Showing papers on "Pyran published in 2016"
TL;DR: In this paper, a powerful, magnetic, supported, acid catalyst, NiFe2O4@SiO2−H3PW12O40, was prepared by chemical support of Keggin (H3pW12o40) heteropolyacid (HPA) on silica-coated NiFe 2O4 magnetic nanoparticles.
Abstract: A powerful, magnetic, supported, acid catalyst, NiFe2O4@SiO2–H3PW12O40, was prepared by chemical support of Keggin (H3PW12O40) heteropolyacid (HPA) on silica-coated NiFe2O4 magnetic nanoparticles. XRD, TEM, SEM, VSM, and FTIR confirmed that the keggin HPA is well dispersed on the surface of silica-coated NiFe2O4 magnetic nanoparticles. The magnetically recoverable catalyst could be easily recycled at least six times without significant loss of catalytic activity. After full characterization, its catalytic activity was investigated in the synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-c]pyrazole derivatives. (1) Novel silica-coated magnetic NiFe2O4 nanoparticles-supported H3PW12O40 was fabricated and characterized. (2) Recyclability of the catalyst. (3) Avoiding use of corrosive acid catalysts. (4) Green chemistry.
73 citations
TL;DR: A coumarin-spiropyran dyad with a hydrogenated pyran moiety behaving as an off-on type fluorescent receptor for rapid, selective, and sensitive detection of cyanide anion (CN(-)) in aqueous media is synthesized.
Abstract: We synthesized a coumarin–spiropyran dyad with a hydrogenated pyran moiety (2), behaving as an off–on type fluorescent receptor for rapid, selective, and sensitive detection of cyanide anion (CN–) in aqueous media. The receptor itself shows almost no fluorescence with a quantum yield < 0.01, due to the delocalization of π-electrons over the molecule. Selective nucleophilic addition of CN– to the spirocarbon of the molecule rapidly promotes spirocycle opening within only 3 min. This leads to localization of π-electrons on the coumarin moiety and exhibits strong light-blue fluorescence at 459 nm with very high quantum yield (0.52). As a result of this, the receptor facilitates rapid, selective, and sensitive fluorometric detection of CN– as low as 1.0 μM.
69 citations
TL;DR: An iron-catalyzed radical [2 + 2 + 2] annulation of benzene-linked 1,7-enynes with aldehydes with an attractive dual role, which triggers and terminates the domino cyclization.
63 citations
TL;DR: In this article, a silica-coated magnetic NiFe2O4 nanoparticle-supported Preyssler heteropolyacid (H14[NaP5W30O110]) catalyzed the synthesis of highly substituted pyran derivatives under ultrasonic irradiation at room temperature in ethanol.
Abstract: Silica-coated magnetic NiFe2O4 nanoparticle-supported Preyssler heteropolyacid (H14[NaP5W30O110]) catalyzed efficiently the synthesis of highly substituted pyran derivatives under ultrasonic irradiation at room temperature in ethanol. In comparison with conventional methods, our protocol is convenient and offers several advantages, such as shorter reaction times, higher yields, milder conditions and environmental friendliness. The catalyst can be recovered by a simple external magnet and used four times without a significant loss of catalytic activity.
44 citations
TL;DR: The reaction of pregnenolone with cyanoacetylhydrazine and ammonium acetate at 120°C gave the Knoevenagel condensation product 3, which reacted with different reagents to give thiophene, thieno[2,3-d]pyrimidine, 1,2,4-triazole and pyran derivatives.
40 citations
TL;DR: In this paper, a new and rational method for the synthesis of Fe3O4@SiO2@Si3Cl based magnetic nanoparticles with amino cobalt phthalocyanine tags (ACoPc-MNPs) was described and these were evaluated as a reusable catalyst for the one-pot synthesis of tetrahydrobenzo[b]pyran derivatives.
