Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• of the acid and the directionality of the hydrogen bond pattern of the acid dimer. Cross metathesis of monovinyl-substituted POSS with olefins has been reported for the first time by Marciniec [18]. It was demonstrated that monovinylheptaisobutyl-substituted octasilsesquioxane (monovinyl-POSS

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• these studies should facilitate the development of new ligands. In terms of mapping of glutamate receptors hydroxyglutamic acids 2–4 (Figure 2) should be of great interest since an additional hydroxy group is capable of acting as a hydrogen bond donor as well as a hydrogen bond acceptor. In fact (2S,4S

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• )–2.05(2) Å) than with chlorosilanol 8 (OH···2.16(0) Å). Due to its two hydroxy units, the silanediol 9 shows higher catalytic activity as hydrogen bond donor than chlorosilanol 8, e.g., C–C coupling N-acyl Mannich reaction of silyl ketene acetals 11 with N-acylisoquinolinium ions (up to 85% yield and 12

• ]) to the corresponding silanediols. While hydrolyses of dichlorosilanes have been studied extensively [23][24][25], hydrolyses of alkoxy dichlorosilanes are much less explored. Hydrogen bond donor (HBD) catalysis is an emerging field in organic synthesis [26][27][28], employing, e.g., squaramides [29

• the OH(ax) and the Cl(eq) is found, in addition to the C–H interaction (dotted line, Figure 9), which stabilized the leaving Cl ion with a weak hydrogen bond. In the front attack mechanisms for the second hydrolytic step only stabilizing C–H interactions from the fenchyl group to the chloro atom occur

Computational characterization of enzyme-bound thiamin diphosphate reveals a surprisingly stable tricyclic state: implications for catalysis

• Ferran Planas,
• Michael J. McLeish and
• Fahmi Himo

Beilstein J. Org. Chem. 2019, 15, 145–159, doi:10.3762/bjoc.15.15

• with ThDP, all of which are expected to affect the cofactor’s geometry and energy. Of particular interest is the conserved Glu47 residue which forms a hydrogen bond to N1' of the pyrimidine ring. It is important to note that, during the geometry optimizations of the three states YIH+, APH+ and TCH

• hydrogen bond between the Nε and the exocyclic N4' amino group, a bond that is not present in the other states. With that notable exception, the overall geometries of the different states are quite similar, and bond distances are also fairly consistent (Figure 3). As with model A, the AP state is found to

• changes somewhat between the states (Figure 4). Interestingly, there is a hydrogen bond from the water to the anionic C2 carbon in the YI state (OH…C distance of 1.91 Å), with the negative charge on C2 further stabilized by interaction with the exocyclic NH2 group (NH…C distance of 2.17 Å). The

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

• groups at 3- and 5-positions. The most stable conformer 2A contains a hydrogen bond between the OH group at 5 position and the carbonyl group at 4 position. The overall conformation is sensitive to the direction of the OH group at 3 position. The OH isomer at 3 position (2B) was significantly

• to rotation of the OH group at 5 position destabilizes the system dramatically, as in 2C, by 9.7 kcal/mol (in the gas phase) and 5.4 kcal/mol (in DMSO); however, the hydrogen bond is not crucial for the overall planar structure. The structures and energies of all possible isomeric mono-anions derived

• -anion 2C) derived from the neutral conformation 2C. The 3-anion 2C was significantly more unstable than 3-anion 2A, the geometrical difference being only the flip of the OH group at 5 position. This is consistent with a large stabilizing contribution of the hydrogen bond. The 5-anion 2A was the most

The activity of indenylidene derivatives in olefin metathesis catalysts

• Maria Voccia,
• Steven P. Nolan,
• Luigi Cavallo and
• Albert Poater

Beilstein J. Org. Chem. 2018, 14, 2956–2963, doi:10.3762/bjoc.14.275

• there is a hydrogen bond (Ru···H) that affects the charge on the metal, especially strong when the indenylidene is substituted. The Ru···H distances for 1–6 are 3.110, 3.167, 3.004, 3.036 Å, 2.944, 2.929 Å, respectively (see Figure 2). This interaction is due to the rotation of 90° of the indenylidene

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

• has been shown that E-isomers of neutral imines can be stabilised by an intramolecular C=N−H···OMe hydrogen bond with a neighbouring methoxy group. Electron-donating OMe groups dramatically increase the basicity of the imino nitrogen, forcing the latter to abstract a proton from the proton sponge

