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Search for "oxazole" in Full Text gives 77 result(s) in Beilstein Journal of Organic Chemistry.

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

  • Paul Hommes and
  • Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

Graphical Abstract
  • formed. Instead, we isolated the trisubstituted oxazole derivative 6 in 55% yield. The scope of this reaction has not been studied by us, however it is known in the literature that enamides can undergo related oxidative cyclizations to oxazoles in the presence of the reagent cocktail employed or under
  • methoxylation of compound 3a we unexpectedly observed the formation of the 5-acetyl-substituted oxazole derivative 6. However, precursor 3i was smoothly available from acetylacetone 1a. It could smoothly be transformed into the desired bipyridine derivative 4i, but also into the related pyrimidine and
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Published 09 Jun 2016

Marine-derived myxobacteria of the suborder Nannocystineae: An underexplored source of structurally intriguing and biologically active metabolites

  • Antonio Dávila-Céspedes,
  • Peter Hufendiek,
  • Max Crüsemann,
  • Till F. Schäberle and
  • Gabriele M. König

Beilstein J. Org. Chem. 2016, 12, 969–984, doi:10.3762/bjoc.12.96

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  • Na a174 yielded a new class of halogenated pyrrole–oxazole compounds 14–18 (Figure 8). Pyrronazols A (14), A2 (15) and B (16), synthesized by Ari7, additionally include an α-pyrone moiety [48]. This is worth noting, since the non-cyclic alkyl moiety in the pyrronazols C1 (17) and C2 (18), found in
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Published 13 May 2016

Antibiotics from predatory bacteria

  • Juliane Korp,
  • María S. Vela Gurovic and
  • Markus Nett

Beilstein J. Org. Chem. 2016, 12, 594–607, doi:10.3762/bjoc.12.58

Graphical Abstract
  • exhibit an unusual molecular architecture featuring two oxazole rings connected by a two-carbon tether and a terminal 2,4-pentadienylamine moiety. Feeding experiments as well as biosynthetic reasoning indicated that the siphonazoles originate from a mixed PKS/NRPS pathway [125]. Both bisoxazoles were
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Published 30 Mar 2016

Recent advances in copper-catalyzed C–H bond amidation

  • Jie-Ping Wan and
  • Yanfeng Jing

Beilstein J. Org. Chem. 2015, 11, 2209–2222, doi:10.3762/bjoc.11.240

Graphical Abstract
  • functionalization with nitrogen nucleophiles, including amides, sulfonamides and primary arylamines. In addition, the oxazole-based DG could be easily deprotected to provide the corresponding benzoic acid 44 by heating in EtOH in the presence of KOH (Scheme 13). As another easily available N-containing aromatic
  • , was reported by Dai and Yu et al. [83]. As outlined in Scheme 26, the presence of the oxazole-based DG was found to be the main factor in tuning the selective formation of 101. Related control experiments suggested that the formation of intermediate 102 acquired from the copper-catalyzed C(sp2)–C(sp3
  • for lactam synthesis. Copper-catalyzed amidation/sulfonamidation of aryl C–H bonds. C–H amidation of pyridinylbenzenes and indoles. Mechanism of the Cu-catalyzed C2-amidation of indoles. Copper-catalyzed, 2-phenyl oxazole-assisted C–H amidation of benzamides. DG-assisted amidation/imidation of indole
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Published 17 Nov 2015

Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyl)oxazoles

  • Kandasamy Rajaguru,
  • Arumugam Mariappan,
  • Rajendran Suresh,
  • Periasamy Manivannan and
  • Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2015, 11, 2021–2028, doi:10.3762/bjoc.11.219

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  • . This is illustrated with one reaction in which 3 was subjected to treatment with triphenylphosphine in the presence of iodine and triethylamine in dry dichloromethane at room temperature (Scheme 4) [34][35]. As expected, compounds 3 are converted to 2,4,5-substituted oxazole 7 regiospecifically in good
  • investigation of the structure of 8a indicated that the compound is a highly substituted 2-(trifluoromethyl)oxazole. With different α-azidochalcones, differently substituted 8 have been isolated (Figure 5). It should be mentioned that oxazole formation is observed only at low temperature with trifluoroacetic
  • , the solvent was removed in vacuo, and the residue was directly purified by column chromatography on silica gel (hexane/ethyl acetate 9:1) to yield oxazole 7. Synthesis of 8: In a dry two neck round bottom reaction vessel equipped with a calcium guard tube and a magnetic bar, α-azidochalcone (1.0 equiv
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Published 29 Oct 2015

