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

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

  • Robin Klintworth,
  • Garreth L. Morgans,
  • Stefania M. Scalzullo,
  • Charles B. de Koning,
  • Willem A. L. van Otterlo and
  • Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

Graphical Abstract
  • vinylogous amides such as 11, however, we fortuitously found substituted 2,3-dihydro-1H-pyrrolizines 12 as unexpected products when intermediates 11 were exposed to acidic conditions, including treatment with acetic acid or even during chromatography on silica gel (Scheme 1) [18]. In these cyclizations the
  • case decomposition was noted within 30 seconds, while for the 2-iodo compound complete decomposition took place within 10 minutes (Table 2, entries 11 and 12). Less problematic were the ortho-bromo examples (Table 2, entries 13 and 14), although the cyclizations proceeded with significantly reduced
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Published 13 Oct 2021

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

  • Yi Liu,
  • Puying Luo,
  • Yang Fu,
  • Tianxin Hao,
  • Xuan Liu,
  • Qiuping Ding and
  • Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

Graphical Abstract
  • functionalizations of pyrrole derivatives, such as iodination, bromination, trifluoromethylation, azidation, carbonylation, arylation, and alkylation. The proposed mechanism generally involves two kinds of intramolecular cyclizations: one is 6-endo-dig cyclization to promote the formation of pyridine ring
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Published 22 Sep 2021

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

  • Sumana Mandal,
  • Raju D. Chaudhari and
  • Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

Graphical Abstract
  • chemists. Many transition-metal-salt-mediated cyclizations are reported in literature. Hg(II) salts have been successfully employed in cyclizations to form complex heterocyclic and carbocyclic structures that are impossible to synthesize with other transition metal salts. In this review, we have summarized
  • -) Hg(II)-salt-mediated cyclizations were also observed in the case of alkynes. Arylalkynes 72 were cyclized via Hg(II)-salt-induced reactions to form benzopyran derivatives 73 [73][74][75]. Interestingly in the case of 1-aryloxy-4-arylthio-2-butyne derivatives 74, selective ring closure on the oxygen
  • ]. Devan et al. had developed similar types of Hg(TFA)2-mediated cyclizations of allene 116 at low temperature followed by reduction with alkaline NaBH4 to form cyclized product 117 in moderate yield [88]. The reaction was believed to proceed through Hg(II) ion-promoted electrophilic cyclization (Scheme 35
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Published 09 Sep 2021

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

  • Songeziwe Ntsimango,
  • Kennedy J. Ngwira,
  • Moira L. Bode and
  • Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

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  • ], rhodium-mediated alkyne [2 + 2 + 2] cycloaddition reactions [3], and the palladium-catalysed aerobic domino Suzuki coupling/Michael addition reaction [4]. The most attractive and common strategies to phenanthridines rely on intramolecular cyclizations of various ortho-functionalized biaryl precursors
  • visible light photoredox-catalyzed cyclizations also afforded phenanthridines (Figure 2, reaction 3) [11]. Inspired by the Rodrıguez and Walton approach, we sought to synthesize the nitrogen analogue of an angucycline known as phenanthroviridone 6, [12] from oxime 7 (Scheme 1). Based on the results
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Published 08 Sep 2021

Halides as versatile anions in asymmetric anion-binding organocatalysis

  • Lukas Schifferer,
  • Martin Stinglhamer,
  • Kirandeep Kaur and
  • Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

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  • transformations such as cyclizations or nucleophilic additions. Inspired by cationic terpene-type cyclization cascades, Jacobsen’s group turned their attention to the structure and properties of the chiral part of thiourea catalysts by introducing extended π-groups. A series of thiourea catalysts 53–55 with
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Published 01 Sep 2021

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF3·OEt2 catalysis

  • Karthikeyan Soundararajan,
  • Helen Ratna Monica Jeyarajan,
  • Raju Subimol Kamarajapurathu and
  • Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

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  • M(salen) complexes. Intramolecular Friedel–Crafts cyclizations in Morita–Baylis–Hillman adducts are known to undergo annulations generating cyclic frameworks of indene. To the best of our knowledge, five reports are cited for the intramolecular FC reaction in MBH adducts. The first report was by
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Published 26 Aug 2021

Recent advances in the syntheses of anthracene derivatives

  • Giovanni S. Baviera and
  • Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

Graphical Abstract
  • intramolecular cyclization until 2012 [52]. Mohanakrishnan’s group has contributed with numerous methodologies for the synthesis of anthracene derivatives, mainly methodologies involving Lewis acid-mediated intramolecular cyclizations. For example, in 2012 they reported an annulation protocol to synthesize
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Published 10 Aug 2021

