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排序方式: 共有333条查询结果,搜索用时 31 毫秒
1.
Georg Süss-Fink Ulf Bodensieck Lisa Hoferkamp Gerd Rheinwald Helen Stoeckli-Evans 《Journal of Cluster Science》1992,3(4):469-478
The reaction of trirutheniumdodecacarbonyl with various thioureas was found to give, depending upon the substituents and the reaction conditions, a large variety of tri-, tetra-, penta-, and hexanuclear ruthenium clusters. The ligand systems observed in the products are derived from the thioureas employed; the fragmentation of the thiourea molecules involve N-H, C-S, C-H, and C-N activation processes. 相似文献
2.
Cyclic and acyclic β-bromovinyl aldehydes are cyclized with an array of arylhydrazines in toluene at 125 °C in the presence of a palladium catalyst and a phosphorus chelating ligand together with NaOtBu to give 1-aryl-1H-pyrazoles in moderate to good yields. 相似文献
3.
Yuhua Zhang 《Tetrahedron letters》2004,45(41):7581-7584
Under microwave conditions, tetrahydrofuran (THF), tetrahydropyran and 1,4-dioxane are added directly onto alkynes and generated various vinyl cycloethers. 相似文献
4.
The electrophilic α-alkylation of ketones with alcohols was accomplished by a [Ru(DMSO)4]Cl2 catalyzed process, water being the only wasted material. The reaction can be successfully governed to produce either the expected ketones or their related alcohols only by changing the reaction conditions. When 2-aminobenzyl alcohol was used, a cyclization process took place to yield 2,3-disubstituted quinolines. 相似文献
5.
Friedrich W. Vierhapper 《Monatshefte für Chemie / Chemical Monthly》1980,111(2):551-554
Conformations of six title compounds were determined by13C-NMR spectroscopy. Equilibration of the 2-methyl-compounds gives as main products the derivatives of the amines least abundant in the product mixture of the catalytic hydrogenation.
Konformation und Base-katalysierte Äquilibrierungen von N-Nitroso-decahydrochinolinen und N-Nitroso-2-methyl-decakydrochinolinen (Kurze Mitt.)
Zusammenfassung Die Konformationen der sechs Titelverbindungen wurden mittels13C-NMR Spektroskopie bestimmt. Äquilibrierung der 2-Methyl-verbindungen ergab als Hauptprodukte die Derivate der bei katalytischer Hydrierung in geringster Menge entstandenen Amine.相似文献
6.
Klaus Rakus Sergej P. Verevkin Hans-Dieter Beckhaus Christoph Rüchardt 《欧洲无机化学杂志》1994,127(11):2225-2234
The thermolysis reactions of the tricyanomethyl compounds 10a-c were studied in solution. 2,2-Dicyano-3-methyl-3-phenylbutyronitrile ( 10a ) and 2,2-dicyano-3-methyl-3-(4-nitrophenyl)butyronitrile ( 10b ) decomposed heterolytically into carbenium ions and (CN)3C− anions, while 9-methyl-9-(tricyanomethyl)fluorene ( 10c ) underwent about 11% homolytic C-C bond cleavage into 9-methyl-9-fluorenyl- and tricyanomethyl radicals. The rates of the homolysis were determined by a radical scavenger procedure under conditions of pseudozero order kinetics. From the temperature effect on the rate constants the activation parameters were determined [ΔH ( 10c ) = 155· 2 kJ mol−1, ΔS ( 10c ) = 58· 5 J mol−1 K−1]. Standard enthalpies of formation ΔH (g) were determined for 2,2-dicyanopropionitrile ( 2 ) (422.45 kJ mol−1), 2,2-dicyanohexanenitrile ( 3 ) (349.74 kJ mol−1), 2,2-dicyano-3-phenylpropionitrile ( 4 ) (540.75 kJ mol−1), 2-butyl-2-methylhexanentrile ( 5 ) (-133.20 kJ mol−1), 2,2-dimethylpentanenitrile ( 6 ) (-45.78 kJ mol−1), and 2-methylbutyronitrile ( 7 ) (2.44 kJ mol−1) from the enthalpies of combustion and enthalpies of sublimation/vaporization. From these data and known Δ (g) values for alkanenitriles and -dinitriles, thermochemical increments for ΔH (g) were derived for alkyl groups with one, two, or three cyano groups attached. The comparison of these increments with those of alkanes reveals a strong geminal destabilization, which is interpreted by dipolar repulsions between the cyano groups. - From ΔH (g) of 10c and ΔH of its homolytic decomposition the radical stabilization enthalpy for the tricyanomethyl radical 1 RSE ( 1 ) = -18 kJ mol−1 was determined. Thus, 1 is destabilized, in comparison with the RSEs of tertiary α-cyanalkyl (23 kJ mol−1) and α,α-dicyanoalkyl (27 kJ mol−1) radicals, which were recalculated from bond homolysis measurements[4] and the new thermochemical data. This change of RSE on increasing the number of α-cyano groups is discussed as the result of the additive contributions by resonance stabilization and increasing destabilization by dipolar repulsion. The amount of the dipolar energies was estimated by molecular mechanics (MM2). 相似文献
7.
Reaction of 2,3,7,8,12,13,17,18-octaethylporphyrin with LiR reagents containing functional groups readily yields meso substituted derivatives suitable for further transformations with residues such as -p-C6H5Br, -p-C6H5-CCH, -p-C6H5-NH2 or -(CH2)3-CHCH2. Similar reactions of tetrabenzoporphyrin with alkyllithium reagents afforded the first entry into meso mono- and dialkylsubstituted tetrabenzoporphyrins while reaction of bicyclo[2.2.2]oct-type masked isoindole precursors with LiR followed by in situ retro-Diels-Alder reaction also afforded the 5-phenyl and 5,10-diphenyltetrabenzoporphyrins in high purity. 相似文献
8.
Shin Kamijo 《Tetrahedron letters》2006,47(32):5629-5632
Cyclic vinylogous triflate hemiacetals can serve as ‘synthetic equivalents’ for alkynyl aldehydes: treatment of a vinylogous triflate hemiacetal with excess amounts of Grignard reagents produces acyclic alkynyl alcohols in good to high yields. This transformation likely involves the Grob-type C-C bond cleaving fragmentation to form the alkynyl aldehyde in situ. Subsequent nucleophilic attack of the Grignard reagent furnishes secondary alkynols. Vinylogous triflate hemiacetals are easily prepared by DIBALH reduction of vinylogous acyl triflates, which are derived from cyclic 1,3-diketones. 相似文献
9.
Guan-Sheng JiaoAurore Loudet Hong Boon LeeStanislav Kalinin Lennart B.-Å JohanssonKevin Burgess 《Tetrahedron》2003,59(17):3109-3116
The purpose of this project was to prepare fluorescent dyes that could absorb energy at relatively short wavelengths, and fluoresce in the near-IR region. To achieve this, copper- and palladium-mediated C-N couplings were used to prepare the ‘cassettes’, i.e the carbazole derivative 3b and the carbazole-, phenothiazine-, and phenoazine-squaraines 4b-d. These compounds have carbazole, phenothiazine, and phenoazine donor-components that absorb around about 300-320 nm, and squaraine acceptor-parts that fluoresce in the range 650-700 nm. The efficiencies of energy transfer from the donor to the acceptor, and the overall quantum yields of the cassettes were determined. 相似文献
10.