Search results for "Conjugated"

showing 10 items of 288 documents

nBuLi-Mediated hydrophosphination: a simple route to valuable organophosphorus compounds

2010

A straightforward synthesis of homoallyl- and allylphosphanes has been developed using nBuLi-mediated hydrophosphination of conjugated dienes. In all the cases the phosphorus atom of the reacting phosphane attacked the sterically less demanding side of the diene exclusively. In addition, high regioselectivities towards 1,2- or 1,4-addition products were observed depending on the nature of the dienes. This hydrophosphination reaction was extended to a variety of substrates such as styrene derivatives, alkynes and 1,3,5-cycloheptatriene. The structures of three hydrophosphination products were confirmed by X-ray diffraction studies.

Steric effectsligand designDieneAlkyneConjugated system010402 general chemistryalkynes01 natural sciencesChemical synthesisStyrenechemistry.chemical_compound[ CHIM.ORGA ] Chemical Sciences/Organic chemistryhydrophosphinationOrganic chemistryPhysical and Theoretical ChemistryphosphorusComputingMilieux_MISCELLANEOUSchemistry.chemical_classificationalkenes010405 organic chemistryAlkene[CHIM.ORGA]Chemical Sciences/Organic chemistryOrganic ChemistryRegioselectivity0104 chemical scienceschemistry
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Enantioselective Synthesis of Pyrrolizidinone Scaffolds through Multiple-Relay Catalysis

2020

A triple-tandem protocol for the synthesis of the pyrrolizidinone skeleton has been devised. It involves a cross metathesis-intramolecular aza-Michael reaction-intramolecular Michael addition tandem sequence, starting from N-pentenyl-4-oxo-2-alkenamides and conjugated ketones. In the presence of two cooperative catalysts, namely the second-generation Hoveyda-Grubbs catalyst and (R)-TRIP-derived BINOL phosphoric acid, this multiple-relay catalytic process takes place in good yields and outstanding levels of diastero- and enantioselectivity with the simultaneous generation of three contiguous stereocenters.

Tandem010405 organic chemistryOrganic ChemistryEnantioselective synthesisSequence (biology)Conjugated system010402 general chemistry01 natural sciencesBiochemistryCombinatorial chemistry0104 chemical sciencesCatalysisStereocenterchemistry.chemical_compoundchemistryMichael reactionPhysical and Theoretical ChemistryPhosphoric acidOrganic Letters
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Rapid and eco-friendly synthesis of graphene oxide-silica nanohybrids

2014

The increasing interest in Graphene oxide (GO) is due to many issues: the presence of both sp2-conjugated atoms and oxygen-containing functional groups provides a strong hydrophilicity and the possibility to further functionalize it with other molecules (i.e. π-π interactions covalent attachment etc.) [1]. Furthermore since the GO is biocompatible and noncytotoxic many studies have been recently focused on the development of GO-based nanodevices for bioimaging DNA detection drug delivery. Due to their low cytotoxicity and large internal surface area silica nanoparticles have been taken into account as promising material for biolabeling and drug loading/delivery. Particular consideration has recently been demonstrated for GO-silica composites because of the potentialities for electrical applications their chemical inertia and stability toward ions exposure. The possibility to combine the extraordinary properties of GO and silica offers several advantages for the realization of nanoprobes for biological applications and of biosensor [12]. The strategy for the fabrication of GO-nanosilica nanohybrids can be schematized as follows: (i) synthesis of GO by oxidizing graphite powder with the method described by Marcano et al. [3] (ii) Preparation of oxygen-loaded silica nanoparticles by thermal treatments in controlled atmosphere in order to induce high NIR emission at 1272 nm from high purity silica nanoparticles. (iii) preparation of GrO-silica nanohybrid films via rapid solvent casting in water. The nanohybrids were tested by XPS FTIR Raman analysis UV photoluminescence analysis TGA Zeta potential measurements electrical tests AFM and SEM. Several nanohybrids were prepared by combining two different typologies of GO and two different samples of silica.
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Polymorphism-Triggered Reversible Thermochromic Fluorescence of a simple 1,8-Naphthyridine

2013

The fluorescent behavior in the solid state of a naphthyridine-based donor–acceptor heterocycle is presented. Synthesized as a crystalline blue-emissive solid (Pbca), the compound can easily be transformed in its P21/c polymorphic form by heating. The latter material shows blue to cyan emission switching triggered by a reversible thermally induced phase transformation. This fact, the reversible acidochromism, and the strong anisotropic fluorescence of the compound in the solid state, account for the potential of 1,8-naphthyridines as simple and highly tunable organic compounds in materials science.

