Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• polyfunctionalized spirocyclopenteneoxindoles in good yields (63–85%) and with excellent enantioselectivities (91–99% ee). In contrast, the ee was fairly low (46%) when using a methyl-substituted MHB carbonate at the allylic site. It was rationalized that the aromatic π–π interactions between the catalyst and the

Expeditive synthesis of trithiotriazine-cored glycoclusters and inhibition of Pseudomonas aeruginosa biofilm formation

• Meriem Smadhi,
• Sophie de Bentzmann,
• Anne Imberty,
• Marc Gingras,
• Raoudha Abderrahim and
• Peter G. Goekjian

Beilstein J. Org. Chem. 2014, 10, 1981–1990, doi:10.3762/bjoc.10.206

• modifying π–π-interactions and by favoring hydrogen-bonding to water. These compounds also lack the hydrophobic peripheral benzene units of the previous glycoasterisk ligands. They were replaced with a methylene-triazole linker in order to increase water solubility and to modulate the degree of flexibility

Supercritical carbon dioxide: a solvent like no other

• Jocelyn Peach and
• Julian Eastoe

Beilstein J. Org. Chem. 2014, 10, 1878–1895, doi:10.3762/bjoc.10.196

• intermolecular π–π interactions. Highly ordered macroscale structures were formed through surfactant self-assembly with the addition of the hydrotropic salt benzylamine hydrochloride (BnNH2∙HCl) to a sodium sulfonate surfactant (sodium dodecylbenzene sulfonate, SDBS) [109]. With hydrotrope addition, self

• dimensional fibre growth is attributed to directional forces arising from π–π interactions between the phenyl groups present in both the surfactant and the hydrotrope. Conclusions – viscosity enhancers in dense CO2 There is a range of approaches to help develop viscosity in scCO2, most of which surround the

• phenomena [32][41]. The addition of low molecular weight polymers has shown some promise, with viscosity increases being observed in polymer containing CO2 in comparison to pure CO2, which are attributed to strong intermolecular forces arising from π–π interactions of phenyl groups in the polymeric

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

• stability, processability, and semiconductor device performance. Intermolecular π–π-interactions between chromophores can be dramatically improved upon functionalization at the 6- and 13-positions of pentacene, as demonstrated by the two-dimensional (2D) bricklayer-packing motif for TIPSPc [13][14]. A

Columnar/herringbone dual crystal packing of pyrenylsumanene and its photophysical properties

• Binod Babu Shrestha,
• Shuhei Higashibayashi and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2014, 10, 841–847, doi:10.3762/bjoc.10.80

• molecules are stacked in a convex-to-concave fashion, since this particular pattern results in more highly favored intermolecular π–π interactions [1][2][3][4][5][6][7][8][9][10][11][12][13]. The columnar packing structures of buckybowls typically occur in two forms which are differentiated by the stacking

• –π interaction is 3.0 Å which is sufficiently close to form an excimer (Figure 2f). The angle of the pyrene moieties resulting from the CH–π interaction is approximately 40° (Figure 2f), which enables the partial π–π interactions. Judging from the crystal features of 1, the red-shifted emission of 1

• columnar structure of buckybowl crystals resulting from convex–concave intermolecular π–π interactions is expected to be quite predictable and to serve as a directing force to provide specific crystal structures [16][17]. The present study demonstrates the promising possibility of utilizing the sumanene

Triphenylene discotic liquid crystal trimers synthesized by Co₂(CO)₈-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition

• Bin Han,
• Ping Hu,
• Bi-Qin Wang,
• Carl Redshaw and
• Ke-Qing Zhao

Beilstein J. Org. Chem. 2013, 9, 2852–2861, doi:10.3762/bjoc.9.321

• 3.57Å than that of 5b and 5c, due to the stronger π–π interactions between the triphenylene discogens with mono-ester group. The columnar parameter values of the trimers decreased with the spacer length shortened. So we deduced that the benzene cores were among the alkyl chains in the columnar stacking

Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring

• Marta Pérez-Torralba,
• Rosa M. Claramunt,
• M. Ángeles García,
• Concepción López,
• M. Carmen Torralba,
• M. Rosario Torres,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2013, 9, 2156–2167, doi:10.3762/bjoc.9.253

• % probability) of 1, showing the X-ray labeling of the asymmetric unit. View of the zigzag chain formed in 1, showing the H-bond and F–F interactions. ORTEP plot (20% probability) of 2, showing the X-ray labeling of the asymmetric unit. Packing of 2 showing the F–F contacts along the chain (orange) and the π–π

• interactions that form the double chain (violet). The different tautomers in the 1H and 1-methyl series. 2-Methoxy-4-methyl-3H-1,5-benzodiazepine (7). 1H–19F coupling constant values either through-bond or through-space. The optimized geometry of the TS of 2a inversion. Equations used to transform absolute

