Adhesion, forces and the stability of interfaces

• Robin Guttmann,
• Johannes Hoja,
• Christoph Lechner,
• Reinhard J. Maurer and
• Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

• large variety of WMIs. To some of them, special names are assigned, such as hydrogen bonding or hydrophobic interactions. In chemistry, these WMIs are frequently used as if they were basic interaction types. For a long time, dispersion was largely ignored in chemistry, attractive intermolecular

• their different flavors. Hydrogen bonding is a typical WMI. As such, it is composed of the abovementioned basic interactions, each having its own strength and range. Nevertheless, it is common practice in chemistry to speak about hydrogen bonding as if it was indeed a genuine basic interaction rather

• than a composed interaction. Instead of stressing the different compositions of the basic interactions, chemists speak of strong, moderate or weak hydrogen bonding [3]; sometimes even further divisions are made [4]. Hydrogen bonding was introduced nearly 100 years ago to explain the stabilization of

A simple and effective preparation of quercetin pentamethyl ether from quercetin

• Jin Tatsuzaki,
• Tomohiko Ohwada,
• Yuko Otani,
• Reiko Inagi and
• Tsutomu Ishikawa

Beilstein J. Org. Chem. 2018, 14, 3112–3121, doi:10.3762/bjoc.14.291

• University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0013, Japan 10.3762/bjoc.14.291 Abstract Among the five hydroxy (OH) groups of quercetin (3,5,7,3',4'-pentahydroxyflavone), the OH group at 5 position is the most resistant to methylation due to its strong intramolecular hydrogen bonding with the

• -methylation is difficult because the OH group at 5 position is resistant to alkylation due to its strong intramolecular hydrogen bonding with the carbonyl group at 4 position. Indeed, inconsistent experimental results have been reported in the literature; incomplete methylation occurred in some cases [24][34

• (run 1 in Table 2, see Supporting Information File 1). The tetramethyl ether 4 showed a lower-field-shifted signal at 12.64 ppm in the 1H NMR spectrum (see Supporting Information File 2), due to strong intramolecular hydrogen-bonding of the OH group at 5 position with the carbonyl group at 4 position

1,8-Bis(dimethylamino)naphthyl-2-ketimines: Inside vs outside protonation

• A. S. Antonov,
• A. F. Pozharskii,
• P. M. Tolstoy,
• A. Filarowski and
• O. V. Khoroshilova

Beilstein J. Org. Chem. 2018, 14, 2940–2948, doi:10.3762/bjoc.14.273

• proton sponge moiety to occupy the in,out-conformation [14] with the 1-NMe2 group participating in NHN intramolecular hydrogen bonding with the C=NH2+ group (Scheme 8). Indeed, in the case of 7b’, which contains three OMe groups, we have found direct evidence of this process: the 1-NMe2 group signal

• 10 (Scheme 8, right), which is out-protonated due to steric reasons [15]. In refs. [15][16][17] it was shown that hydrogen bonding to an out-inverted NMe2 group without the proton transfer does not noticeably change the chemical shift of methyl protons. Thus, in the case of 7b’, the chemical shift at

Nucleoside macrocycles formed by intramolecular click reaction: efficient cyclization of pyrimidine nucleosides decorated with 5'-azido residues and 5-octadiynyl side chains

• Jiang Liu,
• Peter Leonard,
• Sebastian L. Müller,
• Constantin Daniliuc and
• Frank Seela

Beilstein J. Org. Chem. 2018, 14, 2404–2410, doi:10.3762/bjoc.14.217

• ellipsoids are drawn at the 50% probability level and H-atoms are shown as small spheres of arbitrary size. Hydrogen bonds are shown as dashed lines. The crystal packing of 8 shows the intramolecular hydrogen-bonding network (projection parallel to the x-axis). N- and S-conformation for cyclonucleoside 8. B

Determining the predominant tautomeric structure of iodine-based group-transfer reagents by ¹⁷O NMR spectroscopy

• Nico Santschi,
• Cody Ross Pitts,
• Benson J. Jelier and
• René Verel

Beilstein J. Org. Chem. 2018, 14, 2289–2294, doi:10.3762/bjoc.14.203

• residual value (Table 1). Conceivably, this may be due to intermolecular hydrogen bonding with the solvent or other alcohol molecules in the concentrated solution. In fact, including a methanol solvent molecule as a hydrogen-bond donor in the DFT calculation will shift the δcalc in the right direction for

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• lasso, a structural motif which was also recently found in nature for peptides with high antibacterial efficacy [71]. In 12, the TTF molecule is not implemented in the thread but in the wheel component. In the neutral state, strong hydrogen bonding between the crown ether wheel and the dialkylammonium

