Search results

Search for "[4 2] cycloaddition" in Full Text gives 92 result(s) in Beilstein Journal of Organic Chemistry.

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
  • ranged from 1:2 to 2:3 with a preference to 310a–315a regioisomers. An interesting approach to the synthesis of 1-indanones and 1-indenones is based on the hexadehydro-Diels–Alder (HDDA) reaction in which an alkyne reacts in the [4 + 2] cycloaddition with diyne and forms a reactive benzyne species as a
PDF
Album
Review
Published 09 Mar 2017
Graphical Abstract
  • thorough literature search using Reaxys indicates that cyclohexanone has been made by [5 + 1] and [4 + 2] cycloaddition strategies thus validating the patterns of assembly shown in the third and fourth entries of Scheme 1 and the fourth entry of Scheme 2. The [5 + 1] literature examples involved insertion
PDF
Album
Supp Info
Full Research Paper
Published 16 Nov 2016

Highly chemo-, enantio-, and diastereoselective [4 + 2] cycloaddition of 5H-thiazol-4-ones with N-itaconimides

  • Shuai Qiu,
  • Choon-Hong Tan and
  • Zhiyong Jiang

Beilstein J. Org. Chem. 2016, 12, 2293–2297, doi:10.3762/bjoc.12.222

Graphical Abstract
  • chemoselectivity and excellent yield of 98% (Table 1, entry 10). With the optimal reaction conditions in hand, we examined the substrate scope of the enantioselective [4 + 2] cycloaddition between 5H-thiazol-4-ones 1 and N-itaconimides 2, catalyzed by DP-UAA V (Scheme 1). Firstly, with 1a as the model 5H-thiazol-4
  • decreases the free energy of the second formal Mannich reaction, thus improving the reaction rate and chemoselectivity of the [4 + 2] cycloaddition. To extend the usefulness of this reaction, we demonstrate that the adduct can be efficiently reduced with borane. As shown in Scheme 2, 3a was readily reduced
PDF
Album
Supp Info
Full Research Paper
Published 01 Nov 2016

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

  • Lucie Brulíková,
  • Aidan Harrison,
  • Marvin J. Miller and
  • Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

Graphical Abstract
  • , requiring a detailed examination of the kinetic versus thermodynamic effects. The nitroso hetero-Diels–Alder reaction involves the formation of the 3,6-dihydro-2H-1,2-oxazine scaffold 3 from nitroso dienophiles 1 and dienes 2 in a [4 + 2] cycloaddition reaction (Scheme 1). The first nitroso hetero-Diels
PDF
Album
Review
Published 01 Sep 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
  • the Michael products [19] which are the dominant products in polar solvents [25]. Previous mechanistic studies by Koerner and Rickborn [25] have collected strong arguments for a fast concerted [4 + 2]-cycloaddition of the deprotonated anthrone. Michael products were shown to be secondary products of a
PDF
Album
Supp Info
Full Research Paper
Published 19 Aug 2016

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

  • Franziska Hemmerling and
  • Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

Graphical Abstract
  • ) or versipelostatin A (153) result from formal [4 + 2] cycloaddition reactions between exo-methylene groups and conjugated dienes. The required exo-methylene groups are installed by formal dehydration of 5-hydroxymethyltetronates. Leadlay et al. have confirmed that the respective reaction in
  • analogous acetylation–elimination process was experimentally confirmed for quartromicin D1 (151) biosynthesis (Scheme 22) [145]. VstJ has been identified as a probable candidate for the enzyme-catalysed [4 + 2] cycloaddition in versipelostatin A (153) biosynthesis by heterologous expression, gene knockout
  • the fact that four [4 + 2] cycloaddition events need to take place to assemble the four monomers into the highly symmetrical natural product [147]. Thiotetronates. Recently, Leadlay et al. presented their findings on the biosynthesis of thiotetronate antibiotics (Scheme 24) [148]. These small
PDF
Album
Review
Published 20 Jul 2016

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

  • Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

Graphical Abstract
  • , dehydropiperidine or piperidine is consistent with a [4 + 2] cycloaddition across two dehydrated serine residues [79][80]. Genetic disruption of tclM from the thiocillin pathway showed that TclM was responsible for this transformation [81], although the precise cyclisation mechanism (concerted or stepwise) could
PDF
Album
Review
Published 20 Jun 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
  • catalyzed by the bifunctional urea 127 (Scheme 41) [61]. The transformation follows a Michael–Michael mechanism and is considered a formal [4 + 2] cycloaddition of 128 (bearing a nucleophilic carbon as well as an electrophilic carbon) and protected methylene-indolinones 129. A wide range of substrates were
PDF
Album
Review
Published 10 Mar 2016

