Search results

Search for "cyclizations" in Full Text gives 199 result(s) in Beilstein Journal of Organic Chemistry.

Anion–π catalysis on carbon allotropes

  • M. Ángeles Gutiérrez López,
  • Mei-Ling Tan,
  • Giacomo Renno,
  • Augustina Jozeliūnaitė,
  • J. Jonathan Nué-Martinez,
  • Javier Lopez-Andarias,
  • Naomi Sakai and
  • Stefan Matile

Beilstein J. Org. Chem. 2023, 19, 1881–1894, doi:10.3762/bjoc.19.140

Graphical Abstract
  • introduced in 2017, followed by carbon nanotubes in 2019. Consistent with expectations from theory, anion–π catalysis on carbon allotropes generally increases with polarizability. Realized examples reach from enolate addition chemistry to asymmetric Diels–Alder reactions and autocatalytic ether cyclizations
  • catalysis; electromicrofluidics; enolate addition; ether cyclizations; fullerenes; Introduction Anion–π catalysis was introduced ten years ago [1]. The idea is to stabilize anionic transition states on electron-deficient, π-acidic aromatic surfaces (Figure 1A). The true beginning is arguably in 2015
  • catalysis. Moreover, epoxide opening polyether cyclizations are among the most impressive cascade reactions in nature [71][72][73]. Best known is the hypothetical cascade XII in the biosynthesis of brevetoxin B [74]. It affords eleven fused ethers by violating the Eschenmoser–Dunitz–Baldwin guidelines [75
PDF
Album
Review
Published 12 Dec 2023

Synthetic approach to 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides based on common β-keto amide precursors

  • Yordanka Mollova-Sapundzhieva,
  • Plamen Angelov,
  • Danail Georgiev and
  • Pavel Yanev

Beilstein J. Org. Chem. 2023, 19, 1804–1810, doi:10.3762/bjoc.19.132

Graphical Abstract
  • reductive cyclizations of o-nitrobenzoyl ketones [57][58], enamines [59][60], or isoxazoles [61]. The scope of these reductive cyclizations is limited by the availability of the necessary intermediates and has remained largely underexplored, especially with regard to 4-quinolones with long-chain
PDF
Album
Supp Info
Full Research Paper
Published 23 Nov 2023

Synthesis of 7-azabicyclo[4.3.1]decane ring systems from tricarbonyl(tropone)iron via intramolecular Heck reactions

  • Aaron H. Shoemaker,
  • Elizabeth A. Foker,
  • Elena P. Uttaro,
  • Sarah K. Beitel and
  • Daniel R. Griffith

Beilstein J. Org. Chem. 2023, 19, 1615–1619, doi:10.3762/bjoc.19.118

Graphical Abstract
  • cyclized product 16 in 75% yield. These results suggest that these Heck cyclizations are quite sensitive to the identity of the alkene substituent that is cis to the halogen. We were also interested in engaging vinyl iodide 17 in a 7-exo-trig cyclization to form 18. Z-Iodoalkene 17 appeared to react
PDF
Album
Supp Info
Full Research Paper
Published 23 Oct 2023

Unraveling the role of prenyl side-chain interactions in stabilizing the secondary carbocation in the biosynthesis of variexenol B

  • Moe Nakano,
  • Rintaro Gemma and
  • Hajime Sato

Beilstein J. Org. Chem. 2023, 19, 1503–1510, doi:10.3762/bjoc.19.107

Graphical Abstract
  • . Several terpene cyclizations with an exomethylene group are known, such as with caryolene and crotinsulidane diterpenoids, and the reaction mechanisms have been analyzed [27][28][29][30]. It would be interesting to see how the exomethylene group reacts in the cyclization of variexenol B. In this study, we
PDF
Album
Supp Info
Letter
Published 28 Sep 2023

