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

Selective formation of a zwitterion adduct and bicarbonate salt in the efficient CO₂ fixation by N-benzyl cyclic guanidine under dry and wet conditions

• Yoshiaki Yoshida,
• Naoto Aoyagi and
• Takeshi Endo

Beilstein J. Org. Chem. 2018, 14, 2204–2211, doi:10.3762/bjoc.14.194

• structure was fairly stabilized because of the multi hydrogen bond in the intermolecular. Conclusion The efficient CO2 fixation by N-benzyl cyclic guanidine 1 was achieved by bubbling dry CO2 in CH3CN at 25 °C for 2 h. In addition, the zwitterion adduct 2 and bicarbonate salt 3 were selectively prepared

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

• conjugated to an aromatic cyclobutenedione ring, can be easily synthesized from different derivatives of squaric acid and amines [1][2][3][4]. The possibility to fabricate chiral squaramide derivatives and their efficient hydrogen bond donor/acceptor ability has driven the pivotal role of these compounds in

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

• (above 1700 cm−1) and a new absorption band in the wavenumber range of 1550 cm−1 to 1620 cm−1 can be directly inferred from the formation of either a hydrogen bond between primary amine and the carboxyl groups of GO or an inner salt formation (i.e., COO−NH3+). The presence of the amide bond in the

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

• supramolecular host–guest interaction with the calixarene to form a stable transition state A. Then, another hydrogen bond is formed between the nitrogen atom of the tertiary amine group in A and acetylacetone in its enol form, leading to the formation of a ternary complex B. Finally, nucleophilic attack of

Preparation and X-ray structure of 2-iodoxybenzenesulfonic acid (IBS) – a powerful hypervalent iodine(V) oxidant

• Irina A. Mironova,
• Pavel S. Postnikov,
• Rosa Y. Yusubova,
• Akira Yoshimura,
• Thomas Wirth,
• Viktor V. Zhdankin,
• Victor N. Nemykin and
• Mekhman S. Yusubov

Beilstein J. Org. Chem. 2018, 14, 1854–1858, doi:10.3762/bjoc.14.159

• (≈1.87–1.88 Å), their short (≈2.59 Å) O(6)···O(12) distance, and a small electron density close to O(6) and O(12). Thus, a proton was added at the small electron density region to the O(6) atom. Such proton positioning results in the formation of an expected strong hydrogen bond (≈1.87 Å ) in the O(6)–H

First thia-Diels–Alder reactions of thiochalcones with 1,4-quinones

• Grzegorz Mlostoń,
• Katarzyna Urbaniak,
• Paweł Urbaniak,
• Anna Marko,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2018, 14, 1834–1839, doi:10.3762/bjoc.14.156

• centrosymmetric, the compound in the crystal is racemic. The S-atom of the thiophene ring is disordered over two unequally occupied positions as a result of slight but opposite directions of envelope puckering of the ring. The hydroxy group forms an intramolecular hydrogen bond with the adjacent quinoid O-atom

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

• with the observations made from the crystal structures. 1H NMR host–guest solution studies Guest binding studies of the N-oxide guests (1–12) by the receptor BrC6 were investigated in solution via a series of 1H NMR experiments in different hydrogen bond competing solvents and solvent mixtures: acetone

• bonding (Figures S10–S12, Supporting Information File 1). Due to fast H/D exchange processes on the NMR time scale at 298 K in protic solvents, the hydrogen bond interactions between host and guests were not observed. In CD3OD/CDCl3, complexation-induced chemical shift changes of the guests are observed

• crystallography and 1H NMR solution studies in three different hydrogen-bond-competitive solvents. In the solid state, BrC6 undergoes large cavity conformational changes to accommodate the N-oxide guests compared to our previously studied host systems, C-ethyl-2-bromoresorcinarene and C-propyl-2

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

• strong hydrogen bond acceptor solvents, such as DMSO-d6 [45], then the NH groups are exposed to the solvent rather than developing intramolecular hydrogen bonds. Conversely, a TG value less negative than −4 ppb K−1 discloses the NH group preference towards intramolecular hydrogen bonds formation, at room

• temperature, e.g., with s-triazine LPs N-1, -3, -5. If so, the compounds under investigation (Table 3) exhibited TG values denoting significant (peripheral) >N–H···O=SMe2 hydrogen bond interactions. TGs moderately increased, from −5.55 ppb K−1 in G-1 D-N

