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Search for "pyrroles" in Full Text gives 141 result(s) in Beilstein Journal of Organic Chemistry.

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
  • aziridines into 2,4-disubstituted pyrroles. Two isotopomers of the expected skeletal rearrangement product were identified using 13C-labelling and led to a revised mechanism featuring two distinct skeletal rearrangements. The mechanistic proposal has been rationalised against the reaction of a range of 13C
  • : 2,4-Disubstituted pyrroles were only observed in appreciable quantities when the reaction was performed with a non basic solvent and counter ion combination that allows for formation of a separated ion pair, such as dichloromethane and triflate (Scheme 1). This selectivity was switched and the 2,5
  • indentified from the reaction mixture. Though H/D exchange in pyrroles has been noted in gold-catalysed reactions [13], control reactions had shown that no H/D exchange occurred in this specific system [18][19]. There was also no interconversion between 2,4- and 2,5-isomers under the same reaction conditions
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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

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  • substituted novel pyrroline derivatives have been synthesized by this methodology and the products can be used as key intermediates in the synthesis of substituted pyrrolines, pyrroles and pyrrolidines. Keywords: 5-alkyl/aryl/heteroaryl substituted 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates; aziridine; N
  • materials in the preparation of substituted pyrroles, pyrrolines and pyrrolidines. The pyrrolines as well as pyrrolidines with substitution at the 2-position are important structural units in many natural products. A few of the natural products that contain 2-substituted pyrroline and 2-substituted
  • ]. Thus, 2-substituted pyrrolines can be converted into biologically important pyrroles or pyrrolines having alkyl/aryl/heteroaryl substitution at the 2-position (Scheme 4). To see the generality of the aziridine ring expansion reaction with electron withdrawing groups other than ester, the N
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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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  • nucleophilic oxidant in this context [40]. The gold-catalyzed intramolecular nucleophilic attack of heteroatoms on alkynes, followed by ring expansion, represents an appropriate method for the synthesis of furans and pyrroles. In 2006, Schmalz and co-workers reported a gold-catalyzed cascade reaction of
  • intermolecular nucleophilic attack to give intermediate 47, which upon cycloisomerization affords the aromatic product (Scheme 14, path b). Toste and co-workers reported an intramolecular acetylenic Schmidt reaction using azides as internal nucleophiles to give substituted pyrroles (Scheme 15) [42]. Gold
  • gold-catalyzed ring expansion of 1-oxiranyl-1-alkynylcyclopropanes [43][44]. An alternative method for obtaining disubstituted pyrroles via gold-catalyzed ring expansion was reported by Davies and co-workers who employed alkynyl aziridines 51 as intramolecular nucleophiles [45]. Ring expansion from the
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Published 07 Jun 2011

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

  • Marcus Baumann,
  • Ian R. Baxendale,
  • Steven V. Ley and
  • Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

Graphical Abstract
  • interesting but less used transformations. Review Pyrroles Pyrrole, a five-membered nitrogen containing heterocycle is present in some of the most common biologically important molecules, i.e., chlorophyll and haem. However, while the pyrrole ring is not widely represented in pharmaceutical compounds, the
  • company [3]. From structure–activity relationship (SAR) studies it was found that the addition of substituents at the 3- and 4-position of the pyrrole scaffold significantly increases potency when compared to the more classical 2,5-disubstituted pyrroles. This study culminated in the discovery of
  • proved to be less successful for more complex pyrroles of which atorvastatin was an example (Scheme 1). In order to prepare the 5-isopropylpyrrole derivative 16 a more efficient [3 + 2] cycloaddition of an acetylene component with an amido acid 13 was developed. Unfortunately, reacting ethyl
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Published 18 Apr 2011

Fluorometric recognition of both dihydrogen phosphate and iodide by a new flexible anthracene linked benzimidazolium-based receptor

  • Kumaresh Ghosh and
  • Debasis Kar

Beilstein J. Org. Chem. 2011, 7, 254–264, doi:10.3762/bjoc.7.34

Graphical Abstract
  • hydrogen bond donors and acceptors are of considerable importance. Among the different binding motifs for anions, the hydrogen bonding properties of NH groups in neutral amines [13], amides [14], ureas/thioureas [15][16], indoles [17][18][19] and pyrroles [20] as well as in guanidinium [21] and imidazolium
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Published 25 Feb 2011

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

  • Axel G. Griesbeck,
  • Marco Franke,
  • Jörg Neudörfl and
  • Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

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  • reagent on the liberated benzaldehyde. Conclusion The photocycloaddition of electronically excited carbonyl compounds to isoxazoles is clearly less effective than with other five-membered aromatic or non-aromatic heterocycles (furans, thiophenes, pyrroles, oxazoles, dihydrofurans, dihydropyrroles) [1
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Published 26 Jan 2011