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

  • Thiago S. Silva and
  • Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

Graphical Abstract
  • proved suitable for the synthesis of quaternary centers, although only moderate yields were observed in these cyclizations, and a significant decrease in reactivity was observed when the geminal disubstituted pendant olefin 2c was the cyclization substrate (38% yield) compared with the use of α
  • -cyclization products was attributed to the better overlap between the π-orbital of the enolic carbon atom and the π*-orbital of the complexed olefin terminal carbon. This suggests that, in these cases, the 6-endo-trig cyclizations are under kinetic control. The substrate generality in the methodology
  • yield, and a nature-inspired bicycle 47 was synthetized via two sequential 6-exo-trig cyclizations, giving a preview of the potential use of MHAT methodologies in the synthesis of complex natural products via radical polyene cyclization [78]. Although relevant, the MHAT hydroalkylation methodology
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Published 07 Jul 2021

Substituted nitrogen-bridged diazocines

  • Pascal Lentes,
  • Jeremy Rudtke,
  • Thomas Griebenow and
  • Rainer Herges

Beilstein J. Org. Chem. 2021, 17, 1503–1508, doi:10.3762/bjoc.17.107

Graphical Abstract
  • acetyl group at the CH2NR-bridge and bromo- or iodo-substituents at the distant phenyl ring. The photophysical properties were investigated in acetonitrile and water. As compared to previous approaches the yields of the intramolecular azo cyclizations were increased (from ≈40 to 60%) using an oxidative
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Published 25 Jun 2021

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

  • Premansh Dudhe,
  • Mena Asha Krishnan,
  • Kratika Yadav,
  • Diptendu Roy,
  • Krishnan Venkatasubbaiah,
  • Biswarup Pathak and
  • Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

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  • extreme thermal conditions with the use of corrosive reagents. Much later, Larock and co-workers developed a Pd/Cu-catalyzed imino-annulation of internal alkynes [15], which paved the way for transition-metal-catalyzed cyclizations as easy access to these scaffolds. Notably, the gold-catalyzed tandem
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Published 17 Jun 2021

Synthesis of functionalized imidazo[4,5-e]thiazolo[3,2-b]triazines by condensation of imidazo[4,5-e]triazinethiones with DMAD or DEAD and rearrangement to imidazo[4,5-e]thiazolo[2,3-c]triazines

  • Alexei N. Izmest’ev,
  • Dmitry B. Vinogradov,
  • Natalya G. Kolotyrkina,
  • Angelina N. Kravchenko and
  • Galina A. Gazieva

Beilstein J. Org. Chem. 2021, 17, 1141–1148, doi:10.3762/bjoc.17.87

Graphical Abstract
  • with asymmetric substrates is the high regioselectivity of the cyclizations of intermediate Michael adducts at one of several reactive nitrogen atoms. For example, reported by Giannola et al. [21], the reaction of 3-thioxo-1,2,4-triazin-5-ones 1 with dimethyl acetylenedicarboxylate (DMAD) leads to the
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Published 14 May 2021

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

  • Joseane A. Mendes,
  • Paulo R. R. Costa,
  • Miguel Yus,
  • Francisco Foubelo and
  • Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

Graphical Abstract
  • ][9][10][11] and other compounds that show different types of biological activities [12][13]. The way to achieve these transformations is by intramolecular cyclizations, involving the free primary amine, and appropriate reactive positions (those positions bearing a leaving group) in the electrophile
  • ligands [52][53][54][55] and as chiral auxiliaries [56]. The most widely used synthetic methods to form the aziridine ring [57][58][59][60][61] include intramolecular cyclizations in amines bearing potential leaving groups. Stereoselective syntheses of aziridines have been successfully carried out by
  • hand, natural amino acids proline and hydroxyproline are functionalized pyrrolidines that have found great application in organic synthesis as chiral organocatalysts in stereoselective processes [93][94]. Cyclizations involving a position in the starting chiral imine Arylation of chiral sulfinyl imines
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Published 12 May 2021

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

  • Asha Budakoti,
  • Pradip Kumar Mondal,
  • Prachi Verma and
  • Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

Graphical Abstract
  • ion, which was followed by a completely diastereoselective Friedel–Crafts reaction (Scheme 70). List and co-workers devised a strategy employing highly acidic confined iminoimidodiphosphate (iIDP) Brønsted acids 308 that catalyzed asymmetric Prins cyclizations of both aliphatic and aromatic aldehydes
  • these strategies have been utilized for the elegant synthesis of natural products. In this review, we portrayed an inspection of twenty years in the arena of the development of Prins cyclizations and the further exploration of these strategies in the total synthesis of natural products. This up-to-date
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Published 29 Apr 2021

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

  • Mikhail K. Klychnikov,
  • Radek Pohl,
  • Ivana Císařová and
  • Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