Synthesis of medium and large phostams, phostones, and phostines

  • Jiaxi Xu

Beilstein J. Org. Chem. 2023, 19, 687–699, doi:10.3762/bjoc.19.50

Graphical Abstract
  • phostams, phostones, and phostines are summarized. They include cyclizations and annulations. Cyclizations achieve ring construction through the formations of C–C, C–O, P–C, and P–O bonds in the rings, while annulations build the rings via [5 + 2], [6 + 1], and [7 + 1] fashions with the stepwise formation
  • the catalytic antibody [24]. They are also potential chiral ligands in asymmetric catalysis [25] (Figure 1). Cyclizations and annulations are two major strategies for the synthesis of medium and large phostam, phostone, and phostine derivatives. The cyclizations have been applied in the construction
  • developed for the synthesis of seven-membered phostone and phostine derivatives. Review 1 Synthesis via cyclizations Cyclizations are major strategies for the construction of medium and large phostams, phostones, and phostines via C–C, C–O, P–C, and P–O bond formations, respectively. These strategies can be
PDF
Album
Review
Published 15 May 2023

Nucleophile-induced ring contraction in pyrrolo[2,1-c][1,4]benzothiazines: access to pyrrolo[2,1-b][1,3]benzothiazoles

  • Ekaterina A. Lystsova,
  • Maksim V. Dmitriev,
  • Andrey N. Maslivets and
  • Ekaterina E. Khramtsova

Beilstein J. Org. Chem. 2023, 19, 646–657, doi:10.3762/bjoc.19.46

Graphical Abstract
  • to the PBTA scaffold is an annulation of benzothiazoles with a pyrrole moiety (Scheme 1). It includes intramolecular cyclizations of benzothiazoles bearing a 3'-chloro substituent at C2 position (Scheme 1, entries 1 and 2) [5][6][7], intramolecular catalytic carbene cascade reactions of propargyl 1,3
  • 1-(2-thiophenyl)pyrroles (Scheme 4). It includes intramolecular cationic π-cyclizations in 3-hydroxy-2-(2-sulfanylphenyl)-2,3-dihydro-1H-isoindol-1-ones (Scheme 4, entry 14) [9] and intramolecular cyclizations of 1-(2-(methylsulfinyl)phenyl)-1H-pyrroles under «interrupted Pummerer rearrangement
  • reaction in 1-(2-bromophenyl)-5-(butylsulfanyl)pyrrolidin-2-one. Approach to PBTAs via intramolecular cyclizations of 1-(2-thiophenyl)pyrroles. A new approach to PBTAs via nucleophile-induced ring contraction in pyrrolo[2,1-c][1,4]benzothiazines. Reaction of APBTT 1a with methanol (2a). Derivatization of
PDF
Album
Supp Info
Full Research Paper
Published 11 May 2023

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

  • Austin Pounder,
  • Eric Neufeld,
  • Peter Myler and
  • William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

Graphical Abstract
  • exo face of 30b, oxidative cyclization can afford the ruthenacycle 101. Unlike previous works studying Ru-catalyzed cyclizations involving bicyclic alkenes and alkynes [56][57][58][59], the reaction preferentially undergoes β-hydride elimination to generate 102 rather than reductive elimination which
PDF
Album
Review
Published 24 Apr 2023

Computational studies of Brønsted acid-catalyzed transannular cycloadditions of cycloalkenone hydrazones

  • Manuel Pedrón,
  • Jana Sendra,
  • Irene Ginés,
  • Tomás Tejero,
  • Jose L. Vicario and
  • Pedro Merino

Beilstein J. Org. Chem. 2023, 19, 477–486, doi:10.3762/bjoc.19.37

Graphical Abstract
  • parameters for transannular cyclizations illustrated in Scheme 1.a Calculated activation parameters for transannular cyclizations illustrated in Scheme 2.a Distortion–interaction analysis for fused cyclohexanes. Distortion-interaction analysis for fused cyclopentanes and system 7-8. Comparison of relative
PDF
Album
Supp Info
Full Research Paper
Published 20 Apr 2023

