Search results for " aroma"
showing 10 items of 370 documents
Synthesis of Functionalized Indoles with a Trifluoromethy-Substituted Stereogenic Tertiary Carbon Atom Through an Enantioselective Friedel-Crafts Alk…
2010
[EN] Chiral complexes of BINOL-based ligands with zirconium tert-butoxide catalyze the Friedel-Crafts alkylation reaction of indoles with beta-trifluoromethyl-alpha,beta-unsaturated ketones to give functionalized indoles with an asymmetric tertiary carbon center attached to a trifluoromethyl group. The reaction can be applied to a large number of substituted alpha-trifluoromethyl enones and substituted indoles. The expected products were obtained with good yields and ees of up to 99%.
Straightforward One-Pot Synthesis of New 4-Phenyl-1,2,5,6-tetraazafluoranthen-3(2H)-one Derivatives: X-ray Single Crystal Structure and Hirshfeld Ana…
2022
A straightforward one-pot route for the synthesis of a new 4-phenyl-1,2,5,6-tetraazafluoranthen-3(2H)-one is reported form the direct hydrazinolysis of triketo ester and hydrazine hydrate in ethanol. 4-Phenyl-1,2,5,6-tetraazafluoranthen-3(2H)-one was subjected to aza-Michael addition and N-alkylation on reaction with a set of alkylating agents in the presence of K2CO3. Hydrazinolysis of 4-phenyl-1,2,5,6-tetraazafluoranthen-3(2H)-one ester to hydrazide and conversion of hydrazide to thiosemicarbazide were successful. X-Ray single crystals analysis and 1H, 13C NMR were used for unambiguous structure confirmation. The O…H, N…H, C…N and C…C in 2, and the N…H, …
Non-oxidative dehydroaromatization of methane:an effective reaction regeneration cyclic operation for catalyst life extension
2015
[EN] Non-oxidative methane aromatization is an attractive direct route for producing higher hydrocarbons. It is highly selective to benzene despite the low conversion due to thermodynamic limitations, and Mo/H-ZSM-5, the first catalyst proposed for this reaction, is still considered as one of the most adequate. The major problem of this process is the severe catalyst deactivation due to the rapid build-up of carbonaceous deposits on the catalysts. Here we present an effective regeneration procedure that extends the life of Mo/zeolite based catalysts by combining reaction periods of 1.5 h with 0.5 h regeneration steps in a continuous cyclic mode and methane activation after each regeneration…
Response of soil phosphatase activities to contamination with two types of tar oil.
2018
Tar oil is a complex mixture of hydrocarbon compounds obtained from high-temperature distillation of coal tar. It has been used for over 100 years from now to protect wood and has been applied to wood products, primary utility poles, and railroad ties by pressure methods. Composition of the tar oil depends on the source and typically consists of 85% polycyclic aromatic hydrocarbons (PAHs), 10% phenolic compounds, and 5% heterocyclic compounds. In this research, we performed the laboratory experiment to compare two types of tar oil: C and GX-Plus, and their effects on P-cycling enzymes (phosphatases) in sandy loam and loamy sand. Tar oil was applied to soil samples at the following doses: 2,…
Sustainable Weed, Disease and Pest Management in Medicinal and Aromatic Plants
2015
As for all other crops, in MAPs as well, weeds, diseases and pests are important yield-reducing factors, which may severely curtain biomass production and, that is maybe more important, may affect several qualitative aspects of production. Research about this topic is generally lacking, for two main reasons: the first is that MAPs are generally grown on rather limited areas, and the incidence of specific pests and diseases rarely takes a relevance outside rather narrow boundaries. The second reason is that the economical importance of MAPs is much lower than that ascribed to the “major” crops, which the bigger efforts of research are addressed to. In the changing scenario of latter years, h…
Interaspecific chemical variability and highlighting of chemotypes of leaf essential oils from Ravensara aromatica Sonnerat, a tree endemic to Madaga…
2006
Ravensara aromatica Sonnerat is a tree endemic to Madagascar. The essential oil extracted from the leaves is used in aromatherapy. Previous chemical studies have generated some confusion with regard to the chemical composition of this essential oil. In order to eliminate this uncertainty, we undertook a systematic evaluation of the chemical composition of essential oils from leaves of this species. The study focused on 28 individual samples formally identified as R. aromatica. The essential oils were obtained by hydrodistillation and analysed by GC and GC–MS. It was possible to distinguish four groups of trees through principal components analysis and agglomerative hierarchical clustering a…
On the Nucleophilic Reactivity of 4,6-Dichloro-5-nitrobenzofuroxan with Some Aliphatic and Aromatic Amines: Selective nucleophilic substitution
2020
The reaction rates for the nucleophilic aromatic substitution of 4,6-dichloro-5-nitrobenzofuroxan 1 with eight aliphatic amines (characterized by very different basicities/ nucleophilicities) and three anilines have been measured in both methanol and toluene. The obtained rates have been related to the basicity (pKaH in water and Kb in benzene) or nucleophilicity (N Mayr constants) of the tested amines. The whole of the obtained kinetic data has furnished useful information on the high nucleophilic reactivity of benzofuroxan derivatives, which has been related essentially to two factors: the high electron-drawing ability/power of the condensed furoxan ring and the low aromatic character of …
A Simple Phosphine–Diolefin‐Promoted Copper‐Catalysed N‐Arylation of Pyrazoles with (Hetero)aromatic Bromides: The Case of Chloroarenes Revisited
2012
A molecularly defined new phosphine–diolefin cubane copper pre-catalyst used at 1.25 mol % under mild conditions promotes the coupling of pyrazoles to functionalised aryl and heteroaryl bromides, which hold a variety of functional groups. This versatile phosphorus-based system was thus successfully used, under identical conditions, for the coupling of a large scope of heteroaromatics to selectively produce pyridinyl- and pyrimidinyl-pyrazoles, as well as several novel furyl-, thienyl- and thiazolyl-substituted pyrazoles. The careful investigation of coupling with the analogous aryl and heteroaryl chlorides clearly indicated that for specifically activated chloroarenes a direct nucleophilic …
Unexpected DNA damage caused by polycyclic aromatic hydrocarbons under standard laboratory conditions
2007
Abstract The genotoxicity of 15 polycyclic aromatic hydrocarbons was determined with the alkaline version of the comet assay employing V79 lung fibroblasts of the Chinese hamster as target cells. These cells lack the enzymes necessary to convert PAHs to DNA-binding metabolites. Surprisingly, 11 PAHs, i.e., benzo[ a ]pyrene (BaP), benz[ a ]anthracene, 7,12-dimethylbenz[ a ]anthracene, 3-methylcholanthrene, fluoranthene, anthanthrene, 11 H -benzo[ b ]fluorene, dibenz[ a,h ]anthracene, pyrene, benzo[ ghi ]perylene and benzo[ e ]pyrene caused DNA strand breaks even without external metabolic activation, while naphthalene, anthracene, phenanthrene and naphthacene were inactive. When the comet as…
Predicting the bioaccumulation of polyaromatic hydrocarbons and polychlorinated biphenyls in benthic animals in sediments
2016
There were two main objectives in this study. The first was to compare the accuracy of different prediction methods for the chemical concentrations of polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in the organism, based on the measured chemical concentrations existing in sediment dry matter or pore water. The predicted tissue concentrations were compared to the measured ones after 28-day laboratory test using oligochaeta worms (Lumbriculus variegatus). The second objective was to compare the bioaccumulation of PAHs and PCBs in the laboratory test with the in situ bioaccumulation of these compounds. Using the traditional organic carbon-water partitioning model, tissue…