Dialkylaminodifluorosulfinium salts: XtalFluor-E and XtalFluor-M

(A) Failure of Hydrocinnamyl Alcohol with XtalFluor-M: The reaction of hydrocinnamyl alcohol with 2 or 1 in acetonitrile provided an intractable mixture. For this reaction to proceed, the addition of exogenous sources of fluoride, such as Et3N·3HF or Et3N·2HF, was necessary (B) Halogenation of Alcohols with XtalFluor Reagents: Reaction of primary, secondary and tertiary alcohols with 1 using Et3N·3HF as a promoter gave the fluorinated nucleophilic substitution products. The addition order was a key parameter in this reaction. To obtain good selectivity and stereochemical integrity, 1,8-diazabicycloundec-7-ene (DBU) had to be used together with the fluorination agents. 5 A mixture of fluorinated bridged biphenyl systems has been obtained from 3-hydroxyspirodienones by means of a XtalFluor-E-promoted rearrangement. When compound 2 was used instead of compound 1, substrate decomposition was observed. 6 Chlorination, bromination and iodination reaction of primary alcohols in good yield has been described using a combination of tetraethylammonium halide and XtalFluor- E. (C) Geminal Difluorination of Carbonyl Groups: L'Heureux et al. have reported the geminal difluorination of carbonyl groups of aldehydes and ketones. They demonstrated that compound 1 alone was incapable of performing such transformations.5,8 To obtain geminal difluorinated products, it was necessary to use a promoter and increase the temperature (e.g., CH 2Cl2 or 1,2-dichloroethane at reflux). (D) Fluorination Processes on Carbohydrate Derivatives: Fuchs and co-workers have recently reported the preparation of a fluorodisaccharide in excellent yield without side products using XtalFluor-E, thus eliminating the need for purification. 9 The effective preparation of glycosyl fluorides from thio-, seleno-, telluro- and glycosyl sulfoxides has been performed in 30 minutes by Williams and co-workers with evidence that fluoride is delivered by the tetrafluoroborate counterion (E) Enantioselective Ring Expansion of Prolinols: Direct ring expansion of N-alkyl prolinols to produce the corresponding 3-azidopiperidines in good and excellent regio-, diastereo- and enantioselectivity was achieved by using XtalFluor-E. Formation of an aziridinium intermediate which reacts with a nucleophile such as tetrabutylammonium azide (Bu4NN3) is proposed (F) Cyclodehydration Agents: Paquin and co-workers have recently reported 12 the use of 1 as a practical cyclodehydration agent to obtain 1,3,4-oxadiazoles among other nitrogen-containing heterocycles.13 The addition of acetic acid improved the yield and selectivity of the oxadiazole formation. (G) Activating Agents for Carboxylic Acids: Compound 1 has proved to be an efficient coupling agent for the synthesis of amides by activation of the carboxylic acid. 14 Moreover, this reaction is carried out with primary and secondary amines in good yield without epimerization or racemizatio

Apicoplast isoprenoid precursor synthesis and the molecular basis of fosmidomycin resistance in Toxoplasma gondii

Expression of a bacterial transporter protein in Toxoplasma gondii results in parasite susceptibility to Formidomycin, a drug targeting isoprenoid precursor synthesis

Micromagnetic and Magnetoresistance Studies of Ferromagnetic La\u3csub\u3e0.83\u3c/sub\u3eSr\u3csub\u3e0.13\u3c/sub\u3eMnO\u3csub\u3e2.98\u3c/sub\u3e Crystals

Magnetic force microscopy (MFM) and atomic force microscopy (AFM) were used to investigate the surface topography and micromagnetic structure of La0.83Sr0.13MnO2.98 single crystals with colossal magnetoresistance (CMR). The crystals were grown by fused salt electrolysis and characterized by chemical analysis, X-ray diffraction, magnetic and transport measurements. The crystals are rhombohedral (R 3 c). Magnetic and transport measurements indicate that the ferromagnetic ordering at 310 K is associated with an insulator-metal transition at the same temperature. A maximum negative magnetoresistance (-62 %) is observed at 290 K in an applied magnetic field of 5 T. The magnetoresistance increases in magnitude sharply (1.8 %), comparing to the rest of the change, with increasing magnetic field up to 20 G, and then it increases slowly with increasing field. MFM and AFM were used to study the (110) surface as well as a number of unspecified surfaces. Surface topography of an as-grown crystal exhibits well-developed surface corrugations due to extensive twinning. The corrugation angle at twin boundaries can be related to the unit cell parameters, surface and twinning planes. Magnetic force microscopy images show that magnetic domain boundaries are pinned to the crystallographic twins; a small number of unpinned boundaries are observed. The statistical analysis of domain boundary angle distribution is consistent with cubic magnetocrystalline anisotropy with easy axis along [100] directions for this material. Unusual magnetization behavior in the vicinity of topological defects on the surface is also reported. MFM contrast was found to disappear above the ferromagnetic Curie temperature; after cooling a new magnetic structure comprised of Bloch walls of opposite chiralities developed

