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showing 10 items of 1967 documents
ChemInform Abstract: Preparation of Dithiacycloalkynes by Cyclization Reactions Applying the Cesium Effect.
2010
Abstract The strained dithiacycloalkynes 3a,b and the larger heterocyclic alkynes 3c and 4 are obtained by cesium assisted cyclization reactions of the dithiols 1a–c and 1,4-dibromo-2-butyne (2). The reactivity of 3a–c was studied in cycloaddition and complexation reactions generating the adducts 5a,b and 6 and the silver and cobalt complexes 7 and 8.
ChemInform Abstract: Cycloaddition Reactions of Benzothiete with Azomethines.
1987
Obtention de diaryl-2,3 dihydro-3,4 benzothiazines-1,3 (70%) via la cycloaddition de la thiobenzoquinone methode-1,2 (obtenue par scission thermique du benzothiete) et d'arylimines de benzaldehydes. Obtention egalement de 10% du dimere (dibenzo [b, f] dithiocinne-1,5)
Synthesis of 5-substituted 2,3-dihydrobenzofurans in a one-pot oxidation/cyclization reaction
2011
Variously substituted 2,3-dihydrobenzofurans have been synthesized according to a sequential one-pot oxidation/cyclization procedure between para-aminophenol derivatives and an azadiene. Variously substituted 2,3-dihydrobenzofurans have been synthesized according to a sequential one-pot oxidation/cyclization procedure between para-aminophenol derivatives and an azadiene. © 2011 Elsevier Ltd. All rights reserved.
N-benzoylindole-2,3-quinodimethane: Diels-Alder reactivity and synthetic applications for [b]annellated indoles
1991
Abstract The Diels-Alder reactivity of in situ generated N -benzoylindole-2,3-quinodimethane has been expanded considerably to include reactions with carbon- and hetero-dienophiles which furnish a variety of [ b ]annellated indoles as well as functionalized and annellated carbazoles. The frontier molecular orbital theory was found to be a useful model for the prediction of the experimental results under consideration of reactivity aspects.
5-Alkenyl-1,2,3-thiadiazole
1986
Es wird die Herstellung der Titelverbindungen 5 durch Bromierung-Dehydrobromierung entsprechender 5-Alkyl-1,2,3-thiadiazole 3, ihre spektroskopische Charakterisierung und ihre Umsetzung mit 4-Phenyl-4H-1,2,4-triazol-3,5-dion (6) zu 7, 8 beschrieben. 5-Alkenyl-1,2,3-thiadiazoles A method of preparation for the title compounds 5, by bromination-dehydrobromination of the corresponding 5-alkyl-1,2,3-thiadiazoles 3, their spectroscopical characterization, and the reaction of 5 with 4-phenyl-4H-1,2,4-triazole-3,5-dione (6) with formation of 7, 8 is described.
A density functional theory study for the Diels–Alder reaction between N-acyl-1-aza-1,3-butadienes and vinylamines. Lewis acid catalyst and solvent e…
2002
Abstract The molecular mechanism for the Diels–Alder reaction of N-acyl-1-aza-1,3-butadiene with dimethylvinylamine has been studied using density functional theory methods. This cycloaddition is the nucleophilic attack of the vinylamine to the conjugate position of the unsaturated acyl imine with concomitant ring-closure. The presence of a Lewis acid catalyst coordinated to the acyl oxygen atom decreases markedly the activation energy associated to the nucleophilic attack. This results from an increasing of the electrophilicity of the 1-aza-1,3-butadiene that shift the mechanism from a highly asynchronous concerted process to a polar stepwise one.
Formation and Reactivity of 2-Styryl-1,4-benzoquinones
2001
Density functional theory study of the Lewis acid-catalyzed Diels-Alder reaction of nitroalkenes with vinyl ethers using aluminum derivatives
2002
The inverse electron demand Diels–Alder reaction of nitroalkenes with vinyl ethers catalyzed by Lewis acids based on aluminum metal, AlMe3, Al(OMe)3 and AlCl3 was studied using density functional theory methods. A continuum model was selected to represent the effects of dichloromethane used as solvent. For this cycloaddition reaction two reactive channels corresponding to the endo and exo approach modes of the vinyl ether to the Lewis acid-coordinated nitroalkene were studied. Coordination of the aluminum metal to an oxygen atom of the nitroalkene increases the electrophilicity of the heterodiene, decreasing the activation energy of the cycloaddition. The substitution effect on the aluminum…