1-(Organosulfonyloxy)-3(1H)-1,2-benziodoxoles: Preparation and Reactions with Alkynyltrimethylsilanes

Organosulfonyloxy derivatives of 1,2-benziodoxol-3(1H)-one (3a-c) and 3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole (5a-c) can be prepared in high yield by the reaction of 1-hydroxybenziodoxoles 1 or 4 and the corresponding sulfonic acids or Me(3)SiOTf in the form of stable, but moderately hygroscopic, microcrystalline solids. Reaction of the triflate derivatives 3a and 5a with alkynyltrimethylsilanes affords either alkynyliodonium triflates 6, or (E)-beta-(trifluoromethanesulfonyloxy)alkenyliodonium triflates 7, while the same reaction in the presence of pyridine selectively gives the respective 1-alkynylbenziodoxoles 8 and 9 in 82-90% yield.     

1-[Hydroxy(sulfonyloxy)iodo]-1H,1H-perfluoroalkanes: Stable, Fluoroalkyl Analogs of Koser's Reagent

1-[Hydroxy(sulfonyloxy)iodo]-1H,1H-perfluoroalkanes 3 [R(f)CH(2)I(OH)OSO(2)R; R = CH(3), CF(3), p-CH(3)C(6)H(4), R(f) = CF(3), C(2)F(5)] can be prepared in two steps from the appropriate iodofluoroalkanes by oxidation with peroxytrifluoroacetic acid and subsequent reaction with TsOH, MsOH, or Me(3)SiOTf. The tosylate derivative 3a reacts with silyl enol ethers under mild conditions to give the respective alpha-(tosyloxy) ketones. A similar reaction of cyclohexene furnishes cis-1,2-bis(tosyloxy)cyclohexane as the major product. Triflates 3c,f react with (trimethylsilyl)arenes under mild conditions to afford the respective (fluoroalkyl) (aryl)iodonium triflates 7, while the analogous reaction with alkynyltrimethylsilanes leads to novel (fluoroalkyl)(alkynyl)iodonium salts 8.     

On the metabolites produced by Colletotrichum gloeosporioides a fungus proposed for the Ambrosia artemisiifolia biocontrol; spectroscopic data and absolute configuration assignment of colletochlorin A

Ambrosia artemisiifolia L. is responsible for serious allergies induced on humans. Different approaches for its control were proposed during the COST Action FA1203 “Sustainable management of Ambrosia artemisiifolia in Europe” (SMARTER). Fungal secondary metabolites often show potential herbicidal activity. Three phytotoxins were purified from the fungal culture filtrates of Colletotrichum gloeosporioides, isolated from infected leaves of A. artemisiifolia. They were identified by spectroscopic and chemical methods as colletochlorin A, orcinol and tyrosol (1, 2 and 3). The absolute configuration 6’R to colletochlorin A was assigned for the first time applying the advanced Mosher’s method. When assayed by leaf-puncture on A. artemisiifolia only 1 caused the appearance of large necrosis. The same symptoms were also induced by 1 on ambrosia plantlets associated with plant wilting. On Lemna minor, colletochlorin A caused a clear fronds browning, with a total reduction in chlorophyll content.     

Uranium assay and trace element analysis of the fourth collaborative material exercise samples by the modified Davies-Gray method and the ICP-MS/OES techniques

Journal of Radioanalytical and Nuclear Chemistry - An international group of laboratories participating in CMX-4 subjected three samples to comparative nuclear forensic analysis using uranium assay...     

Synthesis of Water-soluble,Polyester-based Dendrimer Prodrugs for Exploiting Therapeutic Properties of Two Triterpenoid Acids

Dendrimers are macromolecules characterized by high controlled size, shape and architecture, presence of inner cavities able to accommodate small molecules and many peripheral functional groups to bind target entities. They are of eminent interest for biomedical applications, including gene transfection, tissue engineering, imaging, and drug delivery. The well-known pharmacological activities of ursolic and oleanolic acids are limited by their small water solubility, non-specific cell distribution, low bioavailability, poor pharmacokinetics, and their direct administration could result in the release of thrombi. To overcome such problems, in this paper we described their physical incorporation inside amino acids-modified polyester-based dendrimers which made them highly water-soluble. IR, NMR, zeta potential, mean size of particles, buffer capacity and drug release profiles of prepared materials were reported. The achieved water-soluble complexes harmonize a polycationic character and a buffer capacity which presuppose efficient cell penetration and increased residence time with a biodegradable cell respectful scaffold, thus appearing as a promising team of not toxic prodrugs for safe administration of ursolic and oleanolic acids.     

