Effect of pressure on the low-temperature reaction of ethylene with N2O4

Calorimetric monitoring of the autoclave reaction N₂O₄ + C₂H₄ at –85 to +10 °C under argon pressure 10–30 bar revealed that the exothermic chemical reaction started at temperatures above –52 °C at 10 bar, whereas an intensive exothermic reaction started at –85 °C and pressure of 30 bar. IR study showed that oligo/polynitroethylene was formed at 30 bar, while carbonyl and hydroxy compound as well as nitrate R–ONO₂ formation occurred upon processing at 10 bar.     

Fluorous osmium tetraoxide (OsO4): a recoverable and reusable catalyst for dihydroxylation of olefins

A fluorous osmium catalyst was firstly developed. It had been effectively used as recoverable and reusable catalyst in the dihydroxylation of olefins.     

Self‐assembly of amphiphilic tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers

Amphiphilic tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers consisting of one polystyrene block and two poly(N‐isopropylacrylamide) blocks were prepared by the “arm‐first” method in which RAFT polymerization and nonconvalent ligand–metal complexation were employed. The prepared amphiphilic star‐shaped metallopolymers are able to form micelles in water. The size and distribution of the micelles were studied by dynamic light scattering and transmission electron microscopy techniques. Preliminary studies indicate that the polymer concentration and the hydrophilic poly(N‐isopropylacrylamide) block length can affect the morphologies of the formed metal‐interfaced core–shell micelles in water. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4204–4210, 2007     

Carboxylic fused furans for amino acid fluorescent labelling

Four carboxylic fused furans are presented as new fluorescent labels for the amino and hydroxyl functions of organic molecules. Various representative l-amino acids were chosen as models, labelled at their N-terminus and also at their side-chain. Fluorescent derivatives were obtained in high yields, and their absorption and emission properties were studied.     

Synthesis of 3-hydroxyindolin-2-one alkaloids, (±)-donaxaridine and (±)-convolutamydines A and E, through enolization-Claisen rearrangement of 2-allyloxyindolin-3-ones

Claisen rearrangement triggered by enolization of 2-allyloxyindolin-3-ones with DBU was performed in order to prepare 3-allyl-3-hydroxyindolin-2-ones. Total synthesis of 3-hydroxyindolin-2-one alkaloids, (±)-donaxaridine, as well as (±)-convolutamydines A and E, was achieved by transformation of the allyl moiety of 3-allyl-3-hydroxyindolin-2-ones.     

A Study on Stripping Voltammetric Determination of Osmium(IV) at a Carbon Paste Electrode Modified In Situ with Cationic Surfactants

This article deals with the development of a method for the determination of osmium at a carbon paste electrode (CPE) modified with cationic surfactants of the quaternary ammonium salt type; namely, cetyltrimethylammonium bromide (CTAB) and 1‐(ethoxycarbonyl)‐pentadecyltrimethyl‐ammonium bromide (Septonex); both being added in situ and serving for preconcentration of osmium via its hexachloroosmate(IV) anion. The proper electrochemical detection was performed by cathodic scanning in the differential pulse voltammetric mode. Optimization studies concerning important experimental parameters also included a specially performed potentiometric titration, helping to define the actual stoichiometry for the ion‐pairing process, the main principle and driving force of the accumulation step. In a chloride/acetate buffer based supporting medium and with Septonex as the modifier of choice, the reduction signal for osmium was found to be proportional to the Os(IV) concentration in a range from 5×10^?9 to 5×10^?7 mol L^?1 with a limit of detection close to 5×10^?9 mol L^?1 (with preconcentration for 60 s). The method capable to determine Os(IV) in the presence of both Pt(IV) and Ir(III) was tested on model solutions as well as with real sample of industrial waste water (spiked with the analyte); both yielding the recovery rates within 88–99%.     

Supramolecular structures of macromolecules containing bipyridine–copper(I) complexes as revealed from transmission electron microscopy studies

Transmission electron microscopy (TEM) studies on bipyridine (bpy) containing block copolymer systems showed the formation of nanoscopic polymer–ion complexes through complexation with copper(I) ions which segregated to highly ordered columnar domains of mesoscopic dimensions. The domains, i.e. stacks of [(bpy)₂Cu(I)] complex moieties could be visualized by complementary TEM techniques. First, electron energy loss spectra (EELS) showed the absorption edges of copper and nitrogen, which are specific for the bipyridine copper complexes. The element spectroscopic imaging (ESI) technique allowed the imaging of the net copper and net nitrogen distribution, and the coinciding pictures exhibited a microphase separated system in the case of a 3-block copolymer with complexed end segments. High resolution elastic bright field images showed interference lines with a line to line distance of about 8 A which could be related to the Cu–Cu distance in staggered Cu(I)–bipyridine complexes. Received: 6 August 1997 Accepted: 28 April 1998     

Stereospecific synthesis of new 2,3,4,5-piperidinetetracarboxylic acids and 2,3,5-piperidinetricarboxylic acids

Diels-Alder adducts of 1,2-dihydropyridine with maleic and acrylic acid derivatives were stereospecifically converted by way of RuO₄ oxidation into new r-2,c-3,c-4,c-5-piperidinetetracarboxylic acid, r-2,t-3,t-4,c-5-piperidinetetracarboxylic acid, r-2,c-3,c-5-piperidinetricarboxylic acid, and r-2,t-3,c-5-piperidinetricarboxylic acid.     

Darstellung,spektroskopische Charakterisierung und Normalkoordinatenanalyse der bindungsisomeren Tetrachloroiodoselenocyanatoosmate(IV). Kristallstruktur von trans‐(PPh4)2[OsCl4I(NCSe)]

Preparation, Crystal Structure, and Normal Coordinate Analysis of Linkage Isomeric Pentachloroiodoselenocyanatoosmates(IV). Crystal Structure of trans‐(PPh₄)₂[OsCl₄I(NCSe)] By treatment of the solution of (n‐Bu₄N)₂[OsCl₅I] in dichloromethane with suspended Pb(SeCN)₂ the linkage isomers trans‐(n‐Bu₄N)₂[OsCl₄I(NCSe)] ( 1 ) and trans‐(n‐Bu₄N)₂[OsCl₄I(SeCN)] ( 2 ) are formed, which have been separated by ion exchange chromatography on diethylaminoethyl cellulose. The X‐Ray structure determination on a single crystal of trans‐(PPh₄)₂[OsCl₄I(NCSe)] (triclinic, space group P1¯, a = 10.8950(13), b = 11.076(2), c = 20.980(2)Å, α = 96.940(10), β = 98.747(9), γ = 104.419(11)°, Z = 2) reveals, that the nearly linear selenocyanate group in trans position to the iodine atom is coordinated with the Os‐N‐C angle of 171.1°. Based on the molecular parameters of the X‐ray determination ( 1 ) and estimated data ( 2 ) the IR and Raman spectra of both linkage isomers are assigned by normal coordinate analysis. The valence force constants are f_d(OsN) = 1.70 und f_d(OsSe) = 1.15 mdyn/Å.