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

  • Carolin Fischer and
  • Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

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  • resulted in good yields [4][26]. Copper-diamine-catalysed N-arylation facilitated the arylation of pyrroles, pyrazoles, indazoles, imidazoles, triazoles, benzimidazoles and indoles [27][28][29]. Besides aryl halides as the aryl donor, arylsiloxanes [30], arylstannanes [31], iodonium salts [32], aryl lead
  • ], benzimidazoles [40][41], sulfonamides [38], pyrroles [42] and lactams [43]. The three typical methods for N-arylation have been extensively reviewed concerning scope and limitation of these reactions [4][44][45][46][47][48]. However, the application of palladium- and copper-mediated N-arylation reactions in the
  • boronic acids containing electron-donating or weakly electron-withdrawing substituents were suitable. Pyrroles lacking a substituent in the 2-position, which is supposed to support the reaction by a chelating effect with the copper ion, did not succeed in the coupling reaction. Further disadvantages were
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Published 14 Jan 2011

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

  • Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

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  • % and are accompanied with halogenated side-products (Scheme 13). Among heterocyclic systems, pyrroles are the best substrates for reaction with trifluoromethyl-, difluorochloro- and dichlorofluoromethyl sulfenyl chlorides. Their reactivity exceeds that of benzene and its organometallic derivatives [80
  • ]. An excess of reagent gives bis-(SCF3) pyrrole derivatives as shown in Scheme 14. Condensed pyrroles also react readily with CF3SCl. Indole undergoes substitution, as expected, at the 3-position [80], while indolizine and some of its derivatives give 1,3-bis (SCF3)-substituted products, in some cases
  • -isomers [87]. Unlike pyrroles, furan, thiophene and selenophene react with CF3SCl only in the presence of catalysts. For selenophene [84] and thiophenes [85] SnCl4 is sufficient, whilst furans require more forcing conditions usually involving prolonged heating (20 h at 60 °C) and in pyridine for
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Published 18 Aug 2010

Anion receptors containing thiazine-1,1-dioxide heterocycles as hydrogen bond donors

  • Hong-Bo Wang,
  • James A. Wisner and
  • Michael C. Jennings

Beilstein J. Org. Chem. 2010, 6, No. 50, doi:10.3762/bjoc.6.50

Graphical Abstract
  • of nitrogen-based hydrogen bond donor groups such as amides [3][4], ureas [5], pyrroles/indoles/carbazoles [6][7] and sulfonamides [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] to complex the anionic targets in a topologically complementary fashion. Sulfonamides are an interesting
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Published 19 May 2010

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

  • Magnus Rueping and
  • Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

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  • uncovered by Pregosin and co-workers. The cationic Trost-type Ru(IV)-sulfonate catalyst 77 gives high regioselectivity for branched allylated arenes. As electron-rich arenes, pyrroles 75 and indole (76) can be utilized (Scheme 31) [86]. Interestingly, the addition of sulfonic acid was crucial for the high
  • indoles, thiophenes, pyrroles or furans gave the desired anti-1,1,2-triarylalkanes 110 in good yields and with high diastereoselectivities (Scheme 40B). BF3•OEt2 and TFA were used in stoichiometric amounts to promote this reaction. However, application of BF3 resulted in significantly higher reactivity
  • of indole. Pd-catalyzed synthesis of pyrroloindoles from L-tryptophane. Ru(IV)-catalyzed allylation of indole and pyrroles with unique regioselectivity. Silver(I)-catalyzed intramolecular FC-type allylation of arenes and heteroarenes. FC-type alkylations of arenes using propargyl alcohols. (A
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Published 20 Jan 2010

The first direct synthesis of β-unsubstituted meso- decamethylcalix[5]pyrrole

  • Luis Chacón-García,
  • Lizbeth Chávez,
  • Denisse R. Cacho and
  • Josue Altamirano-Hernández

Beilstein J. Org. Chem. 2009, 5, No. 2, doi:10.3762/bjoc.5.2

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  • ; calix[n]pyrrole; Results and Discussion Calix[n]pyrroles have attracted attention because of their ability to recognize anions [1][2]. To date, the calix[4]pyrroles have been studied the most, in part due to the ease with which the macrocycle can be obtained by the condensation of pyrrole with a ketone
  • catalyzed by a Brønsted-Lowry acid such as HCl or methanesulfonic acid, or a Lewis acid such as zeolites with aluminium or cobalt, BF3 or a bismuth salt [2][3][4][5]. The synthesis of calix[n]pyrroles where n > 4 has been reported for n = 5 or 6. The latter compounds have been synthesized via two routes: a
  • acetate with 40% yield [6][7]. On the other hand, β-unsubstituted calix[5]pyrroles have been obtained by two routes: a) from the corresponding meso-decamethylcalix[5]furan, via a method analogous to that reported for calix[6]pyrroles, with 1% yield; and b) directly when the macrocycle is covalently bound
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Preliminary Communication
Published 28 Jan 2009

One-pot preparation of substituted pyrroles from α-diazocarbonyl compounds

  • Fernando de C. da Silva,
  • Mauricio G. Fonseca,
  • Renata de S. Rianelli,
  • Anna C. Cunha,
  • Maria C. B. V. de Souza and
  • Vitor F. Ferreira