• hydrogen bonding. Detailed electrochemical measurements and digital simulations revealed the ring still to be bound to the ammonium station in the TTF●+ state. However, after double oxidation a wheel distribution of 1:1 between the ammonium and the isoxazole station was found indicating a dynamic motion

• Figure 27b), donor–acceptor interactions and hydrogen bonding generate a neutral TTF dimer that is surrounded by cofacially oriented bipyridinium units [112]. The intertwined structure is locked by formation of platinum(II)–pyridine coordination bonds. Interestingly, the doubly interlocked catenane

A switchable [2]rotaxane with two active alkenyl groups

• Xiu-Li Zheng,
• Rong-Rong Tao,
• Rui-Rui Gu,
• Wen-Zhi Wang and
• Da-Hui Qu

Beilstein J. Org. Chem. 2018, 14, 2074–2081, doi:10.3762/bjoc.14.181

• a ΔδH3 = 0.51 ppm due to the association with the DB24C8 macrocycle through hydrogen bonding. All the evidences reveal that the functionalized macrocycle migrated from the DBA recognition site to the amide station when an external base was added to the solution of rotaxane R1. Then, 3 equiv

Synthesis and supramolecular self-assembly of glutamic acid-based squaramides

• Juan V. Alegre-Requena,
• Marleen Häring,
• Isaac G. Sonsona,
• Alex Abramov,
• Eugenia Marqués-López,
• Raquel P. Herrera and
• David Díaz Díaz

Beilstein J. Org. Chem. 2018, 14, 2065–2073, doi:10.3762/bjoc.14.180

• asymmetric catalysis and molecular recognition [5][6]. Besides, squaramides present a dual ability to recognize anions and cations through hydrogen bonding interactions, acting as ion sensors and transmembrane anion transporters [7]. This property has been crucial for the development of new drugs [8][9

• shifts for characteristic bands such as C=O stretching (≈1735 cm−1), and N–H stretching ≈2867–3000 cm−1 (Supporting Information File 1, Figure S2). This suggests that the gelator may also be aggregated in solution, at least to some extend, via similar hydrogen-bonding interactions than in the gel state

• . In contrast, the spectrum of the xerogel, prepared by freeze-drying the corresponding organogel, revealed a red shift (lower frequency) of the above-mentioned stretching bands compared to solid 3 (C=O Δν ≈5 cm−1; N–H Δν ≈70 cm−1), which is an indication of increased hydrogen-bonding. Characterization

Functionalization of graphene: does the organic chemistry matter?

• Artur Kasprzak,
• Agnieszka Zuchowska and
• Magdalena Poplawska

Beilstein J. Org. Chem. 2018, 14, 2018–2026, doi:10.3762/bjoc.14.177

• the epoxides of the graphene-family material. In a coupling with the inclusion of graphene-family material and amine hydrohalide some reactions or transformations may occur, but they are based on electrostatic adsorption or hydrogen bonding [23], rather than on covalent modification. If formation of

• inner salt or hydrogen bonding, as the presence of absorption bands located in 1610–1587 cm−1 (asymmetric vibrations of C=O of –COO− and N–H of NH3+) and 1475–1385 cm−1 (symmetric vibrations of C=O of –COO− and N–H of NH3+) ranges indeed implies. The absorption band located at 3016 cm−1, interestingly

• and hydrogen bonding-dependent adsorption of glucose on the RGO surface results in a shift of the absorption bands coming from the C=O of RGO (from 1724 cm−1 to 1735 cm−1). Another consideration is that this process further influences the obtained material’s morphology, properties and thermal

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

• by three-dimensional networks through self-assembly have drawn significant attention in the past decades. They are normally fabricated by means of noncovalent intermolecular interactions [3], such as π–π stacking, hydrogen bonding, van der Waals forces, hydrophobic, electrostatic, host–guest and

• is used as a candidate to form a new chiro-optical system [30][36][37][38][39][40][41]. Ureidopyrimidinone (UPy), as a connection site, is also introduced to make quadruple hydrogen bonding [42][43][44]. The structure and schematic representation of 3 are shown in Figure 1. The possible assembly

• Discussion The monomolecular compound 3 can be easily synthesized in 3 steps. The compound has the necessary features for gel formation. The quadruple hydrogen bonding created by UPy moieties is quite stable in nonpolar solvents. Therefore, the molecule can easily assemble into dimers. Then, the trans

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• nucleotides must possess selectivity towards these anions. From this point of view, nucleotide receptors based on polyammonium cations are of great demand because the electrostatic interactions of such polyammonium systems and negatively charged phosphates are strong. Hydrogen bonding [8] and π-stacking

• macrocycles 10a, 12a,b (Figure 3) can be rationalized in terms of the binding properties of the investigated nucleotides. Moreover, the presence of intramolecular hydrogen bonding (Figure 4a and b) can explain the protonation of only one nitrogen atom despite the close protonation constants of both primary

