A self-assembled photoresponsive gel consisting of chiral nanofibers

• Lei Zou,
• Dan Han,
• Zhiyi Yuan,
• Dongdong Chang and
• Xiang Ma

Beilstein J. Org. Chem. 2018, 14, 1994–2001, doi:10.3762/bjoc.14.174

• glutamic acid skeleton, containing azobenzene as a photoresponsive group and ureidopyrimidinone (UPy) as a connection site, was designed and synthesized. The monomer is capable of forming an organogel in nonpolar organic solvents and different types of nanostructures in other solvents. The state of the gel

• and co-workers [20][21][22][23][24][25][26][27][28][29][30][31] have built a multifunctional controllable gel system, which utilized L-glutamic lipid to construct nanofibers, nanotwists, and nanotubes with the property of chirality. Azobenzene, which is structurally photosensitive, is widely chosen to

• construct optically controlled systems [17][30][32][33][34][35]. This moiety is also frequently employed as a building block because of its strong π–π stacking in nonpolar solvents. Herein, a novel compound 3 containing both chiral L-glutamic lipid and azobenzene was designed and synthesized (Scheme 1). It

An amphiphilic pseudo[1]catenane: neutral guest-induced clouding point change

• Tomoki Ogoshi,
• Tomohiro Akutsu and
• Tada-aki Yamagishi

Beilstein J. Org. Chem. 2018, 14, 1937–1943, doi:10.3762/bjoc.14.167

• complex system between amphiphilic pillar[6]arene 2 and a photoresponsive cationic azobenzene guest [6]. However, neutral guest molecules could not induce a clear LCST change because encapsulation of the neutral guest in the hydrophobic pillar[n]arene core did not significantly change the hydrophobic

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

• Background: 4-(n-Octyloxy)aniline is a known component in the elaboration of organic materials with mesogenic properties such as N-substituted Schiff bases, perylene bisimide assemblies with a number of 2-amino-4,6-bis[4-(n-octyloxy)phenylamino]-s-triazines, amphiphilic azobenzene-containing linear-dendritic

• block copolymers and G-0 monomeric or dimeric dendritic liquid crystals with photochromic azobenzene mesogens. The present ab initio study explores a previously unknown use of 4-(n-octyloxy)aniline in the synthesis, structure and supramolecular behaviour of new dendritic melamines. Results: Starting

• (ethynyl)-s-triazine and various icosanyloxyphenylazides) with liquid crystalline and luminescent properties [22]. On the other hand, mesogenic supramolecular perylene bisimide assemblies with a number of 2-amino-4,6-bis[(4-alkoxy)phenylamino]-s-triazines [23], amphiphilic azobenzene-containing linear

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• photoswitchable azobenzene α-D-mannoside 47 (Scheme 9) [46]. Notably, in this reaction, traces of an anomeric mixture of the respective furanoside 48 were detected. The Mitsunobu synthesis of aryl glycosides was also applied to p-nitrophenol [47], naphthols [48][49], or multifunctional phenols [27][50]. Such

• ]. Synthesis of phenyl glycosides 44 and 45 from unprotected sugars [24]. Synthesis of azobenzene mannosides 47 and 48 without protecting group chemistry [46]. Synthesis of various aryl sialosides using Mitsunobu glycosylation [25]. Mitsunobu synthesis of different jadomycins [54][55]. BOM: benzyloxymethyl

London dispersion as important factor for the stabilization of (Z)-azobenzenes in the presence of hydrogen bonding

• Andreas H. Heindl,
• Raffael C. Wende and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 1238–1243, doi:10.3762/bjoc.14.106

• dispersion forces to be a significant factor, even in the presence of hydrogen bonds. Keywords: azobenzene; hydrogen bonding; London dispersion; molecular switches; Introduction The photo-controlled E→Z isomerization of azobenzene has been known for decades [1] and has originated a wide field of