  NH to about −6.00 ppb K−1 in G-2 dendrimers, together

• influence on the peripheral (T-0) NH groups/DMSO solvation as they maintained almost the same TG (−6.00 ppb K−1 in 8 vs −6.15 ppb K−1 in 9). In contrast, the inner (T-2) NH groups of 9 appeared “protected” against DMSO (as a hydrogen bond acceptor) because their TG was only −2.00 ppb K−1, (much less

The phenyl vinyl ether–methanol complex: a model system for quantum chemistry benchmarking

• Dominic Bernhard,
• Fabian Dietrich,
• Mariyam Fatima,
• Cristóbal Pérez,
• Hannes C. Gottschalk,
• Axel Wuttke,
• Ricardo A. Mata,
• Martin A. Suhm,
• Melanie Schnell and
• Markus Gerhards

Beilstein J. Org. Chem. 2018, 14, 1642–1654, doi:10.3762/bjoc.14.140

• -chemical calculations in order to investigate the delicate interplay of noncovalent interactions. The complementary results of vibrational and rotational spectroscopy applied in molecular beam experiments reveal the preference of a hydrogen bond of the methanol towards the ether oxygen (OH∙∙∙O) over the π

• include the works on benzene–methanol clusters by the Zwier group [11] and on fluorobenzene–methanol clusters by the Brutschy group [12], to mention only two examples. Complexes of aromatic ethers with polar solvent molecules are of special interest due to the presence of different competing hydrogen bond

• complexes [25] investigated by jet FTIR spectroscopy. The observed OH stretching red-shifts compared to the free alcohols are small, indicating a comparatively weak hydrogen bond, which is also reflected in calculated binding energies [24][25]. With the herein presented work, we now extend our overall multi

Cobalt-catalyzed C–H cyanations: Insights into the reaction mechanism and the role of London dispersion

• Eric Detmar,
• Valentin Müller,
• Daniel Zell,
• Lutz Ackermann and
• Martin Breugst

Beilstein J. Org. Chem. 2018, 14, 1537–1545, doi:10.3762/bjoc.14.130

• -coordination. The resulting intermediate 6a is stabilized by an agostic interaction between the C–H bond and the metal atom as well as by an additional weak hydrogen bond between the C–H bond and the acetate oxygen (O…H distance 2.26 Å). A natural population analysis of structure 6a further confirms the

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

• , then two additional interaction forces in the complex are produced on the same plane, including: 1) the carbonyl of 2 makes a hydrogen bond with the hydroxy group of C7; 2) the phenyl group of 2 forms a face-to-face π-stacking interaction with the benzyl moiety of C7. The complex of 2 with C7 goes to

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

• both catalysts gave the Michael adduct in excellent yields, high ees were obtained only when 54b was used as organocatalyst (up to 94% ee, Scheme 16). During the last decade, squaramide catalysts have become a powerful alternative to the urea/thiourea and guanidine catalysts as multiple hydrogen bond

A three-armed cryptand with triazine and pyridine units: synthesis, structure and complexation with polycyclic aromatic compounds

• Claudia Lar,
• Adrian Woiczechowski-Pop,
• Attila Bende,
• Ioana Georgeta Grosu,
• Natalia Miklášová,
• Elena Bogdan,
• Niculina Daniela Hădade,
• Anamaria Terec and
• Ion Grosu

Beilstein J. Org. Chem. 2018, 14, 1370–1377, doi:10.3762/bjoc.14.115

• cryptand 2 they were 3.27 Å and 3.21 Å, respectively. Since the 3,5-dicyanopyridine fragment contains hydrogen-bond acceptor nitrogen atoms it might be possible to select a guest system which besides the stacking interaction could establish extra hydrogen bonds to enhance the complex stability. Accordingly

• , the O–H···N fragment did not preserve its hydrogen-bond arrangement, as the aromatic fragment rather preferred the so-called “antiparallel-displaced” configuration [40][41] (see Figure 6). The intermolecular interaction energy between 1,5-dihydroxynaphthalene and cryptand 2 is −29.28 kcal/mol, while