A pyridinium/anilinium [2]catenane that operates as an acid–base driven optical switch

• Sarah J. Vella and
• Stephen J. Loeb

Beilstein J. Org. Chem. 2018, 14, 1908–1916, doi:10.3762/bjoc.14.165

• )ethane recognition site [18]. In particular, the significant downfield shifts observed for ethylene protons s and t from 5.30 ppm in 74+ to 5.56 ppm for [8DB24C8]6+ as well as u and r, the ortho pyridinium protons, from 9.04 ppm in 74+ to 9.31 ppm for [8DB24C8]6+ are characteristic of hydrogen-bonding to

Asymmetric Michael addition reactions catalyzed by calix[4]thiourea cyclohexanediamine derivatives

• Zheng-Yi Li,
• Hong-Xiao Tong,
• Yuan Chen,
• Hong-Kui Su,
• Tangxin Xiao,
• Xiao-Qiang Sun and
• Leyong Wang

Beilstein J. Org. Chem. 2018, 14, 1901–1907, doi:10.3762/bjoc.14.164

• reaction, the question arises, which one is activated by the thiourea group through double hydrogen bonding. Based on the better enantioselectivity observed for product 9a over 9b–k, it was deduced that the binding of the nitroolefin with the calixarene cavity might be affected by the steric hindrance of

• the groups present on the aromatic ring. We propose the following plausible synergistic catalytic mechanism (Scheme 3). First, the two oxygen atoms of the nitro group in the nitrostyrene are activated through double hydrogen bonding with the thiourea group, while the benzene ring is held by a

A hemicryptophane with a triple-stranded helical structure

• Augustin Long,
• Olivier Perraud,
• Erwann Jeanneau,
• Christophe Aronica,
• Jean-Pierre Dutasta and
• Alexandre Martinez

Beilstein J. Org. Chem. 2018, 14, 1885–1889, doi:10.3762/bjoc.14.162

• are twisted into a triple helix with the lone pair of the amines and the amide hydrogen atoms oriented toward the cavity, while the amide oxygen atoms are oriented outwards. Intramolecular hydrogen bonding between the nitrogen of the amine function of one linker with the N–H of the amide group of

• another arm can account for this helical structure (Namine···Namide distances of 2.97 Å). This structure sheds light on the excellent yield achieved in the last step of the synthesis. Indeed, such intramolecular hydrogen bonding probably also occurred in the imine precursor, accounting for its high

• hemicryptophane 1 bearing both amide and amine functions in its three likers. In solution, the 1H NMR spectrum shows a C3 symmetrical cage, which is also observed in the solid state by X-ray crystallography. Moreover, in the solid, amide and amine functional groups of different linkers interact through hydrogen

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

• Alphonse Fiebor,
• Richard Tia,
• Banothile C. E. Makhubela and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1859–1870, doi:10.3762/bjoc.14.160

• summarised in Table 1. Formation of the tridentate pincer complex was confirmed by the crystal structure of 17d. The structure is accompanied by two lattice water molecules interacting with each other and an uncoordinated chloride ion through hydrogen bonding. The expected square planar geometry of palladium

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• asymmetric induction. The NH group engages hydrogen bonding with the acetoxy groups located at an iodine(III) center to form two nine-membered rings, which were confirmed by the crystal structure of the iodine(III) reagent 16 [53]. The hydrogen bonding effect is crucial to a supramolecular helical chiral

• attack of acetates to the exposed re-face establishes the S-configured benzylic C–O bond. Without the hydrogen bonding effect, the same reaction with a diester-containing iodoarene catalyst was explored [55]. The sterically hindered adamantyl-substituted catalysts 17 were demonstrated to be efficient to

• engages in double hydrogen bonding to form an 11-membered ring, resulting in the chiral helicity. The helical chirality induced in iodine(III) derivatives of 23 bearing the bislactamide motif was described for 27 with an efficient differentiation of the enantiotopic faces of the styrene substrate. This

Host–guest complexes of conformationally flexible C-hexyl-2-bromoresorcinarene and aromatic N-oxides: solid-state, solution and computational studies

• Rakesh Puttreddy,
• Ngong Kodiah Beyeh,
• S. Maryamdokht Taimoory,
• Daniel Meister,
• John F. Trant and
• Kari Rissanen

Beilstein J. Org. Chem. 2018, 14, 1723–1733, doi:10.3762/bjoc.14.146

• driven by hydrogen bonding [55][56]. Taking the example of BrC6 and 3, a similar moderate deshielding of the hydroxy groups of the BrC6 receptor and a minor deshielding of the aromatic protons of the guest signals are observed (Figure 5) confirming this assembly is also driven by hydrogen bonding. These