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

  • Laura A. Bryant,
  • Rossana Fanelli and
  • Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

Graphical Abstract
  • role of the 6’-OH functionality is shown to be critical in the orchestration of the reaction process, as depicted in the proposed transition state model (Scheme 20). Cycloadditions The [4 + 2] cycloaddition of benzofuran-2(3H)-one derivatives 84 with methyl allenoate 85 to give the corresponding
PDF
Album
Review
Published 07 Mar 2016

Synthesis of constrained analogues of tryptophan

  • Elisabetta Rossi,
  • Valentina Pirovano,
  • Marco Negrato,
  • Giorgio Abbiati and
  • Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

Graphical Abstract
  • -catalysed diastereoselective [4 + 2] cycloaddition of vinylindoles and methyl 2-acetamidoacrylate, leading to methyl 3-acetamido-1,2,3,4-tetrahydrocarbazole-3-carboxylate derivatives, is described. Treatment of the obtained cycloadducts under hydrolytic conditions results in the preparation of a small
  • -3-carboxylic acid derivatives 3, constrained analogues of tryptophan, could be synthesized by Diels–Alder reactions between 2-vinylindoles 1 [22] as dienes and methyl 2-acetamidoacrylate (dehydroalanine) 2 [23] as dienophile (Scheme 1). Reported [4 + 2] cycloaddition reactions of methyl 2
  • the complete deprotection of the cycloadducts in order to obtain the free amino acid function. Results 2-Vinylindole 1a was selected as a benchmark substrate to evaluate the feasibility of the devised [4 + 2] cycloaddition reaction with methyl 2-acetamidoacrylate (2). Test conditions and obtained
PDF
Album
Supp Info
Full Research Paper
Published 27 Oct 2015

Recent applications of ring-rearrangement metathesis in organic synthesis

  • Sambasivarao Kotha,
  • Milind Meshram,
  • Priti Khedkar,
  • Shaibal Banerjee and
  • Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

Graphical Abstract
  • , heteroaryl, and alkyl, etc. to produce α,β-unsaturated acylimidazolidinones 215. Next, the Evan’s asymmetric DA methodology involving a [4 + 2] cycloaddition of chiral bis(oxazoline) in the presence of Cu(OTf)2 was employed to furnish the required norbornene system 216. Later, it was converted into a lactam
PDF
Album
Review
Published 07 Oct 2015

Selected synthetic strategies to cyclophanes

  • Sambasivarao Kotha,
  • Mukesh E. Shirbhate and
  • Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

Graphical Abstract
  • nitrate (40%, Scheme 56). Intramolecular Diels–Alder (DA) reaction: Suwa and co-workers [192] have synthesized the muscopyridine by a [4 + 2] cycloaddition of the bisketene 325. The condensation of acid dichloride derived from 323 with two molecules of Meldrum’s acid gave 324 which on thermal activation
  • muscopyridine (73, 89%). [4 + 2] Cycloaddition (Diels–Alder reaction): In 2003, Tochtermann and co-workers [193] have synthesized a bis[10]paracyclophane with two chiral planes and one chiral axis via the DA reaction as a key step. The bifuran derivative 331 was subjected to a DA sequence with dimethyl
PDF
Album
Review
Published 29 Jul 2015

Enhancing the reactivity of 1,2-diphospholes in cycloaddition reactions

  • Almaz Zagidullin,
  • Vasili Miluykov,
  • Elena Oshchepkova,
  • Artem Tufatullin,
  • Olga Kataeva and
  • Oleg Sinyashin

Beilstein J. Org. Chem. 2015, 11, 169–173, doi:10.3762/bjoc.11.17

Graphical Abstract
  • (R = CN, COOEt, OMe, CH2OEt) results in corresponding 1-alkyl-3,4,5-triphenyl-1,2-diphospholes (alkyl = CH2CN (1a), CH2COOEt (1b), CH2OMe (1c), and (CH2)2OEt (1d)), which spontaneously undergo the intermolecular [4 + 2] cycloaddition reactions at room temperature to form the mixture of the
  • -4,7-(ethylphosphinidene)indene (2e) only upon heating up to 60 °C. With further heating to 120 °C with N-phenylmaleimide, the cycloadducts 2a–c and 2e undergo the retro-Diels–Alder reaction and form only one product of the [4 + 2] cycloaddition reaction 3a–с, 3e with good yields up to 65%. Keywords
  • at room temperature for a few hours. 1,2-Diphosphole 1d is more stable and no cycloaddition was observed upon heating in toluene. Upon standing, the diphospholes 1a–c undergo spontaneous [4 + 2] cycloaddition reactions leading to a mixture of cycloadducts (Scheme 2). The 31P NMR spectra of the
PDF
Album
Supp Info
Full Research Paper
Published 27 Jan 2015