Polyfunctionalised nanoparticles bearing robust gadolinium surface units for high relaxivity performance in MRI

The first example of an octadentate gadolinium unit based on DO3A (hydration number q = 1) with a dithiocarbamate tether has been designed and attached to the surface of gold nanoparticles (around 4.4 nm in diameter). In addition to the superior robustness of this attachment, the restricted rotation of the Gd complex on the nanoparticle surface leads to a dramatic increase in relaxivity (r1) from 4.0 mM‐1 s‐1 in unbound form to 34.3 mM‐1 s‐1 (at 10 MHz, 37 °C) and 22 ± 2 mM‐1s‐1 (at 63.87 MHz, 25 °C) when immobilised on the surface. The ‘one‐pot’ synthetic route provides a straightforward and versatile way of preparing a range of multifunctional gold nanoparticles. The incorporation of additional surface units improving biocompatibility (PEG and thioglucose units) and targeting (folic acid) lead to little detrimental effect on the high relaxivity observed for these non‐toxic multifunctional materials. In addition to the passive targeting attributed to gold nanoparticles, the inclusion of a unit capable of targeting the folate receptors overexpressed by cancer cells, such as HeLa cells, illustrates the potential of these assemblies

Zinc 2-((2-(benzoimidazol-2-yl)quinolin-8-ylimino)methyl)phenolates : synthesis, characterization and photoluminescence behavior

A series of 2-(2-(1H-benzoimidazol-2-yl)quinolin-8-yliminomethyl)phenol derivatives and their zinc complexes (C1 – C5) were synthesized and fully characterized. The molecular structure of the representative complex C2 was determined by single crystal X-ray diffraction, which revealed that the zinc was five-coordinated with the tetra-dentate ligand and a methanol bound to the metal afford a distorted square-pyramidal geometry. The UV-Vis absorption and fluorescence spectra of the organic compounds and their zinc complexes were measured and investigated in various solvents such as methanol, THF, dichloromethane, and toluene; significant influences by solvents were observed on their luminescent properties; red-shifts for the zinc complexes were clearly observed in comparisons to the free organic compounds

Structural Diversity of Alkaline Earth Centered Gold(I) Metallacoronates

One‐pot reactions of the catechol‐scaffolding aroylbis(N,N‐diethylthiourea) H2Lcat with mixtures of alkaline earth nitrates M(NO3)2 (M2+ = Ca2+, Sr2+ or Ba2+) and (NEt4)[AuCl4] or [Au(tht)Cl] (tht = tetrahydrothiophene) in methanol in the presence of Et3N as supporting base give rise to neutral trinuclear gold(I) {2}‐metallacoronates with the composition of {M ⊂ [Au2(Lcat)2]} (1). Similar reactions with the pyridine‐centered aroylbis(N,N‐diethylthiourea) H2Lpy, however, produce complexes with the same metal‐to‐ligand ratio but with higher nuclearity {2M ⊂ [Au4(Lpy)4]} (2). In both 1 and 2, Au(I) ions are exclusively S‐bonded with the organic ligands and adopt a virtually linear coordination fashion. Such metal‐ligand binding is responsible for the formation of metallacoronands, which accommodate alkaline earth metal ions in their molecular voids, thereby resulting in host–guest coordination assemblies. The level of metal‐ligand aggregation in the resulting assemblies is dependent on the denticity, size and flexibility of the centered building block of the aroylbis(N,N‐diethylthiourea) ligands

Creysse – Le site stratifié de Canolle Ferme

Lien Atlas (MCC) :http://atlas.patrimoines.culture.fr/atlas/trunk/index.php?ap_theme=DOM_2.01.02&ap_bbox=0.527;44.844;0.584;44.887 Le secteur de Barbas/Canaule est connu depuis de nombreuses années pour sa forte concentration de sites archéologiques. Sur un rayon de 300 m, une mosaïque d’occupations très compliquée illustre de nombreux loci clairement stratifiés, tels les Barbas (I, II, III et V), les Rigoux, ou encore Canaule II, auxquels s’en ajoutent d’autres à la localisation plus incerta..