graphical Abstract
  • are replaced by the more polarizable sulfur as in phenyl chlorodithioformate (PhSCSCl, 4) [17][40][45], the mechanism of reaction was found to completely switch over to an ionization (SN1) pathway (Scheme 2) in all of the pure and binary aqueous organic mixtures studied. This tendency to follow an
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Published 29 Apr 2011

Olefin metathesis in nano-sized systems

  • Didier Astruc,
  • Abdou K. Diallo,
  • Sylvain Gatard,
  • Liyuan Liang,
  • Cátia Ornelas,
  • Victor Martinez,
  • Denise Méry and
  • Jaime Ruiz

Beilstein J. Org. Chem. 2011, 7, 94–103, doi:10.3762/bjoc.7.13

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  • -cored stars. Multiple carbon–carbon bond formation upon RCM and CM, and the complete switch of selectivity in the presence of acrylic acid. Example of chemo-, regio- and stereoselective CM of polyolefin dendrimers catalyzed by the 2nd generation Grubbs metathesis catalyst to produce water-soluble
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Published 19 Jan 2011

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

  • Yannick Borguet,
  • Xavier Sauvage,
  • Guillermo Zaragoza,
  • Albert Demonceau and
  • Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

Graphical Abstract
  • mixture revealed the presence of at least five different ruthenium–phosphine species in solution. Unless all these species are able to promote the ATRC reaction, the catalytic switch required to complete the tandem process should therefore be far less efficient with monometallic benzylidene complex 3 than
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Published 08 Dec 2010

Gelation or molecular recognition; is the bis-(α,β-dihydroxy ester)s motif an omnigelator?

  • Peter C. Griffiths,
  • David W. Knight,
  • Ian R. Morgan,
  • Amy Ford,
  • James Brown,
  • Ben Davies,
  • Richard K. Heenan,
  • Stephen M. King,
  • Robert M. Dalgliesh,
  • John Tomkinson,
  • Stuart Prescott,
  • Ralf Schweins and
  • Alison Paul

Beilstein J. Org. Chem. 2010, 6, 1079–1088, doi:10.3762/bjoc.6.123

Graphical Abstract
  • , characteristic of a well-defined aggregate) at higher Q in conjunction with local maxima or oscillations usually at higher Q arising from Bragg reflections or sharp interfaces, or a switch from a Q−1 to a Q−2 dependencies on a double logarithmic I(Q) versus Q plot [13][41][42][43][44][45][46][47][48][49]. With
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Published 18 Nov 2010
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