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Search for "ring expansion" in Full Text gives 104 result(s) in Beilstein Journal of Organic Chemistry.

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
  • intermediate D into cycloheptadiene E is an example of a relatively rare reaction of the cyclopropane-ring expansion through a 1,5-C‒C bond migration [15][16][17]. This concerted process is followed by yet another 1,5-migration of the hydrogen atom, leading to the final dimer 2a. The formation of a single
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Published 11 May 2022

Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

  • Yelong Lei and
  • Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

Graphical Abstract
  • alkoxycarbonylketenes, which undergo an electrophilic ring expansion with aziridines to afford alkyl 2-(oxazolin-2-yl)alkanoates in good to excellent yields under microwave heating. The method is a convenient and clean reaction without any activators and catalysts and can be also applied in the synthesis of 2-(oxazolin
  • -2-yl)alkanamides and 1-(oxazolin-2-yl)alkylphosphonates. Keywords: aziridine; diazooxoester; diazo compound; ketene; oxazoline; ring expansion; Introduction Oxazoline derivatives are an important class of nitrogen and oxygen-containing five-membered unsaturated heterocycles [1] and widely exist in
  • -diazo-3-oxoalkanoates first generate alkoxycarbonylketenes, which undergo an electrophilic ring expansion with aziridines to afford alkyl 2-(oxazolin-2-yl)alkanoates in good to excellent yields under microwave heating. The current method is an activator- and catalyst-free, and clean synthetic strategy
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Published 05 Jan 2022

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

  • Scott Benz and
  • Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

Graphical Abstract
  • use of aldehydes (R′ = H), which are usually less stable than their ketone counterparts; (2) ring expansion (Z, R = cyclic) or contraction (Z, R′ = cyclic) of strained cyclic α-ketols; (3) the use of α-dicarbonyl compounds (R′ = acyl, ester, amide, etc.), which lead to more stable β-dicarbonyl
  • excellent yields (>85%), but the two most strongly electron-withdrawing, para-CF3 and meta-CH3, had lower yields (59% and 67%, respectively). Instead of a ring expansion driving the rearrangement, the authors also tested a series of α,α-diaryl-α-hydroxyaldehydes 12 and their corresponding aldimines 14
  • concept by application to isolated reactions, while in the following section, examples of tandem reactions in total syntheses are given. Inspired by the direct ring expansion of 1-alkynylcyclobutanols to α-methylenecyclopentanones catalyzed by gold reported by Toste and co-workers [9], Kim et al
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Published 15 Oct 2021

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

  • Guido Gambacorta,
  • James S. Sharley and
  • Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

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Published 18 May 2021

Synthesis of legonmycins A and B, C(7a)-hydroxylated bacterial pyrrolizidines

  • Wilfred J. M. Lewis,
  • David M. Shaw and
  • Jeremy Robertson

Beilstein J. Org. Chem. 2021, 17, 334–342, doi:10.3762/bjoc.17.31

Graphical Abstract
  • Baeyer–Villiger-type ring expansion, hydrolysis and decarboxylation, cyclization and dehydration, and finally hydroxylation at C(7a). Just one month later, Bode reported the identification of an unknown gene cluster in the symbiotic bacterium Xenorhabdus stockiae [23]. Cloning and expression of this
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Published 02 Feb 2021

Hydrazides in the reaction with hydroxypyrrolines: less nucleophilicity – more diversity

  • Dmitrii A. Shabalin,
  • Evgeniya E. Ivanova,
  • Igor A. Ushakov,
  • Elena Yu. Schmidt and
  • Boris A. Trofimov

Beilstein J. Org. Chem. 2021, 17, 319–324, doi:10.3762/bjoc.17.29

Graphical Abstract
  • , namely a Brønsted acid-activated hydroxypyrroline, depend on the reaction conditions and the structure of the hydrazides. Keywords: hydrazides; pyridazines; pyrrolines; recyclization; ring expansion; Introduction Di- and tetrahydropyridazines are valuable heterocyclic motifs which are utilized as key
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Published 29 Jan 2021

