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

• nitrobenzene. For example, quinoquinoline 5 reacts with chloranil upon heating in toluene to give a dark brown, high-melting product, in which, however, the methylene bridge remains unchanged. According to 1H NMR spectroscopy and combustion analysis data, this is complex 9 with a composition close to the ratio

Synthesis and HDAC inhibitory activity of pyrimidine-based hydroxamic acids

• Virginija Jakubkiene,
• Gabrielius Ernis Valiulis,
• Markus Schweipert,
• Asta Zubriene,
• Daumantas Matulis,
• Franz-Josef Meyer-Almes and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 837–844, doi:10.3762/bjoc.18.84

• methylene bridge linking the pyrimidine ring and the hydroxamic acid residue on the HDAC activity, hydroxamic acids 25–31 were synthesized (Scheme 2). In contrast to the synthesis of esters 3 and 4, alkylation of pyrimidinones 1 and 19 with the corresponding bromoesters in triethylamine in the presence of

• isoform inhibitory activity of compounds 12, 25, and 26 with that of compounds 27–29 suggests that the propyl substituent at the position 5 of the pyrimidine ring is favorable for this effect. Extension of the methylene bridge connecting the pyrimidine ring to the hydroxamic acid residue to the same

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• acids (BNA) Locked nucleic acids are a class of modified nucleosides which traditionally involve the incorporation of a methylene bridge between C4' and O2' of the ribose sugar (Figure 7A). This incorporation, as first reported by both Wengel and Obika, locks the nucleoside in the C3'-endo (north

• location of the methylene bridge to tailor the properties of these nucleosides. The incorporation of nitrogen at C2' has been explored for further functionalization while retaining the LNA scaffold. Singh et al. were the first to report the synthesis of C2'-amino-LNAs (Figure 7C) in 1998 [150], with the

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

• Savva A. Ponomarev,
• Roman V. Larkovich,
• Alexander S. Aldoshin,
• Andrey A. Tabolin,
• Sema L. Ioffe,
• Jonathan Groß,
• Till Opatz and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2021, 17, 283–292, doi:10.3762/bjoc.17.27

• 3 ppm) in the chemical shifts for some carbon atoms (Figure 2). A considerable difference in the chemical shifts was observed for C-7 of the methylene bridge (46.1 for the exo- vs 48.9 ppm for the endo-isomer), C-6 (51.3 for the exo vs 53.4 for the endo-isomer), C-4 (52.4 for the exo- vs 55.3 ppm

• dispersion effects are not included, whereas M062X includes nonlocal effects of electronic dispersion [70][75]. We also demonstrate the preparation of norbornene structures substituted at the methylene bridge. The reaction of model nitrostyrene 1h with spiro[2.4]hepta-4,6-diene was carried out (Scheme 2). As

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

• using dicarboxylic acids alongside EDC·HCl, HOBT and DMAP/DIPEA. This method was accompanied with a systematic decrease of the yield with the lengthening of the –CH2– methylene bridge. To counteract the decrease of yield a second approach was adapted for the larger receptors MC011–MC014. For this the

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• -methylbenzaldehyde). Bromofluorenecarbaldehyde 5 The synthetic route to azide-functionalized 7-bromofluorene-2-carbaldehyde 5 started from unfunctionalized fluorene. Double bromination to 14, followed by double methylation of the methylene bridge to 15 and a lithiation/formylation sequence afforded 7-bromofluorene-2

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• selective metalation can be achieved by varying reaction conditions and reagents. α-Lithiation of the methylene bridge and pyrazole ring in compound 77 allows for the synthesis of tris- and bis(pyrazole)phosphines. Antiñollo et al. [80] and Otero et al. [81] (Scheme 15) demonstrated the effect of varying

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• an ArCH2Ar methylene bridge between anti-oriented Ar rings. These data clearly indicate that calixarene-wheel 1 adopts the 1,2,3-alternate conformation in pseudorotaxane 2+11,2,3-alt (Figure 5 and Figure 6). A further inspection of the 1D and 2D (COSY-45 and HSQC) spectra of the 1:1 mixture of 1 and

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

• observation of cross-peaks between hydroxy protons 4 and the methylene bridge protons 5 and 5’, on the one hand, and the methylene protons 6–8 in the octyl chain (δ = 3.98, 3.18 and 2.04 ppm), on the other hand, is also in line with this conclusion. Thus, the 2D NMR data are completely consistent with the

C-5’-Triazolyl-2’-oxa-3’-aza-4’a-carbanucleosides: Synthesis and biological evaluation

• Roberto Romeo,
• Caterina Carnovale,
• Salvatore V. Giofrè,
• Maria A. Chiacchio,
• Adriana Garozzo,
• Emanuele Amata,
• Giovanni Romeo and
• Ugo Chiacchio

Beilstein J. Org. Chem. 2015, 11, 328–334, doi:10.3762/bjoc.11.38

• -carbanucleoside. However, in order to maintain the six-bond periodicity of the oligonucleotides and thus the flexibility of the oligonucleotide chain the methylene bridge at the pseudo-5’-position was retained. The obtained compounds have shown to be endowed with an interesting antitumor activity: most of them

Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics

• Léa Bouché,
• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 213–223, doi:10.3762/bjoc.10.17

• presence of a methylene bridge at the aminooxepane skeleton. The position of the methylene bridge was only determined for side product 27 using HMBC NMR spectroscopy which shows a small coupling between one proton of the methylene bridge and C-3 (position of the alcohol). We assume that they are formed by

Low-generation dendrimers with a calixarene core and based on a chiral C₂-symmetric pyrrolidine as iminosugar mimics

• Marco Marradi,
• Stefano Cicchi,
• Francesco Sansone,
• Alessandro Casnati and
• Andrea Goti

Beilstein J. Org. Chem. 2012, 8, 951–957, doi:10.3762/bjoc.8.107

• for the methylene bridge protons (filled circles in Figure 2), which are in line with previous observations but more difficult to be rationalised also as a consequence of a slight conformational rearrangement of the calixarene scaffold. Less important shifts are obviously observed for the pyrrolidine

• . The full spectra are reported in Supporting Information File 1 (Figure S1). Asterisks: aromatic protons; empty circles: OCH2CON protons; filled circles: methylene bridge protons. Schematic of the inclusion of alkali-metal ions (sodium and potassium) in the polar cavity defined by the acetamide

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• supramolecular chemistry, are 2,6-metacyclophanes with a methylene bridge between their phenolic groups, as shown in Figure 1 [1][2][3]. In 1994, the term “homocalixarene” was coined by Brodesser and Vögtle to describe analogues of calixarenes with two or more methylene groups between the aromatic moieties [4

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• was the first to observe norcaradiene (2) directly, by employing low-temperature photolysis, and an activation barrier of 11 ± 2 kcal·mol−1 was determined for the formation of 2 from 1, with the product being 4 kcal·mol−1 less stable [25]. Strong electron-withdrawing groups at the methylene bridge

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

• such a system, where two chromophores, stilbene and sydnone, are divided by a methylene bridge, an intramolecular 1,3-dipolar cycloaddition and the formation of diverse polycyclic compounds could be expected. Herein we describe, for the first time, the synthesis of cis- and trans-3-(stilbenylmethyl

Structural conditions required for the bridge lithiation and substitution of a basic calix[4]arene

• Conrad Fischer,
• Wilhelm Seichter and
• Edwin Weber

Beilstein J. Org. Chem. 2011, 7, 1602–1608, doi:10.3762/bjoc.7.188

• new monobridge-substituted calix[4]arenes were characterized with respect to their conformational behaviour in solution and the X-ray crystal structure of one key intermediate is taken into consideration. Keywords: calixarene; lithiation; methylene bridge; supramolecular chemistry; X-ray structure

• ; Introduction Besides the huge progress made in the modification of the upper- and lower-rim positions of basic calix[4]arenes such as 1 in Scheme 1, the substitution of at least one methylene bridge of the chalice opens up a perspective for the vertical expansion of the molecule [1][2]. Thus, during the past

• decade two main preparative routes for the methylene-bridge substitution of p-tert-butyltetramethoxycalix[4]arene have been established: A protocol described by Biali et al. yields a stabilized methylene carbocation through bromination that is ready for electrophilic substitution under SN1 conditions [3

Synthesis and properties of calix[4]arene telluropodant ethers as Ag⁺ selective sensors and Ag⁺, Hg²⁺ extractants

• Yang Lu,
• Yuanyuan Li,
• Song He,
• Yan Lu,
• Changying Liu,
• Xianshun Zeng and
• Langxing Chen

Beilstein J. Org. Chem. 2009, 5, No. 59, doi:10.3762/bjoc.5.59

• reflux temperature of ethanol–benzene (1:1, v/v). The structure and conformation of compounds 6–8 could be conveniently determined by their proton magnetic resonance spectra. As seen from 1H NMR data of 6–8, the methylene bridge protons of the calix skeleton appeared as two doublets at nearly 4.25 ppm

A stable enol from a 6-substituted benzanthrone and its unexpected behaviour under acidic conditions

• Marc Debeaux,
• Kai Brandhorst,
• Peter G. Jones,
• Henning Hopf,
• Jörg Grunenberg,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2009, 5, No. 31, doi:10.3762/bjoc.5.31

• . Compound 12 was characterised by NMR spectroscopy and mass spectrometry. The proton signals at δ = 2.61 and 2.84 ppm (400 MHz) with a geminal coupling constant of 13.5 Hz correspond to the protons of the methylene bridge. The bridgehead protons arise as a multiplet at 4.70–4.76 ppm. NMR data of the

Electronic differentiation competes with transition state sensitivity in palladium- catalyzed allylic substitutions

• Dominik A. Lange and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2007, 3, No. 36, doi:10.1186/1860-5397-3-36

• of phosphabenzene (X) and pyridine (Y) units tune electronic characteristics of P,N-ligand models in Pd-catalyzed allylic substitutions (Scheme 1). The phosphabenzene and pyridine moieties are linked via Car-Car bonds and a methylene bridge retains planarity and limits conformational flexibility