Selected synthetic strategies to cyclophanes

  • Sambasivarao Kotha,
  • Mukesh E. Shirbhate and
  • Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

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Published 29 Jul 2015

A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones

  • Marcelo Isidoro P. Reis,
  • Vinícius R. Campos,
  • Jackson A. L. C. Resende,
  • Fernando C. Silva and
  • Vitor F. Ferreira

Beilstein J. Org. Chem. 2015, 11, 1235–1240, doi:10.3762/bjoc.11.137

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  • naphthoquinones (Figure 1) such as naphtho[2,3-b]furan [5][6][7][8][9][10][11][12][13][14], naphtho-pyran [15][16][17][18], benzo[f]indole [19][20][21][22][23][24], benzo[g]quinolone [25], benzo[b]carbazole [26], naphtho[2,3-b]thiophene [27][28][29][30][31][32][33] and naphtho[2,3-b]]oxazole [34] have been
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Published 22 Jul 2015

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

  • Nikolai V. Rostovskii,
  • Mikhail S. Novikov,
  • Alexander F. Khlebnikov,
  • Galina L. Starova and
  • Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

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  • -azabicyclo[3.2.1]oct-2-ene and/or 5,7-dioxa-1-azabicyclo[4.3.1]deca-3,8-diene-2-one derivatives. According to DFT calculations (B3LYP/6-31+G(d,p)), the cycloaddition can involve two modes of nucleophilic attack of the dihydroazireno[2,1-b]oxazole intermediate on acetyl(methyl)ketene followed by aziridine
  • the mechanism of trapping of dihydroazireno[2,1-b]oxazole intermediates by acetyl(methyl)ketene were investigated by the DFT method. Results and Discussion Rhodium(II) carbenoids generated from α-diazoketones or 2-diazo-1,3-diketones react with various nitrogen-containing compounds, such as amines [16
  • involves the 1,5-cyclization of azirinium ylide 9f–h to dihydroazireno[2,1-b]oxazole 10f–h followed by cycloaddition of the latter to ketene 12 to give two regioisomeric adducts 6f,g and 7f–h (Scheme 3). Several examples of the 1,5-cyclization of azomethine ylides bearing an α-keto group into oxazole
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Published 02 Mar 2015

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

  • Igor B. Krylov,
  • Vera A. Vil’ and
  • Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

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  • solvent mixture at 100–110 °C for 18 h. The oxazole moiety also acts as the directing group in the acetoxylation of alkyl groups with Pd(OAc)2/AcOOt-Bu or Pd(OAc)2/lauroyl peroxide oxidative systems; in these reactions acetic anhydride served as the source of the acetoxy groups [88]. Recently, Cu(OAc)2
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Published 20 Jan 2015

Recent advances in the electrochemical construction of heterocycles

  • Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

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  • solution and dichloromethane is employed as electrolyte. The method features attractive yields (70–95%) and a broad scope with regard to substitution on the phenylene moiety (R1 and R2) and on the oxazole unit (R3). 2 Intermolecular cyclizations 2.1 Cycloadditions with anodically generated intermediates A
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Published 03 Dec 2014

Photochemical approach to functionalized benzobicyclo[3.2.1]octene structures via fused oxazoline derivatives from 4- and 5-(o-vinylstyryl)oxazoles

  • Ivana Šagud,
  • Simona Božić,
  • Željko Marinić and
  • Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2014, 10, 2222–2229, doi:10.3762/bjoc.10.230

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  • .10.230 Abstract Novel cis/trans-4- and cis/trans-5-(2-vinylstyryl)oxazoles have been synthesized by Wittig reactions from the diphosphonium salt of α,α’-o-xylene dibromide, formaldehyde and 4- and 5-oxazolecarbaldehydes, respectively. In contrast, trans-5-(2-vinylstyryl)oxazole has been synthesized by
  • )oxazole small quantities of electrocyclization product, 4-(1,2-dihydronaphthalen-2-yl)oxazole, are isolated and spectroscopically characterized. Keywords: bicyclo[3.2.1]octane; intramolecular photocycloaddition; oxazole; styryl; vinyl; Introduction The bicyclo[3.2.1]octane skeleton is the basic
  • ] and sydnones [11][12][13], as routes to polycyclic compounds, we turned our attention to oxazole derivatives. The oxazole structure is commonly found in natural products and pharmaceuticals [14][15][16][17] and is applied in useful reagents and intermediates in organic synthesis [18][19][20][21][22
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Published 18 Sep 2014

