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

Carbenoid-mediated nucleophilic “hydrolysis” of 2-(dichloromethylidene)-1,1,3,3-tetramethylindane with DMSO participation, affording access to one-sidedly overcrowded ketone and bromoalkene descendants§

  • Rudolf Knorr,
  • Thomas Menke,
  • Johannes Freudenreich and
  • Claudio Pires

Beilstein J. Org. Chem. 2014, 10, 307–315, doi:10.3762/bjoc.10.28

Graphical Abstract
  • -Bu as the base in warm THF or cyclohexane for deprotonating 14, the generated 12 was found [30] to undergo expansion (FBW) of its five-membered ring rather than the intended formation of the acid 10. As two demonstrations that FBW ring expansion is not an inevitable fate of bona-fide 12, we
  • potassium, finding only the carbenoid chain (SNV) product and its descendants but again no ring expansion [30]. Thus, 12 behaves like a normal unsaturated carbenoid whose SNV reaction requires a more abundant, soluble nucleophile than solid KOt-Bu (or, by analogy, solid KOH). These observations pointed to a
  • chain reaction of 12 with DMSO and the α,α-dichloroalkene 6. Synthesis of the one-sidedly overcrowded descendants 38, 39, and 42. Supporting Information Supporting Information File 162: Alternative synthesis of ketone 38b; preparation of [2-D]10, 33, 39a, 39b, 42b, and 43; FBW ring expansion of
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Published 31 Jan 2014

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

  • Sebastian Krüger and
  • Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

Graphical Abstract
  • this review to other reviews concerning different topics exist [7][8][9][10]. The divinylcyclopropane–cycloheptadiene rearrangement will be abbreviated as DVCPR in the following. The divinylcycloproane moiety and the resulting cycloheptadiene will be highlighted in red throughout. The Buchner ring
  • expansion [11][12] as a special case of the DVCPR is not part of this review. The related vinylcylopropane–cyclopentene rearrangement has been reviewed elsewhere [13][14]. Review Mechanistic considerations Transition state. Although the cis-divinylcyclopropane rearrangement is in fact a tethered version of
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Published 16 Jan 2014

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

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Published 30 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
  • believed to be the direct precursor for the common intermediate 48. Lewis acid catalyzed Tiffenau–Demjanov-type ring expansion of 47 gave 48 as a single product. With α-hydroxy ketone 48 in hand, the stage was set for further modifications to access 26, 27, 49 and 50 (Scheme 5). During their attempts to
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Published 10 Oct 2013

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

  • Huili Liu,
  • Kuan Zheng,
  • Xiang Lu,
  • Xiaoxia Wang and
  • Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

Graphical Abstract
  • Baldwin rule, both 5-exo-trig and 6-endo-trig are favorable in the cyclization. Meanwhile, the ring expansion may occur to constitute the functionalized piperidine ring, resembling Cossy’s endeavor to synthesize velbanamine [48]. In this regard, the same coupling condition was applied for the reaction of
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Published 23 May 2013

4-Pyridylnitrene and 2-pyrazinylcarbene

  • Curt Wentrup,
  • Ales Reisinger and
  • David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 754–760, doi:10.3762/bjoc.9.85