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

  • Alan M. Jones and
  • Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

Graphical Abstract
  • also been prepared using the anodic oxidation route. Possibly, one of the most important uses of the Shono oxidation has been in the development of the [4 + 2] cycloaddition, more commonly known as the Diels–Alder reaction for the controlled preparation of N-acyliminium ions to react with dienophiles
PDF
Album
Review
Published 18 Dec 2014

Design and synthesis of novel bis-annulated caged polycycles via ring-closing metathesis: pushpakenediol

  • Sambasivarao Kotha and
  • Mirtunjay Kumar Dipak

Beilstein J. Org. Chem. 2014, 10, 2664–2670, doi:10.3762/bjoc.10.280

Graphical Abstract
  • the corresponding 2,5-diallyl-1,4-benzoquinone (18) was obtained in good yield (67%). Since the quinone 18 is prone to polymerization (it gave a long streak on TLC when exposed to air at rt), it was immediately subjected to the [4 + 2] cycloaddition reaction with freshly prepared 1,3-cyclopentadiene
PDF
Album
Supp Info
Full Research Paper
Published 13 Nov 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
  • unit. Representative synthetic reactions of fullerene C60 (2) include cyclopropanation [29][30], [3 + 2] cycloaddition [31][32], [4 + 2] cycloaddition [33], nucleophilic addition [34], and radical addition reactions [35]. Two of the earliest and most widely used reactions, the Bingel–Hirsch reaction
PDF
Album
Supp Info
Full Research Paper
Published 28 Apr 2014

Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

  • Yuta Takano,
  • Yuki Nagashima,
  • M. Ángeles Herranz,
  • Nazario Martín and
  • Takeshi Akasaka

Beilstein J. Org. Chem. 2014, 10, 714–721, doi:10.3762/bjoc.10.65

Graphical Abstract
  • and Die & Mould Technology, School of Materials Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China and Department of Chemistry, Tokyo Gakugei University, Tokyo 184-8501, Japan 10.3762/bjoc.10.65 Abstract The [4 + 2] cycloaddition of o-quinodimethanes, generated
  • to remarkable differences in chemical and electronic properties between these two classes of EMFs. Chemical functionalization of fullerenes enhances molecular properties and possible applications of fullerenes [1][4]. The [4 + 2] cycloaddition reaction is a useful chemical modification method because
  • it enables to introduce a variety of addends and/or the combination of different functionalities on the fullerene [7]. Regarding the [4 + 2] cycloaddition of EMFs, however, no report is available for endohedral di-metallofullerenes, with the exception of azafullerene [8]. A limited number of reports
PDF
Album
Supp Info
Full Research Paper
Published 25 Mar 2014

Silver and gold-catalyzed multicomponent reactions

  • Giorgio Abbiati and
  • Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

Graphical Abstract
PDF
Album
Review
Published 26 Feb 2014

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

  • Ludovic Eberlin,
  • Fabien Tripoteau,
  • François Carreaux,
  • Andrew Whiting and
  • Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

Graphical Abstract
  • . In the case of methyl acrylate or acrylonitrile, a mixture of cis diastereomers was obtained regioselectively at higher temperature, in a 1:1.6 to 1:1.8 ratio. By contrast, the [4 + 2]-cycloaddition proved to be completely regioselective when performed on the catechol derivative in the absence of
  • based on a first Diels–Alder cycloaddition, as shown above. However, a recent report of Norsikian, Beau and co-workers described a novel sequence of tandem transformations which combined the Petasis reaction, intramolecular [4 + 2]-cycloaddition, cross metathesis and Michael reaction. This process gave
  • product showed traces of the boron cycloadduct, highlighting that this mechanism proceeds, first with a Lewis-acid catalysed [4 + 2]-cycloaddition, and then by Lewis acid-assisted C–B bond protonation. In a different approach which exploited another aspect of the reactivity of boron-substituted dienes
PDF
Album
Review
Published 22 Jan 2014

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

  • Alexander O. Terent'ev,
  • Dmitry A. Borisov,
  • Vera A. Vil’ and
  • Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