• [12] and show reversible isomerization from the thermally stable E- to the Z-isomer upon irradiation with UV light. The metastable Z-azobenzene re-isomerizes to the E-conformer either thermally or upon irradiation with visible light [13][14]. Interestingly, the thermal stability of azobenzene isomers

• can be reversed by the incorporation of azobenzene units in macrocyclic arrangements [15]. For example, the groups of Tamaoki [16] and Herges [17] reported azobenzophanes that isomerize thermally to their energetically lower Z-conformations from their corresponding higher energy E-isomers. Moreover

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• (Scheme 5) [42]. In the absence of light, azobenzene derivatives were isolated as the pure E-isomers. In their original report, Sharpless and co-workers described the use of copper turnings to promote a regioselective azide–alkyne [3 + 2]-cycloaddition ("click") reaction over 24 hours [43]. High-speed

• copper salts was found. In an attempt to expedite the LAG reaction, millimol-scale reactions between the p-azobenzene-appended alkyne and 5′-azido-5′-deoxythymidine were attempted in a more capacious copper vessel with a 15 mm diameter zirconia ball (Figure 3). Clean and complete click reactions were

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• active zwitterionic species via an o-QM intermediate. Dimmock et al. subsequently examined the cytotoxic activity of phenolic azobenzene Mannich bases [92]. Correlations were found between structures and activities against murine P388DI and L1210 cells, human T-lymphocyte cell lines and, in some cases

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• mechanosynthesis of organometallic complexes are shown. Ćurić and co-workers reported the first mechanochemical activation of a C–H bond of unsymmetrical azobenzene with Pd(OAc)2 [178]. The cyclopalladation process was highly regioselective and the rate of palladation was also faster than traditional solution

• phase processes. 4'-(N,N-dimethylamino)-4-nitroazobenzene with an equimolar amount of Pd(OAc)2 and 25 μL of glacial acetic acid (for LAG) resulted in regioselective C–H activation to give cyclopalladated complex E in 4.5 h where two Pd- and two azobenzene groups were involved. Treating this complex with

• ]. b) Multistep and multicomponent synthesis of Re-complexes [176]. c) Mechano-synthesis of NHC-Au complex [177]. Mechanochemical activation of C–H bond of unsymmetrical azobenzene [178]. Mechanochemical synthesis of organometallic pincer complex [179]. Mechanochemical synthesis of tris(allyl)aluminum

Syntheses of 3,4- and 1,4-dihydroquinazolines from 2-aminobenzylamine

• Jimena E. Díaz,
• Silvia Ranieri,
• Nadia Gruber and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2017, 13, 1470–1477, doi:10.3762/bjoc.13.145

• , the selective acylation of the aliphatic amino group was achieved by the treatment of the diamine with benzoic acid in the presence of Zr(azobenzene-4,4´-dicarboxylate) [43], with tert-butylperoxybenzoate [44] and with isopropenyl acetate [45], or by a DCC-mediated coupling with a carboxylic acid [38

Determination of the absolute stereostructure of a cyclic azobenzene from the crystal structure of the precursor containing a heavy element

• Reji Thomas and
• Nobuyuki Tamaoki

Beilstein J. Org. Chem. 2016, 12, 2211–2215, doi:10.3762/bjoc.12.212

• substitution (S-(−)-(E)-1). A reductive debromination of S-(−)-(E)-1 results in formation of one of the enantiomers of (E)-2. Using a combination of HPLC and CD spectroscopy we could safely assign the stereostructure of one of the enantiomers of (E)-2, the reduced product R-(−)-(E)-1. Keywords: azobenzene

• alternative method for the determination of the absolute stereostructure of a molecule without the possibility of functionalization. Recently our group reported the synthesis of several cyclic azobenzene molecules and their properties [45][46][47][48][49][50]. All these molecules share a comparable cyclic

• structure, with a photoisomerizable azobenzene unit linked to a substituted or unsubstituted aromatic unit such as naphthalene or benzene. Generally the molecules are of three categories (i) achiral (irrespective of the isomerized state of the azobenzene, i.e., E or Z), (ii) chiral in E-state and achiral in

Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

• Jie Wang,
• Zhiqiang Qiu,
• Yiming Wang,
• Li Li,
• Xuhong Guo,
• Duc-Truc Pham,
• Stephen F. Lincoln and
• Robert K. Prud’homme

Beilstein J. Org. Chem. 2016, 12, 50–72, doi:10.3762/bjoc.12.7

• photo-responsive small molecules are azobenzene and its derivatives which isomerize from trans to cis and from cis to trans under irradiation with UV and visible light, respectively, and are potentially components of photo-responsive materials. In 2005, Harada et al. constructed a photo-responsive

• of α-CD the dodecyl substituents are complexed and the hydrogel is disrupted to give a free-flowing solution. The addition of trans-4,4’-azobenzene carboxylate to this solution results in the preferential formation of the α-CD·trans-4,4’-azobenzene carboxylate host–guest complex and the PAAddn

• hydrogel reforms. Irradiation at 335 nm causes trans-4,4’-azobenzene carboxylate to photo-isomerize to the cis isomer which is too sterically hindered to form a stable α-CD complex, and the dodecyl substituents of PAAddn are once again complexed by α-CD and the hydrogel disaggregates. This last step is

Azobenzene-based inhibitors of human carbonic anhydrase II

• Leander Simon Runtsch,
• David Michael Barber,
• Peter Mayer,
• Michael Groll,
• Dirk Trauner and
• Johannes Broichhagen

Beilstein J. Org. Chem. 2015, 11, 1129–1135, doi:10.3762/bjoc.11.127

• interested in the exploration of azobenzene-containing sulfonamides to block the catalytic activity of human carbonic anhydrase II (hCAII). Herein, we report the synthesis and in vitro evaluation of a small library of nine photochromic sulfonamides towards hCAII. All molecules are azobenzene-4-sulfonamides

• kinetics. Keywords: azobenzene chemistry; enzyme inhibitors; human carbonic anhydrase II; sulfonamide; X-ray crystallography; Introduction Carbonic anhydrase (CA) is an ubiquitously found zinc-containing metalloenzyme with many isoforms, which all catalyze the conversion of carbon dioxide and water to

• (Figure 1b) [5]. Furthermore, sulfonamide-containing azobenzenes exhibit affinity and blocking ability for hCAII (Figure 1c) [6]. With our knowledge in azobenzene chemistry and photopharmacology, we aimed to further understand how electronic substitution patterns on azobenzenes correlate to changes in

Synthesis of photoresponsive cholesterol-based azobenzene organogels: dependence on different spacer lengths

• Yuchun Ren,
• Bin Wang and
• Xiuqing Zhang

Beilstein J. Org. Chem. 2015, 11, 1089–1095, doi:10.3762/bjoc.11.122

• Yuchun Ren Bin Wang Xiuqing Zhang Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province of China, China West Normal University, Nanchong 637009, China 10.3762/bjoc.11.122 Abstract A series of azobenzene–cholesterol organogel compounds (M0–M12) with different spacers were

• the aggregates change from flower-like, network and rod with different sizes. By using IR and XRD characterization, it is found that intermolecular H-bonding, the solvents and van der Waals interaction are the main contributions to the specific superstructure. Keywords: azobenzene; cholesterol

• can bring about new predictable gelation abilities for the construction of novel cholesterol-based gelators. Azobenzene is one of the smartest molecules among all known photochromic compounds because of its E/Z isomerization [18]. Based on this, photomechanical soft materials containing azobenzene

Synthesis of multivalent carbohydrate mimetics with aminopolyol end groups and their evaluation as L-selectin inhibitors

• Joana Salta,
• Jens Dernedde and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2015, 11, 638–646, doi:10.3762/bjoc.11.72

• desired protected divalent compound 10 in excellent yield. Using the aliphatic sebacoyl dichloride (8) as linker (Table 1, entry 2), the expected product 11 could be isolated in 58% yield. The interesting trans-azobenzene derivative 9 [30] was also employed as precursor and the divalent compound 12 was

