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A pseudo three-component reaction of 2-imidazolines with electron-deficient alkynes furnishes 1,2,2,3-tetrasubstituted imidazolidines containing N-vinylpropargylamine moiety. Heating imidazolidines in aerobic conditions in butyl acetate solution leads to highly functionalized pyrroles through aza-Claisen rearrangement/nucleophilic addition/oxidation/acylation. [ABSTRACT FROM AUTHOR]

Transformations of 2-methyl-1-R-1-phenylethynyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines under the action of electron-deficient alkynes in aprotic and protic solvents were studied. 1-Phenyl-1-phenylethynyl substituted pyrrolopyrazine did not react with alkynes or gave complex reaction mixtures. 1-Alkyl substituted 1-phenylethynyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines in protic solvents underwent expansion to 8-alkylidene-6-phenyl-1,2,3,8-tetrahydropyrrolo[1,2-d][1,4]diazecines. [ABSTRACT FROM AUTHOR]

Alkyne insertion into four-membered carbocyclic rings was achieved through rhodium(I)-catalyzed C-C bond cleavage. The reaction of (2-pyridylmethylene)cyclobutenes proceeded via C-C oxidative addition, and that of cyclobutenols involved β-carbon elimination. In both the cases, multiply substituted benzenes were obtained through the aromatization of the initially formed 1,4-cyclohexadienes. [ABSTRACT FROM AUTHOR]

An efficient ionic liquid catalytic system for hydration of haloalkynes to α-haloketones has been reported. The environmental-friendly system could be easily recycled and reused without any loss of catalytic. α-Haloketones could be got in good to excellent yields with a wide scope of substrates. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of the mesoporous silica-supported gold (Au@mSiO2) nanoparticles compatibilized with the outer shelled superhydrophobic fluorous (F) "tails" was described. The concept of fluorous biphasic separation was applied in the recycling of the synthesized fluorous material during hydroamination reactions of various alkynes. In the presence of perfluoromethylcyclohexane and heptane as a biphasic liquid system, the F-Au@mSiO2 was found to be a highly active catalyst for hydroamination of various alkynes with anilines, and a near quantitative yield for an imine product and produced a relatively minimal formation of a corresponding hydrolyzed ketone by-product. If perfluoromethylcyclohexane and heptane was used as a biphasic solvent, hydroamination at a lower reaction temperature can also be realized leading to an improved recyclability and conversion. [ABSTRACT FROM AUTHOR]

The decision on the fate of the reaction (branching of the path) is sometimes not only taken at the last conical intersection, but the Franck-Condon region can also contribute. Consideration of simple properties such as the slopes of the potential surfaces can explain effects such as the principle of least motion or the torquoselectivity without invoking ad-hoc electronic effects. The lack of stereospecificity of cyclobutene ring opening and the wavelength dependence of photochemical reactions of alkylated olefins and cyclobutenes can similarly be explained, if one assumes in addition that the momentum is conserved over a certain time. [ABSTRACT FROM AUTHOR]

In recent years the catalytic aspects of the organometallic complexes of d[sup 0]/f[sup n]-block have attracted major attention and have been in particular the focus of numerous investigations for the functionalization of unsaturated organic molecules. Metal-mediated oligomerization of terminal alkynes is of considerable current interest because it can lead to a variety of organic enynes and oligoacetylene products that are useful synthetic precursors for the synthesis of natural products and also for organic conducting polymers. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]