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

• the CRD of the lectin, as expected, and furthermore, that in both cases the azobenzene moiety exerts effective interactions with the tyrosine gate involving both benzene rings. Regardless of whether the (E)- or the (Z)-form of 2 is complexed with FimH, favourable π–π interactions can be formed between

Synthesis of 5-(ethylsulfonyl)-2-methoxyaniline: An important pharmacological fragment of VEGFR2 and other inhibitors

• Miroslav Murár,
• Gabriela Addová and
• Andrej Boháč

Beilstein J. Org. Chem. 2013, 9, 173–179, doi:10.3762/bjoc.9.20

• ; S, 14.77%. The AAZ ligand conformer from PDB complex 1Y6A and its VEGFR2 intermolecular interaction map depicting three hydrogen bonds and two stacked (π,π) interactions. No lipophilic interactions are shown here. The part of the skeleton AAZ in bold represents the fragment originating from the

Organocatalytic asymmetric addition of malonates to unsaturated 1,4-diketones

• Sergei Žari,
• Tiiu Kailas,
• Marina Kudrjashova,
• Mario Öeren,
• Ivar Järving,
• Toomas Tamm,
• Margus Lopp and
• Tõnis Kanger

Beilstein J. Org. Chem. 2012, 8, 1452–1457, doi:10.3762/bjoc.8.165

• -containing esters could be the aromatic nature of the squaramide functional group in catalyst IX, allowing additional π–π-interactions. The properties of the enone double bond of the substrate depend on the nature of the substituents in the phenyl ring. Therefore, the electronic effect of the para

Self-assembly of Ru₄ and Ru₈ assemblies by coordination using organometallic Ru(II)₂ precursors: Synthesis, characterization and properties

• Sankarasekaran Shanmugaraju,
• Dipak Samanta and
• Partha Sarathi Mukherjee

Beilstein J. Org. Chem. 2012, 8, 313–322, doi:10.3762/bjoc.8.34

• , respectively. The four donor sites of L are coordinated to four different Ru(II) metal centers and thereby it adopts a tetranuclear rectangular geometry. The solid-state packing of macrocycle 2a along the crystallographic c-axis results in a highly porous structure with square-type channels due to the π–π

• interactions between the adjacent macrocycles (Figure S8, Supporting Information File 1). Triflate (O3SCF3−) counter anions are located outside of the porous channel (Figure S8, Supporting Information File 1). Synthesis and characterization of the octanuclear cage The construction of an octanuclear macrocyclic

Anion–π interactions influence pK_a values

• Christopher J. Cadman and
• Anna K. Croft

Beilstein J. Org. Chem. 2011, 7, 320–328, doi:10.3762/bjoc.7.42

• biological, medical and environmental chemistry [1]. Cation–π and π–π interactions are perhaps the best known of these non-covalent forces and are driven by attractions between the quadrupole moments of the aromatic species in question, with either a cation or other aromatic, respectively. In a similar

• model systems 1–5, based on 1,8-disubstituted naphthalene (Figure 1). Such model systems have already been utilised to great effect by Cozzi and co-workers to probe π–π interactions [25][26]. Related models have also proven effective in exploring neighbouring group interactions in reactive systems, such

Protonation and deprotonation induced organo/hydrogelation: Bile acid derived gelators containing a basic side chain

• Uday Maitra and
• Arkajyoti Chakrabarty

Beilstein J. Org. Chem. 2011, 7, 304–309, doi:10.3762/bjoc.7.40

• -assembled structures form mainly due to weak non-covalent interactions such as hydrogen-bonding, van der Waals forces, π–π interactions, charge-transfer interactions etc. in organogels, whereas, in aqueous gels, the major driving force for aggregation is hydrophobic interaction [2]. A number of

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• gelators for water or aqueous ethanol mixtures. The monoesters presumably form an extended hydrogen bonding array between the ring oxygen and the free hydroxy groups [36]. For these compounds, the main forces that influence gelation include phenyl ring π–π interactions, hydrogen bonding, and hydrophobic

An easy assembled fluorescent sensor for dicarboxylates and acidic amino acids

• Xiao-bo Zhou,
• Yuk-Wang Yip,
• Wing-Hong Chan and
• Albert W. M. Lee

Beilstein J. Org. Chem. 2011, 7, 75–81, doi:10.3762/bjoc.7.11

• accommodate dicarboxylates of different chain lengths. The 3–4 fold stronger binding interaction between sensor 1 and isophthalate in comparison with those of other dicarboxylates may be the result of the good host–guest shape-complementary relationship and the π–π interactions between the aromatic moieties

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

• , solvophobic effects and π–π interactions [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Our previous work has focused on the thermoreversible gelation of partially fluorinated liquids by a homologous series of chiral, non-racemic bis-(α,β-dihydroxy ester)s