ThermochromismnaphthyridinesChemistryStereochemistryfield-effect transistorsSolid-statefood and beverageschemical sensorsGeneral ChemistrylassersCondensed Matter PhysicsFluorescenceCombinatorial chemistrysolid-state fluorescencePolymorphism (materials science)emissionconjugated polymersluminescencepackingGeneral Materials ScienceLuminescencephotocromism
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Synthesis and characterization of polyene chromophores with hydroxyl functionalization

2008

Abstract Eight hydroxyl functionalized donor–acceptor polyene chromophores 3–10 were synthesized and characterized. Knoevenagel condensation reaction of aromatic polyenals with 2-cyanoacetamide derivatives was utilized to synthesize chromophores with all-E configuration. Chromophores of this kind can be attached covalently to polymers or functionalized with dendrons in order to tune the properties. The structures of the molecules were verified by 1H NMR, 13C NMR, ESI-TOF mass spectrometry and UV–vis measurements. Reduced bond-length alternation of the molecules in DMSO-d6 solution were observed by calculating the average difference of the vicinal coupling constants between adjacent CH CH an…

Thermogravimetric analysischemistry.chemical_compoundChemistryCovalent bondProcess Chemistry and TechnologyGeneral Chemical EngineeringProton NMRMoleculeKnoevenagel condensationConjugated systemChromophorePolyenePhotochemistryDyes and Pigments
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Milk quality as affected by grazing time of day in Mediterranean goats.

2008

We evaluated the effect of grazing time of day on goat milk chemical composition, renneting properties and milk fatty acid profile in a Mediterranean grazing system. Sixteen lactating Girgentana goats were divided into two experimental groups and housed in individual pens, where they received 500 g/d of barley grain. For 5 weeks the two groups were left to graze in two fenced plots on a ryegrass sward as follows: morning group (AM), from 9·00 to 13·00; afternoon group (PM), from 12·00 to 16·00. In selected herbage, water-soluble carbohydrates (WSC) increased in the afternoon (204 v. 174 g/kg dry matter, DM; P=0·01), whereas crude protein (CP) and linolenic acid decreased (respectively, 16·7…

Time FactorsLinolenic acidConjugated linoleic acidPastureGrazing time of day goat milk quality fatty acid composition.chemistry.chemical_compoundAnimal scienceGrazing time of dayGrazingAnimalsDry matterLactoseAnimal HusbandryMorningchemistry.chemical_classificationgeographygeography.geographical_feature_categoryGoatsFatty acidGeneral MedicineAnimal FeedDietFatty acid composition; Goat; Grazing time of day; Milk quality; Animal Husbandry; Animals; Diet; Female; Goats; Milk; Time Factors; Animal Feed; Animal Nutritional Physiological Phenomena; Food Science; Animal Science and ZoologyMilkchemistryBiochemistryGoatMilk qualityAnimal Science and ZoologyAnimal Nutritional Physiological PhenomenaFemaleFatty acid compositionFood ScienceThe Journal of dairy research
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A Short Synthesis of Polysubstituted Pyrrolidines via α-(Alkylidene­amino)nitriles

2004

α-(Alkylideneamino)nitriles can be deprotonated under mild conditions. Their conjugated anions react with enones in a 1,4-addition to yield δ-keto-α-(alkylideneamino)nitriles which in turn can be reduced to form pyrrolidines in a one-pot reaction sequence.