IR spectroelectrochemical studies of Fe2V4O13, FeVO4 and InVO4 thin films obtained via sol-gel synthesis

In this paper we generalize the IR spectroscopic properties of M³⁺VO₄ (M=Fe, In) orthovanadate and Fe₂V₄O₁₃ films. The films were prepared using the sol-gel synthesis route from M³⁺ nitrates and vanadium oxoisopropoxide. The vibrational bands in the IR absorbance spectra of the films are classified in terms of terminal V-O stretching (1050–880 cm^–1), bridging V-O^...Fe and V^...O^...Fe stretching (880–550 cm^–1), mixed V-O-V deformations and Fe-O stretching (<550 cm^–1) modes. Ex situ IR spectra of films were measured after consecutive charging/discharging to various intercalation coefficients x and correlated to the current peaks in the cyclic voltammetry curves measured in 1 M LiClO₄/propylene carbonate electrolyte. We classified the ex situ IR spectra of charged/discharged films according to their vibrational band changes. The results reveal that, for small values of the intercalation coefficient, crystalline FeVO₄, InVO₄ and Fe₂V₄O₁₃ films exhibit a simultaneous decrease in the intensity of all IR bands while the band frequencies remain unaffected. For the higher intercalation levels, IR mode frequencies are shifted, signaling the presence of reduced vanadium. Further charging leads to an amorphization of the film structure, which was established from the similarity of the IR spectra of charged films with those of amorphous films prepared at lower annealing temperatures. The results confirm that ex situ IR spectroelectrochemical measurement is an effective way to assess the structural changes in films with different levels of intercalation. Electronic Publication     

Neue Cyclosilicate der Alkalimetalle: Cs5AgSi3O9 und Cs6Na6Si6O18

New Alkali Cyclosilicates: Cs₅AgSi₃O₉ and Cs₆Na₆Si₆O₁₈ The new cyclosilicates were obtained from reactions of the binary oxides at 450–500 °C under inert gas atmosphere. Cs₅AgSi₃O₉ crystallizes in the space group P2₁/m with the lattice constants a = 968,2(2) pm, b = 652,7(1) pm, c = 1162,6(3) pm, β = 93,84(2)° and Cs₆Na₆Si₆O₁₈ in R‐3m with a = 1208,0(1) pm, c = 1458,9(2) pm (IPDS data sets). The characteristic features are isolated rings, [Si₃O₉]^6– and [Si₆O₁₈]^12–, respectively. In Cs₅AgSi₃O₉ these are connected via Ag⁺ to chains. Layers of [NaO₄]‐tetrahedra separate the hexameric rings in Cs₆Na₆Si₆O₁₈. Coordination numbers of caesium are observed between C.N. 3 and C.N. 9 in these alkali rich cyclosilicates. MAPLE calculations of both cyclosilicates as well as the absorption and IR spectrum of Cs₅AgSi₃O₉ are presented. Preparative and thermoanalytical techniques have been used to investigate the reactivity of Cs₅AgSi₃O₉ in the presence of cobalt and nickel metal.     

4,5-Dihydroisoxazole and 4,5-dihydro-1,2,4-oxadiazole derivatives from cycloaddition reactions of nitrile oxides to alkyl N-(diphenylmethylene)-α,β-dehydroamino acids

The alkyl N-(diphenylmethylene)-α,β-dehydroamino acids 1 have been submitted to 1,3-dipolar cycloadditions with nitrile oxides. The reactivity of these compounds depends on the type and on the stereochemistry of the β-substituents. With the unsubstituted terms 1a,b the reaction occurs on the C,C double bond, providing a good method for the synthesis of the 4,5-dihydroisoxazole derivatives 3a,b,c and for the gem-functionalized 4,5-dihydroisoxazoles amino carboxylic ester 5. The β-substituted compounds 1c,d,e , inert to 1,1-dimethylethylnitrile oxide, undergo the reaction to the N,C double bond, thus giving with 2a,b the 4,5-dihydro-1,2,4-oxadiazole derivatives 4. All the reactions occur with high site- and regioselectivity.     

The determination of chlorinated biphenyls,chlorinated dibenzodioxins,and chlorinated dibenzofurans by GC-MS

High resolution gas chromatography, with mass selective detection, has been used for the analysis of PCB on methyl 50 % octyl polysiloxane (SB 50 Octyl), methyl octadecyl polysiloxane, and a smectic polysiloxane (SB Smectic); and for the analysis of polychlorodibenzodioxins and polychlorodibenzofurans with 1 to 8 chlorine substituents on 100 % cyanopropyl siloxane (SP 2331), smectic polysiloxane (SB Smectic), a new polar stationary phase (DB-Dioxin). The analysis has also been performed by column coupling.