All-carbon [3 + 2] cycloaddition in natural product synthesis

  • Zhuo Wang and
  • Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

Graphical Abstract
  • % yield (Scheme 6B). This adduct 92a underwent decarboxylation to afford 92b in 72% yield [42]. Exposure of freshly prepared 92b to triazabicyclodecene [45] led to a ring-expansion/aromatization/aldol cascade producing 93, which was reduced with Et3SiH/TFA smoothly to give indane 94 in 68% yield over two
  • -workers in 2014 [49] (Scheme 9A). The synthesis began with the conversion of ketone 112 into alcohol 113 in four steps, which involved a hypervalent iodine-mediated ring expansion [60]. A two-step synthesis from 113 gave epoxide 114. Epoxide 114 was converted to the corresponding β-ketoester and
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Published 09 Dec 2020

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

  • Shakeel Alvi and
  • Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

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Published 09 Sep 2020

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

  • Clément Q. Fontenelle,
  • Thibault Thierry,
  • Romain Laporte,
  • Emmanuel Pfund and
  • Thierry Lequeux

Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160

Graphical Abstract
  • ester function we expected the ring-opening reaction to proceed with the formation of additional products to alkenes E-13 and Z-13. In fact, two byproducts formed and were identified as β-hydroxymethyl-α-fluorolactone 14 and β-bromomethyl-α-fluorolactone 15 (Table 4) [30]. This ring expansion has been
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Published 07 Aug 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
  • , respectively, which have the same 5-electron 6-carbon cation radical character. Finally, the subsequent deprotonation and HAT by PhS− and PhSH yields the desired [4 + 2] cycloaddition products 22 and 23, respectively. In 1991, Kim and co-workers reported a disulfide-catalyzed ring expansion of cyclobutanone
  • peptide-catalyzed enantioselective cycloaddition. Disulfide-catalyzed [3 + 2] methylenecyclopentane annulations. Disulfide as a HAT cocatalyst in the [4 + 2] cycloaddition reaction. Proposed mechanism of the [4 + 2] cycloaddition reaction using disulfide as a HAT cocatalyst. Disulfide-catalyzed ring
  • expansion of vinyl spiro epoxides. Disulfide-catalyzed aerobic oxidation of diarylacetylene. Disulfide-catalyzed aerobic photooxidative cleavage of olefins. Disulfide-catalyzed aerobic oxidation of 1,3-dicarbonyl compounds. Proposed mechanism of the disulfide-catalyzed aerobic oxidation of 1,3-dicarbonyl
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Published 23 Jun 2020

Recent synthesis of thietanes

  • Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

Graphical Abstract
  • thietane backbones developed during 1966 to 2019. Keywords: cycloaddition; cyclization; ring contraction; ring expansion; thietane; thiotherification; Review 1. Introduction Thietanes are a class of important aliphatic four-membered thiaheterocycles. Some simple alkyl and dialkyl thietanes are components
  • thietane-2-ylideneacetates 397 as byproducts [104] (Scheme 83). 4. Synthesis via the ring expansions and contractions 4.1 Synthesis via ring expansion The ring expansions of thiiranes are alternative ways to prepare thietane derivatives. The transformations included the nucleophilic ring expansion of (1
  • -haloalkyl)thiiranes with various nucleophiles, nucleophilic ring expansion of thiiranes with sulfur ylides, and the electrophilic ring expansion of thiiranes with carbenes generated from sulfur ylides under the catalysis of transition-metal catalysts. 4.1.1 Synthesis via nucleophilic ring expansion of 2-(1
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Published 22 Jun 2020

Synthesis of C70-fragment buckybowls bearing alkoxy substituents

  • Yumi Yakiyama,
  • Shota Hishikawa and
  • Hidehiro Sakurai

Beilstein J. Org. Chem. 2020, 16, 681–690, doi:10.3762/bjoc.16.66

Graphical Abstract
  • that with C60 fragment because most of them consists of acene and/or pyrene units, which might give unique photochemical and electrochemical properties. Recently, we synthesized a buckybowl C28H14 1, which is corresponding to a 40% fragment of C70, from C60-fragment sumanene (2) in three steps via ring
  • expansion by Wagner–Meerwein rearrangement, followed by Pd-catalyzed annulation (Figure 1) [18]. An UV–vis spectroscopy study revealed that the electronic character of 1 rather resembled that of an indenopyrene moiety than that of benzopyrene. Our synthetic route allows to easily introduce substituents on
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Published 15 Apr 2020

Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

  • Svetlana V. Amosova,
  • Andrey A. Filippov,
  • Nataliya A. Makhaeva,
  • Alexander I. Albanov and
  • Vladimir A. Potapov