Abstract: A new and rational method for the synthesis of Fe3O4@SiO2@SiO2(CH)3Cl based magnetic nanoparticles with amino cobalt phthalocyanine tags (ACoPc-MNPs) was described and these were evaluated as a reusable catalyst for the one-pot synthesis of tetrahydrobenzo[b]pyran derivatives. The described reaction proceeded in high to excellent yield, with a short reaction time, and under mild and green solvent-free conditions at room temperature. The ACoPc-MNP catalyst was characterized via Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), X-ray fluorescence (XRF) analysis, energy-dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometry (VSM). Moreover, the catalyst could be easily recovered by magnetic separation and recycled 4 times without significant loss of its catalytic activity. Moreover, by this synthetic method, some novel tetrahydrobenzo[b]pyran derivatives are prepared and characterized.
39 citations
TL;DR: The structure of the newly synthesized compounds has been established on the basis of their analytical and spectral data as discussed by the authors, and the structure of these newly synthesised compounds have been established based on their spectral data.
38 citations
TL;DR: In this article, a new synthetic route for obtaining α-6-hydroxy, 6-methyl-4-enyl-2H-pyran-3-one, a useful syntheson for the preparation of biologically active compounds, was developed from the bio-based platform derivative (2,5-bis-hydroxymethylfuran) BHMF.
Abstract: A new synthetic route for obtaining α-6-hydroxy-6-methyl-4-enyl-2H-pyran-3-one, a useful synthon for the preparation of biologically active compounds, has been developed from the bio-based platform derivative (2,5-bis-hydroxymethylfuran) BHMF. The reaction occurs with good selectivity in water, under mild conditions and employing an heterogeneous recyclable acid (Amberlyst 15®) as catalyst, avoiding the use of oxidizing agents. The reaction provides access to poly-oxygenated compounds characterized by a molecular motif commonly found in many natural products.
38 citations
TL;DR: TiO2 supported gold nanoparticles with low loading are able to semihydrogenate non-fluorinated and gem-difluorinated alkynes to cis-alkenes with high selectivity, using cost-effective and easy-to-handle ammonium formate as the reductant.
36 citations
TL;DR: In this article, a mild and efficient method for the synthesis of thiochro meno[4,3b]pyran and thiopyrano[ 4,3-b] pyran derivatives using MgO nanopowders as a catalyst is described.
34 citations
TL;DR: A general protocol for the facile construction of titled derivatives via three component reaction between 3-substituted phenyl-1H-pyrazole-4-carbaldehyde, malononitrile and various Michael donors in presence of 5-mol% polystyrene supported 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (PS-TBD) was developed.
TL;DR: In this article, an efficient one-pot synthesis of benzo[b]pyrans catalyzed by vitamin B1 functionalized Fe2O3@SiO2 NPs under ultrasonic conditions is reported.
Abstract: An efficient, one-pot synthesis of benzo[b]pyrans catalyzed by vitamin B1 functionalized Fe2O3@SiO2 NPs under ultrasonic conditions is reported herein. The nano-organocatalyst was synthesized and characterized by FT-IR, TEM, EDS, powder XRD, etc. Several benzo[b]pyran derivatives were prepared with satisfactory yields and the nanocatalyst was magnetically retrieved and recycled. The salient features of this protocol include convenient work-up procedure, mild reaction conditions, easy catalyst recovery, shorter reaction time and use of green solvents. Ultrasound energy has been meticulously exploited for the synthesis of a nano-organocatalyst as well as for the preparation of several benzo[b]pyran derivatives. The biological activity of the synthesized benzo[b]pyrans were investigated and one of the derivatives was found to demonstrate profound activity in suppressing the side-effects of chlorpyrifos, an insecticide on the morphology of the external gills of the Duttaphrynus melanostictus tadpoles.
TL;DR: A method combining liquid chromatography with photodiode array detection and quadrupole time-of-flight mass spectrometry was developed to characterize components in three Glycyrrhiza species, and to expound the characteristic fragmentation behaviors in the positive ion mode.