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• [25][26][27][28][29][30][31][32]. 1.1 Reactions involving C(sp2)–H bonds of aromatic C-reagents In one of the first publications on the preparative introduction of the –OR group into CH-reagents containing directing groups, 8-methylquinoline, 2-arylpyridines, N-phenylpyrazole, azobenzene, and

• salt 109 combined with triethylamine acted as the catalyst, and azobenzene 110 served as the oxidizing agent. Esters 111 were prepared in 16–97% yield. The selective oxidative coupling of aldehydes 112 and alcohols 113 in the presence of amines 114 using 1,4-dimethyltriazolium iodide (115), DBU and

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

• Université Paris 06, CNRS, UMR 8232, IPCM, Chimie des Polymères, F-75005, Paris, France CNRS, UMR 8232, IPCM, Chimie des Polymères, F-75005, Paris, France 10.3762/bjoc.10.304 Abstract This paper reports an efficient preparation of bridged bis-β-CD AZO-CDim 1 bearing azobenzene as a linker and exhibiting

• cavities of cis-AZO-CDim 1 are complexed simultaneously by two adamantyl units of the guest forming a 1:1 complex while trans-AZO-CDim 1 seems to lead to the formation of supramolecular polymers with an n:n stoichiometry. Keywords: azobenzene; cyclodextrins; inclusion complex; photoisomerization

• cis (Z) and trans (E) isomers, which can be interconverted by both photochemical and thermal means [21]. This transformation by external stimuli induces a molecular movement and a significant geometric change [22][23]. CDs and azobenzene derivatives can form inclusion complexes controlled by

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

• building blocks. The obtained glycoligands are monodisperse and present azobenzene moieties as well as sugar ligands at defined positions within the oligomeric backbone and side chains, respectively. We show that the combination of molecular precision together with the photoswitchable properties of the

• azobenzene unit allows for the photosensitive control of glycoligand binding to protein receptors. These stimuli-sensitive glycoligands promote the understanding of multivalent binding and will be further developed as novel biosensors. Keywords: azobenzene; glycopolymer; lectin binding; multivalency

• potential perspectives for the sensing and adhesion of bacteriological targets on various substrates. The examples reported so far make use of azobenzene [16], a well-known photochromic compound offering robustness and straightforward preparation. It is able to reversibly isomerize between an extended and

4-Pyridylnitrene and 2-pyrazinylcarbene

• Curt Wentrup,
• Ales Reisinger and
• David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 754–760, doi:10.3762/bjoc.9.85

• phenylnitrene (1) and 2-pyridylcarbene (3) has been described in considerable detail [1][2][3]. The three species 1–3 have all been observed directly by IR or ESR spectroscopy in low-temperature matrices. The normal reaction products of phenylnitrene are azobenzene (4) and aniline (5), but under forcing flash

• described below. Since nitrenes are intrinsically more stable than the isomeric carbenes [3][12][13], a rearrangement of 21 to 19 is perfectly reasonable. In the case of phenylazide, mild FVT results in the formation of azobenzene (4) (Scheme 1), but violent FVT, where the pressure is allowed to rise to ca

NHC-catalysed highly selective aerobic oxidation of nonactivated aldehydes

• Lennart Möhlmann,
• Stefan Ludwig and
• Siegfried Blechert

Beilstein J. Org. Chem. 2013, 9, 602–607, doi:10.3762/bjoc.9.65

• azobenzene [8][9][10][11][12][13][14][15][16][17][18] were described. The use of mpg-C3N4 should lead to a new process containing two subsequent organocatalytic reactions (Scheme 1). Results and Discussion In initial experiments we used 4-nitrobenzaldehyde as a model substrate. As NHC-salt we selected A

Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

• Alexej Bubnov,
• Miroslav Kašpar,
• Věra Hamplová,
• Ute Dawin and
• Frank Giesselmann