Graphical Abstract
  • ]pyrazine (24). FVT of 4-azidopyridine (18) as well as of 24 or 2-(5-tetrazolyl)pyrazine (23) affords the products expected from the nitrene, i.e., 4,4’-azopyridine and 2- and 3-cyanopyrroles. Matrix photolyses of both 18 and 24 result in ring expansion of 4-pyridylnitrene/2-pyrazinylcarbene to 1,5
  • vacuum thermolysis (FVT) conditions cyanocyclopentadiene 6 is formed (Scheme 1). Several other carbene–nitrene rearrangements have been reported [3][4][5]. In addition to the ring expansion (1–2–3), two ring opening reactions have been investigated in recent years. Type I ring opening takes place in
  • and Discussion Here, we report details of the FVT as well as matrix photolysis reactions of 4-azidopyridine (18) and the isomeric triazolo[1,5-a]pyrazine (24) and its precursor, 2-(5-tetrazolyl)pyrazine (23). Furthermore, we report evidence for ring expansion as well as ring opening of 4
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Published 17 Apr 2013
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  • in a recent review [1] and in several books [2][3][4][5]. This is illustrated by the ring expansion of 4-pyridylnitrene (1) and 2-pyrazinylcarbene (3) to 1,5-diazacyclohepta-1,2,4,6-tetraene (2, Scheme 1) [6]. Similarly, 2-pyridylnitrene (4) interconverts with 1,3-diazacyclohepta-1,2,4,6-tetraene (5
  • propargylic structures, and for this reason their cumulene-type IR absorptions can occur over a wide frequency range, 1900–2300 cm−1, depending on substituents. The IR absorption of 11 was observed at 1961 cm−1, indicating an allenic structure. Nitrene 10 can also undergo ring expansion to two
  • diazacycloheptatetraenes 15 and 16 via the azirenes 13 and 14 (Scheme 3) [13]. The diazacycloheptatetraenes were not observed directly in this study, but aza- and diazacycloheptatetraenes have been observed in several other cases [1][17][18] and the ring-expansion reactions have been the subject of detailed theoretical
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Published 17 Apr 2013

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

  • Toshiki Tabuchi,
  • Daisuke Urabe and
  • Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

Graphical Abstract
  • steps. Bicyclo[3.3.2]decene 1 was prepared from C2-symmetric bicyclo[2.2.2]octene 2 through a ring-expansion reaction (Scheme 1) [11]. We reported the synthetic routes to racemic 2 and enantiomerically pure 2 from 3 and 5, respectively. Specifically, the dearomatizing Diels–Alder reaction between 2,5
  • expected to stereoselectively introduce the C1, C5 and C12 stereocenters to afford bicyclo[3.2.2]nonene 8. The C11-aldehyde of 8 was then to be utilized as a handle for the ring expansion to access 1. To the best of our knowledge, construction of the two quaternary carbons by the intermolecular Diels–Alder
  • afforded 22 as a single stereoisomer, and the obtained 22 was oxidized with DMDO to provide α-hydroxy aldehyde 23 as a diastereomeric mixture (dr = 2.8:1). Compound 23 then reacted with benzyl hydroxylamine to produce oxime 24, LiAlH4-treatment of which led to 25. The regioselective ring expansion of seven
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Published 04 Apr 2013

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
  • ; ring expansion; Introduction Hydroazulene skeletons provide the basic ring systems of natural products, such as guaianolide sesquiterpenes [1][2] and the so-called furanether B series [3][4]. The stereoselective synthesis of trans-hydroazulene derivatives by a tandem Michael/intramolecular Wittig
  • approach was reported previously [5]. Recently, a new synthetic method for the construction of a hydroazulene skeleton by a [5 + 2]cycloaddition reaction was also developed [6]. Additionally, there have been many reports on the synthesis of 2,6-disubstituted azulenes [7][8]. In 1951, the ring expansion of
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Published 04 May 2012

Branching out at C-2 of septanosides. Synthesis of 2-deoxy-2-C-alkyl/aryl septanosides from a bromo-oxepine

  • Supriya Dey and
  • Narayanaswamy Jayaraman

Beilstein J. Org. Chem. 2012, 8, 522–527, doi:10.3762/bjoc.8.59

Graphical Abstract
  • common bromo-oxepine intermediate, involving C–C bond forming organometallic reactions. Unsaturated, seven-membered septanoside vinyl bromides or bromo-oxepines, obtained through a ring expansion methodology of the cyclopropane derivatives of oxyglycals, displayed a good reactivity towards several
  • metathesis reactions of appropriately installed diene derivatives [11][12][13]; (iv) ring expansion of 1,2-cyclopropanated sugars [14][15][16][17]; (v) Baeyer–Villiger oxidation of inositol derivatives [18][19] and (vi) electrophile-induced cyclization [20]. We recently developed a new methodology to prepare
  • envisaged that III would form as a synthon to implement C–C bond forming reactions. Vinyl halide 2 was synthesized through a ring-expansion reaction of cyclopropanated adduct 1 (Scheme 1), as reported previously [21]. The reactivity at C-2 of 2 was examined by the chosen organometallic reactions, namely
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Published 10 Apr 2012