Beilstein J. Org. Chem. 2008, 4, No. 45, doi:10.3762/bjoc.4.45

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  • Abstract In this work an efficient one-pot synthesis of substituted pyrroles 7a–n is described, which involves the in situ formation of dihydrofurans ethyl 5-butoxy-2-methyl-4,5-dihydrofuran-3-carboxylate (4), 1-(5-butoxy-2-methyl-4,5-dihydrofuran-3-yl)ethanone (5) and 5-butoxy-4,5-dihydrofuran-3
  • wide number of review articles [15][16][17][18][19]. Due to these multiple uses and varieties of biological activities, the synthesis of this ring system has been subject of intense investigation. Danks [20] developed a high yield Paal–Knorr method of synthesis of pyrroles by the reaction between
  • hexane-2,5-dione and primary amines under microwave irradiation. Other processes including several clay-mediated synthetic variations of these classical methods also have been reported for preparing pyrroles in equal or better yields [21]. In 2001 [22] and 2004 [23], Banik and co-workers, by using the
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Published 28 Nov 2008

Total synthesis of the indolizidine alkaloid tashiromine

  • Stephen P. Marsden and
  • Alison D. McElhinney

Beilstein J. Org. Chem. 2008, 4, No. 8, doi:10.1186/1860-5397-4-8

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  • structure, including radical cyclisations [3]; nucleophilic addition to imines [5][14][15]; electrophilic alkylation of pyrroles [7][13]; alkylation of enamines [6], β-amino esters [8] and pyrrolidinyllithiums [12]; stereoselective reduction of enamines [4][9] and pyridinium salts [11]; and titanium
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Published 26 Jan 2008

Knorr- Rabe partial reduction of pyrroles: Application to the synthesis of indolizidine alkaloids

  • Brendon S. Gourlay,
  • John H. Ryan and
  • Jason A. Smith

Beilstein J. Org. Chem. 2008, 4, No. 3, doi:10.1186/1860-5397-4-3

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  • Brendon S. Gourlay John H. Ryan Jason A. Smith School of Chemistry, University of Tasmania, Hobart, Australia CSIRO Division of Molecular and Health Technologies, Bag 10, Clayton South, Victoria, Australia 10.1186/1860-5397-4-3 Abstract Background The Birch reduction of electron rich pyrroles
  • rich pyrroles. Results The partial reduction of bicyclic α-ketopyrrole derivatives has been performed under dissolving metal conditions with zinc and hydrochloric acid to give excellent yields of hexahydroindolizidines. This reduction method has been utilised for the diastereoselective synthesis of 5
  • electron density of these aromatic heterocycles inhibits the addition of an electron, the first step of a Birch reaction [2]. Donohoe has shown that the partial reduction of pyrroles is possible but this process generally requires the presence of at least two electron withdrawing groups that reduce the
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Published 15 Jan 2008

Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis

  • Roger Hunter,
  • Sophie C. M. Rees-Jones and
  • Hong Su

Beilstein J. Org. Chem. 2007, 3, No. 38, doi:10.1186/1860-5397-3-38

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  • resulted in us developing a one-pot methodology involving its in situ generation. We have recently demonstrated the applicability of N-protected-4-methoxy-2-trimethylsilyloxy pyrroles 5 to the synthesis of key intermediates for the alkaloids lepadiformine [10] and castanospermine [11] using vinylogous
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Published 03 Nov 2007

Aroylketene dithioacetal chemistry: facile synthesis of 4-aroyl- 3-methylsulfanyl- 2-tosylpyrroles from aroylketene dithioacetals and TosMIC

  • H. Surya Prakash Rao and
  • S. Sivakumar

Beilstein J. Org. Chem. 2007, 3, No. 31, doi:10.1186/1860-5397-3-31

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  • hydride in THF at rt resulted in a facile synthesis of the 4-aroyl-3-methylsulfanyl-2-tosylpyrroles 3 in good yield along with a minor amount of 4-[(4-methylphenyl)sulfonyl]-1-[(methylsulfanyl)methyl]-1H-imidazole 4. This study lead to the synthesis of 2,3,4-trisubstiuted pyrroles having 1-naphthoyl/2
  • could lead to 2,3,4-trisubstituted pyrroles having an aroyl moiety located on C-4. Von Leusen's and others have amply demonstrated that the cycloaddition of TosMIC to the alkenes having strong electron-withdrawing groups (Michael acceptors) followed by loss of TosOH provide 3,4-disubstituted pyrroles in
  • excellent yield. [8][9][10] Similarly, the reaction of TosMIC with activated alkynes afford trisubstituted pyrroles. However, the scope of pyrrole synthesis via cycloaddition of TosMIC to the "push-pull" alkenes is not well explored. We reasoned that, in the event of cycloaddition taking place between
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Published 28 Sep 2007
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