Double N-arylation reaction of polyhalogenated 4,4’-bipyridines. Expedious synthesis of functionalized 2,7-diazacarbazoles

• Mohamed Abboud,
• Emmanuel Aubert and
• Victor Mamane

Beilstein J. Org. Chem. 2012, 8, 253–258, doi:10.3762/bjoc.8.26

• ., van der Waals radii taken into account), large enough to accommodate n-hexane and chloroform molecules, which are disordered. Conclusion In summary, we have described an efficient approach for the synthesis of uncommon 2,7-diazacarbazoles from readily available tetrahalogenated 4,4’-bipyridines. By

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• the fullerenes is observed. This arrangement maximizes the number of points of contact within the supramolecular complex, thereby enhancing the van der Waals interactions. In the same paper, the association constants of several oxacalix[3]arenes were calculated by the Rose–Drago method based on

The interplay of configuration and conformation in helical perylenequinones: Insights from chirality induction in liquid crystals and calculations

• Elisa Frezza,
• Silvia Pieraccini,
• Stefania Mazzini,
• Alberta Ferrarini and
• Gian Piero Spada

Beilstein J. Org. Chem. 2012, 8, 155–163, doi:10.3762/bjoc.8.16

• following set of van der Waals radii: rH = 0.1 nm, rO = 0.15 nm and rC = 0.185 nm [42], along with a rolling sphere radius equal to 0.3 nm [40] and a density of vertices equal to 500 nm−2. The chirality parameter of a given compound Q, was calculated as where the sum is over all the conformers and gj, wj

Computational evidence for intramolecular hydrogen bonding and nonbonding X···O interactions in 2'-haloflavonols

• Tânia A. O. Fonseca,
• Matheus P. Freitas,
• Rodrigo A. Cormanich,
• Teodorico C. Ramalho,
• Cláudio F. Tormena and
• Roberto Rittner

Beilstein J. Org. Chem. 2012, 8, 112–117, doi:10.3762/bjoc.8.12

• , except for the (C=)O···H(O) interaction in 2'-fluoroflavonol A, which is slightly covalent and, hence, stronger than the remaining ones. The distances between the atoms involved in long-range interactions depicted in Table 2 are always shorter than the sum of their van der Waals radii (the van der Waals

On the mechanism of action of gated molecular baskets: The synchronicity of the revolving motion of gates and in/out trafficking of guests

• Keith Hermann,
• Stephen Rieth,
• Hashem A. Taha,
• Bao-Yu Wang,
• Christopher M. Hadad and
• Jovica D. Badjić

Beilstein J. Org. Chem. 2012, 8, 90–99, doi:10.3762/bjoc.8.9

• of the guest (ΔG°), and (3) the “slippage” of the guest while exiting the open host (ΔG‡sterics) [8][11][21][35]. The encapsulation kinetics is first-order in guest CH3CCl3 suggesting that this species creates van der Waals strain (friction) during the in/out trafficking, thereby justifying the use

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 of cationic dibenzosemibullvalene-based phase-transfer catalysts by di-π-methane rearrangements of pyrrolinium-annelated dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 119–126, doi:10.3762/bjoc.7.17

• amphiphilic tetraalkylammonium derivative that exhibits three different benzene-containing concave sites to which an organic substrate may associate by attractive van der Waals interactions or π-stacking. Moreover, additional functionalities, e.g., hydroxy or amino groups, may be attached to the benzene rings

Expanding the gelation properties of valine-based 3,5-diaminobenzoate organogelators with N-alkylurea functionalities

• Hak-Fun Chow and
• Chin-Ho Cheng

Beilstein J. Org. Chem. 2010, 6, 1015–1021, doi:10.3762/bjoc.6.114

• , precipitation or crystallization will take place. On the other hand, if the interactions are too weak, dissolution of the organogelator will result. In addition, non-specific interactions such as hydrophobic and van der Waals interactions are difficult to quantify, yet they can play very important roles on a

Differences between β-Ala and Gly-Gly in the design of amino acids-based hydrogels

• Andreea Pasc,
• Firmin Obounou Akong,
• Sedat Cosgun and
• Christine Gérardin

Beilstein J. Org. Chem. 2010, 6, 973–977, doi:10.3762/bjoc.6.109

• as electrostatic, hydrogen bonding, dipole–dipole, π–π stacking and hydrophobic/van der Waals interactions. Since the cross-links between fibres are non-covalent in nature, LMWHs exhibit thermoreversibility, rapid response to external stimuli (i.e., stirring, sonication). Among these LMWHs, amino

• solvents, and a hydrophobic domain for van der Waals or hydrophobic interactions (Figure 1). They are able to entrap a large number of solvent molecules per one gelator molecule. Herein the gelators were designed as AA-His-EO2-Alk, bearing i) an hydrophobic alkyl group, ii) a polar peptide group with

Towards racemizable chiral organogelators

• Jian Bin Lin,
• Debarshi Dasgupta,
• Seda Cantekin and
• Albertus P. H. J. Schenning

Beilstein J. Org. Chem. 2010, 6, 960–965, doi:10.3762/bjoc.6.107

• that these hydrogen-bonded dimers or tetramers subsequently stack via π-π interaction and via van der Waals interactions into bundled fibers. Racemization The racemization of R-3 was investigated by chiral HPLC. After adding 1 equivalent of DBU to a solution of R-3 in octane at room temperature

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

• hydrophobic interactions is mandatory for any gelation process. Non-covalent interactions such as hydrogen bonding, ionic interactions, π–π stacking or van der Waals forces play a pivotal role in self-assembled gelation [12]. Tuning the structure of gelator molecules leads to a better understanding of the