Graphical Abstract
  • step [55]. Radical 5-exo or 5-endo cyclizations of substituted N-allyl or N-vinyl α-halo amides VIII [56][57][58][59][60][61] or X [62][63][64][65][66] using atom transfer and other chain reactions, as well as non-chain methods [67][68][69][70][71][72][73] have been used to approach diverse γ-lactam
  • cyclizations to lactams of type 10 based on the persistent radical effect (PRE) are unknown and may provide a simple access to 3,4-disubstituted γ-lactams. We report here that tandem nucleophilic epoxide ring-opening/Brook rearrangement/radical oxygenation reactions are indeed very effective for the synthesis
  • (2R*,4S*)-9l as the major product (Scheme 8). The outcome of the thermal radical cyclizations of the dioxygenated amides 9 is dependent on the structure of the alkene unit, but the general trend is similar (Scheme 9). Amides with a terminal alkene unit furnished dioxygenated pyrrolidones 12a–f,h–j as
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Published 09 Mar 2021

The preparation and properties of 1,1-difluorocyclopropane derivatives

  • Kymbat S. Adekenova,
  • Peter B. Wyatt and
  • Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

Graphical Abstract
  • ) were successful. Therefore, alternative methods such as intramolecular cyclizations, exchange fluorination, and transformation of functional groups in fluorinated rings have been developed in order to provide access to fluorinated cyclopropanes with electron-withdrawing substituents. 1.1
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Published 26 Jan 2021

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

  • Daria I. Tonkoglazova,
  • Anna V. Gulevskaya,
  • Konstantin A. Chistyakov and
  • Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

Graphical Abstract
  • starting materials, rather expensive catalysts, harsh reaction conditions or low product yields. Transition-metal-catalyzed, electrophile-induced and oxidative radical cyclizations of ortho-alkynylated biaryls are widely used for the synthesis of polynuclear aromatics [57][58][59][60][61][62][63][64][65
  • -2-carbazolylpyridine 6 in 74% yield (Scheme 3). Electrophilic cyclizations of 3-alkynyl-2-carbazolylazines 2a,b and 6 into azine-fused carbazoles 7a–c were carried out with ICl in dry acetonitrile at room temperature in the dark (Table 3). In the cases of compounds 2a,b, the reaction was found to be
  • steps of the method are electrophile-induced 6-endo-dig cyclizations of ortho-alkynylated biaryls. The overall yields of helicenes in five stages of the synthesis exceed 30%. The single-crystal X-ray diffraction analysis revealed the non-planar crystal structures of the synthesized helicenes responsible
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Published 04 Jan 2021

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

  • Dmitrii A. Aksenov,
  • Nikolai A. Arutiunov,
  • Vladimir V. Maliuga,
  • Alexander V. Aksenov and
  • Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

Graphical Abstract
  • discovered that the nucleophilic amines 3 can be successfully employed in this type of transformations as well, providing the amidinium intermediates 4, which are susceptible to a variety of subsequent cyclizations. This approach opens up a novel avenue by which to access the benzoxazoles 5 [40
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Published 26 Nov 2020

Synthesis of novel fluorinated building blocks via halofluorination and related reactions

  • Attila Márió Remete,
  • Tamás T. Novák,
  • Melinda Nonn,
  • Matti Haukka,
  • Ferenc Fülöp and
  • Loránd Kiss

Beilstein J. Org. Chem. 2020, 16, 2562–2575, doi:10.3762/bjoc.16.208

Graphical Abstract
  • interactions are marked with two-headed arrows. Mechanism of the halofluorination reactions of the substrate 19. X = Br (compounds a), I (compounds b), Cl (compounds c). Synthesis and halofluorination of the imide 24. Cyclizations of halofluorinated diesters with potassium tert-butoxide. Relevant NOESY
  • interactions are marked with blue two-headed arrows. Mechanism of the reaction of the cyclopropanation of the compounds (rac)-2a,b and (rac)-5a with t-BuOK. Presumed mechanism of the reaction of the compound (rac)-6b with t-BuOK. Cyclizations of halofluorinated tetrahydrophthalimides with DBU. Relevant NOESY
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Published 16 Oct 2020

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

  • Olusesan K. Koleoso,
  • Matthew Turner,
  • Felix Plasser and
  • Marc C. Kimber

Beilstein J. Org. Chem. 2020, 16, 1983–1990, doi:10.3762/bjoc.16.165

Graphical Abstract
  • innovative transformations, including cycloadditions [5][6][7][8][9], intramolecular cyclizations and intermolecular addition reactions [10][11][12][13][14][15][16][17][18], as well as the use of the allenamide building block in natural product synthesis [1]. Addition reactions of allenamides, which can also
  • encompass intramolecular cyclizations, are typically promoted by the electrophilic activation of the β-carbon of the allenamide. This can be achieved using various electrophilic methods, including the use of Brönsted acids [15][19][20][21][22], halogenation sources [16][18][23][24][25][26][27][28], by means
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Published 12 Aug 2020

Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation–cyclization cascade mediated by K2S2O8

  • Qiang Liu,
  • Weibang Lu,
  • Guanqun Xie and
  • Xiaoxia Wang

Beilstein J. Org. Chem. 2020, 16, 1974–1982, doi:10.3762/bjoc.16.164

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  • oxa-Michael additions of 2’-hydroxychalcones [9][10], or through condensation cyclization reactions of o-hydroxyacetophenones with ketones/aldehydes [11][12], in addition to other alternative transformations [13][14]. Moreover, radical cascade cyclizations of o-allyloxybenzaldehydes by employing
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Published 12 Aug 2020

Controlling the stereochemistry in 2-oxo-aldehyde-derived Ugi adducts through the cinchona alkaloid-promoted electrophilic fluorination

  • Yuqing Wang,
  • Gaigai Wang,
  • Anatoly A. Peshkov,
  • Ruwei Yao,
  • Muhammad Hasan,
  • Manzoor Zaman,
  • Chao Liu,
  • Stepan Kashtanov,
  • Olga P. Pereshivko and
  • Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2020, 16, 1963–1973, doi:10.3762/bjoc.16.163

Graphical Abstract
  • -aldehyde 7. For example, we have explored the potential of the peptidyl reactive site in a number of enolization-driven post-Ugi cyclizations leading to the assembly of pyrrol-2-ones 9 and 10 [59][60]. We have also taken advantage of a 1,3-dicarbonyl moiety present in 8 by engaging them in an enolization
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Published 11 Aug 2020

Regiodivergent synthesis of functionalized pyrimidines and imidazoles through phenacyl azides in deep eutectic solvents

  • Paola Vitale,
  • Luciana Cicco,
  • Ilaria Cellamare,
  • Filippo M. Perna,
  • Antonio Salomone and
  • Vito Capriati

Beilstein J. Org. Chem. 2020, 16, 1915–1923, doi:10.3762/bjoc.16.158

Graphical Abstract
  • intermediate α-imino ketone undergoes when a solution in ChCl/urea is stirred at rt for 4 h in the presence of Et3N (3 equiv) as a base. These cyclizations proved to be relatively sensitive to the electronic properties of the starting phenacyl azides as they did not take place in the presence of strong
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Published 05 Aug 2020

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

  • Dalel El-Marrouki,
  • Sabrina Touchet,
  • Abderrahmen Abdelli,
  • Hédi M’Rabet,
  • Mohamed Lotfi Efrit and
  • Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

Graphical Abstract
  • [15][16][17][18], nucleophilic and electrophilic cyclizations [19][20][21][22][23][24][25], reductive and oxidative cyclizations [26][27], and transition-metal catalysis [28][29][30][31][32][33][34][35][36][37]. There are fewer ways to access indolone derivatives, mainly based on the use of di- [12
  • ][38][39] or triketones [10][13] and enaminones [40][41][42][43] as starting materials. For the synthesis of cinnoline derivatives, aryldiazenes and aryltriazenes are substrates of choice for transition-metal-catalyzed (Rh, Pd, Cu) cross-coupling reactions, followed by intramolecular cyclizations [44
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Published 17 Jul 2020

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

  • Alessandra Del Tito,
  • Havall Othman Abdulla,
  • Davide Ravelli,
  • Stefano Protti and
  • Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

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  • Phenanthrenes and their aza-analogues have important applications in materials science and in medicine. Aim of this review is to collect recent reports describing their synthesis, which make use of radical cyclizations promoted by a visible light-triggered photocatalytic process. Keywords: phenanthrenes
  • cyclizations for the synthesis of polycondensed aromatics, with a focus on those containing heteroatoms [36][37][38][39]. The aim of the present review is to summarize the recent efforts in the design and optimization of photocatalyzed procedures for the synthesis of phenanthrenes and their nitrogen-containing
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Published 25 Jun 2020

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

  • Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

Graphical Abstract
  • excellent radical properties also made these thiyl radicals powerful HAT catalysts. They have increasingly been proven useful in various types of organic photoreactions, such as cyclizations, anti-Markovnikov additions, aromatic olefin carbonylations, isomerizations, etc. They are a class of green, economic
  • variety of reactions, renders them a class of green, economic, mild, and chemoselective radical catalyst. Apart from this, they are also excellent HAT catalysts in photoredox catalysis systems [2][3]. In various types of organic photochemistry reactions, such as cyclizations, anti-Markovnikov additions
  • nonpolar solvent, PhSSPh accelerates the [4 + 2] cycloaddition of the radical cation 19, but the electron-relay catalyst promotes the [2 + 2] cycloaddition. The radical cation 19 can undergo two different types of cyclizations, subject to the relative reactivity of its radical and cation center. The α
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Published 23 Jun 2020
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