نتایج جستجو برای: furans
تعداد نتایج: 955 فیلتر نتایج به سال:
We evaluated the effect of chronic exposure to dioxin and dioxin-like compounds on the pancreas in female Harlan Sprague-Dawley rats. This investigation represents part of an ongoing National Toxicology Program initiative to determine the relative potency of chronic toxicity and carcinogenicity of polychlorinated dioxins, furans, and biphenyls. Animals were treated by gavage for up to 2 years w...
Fermentatively produced ethanol from lignocellulose by yeast is a renewable alternative to fossil fuels. However, inhibitors originating from the breakdown process of the raw material decrease the fermentation rate. Previous studies have made known inhibition effects by the furan compounds furfural and hydroxymethyl furfural (HMF). In the current work, the kinetics and inhibition effect of furf...
The aim of this work was to identify and gain further knowledge on the origin of sulfur compounds present in the volatile fraction of cooked ham, and on their role in the aroma of this product. To this end, we performed analyses by one- and two-dimensional gas chromatography coupled with mass spectrometry, and olfactometry. Among the odorant sulfur compounds identified, three furans present in ...
The mechanisms of gold(III)-catalyzed synthesis of highly substituted furans via [3,3]-sigmatropic rearrangements and/or [1,2]-acyloxy migration based on propargyl ketones have been investigated using density functional theory calculations at BHandHLYP/6-31G(d,p) (SDD for Au) level of theory. Solvent effects on these reactions were explored using calculations that included a polarizable continu...
A series of (E)-1-aryloxy-1-en-3-ynes has been prepared by Sonogashira coupling of 2-bromo-3-aryloxypropenoates with terminal alkynes using Pd(PPh(3))(4) and CuI as the catalysts in Et(3)N. The resulting enynyl-aryl ethers are found to be highly applicable to the synthesis of 2,4-disubstituted furans with an ester group at C-4 position through an Au/Ag-catalyzed annulation reaction under extrem...
Environmental pollutants, such as dioxins and furans, are extremely toxic and related with pulmonary diseases development. Impairment of mitochondrial function has been shown in pollutant-induced hepatic injury, but it has not been addressed in lungs, even though lung mitochondria are primary cellular targets for pollutants-induced toxicity. In isolated lung mitochondria, dibenzofuran significa...
Photooxygenation of azidoalkyl furans has revealed both a novel triazole formation method and a unique endoperoxide rearrangement. The key step of this method is a 3 + 2 cycloaddion of the azide to the endoperoxide intermediate. The reduction of the peroxide bond and two subsequent C-C bond cleavages provide a triazole having a newly formed carboxylic acid functionality. The reactions are clean...
A catalytic decarboxylative annulation has been developed for the regioselective synthesis of trisubstituted furans by the cycloaddition of ketones with α,β-unsaturated carboxylic acids under ambient air. A library of furan derivatives were obtained in good yields from the readily available substrates in the combination of a catalytic amount of Cu-salt and a stoichiometric amount of water. Wate...
In the presence of trifluoromethylsulfonium reagents, boronate complexes derived from 2-lithio furan and non-racemic secondary and tertiary alkyl or aryl boronic esters undergo deborylative three-component coupling to give the corresponding 2,5-disubstituted furans with excellent levels of enantiospecificity. The process proceeds via the reaction of boronate complexes with a trifluoromethyl rad...
Abstract Furans are an important class of compounds that can be thermochemical or enzymatically produced from biomass. Despite their importance little is known about the thermal decomposition furans with oxygenated substituents. In this work, influence -CH3, -CH2OH and -CHO functional groups on molecular radical chemistry studied a combined quantum chemical experimental approach using 2-furfury...
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