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

  • Cécile Alleman,
  • Charlène Gadais,
  • Laurent Legentil and
  • François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

Graphical Abstract
  • found multiple applications in natural product synthesis [65]. Employed in C–C bond-formation reactions, this single-electron reducing agent has been particularly useful for five- to eight-membered ring cyclizations [65]. Its tunable reactivity opens access to both radical and anionic processes, hence
PDF
Album
Review
Published 03 Mar 2023

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

  • Bilge Banu Yagci,
  • Selin Ezgi Donmez,
  • Onur Şahin and
  • Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

Graphical Abstract
  • differences between acyl chlorides 23 and 6 in the examined aza-Nazarov cyclizations can be understood when the electron densities on the two olefin moieties are considered. Indeed, while both of the proposed intermediates 29 and 9 (Scheme 1) can benefit from the β-silicon stabilization effect, the olefinic
  • the β-silicon effect in this aza-Nazarov cyclization. During the course of our studies, we observed occasionally the formation of aldehyde-containing side products, the amount of which increased when the aza-Nazarov cyclizations did not proceed efficiently. We proposed that, if the aza-Nazarov
PDF
Album
Supp Info
Full Research Paper
Published 17 Jan 2023

NaI/PPh3-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

  • Dan Liu,
  • Yue Zhao and
  • Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

Graphical Abstract
  • reactions constitute a powerful synthetic approach to construct multiple C–C or C–X bonds in one pot. As such, these tend to allow facile access to many complex natural molecules and drugs [1][2][3][4][5][6]. Recently, radical-initiated cascade cyclizations involving acrylamides have attracted considerable
PDF
Album
Supp Info
Letter
Published 16 Jan 2023

Combining the best of both worlds: radical-based divergent total synthesis

  • Kyriaki Gennaiou,
  • Antonios Kelesidis,
  • Maria Kourgiantaki and
  • Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

Graphical Abstract
  • reduction of the amide using Wilkinson’s catalyst provided diastereoisomeric indole 131. Careful manipulation of the nitrile and alcohol side chains allowed selective cyclizations to the nitrogen atom of the indole core to conclude the total syntheses of 132–134. Samarium diiodide-mediated reductive
PDF
Album
Review
Published 02 Jan 2023

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

  • Elena R. Lopat’eva,
  • Igor B. Krylov,
  • Dmitry A. Lapshin and
  • Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

Graphical Abstract
  • organic syntheses [5][6][7][8][9] and offer rich opportunities for the adaptation of organocatalysis. The diversity of such transformations spans from the functionalization of hydrocarbon raw materials to the fine organic synthesis, including functional group transformations, oxidative cyclizations, and
  • coupling, or deprotonation followed by the functionalization of α- and β-positions of the starting aldehyde. NHC-catalyzed photochemical processes [64] and oxidative cyclizations with heterocycle formation [65] were reviewed previously. Acidic molecules or hydrogen-bond donors are used as organocatalysts
  • the key factor for the high chemoselectivity. Hypervalent iodine catalysis Effective hypervalent iodine(III)-catalyzed processes (for example, oxidative double C=C bond functionalization, oxidative cyclizations, CH-functionalization of carbonyl compounds, etc.) employing mainly peroxoacids or electric
PDF
Album
Perspective
Published 09 Dec 2022

A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition

  • Anastasia Vepreva,
  • Alexander Yanovich,
  • Dmitry Dar’in,
  • Grigory Kantin,
  • Alexander Bunev and
  • Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177

Graphical Abstract
  • reaction conditions was undertaken except for the isolation for the initial O–H insertion product which facilitated subsequent steps (the Claisen rearrangement and the final cyclization, vide infra). With product 6a at hand we proceeded studying its base-promoted Michael-type cyclizations. As it follows
  • from the data collated in Table 1, to our delight, cyclizations of the phenoxide anion generated on the action of base (except for 2,6-lutidine) proceeded as 5-exo-trig (rather than 6-endo-trig) process and yielded spirocyclic compound 7a as a mixture of syn and anti diastereomers. DABCO in toluene at
PDF
Album
Supp Info
Full Research Paper
Published 06 Dec 2022