Isoxazolium N-ylides and 1-oxa-5-azahexa-1,3,5-trienes on the way from isoxazoles to 2H-1,3-oxazines

  • Alexander F. Khlebnikov,
  • Mikhail S. Novikov,
  • Yelizaveta G. Gorbunova,
  • Ekaterina E. Galenko,
  • Kirill I. Mikhailov,
  • Viktoriia V. Pakalnis and
  • Margarita S. Avdontceva

Beilstein J. Org. Chem. 2014, 10, 1896–1905, doi:10.3762/bjoc.10.197

Graphical Abstract
  • very low activation barriers (0.2–1.5 kcal/mol) to give (3Z)-1-oxa-5-azahexa-1,3,5-trienes. This is expected, because the oxazole N–O bond is very weak and the reaction is pseudopericyclic [21][22]. The calculated low thermodynamic and kinetic stabilities of the isoxazolium ylides (Figure 1) give only
  • )] computed at DFT B3LYP/6-31G(d) level. Energy profiles for the transformations of (3Z)-1-oxa-5-azahexa-1,3,5-triene D and oxazines E derived from (methoxycarbonyl)phenylcarbene or di(methoxycarbonyl)carbene and oxazole A. Relative free energies [kcal/mol, 298 K, CH2Cl2 (PCM)] computed at DFT B3LYP/6-31G(d
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Published 14 Aug 2014

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

  • Gijs Koopmanschap,
  • Eelco Ruijter and
  • Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

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  • afforded the final (R)-bacillamide C in 6% yield over three steps (ee 94%). Oxazoles The oxazole unit has been applied in different bioactive marine natural products [110]. The group of Zhu reported a Ugi 3-CR to a small library of 2,4,5-trisubstituted oxazole-containing peptide-like structures from
  • bifunctional α-isocyanoacetamides (Scheme 43) [111][112]. A plausible mechanism for this reaction involves the formation of 141, that after tautomerization, cyclizes to the oxazole product 143. It is noteworthy, that this reaction proceeds without the addition of a carboxylic acid because amino-oxazoles are
  • unstable under acidic conditions. In total, six different aldehydes, twelve amines and three isocyanides yielded the corresponding desired oxazole mimics 143 in good yields (60–96%), however, the products were obtained as racemates even when the reaction was performed with chiral isocyanides. Some
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Published 04 Mar 2014

Silver and gold-catalyzed multicomponent reactions

  • Giorgio Abbiati and
  • Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

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  • reaction with the chloride ion released during the initial imine acylation. Finally, a combination between Brønsted acid and metal catalysis, promote the isomerization of V to oxazole 21. It is noteworthy, that the gold catalyst seemed to be essential only for the formation of the gold-acetylide
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Published 26 Feb 2014

Total synthesis and cytotoxicity of the marine natural product malevamide D and a photoreactive analog

  • Werner Telle,
  • Gerhard Kelter,
  • Heinz-Herbert Fiebig,
  • Peter G. Jones and
  • Thomas Lindel

Beilstein J. Org. Chem. 2014, 10, 316–322, doi:10.3762/bjoc.10.29

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  • 13C NMR signals of oxazole C-5 (10 Hz) and C-4 (6.2 Hz). To the best of our knowledge, this is only the second time that a peptide-derived oxazol-5-ylphosphate has been characterized. Earlier, Boyd and co-workers had converted an oxazolone to an oxazolyl phosphate by treatment with excess diphenyl
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Published 03 Feb 2014

New tridecapeptides of the theonellapeptolide family from the Indonesian sponge Theonella swinhoei

  • Annamaria Sinisi,
  • Barbara Calcinai,
  • Carlo Cerrano,
  • Henny A. Dien,
  • Angela Zampella,
  • Claudio D’Amore,
  • Barbara Renga,
  • Stefano Fiorucci and
  • Orazio Taglialatela-Scafati

