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

Stereoselectively fluorinated N-heterocycles: a brief survey

  • Xiang-Guo Hu and
  • Luke Hunter

Beilstein J. Org. Chem. 2013, 9, 2696–2708, doi:10.3762/bjoc.9.306

Graphical Abstract
  • increased ridigity was credited with a dramatic improvement in the enantioselectivity. 3.3 Six-membered rings The conformational analysis of six-membered rings is a cornerstone in physical chemistry. Substituted saturated six-membered compounds usually adopt a chair conformation with substituents preferring
  • and Snyder were also able to rule out hydrogen bonding as the source of the axial preference, since the N,N-dimethyl analogue 20 exhibited a similar effect. 3.4 Seven-membered rings Seven-membered rings exhibit much more complex conformational behaviour than six-membered rings. Hence, it is perhaps
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Published 29 Nov 2013

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

  • Mikko Passiniemi and
  • Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

Graphical Abstract
  • six-membered rings. Five-membered dihydrofuran rings lead to the synthesis of furanomycin D [35][36], norfuranomycin E [37], and the polyoxin family F [38]. The six-membered tetrahydropyridine G synthesized via this route can be used as an intermediate in the synthesis of iminosugars, e.g., of the
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Published 26 Nov 2013

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

  • Marcus Baumann and
  • Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

Graphical Abstract
  • published review on five-membered rings, will form a comprehensive foundation and reference source for individuals interested in medicinal, synthetic and preparative chemistry. Keywords: heterocycles; medicinal chemistry; pharmaceuticals; six-membered rings; synthesis; Introduction The commonality of six
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Published 30 Oct 2013

The preparation of several 1,2,3,4,5-functionalized cyclopentane derivatives

  • André S. Kelch,
  • Peter G. Jones,
  • Ina Dix and
  • Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 1705–1712, doi:10.3762/bjoc.9.195

Graphical Abstract
  • reason is probably the practical consideration that there are more and higher-yielding preparative routes to three-, four- and six-membered rings than to five-membered ones. Looking at possible precursors for 3, it seems reasonable to start with a substrate that contains at least a complete five-membered
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Published 19 Aug 2013

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

  • František Josefík,
  • Markéta Svobodová,
  • Valerio Bertolasi and
  • Petr Šimůnek

Beilstein J. Org. Chem. 2013, 9, 1463–1471, doi:10.3762/bjoc.9.166

Graphical Abstract
  • others are given in Supporting Information File 1. Almost all the structures display some disorder. Structures 5d, 5f, 5j and 5l show disorder in the C3–C7,N3 six-membered rings and the C5H2 moieties were refined over two sites. All the BF4− anions exhibit high temperature factors; in 5d and 5l the
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Published 23 Jul 2013

α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions

  • Åsmund Kaupang and
  • Tore Bonge-Hansen

Beilstein J. Org. Chem. 2013, 9, 1407–1413, doi:10.3762/bjoc.9.157

Graphical Abstract
  • (Table 1, entries 1–3, products 5a–c), whereas among the derivatives bearing 1,4-heterosubstituted six-membered rings as side chains, poorer yields are obtained (Table 1, entries 4–6, products 5d–f). The latter result could possibly be viewed as an expression of the deactivation of the C–H bonds β to the
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Published 11 Jul 2013

Selective copper(II) acetate and potassium iodide catalyzed oxidation of aminals to dihydroquinazoline and quinazolinone alkaloids

  • Matthew T. Richers,
  • Chenfei Zhao and
  • Daniel Seidel

Beilstein J. Org. Chem. 2013, 9, 1194–1201, doi:10.3762/bjoc.9.135

Graphical Abstract
  • pyrrolidine-containing aminal adopts a bent structure, whereas the piperidine aminal appears relatively strain-free [34]), this finding likely relates to the reduced propensity of six-membered rings to engage in reactions that form exocyclic double bonds. The isolation of azepinoquinazoline 12 in 73% yield
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Published 20 Jun 2013

Polymerization of novel methacrylated anthraquinone dyes

  • Christian Dollendorf,
  • Susanne Katharina Kreth,
  • Soo Whan Choi and
  • Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 453–459, doi:10.3762/bjoc.9.48

