Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

• Ekaterina V. Kolupaeva,
• Narek A. Dzhangiryan,
• Alexander F. Pozharskii,
• Oleg P. Demidov and
• Valery A. Ozeryanskii

Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24

• studied for the first time. In addition to the pronounced tendency of the title compound to form associates with an intramolecular hydrogen bond of the NHN type (new examples with the participation of pyridine rings, including self-associates are shown) and its inertness to amination reactions of the

• (Supporting Information File 1, Figure S13). This is a rather low value for chelate-type cations, but at the same time, it is quite logical, as molecule 14 contains a short CH=CH bridge, which increases the internitrogen distance and stretches (that is, weakens) the intramolecular hydrogen bond. For

• compounds 5·HBF4 and 8·HBF4 were recrystallized from acetonitrile and subjected to XRD analysis under the same conditions. Selected data obtained are shown in Table 1. As can be seen, in both protonated quinoquinoline systems, an intramolecular hydrogen bond is realized (strongly asymmetric in crystals, but

Experimental and theoretical studies on the synthesis of 1,4,5-trisubstituted pyrrolidine-2,3-diones

• Nguyen Tran Nguyen,
• Vo Viet Dai,
• Nguyen Ngoc Tri,
• Luc Van Meervelt,
• Nguyen Tien Trung and
• Wim Dehaen

Beilstein J. Org. Chem. 2022, 18, 1140–1153, doi:10.3762/bjoc.18.118

• -Trisubstituted pyrrolidine-2,3-dione derivatives were prepared from the above mentioned 2-pyrrolidinone derivatives and aliphatic amines, which exist in enamine form and are stabilized by an intramolecular hydrogen bond. A possible reaction mechanism between 3-pyrroline-2-one and aliphatic amine (CH3NH2) was

• ···O intramolecular hydrogen bond (distance ca. 1.7–1.8 Å) (cf. Figures 4–6). The isomerization of 4a/4a’ is extremely fast due to the high rate constant of about 1012 s−1 at 298 K, calculated by the transitional state theory method and quantum tunneling effect [47]. It is thus impossible to

• broad peak corresponding to the proton of the secondary amino group (NH) at a chemical shift of 11.74 ppm. The intramolecular hydrogen bond led to the appearance of a resonance signal of the amino group at high chemical shift. Also, the coupling between the amino proton and methylene protons was

First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation

• Maxime Pypec,
• Laurent Jouffret,
• Claude Taillefumier and
• Olivier Roy

Beilstein J. Org. Chem. 2022, 18, 845–854, doi:10.3762/bjoc.18.85

• , is consistent with intramolecular hydrogen bond interaction, which is accompanied by a reduction of the exchange rate of the NH proton. In DMSO, we observe reduced NH linewidths, consistent with the fact that this solvent has strong hydrogen bonding and solvation abilities which reduce significantly

• Information File 1). The lowest energy was found for χ1 = 124°, an angle value slightly higher than those found in the crystallographic structure of compound 2 (111 and 116° for conformation B, Table 2). This difference may be a result of the 6-membered intramolecular hydrogen bond formed in the monomer model

Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

• Yelong Lei and
• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

• hydrogen bond. Thus, the tautomerization favors to the left direction, forming D-form products, when α-diazo-β-diketones are as starting materials (R1 = alkyl and aryl), while it predominates to the right direction, generating 2-(alkoxycarbonyl)methyloxazolines as products, when alkyl α-diazo-β

• different chemoselectivities. 2-Alkylideneoxazolidines and 2-alkyloxazolines are structural isomers and can possibly tautomerize each other. As a more electron-withdrawing group with more electron density on the carbonyl group, a ketone favors the conjugation of the double bond as well as the intramolecular

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• [22]. Moreover, the E geometrical isomer in the –CH=N- double bond has a higher percentage when in dimethyl sulfoxide-d6 solution. On the other hand, the Z isomer can be stabilized in less polar solvents by an intramolecular hydrogen bond. In the present study, the spectral data were recorded in CDCl3

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• of the π-electron density along the molecule, together with an intramolecular hydrogen bond (Figure 1, 1c). Despite the plurality of evidence showing this representation as inappropriate [1], structure 1a remains commonly used in the scientific literature. In this review, biguanides will be

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

• Lukáš Marek,
• Lukáš Kolman,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• rapidly equilibrating (Z)/(E)-isomers [2], the derivatives containing a secondary nitrogen slightly prefer [2][9][48] the (Z)-configuration due to an intramolecular hydrogen bond. A substitution of hydrogen at the methylidene carbon by an aryl group and a secondary nitrogen, enabling an intramolecular