Beilstein J. Org. Chem. 2013, 9, 1643–1651, doi:10.3762/bjoc.9.188

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  • oxazole or thiazole rings) [10], papuamides (HIV inhibitory macrocyclic depsipeptides) [11], polytheonamides (cytotoxic linear polypeptides) [12], cyclotheonamides (thrombin and serine protease inhibitors) [13], perthamides (anti-inflammatory cyclopeptides) [14][15], solomonamides [16] and
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Published 13 Aug 2013

Synthesis and physicochemical characterization of novel phenotypic probes targeting the nuclear factor-kappa B signaling pathway

  • Paul M. Hershberger,
  • Satyamaheshwar Peddibhotla,
  • E. Hampton Sessions,
  • Daniela B. Divlianska,
  • Ricardo G. Correa,
  • Anthony B. Pinkerton,
  • John C. Reed and
  • Gregory P. Roth

Beilstein J. Org. Chem. 2013, 9, 900–907, doi:10.3762/bjoc.9.103

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  • cell line and >400-fold selective over both the NF-κB activation in HEK 293T cells and against TNFα-mediated NF-κB activation. In comparison, the second oxazole-based probe 12 is also potent (0.2 μM) in the 697 pre-B cell line and >400-fold selective over both the NF-κB activation in HEK 293T cells and
  • 4-ethoxybenzaldehyde was condensed with diacetyl monoxime under acidic conditions. The resulting oxazole N-oxide 9 was converted to the chloromethyloxazole 10 via selective chlorination with phosphorous oxychloride in good yield. Addition of thioglycolic acid led to the carboxylic acid 11, which was
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Published 08 May 2013

Synthesis of 5-(ethylsulfonyl)-2-methoxyaniline: An important pharmacological fragment of VEGFR2 and other inhibitors

  • Miroslav Murár,
  • Gabriela Addová and
  • Andrej Boháč

Beilstein J. Org. Chem. 2013, 9, 173–179, doi:10.3762/bjoc.9.20

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  • sodium salt C was subsequently converted to the hydrochloride salt of 3-amino-4-hydroxybenzene-1-sulfonyl chloride (D) by treatment with thionyl chloride at room temperature. The amino group of D was protected in the form of a 2-methylbenzo[d]oxazole-5-sulfonyl chloride (E) by reaction of D with (EtO)3CH
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Published 25 Jan 2013

Engineering of indole-based tethered biheterocyclic alkaloid meridianin into β-carboline-derived tetracyclic polyheterocycles via amino functionalization/6-endo cationic π-cyclization

  • Piyush K. Agarwal,
  • Meena D. Dathi,
  • Mohammad Saifuddin and
  • Bijoy Kundu

Beilstein J. Org. Chem. 2012, 8, 1901–1908, doi:10.3762/bjoc.8.220

Graphical Abstract
  • antagonistic [4] and antitopoisomerase-I activities [5][6][7][8][9][10][11][12][13][14][15][16]. The presence of a heterocyclic ring at the position 3 of the indole represents an important class of marine alkaloids, such as oxazole (martefragin [17], amazol [18]), imidazole (topsentins [19][20] and
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Published 08 Nov 2012

Parallel solid-phase synthesis of diaryltriazoles

  • Matthias Wrobel,
  • Jeffrey Aubé and
  • Burkhard König

Beilstein J. Org. Chem. 2012, 8, 1027–1036, doi:10.3762/bjoc.8.115

Graphical Abstract
  • , 4.25; N, 23.75. Terphenyl scaffold 1 [13][14]; oxazole-pyridazine-piperazine 2 [14][15] and aryl-triazoles 3 and 4 [15][16] as α-helix mimetics. Synthesis of azido-functionalized resins 7 and 9. Copper-catalyzed [2 + 3] cycloadditions of resin-bound azide 7 with five terminal alkynes. Copper-catalyzed
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Published 06 Jul 2012

Identification and isolation of insecticidal oxazoles from Pseudomonas spp.