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

  • Keith P. Reber and
  • Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

Graphical Abstract
  • derived from a common biosynthetic pathway starting from farnesyl pyrophosphate and glycine [5]. This prompted us to investigate a biomimetic synthesis in which the halichonic acids could be prepared from a common imine intermediate via divergent intramolecular aza-Prins cyclizations [8]. Herein, we
PDF
Album
Supp Info
Full Research Paper
Published 01 Dec 2022

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

  • Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

Graphical Abstract
  • been prepared through two major strategies of cyclizations and annulations. Cyclizations achieve ring construction through the formation of any bond in the ring, while annulations build the ring via [4 + 1] and [3 + 2] fashions with the simultaneous formation of two bonds. The review includes the
  • their fused derivatives have been synthesized through various synthetic strategies. The synthetic strategies can be categorized into cyclization and annulation strategies. The cyclizations have been widely applied for the formation of any C–N, C–P, P–N, and C–C bonds in the 1,2-azaphospholidine ring. [4
PDF
Album
Review
Published 22 Jul 2022

Efficient production of clerodane and ent-kaurane diterpenes through truncated artificial pathways in Escherichia coli

  • Fang-Ru Li,
  • Xiaoxu Lin,
  • Qian Yang,
  • Ning-Hua Tan and
  • Liao-Bin Dong

Beilstein J. Org. Chem. 2022, 18, 881–888, doi:10.3762/bjoc.18.89

Graphical Abstract
  • cyclase) act on geranylgeranyl diphosphate (GGDP) to perform regio- and stereoselective cyclizations or skeleton rearrangement reactions via carbocation chemistry to form diverse and versatile carbon skeletons; and ii) multiple post-modification enzymes, most often cytochrome P450s, decorate the carbon
PDF
Album
Supp Info
Full Research Paper
Published 21 Jul 2022

Structural basis for endoperoxide-forming oxygenases

  • Takahiro Mori and
  • Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

Graphical Abstract
  • the synthesis of chemical reagents with an endoperoxide bridge have been reported [77][78]. The classical method for endoperoxide synthesis is through cycloadditions of dienes and alkenes, using singlet oxygen. Furthermore, cyclizations of hydroperoxides with pendant alkenes or alkynes have also been
PDF
Album
Review
Published 21 Jun 2022

Unusual highly diastereoselective Rh(II)-catalyzed dimerization of 3-diazo-2-arylidenesuccinimides provides access to a new dibenzazulene scaffold

  • Anastasia Vepreva,
  • Alexander S. Bunev,
  • Andrey Yu. Kudinov,
  • Grigory Kantin,
  • Mikhail Krasavin and
  • Dmitry Dar’in

Beilstein J. Org. Chem. 2022, 18, 533–538, doi:10.3762/bjoc.18.55

Graphical Abstract
  • diazocarbonyl compounds [5]. The close spatial arrangement of the conjugate aryl fragment and the diazo group in the DAS molecule favors both intramolecular and intermolecular cyclizations involving the arylidene group. Thus, under catalytic decomposition, DAS containing a 2-pyridyl or 2-hydroxyaryl substituent
PDF
Album
Supp Info
Letter
Published 11 May 2022

Synthesis of piperidine and pyrrolidine derivatives by electroreductive cyclization of imine with terminal dihaloalkanes in a flow microreactor

  • Yuki Naito,
  • Naoki Shida and
  • Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 350–359, doi:10.3762/bjoc.18.39

Graphical Abstract
  • their demonstration. Therefore, it is desirable to conduct the reductive cyclizations without the use of a mercury cathode, and the development of a simple, green, and efficient method for the electrochemical synthesis of heterocyclic amines is an important research target. The electrochemical flow
PDF
Album
Supp Info
Full Research Paper
Published 29 Mar 2022

Regioselectivity of the SEAr-based cyclizations and SEAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

