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Search for "six-membered rings" in Full Text gives 71 result(s) in Beilstein Journal of Organic Chemistry.

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

Graphical Abstract
  • : asymmetric organocatalysis; axial chirality; biaryls; hydrogen bond; oxo-Diels–Alder reaction; Introduction The Diels–Alder (DA) reaction is a useful and easy-to-perform method for the synthesis of six-membered rings through the direct formation of C–C bonds between a diene and a dienophile (a substituted
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Published 18 Apr 2019

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines

  • Laize A. F. Andrade,
  • Lucas A. Zeoly,
  • Rodrigo A. Cormanich and
  • Matheus P. Freitas

Beilstein J. Org. Chem. 2019, 15, 506–512, doi:10.3762/bjoc.15.44

Graphical Abstract
  • manifests in six-membered rings when 1JC–Hax < 1JC–Heq [8][9]. A similar effect on 1JC–F has been observed on fluorinated six-membered rings and then called the (reverse) fluorine Perlin-like effect [10]. Despite some controversies on the origin of such effects [11][12][13][14], the anomeric-like
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Published 20 Feb 2019

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

  • Sibylle Frei,
  • Adam K. Katolik and
  • Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

Graphical Abstract
  • obtained crystal structure of derivative 6 (Table S1, Supporting Information File 1). The reason for that can be attributed to the different conformations of the six-membered rings in these two structures. Apart from that, the two structures were very similar. Synthesis of the modified oligonucleotides and
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Published 08 Jan 2019

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

  • Christiane Schultze and
  • Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

Graphical Abstract
  • which a heterocycle is annellated to the benzene ring of the coumarin skeleton. In particular the latter group is often further divided into sections according to ring size (five-membered rings: furanocoumarins; six-membered rings: pyranocoumarins) and location of the annellated ring (linear vs angular
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Published 05 Dec 2018

Oxidative and reductive cyclization in stiff dithienylethenes

  • Michael Kleinwächter,
  • Ellen Teichmann,
  • Lutz Grubert,
  • Martin Herder and
  • Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

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  • Cyclization by anodic oxidation In initial experiments, the electrochemical behavior of the methyl-substituted derivative bearing six-membered rings (sDTE66-Me) was investigated. For both configurational isomers, i.e., E- and Z-sDTE66-Me, an irreversible oxidation wave corresponding to the transfer of two
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Published 09 Nov 2018

Chiral bisoxazoline ligands designed to stabilize bimetallic complexes

  • Deepankar Das,
  • Rudrajit Mal,
  • Nisha Mittal,
  • Zhengbo Zhu,
  • Thomas J. Emge and
  • Daniel Seidel

Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175

Graphical Abstract
  • to form a five-membered metallacycle, subtending N(2)–Ni(1)–N(3) and N(5)–Ni(2)–N(6) angles of 81.53° and 80.34°, respectively. Additionally, the nitrogen atoms on the oxazoline and amide moieties form six-membered rings with the nickel(ΙΙ) center with N(1)–Ni(1)–N(2) and N(4)–Ni(2)–N(5) angles of
  • °, respectively. The coordination of the nitrogen atoms on oxazoline and amide moieties with the two zinc centers forms six-membered rings with N(3)–Zn(1)–N(2) and N(6)–Zn(2)–N(5) angles of 87.05° and 88.55°, respectively. All of the Zn–N distances are within 2.023–2.177 Å, as expected for such complexes
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Published 01 Aug 2018

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

  • James R. Vyvyan,
  • Courtney A. Engles,
  • Scott L. Bray,
  • Erik D. Wold,
  • Christopher L. Porter and
  • Mikhail O. Konev

Beilstein J. Org. Chem. 2017, 13, 2122–2127, doi:10.3762/bjoc.13.209

Graphical Abstract
  • with similar intramolecular etherifications to make five- and six-membered rings [40], and our own preparation of an analogous seven-membered cyclic ether [41], we examined Pd(0) catalyst precursors with the Q-Phos ligand. The reaction with Pd(dba)2 with Q-Phos and sodium tert-butoxide produced cyclic
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Published 11 Oct 2017

Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

  • Serge Pérez and
  • Daniele de Sanctis

Beilstein J. Org. Chem. 2017, 13, 1145–1167, doi:10.3762/bjoc.13.114

Graphical Abstract
  • and six membered rings, anomeric mixture, etc.). It is also true that much less effort has been devoted to the production of organic crystals of medium sized biomolecules compared to biological macromolecules. Nevertheless, in many instances, ordered samples may be obtained, either in the form of
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Published 14 Jun 2017

Synthesis of 1-indanones with a broad range of biological activity

  • Marika Turek,
  • Dorota Szczęsna,
  • Marek Koprowski and
  • Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