Perhydroazulene-based liquid-crystalline materials with smectic phases

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

Beilstein J. Org. Chem. 2012, 8, 403–410, doi:10.3762/bjoc.8.44

Graphical Abstract
  • achieved by the introduction of terminal groups preferentially in trans- or anti-fashion. We previously employed a ring expansion strategy for the synthesis of the perhydroazulene core and were able to also purify several of our carbene adducts by way of HPLC [14]. If we start our synthesis by the
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Published 16 Mar 2012

Aldol elaboration of 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridin-4-ones, masked precursors to acylpyridones

  • Raymond C. F. Jones,
  • Abdul K. Choudhury,
  • James N. Iley,
  • Mark E. Light,
  • Georgia Loizou and
  • Terence A. Pillainayagam

Beilstein J. Org. Chem. 2012, 8, 308–312, doi:10.3762/bjoc.8.33

Graphical Abstract
  • genetic techniques, and been shown to involve conversion from an acyltetramic acid by oxidative ring expansion [7][8]. During a programme of synthesis towards metabolites containing the enolised heterocyclic tricarbonyl motif 3 [9][10][11][12][13][14][15][16], we have reported nitrile oxide dipolar
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Published 27 Feb 2012

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

  • Helen Jansen,
  • J. Chris Slootweg and
  • Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

Graphical Abstract
  • et al. using a double dehydrohalogenation of 1,2-dibromo-4,5-epoxycyclohexane [38][53], but is also accessible by epoxidation of Dewar benzene followed by photolytic or thermal ring expansion [54]. The molecular structure of the 2-tert-butoxycarbonyl oxepine showed a boat configuration with bow (α
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Published 21 Dec 2011

Continuous flow photolysis of aryl azides: Preparation of 3H-azepinones

  • Farhan R. Bou-Hamdan,
  • François Lévesque,
  • Alexander G. O'Brien and
  • Peter H. Seeberger

Beilstein J. Org. Chem. 2011, 7, 1124–1129, doi:10.3762/bjoc.7.129

Graphical Abstract
  • tools, both for preparative heterocycle synthesis [16][17] and for photoaffinity labeling of proteins [18][19][20]. The photolysis of aryl azide 1 [21], a well-studied and widely used reaction [22][23][24][25][26][27][28][29][30], generates the singlet aryl nitrene intermediate 12 (Scheme 1). Ring
  • expansion of 12, via 2H-azirine 3, affords didehydroazepine 4, which can be trapped by variety of nucleophiles to provide the corresponding azepine 5. Alternatively, intersystem crossing (ISC) of 12 gives rise to 32, which can dimerize to form diazo compound 6. Performing the reaction in the presence of
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Published 17 Aug 2011

Recent developments in gold-catalyzed cycloaddition reactions

  • Fernando López and
  • José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

Graphical Abstract
  • on an initial (3 + 2) dipolar cycloaddition between the carbonyl ylide IV and the alkene, followed by a ring expansion (1,2-alkyl migration) that is assisted by the oxy group and generates the oxonium intermediate V (Scheme 2). A final elimination process regenerates the catalyst and affords the
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Published 09 Aug 2011

Recent advances in the gold-catalyzed additions to C–C multiple bonds

  • He Huang,
  • Yu Zhou and
  • Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