• -dihydroxynaphthalene. The higher affinity for anthracene and pyrene than for the dihydroxylated aromatic guest is explained by the influence of the polar solvent (DMSO). Molecular modelling revealed the preference for aryl–aryl stacking instead of a hydrogen bond between the donor OH groups of the guest and the

Novel unit B cryptophycin analogues as payloads for targeted therapy

• Eduard Figueras,
• Adina Borbély,
• Mohamed Ismail,
• Marcel Frese and
• Norbert Sewald

Beilstein J. Org. Chem. 2018, 14, 1281–1286, doi:10.3762/bjoc.14.109

• the vinca domain (Lys176, Val177 and Tyr210). Other than previously reported [52], the methoxy group of subunit B forms a hydrogen bond with Lys176 (Figure 2). Another binding mode of 2 with high binding affinity and hydrogen bond formation did not involve any interaction of subunit B, yet it was

• the other derivatives 23 and 24 (Figure 4). Besides hydrogen bond formation and binding affinity of inhibitors 2, 23 and 24, π-interactions and hydrophobic contacts with the binding pocket of the vinca domain were detected that would in turn increase the affinity of the inhibitor and its effect on the

• magenta. Docking of 22 to the vinca domain of β-tubulin. Surface and backbone of β-tubulin are shown in blue, GDP in yellow. No hydrogen bond formation was detected. The orientation of the azidoethoxy-ethoxyethyl substituent prevents the inhibitor from the correct interaction with the protein. The epoxide

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

• substituent (3-quinolinyl nitrogen forming a hydrogen bond with a guanine amino group at the base of the minor groove) and a low pKa tail group. This drug was further selected for the treatment of Gram-positive bacteria Clostridium difficile infections and is currently in the phase II clinical trials

• selectively bind mixed G·C and A·T sequences of DNA. They hypothesized that thiophene (positive electrostatic potential) and the electron-donor nitrogen of N-MeBI should pre-organize the conformation for accepting hydrogen bond from G-NH2, which was validated by replacing the thiophene moiety with other

• ) were designed and synthesized by Dervan et al. and followed by other groups. It was observed that pyrrole/imidazole polyamides were able to bind side-by-side in the minor groove of DNA with high affinity and in a sequence-specific manner. Crystal structure studies confirmed the existence of a hydrogen

Correlation effects and many-body interactions in water clusters

• Andreas Heßelmann

Beilstein J. Org. Chem. 2018, 14, 979–991, doi:10.3762/bjoc.14.83

• explicitly or implicitly influenced by a water environment. An example for this is the hydrogen-bond cooperativity effect that can have a significant impact on the properties of the bare solute molecules [1]. In order to describe such phenomena, computer simulations have become an indispensable tool, since

Local energy decomposition analysis of hydrogen-bonded dimers within a domain-based pair natural orbital coupled cluster study

• Ahmet Altun,
• Frank Neese and
• Giovanni Bistoni

Beilstein J. Org. Chem. 2018, 14, 919–929, doi:10.3762/bjoc.14.79

• . This information is used to rationalize the trend of stability of various conformers of the water and hydrogen fluoride dimers. Keywords: DLPNO-CCSD(T); hydrogen-bond interaction; interaction energy; local energy decomposition; London dispersion; Introduction Hydrogen bonds are of fundamental

Crystal structure of the inclusion complex of cholesterol in β-cyclodextrin and molecular dynamics studies

• Elias Christoforides,
• Andreas Papaioannou and
• Kostas Bethanis

Beilstein J. Org. Chem. 2018, 14, 838–848, doi:10.3762/bjoc.14.69

• numerous van der Waals and C–H···O interactions mainly between the guest and the inner dimeric host cavity. The observed host–guest interactions along with the extended hydrogen bond network between water molecules, hosts and guest are listed analytically in Supporting Information File 1, Table S1. In

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

Investigations towards the stereoselective organocatalyzed Michael addition of dimethyl malonate to a racemic nitroalkene: possible route to the 4-methylpregabalin core structure

• Denisa Vargová,
• Rastislav Baran and
• Radovan Šebesta

Beilstein J. Org. Chem. 2018, 14, 553–559, doi:10.3762/bjoc.14.42

• malonate catalyzed by hydrogen-bond-donating organocatalysts (Scheme 2). We have also briefly investigated Meldrum´s acid as a donor, instead of dimethyl malonate, but we have obtained a complicated reaction mixture, which was difficult to purify. Therefore, we have focused our attention on the Michael