Redox-active tetrathiafulvalene and dithiolene compounds derived from allylic 1,4-diol rearrangement products of disubstituted 1,3-dithiole derivatives

• Filipe Vilela,
• Peter J. Skabara,
• Christopher R. Mason,
• Thomas D. J. Westgate,
• Asun Luquin,
• Simon J. Coles and
• Michael B. Hursthouse

Beilstein J. Org. Chem. 2010, 6, 1002–1014, doi:10.3762/bjoc.6.113

• restricted to dimers. Secondly, the six-membered ring comprising–C1–C2–C3–C4–C5–C6– and the adjacent thiophene (–S3–C7–C8–C4–C3–) form π–π interactions with a neighbouring molecule, such that the overlap between the corresponding molecules is restricted to one minor portion of the molecule. The centroid

• –centroid distance between the benzene and thiophene rings is 3.74 Å and this interaction is also constrained to dimers. Although in Figure 5 the cations have been omitted for clarity, the diagram shows where the tetrabutylammonium molecules reside to block further close π–π interactions. These interactions

Pyridinium based amphiphilic hydrogelators as potential antibacterial agents

• Sayanti Brahmachari,
• Sisir Debnath,
• Sounak Dutta and
• Prasanta Kumar Das

Beilstein J. Org. Chem. 2010, 6, 859–868, doi:10.3762/bjoc.6.101

• amphiphile 2 began to self-assemble towards hydrogelation above 0.035%, w/v. Moreover, the red shifted emission peak up to MGC and above indicates that the intermolecular π–π interactions between the pyridine moieties plays an important role in gelation [28]. Consequently, the fluorescence quenching of

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• . Strong hydrogen bonding between the lactam units favors the chromophores forming physically cross-linked chain structures in the solid state, which is the origin for the poor solubility [7][8]. Short distances between the chromophore planes (0.336 nm) and phenyl ring planes (0.354 nm) enable π-π

• -interactions via molecular orbital overlapping and excition coupling effects [7][8][9], whilst electronic interactions and strong intermolecular forces lead to a high thermal stability of up to 500 °C. For chemical incorporation into conjugated polymers, the solubility of the DPP compound needs to be increased

Synthesis, electronic properties and self-assembly on Au{111} of thiolated (oligo)phenothiazines

• Adam W. Franz,
• Svetlana Stoycheva,
• Michael Himmelhaus and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2010, 6, No. 72, doi:10.3762/bjoc.6.72

• reversible formation of stable radical cations [26][27][28][29][30][31], their tunable redox and fluorescence properties [32][33][34], and their tendency to self-assemble on surfaces by π–π interactions [35] make them eligible for use as redox-switchable molecular entities. In addition, the inherent folded

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• . The authors reasoned that steric and π–π-interactions with the crowns phenyl substituents are the decisive factor for the enantioselective recognition. Recently, Turgut et al. reported a comparable series of C2-symmetric chiral aza crown ether macrocycles (29) based on (S)-3-phenyloxy-1,2-propanediol

• guests such as NEA (20a) or phenylglycinol (20c). For tryptophan (81b) the best results were achieved with selection factors of one enantiomer over the other up to 13 fold, corresponding to over 90% ee. This is explained by π–π-interactions. Besides chiral substituents on the crown ether ring, chiral

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• acetonitrile. Structural investigations The structure of compounds 1, 2, 6, and 9 was examined in the solid state and in solution. Figure 1 shows the X-ray crystal structures of 6 and 9. The planar flavin chromophore is turned outward relative to the Kemp’s acid. Intermolecular π-π-interactions between the

Variations in product in reactions of naphthoquinone with primary amines

• Marjit W. Singh,
• Anirban Karmakar,
• Nilotpal Barooah and
• Jubaraj B. Baruah

Beilstein J. Org. Chem. 2007, 3, No. 10, doi:10.1186/1860-5397-3-10

• have anion binding ability on protonation or have complex forming ability with metals. The incorporation of pyridine ring to a quinone has also another facet as we have recently observed that in picolyl derivative of 1,8-naphthalimides the π-π interactions are governed by the position of the nitrogen

Molecular recognition. 1. Crystal structures of hexaazamacrocyclic amines containing p-xylylene spacers and their adducts with acids

• Teresa Borowiak,
• Grzegorz Dutkiewicz,
• Maciej Kubicki,
• Marek Pietraszkiewicz,
• Agnieszka Gil and
• Rainer Mattes

Beilstein J. Org. Chem. 2005, 1, No. 16, doi:10.1186/1860-5397-1-16

• molecular plane. Four of the six methyl groups are directed towards the molecular cavity. They are situated in pairs slightly above and below the cavity due to the crystallographic symmetry. The remaining two methyl groups are exo-oriented along the long molecular axis. No π-π interactions occur in the