Graphical Abstract
  • rearrangement followed by nucleophilic attack of the Boc-protected nitrogen atom. A similar method to synthesize the 2-vinylpiperidin-3-ol 158 by a highly stereoselective gold-catalyzed allene cyclization has been reported (Scheme 27) [72]. The ring expansion of cyclopropane derivatives provides a powerful
  • method to construct synthetically useful four-membered carbocycles. Ye et al. reported a new type of gold(I)-catalyzed ring expansion of an non-activated alkynylcyclopropane/sulfonamide to obtain (E)-2-alkylidenecyclobutanamines [73]. For example, treatment of alkynylcyclopropane 159 with TsNH2 and 5 mol
  • in high yields [77]. However, in some cases, aryl-substituted N-tosyl alkynyl aziridines 169 undergo a gold-catalyzed ring expansion to afford 2,5-substituted or 2,4-substituted pyrrole products [78]. Interestingly, the reaction pathway is determined by the counter ion of the gold catalyst. The
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Published 04 Jul 2011

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

  • Paul W. Davies,
  • Nicolas Martin and
  • Neil Spencer

Beilstein J. Org. Chem. 2011, 7, 839–846, doi:10.3762/bjoc.7.96

Graphical Abstract
  • other reports into π-acid promoted alkynyl aziridine cycloisomerisations without skeletal rearrangement [20][21][22][23]. Our working mechanism to explain this reaction divergence centred on the electrophilic activation of the alkyne in A triggering a ring-expansion to a common intermediate B from which
  • requires fission of three bonds: The propargylic C–N bond in ring expansion; the aryl–aziridinyl C–C bond in the 1,2 shift and the propargylic C–H bond for aromatisation (Scheme 3). The positioning of a deuterium atom at the benzylic carbon in 4 enables the carbons of the aziridine ring to be distinguished
  • expansion of metal coordinated alkynyl aziridines to the 5-membered cyclic cation B, which leads to isotopomer G (Path II) and 2,5-disubstituted pyrroles D (Path I), a competing regioisomeric ring-expansion could afford 4-membered ring intermediate I. Evolution of I by a ring-expanding 1,2-shift of the
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Published 21 Jun 2011

Synthesis of novel 5-alkyl/aryl/heteroaryl substituted diethyl 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates by aziridine ring expansion of 2-[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters

  • Satish S. More,
  • T. Krishna Mohan,
  • Y. Sateesh Kumar,
  • U. K. Syam Kumar and
  • Navin B. Patel

Beilstein J. Org. Chem. 2011, 7, 831–838, doi:10.3762/bjoc.7.95

Graphical Abstract
  • /bjoc.7.95 Abstract A novel synthetic methodology has been developed for the synthesis of diethyl 5-alkyl/aryl/heteroaryl substituted 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates (also called 2-substituted pyrroline-4,5-dihydro-3,3-dicarboxylic acid diethyl esters) by iodide ion induced ring expansion of 2
  • -[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters in very good to excellent yields under mild reaction conditions. The electronic and steric impact of the substituents on the kinetics of ring expansion of N-vinyl aziridines to pyrrolines has been studied. Various diversely
  • -vinyl substituted aziridines; ring expansion; sodium iodide; Introduction Vinylaziridines are a particularly interesting class of aziridine derivatives that lend themselves to a host of highly useful synthetic transformations [1]. They are versatile electrophiles and notably undergo regioselective ring
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Published 20 Jun 2011

Synthetic applications of gold-catalyzed ring expansions

  • David Garayalde and
  • Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

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  • ; ring expansion; strained rings; Introduction Over the past twenty years, the image of gold has evolved, from being considered a dead-entity in terms of chemical reactivity, to playing a key role in catalytic processes. The vast array of gold-mediated transformations reported so far share a common
  • powerful in triggering ring-expansion processes to introduce structural complexity into organic molecules. The gold-catalyzed ring expansion of strained rings is viewed nowadays as a flexible synthetic tool in organic synthesis [7][8][9]. In this review, we aim to summarize the most recent developments in
  • the various approaches to access these ubiquitous scaffolds, the gold(I)-catalyzed ring expansion of cyclopropanols and cyclobutanols is considered one of the most powerful and versatile methods. In 2005, Toste and co-workers reported the treatment of 1-(phenylethynyl)cyclopropanol (11) with tris(4
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Published 07 Jun 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
  • diradical intermediate of type 17, its lifetime is evidently too short to allow ring-expansion as depicted in Scheme 7. Whether this process might be induced thermally (vinylcyclopropane→cyclopentene rearrangement; [23]) is an open question. Conclusion Although the detailed mechanisms of the
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Published 24 May 2011