Abstract: Flavonoids, including flavones, isoflavones, flavanones, chalcones, and isoflavans, have long been recognized as the main active ingredients in licorice. A method combining liquid chromatography with photodiode array detection and quadrupole time-of-flight mass spectrometry was developed to characterize components in three Glycyrrhiza species, and to expound the characteristic fragmentation behaviors in the positive ion mode. Based on the fragmentation patterns of reference compounds, a total of 39 compounds, including 37 flavonoid aglycones and two coumestans, were identified or tentatively identified. Besides, some common features, such as H2 O, CO, and CH2 O2 losses, together with retro-Diels-Alder fragmentation, were observed in these compounds. Furthermore, diagnostic fragmentations of C-ring cleavages and UV absorption on the skeleton groups were observed to structurally characterize flavonoid aglycones. In addition, typical losses of different substituent groups were detected: Neutral losses of 56 (C4 H8 ) and 68 Da (C5 H8 ) were yielded from a prenyl chain; neutral losses of 42 (C3 H6 ), 54 (C4 H6 ), and 70 Da (C4 H6 O) were generated by a pyran ring. Particularly, neutral losses of 18 (H2 O), 16 (CH4 ), 112 (C8 H16 ), and 98 Da (C7 H14 ) predicted a hydroxyl, a methoxyl, double prenyl chains, and a prenyl chain with a pyran ring, respectively.
TL;DR: A 14-membered heterocycle is created on the C60 cage skeleton through a multistep procedure that showed unique reactivities towards fluoride ion and copper salts.
Abstract: A 14-membered heterocycle is created on the C60 cage skeleton through a multistep procedure. Key steps involve repeated PCl5-induced hydroxylamino N−O bond cleavage leading to insertion of nitrogen atoms, and also piperidine-induced peroxo O−O bond cleavage leading to insertion of oxygen atoms. The hetero atoms form one pyrrole, two pyran, and one diazepine rings in conjunction with the C60 skeleton carbon atoms. The fullerene-based macrocycle showed unique reactivities towards fluoride ion and copper salts.
01 Jan 2016
TL;DR: Pyran copolymer, a known immunostimu- lator, was found to be a potent inhibitor of purified DNA polymerase (deoxynucleosidetriphosphate: DNA deoxynu- cleotidyltransferase; EC 2.7) isolated from avian myeloblastosis virus.
Abstract: Pyran copolymer, a known immunostimu- lator, was found to be a potent inhibitor of purified DNA polymerase (deoxynucleosidetriphosphate: DNA deoxynu- cleotidyltransferase; EC 2.7.7.7) isolated from avian myeloblastosis virus. Unlike other inhibitors, pyran showed unique features of inhibition. It interacts with the polymerase at a region other than the template site. The inhibitory effect was overcome only by excess enzyme and not affected by excess template. The degree of inhibition was not template specific for the templates tested: 70S RNA from avian myeloblastosis virus, synthetic hybrid poly(rA) oligo(dT)lo, synthetic copolymer poly(dA-dT), and activated calf-thymus DNA. The observed rate of in- hibition by pyran was shown to vary with the different polymerases tested. Inhibition was shown with all on- cornaviral polymerases and, to a lesser extent, with mammalian polymerases. However, two of the three bac- terial polymerases, by contrast, showed a marked activa- tion.
TL;DR: The first organocatalytic, enantioselective Michael/cyclization cascade reaction sequence between α-cyano ketones and isatylidene malononitriles was reported in this paper.
TL;DR: In this article, a class of novel pyran-based chromophores has been synthesized and characterized for what concerns their optical and electrochemical properties, and the electronic structures were investigated in details by means of DFT theoretical computations.
TL;DR: A review of the reactivity of dehydroacetic acid can be found in this article, where the structure of the title compound was investigated and the reaction mechanisms of the reaction were discussed.
TL;DR: In this paper, multicomponent reactions between β-ketoesters and benzaldehydes for the synthesis of 4 H -pyran derivatives promoted by niobium pentachloride (NbCl 5 ) were carried out, providing good yields and reasonable reaction times under mild reaction conditions.
TL;DR: This protocol paves the way for further investigation of alkynyl acylammoniums as 3C synthons for construction of diverse heterocyclic skeletons.
