Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile

• Carsten S. Kramer and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 1414–1418, doi:10.3762/bjoc.9.158

• , the high exo-selectivity for the Diels–Alder reaction can be explained. In the disfavored transition state II the bulky OTBS-group conflicts with the catalyst–substrate complex. Many organocatalytic reactions are known for their long reaction times because of the relatively weak interactions between

Direct alkenylation of indolin-2-ones by 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles: a novel approach

• Sandeep Kumar,
• Ramendra Pratap,
• Abhinav Kumar,
• Brijesh Kumar,
• Vishnu K. Tandon and
• Vishnu Ji Ram

Beilstein J. Org. Chem. 2013, 9, 809–817, doi:10.3762/bjoc.9.92

• interaction energy in the crystal structures of 8yc by means of the dimer unit bound by C–H…π, C–H…O and Ar–H…π interactions at the DFT level of theory yields interaction energies of 22.33, 14.92 and 15.45 kJ·mol−1, respectively. To confirm further the presence of these weak interactions, bond critical points

A peptidic hydrogel that may behave as a “Trojan Horse”

• Nicola Castellucci,
• Giorgio Sartor,
• Natalia Calonghi,
• Carola Parolin,
• Giuseppe Falini and
• Claudia Tomasini

Beilstein J. Org. Chem. 2013, 9, 417–424, doi:10.3762/bjoc.9.44

• been reported [11]. In the gels, noncovalent, weak interactions between the individual LMWHG molecules hold the fibers together. The gel-forming characteristics of LMWHGs can be controlled by altering the strength of these interactions, as illustrated by the thermal reversibility of the gel–sol

The β-cyclodextrin/benzene complex and its hydrogen bonds – a theoretical study using molecular dynamics, quantum mechanics and COSMO-RS

• Jutta Erika Helga Köhler and
• Nicole Grczelschak-Mick

Beilstein J. Org. Chem. 2013, 9, 118–134, doi:10.3762/bjoc.9.15

• the equation ΔG = −RT ln Ks they obtained the corresponding three free energy values ΔG of −11.5 kJ mol−1, −11.0 kJ mol−1 and −10.6 kJ mol−1, indicating rather weak interactions between the guest and host molecule, but still a thermodynamically exothermic reaction of complex formation. Here, our best

Synthesis of multivalent host and guest molecules for the construction of multithreaded diamide pseudorotaxanes

• Nora L. Löw,
• Egor V. Dzyuba,
• Boris Brusilowskij,
• Lena Kaufmann,
• Elisa Franzmann,
• Wolfgang Maison,
• Emily Brandt,
• Daniel Aicher,
• Arno Wiehe and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2012, 8, 234–245, doi:10.3762/bjoc.8.24

• macrocyclization. The use of weak interactions, e.g., metal complexation [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47], charge-transfer interactions [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63], or hydrogen bonding [64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79

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

• ···F fragment present in such a molecular system [5][6]. Although not completely understood, nonbonding F···O interactions, as well as many other unusual long-range interactions involving halogen atoms, are found in several molecular systems in the literature [7][8][9]. Such weak interactions are more

(How) does 1,3,5-triethylbenzene scaffolding work? Analyzing the abilities of 1,3,5-triethylbenzene- and 1,3,5-trimethylbenzene-based scaffolds to preorganize the binding elements of supramolecular hosts and to improve binding of targets

• Xing Wang and
• Fraser Hof

Beilstein J. Org. Chem. 2012, 8, 1–10, doi:10.3762/bjoc.8.1

• methyl groups, but the size of this advantage can be small and is dependent on the groups involved. Keywords: binding affinity; entropy; molecular recognition; scaffolds; supramolecular hosts; triethylbenzene; trimethylbenzene; Introduction Supramolecular hosts use arrays of multiple weak interactions

• to achieve strong and specific binding to targeted guest molecules. Many important weak interactions are directional and lead to highly ordered host–guest complexes [1][2]. The preorganization of binding elements in a competent binding geometry can have enthalpic effects on binding when considering

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• geminal protons G. The singlet at 6.57 ppm is assigned to proton A. The chemical shift of proton A is the same as in structure 11. The other two signals at 3.97 ppm and 4.70 ppm appear as singlets, and they are assigned to protons C and B, respectively, based on weak interactions in the COSY and NOESY

NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

• Damjan Makuc,
• Jennifer R. Hiscock,
• Mark E. Light,
• Philip A. Gale and
• Janez Plavec

Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140

• anion–receptor interaction were found to be H1, H6 and H7α. Only minor ΔδH7α and negligible differences of δH1 and δH6 were observed in the presence of chloride anions (Figure 2a and Figure 2b). The very weak interactions between chloride and 1 could be due to competing interactions of the polar DMSO

• observed for 2 upon interaction with chloride anions (Figure 7a), which suggests a very weak interaction between chloride and 2, similar to the weak interactions observed between chloride and 1. Chemical shift changes showed that the main interaction between receptor 2 and trigonal planar anions (acetate

• anions to 3 induced negligible chemical shifts, suggesting only weak interactions with this anion (Figure 7b). The strong deshielding of H7α and moderate deshielding of H1 protons in the 3·AcO− and 3·BzO− complexes suggests a significant interaction between the anions and the ureido functionality

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

• engineering; halogen bonding; hydrogen bonding; supramolecular chemistry; weak interactions; Introduction Non-covalent interaction, such as hydrogen bonding and metal coordination represent the basic set of tools for the construction of elaborate architectures in the supramolecular chemistry of organic or

Thematic series on supramolecular chemistry

• Christoph A. Schalley

Beilstein J. Org. Chem. 2009, 5, No. 76, doi:10.3762/bjoc.5.76

• interactions was of great interest. The first synthetic host-guest complexes were studied with respect to their components’ ability to bind selectively to each other through weak interactions. Mostly cations were used as the guests, because they provided rather strong binding interactions due to their charge

Themed series in organo- fluorine chemistry

• David O'Hagan

Beilstein J. Org. Chem. 2008, 4, No. 11, doi:10.3762/bjoc.4.11

• organo-fluorine research [7]. Investigations into the stereoelectronic influence of fluorine and the nature of weak interactions between fluorine and other substituents remains an active area of research and for example important insights into how fluorinated drugs interact with proteins are emerging as

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

• products from these reactions are characterized by different spectroscopic techniques and also by X-ray crystallography. The crystal structures of 3 and 4 are shown in Figure 2. In solid state the weak interactions among the molecules lead to formation of self-assemblies of 3 and 4. Among the weak

• identification of a suitable system for obtaining homogeneous solutions with primary amines. The solid state structure of (a) 1 and (b) 2 (drawn with 20% thermal ellipsoids). (a) The crystal structure of 3 and (b) weak interactions in 3 leading to self-assembly, (c) Structure of 4 (drawn with 20% thermal

• interactions N-H. . . O, C-H. . . O and C-H. . . π interactions play roles in the self-assembly formation as illustrated in Figure 2. Some of the important weak bonds responsible for hydrogen bonding assemblies in 3 C6-H. . . O1 (3.303Å, 153.07°), C11-H. . . O1 (3.540Å, 143.41°), N2-H. . . O2 (2.877Å, 140.18