• solid state by X-ray diffraction. The important role of the intramolecular hydrogen bond fixing the (Z)-configuration has also been observed in the crystal structures of other 3-aminomethylidene derivatives containing a primary or secondary nitrogen [14][49][50][51][52]. The (Z)-configuration of the

• hydrogen bond, results in the geometry of a double bond that is locked in a (Z)-configuration [12]. The same (Z)-configuration was observed by us for the primary 3-[amino(aryl)methylidene]oxindoles [33]. The usual method used for the configuration assignment of 3-amino(aryl)methylidene derivatives involves

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• hydrogen bond. This is supported by a smaller deviation of the C(2’’) chemical shift value (61.7 ppm) in comparison to the theoretical shifts for a Csp2 centre. Similar structural analogues are known in the literature [54][83][84][85] but their structural analysis was incomplete. As the aforementioned

• –purine conjugate 5c were 40.9 and 61.7 ppm, respectively. This range does not fully correspond to the theoretical values 80–140 ppm, expected for the Csp2 atom of the N–H form B. In compound 5c the N–H form 5cB is possibly the major tautomer in CDCl3 solution as it is stabilized via an intramolecular

Comparative ligand structural analytics illustrated on variably glycosylated MUC1 antigen–antibody binding

• Christopher B. Barnett,
• Tharindu Senapathi and
• Kevin J. Naidoo

Beilstein J. Org. Chem. 2020, 16, 2540–2550, doi:10.3762/bjoc.16.206

• , the peptide portion has hydrogen bonds between Arg5–Pro8 (26.69% and 26.58%), Arg5–Asp3 (12.45%), an Arg5–Pro2 interaction is observed with an occupancy of 7.13%, and an intramolecular hydrogen bond between the C3 alcohol and the carbonyl of the N-acetyl moiety of the GalNAc has an occupancy of 6.92

• bound antigens are similar. Intramolecular hydrogen-bonding interactions within GalNAc were more dominant in the antibody (have a higher occupation) than in solution. An intramolecular hydrogen bond within the Tn-antigen between the GalNAc–Thr4 (NH of the acetyl group to carbonyl group) may be

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• ; blue – nitrogen; red – oxygen. a) Complex of MC008 with acetate; b) complex of MC006 with formate; c) complex of MC007 with lactate showing an intramolecular hydrogen bond; d) complex of MC009 with lactate showing an additional hydrogen bond with an amide NH of the macrocycle. Binding affinities of the

Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin: experimental and computational evidence for intramolecular and intermolecular C–F···H–C bonds

• Vuyisa Mzozoyana,
• Fanie R. van Heerden and
• Craig Grimmer

Beilstein J. Org. Chem. 2020, 16, 190–199, doi:10.3762/bjoc.16.22

• amongst the weakest of hydrogen bonding phenomena because a carbon acid (C–H) is weak, therefore is a weak donor, and the acceptor is non-polarizable, therefore is a poor acceptor [34][35][36]. Wang and co-workers reported the existence of the C–F···H–C intramolecular hydrogen bond in the structure of

Unexpected one-pot formation of the 1H-6a,8a-epiminotricyclopenta[a,c,e][8]annulene system from cyclopentanone, ammonia and dimethyl fumarate. Synthesis of highly strained polycyclic nitroxide and EPR study

• Sergey A. Dobrynin,
• Igor A. Kirilyuk,
• Yuri V. Gatilov,
• Andrey A. Kuzhelev,
• Olesya A. Krumkacheva,
• Matvey V. Fedin,
• Michael K. Bowman and
• Elena G. Bagryanskaya

Beilstein J. Org. Chem. 2019, 15, 2664–2670, doi:10.3762/bjoc.15.259

• distorted half-chair. Presumably, this difference is due to the formation of an intramolecular hydrogen bond O6–H…O5 (H…O 1.95(2) Å, O–H…O 154(2)°) in molecule 6. In the crystal of 1 the amino group participates in intermolecular hydrogen bonding N1–H…O3 (H…O 2.39(2) Å, N–H…O 167(1)°) forming chains of

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

• Alessandro Iagatti,
• Baihao Shao,
• Alberto Credi,
• Barbara Ventura,
• Ivan Aprahamian and
• Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

• the competition between the intramolecular hydrogen bond between the N–H and C=O groups in the Z-form and hydrogen bonds formed by these functional groups with solvent molecules. The conformational distortion and the increased conformational disorder arising from hydrogen bonding with the solvent can

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• because the proton transfer occurs through an intramolecular hydrogen bond. This is also an origin of a large Stokes shift (8,000–11,000 cm−1) in the emission from the ESIPT state. Consequently, yellow luminescence was observed by UV-excitation [17][18]. Mutai et al. reported an ESIPT luminescence of an