Beilstein J. Org. Chem. 2020, 16, 515–523, doi:10.3762/bjoc.16.47

Graphical Abstract
  • potassium selenocyanate proceeded via a rearrangement with ring expansion, leading to a six-membered 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate (kinetic product) which in turn underwent rearrangement with ring contraction to a 1,3-thiaselenol-2-ylmethyl selenocyanate (thermodynamic product). These
  • -dihydro-1,4-thiaselenines (up to 96% yields) – products of rearrangement with ring expansion, which in turn underwent rearrangement with ring contraction, forming a new family of 1,3-thiaselenoles in up to 99% yield. The article was included in the RSC themed web collection "The chemistry of Selenium
  • with various nucleophiles (Scheme 4) were accompanied by ring expansion leading to six-membered functionalized dihydrothiaselenines. Furthermore, the reaction of thiaselenole 1 with ammonium thiocyanate also gave the six-membered 2,3-dihydro-1,4-thiaselenin-2-yl thiocyanate (Scheme 4) [46]. It was
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Published 27 Mar 2020

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

  • Sara Peeters,
  • Linn Neerbye Berntsen,
  • Pål Rongved and
  • Tore Bonge-Hansen

Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212

Graphical Abstract
  • efficient way of synthesizing two synthetically versatile 4-quinolone-3-carboxylate building blocks by cyclopropanation-ring expansion of 3-chloroindoles with α-halodiazoacetates as the key step. This novel transformation was applied towards the synthesis of the antibiotic drug norfloxacin. Keywords
  • : catalysis; cyclopropanation; indole; norfloxacin quinoline; quinolone; Rh(II); ring expansion; Introduction The development and use of metal carbenes occupy a central part in the field of the C–H functionalization [1]. Among the metal carbenes, the transient Rh carbenes, usually made by Rh-catalyzed
  • substituted indoles with R-groups in positions 3–7. When R at position 8 = Cl, the reaction was sluggish, and when R at position 2 = Me there was no quinoline formed. The overall transformation is formally a cyclopropanation of the indole C2–C3 double bond followed by a spontaneous ring expansion of the
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Published 13 Sep 2019

The cyclopropylcarbinyl route to γ-silyl carbocations

  • Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

Graphical Abstract
  • bond c to the cationic center gives rearranged cation 44, the source of the rearranged acetate 39. Ring expansion via migration of bond b in 43 gives the β-trimethylsilyl-stabilized cyclobutyl cation 45, and subsequent desilylation provides cyclobutene (35). Alternatively, cyclobutyl to homoallylic
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Published 24 Jul 2019

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

  • Iwona E. Głowacka,
  • Aleksandra Trocha,
  • Andrzej E. Wróblewski and
  • Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

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Published 23 Jul 2019

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

  • Emeline Benoit,
  • Ahmed Fnaiche and
  • Alexandre Gagnon

Beilstein J. Org. Chem. 2019, 15, 1162–1171, doi:10.3762/bjoc.15.113

Graphical Abstract
  • diastereoselective [3 + 2] cycloaddition reaction [14][15]. The ring expansion sequence 1 → 2 → 6 → 8 has been used as a key step in the synthesis of (±)-fragranol [16], (±)-grandisol [16], (±)-α-cuparenone [17] and (±)-herbertene [17]. Aryl cycloropyl sulfides 1 are most frequently prepared by cyclopropylation of
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Published 27 May 2019

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

  • Edorta Martínez de Marigorta,
  • Jesús M. de Los Santos,
  • Ana M. Ochoa de Retana,
  • Javier Vicario and
  • Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

Graphical Abstract
  • dialkyl ones (Scheme 26, path A) [104]. When cyclopropyl ketones 91 were used as substrates, a ring expansion and a new quaternary centre formation happened through the multicomponent reaction to produce pentacyclic derivatives 92 (Scheme 26, path B) [105]. These reactions, either with arenes 86 or
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Published 08 May 2019

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

  • Yu Liu,
  • Qiao-Lin Wang,
  • Zan Chen,
  • Cong-Shan Zhou,
  • Bi-Quan Xiong,
  • Pan-Liang Zhang,
  • Chang-An Yang and
  • Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

Graphical Abstract
  • presence of 2-indobenzoic acid anion. Recently, Shi’s group developed the first ring expansion of MCPs 63 with a nitrogen atom to furnish azetidines 64 (Scheme 14) [82]. The author proposed that Rh(II) had an effective impact on the reactions and could improve the reaction yields. Unfortunately, the MCPs
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Published 28 Jan 2019

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

  • Veronica Paradiso,
  • Chiara Costabile and
  • Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