Beilstein J. Org. Chem. 2013, 9, 425–436, doi:10.3762/bjoc.9.45

• -alkoxyphenyl β-D-glucopyranosides [5]. LC compounds in which a hydrophilic polyethyleneimine chain with hydroxy side-groups is attached to the azobenzene mesogenic core through the alkylene chain have showed a thermotropic SmA phase, lyotropic lamellar phase, and a lyotropic analogue of the tilted smectic C

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

• control of carbohydrate-specific bacterial adhesion, it has become our goal to synthesise azobenzene mannosides as photoswitchable inhibitors of type 1 fimbriae-mediated adhesion of E. coli. An azobenzene mannobioside 2 was prepared and its photochromic properties were investigated. The E→Z isomerisation

• that of the standard inhibitor methyl mannoside. These findings could be rationalised on the basis of computer-aided docking studies. The properties of the new azobenzene mannobioside have qualified this glycoside to be eventually employed on solid support, in order to fabricate photoswitchable

• adhesive surfaces. Keywords: azobenzene glycosides; bacterial adhesion; E/Z photoisomerisation; FimH antagonists; mannobiosides; molecular switches; sweet switches; Introduction Adhesion of bacteria to surfaces can be a severe problem both in vivo and in vitro. Hence, inhibition of bacterial adhesion by

A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups

• Kalpana Upadhyaya,
• Venkatesh Gude,
• Golam Mohiuddin and
• Rao V. S. Nandiraju

Beilstein J. Org. Chem. 2013, 9, 26–35, doi:10.3762/bjoc.9.4

• azobenzene or salicylideneimine or phenylbenzoate unit in one of the arms of the bent molecule by a polar cyanobiphenyl moiety lends stiffness to the molecule with a strong dipole moment in the lateral direction. The realization of such a molecular architecture leads to a reduction in rotational disorder as

Amino-substituted diazocines as pincer-type photochromic switches

• Hanno Sell,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2013, 9, 1–7, doi:10.3762/bjoc.9.1

• the thermodynamically more stable cis isomer the lone pairs of the amino nitrogen atoms point towards each other, and in the trans form they point in opposite directions. The distance between the amino nitrogen atoms changes between 8 Å (cis) and 11 Å (trans isomer). Keywords: azobenzene; diazocine

• as directed motion at the molecular level [2][3], the geometry change and the force induced during cis–trans isomerization has to be coupled to the environment. In the macroscopic world, therefore, machines are made from stiff materials. Azobenzene, however, is a rather floppy molecule. Both phenyl

• conformational motion. The first and probably most simple measure to make azobenzene stiffer would be to prevent the phenyl groups from rotating. Connecting both rings with each other via an alkane bridge is probably the most straightforward way to achieve that. Such a molecule, 5,6-dihydrodibenzo[c,g][1,2

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

• Subhas Samanta Harris I. Qureshi G. Andrew Woolley Department of Chemistry, University of Toronto, 80 St. George St., Toronto, ON, M5S 3H6, Canada; telephone: (416) 978-0675, fax: (416) 978-8775 10.3762/bjoc.8.246 Abstract Background: Large conformational and functional changes of azobenzene

• -modified biomolecules require longer azobenzene derivatives that undergo large end-to-end distance changes upon photoisomerization. In addition, isomerization that occurs with visible rather than UV irradiation is preferred for biological applications. Results: We report the synthesis and characterization

• of a new crosslinker in which a central piperazine unit links two azobenzene chromophores. Molecular modeling indicates that this crosslinker can undergo a large change in end-to-end distance upon trans,trans to cis,cis isomerization. Photochemical characterization indicates that it does isomerize

Cyclodextrin-induced host–guest effects of classically prepared poly(NIPAM) bearing azo-dye end groups

• Gero Maatz,
• Arkadius Maciollek and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 1929–1935, doi:10.3762/bjoc.8.224

• ]. Several reports are available on the preparation and properties of thermally responsive polyacrylamides containing azobenzene or stilbene dyes in the side chain [3][14]. Furthermore, the interaction of dye-containing polymers with CD in water is of some interest, because of their external, light-induced