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition

• Yulia V. Khoroshunova,
• Denis A. Morozov,
• Andrey I. Taratayko,
• Polina D. Gladkikh,
• Yuri I. Glazachev and
• Igor A. Kirilyuk

Beilstein J. Org. Chem. 2019, 15, 2036–2042, doi:10.3762/bjoc.15.200

• nitroxides [26], implying free rotation of ethyl groups. In the EPR spectra in toluene the nitroxides 11a–c show 0.035–0.04 mT lower hfs constants on nitrogen atom compared to nitroxides 12a–c, presumably due to intramolecular hydrogen bond formation. The difference in aN between 11a–c and 12a–c is almost

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• , based on 4-(phenyldiazenyl)naphthalen-1-ol. According to the theoretical calculations the enol form stabilization could be achieved through a strong intramolecular hydrogen bond formed between the tautomeric hydroxy group and the carbonyl group from the tautomeric backbone. However, intermolecular

Water inside β-cyclodextrin cavity: amount, stability and mechanism of binding

• Stiliyana Pereva,
• Valya Nikolova,
• Silvia Angelova,
• Tony Spassov and
• Todor Dudev

Beilstein J. Org. Chem. 2019, 15, 1592–1600, doi:10.3762/bjoc.15.163

• “open” configuration the primary hydroxy groups do not participate in intramolecular hydrogen bond interactions. Relatively weak hydrogen bonds are formed between the secondary hydroxy groups in the wider/lower rim of the molecule. The calculations reveal that the “head–tail” arrangement of the narrow

• evaluated at the M062X/6-311++G(d,p)//M062X/6-31G(d,p) level of theory (Supporting Information File 1, Table S1). As a general trend, it was observed that expanding the intramolecular hydrogen bond network upon each H2O addition (comprising the water–water and water–cyclodextrin interactions) enhances the

Synthesis and conformational preferences of short analogues of antifreeze glycopeptides (AFGP)

• Małgorzata Urbańczyk,
• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Jerzy Góra,
• Rafał Latajka and
• Norbert Sewald

Beilstein J. Org. Chem. 2019, 15, 1581–1591, doi:10.3762/bjoc.15.162

• the formation of an intramolecular hydrogen bond are characterized by chemical shifts that are independent on the temperature. When the amide proton is involved in a hydrogen bond, its temperature factor value is lower than 4.0 ppb/K [29][30]. Values of the measured temperature coefficient factors

• bonds between the peptide backbone and GalNAc moiety, which are responsible for creating the extended conformation [31][32]. However, further NMR investigations in this area found no evidence of an intramolecular hydrogen bond, or the existence of a very weak interaction, between the carbonyl group of

• determined, no predominant conformer was found. As shown in Figure 3A and B both tripeptides indicate a fully flexible conformation. Corzana et al. suggested for the C- and N-protected, glycosylated ʟ-serine residue an extended conformation without intramolecular hydrogen bond between the amide proton of

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• biphenyl ring intact. Relative spatial arrangement of the larger phenyl substituent is located at the side where it is relatively far away from the intramolecular hydrogen bond unit. Catalytic studies With the organocatalyst 1 in hand, we firstly examined the oxo-DA reaction of benzaldehyde and Rawal’s

Study on the regioselectivity of the N-ethylation reaction of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide

• Pedro N. Batalha,
• Luana da S. M. Forezi,
• Maria Clara R. Freitas,
• Nathalia M. de C. Tolentino,
• Ednilsom Orestes,
• José Walkimar de M. Carneiro,
• Fernanda da C. S. Boechat and
• Maria Cecília B. V. de Souza

Beilstein J. Org. Chem. 2019, 15, 388–400, doi:10.3762/bjoc.15.35

• structure that the intramolecular hydrogen bond between the hydrogen of the amide group, CON–H, and the carbonyl oxygen (C-4), promotes coplanarity between the oxoquinoline nucleus and the CONH moiety of this amide group connected to C-3, as expected. An additional crystallographic description and the full

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

• for 4a, while the E-form is more stable for 5a–7a. Indeed, the X-ray analysis shows that compound 6a in the solid state exists in the E-form stabilised by the N−H···O intramolecular hydrogen bond (IHB) with an ortho-OMe group (Figure 2a), while compound 4a, as it was revealed in our previous work [7

• , signals are coalescent even at −80 °C (Figure 7). The presence of an OMe group in the ortho-position to C=N groups in 5c slows down the exchange and results in NH2+ signals splitting at −40 °C. This can be attributed to the formation of the weak NHO intramolecular hydrogen bond, which becomes stronger

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

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

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