• intermolecular hydrogen bonding and stacking interactions at both upper and lower-rims. The chemical structures of C-ethyl-2-bromoresorcinarene (BrC2), C-propyl-2-bromoresorcinarene (BrC3) and C-hexyl-2-bromoresorcinarene (BrC6) as hosts and pyridine N-oxide (1), 2-methylpyridine N-oxide (2), 3-methylpyridine N

• receptor renders the receptor slightly electron deficient further facilitating π–π interactions. With the larger N-oxide guests 10–12, though the shift changes of the guest are not strong enough to conclusively indicate endo complexation, clear changes in the hydroxy groups suggest interaction via hydrogen

Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles

• Dennis Hiltrop,
• Steffen Cychy,
• Karina Elumeeva,
• Wolfgang Schuhmann and
• Martin Muhler

Beilstein J. Org. Chem. 2018, 14, 1428–1435, doi:10.3762/bjoc.14.120

• reactions over Pt single crystal, polycrystalline Pt and Pt/C electrodes. They proposed two different adsorbate structures of hydrated alkali metal cations on the electrode, either via a hydrogen bonding between hydrating water and two OHad groups (1) or direct ion–dipole interactions between two OHad and

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• mol % 20a was used as catalyst. A dual activation model was proposed for the reaction (Figure 3). According to this mechanism, the aldehyde is activated by the phenolic hydroxy group of calix[4]arene through hydrogen bonding, while nitromethane is activated by tertiary amine group of the catalysts

• water. The high catalytic efficieny of this proline-functionalized calix[4]arene organocatalyst was attributed to the presence of the amide group and its synergistic effect through hydrogen-bonding interaction with the substrate. The scope and limitations of the asymmetric aldol reactions between a wide

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• a high level of enantioselectivity. Naphthol derivatives 31 were converted to spirocyclic lactones 32 in the presence of m-CPBA as co-oxidant for the in situ generation of the I(III) catalyst. Secondary n–π* and/or hydrogen-bonding interactions of the catalyst ensured remarkable enantioselectivities

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

• -substituted moieties in (Z)-4–7 make intramolecular stabilizing interactions unlikely. Nevertheless, it can be envisioned that the freely rotatable Ar–CH2–Ar units should allow the formation of close proximity conformers of (Z)-4a in solution, in which attractive interactions, such as hydrogen bonding and

• compound in these solvents. In 1,4-dioxane and DMSO the isomerization depends on the temperature. While the rates are in comparison rather long at 25 ºC, these processes are considerably faster at 35 ºC. As outlined before, several stabilizing interactions such as LD, hydrogen bonding and solvation effects

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• group, was found to be extremely potent (MIC values in the range of 0.5–13 μg mL−1) against several strains of S. aureus, both methicillin-sensitive and resistant strains. High antimicrobial activity, shown by this drug, was due to the presence of a hydrophobic head group with a hydrogen-bonding

• activities were evaluated [102]. A molecular docking study has revealed that GRA interacts with ct-DNAs via hydrogen bonding interactions between the oxygen atoms of GRA and adenine bases of DNA and van der Waals interactions. Moreover, GRA significantly reduces the polymerization activity of DNA polymerase

• involve in the intramolecular hydrogen bonding which is attributed to its planar orientation whereas the chlorophenyl moiety, the heterocyclic fragment with the C5 and C7 hydroxy groups and C8 piperidinyl substituent in FLP favor non-planar binding geometry. The author examined their sequence-specific

Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines

• Felix Scheidt,
• Christian Thiehoff,
• Gülay Yilmaz,
• Stephanie Meyer,
• Constantin G. Daniliuc,
• Gerald Kehr and
• Ryan Gilmour

Beilstein J. Org. Chem. 2018, 14, 1021–1027, doi:10.3762/bjoc.14.88

• conformations around the two respective torsion angles [37][38]. In this case, it is also highly probable that hydrogen bonding will reinforce these conformational preferences. Whilst it was not possible to isolate crystals of 3 that were suitable for X-ray analysis, it was possible to unambiguously establish

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

• contain both adenine and thymine derivatives. The specificity of the Ade–Thy hydrogen bonding was not disrupted in the presence of non-interacting bases. Tsiourvas and co-workers obtained a similar result after grinding an equimolar mixture of the hexadecylammonium salts of a succinylated acyclovir

On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site

• Eirinaios I. Vrettos,
• Gábor Mező and
• Andreas G. Tzakos

Beilstein J. Org. Chem. 2018, 14, 930–954, doi:10.3762/bjoc.14.80

• characterized in 1966 by Wall et al. [96][97]. The main mechanism of action involves binding to the reversible complex of topoisomerase I (topo I) and the 3′-phosphate group of the DNA backbone through hydrogen bonding, resulting in accumulation of a persistent ternary complex (the cleavable complex). This