Graphical Abstract
  • precursor of the benzene ring (Scheme 87). This methodology has been applied in the synthesis of 1-indanones (Scheme 88 and Scheme 89). In 2012, Hoye et al. have presented the synthesis of 1-indenone 318 via a hexadehydro-Diels–Alder (HDDA) reaction with simultaneous formation of five and six-membered rings
  • from the tetrayne 317 (Scheme 88) [119]. In the reaction participates only three triple bonds marked by red lines. This, catalyzed by MnO2 reaction, is fully regioselective. During the cycloaddition after the formation of the five and six-membered rings, one of the tert-butyldimethylsilyl (TBS) group
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Published 09 Mar 2017

Continuous N-alkylation reactions of amino alcohols using γ-Al2O3 and supercritical CO2: unexpected formation of cyclic ureas and urethanes by reaction with CO2

  • Emilia S. Streng,
  • Darren S. Lee,
  • Michael W. George and
  • Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

Graphical Abstract
  • be expected from the intramolecular closure of 8, consistent with the results observed with bromoalkylamines [48], and suggesting the rate of closure for three-membered rings is slower than that of five- and six-membered rings. We cannot rule out the formation of aziridine as an intermediate in the
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Published 21 Feb 2017

Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation

  • Michał Malik and
  • Sławomir Jarosz

Beilstein J. Org. Chem. 2016, 12, 2602–2608, doi:10.3762/bjoc.12.255

Graphical Abstract
  • (both in 25 and 26). This is in accordance with the general observation, that E-enolates (enolates in six-membered rings are always E) give predominantly the anti-products in aldol reactions (Zimmerman–Traxler model) [52][53][54]. The application of the above-described procedure to cyclohexenone 18 was
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Published 01 Dec 2016

β-Amino functionalization of cinnamic Weinreb amides in ionic liquid

  • Yi-Ning Wang,
  • Guo-Xiang Sun and
  • Gang Qi

Beilstein J. Org. Chem. 2016, 12, 2372–2377, doi:10.3762/bjoc.12.231

Graphical Abstract
  • much lower fields (e.g., 8.25 ppm vs 6.33 ppm for compounds 6a-B vs 6a-A). The reason for this phenomenon is probably due to hydrogen bonding between the protons of the nitrobenzenesulfonyl amines and the neighboring carbonyl groups, which form stable six-membered rings as shown in Figure 1. In
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Published 11 Nov 2016

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

  • Mariano Goldberg,
  • Denis Sartakov,
  • Jan W. Bats,
  • Michael Bolte and
  • Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

Graphical Abstract
  • of the guanidinium benzoate salt the six membered rings of 10 adopt conformations close to an envelope with the phenyl substituents in pseudo-axial positions. The unprotonated guanidine 10 catalyzes Diels–Alder reactions of anthrones and maleimides (25–30% ee). It also promotes as a strong Brønsted
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Published 19 Aug 2016

The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

  • Sonia L. Repetto,
  • James F. Costello,
  • Craig P. Butts,
  • Joseph K. W. Lam and
  • Norman M. Ratcliffe

Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143

Graphical Abstract
  • -diethoxypropane) is several orders of magnitude greater than 1 [18]. Relative reactivity of cyclic orthoesters; five versus six-membered rings As k1 ≈ kobs in the pH range examined here (Scheme 1), factors associated with the relief of cyclic strain cannot be used to account for the difference observed for five
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Published 15 Jul 2016

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

  • Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

Graphical Abstract
  • six-membered rings and only four articles described the synthesis of three and seven-membered heterocycles. Additionally, the majority of the reported syntheses were devoted to the development of new methodologies including the use of advanced catalytic systems, alternative solvents and microwave
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Published 21 Jun 2016

Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

  • Jakub Saadi,
  • Christoph Bentz,
  • Kai Redies,
  • Dieter Lentz,
  • Reinhold Zimmer and
  • Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

Graphical Abstract
  • not allow an unambiguous determination. Considering the result obtained with the cycloheptanone derivative where two diastereomers could be assigned by X-ray crystal structure analyses make the proposed trans-annulation of the five- and six-membered rings fairly likely. The palladium-catalyzed
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Published 16 Jun 2016

Separation and identification of indene–C70 bisadduct isomers

  • Bolong Zhang,
  • Jegadesan Subbiah,
  • David J. Jones and
  • Wallace W. H. Wong

Beilstein J. Org. Chem. 2016, 12, 903–911, doi:10.3762/bjoc.12.88

Graphical Abstract
  • between C70 and two isoindene molecules generated in situ from indene. The symmetry of the ellipsoidal C70 molecule means that there are four different bonds between two six membered rings ([6,6]-bonds) that can participate in the Diel–Alder reaction. These are known as α-, β-, ε- and κ-bonds (Figure 2a
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Published 06 May 2016

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

  • Giorgos Koutoulogenis,
  • Nikolaos Kaplaneris and
  • Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

Graphical Abstract
  • main tools a synthetic chemist has to perform asymmetric catalysis. In this review the synthesis of six-membered rings, that contain multiple chiral centers, either by a ring closing process or by a functionalization reaction on an already existing six-membered ring, utilizing bifunctional (thio)ureas
  • )ureas have been synthesized in order to utilize both hydrogen bonding interactions and enamine formation. In the last 10 years the field has witnessed the development of some new activation modes, such as SOMO catalysis [8] and photoredox organocatalysis [9]. Six-membered rings are found in many natural
  • products, pharmaceuticals and agrochemicals, thus, a lot of effort has been put by the synthetic community to provide mild, reliable, robust and operationally simple methods to construct them. Of the vast variety of six-membered rings, those with multiple chiral centers pose the most difficult synthetic
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Published 10 Mar 2016

Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

  • Cesar Garcias-Morales,
  • David Ortegón-Reyna and
  • Armando Ariza-Castolo

Beilstein J. Org. Chem. 2015, 11, 1973–1984, doi:10.3762/bjoc.11.213

Graphical Abstract
  • .11.213 Abstract This paper reports the synthesis of a series of piperidones 1–8 by the Mannich reaction and analysis of their structures and conformations in solution by NMR and mass spectrometry. The six-membered rings in 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones, compounds 1 and 2, adopt
  • , and C2, respectively. A signal corresponding to the carbonyl carbon is located at 211.66 ppm. Figure 5a shows the conformations of 1, determined by the t-ROESY experiment. In solution, one of the six-membered rings is in the chair conformation, while the second is in the boat conformation to prevent
  • Karplus curve [60]. For 4–8, the six-membered rings exhibit the chair–chair conformation, with both of the phenyl rings in equatorial positions. For 1 and 2, the six-membered rings exhibit the chair–boat conformation, because one nitrogen atom is substituted by a methyl group. As a result, LPE repulsion
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Published 22 Oct 2015

The preparation of new functionalized [2.2]paracyclophane derivatives with N-containing functional groups

  • Henning Hopf,
  • Swaminathan Vijay Narayanan and
  • Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 437–445, doi:10.3762/bjoc.11.50

Graphical Abstract
  • cyclophane strain include the following. The bridge C–C single bonds are lengthened to 1.58–1.60 Å, the bridge sp3-bond angles are widened to ca. 112°, and the bridgehead angles within the six-membered rings are narrowed to 116–118°. These rings display a flattened boat conformation (deviations of bridgehead
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Published 07 Apr 2015

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

  • Pablo Wessig,
  • Roswitha Merkel and
  • Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

Graphical Abstract
  • based on spirocyclically joined saturated six-membered rings [8]. The key step of the synthesis of these rods is the formation of ketals and we therefore name this class of compounds oligospiroketals (OSKs). Although the backbone of OSK rods contains many oxygen atoms, these atoms are shielded by
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Published 16 Jan 2015

Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

  • Henning Hopf,
  • Swaminathan Vijay Narayanan and
  • Peter G. Jones

Beilstein J. Org. Chem. 2014, 10, 2021–2026, doi:10.3762/bjoc.10.210

Graphical Abstract
  • bridge angles and narrowed sp2 ring angles at the bridgehead atoms, and boat-shaped six-membered rings with the bridgehead atoms lying out of the plane of the other four atoms (see Table 2 below). The crystal packing involves two classical and three "weak" hydrogen bonds (two involving the
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Published 28 Aug 2014

Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C36H12 open geodesic polyarene

  • Hee Yeon Cho,
  • Ronald B. M. Ansems and
  • Lawrence T. Scott

Beilstein J. Org. Chem. 2014, 10, 956–968, doi:10.3762/bjoc.10.94

Graphical Abstract
  • fullerenes [53]. The carbon–carbon bond shared by two six-membered rings (so-called 6:6-bonds: 1.379 Å) are shorter than those shared by a 5-membered ring and a 6-membered ring (5:6-bonds: 1.430 Å). That is, the carbon–carbon bonds of the hexagonal ring in the center of circumtrindene are not the same as
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Published 28 Apr 2014

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

  • Gijs Koopmanschap,
  • Eelco Ruijter and
  • Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

Graphical Abstract
  • ease of preparation via IMCRs [27][28][29]. First, the β-lactams will be described followed by five-membered rings varying from pyrrolidines to tetrazoles based amide bond isosteres. Examples of the six-membered rings showing peptide like-properties are the piperazines, homoprolines, dihydropyrimidones
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Published 04 Mar 2014

Cyclic phosphonium ionic liquids

  • Sharon I. Lall-Ramnarine,
  • Joshua A. Mukhlall,
  • James F. Wishart,
  • Robert R. Engel,
  • Alicia R. Romeo,
  • Masao Gohdo,
  • Sharon Ramati,
  • Marc Berman and
  • Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

Graphical Abstract
  • ammonium salt (101 cP vs 75 cP at 25 °C). For the six-membered rings the phosphonium IL C4mPphin NTf2 5b is slightly less viscous than C4mPip NTf2 (butylmethylpiperidinium NTf2), 171 cP vs 183 cP. Interestingly, the cyclic cations do not follow the common trend among the quaternary tetra-n-alkylated
  • cations have greater thermal stability than the ammonium ones. One trend observed for both cation types is that the ILs with five-membered rings have greater thermal stability than those with six-membered rings. Further work will be required to determine if the observed TGA behaviors are due to actual
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Published 24 Jan 2014
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