Search results for "Cyclopentadiene"
showing 10 items of 49 documents
CCDC 684679: Experimental Crystal Structure Determination
2009
Related Article: H.Detert, D.Lenoir, H.Zipse|2009|Eur.J.Org.Chem.|2009|1181|doi:10.1002/ejoc.200801076
Pentafulvene durch Aminomethinylierung des Cyclopentadiens
1986
Aus der Dreikomponentenreaktion von Cyclopentadien (1) mit s-Triazin (2) und einem sekundaren Amin 4 gehen die cyclisch N,N-disubstituierten Pentafulven-6-amine 5 und die cyclisch N1,N1-disubstituierten N2-(6-Pentafulvenyl)formamidine 7 hervor. Unter den biologischen Eigenschaften der neuen Verbindungen ist besonders die anthelminthische Wirkung von 5d interessant. Pentafulvenes by Aminomethynylation of Cyclopentadiene The three component reaction comprising the interaction of cyclopentadiene (1) with s-triazine (2) and a secondary amine 4 leads to the cyclic N,N-disubstituted pentafulven-6-amines 5 and the cyclic N1,N1-disubstituted N2-(6-pentafulvenyl)formamidines 7. Among the biological …
The Preparation of Tetramethyl 1,1′,3,3′-Ruthenocenetetracarboxylate and Tetramethyl 1,1′,3,3′-Osmocenetetracarboxylate, and a Simplified Synthesis …
2018
Substituted metallocenes with more than two substituents have to be synthesized using doubly substituted cyclopentadiene rings in a reaction with a metal compound or by the introduction of additional functional groups to an already di-substituted metallocene. The direct formation of tetra-substituted metallocenes often suffers due to insufficient reactivity of the reagents or the resulting product mixtures, which are hard to separate. In this work, a protocol, which was successful in a tetra-substitution of ferrocene by a tetra-metalation followed by a reaction with carbon dioxide, is used to perform the tetra-substitution of ruthenocene and osmocene. In addition, a simplified protocol for …
Thermische Diels-Alder-Reaktionen mitN-(2-Alkenoyl)-(S)-prolinestern als chiralen Dienophilen in organischen und wäßrigen Reaktionsmedien
1990
Thermal Diels-Alder Reactions with N-(2-Alkenoyl)-(S)-proline Esters as Chiral Dienophiles Cyclopentadiene reacts with N-acryloyl-(S)-proline benzyl and allyl ester in toluene at 0°C to give the bicycloheptene-carboxylic acid amides with a stereoselection of (2S):(2R) = 81:19. In the reactions with the N,N′-fumaroylbis(proline esters) the cycloadducts are formed in high yields and with isomer ratios of up to 97:3. The absolute configuration of N,N′-〈(1R,2R,3R,4S)-bicyclo[2.2.1]hept-5-ene-2,3-diyldicarbonyl〉bis-[(S)-proline benzyl ester] (6 a) has been determined by an X-ray analysis. In the reactions of the acrylamides with cyclopentadiene and of the fumaramides with cyclopentadiene, isopre…
The domino reaction between 4,6-dinitrobenzofuroxan and cyclopentadiene. Insights on the nature of the molecular mechanism
2004
Abstract The molecular mechanism of the domino reaction between 4,6-dinitrobenzofuroxan, 1 , and cyclopentadiene, Cp, to give the adduct 11 is examined through density functional theory (DFT) calculations at B3LYP/6-31G* level. This domino reaction comprises two consecutive formally [4+2] cycloadditions. The first one is a two-center addition initialized by the nucleophilic attack of Cp to the more electrophilic center of 1 . The subsequent cyclization can take place along two competitive channels associated to the formation of a second C–C bond yielding the formally [2+4] cycloadduct 9 , or a C–O bond yielding the formally [4+2] cycloadduct 10 . The second cycloaddition is a stepwise proce…
Pyrazolium- and 1,2-Cyclopentadiene-Based Ligands as σ-Donors: a Theoretical Study of Electronic Structure and Bonding
2012
A high-level theoretical investigation of 1,2-cyclopentadiene (4) was performed using density functional theory and wave function methods. The results reveal that, in contrast to earlier assumptions, the ground state of this ephemeral “allene” is carbene-like with a small diradical component. Furthermore, the electronic structure and chemistry of 4 are found to parallel that of 1,2,4,6-cycloheptatetraene: both molecules possess a low-lying excited singlet state with a closed-shell carbenic structure, enabling rich coordination chemistry. Energy decomposition analyses conducted for currently unknown metal complexes of 4 as well as those involving stable carbenes based on the pyrazolium frame…
A PM3 study of the molecular mechanism for the cycloaddition between cyclopentadiene and protonated pyridine-imine derivatives
2001
Abstract The molecular mechanism of the cycloaddition reaction between cyclopentadiene (CP) and three pyridine-imine derivatives has been studied by means of PM3 semiempirical method. The role of the protonation, endo/exo and π-facial stereoselectivity are analyzed and discussed. In neutral conditions the cycloaddition between CP and the pyridine-imine takes place along a concerted mechanism. Protonation on both nitrogen atoms brings out that the reaction pathway takes with a very low barrier along a stepwise mechanism. PM3 results are capable to find the key factors governing this chemical reaction and to explain the experimental outcome.
Cyclopentadiene with two coordinating sites: 1,5-bis(diphenylphosphino) -2,3,4-trimethylcyclopenta-1,3-diene
1997
Abstract The possibility of obtaining the new bidentate 1,2-diphenylphosphinocyclopentadienyl ligand has been studied. 1,5-bis(diphenylphosphino)-2,3,4-trimethylcyclopenta-1,3-diene can be formed from butanone and chlorodiphenylphosphine in eight steps. The results of chemical and spectroscopic studies reveal that a 1.5-sigmatropic migration of the diphenylphosphino group takes place: the 1,2-diphenylphosphino-substituted species are converted into 1.3 species.
Complementarity of reaction force and electron localization function analyses of asynchronicity in bond formation in diels-alder reactions
2014
We have computationally compared three Diels-Alder cycloadditions involving cyclopentadiene and substituted ethylenes; one of the reactions is synchronous, while the others are slightly or highly asynchronous. Synchronicity and weak asynchronicity are characterized by the reaction force constant κ(ξ) having just a single minimum in the transition region along the intrinsic reaction coordinate ξ, while for high asynchronicity κ(ξ) has a negative maximum with minima on both sides. The electron localization function (ELF) shows that the features of κ(ξ) can be directly related to the formation of the new C-C bonds between the diene and the dienophile. There is thus a striking complementarity b…
Cyclopentadienyl derivatives of octahedral carbonylcarbide hexaruthenium clusters: synthesis, NMR, IR and X-ray characterization
1996
Abstract The reaction of hexanuclear carbonylcarbide cluster Ru6C(CO)17 (1) with pentamethylcyclopentadiene by reflux in heptane leads to a new chelate cluster Ru6C(μ-η1-η5-CH2C5Me4)(CO)14 (2). The compound 2 contains a CH2 group α-bonded to one of the Ru atoms in the Ru6 cluster and a C5Me4-ligand η5-coordinated by the adjacent Ru atom of the Ru6 cluster. Reflux of 1 in hexane with two molecular equivalents of nickelocene, Ni(C5H5)2 NiCp2, used as a source of cyclopentadiene yields the Ru6C(CO)12Cp2 (3) cluster. The compounds 2 and 3 have been characterized by NMR and IR spectroscopy and their crystal structures determined by X-ray diffraction studies.