Search results for "Reaction"
showing 10 items of 6134 documents
Mononuclear heterocyclic rearrangement. Part 6 . Studies on base catalysis of the rearrangement of the (Z)-p-nitrophenylhydrazone of 3-benzoyl-5-phen…
1981
A combined experimental and theoretical study of the alkylation of 3,5-dithioxo-[1,2,4]triazepines
2008
The chemo- and regioselective alkylation reactions of 3,5-dithioxo[1,2,4]triazepine 1 in a basic medium with α,ω-dibromoalkanes 2a–c, Br(CH2)nBr (n = 1–3), are studied experimentally and theoretically. These alkylations, which occur at the thioxo sulfur atom in position 5, afford mainly 5-bromomethylthio-2,7-dimethyl- 2,3-dihydro- 4H[1,2,4]triazepin-3-one 3 for n = 1, 6,8-dimethyl-5-thioxo-2,3,4,5-tetrahydro-6H[1,3]thiazolo[4,5-d][1,2,4]triazepine 4 for n = 2 and 7,9-dimethyl-6-thioxo-2,3,4,5,6,7-hexahydro[1,3]thiazino [4,5-d][1,2,4]triazepine 5 for n = 3. Theoretical calculations have been carried out at the B3LYP/6-31G* and B3LYP(benzene)/6-311+G*//B3LYP/6-31G* levels, in order to rationa…
1,2,4-Oxadiazole rearrangements involving an NNC side-chain sequence.
2009
The thermal rearrangement of N-1,2,4-oxadiazol-3-yl-hydrazones into 1,2,4-triazole derivatives is reported. This represents the first example of a three-atom side-chain rearrangement involving an NNC sequence linked at the C(3) of the oxadiazole. The reactions carried out under solvent-free conditions produced good to high yields of the final products.
E-Ring extended estrone derivatives: introduction of 2-phenylcyclopentenone to the estrone D-ring via an intermolecular Pauson–Khand reaction
2006
Abstract An expedient synthetic route to E-ring extended estrone derivatives is reported. Estrone-derived cyclopentenones were accessed by an intermolecular Pauson–Khand (PK) cycloaddition. It was found that electron donating and withdrawing substituents in the arylalkyne increased and decreased the yields of PK products, respectively. The stereochemistry of the products was elucidated by X-ray and NMR studies.
Synthese von methyl- und methylenosubstituierten p-Oligophenylenen durch cokondensierende ULLMANN-Reaktion. 12. Mitt.
1963
Es wird ein Syntheseverfahren fur p-Oligophenylene beschrieben, das eine Variante der ULLMANNschen Biarylverknupfungsreaktion darstellt. Dabei wird eine bifunktionelle Jodverbindung mit einem groseren Uberschus an einer monofunktionellen Komponente umgesetzt. Dieses als cokondensierende ULLMANN-Reaktion bezeichnete Syntheseprinzip, das Ausbeuten von 40–50% d. Th. ergibt, wird eingehend erlautert und die Leistungsfahigkeit an zahlreichen Beispielen belegt. Neben einer Reihe von methylsubstituierten p-Oligophenylenen, welche Derivate vom p-Terphenyl bis zum p-Septiphenyl einschliest, werden auch Oligophenylene mit endstandigem oder mittelstandigem Fluorenrest als Strukturelement hergestellt. …
ChemInform Abstract: Influence of Reactant Polarity on the Course of the Inverse-Electron-Demand Diels-Alder Reaction. A DFT Study of Regio- and Ster…
2010
The molecular mechanisms for the inverse-electron-demand Diels−Alder reactions between nitroethene and three substituted ethenes (propene, methyl vinyl ether, and dimethylvinylamine) to give the corresponding nitroso cycloadducts have been characterized with density functional theory methods using the B3LYP/6-31G* calculational level. On the basis of stability arguments and molecular orbital analysis relative rates, regioselectivity, and stereoselectivity, the presence of Lewis acid catalyst modeled by the BH3 system and the inclusion of solvent effects as a function of the nature of substituent in the dienophile fragment are analyzed and discussed. The ortho attack mode presents transition…
Synthesis of Chlorinated Biphenyls by Suzuki Cross-Coupling Using Diamine or Diimine-Palladium Complexes
2008
Several novel diimines (Salen-type ligands) 2a–2i and their reduced diamine counterparts 3b,3d–3g and 3i form complexes 4a–4i, 5b,5d–5g, and 5i with PdCl2 in DMF or methanol. Using 1 mol-% of the isolated complexes 4e and 5f many polychlorinated biphenyls (PCBs) can be prepared in moderate to excellent yields according to the Suzuki crosscoupling protocol with contact to air. Several 4-acetylbiphen
Syntheses of polyfunctionalized resveratrol derivatives using Wittig and Heck protocols
2012
Improved protocols for Wittig reaction and palladium-catalyzed Heck coupling give expedient access to a series of unprecedented polyfunctionalized artificial-resveratrol derivatives. In the modified Wittig protocol, trimethylsilyl was used as a highly valuable protective group of the phenolic functions of starting aromatic materials. A clean O-alkylation of hydroxylated stilbenes with ethylene carbonate was also conducted. Thus, Wittig reaction followed by hydroxyethylation take place one-pot with only carbon dioxide as waste. Additionally, a palladium-catalyzed Heck coupling strategy was developed by using ferrocenyl phosphane ligands, and multi-functionalized hydroxylated stilbenes were o…
ChemInform Abstract: First Synthesis of Chiral 3-Vinylindoles as 4π-Components for Diels- Alder Reactions.
2010
The first syntheses of chiral 3- and 2-vinylindoles bearing sulfoxide or (-)-menthyloxy functional groups at the β-vinyl positions by way of procedures based on the Horner-Wadsworth-Emmons and Wittig reactions, respectively, are described. Some Diels-Alder reactions demonstrating the 4π-reactivity of these compounds are reported.
ChemInform Abstract: A New Versatile Synthesis of N,N′,N′′,N′′′-Tetra(2-carboxyethyl)- and N,N′,N′′,N′′′-Tetra(3-aminopropyl)-tetraazacycloalkanes by…
2010
Abstract A smooth and convenient one step synthesis of N,N′,N″,N″′-tetra-(2-carboxyethyl)-tetraazacycloalkanes is reported. These compounds are synthesized by Michael addition of tetraazacycloalkanes to acrylic acid. The same Michael addition of tetraazacycloalkanes to an excess of acrylonitrile also leads to the corresponding tetracyanoethylated derivatives. The reduction of such tetracyanoethylated compounds is a new way of preparation for the corresponding primary amines.