Chiral gels derived from secondary ammonium salts of (1R,3S)-(+)-camphoric acid

• Tapas Kumar Adalder,
• N. N. Adarsh,
• Ravish Sankolli and
• Parthasarathi Dastidar

Beilstein J. Org. Chem. 2010, 6, 848–858, doi:10.3762/bjoc.6.100

• can be of two kinds – chemical or polymeric and physical or supramolecular. While covalent bonds are responsible for the formation of 3-D networks in chemical gels, various non-covalent interactions such as hydrogen bonding, π-π stacking, hydrophobic, van der Waals forces etc. are required to form gel

Organic gelators and hydrogelators

• Jean-Pierre Desvergne

Beilstein J. Org. Chem. 2010, 6, 846–847, doi:10.3762/bjoc.6.99

• liquid) which behaves as a visco-elastic material (soft matter) due to the immobilization of solvent molecules in a three-dimensional network. This network results from the self-assembly of the gelling agent into fibres via non-covalent interactions such as hydrogen bonding, π–π stacking, van der Waals

Chromo- and fluorophoric water-soluble polymers and silica particles by nucleophilic substitution reaction of poly(vinyl amine)

• Katja Hofmann,
• Ingolf Kahle,
• Frank Simon and
• Stefan Spange

Beilstein J. Org. Chem. 2010, 6, No. 79, doi:10.3762/bjoc.6.79

• 1 resulting from intermolecular interactions with the surroundings of the molecules, and which of these are dipole–dipole and/or hydrogen-bond interactions. To separate the effects of non-specific van der Waals interactions including electrostatic effects (dipolarity/polarizability) from specific

Synthesis and crystallographic analysis of meso-2,3-difluoro-1,4-butanediol and meso-1,4-dibenzyloxy-2,3-difluorobutane

• Bruno Linclau,
• Leo Leung,
• Jean Nonnenmacher and
• Graham Tizzard

Beilstein J. Org. Chem. 2010, 6, No. 62, doi:10.3762/bjoc.6.62

• group does adopt a gauche conformation with its adjacent fluoro substituent where the F–C–C–O dihedral angle is 71.5°. Although strong H-bonding interactions are absent within the crystal, each molecule displays eight short contacts less than the sum of the van der Waals radii to its four nearest

Chemical aminoacylation of tRNAs with fluorinated amino acids for in vitro protein mutagenesis

• Shijie Ye,
• Allison Ann Berger,
• Dominique Petzold,
• Oliver Reimann,
• Benjamin Matt and
• Beate Koksch

Beilstein J. Org. Chem. 2010, 6, No. 40, doi:10.3762/bjoc.6.40

• the preparation of caged proteins. Fluorine is the most electronegative element and has a van der Waals radius of 1.47 Å [10]. Thus, substitution of a C–H bond with a C–F bond dramatically changes the electronic properties of the given molecule but exerts only a minor steric effect [11]. Due to the

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 subtle balance of weak supramolecular interactions: The hierarchy of halogen and hydrogen bonds in haloanilinium and halopyridinium salts

• Kari Raatikainen,
• Massimo Cametti and
• Kari Rissanen

Beilstein J. Org. Chem. 2010, 6, No. 4, doi:10.3762/bjoc.6.4

• atoms (C–X where X = F, Cl, Br or I) and nucleophilic atoms (S, O or N, in their various hybridization states). The analysis was based on intermolecular contact distances shorter than 1.26 times the sum of the van der Waals (VDW) radii of the two interacting atoms. The analysis showed that the

Chiral amplification in a cyanobiphenyl nematic liquid crystal doped with helicene-like derivatives

• Alberta Ferrarini,
• Silvia Pieraccini,
• Stefano Masiero and
• Gian Piero Spada

Beilstein J. Org. Chem. 2009, 5, No. 50, doi:10.3762/bjoc.5.50

• rolling a spherical probe on the assembly of van der Waals spheres centred at the nuclear positions and approximated by a set of triangles, obtained with the algorithm developed by Sanner et al. [59]) was computed. The results reported in this work were obtained by setting the orienting strength ξ to

• 0.025 Å−2 and the rolling sphere radius to 3 Å [32]. The van der Waals radii rH = 1 Å, rC = 1.85 Å, rO = 1.5 Å, and rSi = 2.1 Å were used [62]. A density of points equal to 5 Å−2 was assumed for the molecular surface. Schematic structure of a right-handed chiral nematic (cholesteric) phase. Black arrows

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• the van der Waals distance, C31-C48 (ca. 3.40 Å); two other carbons are also very close to each other: C32-C51 (ca. 3.65 Å). These remarkable features suggest preferred sites of reactivity inasmuch as this rigid geometry is not disfavoured in solution. 3 Electronic absorption spectra and

Stereoselective synthesis of (2S,3S,4Z)-4-fluoro- 1,3-dihydroxy- 2-(octadecanoylamino)octadec- 4-ene, [(Z)-4-fluoroceramide], and its phase behavior at the air/water interface

• Gergana S. Nikolova and
• Günter Haufe

Beilstein J. Org. Chem. 2008, 4, No. 12, doi:10.3762/bjoc.4.12

• organized in small domains, known as rafts, stabilized by hydrogen bonds among the polar head groups and van der Waals interactions of the hydrophobic chains. The presence of lipid domains is thought to be involved in receptor-mediated signal transduction. Due to its ability to form large hydrogen bonded