Graphical Abstract
  • -products derived from ring-closure reactions were only found when aliphatic amines with two carbon units between the amine and hydroxy functionality were used. In the synthesis of green and blue dyes, aromatic amines that cannot build six-membered rings were utilized. However, the ring-closure can be
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Published 28 Feb 2013

Inter- and intramolecular enantioselective carbolithiation reactions

  • Asier Gómez-SanJuan,
  • Nuria Sotomayor and
  • Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

Graphical Abstract
  • formation of six-membered rings, though the slow cyclization rate results in racemization. The use of a phenylthio-substituted alkene favors the cyclization, and the faster reaction rate results in an improved optical purity of the indolizidines 35 and 36, though with moderate diastereo- and
  • ethers. Formation of six-membered rings: pyrroloisoquinolines. Formation of six-membered rings: tetrahydroquinolines. Acknowledgements We wish to thank the Ministerio de Ciencia e Innovación (CTQ2009-07733) and Universidad del País Vasco/Euskal Herriko Unibertsitatea (UFI11/22, GIU 0946) for their
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Published 13 Feb 2013

The chemistry of bisallenes

  • Henning Hopf and
  • Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

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Published 15 Nov 2012

Asymmetric Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene

  • Magnus Rueping and
  • Sadiya Raja

Beilstein J. Org. Chem. 2012, 8, 1819–1824, doi:10.3762/bjoc.8.208

Graphical Abstract
  • construction of optically active, nitrogen-containing, six-membered rings, such as tetrahydroquinolines and piperidines. N-heterocycles are found in a wide range of natural products and many biologically active compounds [1][2][3][4]. To date, most aza-asymmetric Diels–Alder reactions have been catalyzed by
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Published 23 Oct 2012

Evaluation of a chiral cubane-based Schiff base ligand in asymmetric catalysis reactions

  • Kyle F. Biegasiewicz,
  • Michelle L. Ingalsbe,
  • Jeffrey D. St. Denis,
  • James L. Gleason,
  • Junming Ho,
  • Michelle L. Coote,
  • G. Paul Savage and
  • Ronny Priefer

Beilstein J. Org. Chem. 2012, 8, 1814–1818, doi:10.3762/bjoc.8.207

Graphical Abstract
  • are well within the required H-bonding length of <3.2 Å [31]. In addition, the C…Cu lengths of 2.85 and 3.03 Å with M06L and B3LYP, respectively, were well within the required 4.0 Å limit [31]. This produces pseudo six-membered rings having a C–H…Cu bond angle of 125.1° or 122.9° with M06L and B3LYP
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Published 22 Oct 2012

Highly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions

  • Stefan Bräse,
  • Nicole Volz,
  • Franziska Gläser and
  • Martin Nieger

Beilstein J. Org. Chem. 2012, 8, 1385–1392, doi:10.3762/bjoc.8.160

Graphical Abstract
  • published total synthesis of Taxol (2) by Nicolaou. Two different [4 + 2]-cycloaddition reactions were applied to set up each of the two six-membered rings of the target molecule [9][10]. As a final example, Dynemicin A (3) should be mentioned, which is an enediyne consisting of a complex heterocyclic
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Published 28 Aug 2012

Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols

  • Fátima M. P. de Rezende,
  • Marilua A. Moreira,
  • Rodrigo A. Cormanich and
  • Matheus P. Freitas

Beilstein J. Org. Chem. 2012, 8, 1227–1232, doi:10.3762/bjoc.8.137

Graphical Abstract
  • an interaction. Intramolecular interactions between vicinal F and OH groups have already been investigated in cyclic compounds (including aromatic rings) [4], and the present study extends such analysis to aliphatic compounds capable of forming six-membered rings through hydrogen bonding. Results and
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Published 02 Aug 2012

Synthesis of 2,6-disubstituted tetrahydroazulene derivatives

  • Zakir Hussain,
  • Henning Hopf,
  • Khurshid Ayub and
  • S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 693–698, doi:10.3762/bjoc.8.77

Graphical Abstract
  • rings are approximately coplanar, but the three- and six-membered rings form an interplanar angle of 78.4(1)°. The atoms of the ester side chain are coplanar and this plane forms a dihedral angle of 78.73(4)° with the central ring. In the crystal, the molecules form hydrogen-bonded dimers across
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Published 04 May 2012

Efficient gold(I)/silver(I)-cocatalyzed cascade intermolecular N-Michael addition/intramolecular hydroalkylation of unactivated alkenes with α-ketones