Graphical Abstract
  • ). Importantly, later on Grubbs and co-workers utilized this kind of catalysts, featuring a chelating N-to-Ru arm, for the preparation of cyclic polymers from cyclic monomers via a ring-expansion metathesis polymerization (REMP) process [38][39]. With the aim of developing catalysts suitable for covalent
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Published 28 Dec 2018

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

  • Takashi Go,
  • Akane Morimatsu,
  • Hiroaki Wasada,
  • Genzoh Tanabe,
  • Osamu Muraoka,
  • Yoshiharu Sawada and
  • Mitsuhiro Yoshimatsu

Beilstein J. Org. Chem. 2018, 14, 2722–2729, doi:10.3762/bjoc.14.250

Graphical Abstract
  • radical cyclisations [28] and the 1,7-electrocyclisation of azomethine ylides or ring expansion sequences [29]), most of these approaches are ineffective for synthesising pyrrolo[3,2-c]azepines. Recently, Echavarren and Beller reported a novel Au- or Pt-catalysed cycloisomerisation reaction of pyrrole-2
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Published 29 Oct 2018

Learning from B12 enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

  • Keishiro Tahara,
  • Ling Pan,
  • Toshikazu Ono and
  • Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

Graphical Abstract
  • confirmed by the spin-trapping technique followed by the ESR measurements. The B12-TiO2 hybrid catalyst also mediated the ring-expansion reactions of alicyclic ketones with carboxylic ester and bromomethyl groups (Scheme 11) [96][98]. The products involving six-, seven-, and eight-membered rings were
  • the presence of photosensitizers. 1,2-Migration of a phenyl group mediated by the visible-light-driven catalytic system composed of 1 and Irdfppy. Ring-expansion reactions mediated by the B12-TiO2 hybrid catalyst with UV-light irradiation. Trifluoromethylation and perfluoroalkylation of aromatic
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Published 02 Oct 2018

Synthesis of 1,4-imino-L-lyxitols modified at C-5 and their evaluation as inhibitors of GH38 α-mannosidases

  • Maroš Bella,
  • Sergej Šesták,
  • Ján Moncoľ,
  • Miroslav Koóš and
  • Monika Poláková

Beilstein J. Org. Chem. 2018, 14, 2156–2162, doi:10.3762/bjoc.14.189

Graphical Abstract
  • , 3-methylpiperidine 11 was isolated as a byproduct in 32% yield. A formation of the piperidine 11 proceeds via opening of aziridinium intermediate 10 (Scheme 1) [32]. Interestingly, a product of a ring expansion was not observed during the tosylate substitution with LiBHEt3. Simple acidic hydrolysis
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Published 17 Aug 2018

Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3+ + 2]-cycloaddition/rearrangement reactions

  • Lin-bo Luan,
  • Zi-jie Song,
  • Zhi-ming Li and
  • Quan-rui Wang

Beilstein J. Org. Chem. 2018, 14, 1826–1833, doi:10.3762/bjoc.14.155

Graphical Abstract
  • followed by a ring-expansion rearrangement. In the rearrangement reaction, the phenyl substituent in the initially formed spiro-triazolium adducts 16 underwent a [1,2]-migration from C(3) to the electron-deficient N(2). This led to the ring expansion from 6-membered piperidine to 7-membered diazepine
  • has a strong proclivity for ring expansion to occur. Accordingly, the 6-membered piperidine ring was enlarged to the 7-membered diazepine ring giving the isolated benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepinium salts 10 via [1,2]-shift. It is noteworthy that the intermediate products 16 bear a
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Published 18 Jul 2018

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

  • Yuichi Yoshimura,
  • Hideaki Wakamatsu,
  • Yoshihiro Natori,
  • Yukako Saito and
  • Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

Graphical Abstract
  • nucleoside 54 in 30% yield, but did not give the desired thietane nucleoside at all (Scheme 6). Considered that the ring-expansion occurred in the absence of the hypervalent iodine reagent, the Nishizono and co-workers speculated that the reaction mechanism was as shown in Scheme 7. First, the Lewis acid
  • . Synthesis of purine 4’-thioribonucleosides using hypervalent iodine-mediated glycosylation. Unexpected glycosylation of a thietanose derivative. Speculated mechanism of the ring expansion of a thietanose derivative. Synthesis of thietanonucleosides using the Pummerer-type glycosylation. First synthesis of 4
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Published 28 Jun 2018
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