Die Bestimmung von o-Nitrotoluol in Nitrocellulosepulver mittels des Eintauchrefraktometers

Ohne Zusammenfassung     

Synthesis of 6-amino-1,2,3-triazolo[4,5-c] pyridin-4(5H)one (8-aza-3-deazaguanine) and 6-amino-1-(β-D-ribofuranosyl)-1,2,3-triazolo[4,5-c] pyridin-4(5H)one (8-Aza-3-deazaguanosine) via novel ring closure procedures

The total synthesis of 6-amino-1,2,3-triazolo[4,5-c]pyridin-4(5H)one (8-aza-3-deazaguanine, 3 ) and 6-amino-1-(β-D-ribofuranosyl)-1,2,3-triazolo[4,5-c]pyridin-4(5H)one (8-aza-3-deazaguano-sine, 22 ) has been described for the first time by a novel base-catalyzed ring closure of 4(5)-cyanomethyl-1,2,3-triazole-5(4)carboxamide (14) and methyl 5-cyanomethyl-1-(2,3,5-tri-O-ben-zoyl-β-D-ribofuranosyl)-1,2,3-triazole-4-carboxylate (17) , respectively. Under the catalysis of DBU, 2,4-dinitrophenylhydrazone of dimethyl 1,3-acetonedicarboxylate (7) was converted to methyl 5-methoxycarbonylmethyl-1-(2,4-dinitroanilino)-1,2,3-triazole-4-carboxylate (12) via dimethyl 2-diazo-3-iminoglutarate (8) . Catalytic reduction of 12 gave methyl 4(5)methoxycar-bonylmethyl-1,2,3-triazole-5(4)carboxylate (11) from which methyl 4(5)carbamoylmethyl-1,2,3-triazole-5(4)carboxylate (10) was obtained by ammonolysis. Dehydration of 10 provided methyl 4(5)cyanomethyl-1,2,3-triazole-5(4)carboxylate (13) which on amination gave 14 . The 1,2,3-triazole nucleosides 17, 18 and 19 were obtained from the stannic chloride-catalyzed condensation of the trimethylsilyl 13 and a fully acylated β-D-ribofuranose. The yield and ratio of the ribofuranosyl derivatives of 13 markedly depends on the ratio of stannic chloride used. The structures of the nucleosides 22 and 23 were established by a combination of NOE, ¹H-nmr and ¹³C-nmr spectroscopy.     

Structural properties of charged diblock copolymer solutions

Aqueous micellar solutions of ionic/neutral block copolymers have been studied by light scattering, small angle neutron scattering and small angle X-ray scattering. We made use of a polymer comprised of a short hydrophobic block (polyethylene-propylene) PEP and of a long polyelectrolytic block (polystyrene-sulfonate) PSSNa which has been shown previously to micellize in water. The apparent polydispersity of these micelles is studied in detail, showing the existence of a few large aggregates coexisting with the population of micelles. Solutions of micelles are found to order above some threshold in polymer concentration. The order is liquid-like, as demonstrated by the evolution with concentration of the peak observed in the structure factor (), and the degree of order is found to be identical over a large range of concentrations (up to 20 wt%). Consistent values of the aggregation number of the micelles are found by independent methods. The effect of salt addition on the order is found to be weak. Received: 19 June 1997 / Received in final form: 4 September 1997 / Accepted: 9 October 1997     

Atom transfer cyclization catalyzed by InCl3 via halogen activation

[reaction: see text] Indium trichloride was found to be an efficient catalyst for the cyclization of allylic halides and alkynes with atom transfer in methylene chloride. Mechanistic evidence supports a cationic reaction pathway with Lewis acid activation of the allylic halogen. Concomitant nucleophilic attack by the alkyne and trapping with halide led to atom transfer cyclization products. Depending on alkyne substitution, a bromine atom was transferred from the substrate or a chlorine atom was transferred from the solvent.     

Modification of galvannealed steel through aluminum addition

Aluminum is believed to modify and to some extent control the coating characteristics of commercially produced galvanneal sheet steel. These include mechanical, chemical, and aesthetic properties. Whereas the aluminum added to the molten zinc bath is known to form intermetallics before the steel is annealed, our research is primarily concerned with the effect aluminum has on suppression or enhancement of the particular iron--zinc alloy phases in the coating during galvannealing. The microstructure of four commercially important iron--zinc intermetallic phases containing varying aluminum content between 0--1.5 weight percent has been studied. It is also believed that an iron--aluminum alloy, known as the inhibition layer, forms on the steel surface following hot dipping and prior to annealing. Transmission and scattering Mössbauer spectroscopy as well as X-ray diffraction have been used to identify iron--zinc and iron--aluminum alloys present in the coatings. Discussion will be presented on the effect aluminum has on phase suppression for Fe--Zn alloys prepared in commercially produced galvanneal.     

Use of xenon as a mobile phase for on–line capillary supercritical fluid chromatography–fourier transform infrared spectrometry

Xenon is investigated as a mobile phase for on-line capillary supercritical fluid chromatography-Fourier transform infrared spectrometry (SFC-FTIR). Polycyclic aromatic hydrocarbons, aromatic isocyanates, and epoxy acrylate oligomers are analyzed as examples to show that xenon has similar selectivities and solvating powe to CO₂. Its optical transparency makes it ideal for IR detection. A stop flow system is constructed to increase the sensitivity of spectra measured from compounds which are weak IR absorbers.     

Microwave-assisted, regioselective, Petasis olefination of unsymmetrical oxalates. Formation of pyruvate-based enol ethers and enamines

The Petasis olefination of unsymmetrical oxalates and oxalate monoesters/monoamides (tert-BuO₂CC(O)X, where X = OR, NR₂) is highly regioselective and provides pyruvate-based enol ether and enamine derivatives. The olefination step occurs under conventional thermal conditions, but is dramatically improved--shorter reaction times and higher yields--when promoted by microwave irradiation.     

The tautomerism of heteroaromatic compounds with 5-membered rings—XI 4-Hydroxyisoxazoles-4-isoxazolinones

Four 4-hydroxyisoxazoles together with model compounds have been investigated by UV, IR and NMR spectroscopy and by pK_a measurements, 4-Hydroxyisoxazoles exist predominantly in the hydroxy-form in a wide range of media.