Turn (biochemistry)DeprotonationReaction sequenceChemistryYield (chemistry)Organic ChemistryOrganic chemistryAmino nitrilesGeneral MedicineConjugated systemMedicinal chemistryPyrrole derivativesSynlett
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Improving the Frying Performance and Oxidative Stability of Refined Soybean Oil by Tocotrienol-Rich Unsaponifiable Matters of Kolkhoung (Pistacia khi…

2018

Increasing consumer awareness for all natural products has quickly led to growing research on new resources of potent and profitable natural antioxidants. In this context, for the first time, the Kolkhoung hull oil (KHO) (Pistacia khinjuk)-unsaponifiable matters (USM) (UHO) (100, 200, and 400 mg kg−1) were incorporated into refined soybean oil (RSO) and the oxidative stability of prepared oils was measured during 32 hours of frying. Then, the obtained results (oxidative stability) were compared to the samples containing tert-butyl hydroquinone (TBHQ) (100 mg kg−1) as a common synthetic antioxidant. According to the results of oxidative stability assays of acid values, conjugated diene value…

Unsaponifiable matterfood.ingredientTocotrienolGeneral Chemical Engineering010401 analytical chemistryOrganic Chemistry04 agricultural and veterinary sciencesAntioxidant compoundTotal polar compound040401 food science01 natural sciencesSoybean oil0104 chemical scienceschemistry.chemical_compound0404 agricultural biotechnologyfoodchemistryUnsaponifiableConjugated diene valueChemical Engineering (all)Pistacia khinjukTocotrienolFood scienceKolkhoung hull oilJournal of the American Oil Chemists' Society
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Thermal Induction of 9t12t Linoleic Acid: a New Pathway for the Formation of Conjugated Linoleic Acids

2009

Accepted version of an article published in the journal: International Journal of Engineering and Technology Published version available at: http://www.ijetch.org/papers/066.pdf Thermal induction of 9t12t fatty acid leading to the formation of Conjugated Linoleic Acids (CLA) has been demonstrated by subjecting glyceride, and methyl ester of the acid to heat treatment. Fifteen micro liter portions of the glyceride sample containing 9t12t fatty acid (trilinoelaidin) were placed in micro glass ampoules and sealed under nitrogen and then subjected to thermal treatment at 250oC. The glass ampoules were taken out at regular time intervals, and the contents were subjected to composition analysis b…

VDP::Mathematics and natural science: 400::Basic biosciences: 470::Biochemistry: 476chemistry.chemical_compoundChemistryLinoleic acidOrganic chemistryConjugated systemGeneralLiterature_REFERENCE(e.g.dictionariesencyclopediasglossaries)International Journal of Engineering and Technology
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MRI-visible nanoparticles from hydrophobic gadolinium poly(ε-caprolactone) conjugates

2015

International audience; In this work we report on the synthesis of two hydrophobic and degradable gadolinium poly(ε-caprolactone) conjugates and their use for the preparation of MRI-visible nanoparticles intended for diagnosis applications. Advantage has been taken from functional poly(ε-caprolactone)s (PCL) bearing propargyl (PCL-yne) or amine groups (P(CL-co-NH2VL)) to yield conjugates by following two strategies. In a first approach, an azido-chelate of gadolinium (Gd(III)) has been conjugated by CuAAC to PCL-yne to yield a polymeric chelate containing 2.6 wt% of Gd(III). In a second approach, a dianhydride Gd(III)-ligand was reacted with P(CL-co-NH2VL) to yield, after complexation with …

[CHIM.POLY] Chemical Sciences/PolymersMaterials sciencePolymers and PlasticsBiocompatibility[SDV.IB.IMA]Life Sciences [q-bio]/Bioengineering/ImagingGadoliniumchemistry.chemical_elementNanoparticle02 engineering and technologyConjugated system010402 general chemistry01 natural scienceschemistry.chemical_compoundNanoparticlePolymer chemistryMaterials ChemistrypolyesterChelationOrganic Chemistry021001 nanoscience & nanotechnology0104 chemical sciences[CHIM.POLY]Chemical Sciences/Polymers[SDV.IB.IMA] Life Sciences [q-bio]/Bioengineering/ImagingchemistryPropargylnanoparticlesAmine gas treating0210 nano-technologyCaprolactoneMRIPolymer
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