TL;DR: In this paper, the optical antipodes of the cis-isomers of osmundalactone, a hydroxypyranone natural product and core structure of the angiopterlactones, have been synthesized from acetylfuran in only three steps through a redox cascade utilizing oxidoreductases and transition metal catalysis in a concerted fashion.
Abstract: Both optical antipodes of the cis-isomers of osmundalactone, a hydroxypyranone natural product and core structure of the angiopterlactones, have been synthesized from acetylfuran in only three steps through a redox cascade utilizing oxidoreductases and transition metal catalysis in a concerted fashion. The key step in this fully catalytic strategy is the enzyme-mediated Achmatowicz reaction via selective furan oxygenation to furnish the pyran core structure.
TL;DR: In this paper, two new pyran- or coumarin-substituted thiazolyl-pyrazole-chromen-2-one derivatives 10a-10d and 11a-11d were efficiently synthesized under environmentally friendly reaction conditions through a convenient one-pot multicomponent reaction of a heterocyclic bromoacetyl derivative 3 or 4 with thiosemicarbazide and a substituted 3-(aceto-acetyl)coumarin derivative 5a-5d in anhydrous ethanol.
TL;DR: This FeCl3-catalyzed transformation of aryl- and alkyl β-diketones enables synthetic access to functionalized pyran core structures incorporated in many natural products and biologically active target structures.
TL;DR: Five new pyran rings containing polyketides, penicipyrans A–E (1–5), together with the known pestapyrone A (6), were isolated from the saline soil-derived Penicillium raistrickii by interpretation of NMR and HRESIMS data.
Abstract: Five new pyran rings containing polyketides, penicipyrans A-E (1-5), together with the known pestapyrone A (6), were isolated from the saline soil-derived Penicillium raistrickii. Their structures were determined by interpretation of NMR and HRESIMS data. The absolute configurations of compounds 4 and 5 were established by the modified Mosher's method and single-crystal X-ray diffraction analysis, respectively. These compounds possessed high structural diversity including two α-pyrones (1, 2), three isocoumarins (3, 4, 6), and one dihydropyran derivative (5). Among them, Compound 5 exhibited cytotoxicity against HL-60 and K562 cell lines with IC50 values of 4.4 and 8.5 μM, respectively.
TL;DR: In this article, the detailed mechanism of thermal ring opening reactions of 2H-pyran and 2H 1,4-oxazine systems in a broad range of spiropyran derivatives was studied by density functional methods.
Abstract: The detailed mechanism of thermal ring opening reactions of 2H-pyran and 2H-1,4-oxazine systems in a broad range of spiropyran and spiro-1,4-oxazine derivatives was studied by density functional methods (PBE0/6-311+G(d,p)). The study revealed mechanistic features and the dependence of activation parameters of this electrocyclic reaction on the steric and electronic properties of spiroconjugated fragments of the studied compounds.
TL;DR: In this paper, a Pot, Atom and Step Economics (PASE) potassium fluoride catalyzed multicomponent reaction of isatins, malononitrile and 4-hydroxy-6-methyl-2H-pyran-2-one results in efficient formation of substituted spirooxindole-3,4′-polypyrano[4,3-b]pyrans in 92-96% yields.
Abstract: Abstract Fast (3 min) pot, atom and step economics (PASE) potassium fluoride catalyzed multicomponent reaction of isatins, malononitrile and 4-hydroxy-6-methyl-2H-pyran-2-one results in efficient formation of substituted spirooxindole-3,4′-pyrano[4,3-b]pyrans in 92–96% yields. The developed ‘on-solvent’ approach to the substituted spirooxindole-3,4′-pyrano[4,3-b]pyrans – the pharmacologically perspective substances with known antiviral, antileishmanial, anticonvulsant and anti-HIV activities – is beneficial from the viewpoint of diversity-oriented large-scale processes and represents fast and environmentally benign synthetic concept for the multicomponent reactions strategy.
TL;DR: Anti-proliferative cell activity against cancer cell lines of the most potent compounds showed that compounds 5f and 10e achieved the highest activities among the tested compounds.