Molecular rearrangements of superelectrophiles

  • Douglas A. Klumpp

Beilstein J. Org. Chem. 2011, 7, 346–363, doi:10.3762/bjoc.7.45

Graphical Abstract
  • the synthesis of the analgesic drug butorphanol (40) [21], a key step involves the ring expansion of dication 42 to dication 43 (Scheme 9). Interestingly, the ring expansion step moves the carbocationic site away from a benzylic position, but also transforms it from a 1,4-dication to a 1,5-dication
  • . Condensations of ninhydrin (28) with benzene. Rearrangement of 29 to 30. Superacid promoted ring opening of succinic anhydride (33). Reaction of phthalic acid (36) in FSO3H-SbF5. Ring expansion of superelectrophile 42. Reaction of camphor (44) in superacid. Isomerization of 2-cyclohexen-1-one (48
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Published 23 Mar 2011

Rh-Catalyzed rearrangement of vinylcyclopropane to 1,3-diene units attached to N-heterocycles

  • Franca M. Cordero,
  • Carolina Vurchio,
  • Stefano Cicchi,
  • Armin de Meijere and
  • Alberto Brandi

Beilstein J. Org. Chem. 2011, 7, 298–303, doi:10.3762/bjoc.7.39

Graphical Abstract
  • group endows many natural and synthetic compounds with a broad spectrum of interesting properties, mainly related to its unusual bonding and inherent ring strain [1][2][3]. This characteristic confers on molecules containing this moiety high reactivity, especially towards ring expansion and ring-opening
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Published 09 Mar 2011

Ene–yne cross-metathesis with ruthenium carbene catalysts

  • Cédric Fischmeister and
  • Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

Graphical Abstract
  • reaction demonstrated that ruthenium alkylidene was the active catalytic species (methylidene free conditions). This ring expansion could be extended to fused cycloalkene substrates such as tetrahydroindene and bicyclo[3.2.0]heptenone, both of them featuring a cyclopentene unit to form functionalized
  • obtained for EYCM with styrenes. EYCM of terminal olefins with internal borylated alkynes. Synthesis of propenylidene cyclobutane via EYCM. Efficient EYCM with vinyl ethers. From cyclopentene to cyclohepta-1,3-dienes via cyclic olefin-alkyne cross-metathesis. Ring expansion via EYCM from bicyclic olefins
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Published 04 Feb 2011

Highly substituted benzannulated cyclooctanol derivatives by samarium diiodide-induced cyclizations

  • Jakub Saadi,
  • Irene Brüdgam and
  • Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, 1229–1245, doi:10.3762/bjoc.6.141

Graphical Abstract
  • ][7][8][9][10][11][12][13][14][15][16][17][18]. Successful approaches include ring-closing metathesis [4], rearrangements [5], and cycloadditions [6], transition metal-catalyzed cyclizations [7][8], nucleophilic and electrophilic substitution reactions [9] as well as ring expansion reactions [10
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Published 28 Dec 2010

Total synthesis of (±)-coerulescine and (±)-horsfiline

  • Mukund G. Kulkarni,
  • Attrimuni P. Dhondge,
  • Sanjay W. Chavhan,
  • Ajit S. Borhade,
  • Yunnus B. Shaikh,
  • Deekshaputra R. Birhade,
  • Mayur P. Desai and
  • Nagorao R. Dhatrak

Beilstein J. Org. Chem. 2010, 6, 876–879, doi:10.3762/bjoc.6.103

Graphical Abstract
  • include the following oxidative rearrangements: lead tetraacetate [3], sodium tungstate [11], tert-butyl hypochlorite [12] and N-bromosuccinimide [13]. Other approaches involve the Mannich reaction [14], ring expansion reactions [15][16], 1,3-dipolar [3 + 2] cycloadditions [17][18][19], intramolecular
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Published 27 Sep 2010
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