  • Jonali Das and
  • Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

Graphical Abstract
  • regioselectivity switching in the SEAr-based cyclizations of 3,5-unsubstituted, 4-substituted indoles. In the course of their studies on chemospecific cyclization of α-carbonyl sulfoxonium ylides on aryls and heteroaryls, the Aïssa group in 2019 demonstrated hexafluoroisopropanol (HFIP)-promoted regioselective
PDF
Album
Commentary
Published 08 Mar 2022

Synthesis and late stage modifications of Cyl derivatives

  • Phil Servatius and
  • Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

Graphical Abstract
  • should undergo a wide range of addition reactions. Ozonolysis, on the other hand, should generate a carbonyl functionality. Radical additions towards the double unsaturated side chain of the Cyl-1 derivative might also allow cyclizations. To get access to the desired double unsaturated cyclopeptide, we
PDF
Album
Supp Info
Full Research Paper
Published 04 Feb 2022

Synthesis of new pyrazolo[1,2,3]triazines by cyclative cleavage of pyrazolyltriazenes

  • Nicolai Wippert,
  • Martin Nieger,
  • Claudine Herlan,
  • Nicole Jung and
  • Stefan Bräse

Beilstein J. Org. Chem. 2021, 17, 2773–2780, doi:10.3762/bjoc.17.187

Graphical Abstract
  • [3,4-d][1,2,3]triazine compounds 5 (Scheme 4). The successful cyclizations gave the desired pyrazolo[3,4-d][1,2,3]triazines 5 in moderate to good yields. Not all cyclization products were air-stable. While compounds 5a–d with a benzylic side chain in R1'' were stable, a full characterization was
PDF
Album
Supp Info
Full Research Paper
Published 22 Nov 2021

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet–Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids

  • Marco Keller,
  • Karl Sauvageot-Witzku,
  • Franz Geisslinger,
  • Nicole Urban,
  • Michael Schaefer,
  • Karin Bartel and
  • Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2716–2725, doi:10.3762/bjoc.17.183

Graphical Abstract
  • approaches to the monomeric 1-benzyl-1,2,3,4-tetrahydroisoquinoline alkaloids are typically inspired by their biosynthesis and comprise Bischler–Napieralski-type cyclizations of arylacetamides (followed by reduction of the resulting 3,4-dihydroisoquinolines) or Pictet–Spengler-type cyclizations of
  • ] demonstrated that this building block is compatible with N-acyl-Pictet–Spengler cyclization conditions. The structures of the utilized building blocks are shown in Figure 4. The N-acyl-Pictet–Spengler cyclizations of appropriate pairs of the building blocks with TFA in dichloromethane at 0 °C for 19–90 h (TLC
PDF
Album
Supp Info
Full Research Paper
Published 05 Nov 2021

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

  • Ilya A. P. Jourjine,
  • Lukas Zeisel,
  • Jürgen Krauß and
  • Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

Graphical Abstract
  • radical cyclizations [22], Pschorr reactions [23], and diverse cycloaddition protocols [24][25]. Especially transition-metal-catalyzed cross-coupling reactions starting from benzophenones, benzoic acids, dihalogenated benzene building blocks and others have emerged as new approaches in recent years [26
  • ][27][28]. Various approaches starting from functionalized biaryls have hereby attracted considerable interest, since the precursors are readily available by established cross-coupling reactions. Beyond transition-metal-catalyzed reactions, acid-mediated cyclizations of biphenylcarboxylic acids and
  • ], CBr4 [22], or peroxides like tert-butyl hydroperoxide (TBHP) [35]. Other oxidative cyclizations have been developed starting from biarylglyoxylic acids (using Na2S2O8) [36], and even 2-methylbiphenyls and 2-(hydroxymethyl)biphenyls can be converted into fluorenones by means of TBHP oxidation [37]. In
PDF
Album
Supp Info
Correction
Full Research Paper
Published 02 Nov 2021
Other Beilstein-Institut Open Science Activities