• moiety in monoprotonated forms. The participation of the out-inverted and protonated 1-NMe2 group in the Me2N−H···NH=C hydrogen bond is experimentally demonstrated. It was shown that the number and position of OMe groups in the aromatic substituents strongly affects the rate of the internal hindered

• rotation of the NH2+ fragment in dications. Keywords: hydrogen bond; imine; NMR; proton sponge; superbase; Introduction It is well known that the extremely high basicity of 1,8-bis(dimethylamino)naphthalene (1, DMAN; pKa = 12.1 in H2O [1][2], 18.62 in MeCN [3], 7.5 in DMSO [4]) and its derivatives

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• between H(1) and H(4) in the NOE experiment. The structure contains two carbonyl moieties C(6)–O(2) and C(3)–O(1) with similar distances of 1.222 and 1.218 Å, respectively. The intramolecular hydrogen bond O(1)–H(13) remains strong in the nitrogenated tricycle (2.579 Å) vis-à-vis of the starting hydrazide

• imino-carboxylic acid form likely evolves to its iminium-carboxylate form B [50]. This last intermediate involves the existence of two possible transition states for the cyclization of the imidazolidinone core of which one of them is favored by an intramolecular hydrogen bond (Scheme 5). This control is

Non-native autoinducer analogs capable of modulating the SdiA quorum sensing receptor in Salmonella enterica serovar Typhimurium

• Matthew J. Styles and
• Helen E. Blackwell

Beilstein J. Org. Chem. 2018, 14, 2651–2664, doi:10.3762/bjoc.14.243

• ) [21][22]. C) The solid-state structure of the SdiA homodimer (PDB 4Y15; monomers shown in green and grey) bound to OOHL (cyan) [22]. D) Selected residues surrounding OOHL (cyan) in the SdiA ligand binding pocket (from PDB 4Y15 [22]): hydrogen bond acceptors/donors (orange), hydrophobic residues (grey

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

• Christian Schütz and
• Martin Empting

Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

• could prevent activation of the carbonyl group as a CoA-ester. In 2017, Witzgall et al. were able to co-crystallize 6-FABA-AMP within the N-terminal domain of PqsA (Figure 4) [46]. Key interactions involve a water-mediated hydrogen bond between the amino function of the compound and Q162, as in

• anthraniloyl-AMP. The reason why the fluorinated anthraniloyl-AMP shows good affinity is the formation of a hydrogen bond of the fluorine with the G279 backbone amide hydrogen and furthermore an interaction with the N7 position of the adenine moiety. Additionally a very typical fluorine/main-chain interaction

• , the chlorine is able to occupy a vacant sub pocket. A hydrogen bond is found between the backbone oxygen of L207 and the 3-NH2 hydrogen atoms. Interestingly, adding the chlorine substituent in 7-position of PQS leads to a 135 times more potent agonist, indicating the importance of the vacant sub

Synthesis of dihydroquinazolines from 2-aminobenzylamine: N³-aryl derivatives with electron-withdrawing groups

• Nadia Gruber,
• Jimena E. Díaz and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2018, 14, 2510–2519, doi:10.3762/bjoc.14.227

• . Such effect would result from an intramolecular hydrogen bond between the ammonium and nitro groups in the reaction intermediate, also known as “built-in solvation” [71] (Figure 2). When 2-ABA was reacted with 2-chloro-3-nitropyridine (CNP) in analogous experimental conditions as 2a, compound 2c was

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• appeared as a sharp signal at 5.25 ppm (CDCl3) for 29 and as a broad peak at 3.00 ppm for 30. This can be explained by the presence of an intramolecular hydrogen bond that is possible only in the case of 29. Since the 1H NMR spectrum of cyanohydrin 22 exhibits a sharp hydroxy peak at 5.29 ppm, we derive

Catalyst-free synthesis of 4-acyl-NH-1,2,3-triazoles by water-mediated cycloaddition reactions of enaminones and tosyl azide

• Lu Yang,
• Yuwei Wu,
• Yiming Yang,
• Chengping Wen and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2018, 14, 2348–2353, doi:10.3762/bjoc.14.210

• -triazoline 4 which couples to water by strong hydrogen bond effect [51]. The presence of the hydrogen bonds may promote the elimination of the amino group and the acidic C–H bond at the α-position of the acyl group, which affords N-tosyl-1,2,3-triazole 5. Under the present reaction conditions, the

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