Search results for "TRIF"
showing 10 items of 1419 documents
2,3-Dihydro-1,2,6-thiadiazine 1-Oxides by Biginelli-Type Reactions with Sulfonimidamides under Mechanochemical Conditions.
2021
Biginelli-type multicomponent reactions (MCRs) with NH-free sulfonimidamides provide 2,3-dihydro-1,2,6-thiadiazine 1-oxides in high yields. The couplings are performed in a planetary ball mill under solvent-free mechanochemical conditions. Acetic acid or ytterbium triflate are used as catalysts. A representative product was characterized by X-ray single crystal structure analysis revealing molecular details of the highly functionalized three-dimensional heterocycle. Further product modifications lead to additional structural scaffolds.
Efficient and Mild Ytterbium(III)-Catalyzed Tosylation of Alcohols.
2004
Ytterbium(III) trifluoromethanesulfonate efficiently catalyzes the reaction of primary and secondary alcohols with toluenesulfonic acid anhydride to yield the alkyl tosylates in high yields. The reactions were carried outunder neutral and mild conditions and product purification was easily achieved by means of short column chromatography.
ChemInform Abstract: Synthesis of Functionalized Indoles with a Trifluoromethyl-Substituted Stereogenic Tertiary Carbon Atom Through an Enantioselect…
2010
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%.
Perfluoroketene dithioacetals and perfluorodithiocarboxylic acid derivatives: Versatile tools for organofluorine synthesis
2007
Perfluoroketene dithioacetals are simple and versatile compounds that can be transformed into a large variety of trifluoromethyl derivatives, in particular aza- and thiaheterocycles, perhalodithiocrotonic esters, and fluorinated dithiol thiones. These unsaturated perfluorodithioesters and analogs give interesting polar cycloaddition reactions whose mechanism is strongly influenced by the fluorine substitution. This substitution plays an important role in the reactivity of saturated perfluorodithiocarboxylic acids as well. Except for the carbophilic addition of allyl Grignard reagents to perfluorocarboxamides, a domino thiophilic addition-fluoride elimination was the main reaction process. I…
Thermodiffusion anisotropy under a magnetic field in ionic liquid-based ferrofluids
2021
International audience; Ferrofluids based on maghemite nanoparticles (NPs), typically 10 nm in diameter, are dispersed in an ionic liquid (1-ethyl 3-methylimidazolium bistriflimide - EMIM-TFSI). The average interparticle interaction is found to be repulsive by small angle scattering of X-rays and of neutrons, with a second virial coefficient A2 = 7.3. A moderately concentrated sample at Φ = 5.95 vol% is probed by forced Rayleigh scattering under an applied magnetic field (up to H = 100 kA m-1) from room temperature up to T = 460 K. Irrespective of the values of H and T, the NPs in this study are always found to migrate towards the cold region. The in-field anisotropy of the mass diffusion c…
Determinants of the distribution of nitrogen-cycling microbial communities at the landscape-scale
2010
Little information is available regarding the landscape-scale distribution of microbial communities and its environmental determinants. However, a landscape perspective is needed to understand the relative importance of local and regional factors and land management for the microbial communities. In this manuscript, we investigated the distribution of functional microbial communities involved in N-cycling and of the total bacterial and crenarchaeal communities over 107 sites using a grid with a 16 km lag distance within Burgundy, a 31 500 km2 region in France. After quantifying the abundances of the total bacterial, crenarchaeal, nitrate-reducing, denitrifying and ammonia-oxidizing communit…
A method for the preparation of repacked soil cores with homogeneous aggregates for studying microbial nitrogen transformations under highly controll…
1998
International audience; he feasibility of studies on nitrate transformations during incubation in controlled conditions of air-filled porosity using a method of soil core preparation was investigated. Repacked cores were obtained by uniaxial confined compression in a cylindrical mould of a mass of calibrated and conveniently wet aggregates with a water content selected to saturate the textural porosity of the soil aggregates, imposing structural porosity and thereby producing controlled conditions of aeration. The principle and the descrip- tion of the incubation method are explained and some denitrification and respiration data obtained with low and increasing OZ partial pressures are pres…
Effets simultanés de niveaux croissants de glucose et de pressions partielles en oxygène sur la dénitrification et la réduction dissimilative du nitr…
1998
International audience; Dissimilatory nitrate reduction to ammonium (DNRA) and its importance in comparison to denitrification were studied in soil samples artificially repacked to control water potential and porosity, and incubated for 72 h. Labelled nitrate (100 mg N.kg-’ dry soil, 21.8 % 15N in excess) and increasing levels of glucose-C (250, 500 and 1 000 mg glucose-Ckg-’ dry soil) were initially added to the soil samples to obtain increasing glucose-C/nitrate-N ratios of 2.5,5 and 10, which were then subjected to different 0, partial pressures (0,0.5, 1.0 and 2.0 % (v/v)). The results confirmed the good reproducibility of the experimental condi- tions using this method. Denitrification…
Differential Responses of Nitrate Reducer Community Size, Structure, and Activity to Tillage Systems
2009
ABSTRACT The main objective of this study was to determine how the size, structure, and activity of the nitrate reducer community were affected by adoption of a conservative tillage system as an alternative to conventional tillage. The experimental field, established in Madagascar in 1991, consists of plots subjected to conventional tillage or direct-seeding mulch-based cropping systems (DM), both amended with three different fertilization regimes. Comparisons of size, structure, and activity of the nitrate reducer community in samples collected from the top layer in 2005 and 2006 revealed that all characteristics of this functional community were affected by the tillage system, with increa…
Mapping field-scale spatial distribution patterns of size and activity of the denitrifier community
2008
International audience