• synthesized binaphthol-squaramide catalysts (Sa,R,R)-C8, and (Sa,S,S)-C8 (Scheme 3). Results of the initial catalyst screening are summarized in Table 1. The binaphthyl structural motif has already been employed in the hydrogen-bond-donating organocatalysis [35][36]. However, the binaphthol moiety possessing

• an additional hydrogen bond donor group was not tested in too much depth. Therefore, we have synthesized two binaphthol-based diastereomeric squaramide catalysts (Sa,R,R)-C8 and (Sa,S,S)-C8 (Scheme 3). Starting from (S)-BINOL (8), amine 9 was obtained in five steps following literature procedures

Novel amide-functionalized chloramphenicol base bifunctional organocatalysts for enantioselective alcoholysis of meso-cyclic anhydrides

• Lingjun Xu,
• Shuwen Han,
• Linjie Yan,
• Haifeng Wang,
• Haihui Peng and
• Fener Chen

Beilstein J. Org. Chem. 2018, 14, 309–317, doi:10.3762/bjoc.14.19

• moiety as monodentate hydrogen bond donor to activate the electrophile (anhydride), whilst retaining the tertiary amine functionality to activate the nucleophile (alcohol, Figure 2). As part of our ongoing research program on chloramphenicol base organocatalysis, herein, we report a new class of

• Lingjun Xu Shuwen Han Linjie Yan Haifeng Wang Haihui Peng Fener Chen Department of Chemistry, Fudan University, Shanghai 200433, PR China 10.3762/bjoc.14.19 Abstract A family of novel chloramphenicol base-amide organocatalysts possessing a NH functionality at C-1 position as monodentate hydrogen

• bond donor were developed and evaluated for enantioselective organocatalytic alcoholysis of meso-cyclic anhydrides. These structural diversified organocatalysts were found to induce high enantioselectivity in alcoholysis of anhydrides and was successfully applied to the asymmetric synthesis of (S

Fluorogenic PNA probes

• Tirayut Vilaivan

Beilstein J. Org. Chem. 2018, 14, 253–281, doi:10.3762/bjoc.14.17

• ) appending a fluorophore onto a natural nucleobase and (iii) the use of unnatural, intrinsically fluorescent nucleobases. They can be divided into fluorescent nucleobases capable of hydrogen bond formation, which can form specific base pairs with canonical nucleobases, and those that cannot (i.e., universal

• they will be non-responsive to the base pairing similar to PNA carrying tC or tCO [177]. Pyrrolocytosine is another intrinsically fluorescent hydrogen-bond-forming nucleobase that has been extensively studied in a DNA context [188][189]. When incorporated into PNA, the simple phenyl-substituted

Stereochemical outcomes of C–F activation reactions of benzyl fluoride

• Neil S. Keddie,
• Pier Alexandre Champagne,
• Justine Desroches,
• Jean-François Paquin and
• David O'Hagan

Beilstein J. Org. Chem. 2018, 14, 106–113, doi:10.3762/bjoc.14.6

• C–F activation of benzylic fluorides for nucleophilic substitutions and Friedel–Crafts reactions, using a range of hydrogen bond donors such as water, triols or hexafluoroisopropanol (HFIP) as the activators. This study examines the stereointegrity of the C–F activation reaction through the use of

• demonstrated that both associative and dissociative pathways operate to varying degrees, according to the nature of the nucleophile and the hydrogen bond donor. Keywords: benzylic fluorides; C–F activation; chiral liquid crystal; 2H NMR; PBLG; stereochemistry; Introduction The C–F bond is the strongest

• ]. Protocols using water/isopropanol [3], optimally coordinated triols [4][5], and hexafluoroisopropanol (HFIP) [6][7] as the corresponding hydrogen bond donors have shown considerable success. This mode of activation has been demonstrated for amination [3][4][5] and Friedel–Crafts reactions [6][7] on benzylic

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids – tutorial

• Tamara Šmidlehner,
• Ivo Piantanida and
• Gennaro Pescitelli

Beilstein J. Org. Chem. 2018, 14, 84–105, doi:10.3762/bjoc.14.5