  • Florian Grundmann,
  • Veronika Dill,
  • Andrea Dowling,
  • Aunchalee Thanwisai,
  • Edna Bode,
  • Narisara Chantratita,
  • Richard ffrench-Constant and
  • Helge B. Bode

Beilstein J. Org. Chem. 2012, 8, 749–752, doi:10.3762/bjoc.8.85

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  • intermediates were also investigated revealing interesting biological activities for several compounds despite their overall simple structures. Keywords: insecticidal activity; labradorin; oxazole; Pseudomonas; secondary metabolite; Findings During our search for novel natural products from entomopathogenic
  • known oxazole derivatives labradorin 1 (3, 241.1 m/z [M + H]+, C15H16N2O), labradorin 2 (4, 255.2 m/z [M + H]+, C16H18N2O) and pimprinaphine (5, 275.1 m/z [M + H]+, C18H14N2O) (Figure 1) [8][9]. Detailed analysis of the HPLC–MS data showed WS-30581 A (6, 227.1 m/z [M + H]+, C14H14N2O) [10] as an
  • additional oxazole derivative, but which was only produced in minute amounts. WS-30581 A (6) was identified by comparing the retention time and the MS fragmentation (Supporting Information File 1, Figure S2) of the product contained in the extract, with a synthesized compound. All oxazoles showed a
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Published 18 May 2012

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

  • Jiří Kulhánek and
  • Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

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  • shifted CT bands (λmax), the lowest frequency of CN stretch (23b), and the highest calculated average second-order polarizabilities β within the studied series of compounds 21–26. The nonlinear optical properties of donor- and acceptor-substituted five-membered heterocycles, such as imidazole, oxazole
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Published 05 Jan 2012

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

  • Cécile Verrier,
  • Pierrik Lassalas,
  • Laure Théveau,
  • Guy Quéguiner,
  • François Trécourt,
  • Francis Marsais and
  • Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

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  • direct (hetero)arylation of (hetero)arenes is an attractive alternative to traditional Kumada, Stille, Negishi and Suzuki–Miyaura cross-coupling reactions, notably as it avoids the prior preparation and isolation of (hetero)arylmetals. Developments of this methodology in the oxazole series are reviewed
  • in this article. Methodologies, selectivity, mechanism and future aspects are presented. Keywords: ate complex; catalytic direct arylation; mechanism; oxazole; selectivity; transition-metal catalysis; Introduction Deprotonative metalation of aromatics is widely used as a powerful method for
  • the ring-close oxazole, a trend that is evidenced by 1H NMR spectroscopy and attributed to the strong covalent carbon–zinc bond along with the zinc’s low oxophilicity, and this thus allows subsequent palladium-catalyzed Negishi cross-coupling [31][32][33]. This first, highly efficient, stoichiometric
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Published 29 Nov 2011

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

  • Benan Kilbas and
  • Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

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  • -3,3a,5a,6,6a,6b-hexahydro-2H-cyclopropa[3,4]benzo[1,2-d][1,3]oxazole-6-carboxylate (9): Tris(dibenzylideneacetone)dipalladium chloroform complex (0.2 g, 193.6 mmol) was dissolved in freshly distilled THF (20 mL) under a nitrogen atmosphere. Triisopropyl phosphite (1.6 mL) in THF (5 mL) was then added
  • , 11.75. Found: C, 53.21; H, 4.46; N, 7.79; S, 11.91. rel-3aR,5aR,6R,6aS,6bS-2-Oxo-3-tosyl-3,3a,5a,6,6a,6b-hexahydro-2H-cyclopropa[3,4]benzo[1,2-d][1,3]oxazole-7-exo-carbonitril (17): Biscarbamate 16 (1.00 g, 1.83 mmol) was reacted with freshly prepared Pd-complex as described above. The product was
  • , 58.17; H, 4.27; N, 8.48; S, 9.71. Found: C, 58.13; H, 4.31; N, 8.41; S, 9.3. rel-3aR,5aR,6R,6aS,6bS-2-Oxo-3-tosyl-3,3a,5a,6,6a,6b-hexahydro-2H-cyclopropa[3,4]benzo[1,2-d][1,3]oxazole-7-endo-carbonitril (20): Biscarbamate 16 (1.00 g, 1.83 mmol) was reacted with freshly prepared Pd-complex as described
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Published 24 Feb 2011

Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules

  • Matthias Lehmann and
  • Jens Seltmann

Beilstein J. Org. Chem. 2009, 5, No. 73, doi:10.3762/bjoc.5.73

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  • recently suggested by a theoretical work from Vanakaras [35], in which three different uniaxial and biaxial nematic phases based on aggregates or clusters have been proposed. The model is further supported by results obtained from a bent-shaped oxazole derivative, which forms polar clusters in the nematic
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Published 04 Dec 2009
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