  • Ya-Ping Xiao,
  • Xin-Yuan Liu and
  • Chi-Ming Che

Beilstein J. Org. Chem. 2011, 7, 1100–1107, doi:10.3762/bjoc.7.126

Graphical Abstract
  • ) complexes can efficiently catalyze direct intramolecular hydroalkylation of unactivated alkenes with α-ketones, via the exo-trig cyclization, to build a variety of new five- and six-membered rings [24]. However, all of the substrates examined in this gold(I)-catalyzed reaction were prepared and isolated
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Published 11 Aug 2011

Long-range diastereoselectivity in Ugi reactions of 2-substituted dihydrobenzoxazepines

  • Luca Banfi,
  • Andrea Basso,
  • Valentina Cerulli,
  • Valeria Rocca and
  • Renata Riva

Beilstein J. Org. Chem. 2011, 7, 976–979, doi:10.3762/bjoc.7.109

Graphical Abstract
  • proved unambiguously the relative configuration of the major adducts. Some authors have suggested, for six membered rings, a preferential axial attack of the isocyanide [14][16], since it relieves unfavorable steric strain in the forming tetrahedric adduct (Scheme 2). In our case, equatorial attack
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Published 13 Jul 2011

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

  • Henning Hopf,
  • Vitaly Raev and
  • Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

Graphical Abstract
  • X-ray analysis (Figure 2). Molecules of 13 and 15 show common structural features. Despite the introduction of the new bridge C17–C24, the form of the original [2.2]paracyclophane is maintained to a considerable extent, with a flattened boat conformation of both six-membered rings (C4,5,7,8 and
  • the four-membered rings, the bond lengths C18–23 relax to 1.563(2) and 1.559(2) Å. The interplanar angles between the six-membered rings of the original [2.2]paracyclophane unit are 12.9 and 12.7°. These results clearly show that the photocylization occurs from the conformation in which the two pseudo
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Published 24 May 2011

Synthesis of chiral cyclohexanes and carbasugars by 6-exo-dig radical cyclisation reactions

  • Rajeev K. Shrivastava,
  • Elise Maudru,
  • Gurdial Singh,
  • Richard H. Wightman and
  • Keith M. Morgan

Beilstein J. Org. Chem. 2008, 4, No. 43, doi:10.3762/bjoc.4.43

Graphical Abstract
  • closure of a radical onto an alkyne [14]. In contrast there are fewer reports of the corresponding 6-exo-dig cyclisation to prepare fully functionalised cyclohexanes and carbasugars. The reason for this may be inferred from the observation that the formation of six-membered rings by a radical ring closure
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Published 19 Nov 2008

The tert- amino effect in heterocyclic chemistry: Synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives

  • Dipak Prajapati and
  • Kalyan Jyoti Borah

Beilstein J. Org. Chem. 2007, 3, No. 43, doi:10.1186/1860-5397-3-43

Graphical Abstract
  • ortho-substituted tertiary anilines, especially when ortho-vinyl-substituted anilines have been employed. In general, the ring-closure process leads to five and six membered rings. [9][10][11] Ring closure of ortho-substituted N,N-dialkylaniline derivatives can proceed in three different ways, depending
  • third path (c) involved an analogous reaction of methylene groups and atom B which lead to the formation of six-membered rings. The first reaction of this type was reported in 1895 by Pinnow.[12] Most of the early examples of the reaction of compounds with an unsaturated ortho-substituent involve groups
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Published 12 Dec 2007

Crystal engineering of analogous and homologous organic compounds: hydrogen bonding patterns in trimethoprim hydrogen phthalate and trimethoprim hydrogen adipate

  • Packianathan Thomas Muthiah,
  • Savarimuthu Francis,
  • Urszula Rychlewska and
  • Beata Warżajtis

Beilstein J. Org. Chem. 2006, 2, No. 8, doi:10.1186/1860-5397-2-8

Graphical Abstract
  • substituted phenyl and pyrimidine six-membered rings are free to rotate. An arbitrary conformation of this molecule can be described by the torsion angles of the two rings to the frame. We define these torsion angles as C4-C5-C7-C8 and C5-C7-C8-C9, i.e. with respect to one of the rings the other can rotate
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Published 07 Apr 2006
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