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showing 10 items of 1921 documents
Controlled UV-C light-induced fusion of thiol-passivated gold nanoparticles.
2011
Thiol-passivated gold nanoparticles (AuNPs) of a relatively small size, either decorated with chromophoric groups, such as a phthalimide (Au@PH) and benzophenone (Au@BP), or capped with octadecanethiol (Au@ODCN) have been synthesized and characterized by NMR and UV-vis spectroscopy as well as transmission electron microscopy (TEM). These NPs were irradiated in chloroform at different UV-wavelengths using either a nanosecond laser (266 and 355 nm, ca. 12 mJ/pulse, 10 ns pulse) or conventional lamps (300 nmλ400 nm and ca. 240 nmλ280 nm) and the new AuNPs were characterized by X-ray and UV-vis spectroscopy, as well as by TEM. Laser irradiation at 355 nm led to NP aggregation and precipitation,…
Dienediolates of unsaturated carboxylic acids in synthesis. Synthesis of cyclohexenones and polycyclic ketones by tandem Michael-Dieckmann decarboxyl…
1994
Abstract Substituted 2-cyclohexenones 4 to 7 and hexaxydronaphthalenones and hexahydroindenones 13 to 18 are prepared by tandem Michael-Dieckmann addition of lithium dienediolates of acyclic and alicyclic unsaturated carboxylic acids to the lithium salts of the same or other unsaturated carboxylic acids.
Asymmetric Synthesis of Spirobenzazepinones with Atroposelectivity and Spiro-1,2-Diazepinones by NHC-Catalyzed [3+4] Annulation Reactions
2016
A strategy for the NHC-catalyzed asymmetric synthesis of spirobenzazepinones, spiro-1,2-diazepinones, and spiro-1,2-oxazepinones has been developed via [3+4]-cycloaddition reactions of isatin-derived enals (3C component) with in-situ-generated aza-o-quinone methides, azoalkenes, and nitrosoalkenes (4atom components). The [3+4] annulation strategy leads to the seven-membered target spiro heterocycles bearing an oxindole moiety in high yields and excellent enantioselectivities with a wide variety of substrates. Notably, the benzazepinone synthesis is atroposelective and an all-carbon spiro stereocenter is generated.
Cover Picture: Palladium-Catalyzed Arylation of Linear and Cyclic Polyamines (Eur. J. Org. Chem. 2/2005)
2005
The cover picture shows the model structures of four compounds among the hundred of arylated linear and cyclic polyamines prepared by palladium-catalyzed coupling of mono- and dihalogenoarenes with various aliphatic or aromatic polyamines. The reaction is strongly dependent on the nature and the concentration of the catalytic system, as well as the nature of the base. The competitive reaction between primary and secondary amines and the monoamination of dihalobenzenes have also been detailed in the article by R. Guilard et al. on p. 261 ff. In the following article by the same authors on p. 281 ff, the method has been applied to the synthesis of numerous nitrogen- and oxygen-containing macr…
Static measurements of refractive index increments at 633 nm with a modified refractive index detector
1985
A R 401 Waters Assoc. differential refractometer has been modified to obtain the variation of refractive index increments, dn/dc, of polymer solutions at 633 nm. The introduced modifications were in the sample injection system and in the light source. The performance of the modified refractometer both with aqueous and organic solutions is analyzed. In order to localize a conformational transition in lysozyme, the dependence of dn/dc on temperature for lysozyme solutions in phosphate buffer is studied. Similarly, (dn/dc)k values for the ternary n-alkane/butanone/poly(dimethyl siloxane) systems over the whole composition range of the binary solvent mixtures are evaluated.
Wirkung der Insektizide Allethrin, Lindan und Jacutin-Fogetten-Sublimat auf den photosynthetischen Elektronentransport
1977
Summary During our studies of Hill-reactions of isolated chloroplasts we observed an inhibition of electron transport after an application of the smoke of «Jacutine-Fogetten» in the plant growth chamber. Therefore we tested the influence of the insecticides Lindane (Gammexan), the sublimate formed by the fumigation of «Jacutin Fogetten», and of Allethrin on the photosynthetic electron transport reactions of PS II and PS I. 39 μ M Lindane inhibits the basal, coupled and uncoupled electron transport to ferricyanide of broken chloroplasts isolated from leaves of Pisum sativum up to 35%. A higher inhibitory effect with higher concentrations is limited by the low water solubility of Lindane. On …
FORMATION OF ALIPHATIC CARBOXYLIC ACIDS DURING ALKALINE PULPING OF MULI BAMBOO
2002
ABSTRACT A study on the formation of aliphatic carboxylic acids, i.e., formic and acetic acids and various hydroxy monocarboxylic and dicarboxylic acids, during soda-AQ, kraft, and kraft-AQ pulping of muli bamboo (Melocanna baccifera) was carried out. Detailed gas chromatographic analyses revealed that the most abundant hydroxy carboxylic acids were 2-hydroxybutanoic, lactic, glucoisosaccharinic, glycolic, xyloisosaccharinic, 3,4-dideoxypentonic, and 3-deoxypentonic acids. The presence of AQ depressed the formation of 2-hydroxybutanoic, xyloisosaccharinic, and glucoisosaccharinic acids, and accelerated the formation of glycolic and 3-deoxypentonic acids as well as 3-deoxytetronic acid but h…
ChemInform Abstract: 1-Alkyl- and Azeto[1,2-a][1,5]benzodiazepine Derivatives in the Reaction of o-Phenylenediamine with 3-(Dimethylamino)propiopheno…
2001
The reaction of o-phenylenediamine (4) with one, two or three equivalents of p-substituted 3-dimethylaminopropiophenone hydrochlorides 5a−e was studied. 4-Aryl-2,3-dihydro-1H-1,5-benzodiazepine derivatives 6a−e were obtained in good yields, along with the 1:2-adducts 7c−e and the unexpected 1:3-adducts rac-8c−e. The type of adduct formed is determined by the molar ratio of the reactants 4 and 5 and by the nature of the substituent in the para position of the propiophenone 5.
A non-catalyzed ring-opening aminolysis reaction of sesquiterpene lactones
1994
Abstract Santonin (1) and other sesquiterpene lactones (6–10) react cleanly with pyrrolidine at room temperature to afford γ-hydroxyalkylamides, which by elimination with mesyl chloride in pyridine-benzene at 80°C give unsaturated alkylamides.
Synthesis of two natural 8-oxo-β-cyperone derivatives from (−)-santonin.
1993
Abstract This paper reports on the chemical transformations of (−)-santonin into (+)-8-oxo-β-cyperone and (+)-12-hydroxy-8-oxo-β-cyperone involving 8-oxo group introduction and elaboration of the side chain.