Graphical Abstract
  • peroxides are based on three key reagents: oxygen, ozone, and hydrogen peroxide. These reagents and their derivatives are used in the main methods for the introduction of the peroxide group, such as the singlet-oxygen ene reaction with alkenes, the [4 + 2]-cycloaddition of singlet oxygen to dienes, the
PDF
Album
Review
Published 08 Jan 2014

Gold(I)-catalyzed enantioselective cycloaddition reactions

  • Fernando López and
  • José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

Graphical Abstract
  • allyl cation to the diene. Curiously, by using a gold(I) catalyst bearing a π-acceptor phosphite ligand, such as Au10/AgSbF6, allenedienes disubstituted at the distal position of the allene lead to products formally arising from a [4 + 2] cycloaddition process (Scheme 8, b) [59][60]. Several
  • [4 + 2] cycloaddition (Scheme 9, R1, R2 = alkyl groups). This turned out to be the case and, gratifyingly, we showed that it is possible to perform highly enantioselective allenediene [4 + 2] cycloadditions by using gold complexes derived from a bulky phosphoramidite equipped with anthracenyl
  • into a enantioselective version by using a novel chiral gold complex Au14, featuring a triazole unit embedded in a rigid axially chiral cyclic frame (Scheme 11) [72]. The catalyst generated from Au14 and AgNTf2 was able to promote the [4 + 2] cycloaddition between allenamides 16 and conjugated dienes
PDF
Album
Review
Published 30 Oct 2013

Gold(I)-catalyzed 6-endo hydroxycyclization of 7-substituted-1,6-enynes

  • Ana M. Sanjuán,
  • Alberto Martínez,
  • Patricia García-García,
  • Manuel A. Fernández-Rodríguez and
  • Roberto Sanz

Beilstein J. Org. Chem. 2013, 9, 2242–2249, doi:10.3762/bjoc.9.263

Graphical Abstract
  • also observed in particular cases affording methylenecyclohexene derivatives like VI [14]. On the other hand, 1,6-enynes VII, bearing an aryl substituent at the alkyne, undergo a formal intramolecular [4 + 2] cycloaddition through an initial 5-exo cyclization followed by a Friedel–Crafts-type reaction
  • acetylene moiety would take place through an initial 5-exo cyclization that in the case of aryl-substituted enynes (R = Ar) would give rise to a formal [4 + 2] cycloaddition product XIV [18][19], or alternatively, through a relatively less common 6-endo-dig pathway via gold species XV, which could be
  • and 4a’, is generated in preference to 3a which would be the expected product derived from a formal [4 + 2] cycloaddition initiated by a 5-exo cyclization followed by a Friedel–Crafts-type process in intermediate 5a or 5a’, as described by Echavarren and co-workers [18][19]. Prompted by this result
PDF
Album
Supp Info
Full Research Paper
Published 29 Oct 2013

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

  • Markus Leibeling and
  • Daniel B. Werz

Beilstein J. Org. Chem. 2013, 9, 2194–2201, doi:10.3762/bjoc.9.258

Graphical Abstract
  • for the aspired synthesis [10][11][12][13]. A classical synthesis was published in 1988 by Hansen where a silyl-substituted diene 3 was used for the [4 + 2]-cycloaddition (Scheme 1) [14]. Starting from bisquinone 4 the annulated ring system 5 is obtained in a 1:1 mixture of cis-endo regioisomers
PDF
Album
Supp Info
Full Research Paper
Published 24 Oct 2013

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

  • Peter A. Wade,
  • Alma Pipic,
  • Matthias Zeller and
  • Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

Graphical Abstract
  • been the subject of several theoretical investigations [7][8][9][10]. The necessary nitronic ester precursors are readily preparable by Lewis acid-promoted [4 + 2]-cycloaddition reactions of nitroalkenes with appropriate dienes, a general reaction first reported by Denmark and coworkers (Denmark Diels
PDF
Album
Supp Info
Full Research Paper
Published 17 Oct 2013

The chemistry of isoindole natural products

  • Klaus Speck and
  • Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

Graphical Abstract
  • ) units. The remaining methyl groups are believed to be installed by S-adenosyl methionine (SAM). An intramolecular Aldol condensation generates the pyrrolinone 62, which reacts via an [4 + 2]-cycloaddition to prochaetoglobosin I (63) [56]. Recently, gene disruption studies of Chaetomium globosum revealed
PDF
Album
Video
Review
Published 10 Oct 2013
Other Beilstein-Institut Open Science Activities