Abstract: The multi-component reaction of 2-acetylthiophene with aromatic aldehydes and either malononitrile or ethyl cyanoacetate gave the pyran derivatives 4a–4f and pyridine derivatives 5a–5f. On the other hand, the reaction of the 2-acetylthiophene with elemental sulfur and either malononitrile or ethyl cyanoacetate gave the thiophene derivatives 6a and 6b; respectively. Compounds 6a and 6b underwent a series of heterocyclic reactions to give thiazole and thiophene derivatives. All the products were assessed for antitumor activity towards human cancer human gastric cancer (NUGC and HR), human colon cancer (DLD1), human liver cancer (HA22T and HEPG2), human breast cancer (MCF), nasopharyngeal carcinoma (HONE1) cell lines. Compounds 4e, 4f, 5e, 5f, 7b, 8b, 10e, 10f, 11e, 11f, 14d-f, 15d-f, 16a,b and 18b exhibited optimal cytotoxic effect against cancer cell lines, with IC50’s in the nM range. Moreover, 7b, 10e, 14d, 15e and 16b showed no toxicity against shrimp larvae. Anti-proliferative cell activity against cancer cell lines of the most potent compounds showed that compounds 5f and 10e achieved the highest activities among the tested compounds.
TL;DR: Titanium dioxide nanoparticles were introduced as a new and efficient heterogeneous catalyst for the synthesis of pyran's annulated heterocyclic systems via three-component reaction.
Abstract: Titanium dioxide nanoparticles were introduced as a new and efficient heterogeneous catalyst for the synthesis of pyran’s annulated heterocyclic systems via three-component reaction. The reaction was carried out between various aldehydes, malononitrile, and cyclic CH-acids in H2O as a green solvent at 50 °C during 10 h. This reaction gave pyrans containing heterocyclic compounds including nineteen derivatives in good yields. Titanium dioxide nanoparticles were recycled and reused for six times without significant decrease in the catalyst amount and efficiency. This approach is very efficient, economical, and environmentally benign process since titanium dioxide is a cheap, available, non-toxic, and recyclable catalyst.
TL;DR: In this article, the effects of catalyst type (sulfuric acid, Amberlyst 15, p-toluenesulfonic acid, and p-dodecylbenzenes sulfonic acid) and addition of water on the preparation of 2-isobutyl-4methyltetrahydro-2H-pyran-4-ol by Prins cyclization were studied.
Abstract: The effects of catalyst type (sulfuric acid, Amberlyst 15, p-toluenesulfonic acid, and p-dodecylbenzenesulfonic acid) and of addition of water on the preparation of 2-isobutyl-4-methyltetrahydro-2H-pyran-4-ol by Prins cyclization were studied. It was discovered that in the absence of added water the amphiphilic character of the acid had the main effect and that organic acids were unsuitable for preparation of this compound. From the perspective of the ratio of the amount of the desired product to that of dihydropyrans, after addition of water the results obtained by use of p-toluenesulfonic acid (ratio 3.5, selectivity 67 %) were comparable with those obtained by use of sulfuric acid and were better than those obtained by use of Amberlyst 15 (ratio 2.3, selectivity 68 %). A detailed study of the mechanism confirmed that addition of water to the double bonds of dihydropyrans does not occur.
TL;DR: An atom-economic reaction sequence to 6-substituted 2-pyrones was developed starting from furfuryl alcohol, a renewable resource made from bran or bagasse, and aldehydes, utilizing a thermal rearrangement of cyclopentadienone epoxides as key step.
Abstract: An atom-economic reaction sequence to 6-substituted 2-pyrones was developed starting from furfuryl alcohol, a renewable resource made from bran or bagasse, and aldehydes, utilizing a thermal rearrangement of cyclopentadienone epoxides as key step. Derivatives bearing a hydroxyalkyl side chain could be enzymatically resolved, providing access to enantiomerically pure 2-pyrones, or converted to alkenyl-substituted 2-pyrones such as naturally occurring sibirinone, (E)-6-(pent-1-en-1-yl)-2H-pyran-2-one, and (E)-6-(hept-1-en-1-yl)-2H-pyran-2-one.